May act as a scaffold to localize and regulate type I PI(4)P 5-kinases to specific compartments within the cell, where they generate PI(4,5)P2 for actin nucleation, signaling and scaffold protein recruitment and conversion to PI(3,4,5)P3. a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol 4-phosphate) + ATP = a 1,2-diacyl-sn-glycero-3-phospho-(1D-myo-inositol-4,5-bisphosphate) + ADP + H(+) Heterodimerizes with other type I phosphatidylinositol 4-phosphate 5-kinase. Localized to large cytoplasmic vesicular structures. It is unsure if the enzyme has intrinsic kinase activity.