Serine/threonine-protein kinase that regulates the mRNA translation machinery, probably by modulating the activity of translation factors such as eIF-4G and eIF-2 (PubMed:12225660). It may have some protein kinase activity instead of lipid kinase activity (PubMed:12225660). May play a role in P-granule degradation by autophagy in somatic cells during embryogenesis (PubMed:19377305). Required, during larval development, for the establishment of the proper number of germline progenitors, probably upstream of rsks-1 and ife-1 (PubMed:22278922). Required for larval development (PubMed:22278922). May act as a mediator of lifespan regulation by insulin signaling and nutrient sensing (PubMed:14668850, PubMed:28853436). ATP + L-seryl-[protein] = ADP + H(+) + O-phospho-L-seryl-[protein] ATP + L-threonyl-[protein] = ADP + H(+) + O-phospho-L-threonyl-[protein] Ubiquitous. Expressed in all major tissues and organs, including the intestine, gonads and hypodermal cells (PubMed:12225660). Expressed in neurons (PubMed:17327275). Defects strongly increase lifespan, the mean lifetime being of 25 days instead of 10 days, suggesting that it may be involved in aging process (PubMed:14668850). RNAi-mediated knockdown results in increased longevity and a reduced nucleoli size (PubMed:28853436). RNAi-mediated knockdown in a ncl-1 mutant background (e1942) reduces the increased longevity and suppresses the reduced nucleoli size of the let-363 single mutant, and reduces the increased ribosomal protein synthesis in the ncl-1 single mutant (e1942) (PubMed:28853436). RNAi-mediated knockdown in the germline causes sterility, a severe reduction in the number of germline progenitors and a delay in G2 phase of the cell cycle (PubMed:22278922). RNAi-mediated knockdown results in no sepa-1 containing aggregates at the comma stage of embryonic development indicative of no germ cell specific P-granules at this stage (PubMed:19377305). RNAi-mediated knockdown enhances the loss of touch receptor neurons in a mec-4 u231 mutant (PubMed:17327275). Belongs to the PI3/PI4-kinase family.