Rho-dependent, Rho kinase-independent inhibitory regulation of Rac and cell migration by LPA1 receptor in Gi-inactivated CHO cells.
Lysophosphatidic acid (LPA) is a major serum lysophospholipid that stimulates cell migration in diverse cell types including ovarian cancer cells. We report here that in the absence of Gi function, LPA induces inhibition, rather than stimulation, of cellular Rac activity, lamellipodium formation, and cell migration in response to insulin like growth factor I (IGF-I) in Chinese hamster ovary (CHO) cells, which solely express LPA1 as a LPA receptor. The inhibitory effects of LPA are abrogated by the expression of either Galpha13 C-terminal peptide or C3 toxin pretreatment, but not a Rho kinase inhibitor. Without PTX pretreatment, LPA stimulates Rac and cell migration yet similarly activates Rho, indicating that Rho activation by itself is not sufficient for inhibition of cell migration. Conversely, the expression of a dominant negative Rac mutant sufficiently mimics the LPA inhibition of cell migration. LPA inhibits IGF I-induced Akt activation by only 40% in a manner dependent on Rho kinase. These results demonstrate that inhibition of Gi function converts LPA regulation on Rac and cell migration to an inhibitory mode, which is mediated by G13 and Rho but not Rho kinase, and raise a possibility of Gi as a new therapeutic target for LPA-dependent tumor progression.
Sugimoto
Naotoshi
N
Department of Physiology, Kanazawa University Graduate School of Medicine, 13-1 Takara-machi, Kanazawa 920-8640, Japan. ns@med.kanazawa-u.ac.jp
Takuwa
Noriko
N
Yoshioka
Kazuaki
K
Takuwa
Yoh
Y
D000199:Actins / Q000378:metabolism; D000818:Animals; D016466:CHO Cells / Q000166:cytology / Q000378:metabolism; D002465:Cell Movement / Q000502:physiology*; D006224:Cricetinae; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D006801:Humans; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids / Q000378:metabolism; D037342:Pertussis Toxin / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D011554:Pseudopodia / Q000378:metabolism; D049368:Receptors, Lysophosphatidic Acid / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D020764:cdc42 GTP-Binding Protein / Q000378:metabolism; D020744:rac GTP-Binding Proteins / Q000378:metabolism*; D020741:rho GTP-Binding Proteins / Q000378:metabolism*; D054460:rho-Associated Kinases
D000199:Actins; D047908:Intracellular Signaling Peptides and Proteins; D008246:Lysophospholipids; D049368:Receptors, Lysophosphatidic Acid; D007334:Insulin-Like Growth Factor I; D037342:Pertussis Toxin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D020764:cdc42 GTP-Binding Protein; D020744:rac GTP-Binding Proteins; D020741:rho GTP-Binding Proteins; C032881:lysophosphatidic acid