PIP4K2A and Timothy syndrome: Thus, TS results in the activation of phosphatidylinositol-4-phosphate 5-kinase (PIPK), phospholipase D (PLD), and other lipid signaling molecules that accumulate, including phosphatidic acid, D-myo-inositol-1,4,5-trisphosphate (IP3) and phosphatidylinositol-4,5-bisphosphate (PIP2)49.