Loss of Drp1 function alters OPA1 processing and changes mitochondrial membrane organization.
RNAi mediated loss of Drp1 function changes mitochondrial morphology in cultured HeLa and HUVEC cells by shifting the balance of mitochondrial fission and fusion towards unopposed fusion. Over time, inhibition of Drp1 expression results in the formation of a highly branched mitochondrial network along with "bulge"-like structures. These changes in mitochondrial morphology are accompanied by a reduction in levels of Mitofusin 1 (Mfn1) and 2 (Mfn2) and a modified proteolytic processing of OPA1 isoforms, resulting in the inhibition of cell proliferation. In addition, our data imply that bulge formation is driven by Mfn1 action along with particular proteolytic short-OPA1 (s-OPA1) variants: Loss of Mfn2 in the absence of Drp1 results in an increase of Mfn1 levels along with processed s-OPA1-isoforms, thereby enhancing continuous "fusion" and bulge formation. Moreover, bulge formation might reflect s-OPA1 mitochondrial membrane remodeling activity, resulting in the compartmentalization of cytochrome c deposits. The proteins Yme1L and PHB2 appeared not associated with the observed enhanced OPA1 proteolysis upon RNAi of Drp1, suggesting the existence of other OPA1 processing controlling proteins. Taken together, Drp1 appears to affect the activity of the mitochondrial fusion machinery by unbalancing the protein levels of mitofusins and OPA1.
Möpert
Kristin
K
Silence Therapeutics AG, 13125 Berlin, Germany.
Hajek
Petr
P
Frank
Stephan
S
Chen
Christiane
C
Kaufmann
Jörg
J
Santel
Ansgar
A
D000818:Animals; D034281:Dynamins; D020558:GTP Phosphohydrolases / Q000235:genetics / Q000378:metabolism*; D055785:Gene Knockdown Techniques; D006367:HeLa Cells; D006801:Humans; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism; D008869:Microtubule-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism / Q000648:ultrastructure; D033681:Mitochondrial Membrane Transport Proteins; D051336:Mitochondrial Membranes / Q000378:metabolism / Q000648:ultrastructure; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D000091402:Prohibitins; D034622:RNA Interference; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism
D007527:Isoenzymes; D008565:Membrane Proteins; D026901:Membrane Transport Proteins; D008869:Microtubule-Associated Proteins; D033681:Mitochondrial Membrane Transport Proteins; D024101:Mitochondrial Proteins; C000717331:PHB2 protein, human; D000091402:Prohibitins; D034741:RNA, Small Interfering; D020558:GTP Phosphohydrolases; C470018:MFN2 protein, human; C415198:OPA1 protein, human; C470017:Mfn1 protein, human; C110768:DNM1L protein, human; D034281:Dynamins