Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MCB 2050 first half > Signal transduction > Flashcards

Signal transduction Flashcards

1
Q

what are types of plasma membrane receptors?

A
  1. some activate G-protein switch proteins that trigger downstream pathways or generation of intracellular second messengers
  2. tyrosine kinases that trigger signal transduction pathways involving sequential activation of downstream kinases
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Der and the glucocorticoid receptor pathway?

A
  • Dex activates the glucocorticoid receptor
  • without Dex the receptor is in the cytoplasm
  • with Dex the receptor-hormone complex moves to the nucleus
  • the control b-galactosidase is cytoplasmic regardless of Dex
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what is the glucocorticoid receptor pathway

A
  • hormone diffuses into the cell and binds to ligand binding domain
  • hormone binding displaces chaperon proteins allowing the LBD-hormone complex to move to the nucleus and DNA binding domains can associate with response elements and transcription can happen
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

how do hydrophilic signalling molecules act?

A
  • binding of the signal molecule to a specific cell surface receptor leads to a conformational change
  • activated receptor initiates downstream signal transduction proteins/secondary messengers
  • signal transduction leads to the activation of effector proteins, which usually turns off the active receptor
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what are the 4 types of extracellular signalling

A
  1. endocrine: affects target cells some distance from the site of synthesis, hormone travels through blood
  2. paracrine: affects adjacent target cells
  3. autocrine: cells respond to signals that they produce
  4. signalling by plasma membrane-attached proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How does signal transduction by protein phosphorylation work

A
  • active target proteins are dephosphorylated by protein phosphatases to make them inactive
  • inactive target proteins are phosphorylated by a proteins kinase to make them active
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what are characteristics of secondary messenger molecules

A
  • small short-lived molecules
  • diffuse rapidly
  • allow enzymatic amplification
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the function of G-proteins and GPCRs

A
  • hydrophilic hormones that function as on-off switches for intracellular signalling by binding to membrane receptors to form GPCRs
  • G-proteins exchange GDP to GTP leading to a conformational change and activation
  • active G-proteins send a signal
  • once the signal is sent GTP is converted back to GDP and the G-protein inactivates itself
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what are the activator and inactivator proteins in G-proteins

A

GEF = activator protein: exchangers GDP for GTP, G-protein is now capable of interacting with downstream effector proteins - produces secondary messenger molecules
GAP = inactivator protein: exchanges GTP for GDP, G-protein is capable of interacting with upstream activators

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the signal transduction pathway for epinephrine

A
  • epinephrine hormone binds to the membrane receptor
  • G-protein associates with receptor and exchanges GDP for GTP
  • causes G-alpha subunit to dissociate and bind to adenylyl cyclase
  • adenylyl cyclase can now produce secondary messenger molecules (cAMP) which go on to activate protein kinase A
  • protein kinase A is now able to phosphorylate target proteins
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

subunits of G-proteins

A

3 subunits: Ga, Gb, Gy
- Ga and Gy are covalently bound to the membrane
- Gy and Gb are tightly associated
- ligand binding alters receptor confirmation allowing binding of Ga subunit causing GDP to be replaced with GTP
- Ga subunit disassociates and moves to an inactive effector to make it active

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

mechanisms of GPCR signaling

A
  1. hormone binds to induce conformational change of receptor
  2. activated receptor binds to Ga subunit
  3. activated receptor causes conformational change in Ga and triggers dissociation of GDP
  4. binding of GTP to Ga triggers dissociation of Ga both from the receptor and Gby
  5. hormone dissociates from receptor and Ga binds effector to activate it
  6. hydrolysis of GTP to GDP causes Ga to dissociate from effector and reassociate with Gby
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the GEF and GAP In the GPCR pathway

A

GEF = receptor - exchanges GDP for GTP
GAP = effector - increases the rate of GTP hydrolysis and deactivation of the G-protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what are receptor tyrosine kinases - IMPORTANT

A
  • when activated they phosphorylate downstream targets and initiate a signal transduction cascade
  • usually, the hormone or peptide leads to dimerization of 2 kinase polypeptides
  • dimerization of RTKs leads to cytoplasmic domain autophospholylation
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

how are RTKs activated

A
  • ligand binds to the ligand binding region
  • causes dimerization and phosphorylation of activation loop tyrosines on cytosolic side
  • active protein tyrosine kinase phosphorylates additional tyrosine residues
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

RTK example: EGF receptor

A
  • EGF binds to its receptor
  • dimerization alters the conformation of the intracellular domain leading to kinase activation
  • reciprocal phosphorylation of tyrosine residues on the donor and acceptor domains of the activated receptor
17
Q

what is the Ras/MAP kinase pathway

A
  • activated by RTKs
  • active Ras stimulates the formation of a signal transduction complex which contains 3 sequentially acting protein kinases: Raf, MEK and ERK
  • culminates in phosphorylation and activation of transcription factors controlling gene expression
18
Q

Ras/MAP kinase pathway in 6 steps - IMPORTANT

A
  1. hormone binds to LBD causing receptor dimerization and autophosphorylation of the RTK
  2. binding of adaptor proteins (GRB2 and Sos) bring inactive Ras. the SH3 domains of GRB2 bind to Sos and the SH2 domain interacts with phosphorylated tyrosine residues
  3. Sos acts as the GEF and promotes exchange of GDP for GTP to activate Ras, active Ras then dissociates from Sos
  4. active Ras recruits Raf and activates first kinase (Raf aka MAPKKK). 14-3-3 protein is not longer inhibiting Raf
  5. Raf (MAPKKK) phosphorylates MEK (MAPKK). Ras hydrolyzes its GTP in response and becomes inactive
  6. Phosphorylated MEK phosphorylates ERK (MAPK). ERK can move to the nucleus to activate various TFs via phosphorylation
19
Q

what are 2 ways gene expression is induced at the end of the MAP kinase pathway

A
  1. ERK (MAPK) translocates to the nucleus once activated and is able to transcribe the SRE gene
  2. ERK (MAPK) can activate p90RTK via phosphorylation which can translocate to the nucleus and phosphorylate other TFs

MCB 2050 first half (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions