Pa20292 Flashcards
0
Q
What activates cytotoxic T cells ?
A
Antigen presenting cells of class I MHC
Usually present viral fragments
Can also be stimulated by T helper Th1 cells
1
Q
Why are IgG antibodies so important?
A
Most abundant AB type in the circulation For secondary immune responses Microbes coated in IgG - opsonisation and complement activation AB dependent cell mediated cytotoxicity IgG provide Foetus with humoral immunity
2
Q
What shapes do each of the different classes of antibodies have? Ie monomer, dimer….
A
Monomers= IgE IgG Dimers = IgA Pentamers= IgM
3
Q
The lectin complement cascade pathway involves…..
A
Mannose receptor binding to lectin and cleaving C4
4
Q
What receptors (ABs) do B cells express once matured but before class switching?
A
IgM and IgD receptors
Remember; class switching and somatic hypermutations improve antibody affinity and function
5
Q
How are NKcs activated ?
A
IL-12 from macrophages
Activates NKCs, they secrete IFNy
IFNy Feeds back and activates macrophage
(positive feedback loop)
6
Q
Some features of neutrophils?
A
Granulocytes Lysosomes inside Large multi lobed nucleus Lot of organelles Contain antmicrobial enzymes phagocytose
7
Q
Do therapeutic antibodies tend to be polyclonal or monoclonal?
A
Monoclonal
Act against one particular epitope of an antigen
Activation of a single B cell= monoclonal response
8
Q
Who were vaccinations discovered by and when?
A
By EDWARD JENNER
IN 1976
9
Q
What cells is MHC protein present on?
A
Every cell apart from RBC’s
10
Q
What type of immunity do B cell produce?
A
Humoral immunity
Means antibody mediated immunity
11
Q
Why do antibodies remain specific to a certain antigen for the rest of its life?
A
Because B cells undergo irreversible gene recombination to make it specific to a particular antigen, it can’t change after this recombination as its irreversible.
12
Q
What is inhibition of development of Th1 or Th2 cells by cytokine IL-4 and IL-12 known as?
A
Reciprocal inhibition
13
Q
When activated, B cells swell in size. We call them _____
A
Plasma cells
Produces large numbers of antibodies
14
Q
What do dendritic, macrophages and neutrophils have in common?
A
They are reactive oxygen and nitrogen species.
All engulf the antigen
15
Q
Joining the constant region at the later mRNA stage in AB production, what does this allow?
A
Class switching at the later stages
The constant region of the heavy chain determines whether it’s Ig A D M E or G
16
Q
What do all 3 complement pathways result in the cleavage of?
A
C3——–> C3a + C3b
C3b leads to cleavage of C5——–> C5a + C5b
17
Q
What classes can the 2 heavy chains of antibodies be?
A
Class A, D, E, G or M
18
Q
What does high avidity of an AB mean?
A
They can bind a large number of AG’s as they may be pentameric and have several binding sites, but usually bind with weak affinity.
Eg IgMs pentomer
19
Q
What’s HLA - B27 associated with?
A
Increased risk of ankylosing spondylitis
Chronic arthritis.
Majority of ppl with B-27 are healthy
20
Q
What do lymphocytes have a large nucleus?
A
Involved with a lot of DNa transcription to make cytokines and antibodies
21
Q
What are the only cells that can activate T helper cells?
A
Antigen presenting cells of class II MHC
22
Q
igG antibodies are most abundant. Where Are these usually found?
A
In the circulation.
23
Q
What cells do APCs present AG fragments to?
A
T cells
24
What are hypervariable regions also known as?
CDRs- complementary determining regions.
25
What are igA Antibodies for?
These target airborne antigens
Present at epithelial / mucosal surfaces (as this is where airborne antigens target)
Remember A for airborne
Generally found in lungs (we inhale airborne ABs)
26
Actions of T helper cells?
Activation of macrophages
Triggers phagocytosis
Enhance recruitment of neutrophils
27
How do T cells decide whether to be cytotoxic T cells or T helper cells?
In the thymus T cells mature and encounter a range of self antigens
Once they engage with an MHC it helps to determine what they will become
28
Do IgG and IgE antibodies have low or high avidity?
Low
They are monomers
Only have 2 antigen binding sites
But will have HIGH affinity
29
What are the cytokines IL-1 and TNF produced by?
Macrophages that have been activated by LPS
These are PROINFLAMMATORY
This is why an inflammatory response occurs with bacteria but not viruses.
Because bacteria contain LPS activating infflamation.
30
Herceptin, does the antibody target and bind to receptor or ligand to stop ligand binding?
Receptor
31
What does IFNy do?
Stimulates a macrophage to kill a microbe
32
What do the complements C3a and C3b result in?
C3a resulting in INFLAMMATION drawing WBCs into tissues
C3b coats the microbe and enhances phagocytosis by opsonisation
33
Is type I diabetes mediated by destruction of pancreatic B cells by ANTIBODIES OR T CELLS?!!!
T CELLS!! NOT ANTIBODIES.
34
Cytokines of the adaptive immune system?
IL- 2, 4 ,5, 13
IFNy (both adaptive and innate)
TGFbeta [inhibitory]
TNFbeta
35
What do Th2 cells do?
Provide costimulatory help to B cells
| Secrete the cytokines IL-4 and IL-5
36
Most effector responses are carried out by the Fc region of an antibody. this is because.......
This region binds the Fc receptors on target cells such as neutrophils and macrophages.
37
What aspects of antigens are T cells able to recognise ?
Only able to recognise small fragments of antigens that's been broken up by APCs and presented to T cell on MHC complex (tray)
In contrast to B cells that can recognise epitopes of whole antigens that haven't been broken up.
38
Why do we say T cells have cell mediated immunity?
Because they secrete cytokines to activate other cells
39
What kind of things will toll like receptors respond to?
LPS- KEY ACTIVATORS
ds RNA
Bacterial peptidoglycans
These all tell them that the microbe is foreign
40
What happens to make 2 required regions sit next to each other in antibody production?
The DNA/ alleles in between in spliced out by recombinase enzymes.
41
What do natural killer cells do?
Lysis of virally infected cells
| Recognise viral antigens on cell surface
42
At first, before the B cells matured, what constant regions of the antibody are present?
```
All constant regions present at first coding for each class (C- A,G,M,D,E)
Remember AB starts as IgM
Then when class switching occurs, unwanted constant regions are spliced out.
```
43
When an APC presents an antigen to a T cell, what does the TCR interact with?
Both the MHC protein and the antigenic peptide fragments.
| It interacts with the MHC protein because this tells the t cell not to destroy the self cell.
44
What do T helper cells and cytotoxic T cells both contain on their surfaces?
T cell receptors
45
What do the enzymes recombinases do in antibody production?
Bring together the single V, J and D (depending on if it's light chain) alleles to make the required AB, then add on the constant region at a later stage.
They SPLICE DNA
46
Remember...
Natural killer cells cause Virally infected cell to die by APOPTOSIS, due to entry of granzyme through pores made by perforins.
Not phagocytosis!!!! ( like macrophage and neutrophil )
47
What do T regulatory cells express? CD___ and CD___
CD4 and CD25
| CD 25 also known as (IL-2Receptor.
48
What can antibodies target? Bacteria , viruses, both?
Both bacteria and virus antigens!
49
What is the lymphocyte repertoire?
Range of receptors able to recognise antigens in order for SPECIFIC RECOGNITION
50
What can the 5 constant regions of the heavy chains in ABs be?
IgA, D, M, G E. depends what class antibody you want to make.
51
What does the anti-TNF antibody do?
Mops up excess TNF
Antibody binds to the LIGAND TNF
Stops receptor binding and TNF activating inflammatory responses.
Used in conditions where you want to reduce inflammation eg, arthritis
Example drug: INFLIXIMAB
Remember TNF is proinflammatory
52
What happens when an antigen binds to pattern recognition receptors?
Phagocytosis by macrophages/ neutrophils
Cell may be killed by NK cells if virus
Presentation of fragments of AG to T cells by APC's
53
What do Th1 cells stimulate?
Activate macrophages and cytotoxic T cells
| Secrete cytokines such as IFNy (tells macrophages to kill a microbe)
54
What does binding to toll like receptors result in?
Up regulation of inflammatory gene expression! Ie INFLAMMATION
55
You can get a mixture of antibodies recognising different parts of one big antigen. These parts are ____ and this is a ____ response.
Epitopes
| Polyclonal response
56
Where does an antigen bind to an antibody?
At the ends of the Y shape.
Antigen binds in the groove between where heavy and light chains connect.
Variable regions of genes lie here, make antibody specific.
The rest of antibody usually have same structure as all others, apart from the Fc region.
Hypervariable regions also in the groove susceptible to mutations.
57
What does the anti HER2 receptor antibody do? What's this drug called?
This antibody binds to the HER2 recptor blocking ligand binding.
Stops receptor activation- stops cell growth and proliferation.
Drug = herceptin.
Used to treat BREAST CANCER
58
In the adaptive immune system, what are most cytokines produced by?
T cells
59
What does the Fc region of IgE antibodies binding to Fc receptors result in?
```
Eosinophil activation (WBCs responsible for killing parasites) and mast cell degranulation, resulting in histamine release.
igEs associated with allergies.
```
60
What is a somatic hyper mutation in an antibody?
A mutation in the hyper variable region of the binding groove/ in the amino acids that lie there.
61
In antibody production, splicing of RNA occurs until ____ is produced. What then needs to happen?
RNA spliced until mRNA (mature RNA) produced.
| Then translation of this mRNA into a protein making the antibody occurs.
62
Do T cell receptors undergo somatic hyper mutations?
No
They stay the same
With same low affinity for antigens
63
What is IL-12 produced by and what is its actions?
Produced by macrophages and dendritic cells
Promote natural killer cell cytolysis
It also stimulates the production if IFNy in T cells and NKCs
64
What does LPS present of the surface of some bacteria stimulate?
```
Local and systemic inflammation
WBCs leave blood to enter tissues
Increase tissue fluids
Increase cellular activators enzymes
Activate macrophages and neutrophils
Macrophage activation= cytokine release
Reactive oxygens burst- involved with digestion of AG
```
65
Alternate complement pathway involves....
Direct recognition of a microbe
| similar to using pattern recognition receptors
66
What are class IgD antibodies for?
B cell receptors
| On surface of B cells
67
What is the Fc region of an antibody coded for by?
```
The constant region of the heavy chain codes for Fc region.
Ig class therefore determines it.
```
68
IFNy job?
Secreted by T helper cells
| Activates cytotoxic T cells and macrophages
69
What cytokine promotes Th1 production but inhibits Th2?
IL-12
70
How many different ABs can be made through gene rearrangement in order to recognise specific antigens?
10^7
71
What would mutations in gene sequences anywhere around the variable region of an antibody cause?
Change the shape of the antigen binding groove.
Causes the antibody to have a different affinity for the antigen.
CDR mutations (hypervariable regions) can result in this.
72
Is the complement cascade part of the innate or adaptive immune system?
Innate.
| It naturally occurs whenever a microbe attacks to trigger other proteins to do their jobs such as neutrophils.
73
What is IL-12? Secreted by?
A cytokine
By macrophages and dendritics
T cell stimulating factor
74
We react to antigens in different ways from individual to individual.
This is because we inherit ___ different genes coding for different ___ classes.
12 different genes
| MHC classes
75
Effect of binding to 7 alpha helical transmembrane receptors?
Increased integrin avidity (higher affinity of integrin receptors)
Stimulated migration into tissue
Does not result in killing of the microbe!!!!
76
How do T cells provide a costimulatory signal to tell B cells to produce antibodies?
They upregulate CD40 ligand
This engages with CD40 on B cell. Tells it to make antibodies.
Also T cell produces IL-4 and IL-5 which tell a B cell to make antibodies.
77
The part of an antibody that recognises a single epitope is the ____
Paratope
78
Basic job of pattern recognition receptors?
Recognise structures on microbes that aren't present on self proteins.
Present of neutrophils macrophages and dendritic cells.
4 types
79
IL 4 & 5 job?
Activate B cells to produce antibodies
80
What makes an antibody specific, regarding its structure?
The variable gene region in the binding groove.
Also hypervariable regions in the groove that easily mutate.
Also nucleotides at junctions between V D and J regions can change increasing diversity further.
81
What can T helper cells further be divided into?
Th1 and Th2
| Big cytokine producers
82
What kind of domains do Fc regions contain?
CONSTANT domains
83
Infliximab, does the antibody target and bind to receptor or ligand to stop ligand binding?
Ligand
84
2 light chains of antibodies can be what classes?
Kappa and lambda
| These are the classes of the light chains constant region.
85
What do natural killer cells recognise microbial markers on the surface of?
Already infected cells usually viral (not on microbes)
| Recognise through patter recognition receptors
86
Must abundant type of WBC?
Neutrophils
| Small so they can easily enter tissues
87
An antibodies specificity for an antigen never changes. Ie the antigen it targets will always be the same. However, what can change?
The antibodies AFFINITY for the antigen can change,
| due to the hyper variable regions in the binding groove.
88
Does the receptors involve in the immune response affinity for AG increase or decrease during the response?
Increase!
89
What is the name of the components of a compliment system?
Zymogens
90
What cytokine promotes Th2 production but inhibits Th1?
IL-4
91
Antibodies provide active and passive immunity. What does this mean?
Active; antigens given as a vaccine are killed off by antibodies. Antibodies learn how to target antigen in case of further infection.
Active = you actively make the antibodies YOURSELF
Passive: immunity to a certain antigen has been passed on from genetic traits. (inherited)
IT IS THE TRANSFER OF AN ANTIBODY FROM ONE INDIVIDUAL TO ANOTHER.
Don't make the AB yourself.
92
What is Negative selection?
When T cells are undergoing Thymic selection, and a Tcell binds too strongly to self antigen and becomes activated, these T cells are signalled to die as they must be SELF REACTIVE T cells!!
93
What is the adaptive immune system triggered by?
The innate immune system
94
Lipopolysaccharides are also known as....
ENDOTOXINS
95
What are heavy and light chains bound togetherby?
Disulfidebonds
96
The small part of an antigen that an antibody/ T cell receptor recognises is the _____
Epitope
Antibodies have different specificifities for different epitopes
One antigen lots of different epitopes= (a polyclonal) as lots of diff ABs respond
97
What does ADEPT stand for?
Antibody directed enzyme prodrug therapy.
98
What does excessive LPS stimulation cause?
Systemic inflammatory response syndrome (fever, septic shock, too much inflammation)
99
What are the effects of microbes binding to toll like and mannose receptors?
Production of CYTOKINES
Reactive oxygen intermediates; v. Toxic to microbes= kill the microbe
Phagocytosis
100
What do peritoneal lymphocytes secrete antibodies against?
Lipoplysachharides (LPS)
101
What are the 4 types of patter recognition receptors?
Mannose receptors- recognise sugars
Receptors for opsonins- enhance phagocytosis
Toll like receptors- recognise proteins on AG
7transmembrane alpha helical receptors - recognise peptide fragments
102
How is the signal of an antigen binding to a B cell enhanced?
Hint; what 2 things present on the B cell surface enhance this...
The B cell receptor (antibody on surface)
| Together with a COMPLEMENT BINDING CORECEPTOR on surface
103
How many ABs do plasma B cells usually hold?
Around 2000.
104
What are lymph nodes classed as?
Secondary lymphoid organs
| Once B and T cells are mature but naive, they migrate to the lymph nodes
105
Do T cell receptors have high affinity or low affinity for antigens?
Low affinity
| That's why T cells have to be presents antigens by antigen presenting cells.
106
What do TNFa , IL-1, E-selectin, and iNos result in?
Enhance white blood cell movement from blood to tissue to create inflammation
107
What can bind to 7 alpha helical transmembrane receptors?
Chemokines
Lipid mediators
N formyl methyl peptides (bacterial peptides)
108
What are antigens recognised by on T cells and B cells?
TCRs on T cells ( T cell receptors)
| Antibodies on B cells
109
Which immune system are pattern recognition receptors and LPS involved in?
Innate immune system
110
How do IgG and IgM trigger complement activation?
By binding C1q
111
What are IgE antibodies for?
For targeting parasites and immediate hypersensitivity (allergeeeee reactions= E)
112
What are adjuvants?
Activate the immune system
Included in vaccinations
Enhance the recipients immune response to a given non pathogenic antigen.
Help lots of antibodies to be produced.
113
Where does the Fc region of IgG antibodies bind? What does this promote?
To Fc receptors on surfaces of neutrophils and macrophages.
Promotes phagocytosis
Both AB and AG are destroyed.
114
How do NKCs work?
Perforins released- make holes in target cell membrane
This allow entry of granzyme (digestive enzyme)
Infected cell is sacrificed and dies by apoptosis
Destroys viral load (target cells for NKCs are virally infected)
Apoptosis not phagocytosis!
115
What cells recognise class I MHCs?
CD8 cytotoxic T cells
| Presented on virally infected cells
116
What do activated Tc cells target?
Viruses!
| Tc cells kill virally infected cells by apoptosis
117
TGF beta job?
Inhibitory cytokine
| Acts to dampen the immune system and restore homeostasis (Like Treg cells)
118
What cells recognise MHC class II?
CD4 T helper cells
| Th1 and Th2
119
What do naive T cells (mature T cells that haven't yet encountered an ANTIGEN ) posses? CD__
CD28
120
T helper cells surface molecule is___
CD4
121
What happens to B cells AB avidity to antigens as they mature?
As they mature, the B cell switches classes (from IgM)
The avidity decreases
Their affinity to antigens increases with more mature B cells.
Less mature= igM = 10 binding sites, pentameric, High avidity.
122
Which has a smaller antigen binding groove, class I or class II MHC?
```
Class I has a smaller
class II has a larger
```
123
3 ways the complement cascade can be activated?
Classical
Alternate
Lectin
124
What effect does the complement C5a have?
It is chemotactic for neutrophils (WBCs)
| Draws them out of blood into tissues of infected site
125
2 proinflammatory cytokines to remember;
IL1 (interleukin 1)
TNFalpha
These enhance Inflammatory response by drawing WBC's out blood Into tissue to fight the antigen.
126
What does each chain of an anti body have?
| What do heavy chains have that light chains don't?
All chains have several Ig domain repeats
All chains have variable , joining and conserved (constant) regions
Heavy chains also have diversity regions
127
Classical pathway of complement cascade involves.....
C1 detects an ANTIBODY bound to the microbe
| Then it cleaves C2/C4 starts the cascade...
128
Where are AGs that enter the body/ AG's that are blood Bourne get taken?
AGs that enter the epithelia get taken to the lymph node via the lymphatics
AGs that are blood borne are carried to the spleen ( similar to lymph nodes, cleans the blood)
Spleen and lymph nodes= secondary lymphoid organs
129
What do B and T cells become on activation? ____ ___
Effector cells
130
How is NKCS actions inhibited?
By MHC Class I binding to inhibitory receptors on surface of NKCs.
Stops it invading any uninflected healthy self cells.
131
What cells act as APCs?
Dendritic cells (main type)
B cells
Macrophages
132
What 2 chains are MHC class I peptides made of? What about MHC class II?
Class I alpha 1 and alpha 2 chains
| Class II alpha 1 and beta 1 chains
133
What can heamopoeitic stem cells form?
RBC's, myeloid cells, lymphocytes
134
What 2 molecules make up signal 2, the ACTIVATION signal?
CD 28 on T cell surface.
B7-2 on APC surface.
These bind forming signal 2
These are the main costimulatory molecules.
135
Cytotoxic T cells surface molecule is___
CD8
136
How is a B cell told that enough antibodies have been produced and deactivated?
Signal downregulated by when the Fc region of antibody binds back onto the Fc receptor of the B cell telling it to stop producing antibodies.
137
What are T cell receptors associated with on T cell surfaces?
CD3 signalling chains
138
Features of macrophages?
```
Granulocyte
Rounded nucleus
Secrete cytokines
Phagocytose
Lots of organelles
Inflammatory mediators
Complement proteins
Help with antigen presentation
```
139
Where are the hypervariable regions located?
They protrude into the antigen binding groove.
140
What does Fc region stand for?
Fragment crystallisable region.
141
When activated, T cells swell in size. We call this _____
Blasting
142
What triggers Ig class switching?
Activation of a B cell
143
What are both natural killer cells and dendritic cells?
INTERFERONS
| Interfere with viral reproduction
144
What kinds of things can you attach to an antibody to target an antigen?
Liposomes
Toxins
Radionuclides
Cytokines
145
What anti-inflammatory cytokines do T regulatory cells secrete?
IL-10, TGFbeta
146
What inhibits signalling on surface of the B cell?
Fc receptor
| Binding to Fc region of an antibody
147
```
What antibody class are produced on first antigen encounter?
What are these for?
```
IgM
For complement activation
These are natural ABs in the lining of the abdominal cavity(peritoneum)
Remember IgM= complEMent activation
148
All 4 cells of the innate system use______ receptors. What are these 4 cells?
Pattern recognition receptors.
| Macrophages, neutrophils, dendritic cells, natural killer cells
149
What happens if a CDR undergoes a mutation?
Changes the affinity of an antibody for an antigen
150
What are LPS a product of/ found in?
Cell walls of gram NEGATIVE bacteria
151
What are complemtary determining regions?
3 regions within variable gene segments with highly variable amino acid sequences.
CDR 1,2,3
Combining CDRs from heavy and light chains increases the diversity of ABs allowing them to bind to diff AGs
Also known as hypervariable regions and are particularly susceptible to mutations
152
What 2 molecules make up the INHIBITORY SIGNAL of T cells , dampening the immune response?
CTLA-4 and B7-1
These switch off activation of T cell
Produced by T cell
153
As a B cell matures, what class does it change from the starting IgM class to?
IgD class
154
M N O P.... alphabet.....
Macrophages and neutrophils ..... Phagocytosis!
155
What are hypervariable regions particularly susceptible to?
Mutations
156
What are bone marrow and the thymus classed as?
Primary lymphoid organs
T cells produced in bone marrow, mature in thymus
B cells produced and mature in bone marrow
157
Features of dendritic cells?
```
Large cell
Small nucleus
Membrane protrusions; engulf antigens
Antigen presentation
Release cytokines
```
158
What does IL-2 stimulate?
Growth factor of T cells, increases their number
159
What is positive selection?
When undergoing Thymic selection and T cells are deciding whether they want to be T helpers or cytotoxic, if the T cell doesn't encounter and bind and MHC the cell will be signalled to die as it has not recognised a self antigen.
160
What is peripheral tolerance?
TCR binding to an MHC bound to an antigen is not enough alone to activate T cell. You need costimulatory molecules to produce a second signal. This is the basis of why T cells don't become activated in inappropriate situations.
161
How much of plasma proteins do antibodies take up?
20%
162
Which G protein subunits are the ephindrine and acetylcholine receptors coupled to?
Ephindrine= Gs, increasing cAMP
| Acetylcholine (muscarinic) = Gi, decreasing cAMP
163
Where are nuclear receptors located?
Inside the cell. They are intracellular. Not in nucleus but in cytoplasm.
164
How do you measure the activity of an ion channel?
Use patch clamp recordings
165
Is Ras attached to the cell membrane? By what
Yes by a covalently attached lipid
166
What is direct cell-cell signalling?
Receptor on surface of one cell detects ligand on surface of other cell. Cells physically connect.
167
What is the job of Arf?
Regulates vesicular trafficking and activated phospholipase D. Remember Arf= vesiculARf trARFficking!!!!
168
IP3 is short for...
Inositol 1,4,5 triphosphate
169
Example of a death receptor?
Fas receptor
| Fas protein binds to a Fas ligand on a killer lymphocyte cell
170
How many phosphate groups does adenylyl cyclase remove from ATP?
2 , forming a mono phosphate cAMP
171
How do you form AMP from cAMP?
Use enzyme cyclic AMP phosphodiesterase. It breaks the cyclic part of the molecule (doesn't add or remove anything just breaks)
172
What are class 1B PI3Ks composed of? What subunits?
P101 regulatory subunit that interacts with the Gby subunit of GPCRs.
P110y catalytic subunit for 3 hydroxyl phosphorylation
This is a heterodimer
173
What are class II PI3Ks activated by?
Receptor tyrosine kinases
Cytokine receptors
Integrins
174
What are class 1A PI3Ks composed of? What subunits?
P85 regulatory subunit (with 2 SH2 domains)
P110 catalytic subunit for 3 hydroxyl phosphorylation
This is a heterodimer
175
What is a heteromeric ion channel?
| What is a homomeric ion channel?
Heteromeric channels are composed of several different subunits
Homomeric channels are composed of the same subunits
176
What factors activate rho?
Soluble factors of blood serum such as lyso-phosphatidic acid(LPA).
Rho drives formation of stress fibres in cell reorganising the cyto skeleton.
177
Why is negative feedback in cell signalling important?
If you can't turn a signal off it may result in a tumour forming.
178
What is autocrine cell signalling?
Cell signals to ITSELF. the molecule released acts back on itself.
179
What do Bad and Bax have in common?
Both promote cell death
180
What is the ultimate response of the Ach signal binding to ACh receptors?
Muscle contraction.
Opening of Na+ channel (reception) then Influx of Na+ and depolarisation of membrane (transduction) results in Ca2+ release which in turn results in muscle contraction as the ultimate response.
181
What doe capsaicin, menthol and mustard oil open?
TRP channels on cell membrane
Capsaicin opens TRPV1
Menthol opens TRPM8 (mint m8)
Mustard oil opens TRPA1
182
What is the class II PI3Ks structure like?
A single p110- like catalytic subunit
| Called either PI3KC2alpha ,PI3KC2beta. ,PI3KC2gamma
183
What switches Ras on and off?
GEF (SOS protein) switches ON
| GAP (activating GTPase) switches it OFF
184
What refills calcium stores in the muscle cell?
Ca2+ ATPase called SERCA
185
How many amino acids is the pleckstrin homology domain made of?
120
This domain allows docking of proteins to plasmamembranes
186
Where a outs does ACh bind on the receptor?
ACh binding sites are on the extra cellular portion of the receptor at the interface between the alpha and adjoining subunits.
187
With GPCRs, what happens when an an agonist binds? (explain mechanism)
GPCR undergoes a conformational change.
Causes it to have Hugh affinity for a subunit of G protein.
These bind, GDP release and GTP takes its place.
B-y subunits dissociate from a-GTP complex.
These are now active.
a-GTP complex can bind to target protein, activating it.
GTP hydrolysed to GDP by GTPase activity of alpha subunit, caused by it being attached to the target protein.
Alpha subunit now is associated with GDP again, detaches from target protein as its now inactivated.
188
How does PKB associate to the cell membrane?
Phosphorylation of membrane lipids
189
In the intrinsic pathway what does the effector caspase 3 do?
Cleaves and inactivated cellular components such as:
Cytoskeleton components eg actin
DNA repair enzymes
PKC( eventually leas to cell growth is it was active)
Activates a DNA ase, cleaves DNA
Leads to cell death!
190
Where does Ran--> GDP Ran occur?
| And Ran--> GTP Ran?
Ran combines with GDP IN THE CYTOPLASM OUTSIDE THE NUCLEUS.
| Ran combines with GTP IN THE NUCLEUS.
191
How does Arf regulate vesicular traffic?
Recruiting COAT proteins, regulating phospholipid metabolism, modulating structure of actin at membrane surfaces.
Arf starts off inactive, then GDF/ GEF exchange. GTP- ARF complex binds coatomer proteins around Golgi membranes.
This forms a vesicle. When the vesicle reaches the membrane to fuse with it, coatomer proteins and ARF-GTP complexes detach.
192
What is HER2?
A receptor in the EGFR family.
Over expressed in breast cancers; causes cell proliferation and growth to span out of control.
HER 2 initiates the MAPK pathway
Treated with Herceptin
193
How many caspases are there?
Approx. 9
194
What is the nicotinic acetyl choline receptor directly coupled to?
It is a ligand gated ion channel directly coupled to a cation selective ion channel
195
What is paracrine cell signalling?
Cell signals to a nearby neighbour by release of a molecule.
196
How many subunits is the acetyl choline receptor made up of?
5
| a,a,B,δ,y
197
Difference between competitive and non competitive inhibitors?
Non competitive; binds somewhere else on receptor causing a conformational change so that the ligand can no longer bind.
Competitive: competes for same binding site as ligand, stops the response.
198
What are low molecular weight g proteins? Example?
Superfamily of small g proteins.
They are classes as g proteins as the bind guanine nucleotides (GDP, GTP).
They're a different class to hetertrimeric G proteins, only contain one kind if subunit.
Example is Ras.
199
Target molecule of the Gprotein in the CREB pathway? And the IP3 pathway?
```
cREB= adenylyl cyclase
iP3= phospho lipase C
```
200
What are PI3K's activated by?
By receptor tyrosine kinases (RTKs) and G protein coupled receptors
201
What does MAPK stand for?
Mitogen active protein kinase
| This is a family of serine threonine protein kinases
202
What are the 3 steps in the MAPK pathway after Ras activation?
Activates Ras recruits and activates Raf
Raf then phosphorylates and activates MEK
MEK then phosphorylates and activates MAPK (ERK)
203
What is an IAP?
Inhibitor of apoptosis
Binds to some pro caspases to inhibit their activation
Binds to activated caspases to inhibit their activity
204
What do GTP/GDP do to the alpha subunit?
GTP ACTIVATES IT
| GDP DEACTIVATES IT
205
What are integrins and cytokine receptors an example of?
Receptor linked protein kinases
206
What does a kinase enzyme do?
It will phosphorylate it's substrate.
Or phosphorylase itself (auto phosphorylation)
ATP is the source of phosphate
Phosphates can be added to tyrosine threonine or serine amino acids.
207
What 3 ligand gated ion channels associated with calcium can you think of?
ATP GATES P2X RECEPTORS
NDMA RECEPTORS (GLUTAMATE ION CHANNELS)
TRP CHANNELS
208
What does Tor do?
It's a large serine/threonine kinase activated by AKT.
| It stimulates cells to grow by enhancing protein synthesis.
209
What are insulin receptors and EGF receptors an example of?
Receptor protein kinases
210
How do we detect calcium?
Fura-2 calcium indicator
Fluorescent indicator, changes colour when binds to calcium.
Membrane impermeable; add AM to make it permeable
Forms fura2AM
Once in cell, AM cleaved back off
Dye is now trapped in the cell.
Detects changes in cytosol [calcium]
211
What do mechanically gated ion channels do?
Open in response to mechanical movement of adjacent structures, respond to stretch and temperature.
212
What does the Gi subunit do to adenylyl cylase ?
Inhibits it.
| Decreasing cAMP formation.
213
Difference between receptor protein kinases and receptor LINKED protein kinases?
Receptor protein kinases;
The cytoplasmic portion of the receptor contains a tyrosine kinase. (receptor itself contains the kinase). The kinase is activated when ligands bind to receptor portion.
Receptor linked protein kinases; no natural kinase activity. When a ligand bind receptor activates an associated cytoplasmic tyrosine kinase.
214
What is the code for the catalytic domain in both class 1A and 1B PI3Ks?
p110!!!!!
| This adds a phosphate group onto inositol phospholipids by 3 hydroxyl phosphorylation
215
What is the job of Raf?
It has a role in secretory and endocytotic pathways. Just remember this.
216
What does Bcl-2 do?
Inhibits apoptosis
217
How is the acetyl choline receptor structure determined?
By crystallography experiments
218
What would you treat osteoarthritis , aplastic anaemia (RBC death) , myocardial infarction (heart cell death) and stroke (brain cell death) with?
Treat with caspase inhibitors!
219
What is the job of Rho?
Reorganises the cyto skeleton by serine threonine protein kinases. RhO ReOrganises!
220
How do proteins/ RNA pass through nuclear pores? What helps them?
Pass through with help of Ran-GDP complex and by bonding to IMPORTIN a transport protein.
The proteins contain an amino acid sequence called the nuclear localization signal.
In the nucleus, Ran becomes GTP-Ran which helps importins and proteins dissociate from eachother.
Exportins help move things out of the nucleus.
221
What is long QT syndrome? What channel tends to be effected by this?
hERG (Kv1.11) is a voltage gated potassium channel.
This channel mediates the repolarisation of the cardiac action potential in the heart and is essential in keeping a normal cardiac rhythm.
Mutations in this ion channel may inhibit it causing delayed repolarisation of the heart after a heart beat. This can lead to TDP, an irregular heartbeat. This results in the prolongation of the QT interval and can result in sudden death.
222
What type of cell death is mediated by death receptors?
Extrinsic apoptosis
223
What effect does ischemia reperfusion have on a cell?
Ischemia reperfusion= lack of oxygen/ glucose to the cell
Causes membrane channels to open and extracellular fluid to flow into cell
Causes organelles to swell
Cell eventually bursts
224
What happens when Ach binds to the ACh receptor?
The kinked alpha helices that act as a gate swing out the way and open the channel pore.
Opening the pore allows NA+ and K+ to diffuse down the channel depolarising the membrane.
225
What PI3K inhibitor drugs exist to prevent cancer?
Penicillin wortmannin- irreversibly binds
LY294002- reversibly binds
226
What is the pathway of cell signalling (4 stages)?
Signal, reception, transduction, response.
227
What receptor protein kinase is Ras linked up to?
EGF receptor
228
What is the ultimate response the inositol phospholipid pathway leads to? And the CREB/PKA pathway?
IP3 pathway leads to an intracellular rise in CA2+ which leads to the response of cell proliferation, survival and death.
CREB pathway leads to a increase in gene transcription
229
What do class I PI3ks generate?
PI3s
230
Is the ACh receptor heteromeric or homomeric?
Heteromeric, consists of different subunits
231
Where is the death domain of a death receptor?
In its cytoplasmic tail.
232
What is used to treat HER2 associated cancer ?
Herceptin (monoclonal antibody treatment) interferes with the HER2 receptor.
233
What's the catalytic domain of class III PI3Ks called?
VPS34
234
What are the class 1 PI3K inhibitor drugs in clinical trials likely to treat?
3/4 treat advanced solid tumours; exelixis, GSK, Genentech
| Novartis treats phase 1-11 solid tumours
235
What is endocrine cell signalling?
Uses hormone transported in blood to send messages throughout the body.
236
What does Bad do?
Binds and inhibits death- inhibiting proteins like Bcl2
| When active it binds to and inactivates these death-inhibitory proteins
237
What is Grb2?
An adaptor protein. Its SH2 domain binds to the phospho tyrosine residues of the EGF receptor. It's SH3 domains then recruit SOS protein which in turn activates Ras by GDP/ GTP exchange.
238
How many cells are Eliminated from the body everyday?
10 billion cells.
Shedding intestinal lining,
Dying neutrophils,
Turnover of tissues
239
What is the name of the enzyme that activates inactive pro caspase to caspase?
Initiator protease enzymes
Cleaves pro caspase at 2 sites
Release of the prodomain activates the caspase
240
What do g protein coupled receptors consist of?
Seven transmembrane alpha helices
Intracelluar loop (the largest loop interacts with the g protein)
3 subunits: alpha beta gamma. Forms a-B-y trimer.
Binding domain for agonist on the receptor molecule.
Binding site for GDP/ GTP on the a subunit.
241
Example of a member of the EF hand family?
Calmodulin
Has 4 Ca2+ binding sites in its loop domain
Targets calcium dependent protein kinases
And targets plasma membrane Ca2+ATPase pump
242
Is the N terminal domain intracellular or extracellular? What is it for? What is the C terminal for?
N terminal is extracellular is extracellular and is the binding domain where ligands bind. It contains carbohydrates also for increased specificity.
C terminal is intracellular, it is the part that interacts with the alpha subunit of the g protein.
243
What is the job of Ran?
Transport of RNA and proteins into and out of nucleus. Remember RAN= RNA. Transport = run/ ran.
244
3 domains of the nuclear receptor superfamily?
Ligand binding
DNA binding
Transcription activation (gene transcription)
245
How is Ras's activity terminated?
By GTPase activating protein
| GTPas is activated and take a phosphate group off GTP attached to Ras, converting it back to GDP and deactivating Ras.
246
What are the 2 phosphoinositide3-kinases (PI3Ks)??
Pi-4 kinase
PIP-5 kinase
they both use ATP as the phosphate source
247
What is the EF hand?
A helix - loop- helix structural domain found in a large family of calcium binding proteins.
248
Difference between nicotinic and muscarinic Ach receptors
Nicotinic are ionotropic receptors, meaning that they allow ions to pass through them when they bind to acetylcholine. Therefore, these receptors help depolarize the cell in response to acetylcholine and are excitatory.
Muscarinic are metabotropic receptors (G-protein coupled receptors). They activate G-proteins in response to acetylcholine and these G-proteins can have different cellular responses depending on which G-proteins are activated.
249
What are patch clamp recordings?
```
A patch of membrane with a single ion channel on it is monitored.
The current of this ion channel is recorded using an electrode.
The flickering (opening and closing) of an ion channel is detected on the recording.
Allows the very small current flowing through an ion channel to be measured directly.
```
250
Another name for ligand gated ion channels?
Ionotropic receptors.
251
What does PI3K's stand for
Phosphoinositide 3 kinases
| They ADD A PHOSPHATE GROUP onto inositol phospholipids
252
What is extrinsic apoptosis mediated by?
Death receptors
| Not part of cells nature
253
What must drugs be in order to bind to nuclear receptors?
LIPID SOLUBLE. they have to cross the cell membrane to reach the nuclear receptor. ( lipophillic)
254
What does phospho Kinase C need to bind to to become activated?
DAG, calcium and phosphotide serine (a lipid). It becomes attached to the membrane due to DAG and phosphotide
It is inactive when the pseudo substrate domain is still in tact.
255
What turns pI3K signals off?
Lipid phosphatase PTEN protein.
Converts PIP3 to PIP2
No presence of PiP3 means AKT is no activated and no cell growth and proliferation occurs.
It's a tumour suppressor.
256
How do you switch on/off phosphorylation signals?
Switch things ON using PKAs to phosphorylate things= activates it
Switch off using protein phosphatase 1, an enzyme which cleaves the phosphate group off = deactivates it.
257
How is the IP3 signal terminated?
By phosphatases (enzymes) or by further phosphorylation forming inositol 1,3,4,5 tetrakisphosphate.
258
What is the Erolitnib tyrosine kinase inhibitor used to treat?
Non small cell lung cancer (NSCLC)
This drug inhibits tyrosine kinase enzymes so stops phosphorylation and therefore stops the pathway leading to cell growth and proliferation from working (MAPK pathway)!!!
259
Which 3 amino acids present of proteins can phosphates be added to by Kinase enzymes?
Tyrosine, threonine, serine
260
What does Bax do?
Promotes cell death by inducing cytochrome C release from mitochondria
261
Which G alpha subunits target adenylate cyclase?
| Which target phospho lipase C?
Adenylate cyclase=Gi and Gs
| PLC= Gq
262
What are the dangers of mutated Ras protein?
Can slow down GTP hydrolysis resulting in Ras being 'locked ' in the on position.
Can cause uncontrolled cell division leading to cancer.
Mutated Ras found in human oncogenes (20-25%)
Ras is a target for anitcancer drugs
263
4 examples of ligands for ligand gated ion channels?
NDMA, Glycine, GABA, Ach
264
Where are ligand gated ion channel receptors located?
The membrane of a cell. Occur in all cell types.
265
2 other names for g protein coupled receptors?
7transmembrane, metabotrophic
266
What receptors can activate phospho lipase C to increase cytosolic calcium?
Tyrosine kinase receptors, &
| ACh binding to GpCRs
267
The permeability of ____ increases when Ach binds to the Ach receptor?
Na+ and K+ . This causes the membrane to depolarise carrying the action potential.
268
What family do death receptors belong to?
Tumour necrosis factor receptor family (TNFR)
Names of receptors:
TNFR1
CD95
269
What is CREB responsible for?
Regulating gene transcription and is involved with nuclear signalling.
It's a PKA target and is a cAMP response element binding protein (CRE binding protein)
270
Class 1PI3K's are activated by.......class 1A PI3K's are activated by........and class 1Bs.........
Class 1: cell surface receptors
Class 1A: receptor tyrosine kinases
Class 1B: regulated by G protein coupled receptors, act on the Gby subunit of GPCRs
271
What is calmodulin?
A calcium binding messenger protein CARRIER OF CALCIUM
Transduces calcium signals by binding to calcium then interacting with target proteins.
As many of the proteins CaM binds to cant bind calcium themselves.
272
What happens when cAmP binds to protein kinase A's?
cAMP attach to the regulatory subunits of the PKA. This causes the 2 catalytic subunits to become activated and are released from the regulatory subunits. The catalytic subunits have kinase activity.(go on the phosphorylase proteins)
273
Basic definition of a receptor?
Receptors are proteins that bind to specific ligands/agonists.
Receptors have an affinity for the ligand.
274
What is AKT/PKB activated by?
PIP3
Produced from activated PI3Ks
275
Which parts of class 1A and 1B PI3Ks interact with the areas in which they act on?
The REGULATORY SUBUNITS.
| SH2 domains and Gby subunits attach here
276
What does the FGF receptor inhibitor PD173047 do?
Inhibits the fibroblast growth receptor.
Stops small cell lung cancer growth
Inhibits FGF2 signalling pathways (uses Ras as signalling molecule then MAPK pathway)
This pathways blocked, stops cell growth and proliferation
277
What can you think of that down regulates/ reduces the amount of calcium in the cytosolic?
NCX exchanger in cell membrane pumps Ca2+ out and Na+ in.
SERCA; membrane of ER/ SR. ca2+ ATPase, transfers CA2+ from cytosol into SR/ER.
PMCA; plasma membrane calcium ATPase. Removes CA2+ from the cell.
278
What does DAG activate?
Activates serine/threonine kinases, especially protein kinase C (in the Inositol phospholipid pathway).
Increase in cytosolic Calcium causes DAG to bind to the protein kinase C, activating it.
PKC needs to bind to DAG, calcium and phosphotide serine (a lipid) to become activated!!
279
What are CRE's?
cAMP response elements.
They are DNA sequences that the cellular transcription factor CREB binds to to upregulate or down regulate transcription of the genes.
280
How is Bad deactivated and what does this allow?
By protein kinase B (AKT).
It phosphorylates BAD, making it release the death inhibitory protein it was holding onto.
Promotes cell survival as Bad encourages apoptosis of a cell.
AKT also activates Tor, a protein that stimulates cells to grow in size
281
Job of Ras?
Cell growth regulation via serine-threonine protein kinases. Activates a phosphorylation cascade.
282
When Bad is active , what does it encourage?
A cell to kill itself by apoptosis
283
What does the Gs subunit do to adenylyl cylase?
Stimulates it, increasing cAMP formation.
