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Receptor and Signaling > cGMP > Flashcards

cGMP Flashcards

1
Q

a passage through a cell membrane that uses energy to
move ions or other molecules AGAINST their
concentration gradient

A

Ion Transport

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2
Q

Ion transporters use

A

energy like ATP

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3
Q

types / examples Ion transportation

A

Plasma membrane Ca2+ ATPase
Sodium-calcium exchanger
Sodium chloride symporter
Glycine transporter

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4
Q

Passage through a cell membrane that lets ions flow
DOWN their concentration gradient if it is open; not if it
is closed

A

Ion Channels

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5
Q

________ equalizes the concentrations on either side of the cell
membrane

A

Ion Channels

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6
Q

Ion channels accomplish this equalization via ____________ which is a type of _______transport

A

Facilitated diffusion

Passive

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7
Q

________ is typically one type of ion and activated by changes in electrical membrane potential

A

Voltage gated Ion channel

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8
Q

_____ is less selective and multiple ions

activated by extracellular ligand binding

A

Ligand gated ion channels

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9
Q

What are the three classifications for mechanosensitive ion channels

A

cation
anion
non-selective

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10
Q

_________ activated by mechanical deformation in the membrane

A

stretch-gated / mechanosensitive

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11
Q

______ ion channel is G-protein regulated

A

signal-gated

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12
Q

ion channels can be ______________ for fast acting mediation of ion flow across membrane

A

Ligand gated receptors

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13
Q

Ion channels can be ______________ regulated to mediate slow acting ion channel opening for longer period of time

A

G-Protein regulated

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14
Q

How are ion channels regulated by GPCR (3)

A

G protein alpha or beta-gamma subunit
cAMP, cGMP or DAG
PKA or PKC phosphorylation

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15
Q

how do cAMP, cGMP and DAG regulate ion channels?

A

by directly binding to the channels

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16
Q

what are targets of G proteins so far? 3

A

AC
PLC
ion channels

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17
Q

What is Rhodopsin

A

GPCR for retinal rods

in the intracellular membrane.

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18
Q

why is rhodopsin a major GPCR prototype?

A

Retinal rod outer segment membranes are nearly pure
rhodopsin
therefore rhodopsin was easily identified, purified, studied

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19
Q

what is the ligand for Rhodopsin?

how is it bound?

A

11-cis-retinal

covalently bound

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20
Q

What is the signal and the detector?

A

signal : light photon

detector: 11-cis-retinal

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21
Q

what happens when photon hits the 11-cis-retinal,

A

it causes a conformational change in the retinal, which then changes structure of receptor (C3 loop) and that activates the G-protein transducin

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22
Q

explain the transition from 11-cis-retinaldehyde to all-trans-retinaldehyde ?
which one happens fast?

A

11-cis-retinaldehyde While bound to receptor; changes receptor conformation when light is detected

Once isomerized, it is clipped off, dissociates
from receptor;

enzymatic re-isomerization,
then covalently reattaches to Rhodopsin- happens fast

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23
Q

What is Transducin?

A

Transducin is a G protein (alpha, beta and gamma)

abbreviated GT and is a Gi family member

24
Q

explain what Visual System – Rhodopsin & G protein messenger?

A 
1. Rhodopsin is activated by light. 
Conformational change leads to 
activation of G-protein transducin (GT). (release GDP, bind GTP)
2. The GTα•GTP activates cGMP-PDE
3. The cGMP-PDE breaks down cGMP to 
GMP
4. When cGMP is broken down, it comes 
off the ion channel which leads to 
closing of the channel
5. Ions stop flowing, depolarizes 
membrane, sends electrical signal 
down optic nerve to the brain
25
Q

explain Rhodopsin pathway in light vs dark

A 
When it is dark, we make cGMP 
continuously to keep ion channel 
open (Burning ATP to pump ions back out)
Light turns the cGMP off, closes 
the ion channel
26
Q

GT is substrate for what?

A

a substrate for both cholera and pertussis toxin

27
Q

In Rhodopsin pathway
________ is secondary messenger
________ is the effector
_________ regulated step

A

Second messenger = cGMP
Effector for G protein = cGMP phosphodiesterase that
cGMP degradation is the regulated step;

28
Q

what is the target for cGMP?

A

membrane ion channel

29
Q

how is cGMP phosphodiesterase activated?

A

by alpha-GTP of GT (Gi family)

30
Q

cGMP is synthesized by

A

guanylyl cyclase

31
Q

The ion channels that are the target

of cGMP are________

A

cation channels for

movement of Calcium and Sodium

32
Q

__________ the ion channel

A

cGMP

33
Q

__________ is degraded by PDE (that is activated by Gt

A

cGMP

34
Q

Synthesized by how many guanylyl cylases?

A

two
particulate membrane GC
soluble (cytosolic) GC

35
Q

Activates _________ kinase?

A

PKG

36
Q

what is the similarity between AMP and cGMP and their Cyclases

A

They all share that

“anti-parallel dimer” at the catalytic domain

37
Q

Membrane Guanylyl Cyclase is ____________

A

enzyme-linked receptor

▪ Receptor and cyclase combined in a single molecule

38
Q

where dose the hormone and enzyme activity found on enzyme-linked receptor

A

hormone binding site on

outside, enzyme activity on inside

39
Q

which part of GC is antiparallel “dimer

A

cytosolic and that’s where catalytic domain is too

40
Q

what is Atrial natriuretic factor (ANF, ANP)?

A

is a peptide hormone

released from the heart

41
Q

ANP activates what form of guanylyl cyclase

A

membrane form

42
Q

high cGMP in kidney ___________ and in blood vessel ________________

A

Kidney: decreases sodium retention

blood vessel: low blood pressure and volume

43
Q

_____________ activates Soluble (cytoplasmic) Guanylyl Cyclase

A

Nitric oxide (NO)

44
Q

How does NO activates soluble GC and where does it form and where does it act

A

Changes conformation of the Heme, and then the dimeric
GC
forms in blood vessel endothelial cells in response to stretch and acts in adjacent smooth muscles cells

45
Q

the activity of the catalytic domain of soluble GC is is regulated by ______

A

NO

46
Q

_______ makes NO

A

NOS- nitric oxide synthase

47
Q

receptor for NO is _________

A

soluble GC

48
Q

NO is _________ signaling whereas ANP is ________ signaling

A

NO- paracrine

ANP- endocrine

49
Q

Similarities between AC, mGC and sGC is

A
  • dimers in catalytic domains

- catalytic domains are highly homologous

50
Q

Differences between AC, mGC and sGC is

A
  • Membrane association
  • The regulators
  • The sites at which the regulators bind
51
Q

what is PKG (cyclic GMP-dependent protein kinase):

A
  • cGMP target
  • ser-thr kinase
  • regulatory/ receptor and
    catalytic “domains” on a single peptide chain
52
Q

cGMP targets

A
  • PKG
  • Ion channels
  • cAMP phosphodiesterase’s and cAMP
53
Q

Phosphodiesterase (PDE) breaks __________

A

a phosphodiester bond

54
Q

how many PDE families and how do they vary

A

12
- vary by tissue distribution, substrate
specificity, pharmacological properties,

55
Q

how do we regulate cGMP? (3)

A 
1. by controlling cGMP 
breakdown by 
phosphodiesterases
2. a "soluble" or "cytosolic" 
guanylyl cyclase
3. a "particulate" or 
"membrane" guanylyl 
cyclase

Receptor and Signaling (6 decks)

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