Acts probably as a receptor for selective autophagosomal degradation of ubiquitinated targets. Homooligomer and heterooligomer. Interacts with SQSTM1, titin/TTN, TRIM55, RNF29, USP8, SQSTM1, MAP1LC3A, MAP1LC3B, MAP1LC3C, GABARAP, GABARAPL1 and GABARAPL2. Binds to ubiquitin and ubiquitinated proteins. In cardiac muscles localizes to the sarcomeric M line (By similarity). Is targeted to lysosomes for degradation (By similarity). Expressed in brain. The PB1 domain mediates interaction with SQSTM1.