RhoA required for acid-induced stress fiber formation and trafficking and activation of NHE3.
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.
Yang
Xiaojing
X
Department of Internal Medicine, University of Texas Southwestern Medical School, Dallas, Texas, USA.
Huang
Hai-Chang
HC
Yin
Helen
H
Alpern
Robert J
RJ
Preisig
Patricia A
PA
D000577:Amides / Q000494:pharmacology; D000818:Animals; D016227:Benzoquinones / Q000494:pharmacology; D002460:Cell Line; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005089:Exocytosis / Q000502:physiology; D051417:Focal Adhesion Kinase 1 / Q000378:metabolism; D006851:Hydrochloric Acid / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D047029:Lactams, Macrocyclic / Q000494:pharmacology; D009893:Opossums; D051419:Paxillin / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D017828:Rifabutin / Q000031:analogs & derivatives; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D022502:Stress Fibers / Q000187:drug effects / Q000378:metabolism*; D014443:Tyrosine / Q000378:metabolism; D020742:rhoA GTP-Binding Protein / Q000378:metabolism*
D000577:Amides; D016227:Benzoquinones; D004791:Enzyme Inhibitors; D047029:Lactams, Macrocyclic; D051419:Paxillin; D011725:Pyridines; D000074083:Sodium-Hydrogen Exchanger 3; D017923:Sodium-Hydrogen Exchangers; C108830:Y 27632; D017828:Rifabutin; D014443:Tyrosine; C020754:herbimycin; D011505:Protein-Tyrosine Kinases; D051417:Focal Adhesion Kinase 1; D020742:rhoA GTP-Binding Protein; D006851:Hydrochloric Acid