FoM:L7 - Signal transduction through cell surface receptors Flashcards
1
Q
What are the signalling molecules?
A
- molecules with a specific shape
- binds noncovalently to receptors
2
Q
What are some examples of signalling molecules?
A
- neurotransmitters
- hormones
- growth factors and cytokines
- vitamin A and D derivatives
- nitrous oxide
3
Q
What are neurotransmitters?
A
- small amino acids/derivatives that act as chemical messengers
- released by neurons
- cross synapse
- quickly degraded
4
Q
What are hormones - eicosanoids?
A
- derived from arachidonic acid
- autocrine or paracrine
- involved inflammation
5
Q
Outline intracellular signalling
A
- pass through bilayer
- receptors in cytoplasm or nucleus
- H-R complex binds to hormone response element (HRE)
6
Q
Outline the structure and basic function of plasma membrane receptors
A
- have extracellular, membrane spanning and intracellular domains
- produce rapid effects on cellular ion levels/enzyme activation and inhibition
- slower changes in rate of gene expression
7
Q
What are 4 main enzymes involved in cell signalling?
A
- GTPases: hydrolyse GTP to GDP
- phosphodiesterase
- kinase: transfer of phosphates
- phosphatase: remove phosphates (specific to acid or alkali envt.)
8
Q
How does NO act as a signalling molecule?
A
- primary messenger in smooth muscle relaxation
- second messenger within cells
- activates guanylyl cyclase: GTP -> cGMP
9
Q
What are GPCRs?
A
- 7 membrane spanning alpha helix domains coupled with a G-protein
- specific extracellular binding domain
- no kinase activity
- heterotrimers
10
Q
How do GPCRs function?
A
- signalling molecule binds
- G protein exchanges GDP for GTP
- stimulates adenylyl cyclase
- second messengers formed
11
Q
What is signal amplification?
A
- each receptor-ligand complex activates many G proteins
- each G protein can activate multiple adenylyl cyclases
- each adenylyl cyclase will convert multiple ATP to cAMP
- cAMP activates protein kinase A
12
Q
What is phospholipase C?
A
- effector: can be activated by G proteins
- degrades PTI in cell membranes releasing IP3 (2nd messenger)
- DAG left in membrane
- IP3 diffuses to ER, opens Ca2+ channels
13
Q
What are tyrosine kinase receptors activated by?
A
- activated by growth and differentiation factors or metabolic regulators
14
Q
What happens when a tyrosine kinase receptor is activated?
A
- tyrosine residues are phosphorylated
- dimer forms
- receptor can recognise and activate adapter proteins
15
Q
What is a MAP kinase cascade?
A
- sequential kinase activity
- GF binding, receptor dimerization and autophosphorylation
- adaptor protein docks
- SOS (a GEF)
- GRB-SOS activates RAS
- RAS activates Kinase-kinase-kinase which activates kinase-kinase which activates kinase
- kinase phosphorylates target transcription factors
