Endogenous RGS proteins attenuate Galpha(i)-mediated lysophosphatidic acid signaling pathways in ovarian cancer cells.
Lysophosphatidic acid is a bioactive phospholipid that is produced by and stimulates ovarian cancer cells, promoting proliferation, migration, invasion, and survival. Effects of LPA are mediated by cell surface G-protein coupled receptors (GPCRs) that activate multiple heterotrimeric G-proteins. G-proteins are deactivated by Regulator of G-protein Signaling (RGS) proteins. This led us to hypothesize that RGS proteins may regulate G-protein signaling pathways initiated by LPA in ovarian cancer cells. To determine the effect of endogenous RGS proteins on LPA signaling in ovarian cancer cells, we compared LPA activity in SKOV-3 ovarian cancer cells expressing G(i) subunit constructs that are either insensitive to RGS protein regulation (RGSi) or their RGS wild-type (RGSwt) counterparts. Both forms of the G-protein contained a point mutation rendering them insensitive to inhibition with pertussis toxin, and cells were treated with pertussis toxin prior to experiments to eliminate endogenous G(i/o) signaling. The potency and efficacy of LPA-mediated inhibition of forskolin-stimulated adenylyl cyclase activity was enhanced in cells expressing RGSi G(i) proteins as compared to RGSwt G(i). We further showed that LPA signaling that is subject to RGS regulation terminates much faster than signaling thru RGS insensitive G-proteins. Finally, LPA-stimulated SKOV-3 cell migration, as measured in a wound-induced migration assay, was enhanced in cells expressing Galpha(i2) RGSi as compared to cells expressing Galpha(i2) RGSwt, suggesting that endogenous RGS proteins in ovarian cancer cells normally attenuate this LPA effect. These data establish RGS proteins as novel regulators of LPA signaling in ovarian cancer cells.
Hurst
Jillian H
JH
Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602, United States.
Henkel
Paul A
PA
Brown
April L
AL
Hooks
Shelley B
SB
D000262:Adenylyl Cyclases / Q000378:metabolism; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000187:drug effects; D005576:Colforsin / Q000494:pharmacology; D000242:Cyclic AMP / Q000378:metabolism; D005260:Female; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000378:metabolism*; D006801:Humans; D008246:Lysophospholipids / Q000494:pharmacology*; D016296:Mutagenesis; D050505:Mutant Proteins / Q000378:metabolism; D010051:Ovarian Neoplasms / Q000201:enzymology / Q000473:pathology*; D037342:Pertussis Toxin / Q000494:pharmacology; D020033:Protein Isoforms / Q000378:metabolism; D020710:RGS Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D014945:Wound Healing / Q000187:drug effects
D008246:Lysophospholipids; D050505:Mutant Proteins; D020033:Protein Isoforms; D020710:RGS Proteins; D005576:Colforsin; D000242:Cyclic AMP; D037342:Pertussis Toxin; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D000262:Adenylyl Cyclases; C032881:lysophosphatidic acid