cell signaling

3 types of cell signaling

juxtacrine, paracrine, endocrine

juxtacrine signaling

cell-cell recognition via complementary proteins using gap jxns

paracrine signaling

neuronal signaling, local

endocrine signaling involves

hormones, distant target cells, endocrine cells, blood vessels

the signal is the

ligand

fat-soluble receptor

aka intracellular receptor

water-soluble receptor

aka extracellular receptor

types of receptors

ion-channels, enzymes, G-protein coupled

type of enzyme receptor

RTKs (receptor tyrosine kinases)

2 forms of G-protein coupled receptors

inactive and active

inactive form of G-protein

GDP is bound, but is replaced by GTP when ligand binds

active form of G-protein

GTP is bound and alpha subunit bind a target protein and activate second messengers

signal transduction includes

cAMP, inositol phosphates, Ca

cAMP activates

protein kinase A

inositol phosphates are

phospholipids in cell membrane that travel and bind to sER and opening Ca channels

DAG activates

PKC (protein kinase C)

PKC

phosphorylates other proteins, turning things on/off

Ca role

is for muscle contraction, secretion, and metabolism

example of ion-channel response

ivermectin

ivermectin binds

to glutamate-gated chloride channels of parasites

ivermectin keeps the channels

in an open state, causing hyperpolarization

example of RTK response

insulin

insulin binds to

RTK receptor on muscle, phosphorylating other proteins, glucose enters cell, blood glucose decreases

example of GPCR response

epinephrine

a single cell has

multiple receptors

2 ways cells stop responding

stopping the signal at the receptor or stopping the signal inside the cell

examples of stopping the signal at the receptor

removing signal molecule, internalizing the receptor, inactivating the receptor

examples of stopping the signal inside the cell

breaking down secondary messengers, inactivating signaling proteins, removing PO4 groups, degrading key proteins