Cell-Cell Communication part II

GPCR

G-Protein-Coupled Receptor, a large family of cell-surface receptors that respond to various ligands and activate intracellular signaling pathways.

Ligand

A molecule that binds to a receptor, triggering a response; examples include proteins, small peptides, amino acids, and fatty acids.

cAMP

Cyclic adenosine monophosphate, a second messenger involved in signal transduction pathways activated by GPCRs.

Adenylate Cyclase

An effector protein that converts ATP to cAMP in response to GPCR activation.

Phospholipase C

An effector protein that generates inositol trisphosphate (IP3) and diacylglycerol (DAG) as second messengers.

G-Protein

A molecular switch that transmits signals from GPCRs to effector proteins; consists of three subunits:alpha (α), beta (β), and gamma (γ).

GDP

Guanosine diphosphate, a molecule that binds to the inactive form of G-proteins.

GTP

Guanosine triphosphate, a molecule that activates G-proteins upon binding, causing a conformational change.

PKA

Protein Kinase A, an enzyme activated by cAMP that phosphorylates target proteins to elicit cellular responses.

IP3

Inositol trisphosphate, a second messenger that triggers calcium release from intracellular stores.

DAG

Diacylglycerol, a second messenger that activates Protein Kinase C (PKC).

Vasopressin

Also known as antidiuretic hormone (ADH), a hormone that regulates water reabsorption in the kidneys via GPCR signaling.

Renin-Angiotensin System

A hormone system that regulates blood pressure and fluid balance, involving the conversion of angiotensinogen to angiotensin II.

Cholera Toxin

A bacterial toxin that activates adenylate cyclase, leading to increased cAMP and chloride secretion, causing diarrhea.

Pertussis Toxin

A bacterial toxin that inhibits adenylate cyclase by preventing GDP release from the G-protein, affecting respiratory signaling.

Signal Amplification

The process by which a single ligand-receptor interaction leads to a large cellular response through multiple signaling cascades.

Aquaporin-2

A water channel protein whose expression is regulated by vasopressin signaling, increasing water reabsorption in the kidneys.

G-Protein Subtypes

Variants of G-proteins (e.g., Gas, Gai) that can have stimulatory or inhibitory effects on adenylate cyclase.

GPCR Gene Superfamily

A large family of genes encoding GPCRs, with over 800 homologous genes identified in humans.