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Cell and molecular extras > Lecture 10 GPCR 2 > Flashcards

Lecture 10 GPCR 2 Flashcards

1
Q

How are lipid derived 2nd messengers generated

A

Membrane lipids are targeted by R-regulated lipases to generate 2 different 2nd messengers

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2
Q

What are the 2 most important 2nd messengers generated

A

(i) will be water soluble & diffuse through the cytoplasm eg. IP3
(ii) hydrophobic molecules, which remains in the membrane eg. DAG

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3
Q

How do lipid kinases work

A

add phosphate groups to lipids eg. To DAG to make phosphatidic acid , or to PI to generate PIP, PIP2, PIP3

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4
Q

What 3 enzymes work on PIP2 and what do they form

A

PLC –> breaks phosphodiester bond –> IP3 and DAG
PLD –> di-phosphate inositol and phosphatidic acid
PLA2 –> arachidonic acid

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5
Q

PIP2

A

Phosphatidylinositol 4,5-bisphosphate

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6
Q

What do the lipase enzymes also act on

A

PC (phosphatidylcholine) in same positions

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7
Q

What enzymes act on sphingomyelin

A

Ceramidase

Sphingomyelinase

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8
Q

What activates PLC

A

GaQ + Gbeta/gamma

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9
Q

What does PLC produce and what do these act on

A

DAG - activates PKC

IP3 - interacts with IP3R on ER to release Ca2+

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10
Q

What gives specificity in signalling

A

Selective expression and cellular localisation of signalling molecules

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11
Q

There are many isoforms of…

A

PKC

PLC

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12
Q

Which domain of PKC is conserved

A

XY catalytic

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13
Q

What type of kinase is PKC

A

Ser/Thr kinase

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14
Q

What is PKC structurally similar to

A

PKA

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15
Q

PKC interacts with DAG via what domain

A

C1

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16
Q

PKC interacts with Ca2+ via what domain

A

C2 - binds in the presence of a phospholipid

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17
Q

What drug mimics DAG

A

PMA - phorbol ester - used in research to activate PKC

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18
Q

What does GFP tagging of PKC show

A

PKC can be used to monitor the localized activation of the enzyme in real time.

Shows agonist (for Gq) -dependent translocation to the plasma membrane

Receptors may activate multiple isoforms of PKC to bring about a coordinated change in cell function

This is transient due to DAG breakdown by lipases

19
Q

How does DAG binding activate PKC

A

DAG binding causes dissociation of intramolecular pseudosubstrate domain from active site,

20
Q

Once activated what signalling does PKC provide

A

Once activated PKCs can provide either Positive or Negative feedback in signaling pathway

21
Q

What provides - signalling of PKC + what can this contribute to

A

Phosphorylation of PLCb provides negative feedback for GPCR signaling, makes signaling ‘transient’
Phosphorylation of receptors can contribute to desensitization

22
Q

Imaging of DAG regulated effector(s) revealed what

A

Activation of GqPCRs and synthesis of DAG in the PM, recruits Munc13 (a C1 domain containing protein) to the membrane

23
Q

Role of Munc 13

A

stimulates secretory vesicle docking to the PM, preparing it for fusion

24
Q

What doesn’t involve Munc13

A

PKC as other fucnitons e.g. ion channel reg

25
Q

PI synthesis is regulated by

A

many enzymes

26
Q

Mutation in what gene causes Lowe syndrome

A

OCRL - codes for an inositol polyphosphate 5 phosphatase alter PIP2 levels

27
Q

Lowe syndrome symptoms

A

glaucoma
kidney defect
mental retardation

28
Q

Name 5 processes regulated by calcium signaling

A 
Synaptic transmission
Hormone secretion & synthesis in some cases
Fertilization
Muscle contraction
Cytokenesis
29
Q

Concentration in IC calcium - how

A

In resting cells, cytosolic [Ca2+] is kept low (~100 nM) by ATP-driven Ca2+ pumps

30
Q

Receptors regulate the activity of Ca2+ channels to produce

A

transient rises in Ca2+

31
Q

Name proteins in the lumen of the ER bind up Ca2+ to allow for high concentrations to be stored, creating a large chemical gradient

A

Calsequestrin and calreticulin

32
Q

Striated muscle calcium pump, sequestering protein and release channel

A

SR Ca-ATPase
Calsequestrin
RyR

33
Q

Smooth muscle calcium pump, sequestering protein and release channel

A

Ca-ATPase
Calreticulin > Calsequestrin
IP3/RyR

34
Q

Non-muscle calcium pump, sequestering protein and release channel

A

One of 5 Ca-ATPase
Calreticulin > Calsequestrin
IP3/RyR

35
Q

What regulates calcium influx at PM into cytosol

A

voltage gated and ligand gated channels

36
Q

What regulates calcium influx at ER into cytosol

A

ligand gated channels

37
Q

Name 6 types of PM Ca2+ channels, where found, and what controlled by

A
  1. ATP-act channel - smooth muscle - EC ATP
  2. cAMP act channel - sperm - cytoplasmic cAMP
  3. L-type Ca2+ channel - skeletal, cardiac, brain, non - voltage
  4. N-type - neurones, endocrine - voltage
  5. P-type - purkinje neurons - voltage
  6. T-type - voltage, low threhhold
38
Q

ER Calcium channel gating is regulated by 2nd messengers - name these 4 channels and where found etc.

A
  1. IP3receptors- Most cells including brain and smooth muscle - IP3, Ca2+
  2. Type I ryanodine receptor - skeletal - DHP-receptor, Ca2+
  3. Type II RyR - cardiac - Ca2+, cyclic adenosine diphosphate (cADP)-ribose
  4. Type III - smooth muscle - Ca2+, cyclic adenosine diphosphate (cADP)-ribose
39
Q

Features of all RyR

A

Ca2+release stimulates contraction

40
Q

Information transfer is encoded

A

amplitude, duration and frequency of store-released calcium signaling

41
Q

Information transfer is translated by

A

calcium-binding proteins to bring about changes in cell functions

42
Q

Fast +ve feedback is

A

Fast positive feedback by low [Ca2+]

43
Q

Fast feedback is followed by

A

followed by slow negative feedback elicits transient signals by Type 1 and type 2 IP3 receptors- type III receptors do not show this regulation and so produce prolonged responses that drain stores

Cell and molecular extras (16 decks)

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