Week 2 Flashcards
(133 cards)
1
Q
Nav and Kv ion channel basic structure
A
-4 membrane spanning domains
- Kv domains are separate polypeptides
- Nav, Cav domains are linked together as 4 repeats (I, II, III, IV) making one large polypeptide domain
- Each domain contains 6 a-helices
2
Q
Function of S4 helices in Kv and Nav ion channels
A
Sense voltage
4 per channel
-Positively charged residue (lys or arg) present at every third position
3
Q
Function of S5 and S6 helices + connecting P loop
A
Form ion conducting pathway and selectivity filter
4
Q
Principles of channel selectivity (5)
A
1) Selectivity Varies
2) Charge/Ionic Valence
3) Size
4) Dehydration
5) Multiple binding sites can increase selectivity
5
Q
Dehydration
A
- Ions must be dehydrated before passing through channel pore
- Dehydrated ions are unstable
- Ions stabilized within the pore via interactions with AA of pore
6
Q
Kv ion channel has an _________ gate that opens when the cell is ______, and closes when the cell is _________
A
Activation gate
closed when cell is (-) - current is zero = DEACTIVATION
opened when cell is (+) - allows K+ to flow out of cell = ACTIVATION
7
Q
Selectivity of the activation gate present in Kv and Nav depends on voltage sensing from ______ and ion conducting pathway from ______. ______ allows gate to have hinge-like motion
A
S4 helices
S5 and S6 helices
S6 segment conserved glycine
8
Q
Nav ion channel has a ________ and ________ gate
A
Activation
Inactivation
9
Q
Nav activation gate is _______ when cell is (-), and ______ when cell is (+)
A
closed = DEACTIVATION
open (allows Na+ to flow in) = ACTIVATION
10
Q
Nav Inactivation gate is ______ and resting potential
A
open
11
Q
closed Nav activation gate blocks _________, but once the activation gate opens, _________ is revealed and then ____________
A
inactivation site
receptor site inside pore
inactivation gate can swing closed = INACTIVATION
12
Q
Inactivation gate selectivity is determined by the __________. The channel is closed when this folds over inner end of central ion-conducting pathway.
A
cytoplasmic loop connecting repeats III and IV
13
Q
Sidedness of Ion channels means that _____________. This may require that ________ which is known as __________
A
modifying reagents have access to sites of action only from one side of the membrane
May require than channel be open = State-dependence
14
Q
TTX
A
Illustrates Sidedness
cannot cross membrane, only binds extracellular pore entrance – not effective when intracellular
15
Q
Lidocaine
A
Illustrates State-dependence/sidedness
Protonated form: + charge, acts intracellularly
-blocks channel only when activation and inactivation gates are open
Deprotonated form: neutral charge, can cross membrane
16
Q
Na+, Cl-, and water leak into epithelia on _______ side (down electrochemical gradient), and ______ pump on ________ side pumps Na+ out, Cl- follows, and water follows drawn by osmotic gradient
A
apical
Na/K
basolateral
17
Q
Apical side faces the ______, while the basolateral side faces the ________
A
lumen
interstitium
18
Q
Another way NaCl can get across the membrane is by ____________
A
leaking across the epithelium through leaky tight junctions
19
Q
Another way NaCl can get across the membrane is by using the ____________ cotransporter located on the ________ side of epithelium and then the leak of Cl- across on the __________ side
A
Na+/2Cl-/K+ (electroneutral) on basolateral side
apical side, drags Na+ and water with it
20
Q
Glucose and AA absorbed into the blood by….
A
Nutrients pumped across apical membrane (Na+/AA or glucose) and then move passively out of cell on basolateral side into interstitial fluid
21
Q
Leaky epithelia are typically present in epithelia that _____________
A
engage in massive transport of substances
small/large intestine, gall bladder, proximal kidney tubules
22
Q
________ pumps Cl- into the cell by using energy from ______. This is on the ________ side.
A
Na/K/2Cl
Na+ leakage into the cell
basolateral side
23
Q
The Chloride channel is located on the ______ side of the epithelium. At rest the channel is closed but when open, it allows ______________
A
apical
allows Cl-, water, electrolytes to leak out of the cell into lumen
24
Q
Cl- channel:
Cholera –> ?
Cystic Fibrosis –> ?
A
Cholera = locks Cl- channel open, severe fluid loss
Cystic fibrosis = mutated channel, prevents epithelial secretion of serous (watery fluid)
25
_______, _______, ______, ______ are never pumped across membranes, but ALWAYS ____________
Water, O2, CO2, and urea
move passively down their concentration gradients
26
CO2 is a ______ substance, that is excreted by the _______. It makes up 14.5/15 moles of waste produced from each cell.
volatile
lungs
27
Urea is a ______ metabolic waste produce that it secreted by the ________
non-volatile
kidneys
28
Absorption in the GI tract is...
It plays a _______ role in excreting non-volatile metabolic wastes and regulating ECF composition
- not regulated by ECF composition
- Geared for maximum transport of nutrients at any time regardless of the needs of the ECF
MINIMAL role
29
Kidneys play a ______ role in excreting non-volatile metabolic wastes and regulating ECF composition.
EXTENSIVE role
30
Absorption in the kidneys
"I know what I like"
-Kidneys create an ultrafiltrate of plasma in glomerulus (contains water, salts, sugars, AA, and other beneficial compounds as well as non-volatile metabolic waste)
- Plasma ultrafiltrate passes along renal tubules where all the stuff the kidneys want gets reabsorbed and waste is allowed to pass on
- VERY energetically expensive
31
Action Potential:
1) Resting Potential
- Na+ channel: activation gate closed, inactivation gate open
- Permeability Na = 0
32
Action Potential:
2) Depolarization
- Na+ channel: activation gate open, inactivation gate open
- Maximum Na+ current during rising phase
- Positive feedback: Na+ flowing in makes more Na+ channels open → cell depolarized (more +)
- Once threshold is reached = all or nothing
33
Action Potential:
3) Peak
- Na+ channel: inactivation gate slams shut (delayed), activation gate remains open
- Permeability Na = 0
- Vm is close to equilibrium potential of Na so Na+ current low
34
Action Potential:
4) Repolarization
- Na+ Channel: inactivation gate
| - K+ Channel: gate opens with depolarization, but is slow to open → K+ rushes out of cell
35
Action Potential:
5) Hyperpolarization
- Na+ Channel: inactivation gates closed, activation gate closed (inactivation gates will start to re-open as cell returns
- K+ Channel: cell undershoots resting potential because the K+ channel is delayed in closing
36
K+ channel acts to...
- Speeds up repolarization → more AP in given time
| - Negative feedback: depolarization causes K+ channels to open → repolarization → channels close
37
Intracellular concentrations of Na+ and K+ do not change much after a single AP because...
the number of ions that flow in and out is negligible compared to the total number of ions
38
Role of Na/K pump in AP
-Restores the concentrations of Na+ and K+ → Recharges the battery
39
Booster Stations:
______ acts as the energy source, while ______ acts as the detector
Na+
Voltage gated Na+ channel
40
Absolute refractory period
no stimulus, no matter how strong, can evoke another AP
41
Relative Refractory Period
stronger-than-normal stimulus is required to evoke another AP
42
Why is there a refractory period after each AP?
- Permeability to Na+ very low, Na+ channel inactivation gates require time to reopen after repolarization
- Permeability to K+ still high, K+ channels take time to close again
43
Accommodation of the AP
- if an axon is depolarized slowly, may fail to generate an
| - Axon accommodates to the slow, steady stimulus
44
Mechanism of Accommodation?
Hyperkalemia?
- Slow depolarization allows time for inactivation gates of Na+ channels to close before activation channels open
- Part of why Hyperkalemia is so dangerous! There is time for some Na+ channel inactivation gates to close
45
Threshold for AP
point at which Na+ flow into cell = K+ flow out of cell
46
Positive feedback nature of rising action phase in AP
Na+ flowing in makes more Na+ channels open = positive feedback during rising phase of the action potential
47
Safety Factor
- density of Na channels in a patch of membrane required to generate enough Na current for an AP to propagate
- We have 5-10 times the necessary number of Na+ channels
48
Benefit of having 5-10 times safety factor? (2)
- Get a shorter refractory period with more Na+ channels re-opening their inactivation gates sooner
- Need sufficient current to depolarize even when axon has branches
49
Myelin acts to increase __________ and decrease ________
electrical resistance between inside of axon and ECF
capacitance
50
Node of Ranvier
naked region without myelin
-Site where AP is propagated, where Na+ channels are
51
Saltatory Conduction
AP spreads from node to node
52
Small Diameter axons:
- High threshold to external stimulation
- Lower conduction velocity
- Lower safety factor
53
Big diameter axons:
- Low threshold to external stimulation
- Fast conduction velocity
- Higher safety factor
- Have myelin = conduction velocity directly proportional to diameter
54
Acutre hyperkalemia occurs when ___________. This can disrupt _________
K+ escapes rapidly from cells, elevated extracellular K+ depolarizes cell
disrupts rhythm of heart
55
CBIGK = treatment for _________
Ca, Bicarb, Insulin, Glucose, Kayexalate
hyperkalemia
56
Ca2+ can be used as a treatment for hyperkalemia by...
-Ca2+ can be used to silence “Maverick” pacemakers and restore normal synchronous pattern of excitation/contraction
- Ca2+ ions bind to fixed negative charges on outside surface of cells
- Trick Na+ channels into thinking the membrane has been hyperpolarized → raises threshold for AP initiation
- Stabilizes activation gates
57
_____________ is the initial stage of MS, while ___________ is the final stage of MS progression
relapsing-remitting
Secondary progressive
58
Consequences of demyelination : (3)
1) changes in resting potential and action potentials (harder to depolarize cell due to constant leak of K+ out of cell)
2) decreased speed of conduction in nerves (proliferation of Na+ channels along axon = more Na+ entry into cell, slowing nerve conduction)
3) MS patients must recruit more neurons to do the same function (brain reserve)
59
Therapies for MS include blockers of ______ and ________. Many other therapies target __________
Na+ and K+ channels
immune system
60
Dalfampridine
K+ channel blockade
Improves walking speed in patients with MS
Enhances conduction of AP in demyelinated axons through inhibition of K+ channels (prevents K+ leak and restores resting potential)
61
Structure of Nuclear Pore Complex (NPC)
| 3 subcomplexes
Large macromolecule within the nuclear envelope
-made up of 30-50 distinct proteins (Nucleoporins - Nups) arranged repetitively in distinct sub complexes (Integral, Scaffold, and barrier Nups)
62
Integral Nups
fused to form a luminal ring within the nuclear envelope, anchoring NPC in nuclear envelope
63
Scaffolding layer n=Nups
provide framework for adding barrier layer
| both cytoplasmic and nuclear filaments
64
Cytoplasm scaffold filaments vs. nuclear scaffold fialments
Cytoplasm - free to extend into cytoplasm
Nuclear - form a basket layer that plays role in chromatin organization/gene expression
65
Barrier layer Nups
natively unfolded proteins that line NPC channel with hydrophobic FG (phenylalanine, glycine) Nups (repeats) whose interactions form a selectivity filter
-Creates an entropic barrier or virtual gate that only certain proteins can pass through
66
Types of Cargo Complexes:
1) Karyopherins
2) NTF2
3) NXF1/NXT1
67
Karyopherins
-Receptor Family vs. Adapters
aka importins/exportins
Receptor family: interacts directly with cargo and FG Nups
-EX) Karyopherin Beta
Adapters: have binding sites for specific cargos and receptor family karyopherins (whole complex is transported)
EX) Karyopherin alpha
68
NTF2
specific transporter for Ran.GDP into nucleus
69
NXF1/NXT1
transporters of mRNA and rRNA
70
Ran
Determines directionality of transport
71
Ran.GTP interacts with _________ and promotes _________ or _________
Karyopherin/cargo complex
-promote dissociation (import) or stabilize complex formation (export)
72
3 mechanisms for nuclear import and export
1) size-filtering diffusion
2) spontaneous migration
3) facilitated transport
73
Size-filtering diffusion nuclear import/export
- allows passage of small hydrophilic molecules (20-30kD size cut off)
- Water, ions, small molecules
74
Spontaneous Migration nuclear import/export
- allows passage of amphiphilic molecules that can overcome hydrophobic barrier
- Occurs via rapid association/dissociation from hydrophobic FG nups
- Cannot move substances against concentration gradient
- Includes karyopherins, B-catenin, SR-proteins
75
Facilitated transport in nuclear import/export
- passage of “cargo” (hydrophilic) by carriers (amphiphilic)
- Can transport against concentration gradient
- Requires energy coupled dissociation
76
NLS (Nuclear Localization Signal) / NES (Nuclear Export Signal)
```
NLS = transport in
NES = transport out
```
NLS/NES must be on cell surface
Not cleaved during transport --> Can be reused!
77
Facilitated IMPORT of proteins/snRNPs through NPc:
1) Cargo + NLS bind in ______→ ____________ → brought into _________
2) Ran.GTP binds to ________ → ________________
3) __________ brought back into cytoplasm
4) Ran.GTP hydrolyzed to _______ and ____________
1) Cargo + NLS binds in cytoplasm → binds transporter → brought into nucleus
2) Ran.GTP binds to transporter → conformational change allows cargo to be released
3) Transporter + Ran.GTP brought back into cytoplasm
4) Ran.GTP hydrolyzed to Ran.GDP and released from transporter
78
Facilitated EXPORT of proteins/snRNPs through NPC:
1) Cargo + ______ bound and Transporter + ________ bound
2) Cargo + NES binds to __________ → __________
3) ________ hydrolyzed in cytoplasm causing ___________
4) _________ spontaneously recycles back into nucleus
5) _______ special transporter binds 2 Ran.GDP molecules and _______________
6) Ran.GDP --> __________
1) Cargo + NES bound and Transporter + Ran.GTP bound in nucleus
2) Cargo + NES binds to transporter + Ran.GTP → transport out of nucleus
3) Ran.GTP hydrolyzed in cytoplasm separating pieces
4) Transporter spontaneously recycles back into nucleus
5) NTF2 special transporter binds 2 Ran.GDP molecules and carries them back into the nucleus
6) Ran.GDP → Ran.GTP
79
Facilitated export of mRNAs through the NPC:
Coupled to __________
performed by _________ transporters
RNA is remodeled by ___________ on the cytoplasmic face
_____________ are needed to unravel nascent mRNA to allow binding of transporters
coupled to remodeling of RNA
- NXF1/NXT1 transporters bind mRNA and rRNA (rate limiting step) in nucleus and transports it out into cytoplasm
- RNA is remodeled by cytoplasmic Rnbp at cytoplasmic face
- ATP dependent helicases needed to unravel nascent mRNA to allow binding of transporters
80
4 things that regulate nuclear import and export:
1) Entropy (hydorphobic) barrier created by barrier Nups
2) Presence of Ran.GTP/GDP gradient
3) Interaction of cargo transporters with nucleoporins
4) composition of cargo impacts association with transport receptors
81
Ran.GDP/GTP gradient controls nuclear import and export because...
- High Ran.GTP in nucleus
| - Hydrolysis of Ran.GTP → GDP only in cytoplasm and GDP --> GTP only in nucleus
82
Cargo composition can be changed in 4 ways, impacting association with nuclear tansport receptors
1) Conformational change with ligand binding
2) Covalent modification of cargo molecule
3) Sequestration by binding partners (in nucleus of cytoplasm)
4) Binding/dissociation or regulatory subunits that either mask or provide signals
83
3 mechanisms of protein transport
1) Gated Transport: between cytosol and the nucleus (Nuclear Transport)
2) Transmembrane Transport: across a membrane from the cytosol into an organelle through translocators
- EX) protein synthesis and mitochondrial import
3) Vesicular Transport: in which membrane bound transport intermediates move proteins and lipids from one compartment to another
84
6 major functions of the ER
1) Synthesis of lipids
2) Control of cholesterol homeostasis (Cholesterol sensor and synthesis)
3) Storage of Ca2+ (Rapid uptake and release)
4) Synthesis of proteins on membrane bound ribosomes (Rough ER)
5) Co-translational folding of proteins and early posttranslational modifications
6) Quality control
85
4 major functions of the golgi
1) Synthesis of complex sphingolpids from the ceramide backbone
2) Additional post-translational modifications of proteins/lipids
(Most notably glycosylation and sulfation)
3) Proteolytic processing
4) Sorting proteins and lipids for post-Golgi compartments
86
Golgi broken up into different compartments including _____, _____, ______, and _____. In these different compartments there are ___________
cis (closest to ER), medial, tans, trans golgi network
different enzymes doing different functions in each area
87
The tans golgi network is where ________ and ________ occurs
- sulfation
| - Vesicles bud from and are sorted to their correct destination
88
Constitutive vesicles vs. regulated vesicles
- Constitutive Vesicles: secreted right away
| - Regulated Vesicles: secreted only when the proper signal is received
89
Three vesicle coats
1) COP II
2) COPI
3) Clathrin
90
COPII
ER to Golgi
91
COPI
Golgi to ER
backward, allows recycling of proteins
92
Clathrin
Trans Golgi to plasma membrane (also does endocytosis)
93
Vesicular transport involves the movement of _________ via _________, ________, and __________.
Specific AA motifs on the cytosolic side of _________ are recognized by _________ for __________
movement of cargo and membrane proteins
- budding of vesicles
- fusion of some vesicles into tubules
- fusion of vesicles/tubules with the next compartment
Membrane proteins
adaptor proteins
recruitment into vesicles
94
ER signal sequence
On cargo proteins or transmembrane proteins
- on newly formed polypeptide chain at N-terminus
- directs engaged ribosome to ER membrane
95
Signal Recognition Particle (SRP) structure and function
Structure:
- 6 proteins + 1 RNA
- Flexible binding pocket (can bind variety of signal sequences)
Function:
-Binds nascent polypeptide and ribosome, pausing translation until it also binds SRP receptor (on ER)
96
Translocon structure and function
-protein channel, allows polypeptide chain to enter ER
Structure:
-3 protein complex, forms an aqueous pore that is closed unless a protein is coming through
Function:
-Allows protein to be fed from outside of ER to inside ER lumen as it is made
97
6 Steps for Cargo Protein synthesis
1) ER signal sequence on very beginning of N-terminus of polypeptide chain
2) SRP binds signal sequence and brings it to ER
3) SRP binds SRP receptor on ER and protein begins to be fed through translocon into ER
4) signal peptidase clips off signal sequence
5) Cargo protein done getting synthesized, ribosome falls off
6) protein gets folded and sits inside ER lumen
98
Type 1 Transmembrane protein
amino termins in ER, carboxy out
1 transmembrane domain
99
Stop-Transfer signal
- on mRNA, sequence recognized by translocon, translocon releases this sequence
- The rest of the protein (C-terminal end) made in cytosol
100
Type 2 Transmembrane protein
- amino outside of ER, carboxy in
- 1 transmembrane domain
- (+) charged AA on amino side of the TMD orient amino end to the cytosol
101
N-linked glycosylation occurs in the ________. It is the process of __________ that functions to __________ and __________.
Lumen of ER
Adding preformed carbohydrate complex to asparagine (N) to polypeptide
Function:
- Keep proteins from aggregating when hydrophobic domains are exposed
- Glucose on complex acts as tag to monitor unfolded proteins (determines if they are properly folded or not)
102
Clinical features of Vibrio Cholerae infections: (5)
1) only infects humans
2) incubation 18 hours - 5 days
3) can have asymptomatic cholera (majority of people infected are asymptomatic)
4) Severe, acute, rapidly fatal watery diarrhea (non-inflammatory
5) both epidemic and pandemic
103
________ is the cause of death with cholera
DEHYDRATION
104
________ distinguishes between V. Cholerae Strains
> 200 serogroups based on O-Specific polysacchardie (OPS) of LPS
105
___________ and _________ both protect against cholera disease infection
Prior immunity (recent exposure, you get less sick)
Having one mutant cystic fibrosis gene (CFTR) because cholera toxin isn't able to constitutively opne Cl- channel
106
Treatment of cholera is with ____________
oral rehydration fluids with glucose, which enhances sodium and electrolyte reuptake
107
Two major routes for endocytosis
1) Phagocytosis
| 2) Pinocytosis
108
Phagocytosis
- Macrophages and neutrophils in blood
- Recognize foreign organisms, engulf them, and deliver them to lysosomes for degradation
- Recognize apoptotic cells
109
Pinocytosis, two major routes
(small vesicle formation)
-Involves small volumes – specific uptake of ligands and receptors
1) Clathrin Coat Proteins
2) Caveolae
110
Clathrin coat proteins
endocytic vesicle coat that forms on a vesicle budding from the plasma membrane
111
Pinocytosis via clathrin coat protein steps:
1) cargo molecule binds transmembrane receptor
2) Adapter protein binds short motif on cytoplasmic domain of receptor
3) Adapter complex of proteins forms on intracellular side and clathrin coat assembles on budding vesicle
4) Dynamin pinches vesicle off membrane
5) adaptor complex and clathrin dissociate from vesicle inside cell
112
Caveolae
- endocytic vesicles that form without coat proteins
- important in lipid raft regions and used by some animal viruses and cholera to enter cell
- Made up of 114 calveolin (structural proteins)
113
Quality control of protein synthesis in the ER is ensured by...
- folding enzymes that recognize if a protein is folded properly via glucose tail from N-linked polyoligosaccharide
- glucosidase II adds glucose to protein if it is improperly folded, and funneled back into system to get refolded
- if folding is bad and can't be fixed --> proteosome
114
hsp70
- Made in high abundance when cell is hear shocked
| - Binds exposed hydrophobic patches in incompletely folded proteins and prevents aggregation
115
hsp60
- Large, barrel-shaped structure with chamber
- Feeds misfolded proteins into chamber and helps it fold
- uses ATP
116
Ubiquination-Proteasome System (UPS)
- responsible for rapid degradation of proteins when fast adaptation is needed
- 4 molecule ubiquitin tag sends protein to proteosome
117
Ubiquitin molecules
- attached to proteins by E1, E2 and E3 ligase enzymes as they leave the ER --> 4 (polyubiquitins) target protein to proteosome
- ubiquitin molecules cut off by proteosome and recycled
-mono and multiubiquitins used as regulatory signals instead of degradation signals
118
Proteosome
huge complex of proteins, unwinds misfolded protein and feeds protein strand into a compartment that cuts the protein into short 7-9 AA peptides
-Dispersed throughout cytoplasm
119
Proteosome structure:
Cap
Cylinder
Alpha Subunits
Beta Subunits
Cylinder: where proteolytic cleavage occurs
Cap: recognizes polyubiquitin, uses ATP to unfold protein and feed it into cylinder
Alpha subunits – regulate substrate entry into “death chamber”
Beta subunits – do actually clipping of subunits
- B1 – cleaves after acidic AA
- B2 – cleaves after basic AA
- B5 – cleaves after hydrophobic AA
120
Lyososome
-Degrade extracellular materials taken up by endocytosis and some intracellular components
- Contain enzymes that degrade all classes of molecules – proteins, lipids and sugars
- Transporter in lysosomal membrane allow exit of AA, monosaccarhides, nucleotides, and lipids for reutilization within cell
- Proton pump makes lysosome lumen acidic (pH 5)
121
Macroautophagy
-Formation of a double membrane vesicle that captures cytosolic components/organelles → fuse with lysosome → hydrolases degrade contents of autophagosome
122
Function of macroautophagy
- Remove/recycle organelles, proteins, and other macromolecules
- Cell survival under stress conditions
- Neuro-protection
- Immune response and removal of intracellular pathogens
- Aging – (caloric restriction increases life span)
- Tumor suppression/promotion
- Regulates apoptosis/cell death (promote OR inhibit)
123
Chaperone-Mediated Autophagy
- Recognition of specific proteins that contain a specific recognition sequence (based on AA sequence KFERQ) → direct binding and delivery to lysosome
- Delivers specific proteins in a controlled manner to autophagosomes
124
Macroautophagy Process
1) Activate a PI3K complex that allows nucleation of a membrane that will eventually form the autophagosome.
2) Regulation of protein conjugation events to extend membrane.
3) Randomly capture or specifically deliver cargo to the extending autophagosome, then join the membrane to close the vesicle
4) Fuse with lysosome
5) Recycle amino acids and other macromolecular precursors.
125
Autophagy Protection against Neuro-degeneration
- Aggregate-prone proteins (e.g. Huntington’s) will cause neuronal cell death
- Autophagy degrades the aggregate-prone proteins → no toxic stimulus → not neuronal cell death
126
Apoptosis induction and autophagy
-Many proteins (e.g. Bcl-2) that regulate apoptosis (cell death) also control autophagy
→ problems for interpreting therapeutic interventions designed to target these proteins
-Apoptotic proteases (capases) can cleave essential autophagy regulators → inactivate them, and block autophagy
127
4 characteristics of apoptotic cells
1) Collapse of the nuclease, endonucleases chop up DNA between histones on linkers
2) Cell shrinks – loses 1/3 of volume in a few seconds
3) Cell tears itself apart into apoptotic bodies
• Plasma membrane still intact
4) Recognized by another cell and phagocytosed before dangerous pro-inflammatory contents spill out of cell
128
In a normal cell Phasphatidylserine (PS) all on _________ (maintained by ________)
In an apoptotic cell, PS becomes ____________ (done by __________)
_________ with PS receptors recognized, bind, and ingest cells that have committed to apoptotic pathway
Removal of apoptotic cells is ______________
inner leaflet of cell membrane, flippase
equal on both sides of the membrane, scramblase
Macrophages
physiologically silent
129
Tissues/cells with lots of apoptosis
Thymus – gets fully replaced every 3 days
Lymphocytes – 95-99% of lymphocytes that develop fail to be selected to mature as useful T cells
- Most radiation-sensitive cells – low-dose radiation does not kill lymphocytes, but induces them to kill themselves
- Die so easily because they are so dangerous due their rapid proliferation abilities
Morphogenetic death – important during development in determining the final shape of body parts and organs
130
Intrinsic Apoptosis
1) Perturbation of ___________
-Normally membrane guarded by _____________ protein family member (Bcl-2 and Bcl-XL)
__________ made and replace anti-apoptotic
→ Membrane permeable to ___________
2) __________ released into cytoplasm from mitochondria
3) cyt C activates _______ in cytoplasm
4) Apaf-1 activates ________ which activates _______ (proteases)
- Capase-9 = ?
- Capase-3 = ?
1) mitochondrial outer membrane function
anti-apoptotic Bcl-2
Pro-apoptotic Bcl
cytochrome C
2) cytochrome C
3) Apaf-1
4) capase-9, capase-3
```
capase-9 = signal capase
capase-3 = executioner, cleaves many substrates
```
131
Extrinsic Apoptosis:
1) __________ up-regulates expression of __________
2) Fas L activates _________ on cell surface
3) Fas (CD95) transduces signal, activates _________
4) FADD activates _______ which activates ________
1) Cytotoxik (killer) T cells (CTL), Fas Ligand surface molecule
2) Fas (CD95)
3) FADD
4) capase-8, capase-3
132
Continuum of response to damage
- First repair
- If repair is impossible of unwise, then apoptosis
- If damage is overwhelming, then necrosis
133
Autoimmune Lymphoproliferative Syndrome (ALPS)
failure of lymph cells to die
-new way of thinking about malignancy
