Probably involved in a TGF-beta pathway (PubMed:10887089). May be a receptor for TGF-beta-like ligand daf-7 (PubMed:10887089). Controls the decision of whether or not larvae enter a developmentally arrested state, known as dauer, in response to environmental conditions (PubMed:10887089). Involved in regulating entry into quiescence triggered by satiety (PubMed:18316030). Involved in sensitivity to CO2 levels (PubMed:18524955). In AWC neurons, acts to promote expression of srsx-3, a member of the GPCR family (PubMed:20713521). ATP + L-threonyl-[receptor-protein] = ADP + H(+) + O-phospho-L-threonyl-[receptor-protein] ATP + L-seryl-[receptor-protein] = ADP + H(+) + O-phospho-L-seryl-[receptor-protein] May interact with daf-4 to regulate dauer larva development. Head and ventral nerve cord from embryos to adults. Expressed in many sensory neurons. Subset of head neurons show coexpression with daf-4 when dauer/nondauer decision is made. Also expressed in non-neuronal cells: membraneous sheath surrounding the distal end of the intestine and in the distal tip cell of the gonad. All stages. Belongs to the protein kinase superfamily. TKL Ser/Thr protein kinase family. TGFB receptor subfamily.