Cell Signalling 2 Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

Define;
- phosphate
- kinase
- protein kinases

A

Phosphate - composed of 1 Phosphorous atom and 4 Oxygen atoms

kinase - enzyme that transfers the terminal phosphate group from ATP to a substrate

Protein kinases transfer the
phosphate group to specific serine, threonine or tyrosine residues in proteins.

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

Describe the enzyme-coupled receptor structure

A

Ligand binding domain - extracellular region that allows for easy access and activation to the receptor

Transmembrane domain - a series of hydrophobic amino acids that tethers the receptor to the cell membrane

Intracellular domain - either contains intrinsic catalytic activity or tightly bound to an enzyme

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

Describe the main stages of Receptor Tyrosine Kinase activation

A

When the ligand binds, the receptors form dimers

Receptor’s enzymatic activity
of the intracellular region - tyrosine kinase domain is turned on

The receptor units cross-
phosphorylate

Phosphate groups on the receptor form the basis for docking sites so other proteins can bind and undergo phosphorylation on tyrosines for activation

Docked proteins relay the signal

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

Differentiate between Protein Kinases and Guanine Nucleotide Exchange Factors

A

Protein kinases;
- Phosphorylate proteins to regulate function
- target serine, threonine, or tyrosine residues
- mechanism of action is transfer of phosphate to ADP
- Signal amplification through phosphorylation

Guanine Nucleotide Exchange Factors;
- facilitate GDP-GTP exchange on G proteins
- target GTP-binding proteins
- mechanism of action is to promote GTP binding to G proteins
- activate G proteins as molecular switches

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

What are activated intracellular proteins bound by ?

A

Intracellular signalling proteins docked on activated RTKs usually bind phosphorylated tyrosines through Src Homology 2 (SH2) domains.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Discuss signalling pathways activated by Receptor Tyrosine Kinases

A

RTKs: Dimerize and autophosphorylate upon ligand binding.

Main Pathways:
RAS-MAPK: Regulates proliferation/differentiation via RAF → MEK → ERK.
PI3K-Akt: Promotes survival and growth via PIP3 → Akt activation.
PLCγ: Triggers Ca²⁺ release (IP3) and PKC activation (DAG).
JAK-STAT: Directly regulates gene expression through STAT activation.

Functions: Control proliferation, survival, growth, and differentiation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is small GTPase RAS ?

A

First commonly activated molecule after RTK activation is a protein called Ras
Molecular switch that alternates between GTP bound (on) and GDP bound (off)
GTP-bound Ras associates with the plasma membrane,
diffuses laterally, and activates other proteins at the cell surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Describe the RAS-MAPK pathway:

A

Ras activates a chain reaction of phosphorylation events involving mitogen-activated protein kinases (MAPKs)

MAPKs usually held together by scaffolds - they ensure that specific MAPKs are activated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Describe Activation of RAS-MAPK by EGF:

A

EGF Binding: EGF binds to EGFR extracellular domain.

Dimerization: EGFR dimerizes and autophosphorylates on tyrosine residues.

Adaptor Proteins: Phosphorylated EGFR recruits Grb2 (adaptor protein) and Sos (guanine nucleotide exchange factor).

RAS Activation: Sos activates RAS by exchanging GDP for GTP.

MAPK Cascade: Active RAS-GTP activates RAF → RAF activates MEK → MEK activates ERK (MAPK).

Nuclear Response: ERK translocates to the nucleus and phosphorylates transcription factors, regulating gene expression.

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