NKF4

Novel kinase family 4 unites two clathrin-associated kinases, STK35 (CLIK1) and PDIK1L (CLIK1L), identified by their association with clathrin-coated structures. Both combine a catalytic domain with accessory regions that target them to membranes, and both remain poorly characterized at the level of substrates. STK35 has been reported at the nucleolus and at the basal body of ciliated cells, with proposed roles in ciliogenesis and cell-cycle control, whereas PDIK1L shows an intestinal-restricted expression pattern consistent with a specialized epithelial function. Neither enzyme has entered drug development, and recombinant NKF4 proteins are used for antibody validation, activity screening and localization studies in cultured cells.