Exp Mol Med.  2014 Oct;46(10):e119. 10.1038/emm.2014.67.

A putative pH-dependent nuclear localization signal in the juxtamembrane region of c-Met

• Chaudhary
• Cho MG
• Nguyen TT
• Park KS
• Kwon MH
• Lee JH

• KMID: 2155384
• DOI: http://doi.org/10.1038/emm.2014.67

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 beta. 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 beta, 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.

MeSH Terms

Active Transport, Cell Nucleus
Amino Acid Sequence
HeLa Cells
Humans
Hydrogen-Ion Concentration
Molecular Sequence Data
*Nuclear Localization Signals
Protein Structure, Tertiary
Proto-Oncogene Proteins c-met/*analysis/genetics/*metabolism
Sequence Deletion
Nuclear Localization Signals
Proto-Oncogene Proteins c-met