title: Expression of rat Na-K-ATPase α2 enables ion pumping but not ouabain-induced signaling in α1-deficient porcine renal epithelial cells.
abstract: Na-K-ATPase is a fundamental component of ion transport. Four α isoforms of the Na-K-ATPase catalytic α subunit are expressed in human cells. The ubiquitous Na-K-ATPase α1 was recently discovered to also mediate signal transduction through Src kinase. In contrast, α2 expression is limited to a few cell types including myocytes, where it is coupled to the Na(+)/Ca(2+) exchanger. To test whether rat Na-K-ATPase α2 is capable of cellular signaling like its α1 counterpart in a recipient mammalian system, we used an α1 knockdown pig renal epithelial cell (PY-17) to create an α2-expressing cell line with no detectable level of α1 expression. These cells exhibited normal ouabain-sensitive ATPase, but failed to effectively regulate Src. In contrast to α1-expressing cells, ouabain did not stimulate Src kinase or downstream effectors such as ERK and Akt in α2 cells, although their signaling apparatus was intact as evidenced by EGF-mediated signal transduction. Additionally, α2 cells were unable to rescue caveolin-1. Unlike the NaKtide sequence derived from Na-K-ATPase α1, which downregulates basal Src activity, the corresponding α2 NaKtide was unable to inhibit Src in vitro. Finally, coimmunoprecipitation of cellular Src was diminished in α2 cells. These findings indicate that Na-K-ATPase α2 does not regulate Src and, therefore, may not serve the same role in signal transduction as α1. This further implies that the signaling mechanism of Na-K-ATPase is isoform specific, thereby supporting a model where α1 and α2 isoforms play distinct roles in mediating contraction and signaling in myocytes.
authors.affiliation: Department of Medicine, University of Colorado, Aurora, Colorado;
authors.forename: Joe
authors.initials: J
authors.lastname: Xie
authors.affiliation: Department of Physiology and Pharmacology, University of Toledo, Toledo, Ohio;
authors.forename: Qiqi
authors.initials: Q
authors.lastname: Ye
authors.affiliation: Department of Physiology and Pharmacology, University of Toledo, Toledo, Ohio;
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Cui
authors.affiliation: Department of Physiology and Pharmacology, University of Toledo, Toledo, Ohio;
authors.forename: Namrata
authors.initials: N
authors.lastname: Madan
authors.affiliation: Laboratory Animal Center, Chongqing Medical University, Chongqing, PR China; and.
authors.forename: Qiying
authors.initials: Q
authors.lastname: Yi
authors.affiliation: Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia.
authors.forename: Sandrine V
authors.initials: SV
authors.lastname: Pierre
authors.affiliation: Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia xiez@marshall.edu.
authors.forename: Zijian
authors.initials: Z
authors.lastname: Xie
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D051242:Caveolin 1 / Q000378:metabolism; D002460:Cell Line; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D016623:Ion Pumps / Q000378:metabolism*; D007668:Kidney / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology; D008969:Molecular Sequence Data; D010042:Ouabain / Q000494:pharmacology; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D051381:Rats; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D000254:Sodium-Potassium-Exchanging ATPase / Q000172:deficiency* / Q000378:metabolism; D013552:Swine; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D051242:Caveolin 1; D016623:Ion Pumps; D010042:Ouabain; D019061:src-Family Kinases; D051057:Proto-Oncogene Proteins c-akt; C498532:Atp1a2 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Src tyrosine kinase; membrane transporters; ouabain; rat Na-K-ATPase isoforms; signal transduction