Cytoskeletal association of the A and B nucleoside diphosphate kinases of interphasic but not mitotic human carcinoma cell lines: specific nuclear localization of the B subunit.
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| Abstract |
The human A and B subunits of nucleoside diphosphate kinase (NDP kinase), encoded by the nm23-H1 and nm23-H2 genes, respectively, associate as homo- or heterohexamers to be catalytically active for the synthesis of nucleoside triphosphates. Despite 88% identity, they appear to possess specific functions. The nm23-H1 gene is implicated in tumor progression and metastasis, and the nm23-H2 gene product is a transcription factor for c-myc. To determine if these distinct functions reflect different subcellular localizations, the distribution of the A and B NDP kinases was analyzed by immunocytofluorescence microscopy in human breast cancer cell lines (MCF-7 and MDA-MB-231) using highly specific polyclonal and monoclonal antibodies. Interphasic cells exhibited a granular and filamentous cytoplasmic staining, particularly intense around nuclei, with both anti-NDP kinase A and B antibodies. The filamentous component observed with either anti-A or anti-B antibodies was altered in parallel to tubulin labeling with compounds interacting with microtubules, such as taxol and colchicine. Confirming published biochemical data, a partial colocalization with the vimentin network was observed in the MDA-231 cell line. A nuclear and nucleolar localization of NDP kinase B was shown by confocal microscopy which was not observed with the A enzyme. In dividing cells, NDP kinase labeling was punctiform and was not colocalized with the mitotic spindle. In conclusion, the A and B NDP kinases are similarly distributed in cytosol, associated partly to microtubules supporting a role in nucleotide channeling. Only the B enzyme is present in nuclei in accord with its role as a DNA binding protein. Their altered localization in dividing cells suggests colocalization with yet unidentified structures which are not intermediate filament aggregates.
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| Authors | V P Pinon, G Millot, A Munier, J Vassy, G Linares-Cruz, J Capeau, F Calvo, M L Lacombe |
| Journal | Experimental cell research (Exp Cell Res) Vol. 246 Issue 2 Pg. 355-67 (Feb 01 1999) ISSN: 0014-4827 [Print] United States |
| PMID | 9925751 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't) |
| Copyright | Copyright 1999 Academic Press. |
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