PTB domain-containing engulfment adapter protein 1, also known as GULP1, is an evolutionarily conserved adaptor protein required for efficient engulfment of apoptotic cells by phagocytes. GULP1 also helps modulate cellular glycosphingolipid and cholesterol transport. It also may play a role in the internalization and endosomal trafficking of various LRP1 ligands, such as PSAP. Increased cytoplasmic levels of GULP1 are associated with increases in cellular levels of GTP-bound ARF6.