Principles of Cell Communication

Extracellular and Intracellular receptors

Target protein, Conformational change such as ion channels

Hydrophilic signal molecule

Hydrophobic signal molecule

Contact Dependent - Requires direct contact with cells. (Target cell with a membrane-bound receptor and ligand binding).
Paracrine - The signaling cells are near the target cell. (Signal molecule diffuses from the signal cell).
Synaptic - Exclusive to neurons. (Axons are frequently located distant from the cell body/soma).
Endocrine - Hormones, signaling cell release hormones to the target cell.
Autocrine - Cells that can communicate with themselves. Signal molecule that can bind to its receptor.

Cells that directly communicate with each other. Allows for direct flow of small molecules (Ca++ and cAMP). Important for development.

A neurotransmitter or signal molecule. Causes increased skeletal muscle contraction but decreases heart muscle cell rate.

Ion channel linked- Causes some form of change in membrane potential
G-protein linked receptor - GTP binding trimeric protein mediates receptor and target protein interaction.
Enzyme-linked - Ligands/single pass TM protein involved with enzymes. (enzymes go on to activate kinases and phosphatases).

Has its own intrinsic GAP. Made of Gamma, Alpha and Beta subunit.

Network of intracellular signaling molecules. They are called second messengers. (cAMP, Ca++ and DAG).
Molecular switches such as protein kinases and protein phosphatases.

Scaffolding, Activated receptors and phosphoinositides

Scaffolding is a protein that brings together and organizes signal proteins. Enhances cell signaling efficiency.
Phosphoinositides are lipid signaling molecules that coordinate cell signaling.