Required for renal tubular integrity. ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Predominantly cytoplasmic. Defects in nek8 are the cause of polycystic kidney disease. Morpholino knockdown of the protein in the embryo causes ventral body curvature, pronephric cyst formation and laterality defects, including reversed heart looping. Belongs to the protein kinase superfamily. NEK Ser/Thr protein kinase family. NIMA subfamily.