a member of the PI3/PI4 kinase family. Phosphorylates phosphatidylinositol (PI) in the first committed step in the production of the second messenger inositol- 1,4,5,-trisphosphate. 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-biphosphate (PIP2) on the Golgi complex. May regulate Golgi disintegration/reorganization during mitosis, possibly via its phosphorylation. Three splice-variant isoforms have been described. Note: This description may include information from UniProtKB.