Fig. 5.

Mitophagy. Fragmented mitochondria are more easily targeted for mitophagy, which can be initiated via parkin-dependent and -independent pathways. There is evidence that a diverse set of adaptor and receptor molecules (including NIX/BNIP3) and non-mitochondrial adaptors, such as OPTN, p62 and SQSTM1, help regulate mitochondrial number through mitophagy; however, the outer membrane signals that target specific mitochondria for degradation are not fully understood in the context of development. BNIP3, BCL2 interacting protein 3; NIX, NIP-3-like protein X (also known as BNIP3L); OPTN, optineurin; PINK1, PTEN induced kinase 1; SQSTM1, sequestosome 1.