Factors that might contribute concurrently to the selection of engulfed cargo are the following: (1) the relative abundance of cargo proteins influences the availability of cargo for engulfment by the expanding phagophore. (2) The timing and localization of phagophore biogenesis significantly restrict the available cargo for engulfment. (3) Direct or indirect binding of cargo to early autophagy machinery during phagophore formation can enhance cargo accessibility and in turn promote phagophore formation in proximity to cargo. The decoration of cargo with an "eat me" signal, recognized by an autophagy receptor, can facilitate phagophore recruitment to cargo proteins, aggregates, and/or organelles. Receptors, such as p62/SQSTM1, direct phagophore recruitment and can directly or indirectly promote autophagosome formation.
