Positive regulator of mTOR signaling that functions by triggering the degradation of DEPTOR, an mTOR inhibitor. Involved in the dynamic regulation of mTOR signaling in chondrocyte differentiation during skeletogenesis (PubMed:30232230). Negatively regulates cAMP signaling pathway possibly by acting on CRTC2/TORC2 and CRTC3/TORC3 (Probable). Prevents HDAC4 translocation to the nucleus (By similarity). {ECO:0000250|UniProtKB:Q6P4S6, ECO:0000269|PubMed:30232230, ECO:0000305|PubMed:29211348}. This is the function of SIK3 (SIK family kinase 3, ENSG00000160584).