AboutSecond messengers

Dr. Yasser Ashour

By Dr.Darine Ashraf

Dr.Alaa Mamdouh

Second messengers are intracellular signaling molecules released by the cell to trigger physiological changes such as proliferation, differentiation, migration, survival, andapoptosis.

Secondary messengers are therefore one of the initiating components of intracellular signal transduction cascades.

 

Examples of second messenger molecules includecyclic AMP ,

cyclic GMP ,inositol trisphosphate ,diacylglycerol ,and 

calcium .

The cell releases second messenger molecules in response to exposure to extracellular signaling molecules—the first messengers.

CAMP PATHWAY

Ligands : Epinephrine Ach

Primary Effector : Adenyl cyclase

Secondary messenger : cAMP

CGMP PATHWAYLigands : ANP & NO

Primary Effector : Guanylate cyclase

Secondary messenger : cGMP

CALCIUM AS SECOND MESSENGERCalcium ions – once they enter the cytoplasm exert allasteric regulatory effects on many enzymes & protien.

Calcium acts as a second messenger by indirect signal transduction pathways such as via G protein – coupled receptors.

EICOSANOIDSThis class of llipids act as signaling molecules that binds to cell surface molecules.

They include: Prostaglandins

Prostacyclin Thromboxanes

Leukotrienes

GENERAL SCHEMATIC OF SECOND MESSENGER MECHANISM