The lysosomal membrane-export of metabolites and beyond

Lysosomes are degradative organelles in eukaryotic cells mediating the hydrolytic catabolism of various macromolecules to small basic building blocks. These low-molecular-weight metabolites are transported across the lysosomal membrane and reused in the cytoplasm and other organelles for biosynthetic pathways. Even though in the past 20 years our understanding of the lysosomal membrane regarding various transporters, other integral and peripheral membrane proteins, the lipid composition, but also its turnover has dramatically improved, there are still many unresolved questions concerning key aspects of the function of the lysosomal membrane. These include a possible function of lysosomes as a cellular storage compartment, yet unidentified transporters mediating the export such as various amino acids, mechanisms mediating the transport of lysosomal membrane proteins from the Golgi apparatus to lysosomes, and the turnover of lysosomal membrane proteins. Here, we review the current knowledge about the lysosomal membrane and identify some of the open questions that need to be solved in the future for a comprehensive and complete understanding of how lysosomes communicate with other organelles, cellular processes, and pathways.

Automated summary

Lysosomes are organelles in eukaryotic cells that degrade macromolecules into basic building blocks through hydrolysis, with the metabolites being reused in biosynthetic pathways. Despite advancements in understanding the lysosomal membrane, there are still unresolved questions regarding its function, including storage capabilities, unidentified transporters, protein transport mechanisms, and turnover processes. Further research is needed for a comprehensive understanding of lysosomal communication with other organelles and cellular pathways.