Required for the formation of endoplasmic reticulum-plasma membrane junctions and functions as an accessory protein for bridge- like lipid transfer protein BLTP1, participating in lipid delivery between endoplasmic reticulum and cell membranes (PubMed:40269155). Regulates the phagocytosis of Gram-negative bacteria like L. pneumophila and E. coli, as well as Gram-positive bacteria such as S. aureus (PubMed:31540829). {ECO:0000269|PubMed:31540829, ECO:0000269|PubMed:40269155}. This is the function of LTAP1 (lipid transport auxiliary protein 1, ENSG00000143612).