Probable UDP-glucose transmembrane transporter involved in UDP-glucose transport from the cytosol to the lumen of synaptic vesicles (PubMed:34269178). It is involved in platelet dense granules maturation (By similarity). {ECO:0000250|UniProtKB:Q8BGF8, ECO:0000269|PubMed:34269178}. Alternatively, could function as a molecular adapter enhancing the formation of the PI3KC3-C1/AIC/autophagy initiation complex to promote autophagy in dopaminergic neurons. Could also regulate the plasma membrane localization of the D(1A) dopamine receptor/DRD1 and dopamine signaling. . This is the function of SLC35D3 (solute carrier family 35 member D3, ENSG00000182747).