Mediates the translocation of RNA and DNA across the lysosomal membrane during RNA and DNA autophagy (RDA), a process in which RNA and DNA is directly imported into lysosomes in an ATP-dependent manner, and degraded (PubMed:27046251, PubMed:27846365, PubMed:28724756). Involved in the uptake of single-stranded oligonucleotides by living cells, a process called gymnosis (PubMed:28277980). In vitro, mediates the uptake of linear DNA more efficiently than that of circular DNA, but exhibits similar uptake efficacy toward RNA and DNA (PubMed:27846365). Binds long double-stranded RNA (dsRNA) (500 - 700 base pairs), but not dsRNA shorter than 100 bp (PubMed:26067272). Interacts with adapter protein complex 1 (AP-1) and AP-2, but not AP-3 and AP-4 (PubMed:28724756). Interacts with LAMP2 (PubMed:27046251). Mainly localizes to lysosomes and only partly to the plasma membrane (By similarity). Lysosomal localization is required for SIDT2-mediated intracellular degradation of endogenous RNA (PubMed:28724756). Widely expressed, including in the liver, brain and kidney (at protein level). Glycosylated. Knockout mice demonstrate a statistically significant departure from Mendel's law, but there is no significant differences in their weights or appearance as compared to wild-type controls as newborns. At 5 weeks of age, male mice show reduced weight and size as compared to control animals. This phenotype is not observed in females. Mutant animals exhibit increased fasting glucose levels and impaired glucose tolerance, probably due to impaired insulin granule exocytosis by pancreatic islet cells (PubMed:23776622). At 3 months of age, serum triglyceride and free fatty acid levels increase in knockout mice fed on normal chow. Mice gradually develop hepatic steatosis, with varying degrees of inflammatory changes (PubMed:27233614). Belongs to the SID1 family.