PDF(Pubmed)
Abstract：
PPTC7 is a mitochondrial-localized phosphatase that suppresses BNIP3- and NIX-mediated mitophagy, but the mechanisms underlying this regulation remain ill-defined. Here, we demonstrate that loss of PPTC7 upregulates BNIP3 and NIX post-transcriptionally and independent of HIF-1α stabilization. Loss of PPTC7 prolongs the half-life of BNIP3 and NIX while blunting their accumulation in response to proteasomal inhibition, suggesting that PPTC7 promotes the ubiquitin-mediated turnover of BNIP3 and NIX. Consistently, overexpression of PPTC7 limits the accumulation of BNIP3 and NIX protein levels, which requires an intact catalytic motif but is surprisingly independent of its targeting to mitochondria. Consistently, we find that PPTC7 is dual-localized to the outer mitochondrial membrane and the matrix. Importantly, anchoring PPTC7 to the outer mitochondrial membrane is sufficient to blunt BNIP3 and NIX accumulation, and proximity labeling and fluorescence co-localization experiments demonstrate that PPTC7 dynamically associates with BNIP3 and NIX within the native cellular environment. Collectively, these data reveal that a fraction of PPTC7 localizes to the outer mitochondrial membrane to promote the proteasomal turnover of BNIP3 and NIX, limiting basal mitophagy.
摘要：
PPTC7是一种线粒体定位的磷酸酶，抑制BNIP3-和NIX介导的线粒体自噬，但这一监管背后的机制仍然不明确。这里,我们证明了PPTC7的丢失会在转录后上调BNIP3和NIX，并且与HIF-1α的稳定无关。PPTC7的丢失延长了BNIP3和NIX的半衰期，同时钝化了它们的积累以响应蛋白酶体抑制，提示PPTC7促进泛素介导的BNIP3和NIX的周转。始终如一，PPTC7的过表达限制了BNIP3和NIX蛋白水平的积累，这需要一个完整的催化基序，但令人惊讶地独立于其对线粒体的靶向。始终如一，我们发现PPTC7是双重定位于线粒体外膜和基质。重要的是,将PPTC7锚定到线粒体外膜足以钝化BNIP3和NIX的积累，以及邻近标记和荧光共定位实验表明，PPTC7在天然细胞环境中与BNIP3和NIX动态结合。总的来说，这些数据表明，PPTC7的一部分定位于线粒体外膜，以促进BNIP3和NIX的蛋白酶体更新，限制基底线粒体自噬。
