Choline dehydrogenase interacts with SQSTM1/p62 to recruit LC3 and stimulate mitophagy

Abstract

CHDH (choline dehydrogenase) is an enzyme catalyzing the dehydrogenation of choline to betaine aldehyde in mitochondria. Apart from this well-known activity, we report here a pivotal role of CHDH in mitophagy. Knockdown of CHDH expression impairs CCCP-induced mitophagy and PARK2/parkin-mediated clearance of mitochondria in mammalian cells, including HeLa cells and SN4741 dopaminergic neuronal cells. Conversely, overexpression of CHDH accelerates PARK2-mediated mitophagy. CHDH is found on both the outer and inner membranes of mitochondria in resting cells. Interestingly, upon induction of mitophagy, CHDH accumulates on the outer membrane in a mitochondrial potential-dependent manner. We found that CHDH is not a substrate of PARK2 but interacts with SQSTM1 independently of PARK2 to recruit SQSTM1 into depolarized mitochondria. The FB1 domain of CHDH is exposed to the cytosol and is required for the interaction with SQSTM1, and overexpression of the FB1 domain only in cytosol reduces CCCP-induced mitochondrial degradation via competitive interaction with SQSTM1. In addition, CHDH, but not the CHDH FB1 deletion mutant, forms a ternary protein complex with SQSTM1 and MAP1LC3 (LC3), leading to loading of LC3 onto the damaged mitochondria via SQSTM1. Further, CHDH is crucial to the mitophagy induced by MPP+ in SN4741 cells. Overall, our results suggest that CHDH is required for PARK2-mediated mitophagy for the recruitment of SQSTM1 and LC3 onto the mitochondria for cargo recognition.

The E3 ubiquitin ligase NEDD4 is an LC3-interactive protein and regulates autophagy

“…Previous studies have shown that SQSTM1 is a central player in selective autophagy by interacting with ubiquitinated cargos or binding proteins, such as KEAP1 and CHDH (choline dehydrogenase), involved in mitophagy. 20,21,24,55,56 NEDD4-mediated ubiquitination may modulate molecular structure of SQSTM1 and lead to an increase in binding affinity to the ubiquitinated cargos or the binding proteins, thus to activate mitophagic process. Currently, we know little about NEDD4-mediated ubiquitination of SQSTM1 and the ubiquitination for function of SQSTM1 in autophhagy.…”

Pyruvate stimulates mitophagy via PINK1 stabilization

“…Moreover, pyruvate did not affect the mitophagy mediated by choline 309 dehydrogenase (CHDH), an important molecule for mitophagy [37] 310 (Fig. S5B).…”

“…Mitophagy is part of 37 a mitochondrial quality control system that coordinates mitochondrial 38 dynamics, biogenesis, fission, and fusion; mitophagy dysfunction is 39 thus associated with human diseases [1]. Two recessive Parkinson's 40 disease (PD) genes, PINK1/PARK6 and PARK2/parkin, are key regulators 41 of mitophagy.…”

“…To discover the novel factor(s) that regulate mitophagy, we 158 established a cell-based assay and performed a gain-of-function screen-159 ing by using 437 cDNAs encoding mitochondrial proteins, as described 160 in the Materials and methods section. HEK293T cells were co-161 transfected with an individual cDNA and Mito-GFP, a mito-tracker 162 [28], and were then exposed to a high dose of CCCP (100 μM) for a Because PDK4 is one of the pyruvate dehydrogenase kinases known 188 to inhibit PDC activity, we thought that PDK4-regulated pyruvate levels 189 might affect mitophagy. We found that PDK4 overexpression increased (Fig.…”

Optineurin inhibits NLRP3 inflammasome activation by enhancing mitophagy of renal tubular cells in diabetic nephropathy

“…Depolarization of the mitochondrial membrane potential stabilizes ubiquitin phosphatase and tensin homolog-induced putative kinase 1 on the outer mitochondrial membrane, and this leads to recruitment of optineurin (OPTN) and mitophagosome formation (25). Then, recruitment of the autophagic adaptor nucleoporin 62 (P62) to the damaged and ubiquitinated mitochondrial fragments leads to the clearance of mitochondrial fragments (26). Research indicates that concomitant accumulation of P62 in the mitochondrial component of mitophagosomes is indicative of insufficient mitophagy (27).…”