PGC-1α Determines the Formation of Neuronal Respiratory Chain Supercomplexes That Regulate Mitochondrial Function

Abstract

Loss of PGC-1α signaling is important in the development of experimental diabetic neuropathy (DN) [Choi J et al. Neurobiology of Disease, 2014. 64; 118-130]. In PGC- α knockout (KO) mice there is exacerbation of DN with loss of large and small myelinated fibers, loss of mitochondria (Mt) and DNA content, and increased protein oxidation. We have shown potential important functions of 35-kDa PGC-1α, a novel PGC-1α isoform in regulating Mt integrity. The focus of the present work was to analyze the respiratory chain complex integrity in neurons of PGC-1 α KO mice. In the respiratory supercomplexes of 1,030, 980, and 840 kDa, the levels of complexes 1,030 and 980 kDa are significantly decreased, while the level of 840-kDa complex is significantly increased in PGC-1 α KO mice compared to wild type (WT) mice. Mass spectrometry analysis identifies; (1) subunits of complex I, III, and IV in the 1,030-kDa band, 2) subunits of complex I and III in the 980-kDa band, and (3) subunits of complex I in the 840-kDa band. Quantification results reveal that the activities of complexes I, III, and IV within the 1,030-kDa protein complex are significantly decreased in PGC-1α KO mice. In contrast, we observe little complex I, III, and IV activities either in the 980- or 840-kDa complex. We observed altered Mt morphology and impaired respiration in PGC-1 α KO mice. Co-immunoprecipitation and mass spectrometry analyses reveal that the 35-kDa PGC-1α is associated with NADH dehydrogenase (ubiquinone) flavoprotein 2 (NDUFV2), a subunit of respiratory complex I in the Mt. Immunoblot analysis combined with two-dimensional-blue native gel show the presence of both 35-kD α PGC-1α and NDUFV2 proteins in the 1,030-kDa protein band. These results are consistent with a cooperative role of 35-kDa PGC-1α and NDUFV2 in the organization of Mt respiratory supercomplex assembly. The study provides evidence that 35-kDa PGC-1α is present in the Mt where it could directly regulate Mt function and affect response to diabetes. Disclosure J. Choi: None. M. Salimian: None. S. Konduru: None. J. Russell: None.