Mediates the translocation of RNA and DNA across the lysosomal membrane during RNA and DNA autophagy (RDA), a process in which RNA or DNA is directly imported into lysosomes in an ATP-dependent manner, and degraded. Involved in the uptake of single-stranded oligonucleotides by living cells, a process called gymnosis (By similarity). In vitro, mediates the uptake of linear DNA more efficiently than that of circular DNA, but exhibits similar uptake efficacy toward RNA and DNA. Binds long double-stranded RNA (dsRNA) (500 - 700 base pairs), but not dsRNA shorter than 100 bp (By similarity). Interacts with adapter protein complex 1 (AP-1) and AP-2, but not AP-3 and AP-4 (By similarity). Interacts with LAMP2 (By similarity). 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 (By similarity). Highly expressed in the liver, brain, kidney and intestine (at protein level). Glycosylated. Belongs to the SID1 family.