PO-261 Subcellular localization and expression of NME6, a member of the NME/Nm23/NDPK family, in human tumour cells

Introduction Nucleoside diphosphate kinases (NDPKs) catalyse the exchange of the terminal phosphate from trinucleotides to dinucleotides through a high-energy phosphohistidine intermedier. They are encoded by NME genes and have been found, with a few exceptions, in all living beings. Besides their well-known function as key regulators of the cellular nucleotide homeostasis, they have been appointed numerous additional biochemical and biological functions. The family consists of ten members. NME 1- NME 4, have been extensively studied, especially NME 1 in the context of metastasis formation. The NME 1- NME 4 are highly homologous among themselves and they all possess the NDP kinase activity in their hexameric form. The information on NME 5- NME 9 members is rather scarce but it is known that they display a lower level of mutual homology and apparently do not possess the NDP kinase activity. Their multimeric structure has not yet been revealed. The goal of our recent studies is revealing the subcelullar localization, structure and function of NME 6. Material and methods Subcellular localization has been approached by using a specific anti-NME6 antibody and transfection of an NME6-GFP vector followed by confocal microscopy. The results have been confirmed by cellular fractionation. The expression of NME 6 in human tumour cells was revealed by Western blotting with specific anti-NME6 antibodies. Results and discussions The results of immunofluorescent techniques revealed that NME6 colocalizes with mitochondria. The cellular fractioning confirmed these results. The endogenous NME6 was not detected in the nuclear or cytoplasmic fraction. NME 6 has a fairly strong expression in a panel of human melanoma cell lines and is HeLa cells, as well. Conclusion The mitochondrial localization of NME6 has been confirmed by three different methods although it is known that it does not possess the mitochondrial signalling sequence. The expression of NME 6 has been proven to be quite prominent. Since it has been shown that NME6 is an evolutionary very old gene it is obvious it has an important role in homeostasis of every living cell. Our future studies will be focused on revealing the precise localization of NME6 in the mitochondria and its role in cellular bioenergetics, the quaternary structure of the protein, its potential NDPK activity, its function in basic cellular processes and potential role in cancer onset and progression.