Mitophagy Antibody Sampler Kit

Background

Autophagy is a catabolic process for the autophagosome-lysosomal degradation of bulk cytoplasmic contents (1, 2). Selective autophagy targets the degradation of distinct sets of substrates and organelles (3-5). One of the best studied examples of selective autophagy involves the clearance of damaged mitochondria through a process called mitophagy. Several pathways have been described for various contexts of mitophagy, including the FUNDC1 pathway, the BNIP3 and BNIP3L/Nix pathway, and the PINK1/Parkin pathway. FUNDC1 is a mitochondrial protein that is phosphorylated by the autophagy kinase ULK1 and regulates hypoxia induced mitophagy (6, 7). BNIP3L/Nix and BNIP3 are members of the Bcl-2 family of apoptosis regulators that are expressed on mitochondria, induced by hypoxia, and have been shown to play a role in mitophagy (8). BNIP3L/Nix is also important in the autophagic maturation of erythroid cells (9). FUNDC1, BNIP3 and BNIP3L/Nix bind to LC3 family members, targeting the mitochondria to the autophagosome.

Non-hypoxic induction of mitophagy can be regulated by the PINK1/Parkin pathway, which plays causative roles in neurodegenerative disease, most notably Parkinson’s disease (10, 11). PINK1 is a mitochondrial serine/threonine kinase that is stabilized on the outer mitochondrial membrane of damaged mitochondria. Substrates of PINK1 include the E3 ubiquitin ligase Parkin and ubiquitin itself (12-14). Phosphorylation of Parkin as well as binding to phosphorylated ubiquitin leads to accumulation of ubiquitinated chains on multiple mitochondrial proteins. Ubiquitinated proteins are recognized by selective cargo receptors including SQSTM1/p62, Optineurin, and NDP52 (15-16). Autophagy cargo receptors contain an LC3-interacting region (LIR) required for binding to Atg8/LC3 family members and targeting to the autophagosome (3).