Flashcards in Pa20292 Deck (284):
Why are IgG antibodies so important?
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
What activates cytotoxic T cells ?
Antigen presenting cells of class I MHC
Usually present viral fragments
Can also be stimulated by T helper Th1 cells
What shapes do each of the different classes of antibodies have? Ie monomer, dimer....
Monomers= IgE IgG
Dimers = IgA
The lectin complement cascade pathway involves.....
Mannose receptor binding to lectin and cleaving C4
What receptors (ABs) do B cells express once matured but before class switching?
IgM and IgD receptors
Remember; class switching and somatic hypermutations improve antibody affinity and function
How are NKcs activated ?
IL-12 from macrophages
Activates NKCs, they secrete IFNy
IFNy Feeds back and activates macrophage
(positive feedback loop)
Some features of neutrophils?
Large multi lobed nucleus
Lot of organelles
Contain antmicrobial enzymes
Do therapeutic antibodies tend to be polyclonal or monoclonal?
Act against one particular epitope of an antigen
Activation of a single B cell= monoclonal response
Who were vaccinations discovered by and when?
By EDWARD JENNER
What cells is MHC protein present on?
Every cell apart from RBC's
What type of immunity do B cell produce?
Means antibody mediated immunity
Why do antibodies remain specific to a certain antigen for the rest of its life?
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.
What is inhibition of development of Th1 or Th2 cells by cytokine IL-4 and IL-12 known as?
When activated, B cells swell in size. We call them _____
Produces large numbers of antibodies
What do dendritic, macrophages and neutrophils have in common?
They are reactive oxygen and nitrogen species.
All engulf the antigen
Joining the constant region at the later mRNA stage in AB production, what does this allow?
Class switching at the later stages
The constant region of the heavy chain determines whether it's Ig A D M E or G
What do all 3 complement pathways result in the cleavage of?
C3--------> C3a + C3b
C3b leads to cleavage of C5--------> C5a + C5b
What classes can the 2 heavy chains of antibodies be?
Class A, D, E, G or M
What does high avidity of an AB mean?
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
What's HLA - B27 associated with?
Increased risk of ankylosing spondylitis
Majority of ppl with B-27 are healthy
What do lymphocytes have a large nucleus?
Involved with a lot of DNa transcription to make cytokines and antibodies
What are the only cells that can activate T helper cells?
Antigen presenting cells of class II MHC
igG antibodies are most abundant. Where Are these usually found?
In the circulation.
What cells do APCs present AG fragments to?
What are hypervariable regions also known as?
CDRs- complementary determining regions.
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)
Actions of T helper cells?
Activation of macrophages
Enhance recruitment of neutrophils
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
Do IgG and IgE antibodies have low or high avidity?
They are monomers
Only have 2 antigen binding sites
But will have HIGH affinity
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.
Herceptin, does the antibody target and bind to receptor or ligand to stop ligand binding?
What does IFNy do?
Stimulates a macrophage to kill a microbe
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
Is type I diabetes mediated by destruction of pancreatic B cells by ANTIBODIES OR T CELLS?!!!
T CELLS!! NOT ANTIBODIES.
Cytokines of the adaptive immune system?
IL- 2, 4 ,5, 13
IFNy (both adaptive and innate)
What do Th2 cells do?
Provide costimulatory help to B cells
Secrete the cytokines IL-4 and IL-5
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.
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.
Why do we say T cells have cell mediated immunity?
Because they secrete cytokines to activate other cells
What kind of things will toll like receptors respond to?
LPS- KEY ACTIVATORS
These all tell them that the microbe is foreign
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.
What do natural killer cells do?
Lysis of virally infected cells
Recognise viral antigens on cell surface
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.
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.
What do T helper cells and cytotoxic T cells both contain on their surfaces?
T cell receptors
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
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 )
What do T regulatory cells express? CD___ and CD___
CD4 and CD25
CD 25 also known as (IL-2Receptor.
What can antibodies target? Bacteria , viruses, both?
Both bacteria and virus antigens!
What is the lymphocyte repertoire?
Range of receptors able to recognise antigens in order for SPECIFIC RECOGNITION
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.
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
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
What do Th1 cells stimulate?
Activate macrophages and cytotoxic T cells
Secrete cytokines such as IFNy (tells macrophages to kill a microbe)
What does binding to toll like receptors result in?
Up regulation of inflammatory gene expression! Ie INFLAMMATION
You can get a mixture of antibodies recognising different parts of one big antigen. These parts are ____ and this is a ____ response.
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.
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
In the adaptive immune system, what are most cytokines produced by?
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.
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.
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.
Do T cell receptors undergo somatic hyper mutations?
They stay the same
With same low affinity for antigens
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
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
Alternate complement pathway involves....
Direct recognition of a microbe
(similar to using pattern recognition receptors)
What are class IgD antibodies for?
B cell receptors
On surface of B cells
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.
Secreted by T helper cells
Activates cytotoxic T cells and macrophages
What cytokine promotes Th1 production but inhibits Th2?
How many different ABs can be made through gene rearrangement in order to recognise specific antigens?
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.
Is the complement cascade part of the innate or adaptive immune system?
It naturally occurs whenever a microbe attacks to trigger other proteins to do their jobs such as neutrophils.
What is IL-12? Secreted by?
By macrophages and dendritics
T cell stimulating factor
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
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!!!!
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.
The part of an antibody that recognises a single epitope is the ____
Basic job of pattern recognition receptors?
Recognise structures on microbes that aren't present on self proteins.
Present of neutrophils macrophages and dendritic cells.
IL 4 & 5 job?
Activate B cells to produce antibodies
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.
What can T helper cells further be divided into?
Th1 and Th2
Big cytokine producers
What kind of domains do Fc regions contain?
Infliximab, does the antibody target and bind to receptor or ligand to stop ligand binding?
2 light chains of antibodies can be what classes?
Kappa and lambda
These are the classes of the light chains constant region.
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
Must abundant type of WBC?
Small so they can easily enter tissues
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.
Does the receptors involve in the immune response affinity for AG increase or decrease during the response?
What is the name of the components of a compliment system?
What cytokine promotes Th2 production but inhibits Th1?
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.
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!!
What is the adaptive immune system triggered by?
The innate immune system
Lipopolysaccharides are also known as....
What are heavy and light chains bound togetherby?
The small part of an antigen that an antibody/ T cell receptor recognises is the _____
Antibodies have different specificifities for different epitopes
One antigen lots of different epitopes= (a polyclonal) as lots of diff ABs respond
What does ADEPT stand for?
Antibody directed enzyme prodrug therapy.
What does excessive LPS stimulation cause?
Systemic inflammatory response syndrome (fever, septic shock, too much inflammation)
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
What do peritoneal lymphocytes secrete antibodies against?
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
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
How many ABs do plasma B cells usually hold?
What are lymph nodes classed as?
Secondary lymphoid organs
Once B and T cells are mature but naive, they migrate to the lymph nodes
Do T cell receptors have high affinity or low affinity for antigens?
That's why T cells have to be presents antigens by antigen presenting cells.
What do TNFa , IL-1, E-selectin, and iNos result in?
Enhance white blood cell movement from blood to tissue to create inflammation
What can bind to 7 alpha helical transmembrane receptors?
N formyl methyl peptides (bacterial peptides)
What are antigens recognised by on T cells and B cells?
TCRs on T cells ( T cell receptors)
Antibodies on B cells
Which immune system are pattern recognition receptors and LPS involved in?
Innate immune system
How do IgG and IgM trigger complement activation?
By binding C1q
What are IgE antibodies for?
For targeting parasites and immediate hypersensitivity (allergeeeee reactions= E)
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.
Where does the Fc region of IgG antibodies bind? What does this promote?
To Fc receptors on surfaces of neutrophils and macrophages.
Both AB and AG are destroyed.
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!
What cells recognise class I MHCs?
CD8 cytotoxic T cells
Presented on virally infected cells
What do activated Tc cells target?
Tc cells kill virally infected cells by apoptosis
TGF beta job?
Acts to dampen the immune system and restore homeostasis (Like Treg cells)
What cells recognise MHC class II?
CD4 T helper cells
Th1 and Th2
What do naive T cells (mature T cells that haven't yet encountered an ANTIGEN ) posses? CD__
T helper cells surface molecule is___
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.
Which has a smaller antigen binding groove, class I or class II MHC?
Class I has a smaller
class II has a larger
3 ways the complement cascade can be activated?
What effect does the complement C5a have?
It is chemotactic for neutrophils (WBCs)
Draws them out of blood into tissues of infected site
2 proinflammatory cytokines to remember;
IL1 (interleukin 1)
These enhance Inflammatory response by drawing WBC's out blood Into tissue to fight the antigen.
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
Classical pathway of complement cascade involves.....
C1 detects an ANTIBODY bound to the microbe
Then it cleaves C2/C4 starts the cascade...
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
What do B and T cells become on activation? ____ ___
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.
What cells act as APCs?
Dendritic cells (main type)
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
What can heamopoeitic stem cells form?
RBC's, myeloid cells, lymphocytes
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.
Cytotoxic T cells surface molecule is___
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.
What are T cell receptors associated with on T cell surfaces?
CD3 signalling chains
Features of macrophages?
Lots of organelles
Help with antigen presentation
Where are the hypervariable regions located?
They protrude into the antigen binding groove.
What does Fc region stand for?
Fragment crystallisable region.
When activated, T cells swell in size. We call this _____
What triggers Ig class switching?
Activation of a B cell
What are both natural killer cells and dendritic cells?
Interfere with viral reproduction
What kinds of things can you attach to an antibody to target an antigen?
What anti-inflammatory cytokines do T regulatory cells secrete?
What inhibits signalling on surface of the B cell?
Binding to Fc region of an antibody
What antibody class are produced on first antigen encounter?
What are these for?
For complement activation
These are natural ABs in the lining of the abdominal cavity(peritoneum)
Remember IgM= complEMent activation
All 4 cells of the innate system use______ receptors. What are these 4 cells?
Pattern recognition receptors.
Macrophages, neutrophils, dendritic cells, natural killer cells
What happens if a CDR undergoes a mutation?
Changes the affinity of an antibody for an antigen
What are LPS a product of/ found in?
Cell walls of gram NEGATIVE bacteria
What are complemtary determining regions?
3 regions within variable gene segments with highly variable amino acid sequences.
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
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
As a B cell matures, what class does it change from the starting IgM class to?
M N O P.... alphabet.....
Macrophages and neutrophils ..... Phagocytosis!
What are hypervariable regions particularly susceptible to?
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
Features of dendritic cells?
Membrane protrusions; engulf antigens
What does IL-2 stimulate?
Growth factor of T cells, increases their number
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.
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.
How much of plasma proteins do antibodies take up?
Which G protein subunits are the ephindrine and acetylcholine receptors coupled to?
Ephindrine= Gs, increasing cAMP
Acetylcholine (muscarinic) = Gi, decreasing cAMP
Where are nuclear receptors located?
Inside the cell. They are intracellular. Not in nucleus but in cytoplasm.
How do you measure the activity of an ion channel?
Use patch clamp recordings
Is Ras attached to the cell membrane? By what
Yes by a covalently attached lipid
What is direct cell-cell signalling?
Receptor on surface of one cell detects ligand on surface of other cell. Cells physically connect.
What is the job of Arf?
Regulates vesicular trafficking and activated phospholipase D. Remember Arf= vesiculARf trARFficking!!!!
IP3 is short for...
Inositol 1,4,5 triphosphate
Example of a death receptor?
Fas protein binds to a Fas ligand on a killer lymphocyte cell
How many phosphate groups does adenylyl cyclase remove from ATP?
2 , forming a mono phosphate cAMP
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)
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
What are class II PI3Ks activated by?
Receptor tyrosine kinases
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
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
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.
Why is negative feedback in cell signalling important?
If you can't turn a signal off it may result in a tumour forming.
What is autocrine cell signalling?
Cell signals to ITSELF. the molecule released acts back on itself.
What do Bad and Bax have in common?
Both promote cell death
What is the ultimate response of the Ach signal binding to ACh receptors?
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.
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
What is the class II PI3Ks structure like?
A single p110- like catalytic subunit
Called either PI3KC2alpha ,PI3KC2beta. ,PI3KC2gamma
What switches Ras on and off?
GEF (SOS protein) switches ON
GAP (activating GTPase) switches it OFF
What refills calcium stores in the muscle cell?
Ca2+ ATPase called SERCA
How many amino acids is the pleckstrin homology domain made of?
This domain allows docking of proteins to plasmamembranes
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.
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.
How does PKB associate to the cell membrane?
Phosphorylation of membrane lipids
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!
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.
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.
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
How many caspases are there?
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
What is paracrine cell signalling?
Cell signals to a nearby neighbour by release of a molecule.
How many subunits is the acetyl choline receptor made up of?
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.
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.
Target molecule of the Gprotein in the CREB pathway? And the IP3 pathway?
cREB= adenylyl cyclase
iP3= phospho lipase C
What are PI3K's activated by?
By receptor tyrosine kinases (RTKs) and G protein coupled receptors
What does MAPK stand for?
Mitogen active protein kinase
This is a family of serine threonine protein kinases
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)
What is an IAP?
Inhibitor of apoptosis
Binds to some pro caspases to inhibit their activation
Binds to activated caspases to inhibit their activity
What do GTP/GDP do to the alpha subunit?
GTP ACTIVATES IT
GDP DEACTIVATES IT
What are integrins and cytokine receptors an example of?
Receptor linked protein kinases
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.
What 3 ligand gated ion channels associated with calcium can you think of?
ATP GATES P2X RECEPTORS
NDMA RECEPTORS (GLUTAMATE ION CHANNELS)
What does Tor do?
It's a large serine/threonine kinase activated by AKT.
It stimulates cells to grow by enhancing protein synthesis.
What are insulin receptors and EGF receptors an example of?
Receptor protein kinases
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
Once in cell, AM cleaved back off
Dye is now trapped in the cell.
Detects changes in cytosol [calcium]
What do mechanically gated ion channels do?
Open in response to mechanical movement of adjacent structures, respond to stretch and temperature.
What does the Gi subunit do to adenylyl cylase ?
Decreasing cAMP formation.
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.
What is the code for the catalytic domain in both class 1A and 1B PI3Ks?
This adds a phosphate group onto inositol phospholipids by 3 hydroxyl phosphorylation
What is the job of Raf?
It has a role in secretory and endocytotic pathways. Just remember this.
What does Bcl-2 do?
How is the acetyl choline receptor structure determined?
By crystallography experiments
What would you treat osteoarthritis , aplastic anaemia (RBC death) , myocardial infarction (heart cell death) and stroke (brain cell death) with?
Treat with caspase inhibitors!
What is the job of Rho?
Reorganises the cyto skeleton by serine threonine protein kinases. RhO ReOrganises!
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.
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.
What type of cell death is mediated by death receptors?
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
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.
What PI3K inhibitor drugs exist to prevent cancer?
Penicillin wortmannin- irreversibly binds
LY294002- reversibly binds
What is the pathway of cell signalling (4 stages)?
Signal, reception, transduction, response.
What receptor protein kinase is Ras linked up to?
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
What do class I PI3ks generate?
Is the ACh receptor heteromeric or homomeric?
Heteromeric, consists of different subunits
Where is the death domain of a death receptor?
In its cytoplasmic tail.
What is used to treat HER2 associated cancer ?
Herceptin (monoclonal antibody treatment) interferes with the HER2 receptor.
What's the catalytic domain of class III PI3Ks called?
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
What is endocrine cell signalling?
Uses hormone transported in blood to send messages throughout the body.
What does Bad do?
Binds and inhibits death- inhibiting proteins like Bcl2
When active it binds to and inactivates these death-inhibitory proteins
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.
How many cells are Eliminated from the body everyday?
10 billion cells.
Shedding intestinal lining,
Turnover of tissues
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
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.
Example of a member of the EF hand family?
Has 4 Ca2+ binding sites in its loop domain
Targets calcium dependent protein kinases
And targets plasma membrane Ca2+ATPase pump
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.
What is the job of Ran?
Transport of RNA and proteins into and out of nucleus. Remember RAN= RNA. Transport = run/ ran.
3 domains of the nuclear receptor superfamily?
Transcription activation (gene transcription)
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.
What are the 2 phosphoinositide3-kinases (PI3Ks)??
they both use ATP as the phosphate source
What is the EF hand?
A helix - loop- helix structural domain found in a large family of calcium binding proteins.
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.
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.
Another name for ligand gated ion channels?
What does PI3K's stand for
Phosphoinositide 3 kinases
They ADD A PHOSPHATE GROUP onto inositol phospholipids
What is extrinsic apoptosis mediated by?
Not part of cells nature
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)
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.
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.
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.
How is the IP3 signal terminated?
By phosphatases (enzymes) or by further phosphorylation forming inositol 1,3,4,5 tetrakisphosphate.
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)!!!
Which 3 amino acids present of proteins can phosphates be added to by Kinase enzymes?
Tyrosine, threonine, serine
What does Bax do?
Promotes cell death by inducing cytochrome C release from mitochondria
Which G alpha subunits target adenylate cyclase?
Which target phospho lipase C?
Adenylate cyclase=Gi and Gs
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
4 examples of ligands for ligand gated ion channels?
NDMA, Glycine, GABA, Ach
Where are ligand gated ion channel receptors located?
The membrane of a cell. Occur in all cell types.
2 other names for g protein coupled receptors?
What receptors can activate phospho lipase C to increase cytosolic calcium?
Tyrosine kinase receptors, &
ACh binding to GpCRs
The permeability of ____ increases when Ach binds to the Ach receptor?
Na+ and K+ . This causes the membrane to depolarise carrying the action potential.
What family do death receptors belong to?
Tumour necrosis factor receptor family (TNFR)
Names of receptors:
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)
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
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.
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)
Basic definition of a receptor?
Receptors are proteins that bind to specific ligands/agonists.
Receptors have an affinity for the ligand.
What is AKT/PKB activated by?
Produced from activated PI3Ks
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)
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
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.
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!!
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.
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
Job of Ras?
Cell growth regulation via serine-threonine protein kinases. Activates a phosphorylation cascade.
When Bad is active , what does it encourage?
A cell to kill itself by apoptosis