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This Article Full Text Full Text (PDF) All Versions of this Article: 293/4/F1054    most recent 00295.2007v1 Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in ISI Web of Science Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Yang, X. Articles by Preisig, P. A. Search for Related Content PubMed PubMed Citation Articles by Yang, X. Articles by Preisig, P. A.

RhoA required for acid-induced stress fiber formation and trafficking and activation of NHE3

Departments of ¹Internal Medicine and ²Physiology, University of Texas Southwestern Medical School, Dallas, Texas; and Departments of ³Internal Medicine and ⁴Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut

Submitted 26 June 2007 ; accepted in final form 6 August 2007

Exposure to an acid load increases apical membrane Na⁺/H⁺ antiporter (NHE3) activity, a process that involves exocytic trafficking of the transporter to the apical membrane. We have previously shown that an intact microfilament structure is required for this exocytic process (Yang X, Amemiya M, Peng Y, Moe OW, Preisig PA, Alpern RJ. Am J Physiol Cell Physiol 279: C410–C419, 2000). The present studies demonstrate that acid-induced stress fiber formation is required for stimulation of NHE3 activity. Formation of stress fibers is associated with acid-induced tyrosine phosphorylation and increases in protein abundance of two focal adhesion proteins, p125^FAK and paxillin. The Rho kinase inhibitor Y27632 completely blocks acid-induced stress fiber formation and the increases in apical membrane NHE3 abundance and activity, but it has no effect on acid-induced tyrosine phosphorylation of p125^FAK or paxillin. Herbimycin A completely blocks acid-induced tyrosine phosphorylation of p125^FAK and paxillin but only partially blocks stress fiber formation and NHE3 activation. These studies demonstrate that Rho kinase mediates acid-induced stress fiber formation, which is required for NHE3 exocytosis, and increases in NHE3 activity. Acid-induced tyrosine phosphorylation of the focal adhesion proteins p125^FAK and paxillin is not Rho kinase dependent. Thus these two acid-mediated effects are associated, yet independent processes.

OKP cells; Y27632; tyrosine phosphorylation; actin