Pathway maps

G-protein signaling_G-Protein alpha-s signaling cascades
G-protein signaling_G-Protein alpha-s signaling cascades

Object List (links open in MetaCore):, cAMP, H-Ras, G-protein alpha-s, ATP cytosol,, Adenylate cyclase type I, CREB1, Anaphase-promoting complex (APC), RAP-1A, GSK3 beta, G-protein beta/gamma, PDZ-GEF1, ADP , c-Src, cAMP-GEFI, MEK1(MAP2K1), cAMP-GEFII, Ryanodine receptor 1, GSK3 alpha, MEK2(MAP2K2), PDE4A, Erk (MAPK1/3), PKA-reg (cAMP-dependent), RGS2, Alpha adducin, KPYR,, AMP,, c-Raf-1, AK5, AK1, B-Raf, PKM2, PKA-cat (cAMP-dependent)


G-Protein alpha-s signaling cascades

G-protein alpha-s coupled receptors interact with trimeric G-protein alpha-s/ beta/gamma causing exchange of GDP for GTP bound to G-protein alpha-s subunits, followed by dissociation of the beta/gamma heterodimers.

G-protein alpha-s can directly stimulate activity of v-src sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog ( c-Src ) and Adenylate cyclase 1 ( Adenylate cyclase type I ) .

Regulators of G-protein signaling (RGS) proteins are GTPase-activating proteins (GAPs) that attenuate signaling by heterotrimeric G proteins. Regulator of G-protein signaling 2, 24kDa ( RGS2 ) directly binds with G-protein alpha-s and selectively inhibits G protein alpha-s function [1].

G-protein alpha-s activates all isoforms of adenylate cyclases. After stimuli, Adenylate cyclase type I increases levels of cAMP in the cell and activates Protein kinase, cAMP-dependent ( PKA ) inactive complex ( PKA-reg (cAMP-dependent) - PKA-cat (cAMP-dependent) ), which results in PKA activation [2].

PKA regulates activity of different proteins participating in various cell processes.

PKA-cat (cAMP-dependent) phosphorylates and stimulates cAMP responsive element binding protein 1 ( CREB1 ) [3]. Phosphorylation of phosphodiesterase 4A, cAMP-specific ( PDE4A) by PKA-cat (cAMP-dependent) increases PDE4A activity and catalyzes cAMP hydrolysis [4]. PKA-cat (cAMP-dependent) also phosphorylates Ryanodine receptor 1 ( RYR1 ) and, thereby, activates a calcium (Ca2+) release channel [5].

On the other hand, phosphorylation by PKA inhibits Glycogen synthase kinase-alpha/beta ( GSK3alpha/beta ) activity [6], reduces the affinity of Adducin 1 ( Alpha adducin ) for actin complexes, and blocks the action of Anaphase-promoting complex (APC), which regulates mitotic progression and chromatin assembly [7].

Other targets for cAMP are guanine nucleotide exchange factors for small GTPases. cAMP binds guanine nucleotide exchange factor Rap guanine nucleotide exchange factor (GEF) 2 ( PDZ-GEF1 ) and activates Mitogen-activated protein kinase kinases 1 and 2 ( MEK1(MAP2K1), MEK2(MAP2K2) )/ Mitogen-activated protein kinases 1-3 ( ERK1/2 ) pathway via v-Ha-ras Harvey rat sarcoma viral oncogene homolog ( H-RAS )- v-raf-1 murine leukemia viral oncogene homolog 1 ( c-Raf-1 ) regulation [8].

Other cAMP-binding guanine nucleotide exchange factors Rap guanine nucleotide exchange factor (GEF) 4 and 3 ( cAMP-GEFII, cAMP-GEFI ) promote cell proliferation via RAP1A, member of RAS oncogene family ( RAP-1A )/ v-raf murine sarcoma viral oncogene homolog B1 ( B-RAF )/ MEK1(MAP2K1), MEK2(MAP2K2)/ ERK1/2 pathway and inhibit c-Raf-1 signaling [9].


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