Plays a role in regulation of vesicular cargo transport from the trans-Golgi network (TGN) to the plasma membrane (PubMed:15107860). Regulates Golgi phosphatidylinositol 4-phosphate (PtdIns(4)P) levels and activates the PtdIns(4)P phosphatase activity of SACM1L when it binds PtdIns(4)P in 'trans' configuration (PubMed:30659099). Binds preferentially to PtdIns(4)P (PubMed:11001876, PubMed:15107860). Negatively regulates APOB secretion from hepatocytes (PubMed:30659099). {ECO:0000269|PubMed:11001876, ECO:0000269|PubMed:15107860, ECO:0000269|PubMed:30659099}. This is the function of ENSG00000116095 (PLEKHA3, pleckstrin homology domain containing A3).