Nitrogen-containing-bisphosphonates (N-BPs) are widely prescribed to treat osteoporosis and other bone-related diseases. Although previous studies established that N-BPs function by inhibiting the mevalonate pathway in osteoclasts, the mechanism by which N-BPs enter the cytosol from the extracellular space to reach their molecular target is not understood. Here we implemented a CRISPRi-mediated genome-wide screen and identified SLC37A3 (solute carrier family 37 member A3) as a gene required for the action of N-BPs in mammalian cells. We observed that SLC37A3 forms a complex with ATRAID (all-trans retinoic acid-induced differentiation factor), a previously identified genetic target of N-BPs. SLC37A3 and ATRAID localize to lysosomes and are required for releasing N-BP molecules that have trafficked to lysosomes through fluid-phase endocytosis into the cytosol. Our results elucidate the route by which N-BPs are delivered to their molecular target, addressing a key aspect of the mechanism of action of N-BPs that may have significant clinical relevance.

CRISPRi_survival_screen_alendronate_K562Statistical information of all genes targeted in a CRISPRi mediated survival screen performed in human K562 cells using an osteoporosis drug, alendronate, as the selection agent. experimental procedures and statistical analyses are described in the manuscript.ZY_OSHEA_2018_supplementary_data_table_1.xlsxCRISPRi_survival_screen_zoledronate_K562statistical information of all genes targeted in a CRISPRi mediated survival screen performed in human K562 cells using an osteoporosis drug, zoledronate, as the selection agent. experimental procedures and statistical analyses are described in the manuscript.ZY_OSHEA_2018_supplementary_data_table_2.xlsx