title: Src-independent ERK signaling through the rat α3 isoform of Na/K-ATPase.
abstract: The Na/K-ATPase α1 polypeptide supports both ion-pumping and signaling functions. The Na/K-ATPase α3 polypeptide differs from α1 in both its primary structure and its tissue distribution. The expression of α3 seems particularly important in neurons, and recent clinical evidence supports a unique role of this isoform in normal brain function. The nature of this specific role of α3 has remained elusive, because the ubiquitous presence of α1 has hindered efforts to characterize α3-specific functions in mammalian cell systems. Using Na/K-ATPase α1 knockdown pig kidney cells (PY-17), we generated the first stable mammalian cell line expressing a ouabain-resistant form of rat Na/K-ATPase α3 in the absence of endogenous pig α1 detectable by Western blotting. In these cells, Na/K-ATPase α3 formed a functional ion-pumping enzyme and rescued the expression of Na/K-ATPase β1 and caveolin-1 to levels comparable with those observed in PY-17 cells rescued with a rat Na/K-ATPase α1 (AAC-19). The α3-containing enzymes had lower Na+affinity and lower ouabain-sensitive transport activity than their α1-containing counterparts under basal conditions, but showed a greater capacity to be activated when intracellular Na+was increased. In contrast to Na/K-ATPase α1, α3 could not regulate Src. Upon exposure to ouabain, Src activation did not occur, yet ERK was activated through Src-independent pathways involving PI3K and PKC. Hence, α3 expression confers signaling and pumping properties that are clearly distinct from that of cells expressing Na/K-ATPase α1.
authors.affiliation: Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia.
authors.forename: Namrata
authors.initials: N
authors.lastname: Madan
authors.affiliation: Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia.|Department of Natural Medicinal Chemistry, China Pharmaceutical University, Nanjing, China; and.
authors.forename: Yunhui
authors.initials: Y
authors.lastname: Xu
authors.affiliation: Gladstone Institute of Cardiovascular Disease, San Francisco, California.
authors.forename: Qiming
authors.initials: Q
authors.lastname: Duan
authors.affiliation: Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia.
authors.forename: Moumita
authors.initials: M
authors.lastname: Banerjee
authors.affiliation: Marshall Institute for Interdisciplinary Research, Marshall University, Huntington, West Virginia.
authors.forename: Isabel
authors.initials: I
authors.lastname: Larre
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: D000818:Animals; D002460:Cell Line; D049109:Cell Proliferation / Q000502:physiology; D015640:Ion Channel Gating / Q000502:physiology*; D007668:Kidney / Q000166:cytology / Q000378:metabolism*; D020935:MAP Kinase Signaling System / Q000502:physiology*; D020033:Protein Isoforms / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D012964:Sodium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism*; D013234:Stem Cells / Q000201:enzymology*; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D020033:Protein Isoforms; D012964:Sodium; D019061:src-Family Kinases; C499075:Atp1a1 protein, rat; D000254:Sodium-Potassium-Exchanging ATPase
keywords: Na+/K+-ATPase; Src; caveolin; extracellular‐signal‐regulated kinase (ERK); phosphatidylinositide 3‐kinase (PI 3‐kinase); signal transduction