May function in clathrin-mediated endocytosis. Has both a membrane binding/tubulating activity and the ability to recruit proteins essential to the formation of functional clathrin-coated pits. Has a preference for membranes enriched in phosphatidylserine and phosphoinositides and is required for the endocytosis of the transferrin receptor. May also bind tubulin. May play a role in the regulation of energy homeostasis. Interacts with proteins essential or regulating the formation of functional clathrin-coated pits (Probable). Interacts with CANX (By similarity). Interacts with AP2A1 (By similarity). Interacts with EPS15 (PubMed:26822536). Interacts with SH3GL3 (PubMed:15919751). Interacts with AMPH (PubMed:20946875). Interacts with ITSN1 (via SH3 domains) (PubMed:20946875). Interacts with and REPS1 (PubMed:20946875). Specifically expressed in brain. Genetic variation in SGIP1 is associated with fat mass and SGIP1 may be a determinant of obesity-related traits. Extended N-terminus.