title: Novel role of ATPase subunit C targeting peptides beyond mitochondrial protein import.
abstract: In mammals, subunit c of the F(1)F(0)-ATP synthase has three isoforms (P1, P2, and P3). These isoforms differ by their cleavable mitochondrial targeting peptides, whereas the mature peptides are identical. To investigate this apparent genetic redundancy, we knocked down each of the three subunit c isoform by RNA interference in HeLa cells. Silencing any of the subunit c isoforms individually resulted in an ATP synthesis defect, indicating that these isoforms are not functionally redundant. We found that subunit c knockdown impaired the structure and function of the mitochondrial respiratory chain. In particular, P2 silencing caused defective cytochrome oxidase assembly and function. Because the expression of exogenous P1 or P2 was able to rescue the respective silencing phenotypes, but the two isoforms were unable to cross-complement, we hypothesized that their functional specificity resided in their targeting peptides. In fact, the expression of P1 and P2 targeting peptides fused to GFP variants rescued the ATP synthesis and respiratory chain defects in the silenced cells. Our results demonstrate that the subunit c isoforms are nonredundant, because they differ functionally by their targeting peptides, which, in addition to mediating mitochondrial protein import, play a yet undiscovered role in respiratory chain maintenance.
authors.affiliation: Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, NY 10065, USA.
authors.forename: Cristofol
authors.initials: C
authors.lastname: Vives-Bauza
authors.forename: Jordi
authors.initials: J
authors.lastname: Magrané
authors.forename: Antoni L
authors.initials: AL
authors.lastname: Andreu
authors.forename: Giovanni
authors.initials: G
authors.lastname: Manfredi
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis; D000818:Animals; D015536:Down-Regulation; D003576:Electron Transport Complex IV / Q000378:metabolism; D015971:Gene Expression Regulation, Enzymologic; D020868:Gene Silencing; D005816:Genetic Complementation Test; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008928:Mitochondria / Q000201:enzymology* / Q000235:genetics; D025261:Mitochondrial Proton-Translocating ATPases / Q000235:genetics / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010455:Peptides / Q000378:metabolism*; D021382:Protein Sorting Signals; D021122:Protein Subunits / Q000235:genetics / Q000378:metabolism*; D021381:Protein Transport; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism
chemical_list: D007527:Isoenzymes; D010455:Peptides; D021382:Protein Sorting Signals; D021122:Protein Subunits; D012333:RNA, Messenger; D011994:Recombinant Proteins; D000255:Adenosine Triphosphate; D003576:Electron Transport Complex IV; D025261:Mitochondrial Proton-Translocating ATPases