Lysophagy and xenophagy. (a) During lysophagy, unknown lysosomal proteins are ubiquitinated and recognized by SQSTM1, which functions as a receptor, linking the damaged lysosomes with the LC3/GABARAP-conjugated sequestering membranes. LGALS3 binds to exposed lysosomal glycoproteins upon membrane rupture. A specific lysophagy mechanism remains to be elucidated. (b) In xenophagy, intracellular pathogens such as viruses and bacteria are recognized and ubiquitinated. SQSTM1, OPTN, CALCOCO2 and NBR1 have been described as receptor proteins.