title: Distinct pathways of ERK1/2 activation by hydroxy-carboxylic acid receptor-1.
abstract: Mechanistic investigations have shown that, upon agonist activation, hydroxy-carboxylic acid receptor-1(HCA1) couples to a Gi protein and inhibits adenylate cyclase activity, leading to inhibition of liberation of free fatty acid. However, the underlying molecular mechanisms for HCA1 signaling remain largely unknown. Using CHO-K1 cells stably expressing HCA1, and L6 cells, which endogenously express rat HCA1 receptors, we found that activation of ERK1/2 by HCA1 was rapid, peaking at 5 min, and was significantly blocked by pertussis toxin. Furthermore, time course experiments with different kinase inhibitors demonstrated that HCA1 induced ERK1/2 activation via the extracellular Ca2+, PKC and IGF-I receptor transactivation-dependent pathways. In addition, we observed that pretreated the cells with M119K, an inhibitor of Gβγ subunit-dependent signaling, effectively attenuated the ERK1/2 activation triggered by HCA1, suggesting a critical role for βγ-subunits in HCA1-activated ERK1/2 phosphorylation. Furthermore, the present results also indicated that the arrestin2/3 were not required for ERK1/2 activation. In conclusion, our findings demonstrate that upon binding to agonist, HCA1 receptors initially activate Gi, leading to dissociation of the Gβγ subunit from activated Gi, and subsequently induce ERK1/2 activation via two distinct pathways: one PKC-dependent pathway and the other IGF-IR transactivation-dependent pathway. Our results provide the first in-depth evidence that defines the molecular mechanism of HCA1-mediated ERK1/2 activation.
authors.affiliation: Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang, China.
authors.forename: Guo
authors.initials: G
authors.lastname: Li
authors.affiliation: Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang, China.
authors.forename: Hui-qian
authors.initials: HQ
authors.lastname: Wang
authors.affiliation: Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang, China.
authors.forename: Li-hui
authors.initials: LH
authors.lastname: Wang
authors.affiliation: Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang, China.
authors.forename: Ru-ping
authors.initials: RP
authors.lastname: Chen
authors.affiliation: Institute of Aging Research, School of Medicine, Hangzhou Normal University, Hangzhou, Zhejiang, China.
authors.forename: Jun-ping
authors.initials: JP
authors.lastname: Liu
mesh_terms: D000818:Animals; D019390:Arrestins / Q000378:metabolism; D016466:CHO Cells; D002352:Carrier Proteins / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D066246:ErbB Receptors / Q000378:metabolism; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D057809:HEK293 Cells; D020962:Heterotrimeric GTP-Binding Proteins / Q000378:metabolism; D006801:Humans; D019344:Lactic Acid / Q000494:pharmacology; D020935:MAP Kinase Signaling System; D009419:Nerve Tissue Proteins / Q000819:agonists / Q000235:genetics / Q000378:metabolism*; D037342:Pertussis Toxin / Q000494:pharmacology; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010739:Phospholipase D / Q000378:metabolism; D010766:Phosphorylation; D011493:Protein Kinase C / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D051381:Rats; D017526:Receptor, IGF Type 1 / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D010738:Type C Phospholipases / Q000378:metabolism; D019061:src-Family Kinases / Q000378:metabolism; D009687:Nuclear Proteins
chemical_list: D019390:Arrestins; D002352:Carrier Proteins; D066246:ErbB Receptors; D048049:Extracellular Signal-Regulated MAP Kinases; D020962:Heterotrimeric GTP-Binding Proteins; D019344:Lactic Acid; D009419:Nerve Tissue Proteins; D037342:Pertussis Toxin; D019869:Phosphatidylinositol 3-Kinases; D010739:Phospholipase D; D011493:Protein Kinase C; D017526:Receptor, IGF Type 1; D010738:Type C Phospholipases; D019061:src-Family Kinases; C484328:MAGEE1 protein, human; D009687:Nuclear Proteins; C082333:arrestin3; C512478:EGFR protein, human