Cell to cell communication = Cell signalling Ligand (ex insulin, epinephrine)→ Receptor → G protein (GDP to GTP) → adenylyl cyclase→ cAMP (second messenger and signal amplification) → activate protein kinase (several kinds)→ phosphorylate a protein(s) (result in an effect) Involves a signal molecule secreted from one cell that interacts with receptors on a second cell. The secreted molecule could be a hormone, neurotransmitter, histamine or other substance that either acts locally (paracrine), moves through the bloodstream to another organ (endocrine) or is released by a neuron (synaptic). The molecule binding with the receptor initiates a sequence of events mediated by a g protein that that results in a biological effect. The type of effect depends on the secreted molecule and the cell type; some molecules can have different effects on different cells – the question is how?

Gap junction between two cells (ex muscle) to promote exchange of materials

Signals can either interact at the surface of the cell (protein hormones, growth factors) or inside the cell (steroid hormones, NO)

Different modes of signalling; we will focus on endocrine for now

gnal.htm em_sets/signaling/overview.html Good tutorials ogyPages/C/CellSignaling.html This one is a bit advanced but lists all known kinds of cell signalling

hill.com/sites/ /student_view0/chapter17/animation__sec ond_messenger__camp.html Good basic introduction to G proteins and cAMP Signal amplification G protein mediated work of epimephrine and glycogen very good ature=related cAMP and kinase example Intracellular receptors Insulin signalling example

Two keys steps for G protein activation/deactiviation: Exchange of GDP for GTP (controlled by guanine exchange factor (GEF) Conversion of GTP to GDP (controlled by GTPase activating proteins (GAPs). This step deactivates adenylyl cyclase and stops production of cAMP.

Specific example of kinase activation( cAMP omitted)

FAMILYSOME FAMILY MEMBERS ACTION MEDIATED BY FUNCTIONS IGsGs αactivates adenylyl cyclase; activates Ca 2+ channels G G olf αactivates adenylyl cyclase in olfactory sensory neurons IIGiGi αinhibits adenylyl cyclase βγactivates K + channelsK GoGo βγactivates K + channels; inactivates Ca 2+ channelsK α and βγactivates phospholipase C-β G G t (transducin)αactivates cyclic GMP phosphodiesterase in vertebrate rod photoreceptorscyclic GMP IIIGqGq αactivates phospholipase C-β Types of things that g proteins do

Another g protein mediated signal pathway : IP3 ip3dagca2pkc-pathway-animations/ 01.htm?v=chapter&i= &s=13000&n=00010&o

What kinds of cell signals use g proteins? G proteins are important in signal transduction regarding hormone function, taste, smell, and cell growth

List of diseases associated with mutations in g proteins: transduction.php

Action of cholera toxin on g protein mediated receptors