a Department of Physiology, Yong Loo Lin School of Medicine , National University of Singapore , Singapore.
b School of Chinese Medicine , Hong Kong Baptist University , Hong Kong , China.
Autophagy. 2018;14(11):2023-2025. doi: 10.1080/15548627.2018.1502565. Epub 2018 Sep 2.
Mitophagy is a main type of selective autophagy, via which damaged mitochondria are selectively degraded via the autophagic pathway. The protein kinase PINK1 and E3 ubiquitin ligase PRKN are the most well studied regulators of mitophagy, via a feedforward mechanism involving ubiquitin phosphorylation (p-Ser65-Ub) and accumulation at the damaged mitochondria. However, it is unknown whether there is a protein phosphatase against PINK1-mediated phosphorylation of ubiquitin. We recently reported that PTEN-L, a newly identified PTEN isoform, is a novel negative regulator of mitophagy through dephosphorylation of p-Ser65-Ub. Our data demonstrate that a significant portion of PTEN-L localizes at the outer mitochondrial membrane and is able to prevent PRKN's mitochondrial translocation, reduce the phosphorylation of PRKN, impair its E3 ligase activity as well as maintain PRKN in a closed/inactive status. Moreover, we found that PTEN-L dephosphorylates p-Ser65-Ub to disrupt the feedforward mechanism of mitophagy. Our findings suggest that PTEN-L acts as a brake in the regulation of mitophagy.
ATR: alternatively translated region; CCCP: carbonylcyanide 3-chlorophenylhydrazone; DUBs: deubiquitinating enzymes; MFN2: mitofusion2; MS/MS: tandem mass spectrometry; mtDNA: mitochondrial DNA; MTS: mitochondrial targeting sequences; O/A: oligomycin and antimycin A; PINK1: PTEN induced putative kinase 1; PRKN/parkin: parkin RBR E3 ubiquitin protein ligase; PTEN: phosphatase and tensin homolog; PTEN-L: phosphatase and tensin homolog-long; Ub: ubiquitin; USP: ubiquitin-specific proteases; YFP: yellow fluorescence protein.
自噬是一种选择性自噬的主要类型，通过该途径可以通过自噬途径选择性地降解受损的线粒体。蛋白激酶 PINK1 和 E3 泛素连接酶 PRKN 是通过涉及泛素磷酸化（p-Ser65-Ub）和在受损线粒体处积累的前馈机制对线粒体自噬的最有研究的调节剂。然而，尚不清楚是否存在针对 PINK1 介导的泛素磷酸化的蛋白磷酸酶。我们最近报道，PTEN-L，一种新鉴定的 PTEN 同工型，是通过去磷酸化 p-Ser65-Ub 来调节线粒体自噬的新型负调节剂。我们的数据表明，PTEN-L 的很大一部分定位于外线粒体膜上，能够阻止 PRKN 的线粒体易位，降低 PRKN 的磷酸化，损害其 E3 连接酶活性，并使 PRKN 保持关闭/非活性状态。此外，我们发现 PTEN-L 去磷酸化 p-Ser65-Ub 以破坏线粒体自噬的前馈机制。我们的研究结果表明，PTEN-L 作为线粒体自噬调节的制动器起作用。
ATR：替代翻译区；CCCP：羰基氰化物 3-氯苯腙；DUBs：去泛素化酶；MFN2：线粒体融合 2；MS/MS：串联质谱；mtDNA：线粒体 DNA；MTS：线粒体靶向序列；O/A：寡霉素和抗霉素 A；PINK1：PTEN 诱导的假定激酶 1；PRKN/帕金森病：Parkin RBR E3 泛素蛋白连接酶；PTEN：磷酸酶和张力蛋白同源物；PTEN-L：磷酸酶和张力蛋白同源物长；Ub：泛素；USP：泛素特异性蛋白酶；YFP：黄色荧光蛋白。
