Phosphorylates phosphatidylinositol (PI) in the first committed step in the production of the second messenger inositol-1,4,5,-trisphosphate (PIP) (PubMed:9218477, PubMed:11526106). May regulate Golgi disintegration/reorganization during mitosis, possibly via its phosphorylation (By similarity). Involved in Golgi-to-plasma membrane trafficking (By similarity). a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol) + ATP = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol 4-phosphate) + ADP + H(+) Inhibited by wortmannin. Increased kinase activity upon interaction with NCS1/FREQ. Interacts with ARF1 and ARF3 in the Golgi complex, but not with ARF4, ARF5 or ARF6 (By similarity). Interacts with NCS1/FREQ in a calcium-independent manner. Interacts with CALN1/CABP8 and CALN2/CABP7; in a calcium-dependent manner; this interaction competes with NCS1/FREQ binding (PubMed:11526106). Interacts with ACBD3. Interacts with ARMH3, YWHAB, YWHAE, YWHAG, YWHAH, YWHAQ, YWHAZ and SFN (By similarity). Interacts with GGA2 (via VHS domain); the interaction is important for PI4KB location at the Golgi apparatus membrane (By similarity). Interacts with ATG9A (By similarity). Found in the outer membrane of mitochondria and membranes of the rough endoplasmic reticulum. Recruited to the Golgi complex by the small GTPase ARF to stimulate the synthesis of phosphatidylinositol 4,5-bisphosphate (PIP2) on the Golgi complex. Recruited to the Golgi apparatus membrane by ACBD3, GGA2 is also involved in the recruitment. Belongs to the PI3/PI4-kinase family. Type III PI4K subfamily.