Protein kinase which influences neuronal morphogenesis and polarity through effects on microtubules. Regulates microtubule acetylation in neurons. Contributes to prolactin-mediated phosphorylation of PXN and VAV2. Implicated in prolactin-mediated cytoskeletal reorganization and motility of breast cancer cells through mechanisms involving RAC1 activation and phosphorylation of PXN and VAV2. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Prolactin stimulates its activity. Interacts with PXN, PRLR, VAV1 and VAV2 and this interaction is prolactin-dependent. Up-regulated in malignant versus normal breast tissue. Isoform 2 shows a high level of expression in testis, ovary and brain. Phosphorylation at Thr-479 regulates its catalytic activity. Belongs to the protein kinase superfamily. NEK Ser/Thr protein kinase family. NIMA subfamily.