Essential for the regulation of ciliary length and required for the long-term survival of photoreceptors. Could have an important function in sensory cells and in spermatogenesis. May participate in signaling pathways used in visual and olfactory sensory transduction. Phosphorylates FZR1 in a cell cycle-dependent manner. Plays a role in the transcriptional coactivation of AR (By similarity). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Interacts with AR and CDK20. Found in a complex containing MAK, AR and NCOA3. Interacts with FZR1 (via WD repeats) (By similarity). Interacts with RP1. Localizes in both the connecting cilia and the outer segment axonemes. In pre- and postmeiotic male germ cells in testis. In photoreceptor cells of the retina and in the olfactory receptors, and in certain epithelia of the respiratory tract and choroid plexus (brain). On day 14 or 17 of embryonic development. Expression is observed in germ cells at the stages of late pachytene spermatocytes through to early round spermatids. Autophosphorylated. Phosphorylated on serine and threonine residues (By similarity). Mice are mostly fertile, develop normally, and exhibit no gross abnormalities and spermatogenesis is intact. However, both sperm motility and litter size is reduced. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.