LD protein targeting: Depiction of four different types of LD-targeted proteins. Canonical class I (ERTOLD) and class II (CYTOLD) proteins are shown, as well as INTOLD and TERTOLD proteins. (A) The class I (ERTOLD) targeting. (B) Class II (CYTOLD) targeting. (C) Indirect LD association (INTOLD) by binding to another LD-resident protein. (D) TERTOLD targeting, which involves ER-anchored proteins that interact with LDs at ER–LD interfaces.