Phospholipase C-β1 mediates α1-adrenergic receptor-stimulated activation of the sodium-hydrogen exchanger in Chinese hamster lung fibroblasts (CCL39)

The activation of the Na+-H+ exchanger 1 (NHE1) and extracellular-signal regulated kinase (ERK) phospho rylation in Chinese hamster lung fibroblasts (CCL39) was characterized in response to the specific alpha(1)-adrenergic agonist, phenylephrine (PE). Addition of 100 mu mol PE/L increased the steady-state intracellular pH (pH(i)) by 0.16 +/- 0.03 pH units, as well as increasing the phosphorylation of ERK. The response of NHE1 to PE in CCL39 cells was determined by the use of specific antagonists. Use of 2 specific chemical inhibitors of phosphoinositide-specific phospholipase C (PLC) reduced the ability of PE to activate either the exchanger or ERK. Studies were conducted in PLC beta-deficient cell lines derived from parental CCL39 cells. NHE1 activity in both mutant cell lines was increased in response to phorbal esters or lysophosphatidic acid, whereas the addition of PE only caused a minimal change in either pH(i) or ERK phosphorylation. These results, combined with reconstitution experiments with exogenously expressed PLC beta(1), PLC beta(2), or PLC beta(3), revealed that stimulation of NHE1 activity by PE in CCL39 cells is a PLC beta(1)-coupled event. Furthermore, the data indicate that alpha(1)-adrenergic signaling of PLC beta is upstream of ERK activation. These data demonstrate that PLC beta(1) is primarily involved in the activation of NHE1 in CCL39 fibroblasts.