<P> Second messengers are intracellular signaling molecules released by the cell to trigger physiological changes such as proliferation , differentiation , migration , survival , and apoptosis . Secondary messengers are therefore one of the initiating components of intracellular signal transduction cascades . Examples of second messenger molecules include cyclic 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 . First messengers are extracellular factors , often hormones or neurotransmitters , such as epinephrine , growth hormone , and serotonin . Because peptide hormones and neurotransmitters typically are biochemically hydrophilic molecules , these first messengers may not physically cross the phospholipid bilayer to initiate changes within the cell directly -- unlike steroid hormones , which usually do . This functional limitation necessitates the cell to devise signal transduction mechanisms to transduce first messenger into second messengers , so that the extracellular signal may be propagated intracellularly . An important feature of the second messenger signaling system is that second messengers may be coupled downstream to multi-cyclic kinase cascades to greatly amplify the strength of the original first messenger signal . For example , RasGTP signals link with the Mitogen Activated Protein Kinase ( MAPK ) cascade to amplify the allosteric activation of proliferative transcription factors such as Myc and CREB . </P>
<P> Second messengers are intracellular signaling molecules released by the cell to trigger physiological changes such as proliferation , differentiation , migration , survival , and apoptosis . Secondary messengers are therefore one of the initiating components of intracellular signal transduction cascades . Examples of second messenger molecules include cyclic 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 . First messengers are extracellular factors , often hormones or neurotransmitters , such as epinephrine , growth hormone , and serotonin . Because peptide hormones and neurotransmitters typically are biochemically hydrophilic molecules , these first messengers may not physically cross the phospholipid bilayer to initiate changes within the cell directly -- unlike steroid hormones , which usually do . This functional limitation necessitates the cell to devise signal transduction mechanisms to transduce first messenger into second messengers , so that the extracellular signal may be propagated intracellularly . An important feature of the second messenger signaling system is that second messengers may be coupled downstream to multi-cyclic kinase cascades to greatly amplify the strength of the original first messenger signal . For example , RasGTP signals link with the Mitogen Activated Protein Kinase ( MAPK ) cascade to amplify the allosteric activation of proliferative transcription factors such as Myc and CREB . </P>
what is the role of second messenger in hormone action
what is the role of second messenger in hormone action
trigger physiological changes such as proliferation , differentiation , migration , survival , and apoptosis
trigger physiological changes such as proliferation , differentiation , migration , survival , and apoptosis