Cell signalling 1 Flashcards
What is the basic concept of cell signalling?
A chemical released by 1 cell is recognised by another cell
- involves receptor molecule that recognises signal in a highly specific manner
= allows recipient cell to respond
Why is cell signalling important?
> essential for coordination of cell behaviour
single cell orgs use signalling to identify + interact w/ cells of correct mating type in sexual reproduction
multicellular orgs depend on signalling for correct development, tissue maintenance + homeostasis
What happens if a cell doesn’t receive a survival signal?
What happens if signals are mis-regulated?
Undergoes apoptosis
Cancer
What do insulin signals do when blood glucose rises after eating food?
Pancreatic beta cells secrete insulin
–> acts on adipose/muscle/liver cells
= glucose + amino acid uptake + storage
How could problems with insulin signalling lead to diabetes?
Insufficient insulin production
= failure of pancreatic beta cells
Insulin insensitivity
= failed response of peripheral tissues
What are the 4 main types of cell signalling systems?
> endocrine
paracrine
neuronal
contact-dependent (juxtacrine)
What is endocrine signalling?
Endocrine cells release hormones that act on distant target cells in the body
What is paracrine signalling?
Signal only goes short distance + acts on cells in same tissue or adjacent tissue
What is neuronal signalling?
1 cell releases neurotransmitter molecules across a synapse
What is contact-dependent signalling?
Signal only acts on touching adjacent cells
How are neutrons + support cells formed during development?
Through contact mediated cell signalling involving Delta + Notch
What is delta?
What is notch?
A membrane-bound inhibitory signal protein
A receptor protein
What does neurogenin do?
Promotes the expression of delta signals
Describe Delta-Notch signalling in neuronal differentiation
- Unspecified epithelial cells signal to their neighbours to maintain low neurogenin levels
= promotes low levels of Delta expression - By chance some cells will express higher levels of Delta
-> signals to surrounding cells to prevent neurogenin expression
= stops them from differentiating as neurones + reduces their expression of Delta - Neurogenin levels increase in cells NOT receiving Delta signal
= allows expression of factors e.g. Neuro D
= initiate neuronal differentiation
What 3 mechanisms could be used to ensure local signals don’t act too far from their origin?
> rapid degradation
binding to inhibitory proteins
binding to ECM
How does AcH affect heart muscle, salivary gland cells + skeletal muscle differently?
What are their receptors?
Heart = decreased rate of firing
receptor:GPCR
Salivary gland = secretion
receptor: GPCR
Skeletal = contraction
receptor: ligand-gated ion channel
What can the molecular relay/ intracellular signalling pathway (initiated after signal-receptor interaction) allow?
> modulation of the signalling pathway e.g. cross-talk w/ other signalling pathways
amplification of the pathway
distribution of signal to all parts of cell
What are the 2 examples of cell-surface receptors?
G-protein coupled receptors
Enzyme-linked receptors
What are the 2 types of intracellular receptors + their examples?
> those that act as transcription factors
e.g. steroid + thyroid hormone receptors
> enzymes directly activated by the signal molecule
e.g. guanylyl cyclase activated by NO
What are steroid + thyroid hormones?
Small, hydrophobic signal molecules that interact w/ intracellular receptors
–> hormone-receptor complex moves into nucleus + acts directly as a TF
Which cells produce testosterone?
Leydig cells in testis
What is androgen insensitivity syndrome?
XY individuals lack testosterone receptor
–> develop female physical characteristics
What is NO used to treat?
Angina = pain associated w. poor blood flow to heart
Which features of NO ensures it acts only locally?
Reacts readily w/ O2 + water to form nitrates/nitrites
Half life = 5-10 seconds
Describe how NO is used to treat angina
- Nerve terminal releases neurotransmitter + binds to receptor on endothelial cell
- Signalling system in cell produces NO (from arginine)
- NO fuses to smooth muscle cells
- NO binds to target protein (guanylyl cyclase)
= rapid relaxation of smooth muscle cell
–> dilates blood vessel
What happens when guanylyl cyclase is bound to NO?
How is this signalling reversed?
Converts GTP to cGMP
–> increased cGMP = smooth muscle cell relaxation
= blood vessels dilate
cGMP phosphodiesterase converts cGMP into 5’-GMP
–> muscle cells contract
= blood vessels constrict
How does viagra work?
Inhibits PDE5 phosphodiesterase in the blood vessels of erectile tissue
= sustained signalling response
= blood vessels remain dialect
