Bcl-2-like protein 13 is a mammalian Atg32 homologue that mediates mitophagy and mitochondrial fragmentation

Tomokazu Murakawa,Yoshinori Ohsumi,Shigemiki Omiya,Ayako Hashimoto,Koji Okamoto,Hiroyuki Nakayama,Yasushi Sakata,Shungo Hikoso,Tomofumi Misaka,Ajay M Shah,Osamu Yamaguchi,Manabu Taneike,Toshihiro Takeda,Kinya Otsu,Yasushi Akazawa ,Keiya Nishida ,Hiroshi Ueda ,Akira Yamamoto ,Takahiro Oka ,Hirofumi Yasui

doi:10.1038/ncomms8527

Abstract

Damaged mitochondria are removed by mitophagy. Although Atg32 is essential for mitophagy in yeast, no Atg32 homologue has been identified in mammalian cells. Here, we show that Bcl-2-like protein 13 (Bcl2-L-13) induces mitochondrial fragmentation and mitophagy in mammalian cells. First, we hypothesized that unidentified mammalian mitophagy receptors would share molecular features of Atg32. By screening the public protein database for Atg32 homologues, we identify Bcl2-L-13. Bcl2-L-13 binds to LC3 through the WXXI motif and induces mitochondrial fragmentation and mitophagy in HEK293 cells. In Bcl2-L-13, the BH domains are important for the fragmentation, while the WXXI motif facilitates mitophagy. Bcl2-L-13 induces mitochondrial fragmentation in the absence of Drp1, while it induces mitophagy in Parkin-deficient cells. Knockdown of Bcl2-L-13 attenuates mitochondrial damage-induced fragmentation and mitophagy. Bcl2-L-13 induces mitophagy in Atg32-deficient yeast cells. Induction and/or phosphorylation of Bcl2-L-13 may regulate its activity. Our findings offer insights into mitochondrial quality control in mammalian cells.

Highlights

We show that Bcl2-L-13 induces mitochondrial fragmentation and mitophagy in mammalian cells and can function as a mitophagy receptor when it is expressed in yeast
We hypothesized that a mammalian mitophagy receptor will share the following molecular features with Atg[32]: mitochondrial localization; WXXL/I motifs; acidic amino acid clusters; and single membrane-spanning topology
In contrast to the previous report, overexpression of Bcl2-L-13 did not induce the activation of caspase 3 in HEK293 cells (Fig. 1b)

Summary

Introduction

We show that Bcl-2-like protein 13 (Bcl2-L-13) induces mitochondrial fragmentation and mitophagy in mammalian cells. Bcl2-L-13 binds to LC3 through the WXXI motif and induces mitochondrial fragmentation and mitophagy in HEK293 cells. In yeast[4] and mammalian cells[5], mitophagy is reported to be preceded by mitochondrial fission, which divides elongated mitochondria into pieces of manageable size for engulfment by isolation membrane. The OMM kinase, phosphatase and tensin homolog (PTEN)-induced putative kinase protein 1 (PINK1) and the cytosolic E3 ubiquitin ligase Parkin, the mutations of which are causative for hereditary Parkinson’s disease, are known to mediate mitophagy to eliminate damaged mitochondria in many types of cells[10]. We show that Bcl2-L-13 induces mitochondrial fragmentation and mitophagy in mammalian cells and can function as a mitophagy receptor when it is expressed in yeast

Methods

Results

Conclusion