title: An extended proteome map of the lysosomal membrane reveals novel potential transporters.
abstract: Lysosomes are membrane-bound endocytic organelles that play a major role in degrading cell macromolecules and recycling their building blocks. A comprehensive knowledge of the lysosome function requires an extensive description of its content, an issue partially addressed by previous proteomic analyses. However, the proteins underlying many lysosomal membrane functions, including numerous membrane transporters, remain unidentified. We performed a comparative, semi-quantitative proteomic analysis of rat liver lysosome-enriched and lysosome-nonenriched membranes and used spectral counts to evaluate the relative abundance of proteins. Among a total of 2,385 identified proteins, 734 proteins were significantly enriched in the lysosomal fraction, including 207 proteins already known or predicted as endo-lysosomal and 94 proteins without any known or predicted subcellular localization. The remaining 433 proteins had been previously assigned to other subcellular compartments but may in fact reside on lysosomes either predominantly or as a secondary location. Many membrane-associated complexes implicated in diverse processes such as degradation, membrane trafficking, lysosome biogenesis, lysosome acidification, signaling, and nutrient sensing were enriched in the lysosomal fraction. They were identified to an unprecedented extent as most, if not all, of their subunits were found and retained by our screen. Numerous transporters were also identified, including 46 novel potentially lysosomal proteins. We expressed 12 candidates in HeLa cells and observed that most of them colocalized with the lysosomal marker LAMP1, thus confirming their lysosomal residency. This list of candidate lysosomal proteins substantially increases our knowledge of the lysosomal membrane and provides a basis for further characterization of lysosomal functions.
authors: Commissariat à l'Energie Atomique, Institut de Recherches en Technologies et Sciences du Vivant, Laboratoire Biologie à Grande Echelle, F-38054 Grenoble, France.
authors: Agnès
authors: A
authors: Chapel
authors: Sylvie
authors: S
authors: Kieffer-Jaquinod
authors: Corinne
authors: C
authors: Sagné
authors: Quentin
authors: Q
authors: Verdon
authors: Corinne
authors: C
authors: Ivaldi
authors: Mourad
authors: M
authors: Mellal
authors: Jaqueline
authors: J
authors: Thirion
authors: Michel
authors: M
authors: Jadot
authors: Christophe
authors: C
authors: Bruley
authors: Jérôme
authors: J
authors: Garin
authors: Bruno
authors: B
authors: Gasnier
authors: Agnès
authors: A
authors: Journet
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000378:metabolism; D015870:Gene Expression; D006367:HeLa Cells; D022781:Hepatocytes / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D007425:Intracellular Membranes / Q000737:chemistry*; D008099:Liver / Q000737:chemistry / Q000378:metabolism*; D051907:Lysosomal Membrane Proteins / Q000235:genetics / Q000378:metabolism; D008247:Lysosomes / Q000737:chemistry*; D008297:Male; D026901:Membrane Transport Proteins / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D008856:Microscopy, Fluorescence; D058977:Molecular Sequence Annotation; D020543:Proteome / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D052118:Lysosomal-Associated Membrane Protein 1
chemical_list: D015415:Biomarkers; D051907:Lysosomal Membrane Proteins; D026901:Membrane Transport Proteins; D020543:Proteome; C489116:LAMP1 protein, human; D052118:Lysosomal-Associated Membrane Protein 1