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Membranes > Coyler > Flashcards

Coyler Flashcards

1
Q

What concentration is cAMP within a cell?

A

0.1-1uM

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2
Q

What are the physiological effects of cAMP?

A

Glucose metabolism from glycogen
Fight or flight response
Trigyceride breakdown

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3
Q

How many members of the adenlyl cyclase family are there?

A

6, with 50-92% identity

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4
Q

What is the structure of adenlyl cyclase?

A

2 NBD domains and 12TM helices

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5
Q

What is the turnover of AC?

A

1000/min

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6
Q

How does cAMP have localised effects?

A

APAK provides a platform to link targets and degradation close to AC

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7
Q

What is the main target of cAMP?

A

PKA

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8
Q

What are the targets of cAMP?

A

cAMP-dependant kinases,
Exchange Protein directly activated by cAMP,
ion channels

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9
Q

What are the sites of cAMP/ CaMK responses in muscle cells?

A

L-Calcium channels
RyR2 Calcium channels
Phospholambam

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10
Q

What enzyme does cAMP act on in muscle cells?

A

CamK11

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11
Q

How is cAMP degraded?

A

Phosphodiesterases

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12
Q

What structure is PDE?

A

58-125kDa, regulatory and targetting domains with catalytic core

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13
Q

How many forms of PDE are there?

A

11 classes, 30 isoforms

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14
Q

What is the structure of PKA?

A

Dimer of R/C
R is autoinhibitory by mimicking substrate, released by fast/slow cAMP sites
C has MgATP site and substrate binding site

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15
Q

What specificity does PKA have?

A

Low specificity for S/T in RRxSxxxx motif

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16
Q

What deterrents does PKA specificity have?

A

Y at 0
F at +4
Acidic residues at -1
K at -1

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17
Q

How is cAMP signalling restricted?

A 
PDE degradation
AKAP compartmentalisation
Phosphatases counteracting downstream targets
GPCR/GP inactive form
Internalisation of GPCR
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18
Q

How is Adenlyl cyclase activated?

A

By GPCR stimulation, varying from which GP subunit

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19
Q

Is the [cAMP] uniform across a cell?

A

No-heterogeneous/localised

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20
Q

Which pathogens expliot cAMP signalling?

A

Cholera ADP-ribosylates Gas for permanent inactivation

Pertussis injects soluble AC

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21
Q

Which receptors are activated by cAMP in heart?

A

B1-AR and B2-AR

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22
Q

Which heart receptor have the most significant increase in contractility?

A

400% in B1-AR

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23
Q

Which heart receptor is cardioprotective?

A

B2-AR

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24
Q

What are the effects of overstimulation of PKA?

A

desensititation

25
Q

How does EPac respond to high stimulation?

A

desensitised

26
Q

Which cAMP target has a switch in activity when overactivated?

A

CaMK11 switches from contractility to apoptosis

27
Q

What effect does GPCR phosphorylation have on a cell?

A

Cell growth/hypertrophy.

28
Q

What is IP3?

A

inositol-1,4,5-triphosphate

29
Q

What percentage of the membrane is PIs?

A

2-8%

30
Q

Which 2 pathways can stimulate PLC activity?

A

PTK or GPCR

31
Q

How are GPCRs activated for IP3 signalling?

A

Ach, 5HT, odour, light

32
Q

Which PLC isoform do RTKs activate?

A

PLCy phosphorylation at Y771, Y783, Y1254

33
Q

Which G proteins are involved in activating PLCs?

A

q, By, 11, 14, 16

34
Q

Which PLC isoform does Gaq activate?

A

beta 1

35
Q

How is PLCy inhibited?

A

PKA and PKC phosphorylation

36
Q

What physiological effects does IP3 have directly?

A

fertilisation,
platelet aggregation
secretion from the adrenal cortex
smooth muscle contraction

37
Q

What does DAG activate?

A

Ca-dependant kinases

38
Q

What does PLC produce?

A

IP3 and DAG

39
Q

How does IP3 mediate release of Ca?

A

Opens ligand gated Ca channels in ER

40
Q

Where is the intracellular store of Ca?

A

In the ER, maintained by SERCA pump and buffer proteins calreticulin and calsequestrin

41
Q

What is the structure of the IP3R?

A

tetrameric channel with 3 isoforms of 2701-2745 residues

42
Q

How is IP3R regulated?

A

Cytosolic [Ca}
ATP
PKA phosphorylation

43
Q

What is the Kd of IP3 for the IP3R?

A

10nM

44
Q

What is the [intracellular Ca]?

A

0.1-1uM

45
Q

What is the [Ca] in the blood?

A

1-2mM

46
Q

How can [cytosolic Ca] be observed?

A

photoproteins based on aequorin

EGTA derived organic dyes that use acidic groups for chelation

47
Q

How much Ca can be released in cytoplasm?

A

Quantal/fixed

48
Q

How does Ca release vary with increasing [agonist]?

A

frequency of release varies

49
Q

What is the capacitive Ca entry?

A

Quantal release of Ca from ER
Decline
Opening of blood channels
Increase in Ca

50
Q

How does Ca enter cells from blood?

A

Low Ca causes Orai to release TRPC as open non-specific cation channel
Orai binds STIM in ER membrane
Clusters of complex lock TRPC in Ca form (Icrac form)

51
Q

What direct effects does Ca have an a cell?

A

channels, proteases and lipases,

eg TCA, PKC, PDE, contractile proteins

52
Q

Which regulatory proteins does Ca interact with?

A

calmodulin, annexins

53
Q

What is the structure of CaM?

A

16.8kDa

4 EF hands

54
Q

Where is CaM found?

A

Ubiquitous and abundant

55
Q

What processes in CaM involved in?

A

Ca transport
Glycogen metabolism
Cyclic nucleotide metabolism
Replaces troponin in smooth muscle contraction

56
Q

How is CaM activated?

A

conformational change buckles central helix
methionine puddle exposed
binding of substrate

57
Q

What motif does CaM target?

A

positive residues-hydrophobes

58
Q

How is CaM involved in neurotransmitter release?

A

CaMK11 releases synapsin on vesicles for interaction with actin cytoskeleton

Membranes (7 decks)

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