title: SH2 Ligand-Like Effects of Second Cytosolic Domain of Na/K-ATPase α1 Subunit on Src Kinase.
abstract: Our previous studies have suggested that the α1 Na/K-ATPase interacts with Src to form a receptor complex. In vitro binding assays indicate an interaction between second cytosolic domain (CD2) of Na/K-ATPase α1 subunit and Src SH2 domain. Since SH2 domain targets Src to specific signaling complexes, we expressed CD2 as a cytosolic protein and studied whether it could act as a Src SH2 ligand in LLC-PK1 cells. Co-immunoprecipitation analyses indicated a direct binding of CD2 to Src, consistent with the in vitro binding data. Functionally, CD2 expression increased basal Src activity, suggesting a Src SH2 ligand-like property of CD2. Consistently, we found that CD2 expression attenuated several signaling pathways where Src plays an important role. For instance, although it increased surface expression of Na/K-ATPase, it decreased ouabain-induced activation of Src and ERK by blocking the formation of Na/K-ATPase/Src complex. Moreover, it also attenuated cell attachment-induced activation of Src/FAK. Consequently, CD2 delayed cell spreading, and inhibited cell proliferation. Furthermore, these effects appear to be Src-specific because CD2 expression had no effect on EGF-induced activation of EGF receptor and ERK. Hence, the new findings indicate the importance of Na/K-ATPase/Src interaction in ouabain-induced signal transduction, and support the proposition that the CD2 peptide may be utilized as a Src SH2 ligand capable of blocking Src-dependent signaling pathways via a different mechanism from a general Src kinase inhibitor.
authors.affiliation: Marshall Institute for Interdisciplinary Research (MIIR), Marshall University, Huntington, West Virginia, United States of America.
authors.forename: Moumita
authors.initials: M
authors.lastname: Banerjee
authors.affiliation: Case Cardiovascular Research Institute, Department of Medicine, Case Western Reserve University School of Medicine and Harrington Heart and Vascular Institute, Cleveland, Ohio, United States of America.
authors.forename: Qiming
authors.initials: Q
authors.lastname: Duan
authors.affiliation: Marshall Institute for Interdisciplinary Research (MIIR), Marshall University, Huntington, West Virginia, United States of America.
authors.forename: Zijian
authors.initials: Z
authors.lastname: Xie
mesh_terms: D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D049109:Cell Proliferation; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006801:Humans; D018374:LLC-PK1 Cells; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000378:metabolism; D015398:Signal Transduction; D000254:Sodium-Potassium-Exchanging ATPase / Q000737:chemistry* / Q000378:metabolism*; D013552:Swine; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D008024:Ligands; D021122:Protein Subunits; D011993:Recombinant Fusion Proteins; D019061:src-Family Kinases; D048049:Extracellular Signal-Regulated MAP Kinases; D000254:Sodium-Potassium-Exchanging ATPase