PA24A, PKC-mu, G-protein beta/gamma, c-Src, PKC-alpha, H-Ras, MEK3(MAP2K3), 18.104.22.168, G-protein alpha-15, PKA-cat (cAMP-dependent), Adenylate cyclase type I, Elk-1, Adenosine extracellular region, G-protein alpha-i family, Erk (MAPK1/3), Rac1, AKT(PKB), IKK-alpha, IP3 receptor, CREB1, PtdIns(4,5)P2, PLC-beta3, PI3K cat class IB (p110-gamma), DAG, <endoplasmic reticulum lumen> Ca('2+) = <cytosol> Ca('2+), ATF-2, PREX1, I-kB, NF-kB, 22.214.171.124, 126.96.36.199, Shc, p38 MAPK, MEKK4(MAP3K4), c-Raf-1, SOS, PI3K reg class IB (p101), IP3, 188.8.131.52, GRB2, Arachidonic acid, Ca('2+) cytosol, IKK-beta, Adenosine A1 receptor, MEK1(MAP2K1), Ca('2+) endoplasmic reticulum lumen, cAMP, PKA-reg (cAMP-dependent), PKC-delta, MEK2(MAP2K2), IKK (cat), 1-Alkyl-2-arachidonoyl-glycerophosphocholine, PtdIns(3,4,5)P3
Adenosine A1 receptor signaling
Adenosine is a potent biological mediator that affects numerous cell types including neuronal cells, platelets, neutrophils and smooth muscle cells. Currently, four adenosine receptor subtypes have been identified: A1, A2A, A2B and A3. Adenosine receptors belong to the G-protein-coupled receptor family of cell surface receptors. Adenosine A1 receptor is a G-protein alpha-i and G-protein alpha-15 coupled receptor .
Adenosine A1 receptor interaction with the trimeric G-protein alpha/beta/gamma causes the exchange of GDP to GTP bound to G-protein alpha subunits and the dissociation of the beta/gamma heterodimers.
G-protein alpha-i inhibits activity of several Adenylate cyclase isoforms that leads to the decrease of cAMP level and attenuation of cAMP responsive element binding protein 1 ( CREB1 ) phosphorylation by Protein kinase, cAMP-dependent, catalytic ( PKA-cat (cAMP-dependent) ) .
Phospholipase C, beta 3 ( PLC-beta3 ) activation is coupled with Adenosine A1 receptor signaling via both G-protein alpha-15 and G-proteins beta/gamma subunits. PLC-beta3 catalyzes hydrolysis of phosphoinositide 4,5-bisphosphate ( PtdIns(4,5)P2 ) to form inositol 1,4,5-triphosphate ( IP3 ) and 1,2-diacyl-glycerol ( DAG ). The IP3 is then released into the cytoplasm and mobilizes Ca('2+) from internal stores, whereas DAG activates Protein kinase C delta ( PKC-delta ), which, stimulates Protein kinase D1 ( PKC-mu ) . PKC-mu plays an important role in the Adenosine A1 receptor signaling via activation of Inhibitor of kappa light polypeptide gene enhancer in B-cells, kinase beta ( IKK-beta)/ Nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor ( I-kB )/ Nuclear factor of kappa light polypeptide gene enhancer in B-cells ( NF-kB ) pathway .
DAG and Ca(II) can also activate Protein kinase C, alpha ( PKC-alpha ). PKC-alpha regulates Phospholipase A2, group IVA ( PA24A )-mediated Arachidonic acid release independently of MAP kinase .
G-proteins beta/gamma subunits and the lipid second messenger phosphatidylinositol (3,4,5)-trisphosphate ( PtdIns(3,4,5)P3 ) stimulate Phosphatidylinositol-3,4,5-trisphosphate-dependent Rac exchange factor 1 ( PREX1 ) Rac-GEF activity. PREX1 is a Ras-related C3 botulinum toxin substrate 1 ( Rac1 ) activator . Mitogen-activated protein kinase 14 ( P38 MAPK ) is activated by Rac1 via Mitogen-activated protein kinase kinase kinase 4 ( MEKK4(MAP3K4) )/ Mitogen-activated protein kinase kinase 3 ( MEK3(MAP2K3) ) pathway.
The G-protein beta/gamma heterodimers activate PI3K cat class IB, recruiting Phosphoinositide-3-kinase, regulatory subunit 5 ( PI3K reg class IB (p101) ) that activates Phosphoinositide-3-kinase, catalytic, gamma polypeptide ( PI3K cat class IB (p110-gamma) ). PI3K cat class IB (p110-gamma) converts phosphatidylinositol 4,5-biphosphate ( PtdIns(4,5)P2 ) to phosphatidylinositol 3,4,5-triphosphate ( PtdIns(3,4,5)P3 ) . PtdIns(3,4,5)P3 is a second messenger that directly binds via pleckstrin homology (PH) domen with V-akt murine thymoma viral oncogene homolog 1 ( AKT(PKB) ), that activates Conserved helix-loop-helix ubiquitous kinase ( IKK-alpha )/ I-kB/ NF-kB signaling .
The Adenosine A1 receptor activates Mitogen-activated protein kinase 1-3 ( ERK1/2 ) pathway via the activation of G-protein beta/gamma and v-src sarcoma (Schmidt-Ruppin A-2) viral oncogene homolog ( c-Src ). In turn, c-Src activates v-raf-1 murine leukemia viral oncogene homolog 1 ( c-Raf-1 )/ Mitogen-activated protein kinase kinases 1 and 2 ( MEK1(MAP2K1) MEK2(MAP2K2) )/ ERK1/2/ ELK1, member of ETS oncogene family ( ELK1 ) pathway via phosphorylation of adaptor protein SHC (Src homology 2 domain containing) transforming protein 1 ( Shc ), and recruitment of adaptor protein Growth factor receptor-bound protein 2 ( GRB2 ) and Son of sevenless homolog ( SOS ) .