engleski

NME6, a member of the NME/NDPK family resides in complexes at the interface of mitochondrial inner membrane and matrix

The nucleoside diphosphate kinases (NDPK/NME/Nm23) are a family of enzymes catalyzing the transfer of gamma phosphate from NTPs to NDPs. The family consists of 10 members in human. The family is divided in two groups. Group I (NME1-NME4) members are highly homologous among themselves and exhibit NDPK activity. Studies of cytosolic NME1/2 and mitochondrial NME3/4 revealed the enzymatic activity mechanism, which depends on the phosphorylation of a specific histidine in the catalytic site, and requires NMEs to assemble as hexamers. Group II (NME5-NME9) members display less homology and seem to be NDPK inactive. Extensive research has been conducted on Group I members after the discovery of NME1’s role in metastasis suppression, while Group II remained largely unexplored. We focused our research on the barely explored Group II mitochondrial NME6 protein. We used immunofluorescence and live cell imaging together with time laps microscopy to confirm NME6 mitochondrial localization, and refined it using mitochondrial subfractionation. Fractionation of mitochondria by the swelling/shrinking procedure was analyzed by western blot and showed a NME6 distribution pattern highly similar to proteins of the matrix. It has also been revealed that overexpressing NME6 leads to downregulation of components oxidative phosphorylation chain. Although the proximity ligation assay indicated that NME6 forms complexes with mitochondrial proteins OPA1, NME4 and RCC1L the immunoprecipitation showed that the NME6 protein physically interacts only with RCC1L, a protein involved in coordination of the mitochondrial ribosome assembly. Together, these results provide precious clues for understanding the NME6 function and its possible impact on the respiratory chain and mitoribosomal translation and assembly.

Microscopy ; NME6 ; Mitochondria ; Matrix

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