G alpha q and G alpha 13 regulate NHE-1 and intracellular calcium in epithelial cells.
To understand the mechanisms by which G protein-coupled signaling systems regulate NHE-1 in epithelial cells, we expressed G alpha q and G alpha 13 in a renal epithelial cell line. We studied two signaling systems that have been implicated in NHE-1 regulation [intracellular Ca (Cai) and phospholipase C activity] and measured NHE-1 activity, mRNA, and antigen. Expression of alpha qWT and alpha qQ209L (a GTPase-deficient mutant) increased basal Cai and altered the kinetics of the bradykinin-induced Cai signal. The initial bradykinin-induced spike in Cai was prolonged and the plateau was higher in cells expressing alpha qWT and alpha qQ209L than in control cells. Cells expressing alpha 13WT also had a higher basal Cai and plateau after stimulation by bradykinin, but Ca release from intracellular stores was similar to that in control cells. Expression of all three alpha-chains increased NHE-1 activity, antigen, and mRNA. The alpha qQ209L had the greatest effect increasing activity by approximately twofold. The alpha 13WT increased NHE-1 activity by approximately 1.5-fold, and alpha qWT increased activity 1.2-fold. These studies demonstrate that alpha q and alpha 13 alter regulation of Cai but by different mechanisms. The Ca signal or another signal generated by alpha q and alpha 13 regulate(s) NHE-1 at the levels of activity, antigen, and mRNA.
Kitamura
K
K
Department of Medicine, University of Texas, Southwestern Medical Center, Dallas 75235.
Singer
W D
WD
Cano
A
A
Miller
R T
RT
D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002461:Cell Line, Transformed; D004847:Epithelial Cells; D004848:Epithelium / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000737:chemistry / Q000502:physiology*; D007425:Intracellular Membranes / Q000378:metabolism*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D015290:Second Messenger Systems; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
D017923:Sodium-Hydrogen Exchangers; C069139:growth factor-activatable Na-H exchanger NHE-1; D019204:GTP-Binding Proteins; D002118:Calcium