Growth Factors Induce Phosphorylation of the Na ⁺ /H ⁺ Antiporter, a Glycoprotein of 110 kD

Abstract

The Na+/H+ antiporter, which regulates intracellular pH in virtually all cells, is one of the best examples of a mitogen- and oncogene-activated membrane target whose activity rapidly changes on stimulation. The activating mechanism is unknown. A Na+/H+ antiporter complementary DNA fragment was expressed in Escherichia coli as a beta-galactosidase fusion protein, and a specific antibody to the fusion protein was prepared. Use of this antibody revealed that the Na+/H+ antiporter is a 110-kilodalton glycoprotein that is phosphorylated in growing cells. Mitogenic activation of resting hamster fibroblasts and A431 human epidermoid cells with epidermal growth factor, thrombin, phorbol esters, or serum, stimulated phosphorylation of the Na+/H+ antiporter with a time course similar to that of the rise in intracellular pH.

Convergence of integrin and growth factor receptor signaling pathways within the focal adhesion complex.

“…This antibody recognized proteins with apparent molecular weights of 110 kDa and 66 kDa from 1OT1/2 fibroblasts and bovine endothelial cells, respectively, when analyzed by immunoblotting or immunoprecipitation, as previously reported for other anti-Na+/H+ antiporter antibodies (Ross et al, 1990;Sardet et al, 1990). …”

Exclusion of the Na(+)-H+ antiporter as a candidate gene in human essential hypertension.

“…If Na + -H + exchange and SLC are indeed mediated by the same protein, 9 -13 these results suggest that elevated SLC must be mediated by secondary effects on the antiporter, either by alteration of the chemical gradient for Na + or H + or modification of the intrinsic activity of the antiporter, as for example, with phosphorylation. 30 A third possibility is that a distinct Na + -H + exchanger, encoded by an unlinked gene, mediates SLC in erythrocytes; no such isoforms of the antiporter have yet been identified. We have demonstrated the feasibility of the use of genetic linkage analysis to test the hypothesis that mutations in particular candidate genes contribute to the development of hypertension or other intermediate phenotypes.…”

Effect of NHE1 antisense gene transfection on the biological behavior of SGC-7901 human gastric carcinoma cells

“…Since the successful cloning of human NHE1cDNA in 1989 by the Sardet Laboratory [6] , the 8 known subtypes of NHE, named as NHE1-8 respectively, have been shown to be identical in structure and are related in function. These form the gene family of membrane exchange protein [7][8][9][10] .…”