title: G alpha12/G alpha13 subunits of heterotrimeric G proteins mediate parathyroid hormone activation of phospholipase D in UMR-106 osteoblastic cells.
abstract: PTH, a major regulator of bone remodeling and a therapeutically effective bone anabolic agent, stimulates several signaling pathways in osteoblastic cells. Our recent studies have revealed that PTH activates phospholipase D (PLD) -mediated phospholipid hydrolysis through a RhoA-dependent mechanism in osteoblastic cells, raising the question of the upstream link to the PTH receptor. In the current study, we investigated the role of heterotrimeric G proteins in mediating PTH-stimulated PLD activity in UMR-106 osteoblastic cells. Transfection with antagonist minigenes coding for small peptide antagonists to G alpha 12 and G alpha13 subunits of heterotrimeric G proteins prevented PTH-stimulated activation of PLD, whereas an antagonist minigene to G alphas failed to produce this effect. Effects of pharmacological inhibitors (protein kinase inhibitor, Clostridium botulinum exoenzyme C3) were consistent with a role of Rho small G proteins, but not of cAMP, in the effect of PTH on PLD. Expression of constitutively active G alpha12 and G alpha13 activated PLD, an effect that was inhibited by dominant-negative RhoA. The results identify G alpha12 and G alpha13 as upstream transducers of PTH effects on PLD, mediated through RhoA in osteoblastic cells.
authors.affiliation: Department of Molecular Pharmacology and Biological Chemistry, Northwestern University Feinberg School of Medicine, Chicago, Illinois 60611, USA.
authors.forename: A T K
authors.initials: AT
authors.lastname: Singh
authors.forename: A
authors.initials: A
authors.lastname: Gilchrist
authors.forename: T
authors.initials: T
authors.lastname: Voyno-Yasenetskaya
authors.forename: J M
authors.initials: JM
authors.lastname: Radeff-Huang
authors.forename: P H
authors.initials: PH
authors.lastname: Stern
mesh_terms: D002460:Cell Line; D005576:Colforsin / Q000494:pharmacology; D017868:Cyclic AMP-Dependent Protein Kinases / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000187:drug effects*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D044365:GTP-Binding Protein alpha Subunits, G12-G13 / Q000235:genetics / Q000502:physiology*; D015870:Gene Expression; D010006:Osteoblasts / Q000201:enzymology*; D010281:Parathyroid Hormone / Q000494:pharmacology*; D010739:Phospholipase D / Q000378:metabolism*; D014162:Transfection; D020742:rhoA GTP-Binding Protein / Q000502:physiology
chemical_list: D004791:Enzyme Inhibitors; D010281:Parathyroid Hormone; D005576:Colforsin; D017868:Cyclic AMP-Dependent Protein Kinases; D010739:Phospholipase D; D044365:GTP-Binding Protein alpha Subunits, G12-G13; D020742:rhoA GTP-Binding Protein