ABSTRACT
LIMP-2 (also known as SCARB2) is an abundant lysosomal membrane protein. Previous studies have shown that LIMP-2 functions as a virus receptor, a chaperone for lysosomal enzyme targeting and a lipid transporter. The large luminal domain of LIMP-2 contains a hydrophobic tunnel that enables transport of phospholipids, sphingosine and cholesterol from the lysosomal lumen to the membrane. The question about the fate of the lipids after LIMP-2-mediated transport is largely unexplored. To elucidate whether LIMP-2 is present at contact sites between lysosomes and the endoplasmic reticulum (ER), we performed a proximity-based interaction screen. This revealed that LIMP-2 interacts with the endosomal protein STARD3 and the ER-resident protein VAPB. Using imaging and co-immunoprecipitation, we demonstrated colocalization and physical interaction between LIMP-2 and these proteins. Moreover, we found that interaction of LIMP-2 with VAPB required the presence of STARD3. Our findings suggest that LIMP-2 is present at ER–lysosome contact sites, possibly facilitating cholesterol transport from the lysosomal to the ER membrane. This suggests a novel mechanism for inter-organelle communication and lipid trafficking mediated by LIMP-2.
Footnotes
Author contributions
Conceptualization: J.K., P.S.; Methodology: S.R., S.H., Z.X.; Validation: S.R., D.N., C.H., J.K., P.S.; Formal analysis: B.R., P.S.; Investigation: S.R., S.H., Z.X., B.R., V.O., C.H.; Resources: E.C., D.N., P.S.; Data curation: E.C., B.R.; Writing - original draft: P.S.; Writing - review & editing: D.N., J.K., P.S.; Visualization: V.O., C.H.; Supervision: J.K., P.S.; Project administration: P.S.; Funding acquisition: P.S.
Funding
This work was partially supported by the Deutsche Forschungsgemeinschaft (DFG) through the Research Unit 2625 awarded to P.S. and J.K. Additionally, D.N. received support from a grant provided by the Ministry of Science and Technology of the People's Republic of China, grant no. 2021YFA1300301.
Data availability
Raw mass spectrometry data have been uploaded to the MassIVE public repository (https://massive.ucsd.edu) under accession number MSV000096477. All other data can be found within the article and its supplementary information.
