Marchesan, E. | bioRxiv Science

bioRxiv2023

Efficient Prohibitin 2 exposure during mitophagy depends on Voltage-dependent anion-selective channel protein 1.

Autophagic elimination of depolarized mitochondria (mitophagy) depends on Ubiquitin proteasome complex to expose the inner mitochondrial membrane-resident protein-Prohibitin 2 (PHB2). This uncovering facilitates its interaction with autophagosomal membrane-associated protein LC3. It remains unclear whether PHB2 is uncovered randomly through mitochondrial rupture sites. Prior knowledge and initial screening indicated that Voltage-dependent anion-selective channel protein 1 (VDAC1) might play a role in this process. Through in vitro biochemical assays and imaging, we have found that VDAC1-PHB2 interaction increases during mitochondrial depolarization. Subsequently, this interaction enhances the efficiency of PHB2 exposure and mitophagy. To investigate the relevance in vivo, we utilized a Porin (equivalent to VDAC1) knockout Drosophila line. Our findings demonstrate that during rotenone-induced mitochondrial stress, Porin is essential for PHB2 exposure, PHB2-LC3 interaction, and mitophagy. This study highlights that VDAC1 predominantly synchronizes efficient PHB2 exposure through mitochondrial rupture sites during mitophagy. These findings may provide insights to understand progressive neurodegeneration.

cell biology↗

bioRxiv2023

Activation of Ca2+ phosphatase Calcineurin regulates Parkin translocation to mitochondria and mitophagy

Selective removal of dysfunctional mitochondria via autophagy is crucial for the maintenance of cellular homeostasis. This event is initiated by the translocation of the E3 ubiquitin ligase Parkin to damaged mitochondria, and it requires the Serine/Threonine-protein kinase PINK1. In a coordinated set of events, PINK1 operates upstream of Parkin in a linear pathway that leads to the phosphorylation of Parkin, Ubiquitin, and Parkin mitochondrial substrates, to promote ubiquitination of outer mitochondrial membrane proteins. Ubiquitin decorated mitochondria are selectively recruiting autophagy receptors,which are required to terminate the organelle via autophagy. In this work we show a previously uncharacterized molecular pathway that correlates the activation of the Ca2+-dependent phosphatase Calcineurin to Parkin-dependent mitophagy. Calcineurin downregulation or genetic inhibition prevents Parkin translocation to CCCP-treated mitochondria, and impairs stress-induced mitophagy, whereas Calcineurin activation promotes Parkin mitochondrial recruitment and basal mitophagy. Calcineurin interacts with Parkin, and promotes Parkin translocation in the absence of PINK1, but requires PINK1 expression to execute mitophagy in MEF cells. Genetic activation of Calcineurin in vivo boosts basal mitophagy in neurons, and corrects locomotor dysfunction and mitochondrial respiratory defects of a Drosophila model of impaired mitochondrial functions. Our study identifies Calcineurin as a novel key player in the regulation of Parkin translocation and mitophagy.

cell biology↗