期刊
BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH
卷 1868, 期 4, 页码 -出版社
ELSEVIER
DOI: 10.1016/j.bbamcr.2020.118942
关键词
ATP synthase; Cristae; Human mitochondria; Membrane protein; Organelle biogenesis; Protein complex
资金
- CNRS (Centre National de la Recherche Scientifique)
- Universite de Bordeaux
- Tunisian ministry for higher education and scientific research
The study provides molecular insights into the process of ATP synthase assembly through investigating the role of a human protein TMEM70. It reveals physical interactions between TMEM70 and Su.c, indicating TMEM70 oligomers act as a scaffold for c-ring assembly. Using super-resolution microscopy, the specific localization of TMEM70 at the inner cristae membrane is demonstrated, highlighting the assembly of mammalian ATP synthase within inner cristae membranes.
Mitochondrial ATP-synthesis is catalyzed by a F1Fo-ATP synthase, an enzyme of dual genetic origin enriched at the edge of cristae where it plays a key role in their structure/stability. The enzyme's biogenesis remains poorly understood, both from a mechanistic and a compartmentalization point of view. The present study provides novel molecular insights into this process through investigations on a human protein called TMEM70 with an unclear role in the assembly of ATP synthase. A recent study has revealed the existence of physical interactions between TMEM70 and the subunit c (Su.c), a protein present in 8 identical copies forming a transmembrane oligomeric ring (c-ring) within the ATP synthase proton translocating domain (Fo). Herein we analyzed the ATP-synthase assembly in cells lacking TMEM70, mitochondrial DNA or F1 subunits and observe a direct correlation between TMEM70 and Su.c levels, regardless of the status of other ATP synthase subunits or of mitochondrial bioenergetics. Immunoprecipitation, two-dimensional blue-native/SDS-PAGE, and pulse-chase experiments reveal that TMEM70 forms large oligomers that interact with Su.c not yet incorporated into ATP synthase complexes. Moreover, discrete TMEM70-Su.c complexes with increasing Su.c contents can be detected, suggesting a role for TMEM70 oligomers in the gradual assembly of the c-ring. Furthermore, we demonstrate using expansion super-resolution microscopy the specific localization of TMEM70 at the inner cristae membrane, distinct from the MICOS component MIC60. Taken together, our results show that TMEM70 oligomers provide a scaffold for c-ring assembly and that mammalian ATP synthase is assembled within inner cristae membranes.
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