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Block 1 Week 3 > CELL BIOL (Perrino): Receptors > Flashcards

CELL BIOL (Perrino): Receptors Flashcards

1
Q

What membrane proteins represent 50 percent of drug targets?

A

GPCR!!!

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2
Q

Can a ligand bind to more than one GPCR, and can the receptor bind to more than one ligand?

A

YEAH! they can both bind to a lot of GPCRs and ligands, respectively

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3
Q

How many transmembrane domains does EVERY GPCR have?

A

Seven! These domains are also the most conserved parts

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4
Q

What parts of GPCRs are diverse?

A

The binding site AND the cytosolic domain

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5
Q

Examples of ligands with a ton of receptors!

A

Adrenaline has 9. ACh has 5. serotonin has 15 GPCRs

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6
Q

What cells, tissues, and organ systems express GPCR and enzyme linked receptors?

A

ALL OF ‘EM

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7
Q

ALL alpha units of G protein serve to what?

A

serve as a GTPase to bind to GTP and then hydrolyze it

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8
Q

Once ligand binds to GPCR, what’s the first step?

A

the G protein complex (alpha, beta, gamma) docks to receptor protein. receptor protein!

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9
Q

What happens immediately after GDP-coupled alpha subunit binds to receptor?

A

GDP gets exchanged for GTP; and the BOTH alpha subunit and BY complex are considered activated

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10
Q

What does GTP cause the ABY complex in g proteins to do?

A

it activates AND dissociates them!

well, A apart from BY

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11
Q

Where do activated subunits go (usually the alpha)?

A

they find the TARGET protein on the cytosolic side of the membrane to attach to

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12
Q

What does the hydrolysis of GTP coupled alpha subunit do?

A

It causes the alpha to dissociate from target protein. and then alpha reassembles with BY. LAST STEP IN GPCR

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13
Q

describe cholera mechanism

A

binds to the α subunit so that it can no longer hydrolyze its bound GTP, causing it to remain in an active state that stimulates adenylyl cyclase indefinitely.

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14
Q

In alpha-andrenergic receptor what does activated g protein alpha subunit do?

A

It inhibits adenylyl cyclase! no cAMP

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15
Q

In alpha-andregenic receptor what does the activated BY complex do?

A

It activates the K+ channel for efflux of potassium

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16
Q

In alpha-andregenic receptor, what does the hydrolysis of the GTP coupled alpha subunit do?

A

like always, it causes ABY to reassociate!

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17
Q

What does pertussin toxin block?

A

the affects the GDP-ABY complex such that the subunits do not get activated because they remain bound. remember that it’s a Gi alpha for a target protein. So if it did work, the BY would probably be putting in work, just like the other alpha andregenic receptor examples.

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18
Q

What does PKA mean?

A

Protein KinASE

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19
Q

What does inactive PKA look like?

A

It has a dimeric regulatory subunit connected to an inactive catalytic dimeric subunit

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20
Q

What does cAMP do to the inactive PKA?

A

It binds to the REGULATORY subunit to make a cAMP-regulatory subunit complex. Additionally, this causes the release of the catalytic subunits (both separate) and now they become ACTIVE!

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21
Q

PKA activates what and blocks what in fight or flight?

A

active PKA inactivates glycogen synthesis and upregulates glycolysis production

22
Q

Why does ligand for somatostatin up regulation produce a longer PKA response than, say, flight or fight?

A

Ligand activates PKA like usualy, but the activated PKA phosphorylates CREB,which is a DNA bnidning protein that somatostatin hormone gene transcription

23
Q

is the cAMP/PKA cascade common in hormones?

A

Yup!

24
Q

How can you deactivate cAMP pathway?

A
  1. PDE

2. phosphotase

25
Q

What does PDE stand for and what does it do?

A

Phosphodiesterase breaks phosphodiester bonds and converts cAMP to regular inactive AMP

26
Q

What does phosphotase do?

A

It removes phosphate groups from proteins, such as the CREB binding protein in the somastatin pathway

27
Q

How specific are regulatory protein phosphotases?

A

They’re not specific at all. They’re very promiscuous

28
Q

Main FX of phosphotases?

A

To dephosphorylate phosphate kinase dependent proteins

29
Q

First step in PKC cascade after ABY activation

A

phosphoLIPASE C gets actiated and then breaks up DAG-IP3

30
Q

Where does the free IP3 go?

A

it binds to a transporter on the lumen of the ER which causes a conformational change and therefore the release of CA++!!

31
Q

What does the release of Ca++ in the PKC cascade do?

A

the Ca++ binds to the PKA C (DAG also binds to the PKA C), and then it activates it.

32
Q

What does an acttvated PKA C do?

A

it phosphorylates a bunch of other proteins!

33
Q

is calcium way higher in the cell or outside the cell?

A

Outside has [CA++] concentration by ten thousand fold

34
Q

Why is Ca++ so low in the cytosol? (3 reason)

A
  1. active transport to ER
  2. active transport to MT
  3. calcium binding molecules in cytosol
35
Q

What are the 2 ways to raise Ca++ in the cell?

A
  1. voltage gated calcium channels in nerve cells!

2. GPCR response that releases IP3 to bind to transporter on ER and allow CA++ to flow into cytosol

36
Q

In cardiac myocytes, instead of IP3 what activates calcium efflux outside of ER?

A

Addition of calcium coming from the plasma membrane

37
Q

Main mechanims for GPCR response? Occurs about 90 percent of time

A

the cAMP pathway that activates a PKA for fruther singaling

38
Q

Now, how common is the PKA C pathway?

A

pretty common but not nearly as common as the cAMP pathway

39
Q

In olfaction, what is the name of the target protein that activated Galpha

A

Adenylyl cyclase

40
Q

What does adenylyl cylcase do in olfaction?

A

it actiates cAMP cascade

41
Q

What does cAMP do in olfaction?

A

It binds to the Na+ transporter to allow sodium in and depolarize the cell. then signal goes to brain

42
Q

Describe the signalling pathway of rod cells in dark.

A

rhodopsin inactivated; Gt (transducin) inactivated; low PDE; cGMP is active ; cell is depolarized; and then high rate of synapse

43
Q

Describe signalling pathway of rod cells in light

A

Light activates rhodopsin and then G protein transducin is activated; this then activates phosphodiesterase PDE which then lowers the amount of cGMP (by breaking phosphodiesterbonds); and then therefore sodium channels close so the cell is hyperpolarized. low synapse rate

44
Q

What happens if a GCPR has been on far too long”

A

It gets desensitized

45
Q

What’s the first step in the GPCR phophorylation process?

A

Activated GPCR stimulates GRK, GRRRRRRKK, to phophorylate the GPCR at MULTIPLE sites. so then

46
Q

What happens to the GPCR domain site after it’s multiphosphorylated?

A

ARRESTIN bdinds onto the domain part of the GPCR, completely blocking the cytosolic domain

47
Q

How many domains do ALL tyrosine kinase receptors have?

A

JUST ONE!!!!!!!!!!!!! Unlike 7 in GPCR

48
Q

_____ are usually growth factors

A

receptor tyrosine kinases

49
Q

After receptor binds to RTK, what happens? And then what happens after that?

A

RTKs dimerize, and then they autophosphorylate each other

50
Q

Tyr phophoyrylation WITHIN kinase somain increases or decreases kinase activity?

What about Tyr phosphorylation outside the domain?

A

INCREASES kinase activty?

provides docking sites for binding of other signaling proteins

Block 1 Week 3 (10 decks)

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