To understand the mechanisms by which G protein-coupled signaling systems regulate NHE-1 in epithelial cells, we expressed Gα(q) and Gα13 in a renal epithelial cell line. We studied two signaling systems that have been implicated in NHE-1 regulation [intracellular Ca (Ca(i)) and phospholipase C activity] and measured NHE-1 activity, mRNA, and antigen. Expression of α(qWT) and α(qQ209L) (a GTPase-deficient mutant) increased basal Ca(i) and altered the kinetics of the bradykinin-induced Ca(i) signal. The initial bradykinin-induced spike in Ca(i) was prolonged and the plateau was higher in cells expressing α(qWT) and α(qQ209L) than in control cells. Cells expressing α(13WT) also had a higher basal Ca(i) and plateau after stimulation by bradykinin, but Ca release from intracellular stores was similar to that in control cells. Expression of all three α-chains increased NHE-1 activity, antigen, and mRNA. The αq(Q209L) had the greatest effect increasing activity by approximately twofold. The α(13WT) increased NHE-1 activity by ~1.5-fold, and α(qWT) increased activity 1.2-fold. These studies demonstrate that α(q) and α13 alter regulation of Ca(i) but by different mechanisms. The Ca signal or another signal generated by α(q) and α13 regulate(s) NHE-1 at the levels of activity, antigen, and mRNA.
ASJC Scopus subject areas
- Cell Biology