B1W3 Receptors

Question 1

generic intracellular signalling pathway

Answer 1

extracellular signal molecule binds to a receptor protein, there is an intracellular signaling protein cascades that transmit signal to the effector proteins in the cell, which can alter metabolism, gene expression, or cells shape or movement

Question 2

g protein coupled receptor

Answer 2

largest and most diverse family
multipass (7) transmembrane protein
pretty much can bind any signal molecule, many drugs target these

Question 3

cytosolic components of Gprotein

Answer 3

alpha subunit picks up GTP and is activated

heterotrimeric complex

Question 4

GPCR signalling mechanism

Answer 4

Signal molecule binds, changing conformation, increases affinity for the heterotrimeric protein, that causes the GDP to be exchanged for the GTP, which then sends off the beta and gamma parts that go activate other proteins

Question 5

turning off GPCR

Answer 5

P leaves and makes GTP into GDP and everything turns off again, the Betagamma subunit comes and binds again and everything goes back to basal levels

Question 6

Gs alpha

Answer 6

activates adenylyl cyclase, activated Ca channels

Question 7

Golf alpha

Answer 7

activates adenylyl cyclase in olfactory sensory neruons

Question 8

Gi alpha

Answer 8

inhibits adenylyl cyclase

Question 9

Gi betagamma

Answer 9

activates K+ channels

Question 10

Gt alpha

Answer 10

activates cyclic GMP phsophodiesterase in vertebrae rod photoreceptors

Question 11

Gq alpha

Answer 11

activates phospholipase C-beta

Question 12

cholera toxin

Answer 12

blocks alpha subunit so it can’t be turned off, lose tons of water because calcium channels are activated

Question 13

cyc AMP

Answer 13

made from a GPCR,
Cyclic AMP activates Protein Kinase A (PKA) , cycAMP binds and it releases the active subunits
PKA is a multifuncitonal protein kinase, so it has many jobs, phosphorylates many substrates like serine or threonine

PKA can mediate a large variety of responses (like flight or fight) or increase gene trx by activating CREB

Question 14

inactivation and reversal of cAMP pathways

Answer 14

need to reverse their on switches
has to be dephosphorylated, (GTP to GDP), then the phosphodiesterase will start to break down cAMP levels, which turns off the PKA, phosphatases will dephosphorylate the proteins

Question 15

Gq pathway

Answer 15

Gq pathway: activates alpha and betagamma subunits, then it activates phospholipase C beta, which acts on PIP2 which makes IP3, which activates protein kinase C by binding to and opening calcium channels in the ER PKC also needs DAG

Question 16

maintaining Ca levels

Answer 16

Outside the cell, there is higher Ca then inside the cell (10^-7)
Opening any calcium channel will flow really rapidly because of the huge gradient
Takes energy to maintain this calcium pump, to keep cytosolic calcium low and keep Ca high in ER

Question 17

calcium in cardiac cells

Answer 17

In cardiac cells, combo of both mechanisms, cell has voltage based calcium channels and the internal calcium

Depolarization causes Ca to flow in, then the sarcoplasmic reticulum binds the calcium and releases more calcium from the SR (calcium induced calcium release

Question 18

Golf

Answer 18

normal GCPR pathway, the cAMP levels open a Na+ channel

Question 19

cGMP gated Na+ channels for sight

Answer 19

in rod cells, light activates rhodopsin, which activates Gt, increases phosphodiesterase which decreases cGMP, which closes the Na+ channels so the rod cell is hyper polarized, low rate of neurotransmitter release

opposite in the dark

Question 20

GRK

Answer 20

it phosphorylates the GPCR when it has been on too long, allows arrestin to bind so the GPCR is forced to turn off

Question 21

tyrosine kinase receptors

Answer 21

Intrinsic enzymatic domains (rPTKs, and rSer/Thr kinases) within the receptor subunit o the cell
Unlike GCPR, these are single pass transmembrane domains
Receptor dimerization of the receptors

Question 22

TKRs activate:

Answer 22

They have tyrosine kinase domains in the cell, the other domains outside the cell
lots of growth factors!!!! Things that cause the cell to proliferate, protein kinases mediate those signalling responses (they are compromised in cancer diseases)

Question 23

mechanism of RTKs

Answer 23

Dimerization is critical for their activity
When they dimerize, there is a phosphorylation activity
Signals can be dimer, monomer, in the cytosol, attached to other proteins

Question 24

autophosphorylation of RTK

Answer 24

Auto phosphorylation

Provide docking sites for other proteins that become activated upon binding to the phosphorylated tyrosine

need continuous presence of the ligand to keep it activated

Question 25

insulin and IGF-1 receptors

Answer 25

everything is the same, but they have IRS-1 that is used to dock other proteins

Question 26

Ras proteins

Answer 26

Influences the associated enzymatic activities, Ras is inactivated with GDP, there is an increase in GEF so GTP can bind.
(stays on for a long time with GTP bound)
GAP needed to remove the Pi to make it GDP again

RTKs are linked to GEFs to drive Ras to the active state

Question 27

MAP kinase pathway

Answer 27

MAP kinase pathways are mostly activated by growth factors
Ras binds to Raf
Raf binds to Mek
Mek binds to Erk
That phosphorylates a bunch of other proteins that change protein activity or gene expression

Use RTKs to activate Ras to make this pathway work

Question 28

cell survival with PI3kinase and Akt

Answer 28

Akt is phosphorylated buy the PI3 kinases, then it phosph. Bad which inactivates it and lets the apoptosis inhibitory protein run free=cell survival