DGL-alpha, 1-hexadecanoyl-2-arachidonoyl-glycerol 3-phosphocholine, Pyk2(FAK2), Arachidonic acid, G-protein beta/gamma, Alpha-2C-1 adrenergic receptor, PtdIns(3,4,5)P3, Adrenaline, HB-EGF, G-protein alpha-i3, ERK2 (MAPK1), PI3K reg class IA, G-protein alpha-o, 220.127.116.11, PLC-beta3, Shc, None, c-Jun, c-Raf-1, CaMK II, Monoglyceride lipase, AKT(PKB), Alpha-2A adrenergic receptor, Ca('2) cytosol, IP3, 18.104.22.168, Ca('2+) endoplasmic reticulum lumen, Alpha-2B adrenergic receptor, ADAM12, GRB2, CYP2C8, G-protein alpha-i2, G-protein alpha-i1, PI3K reg class IA (p85-alpha), Noradrenaline, c-Src, DGL-beta, ERK1 (MAPK3), 22.214.171.124, H-Ras, SOS, MEK1(MAP2K1), 1-palmitoyl-sn-glycero-3-phosphocholine, 14,15-EET, DAG, IP3 receptor, 3.1.1.-, Calmodulin, PDK (PDPK1), PI3K cat class IA, PtdIns(4,5)P2, 2-arachidonoylglycerol, PLC-beta2, 126.96.36.199, MEK2(MAP2K2), EGFR, G-protein alpha-i family, 188.8.131.52, Carboxylic acid, glycerol, cPLA2, ERK1/2
Alpha-2 adrenergic receptor activation of ERK
Alpha-2A adrenergic receptor, Alpha-2B adrenergic receptor, and Alpha-2C-1 adrenergic receptor participate in activation of Mitogen-activated protein kinases 1 and 3 ( ERK1/2 ) via different ways .
Alpha-2A adrenergic receptor activates Phospholipase C beta 3 or 2 ( PLC-beta3 or PLC-beta2) when complex Guanine nucleotide binding protein (G protein) beta and gamma ( G-protein beta/gamma ) is released from the trimeric complex with G-protein alpha-i family (presumably by G-protein alpha-i2 ) , . PLC-beta3 and PLC-beta2 may to hydrolyze Phosphatidylinositol-4,5-Bisphosphate ( PtdIns(4,5)P2 ) and produce 1,2-diacyl-glycerol ( DAG ) and Inositol 1,4,5-trisphosphate ( IP3 ). IP3 activates Inositol 1,4,5-triphosphate receptor type 3 ( IP3 receptor ), which causes Ca('2) release from intracellular compartments. As a result of activation of adrenergic receptor, elevated cytosolic Ca('2) levels lead to activation of Calmodulin/ most likely Calcium/calmodulin-dependent protein kinase II ( CaMK II )/ PTK2B protein tyrosine kinase 2 beta ( Pyk2(FAK2) )/ v-src sarcoma viral oncogene homolog ( c-Src )/ SHC transforming protein 1 ( Shc )/ Growth factor receptor-bound protein 2 ( GRB2 )/ son of sevenless homolog ( SOS )/ v-Ha-ras Harvey rat sarcoma viral oncogene homolog ( H-Ras )/ v-raf-1 murine leukemia viral oncogene homolog 1 ( c-Raf-1 )/ Mitogen-activated protein kinase kinase 1 and 2 ( MEK1 and MEK2 )/ Erk .
Also, activation of ERK cascade by all three Alpha-2 adrenergic receptors is accomplished by stimulation of Arachidonic acid production via DAG. DAG is catalyzed by Diacylglycerol lipase alpha and beta ( DGL-alpha and DGL-beta ) to 2-arachidonoylglycerol, which gets converted by Monoglyceride lipase to Arachidonic acid. Arachidonic acid is then converted by Cytochrome P450 (by, for instance, Cytochrome P450 family 2 subfamily C polypeptide 8 ( CYP2C8 )) to 14,15-epoxyeicosatrienoic acid ( 14,15-EET ), which activates c-Src. c-Src may phosphorylate matrix metalloproteinases, for example ADAM metallopeptidase domain 12 ( ADAM12 ). ADAM12, in turn, cleaves Heparin-binding EGF-like growth factor ( HB-EGF ) leading to transactivation of Epidermal growth factor receptor ( EGFR ). EGFR then activates Shc- and GRB2 -mediated ERK cascade activation .
In addition, Alpha-2A and Alpha-2C-1 adrenergic receptors, after activation of c-Src, can activate Shc/ GRB2/ SOS without EGFR-transactivation .
Also, all three Alpha-2 adrenergic receptors stimulate v-akt murine thymoma viral oncogene homolog ( AKT(PKB )) that is thought to activate ERK2 and ERK1. AKT(PKB ) may act via EGFR/ Phosphoinositide-3-kinase ( PI3K)/ PtdIns(3,4,5)P3/ possibly via GRB2-associated binding protein 1 ( GAB1 ) or directly/ 3-phosphoinositide dependent protein kinase-1 ( PDK (PDPK1 )/ AKT. Alpha-2A and Alpha-2C-1 adrenergic receptors are also able to activate Phosphoinositide-3-kinase, regulatory subunit 1 (p85 alpha) ( PI3K reg class IA (p85-alpha) ) via c-Src without EGFR transactivation , , .
Moreover, Alpha-2B adrenergic receptor participates in ERK activation via extracellular Ca('2+) dependent Phospholipase A2 ( cPLA2 ) activation, which in turn lead to Arachidonic acid production and to the above-described ERK cascade activation via Shc .
Due to ERK activity, adrenergic receptors influence cell growth and proliferation , . Furthermore, in nerve cells, ERK activates Jun oncogene ( c-Jun ) and participates in cell differentiation .