PTEN-L is a novel protein phosphatase for ubiquitin dephosphorylation to inhibit PINK1\u2013Parkin-mediated mitophagy

Liming Wang,Hayden Weng-Siong Tan,Guang Lu,Jingzi Zhang,Yueming Tang ,Boon‐Huat Bay ,Yihua Wu,Pornteera Pawijit,Jigang Wang,Mallilankaraman Karthik,Celestial T Yap,Yin Shi,Shuo Deng,Yih‐Cherng Liou ,Yan Tong,Yajun Wu,Yik-Lam Cho,Jung-Eun Park,Kah‐Leong Lim ,Siu Kwan Sze ,Ritu Chawla,Hanry Yu,Jianbin Zhang,Grace G.y Lim ,Chunxin Wang,Lei Fang,Hwang Ching Chan ,Han‐Ming Shen

doi:10.1038/s41422-018-0056-0

Abstract

Mitophagy is an important type of selective autophagy for specific elimination of damaged mitochondria. PTEN-induced putative kinase protein 1 (PINK1)-catalyzed phosphorylation of ubiquitin (Ub) plays a critical role in the onset of PINK1–Parkin-mediated mitophagy. Phosphatase and tensin homolog (PTEN)-long (PTEN-L) is a newly identified isoform of PTEN, with addition of 173 amino acids to its N-terminus. Here we report that PTEN-L is a novel negative regulator of mitophagy via its protein phosphatase activity against phosphorylated ubiquitin. We found that PTEN-L localizes at the outer mitochondrial membrane (OMM) and overexpression of PTEN-L inhibits, whereas deletion of PTEN-L promotes, mitophagy induced by various mitochondria-damaging agents. Mechanistically, PTEN-L is capable of effectively preventing Parkin mitochondrial translocation, reducing Parkin phosphorylation, maintaining its closed inactive conformation, and inhibiting its E3 ligase activity. More importantly, PTEN-L reduces the level of phosphorylated ubiquitin (pSer65-Ub) in vivo, and in vitro phosphatase assay confirms that PTEN-L dephosphorylates pSer65-Ub via its protein phosphatase activity, independently of its lipid phosphatase function. Taken together, our findings demonstrate a novel function of PTEN-L as a protein phosphatase for ubiquitin, which counteracts PINK1-mediated ubiquitin phosphorylation leading to blockage of the feedforward mechanisms in mitophagy induction and eventual suppression of mitophagy. Thus, understanding this novel function of PTEN-L provides a key missing piece in the molecular puzzle controlling mitophagy, a critical process in many important human diseases including neurodegenerative disorders such as Parkinson’s disease.

Highlights

Mitophagy is a selective form of autophagy for elimination of damaged mitochondria.[1]
Phosphatase and tensin homolog (PTEN)-L resides at the outer mitochondrial membrane PTEN-L, as a novel isoform of PTEN, translates from a noncanonical CUG initiation codon, with the addition of 173 amino acids to its N-terminus[33,34] (Fig. 1a)
In the topology assay using purified mitochondria from the HeLa cells stably expressing PTEN-L, PTEN-L was not protected from proteinase K, to Tom[20], an outer mitochondrial membrane (OMM) protein, and differently from Tim[23], Tim[44] and HSP60 that are known to localize at the outer surface of the inner membrane facing the inter-membranes space, inner surface of the mitochondrial membrane (IMM) and the mitochondrial matrix, respectively (Fig. 1d).[38]

Summary

Introduction

Mitophagy is a selective form of autophagy for elimination of damaged mitochondria.[1] Defective mitophagy is well known to be implicated in the pathogenesis of neurodegenerative disorders, in particular Parkinson’s disease.[2,3] The E3 ubiquitin (ligase Parkin (encoded by the PARK2 gene) and the serine/threonine kinase. It is believed that the dephosphorylation of ubiquitin is a more

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Results

Conclusion