2/15/2023 0 Comments Cccp project nova![]() Mitochondria of healthy cells continually divide and fuse with each other ( Hoppins et al., 2007). Inducible cleavage provides a mechanism for quality control because proteolytic inactivation of OPA1 promotes selective removal of defective mitochondrial fragments by preventing their fusion with the mitochondrial network. We conclude that a proteolytic cascade controls OPA1. Loss of membrane potential causes 60-kD protein to accumulate, suggesting that OMA1 is attenuated by proteolytic degradation. We also find that OMA1 is normally cleaved from 60 to 40 kD by another as of yet unidentified protease. We find that OMA1 small interfering RNA inhibits inducible cleavage, helps retain fusion competence, and slows the onset of apoptosis, showing that OMA1 controls OPA1 cleavage and function. In this study, we show that this inducible cleavage is mediated by a zinc metalloprotease called OMA1. Other isoforms are not cleaved by YME1L, but they are cleaved when mitochondria lose membrane potential or adenosine triphosphate. A subset of OPA1 isoforms is constitutively cleaved by YME1L. The mammalian mitochondrial inner membrane fusion protein OPA1 is controlled by complex patterns of alternative splicing and proteolysis.
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