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Characterization of the Na+/H+ exchanger in human epidermoid carcinoma A431 vesicles

✍ Scribed by David Mancuso; Luis Glaser

Publisher: John Wiley and Sons
Year: 1985
Tongue: English
Weight: 699 KB
Volume: 123
Category: Article
ISSN: 0021-9541
DOI: 10.1002/jcp.1041230302

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✦ Synopsis

A previous report from this laboratory (Rothenberg et al., 1983a) demonstrated the presence of an Na+/H + exchanger in human epidermoid carcinoma A431 cells. We now characterize surfacederived membrane vesicles from this cell line which contain a functional Na+lH+ exchanger. The Na+/H+ exchanger in A431 vesicles shares a number of characteristics in common with previously described Na+/H+ exchangers including the following: (1) Na+ uptake is stimulated by an outward-directed pH gradient and inhibited by an inwarddirected pH gradient. (2) Na+ uptake is inhibited by arniloride and its analogs and their relative effectiveness is similar in vesicles and A431 cells. (3) The Na+/H+ exchanger uses Na+ o r Li+ as a substrate but not K + or Cs+. (4) H + efflux is stimulated by an inward-directed Na+ gradient and inhibited by t h e amiloride analog 5-Ndimethylamiloride. The Na+/H + exchanger in these membrane vesicles is activated allosterically by low intravesicular pH. The apparent pKa of the activating site is 6.4-6.6, characteristic of the N A + / H + exchanger before activation by mitogens.

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