title: A putative pH-dependent nuclear localization signal in the juxtamembrane region of c-Met.
abstract: The C-terminal fragment of the c-Met receptor tyrosine kinase is present in the nuclei of some cells irrespective of ligand stimulation, but the responsible nuclear localization signal (NLS) has not been previously reported. Here, we report that two histidine residues separated by a 10-amino-acid spacer (H1068-H1079) located in the juxtamembrane region of c-Met function as a putative novel NLS. Deletion of these sequences significantly abolished the nuclear translocation of c-Met, as did substitution of the histidines with alanines. This substitution also decreased the association of c-Met fragment with importin β. The putative NLS of c-Met is unique in that it relies on histidines, whose positive charge changes depending on pH, rather than the lysines or arginines, commonly found in classical bipartite NLSs, suggesting the possible 'pH-dependency' of this NLS. Indeed, decreasing the cytosolic pH either with nigericin, an Na(+)/H(+) exchanger or pH 6.5 KRB buffer significantly increased the level of nuclear c-Met and the interaction of the c-Met fragment with importin β, indicating that low pH itself enhanced nuclear translocation. Consistent with this, nigericin treatment also increased the nuclear level of endogenous c-Met in HeLa cells. The putative aberrant bipartite NLS of c-Met seems to be the first example of what we call a 'pH-dependent' NLS.
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Korea [2] Department of Biomedical Sciences, The Graduate School, Ajou University, Suwon, Korea.
authors.forename: Shubhash Chandra
authors.initials: SC
authors.lastname: Chaudhary
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Korea [2] Department of Biomedical Sciences, The Graduate School, Ajou University, Suwon, Korea.
authors.forename: Min-Guk
authors.initials: MG
authors.lastname: Cho
authors.affiliation: Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: Tuyet Thi
authors.initials: TT
authors.lastname: Nguyen
authors.affiliation: Department of Physiology, Yonsei University Wonju College of Medicine, Wonju, Korea.
authors.forename: Kyu-Sang
authors.initials: KS
authors.lastname: Park
authors.affiliation: Department of Microbiology, Ajou University School of Medicine, Suwon, Korea.
authors.forename: Myung-Hee
authors.initials: MH
authors.lastname: Kwon
authors.affiliation: 1] Department of Biochemistry and Molecular Biology, Ajou University School of Medicine, Suwon, Korea [2] Department of Biomedical Sciences, The Graduate School, Ajou University, Suwon, Korea.
authors.forename: Jae-Ho
authors.initials: JH
authors.lastname: Lee
mesh_terms: D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D006367:HeLa Cells; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D017434:Protein Structure, Tertiary; D019859:Proto-Oncogene Proteins c-met / Q000032:analysis* / Q000235:genetics / Q000378:metabolism*; D017384:Sequence Deletion
chemical_list: D019913:Nuclear Localization Signals; D019859:Proto-Oncogene Proteins c-met