Molecular basis of selective mitochondrial fusion by heterotypic action between OPA1 and cardiolipin

Nature Cell Biology 19, 856 (2017). doi:10.1038/ncb3560 Authors: Tadato Ban, Takaya Ishihara, Hiroto Kohno, Shotaro Saita, Ayaka Ichimura, Katsumi Maenaka, Toshihiko Oka, Katsuyoshi Mihara & Naotada Ishihara Mitochondria are highly dynamic organelles that undergo frequent fusion and fission. Optic atrophy 1 (OPA1) is an essential GTPase protein for both mitochondrial inner membrane (IM) fusion and cristae morphology. Under mitochondria-stress conditions, membrane-anchored L-OPA1 is proteolytically cleaved to form peripheral S-OPA1, leading to the selection of damaged mitochondria for mitophagy. However, molecular details of the selective mitochondrial fusion are less well understood. Here, we showed that L-OPA1 and cardiolipin (CL) cooperate in heterotypic mitochondrial IM fusion. We reconstituted an in vitro membrane fusion reaction using purified human L-OPA1 protein expressed in silkworm, and found that L-OPA1 on one side of the membrane and CL on the other side are sufficient for fusion. GTP-independent membrane tethering through L-OPA1 and CL primes the subsequent GTP-hydrolysis-dependent fusion, which can be modulated by the presence of S-OPA1. These results unveil the most minimal intracellular membrane fusion machinery. In contrast, independent of CL, a homotypic trans-OPA1 interaction mediates membrane tethering, thereby supporting the cristae structure. Thus, multiple OPA1 functions are modulated by local CL conditions for regulation of mitochondria...
Source: Nature Cell Biology - Category: Cytology Authors: Tags: Letter Source Type: research