Able to phosphorylate several exogenous substrates and to undergo autophosphorylation (PubMed:10421840). Negatively regulates cilium length in a cAMP and mTORC1 signaling-dependent manner (PubMed:25243405). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Phosphorylation appears to increase the enzymatic activity. Highly expressed in testis, and less in kidney, brain and lung. Autophosphorylated. Belongs to the protein kinase superfamily. CMGC Ser/Thr protein kinase family. CDC2/CDKX subfamily.