Protein kinase which is involved in the control of centrosome separation and bipolar spindle formation in mitotic cells and chromatin condensation in meiotic cells. Regulates centrosome separation (essential for the formation of bipolar spindles and high-fidelity chromosome separation) by phosphorylating centrosomal proteins such as CROCC, CEP250 and NINL, resulting in their displacement from the centrosomes. Regulates kinetochore microtubule attachment stability in mitosis via phosphorylation of NDC80. Involved in regulation of mitotic checkpoint protein complex via phosphorylation of CDC20 and MAD2L1. Plays an active role in chromatin condensation during the first meiotic division through phosphorylation of HMGA2. Phosphorylates: PPP1CC; SGO1; NECAB3 and NPM1. Essential for localization of MAD2L1 to kinetochore and MAPK1 and NPM1 to the centrosome. Phosphorylates CEP68 and CNTLN directly or indirectly (By similarity). NEK2-mediated phosphorylation of CEP68 promotes CEP68 dissociation from the centrosome and its degradation at the onset of mitosis (By similarity). Phosphorylates and activates NEK11 in G1/S-arrested cells. Involved in the regulation of centrosome disjunction (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Its catalytic activity is inhibited by the inhibitor CCT241950. In the presence of this inhibitor, displays an autoinhibited conformation: Tyr-70 side chain points into the active site, interacts with the activation loop, and blocks the alphaC helix. Forms homodimers and heterodimers. Interacts with CDC20, CTNB1, MAD1L1, MAD2L1, MAPK, NEK11, NPM1, NDC80, PCNT, PPP1CA, PPP1CC and SGO1. Interacts with STK3/MST2 (via SARAH domain) and SAV1 (via SARAH domain) (By similarity). Interacts with NECAB3 and HMGA2 (PubMed:14697346, PubMed:14668482). Interacts with CEP68; the interaction leads to phosphorylation of CEP68. Interacts with CNTLN; the interaction leads to phosphorylation of CNTLN. Interacts with CEP85 (By similarity). STK3/MST2 and SAV1 are required for its targeting to the centrosome. Colocalizes with SGO1 and MAD1L1 at the kinetochore. Not associated with kinetochore in the interphase but becomes associated with it upon the breakdown of the nuclear envelope. Has a nucleolar targeting/ retention activity via a coiled-coil domain at the C-terminal end (By similarity). Most abundantly expressed in testis. Low levels found in mid-gestation embryo, ovary, placenta, intestine, thymus and skin. Within the testis, expression restricted to germ cells with highest levels detected in spermatocytes at pachytene and diplotene stages. Also expressed in meiotic pachytene oocytes. The leucine-zipper domain is required for its dimerization and activation. Activated by autophosphorylation. Protein phosphatase 1 represses autophosphorylation and activation of isoform 1 by dephosphorylation. Phosphorylation by STK3/MST2 is necessary for its localization to the centrosome. Belongs to the protein kinase superfamily. NEK Ser/Thr protein kinase family. NIMA subfamily.