2 Flashcards
autocrine:
a cell that makes and responds to its own chemical signal
paracrine:
chemical signals that interact with receptors on nearby cells
endocrine:
chemical signals are secreted into the blood and carried to the cells they act upon
chemical signals can be called
hormone
growth factor
cytokine
agonist
ligand
signal transduction - 1st mechanism
transmembrane receptor has protein kinase activity in cytosolic domain
signal transduction - 2nd mechanism
transmembrane receptor interacts with adjacent G-protein on cytosolic membrane surface
causing inactive trimer to dissociate into active monomer and dimer
signal transduction - 3rd mechanism
intracellular receptor interacts with hormone and undergoes conformational change
coz of hydrophobic hormones can cross plasma membrane
examples of 2nd messengers released into vicinity of enzymes
cAMP / protein kinase A
when does protein activity occur?
on arrival of a signal, intracellular proteins are activated to initiate a response
zymogenic activation
proteases cleave immature to mature enzyme (e.g. trypsinogen to trypsin)
covalent modification
adding chemical groups to proteins to alter their activity
e.g. phosphorylation, methylation, myristoylation, palmitoylation, oleoylation, glycosylation
1) receptor occupancy:
dimerisation and autophosphorylation
2) attraction of SH2 domains:
binding to substrates and adaptors
3) substrates initiate response
signalling cascades = phosphorylate several types of downstream proteins
phosphorylate end-target proteins = conformational change that is a response
signalling cascades:
- kinases can phosphorylate other kinases, which can phosphorylate other kinases and so on
- tyr kinases
- ser / thr kinases
