title: Disrupted in renal carcinoma 2 (DIRC2), a novel transporter of the lysosomal membrane, is proteolytically processed by cathepsin L.
abstract: DIRC2 (Disrupted in renal carcinoma 2) has been initially identified as a breakpoint-spanning gene in a chromosomal translocation putatively associated with the development of renal cancer. The DIRC2 protein belongs to the MFS (major facilitator superfamily) and has been previously detected by organellar proteomics as a tentative constituent of lysosomal membranes. In the present study, lysosomal residence of overexpressed as well as endogenous DIRC2 was shown by several approaches. DIRC2 is proteolytically processed into a N-glycosylated N-terminal and a non-glycosylated C-terminal fragment respectively. Proteolytic cleavage occurs in lysosomal compartments and critically depends on the activity of cathepsin L which was found to be indispensable for this process in murine embryonic fibroblasts. The cleavage site within DIRC2 was mapped between amino acid residues 214 and 261 using internal epitope tags, and is presumably located within the tentative fifth intralysosomal loop, assuming the typical MFS topology. Lysosomal targeting of DIRC2 was demonstrated to be mediated by a N-terminal dileucine motif. By disrupting this motif, DIRC2 can be redirected to the plasma membrane. Finally, in a whole-cell electrophysiological assay based on heterologous expression of the targeting mutant at the plasma membrane of Xenopus oocytes, the application of a complex metabolic mixture evokes an outward current associated with the surface expression of full-length DIRC2. Taken together, these data strongly support the idea that DIRC2 is an electrogenic lysosomal metabolite transporter which is subjected to and presumably modulated by limited proteolytic processing.
authors.affiliation: Biochemical Institute, Christian-Albrechts-University, Kiel, Germany.
authors.forename: Lalu Rudyat Telly
authors.initials: LR
authors.lastname: Savalas
authors.forename: Bruno
authors.initials: B
authors.lastname: Gasnier
authors.forename: Markus
authors.initials: M
authors.lastname: Damme
authors.forename: Torben
authors.initials: T
authors.lastname: Lübke
authors.forename: Christian
authors.initials: C
authors.lastname: Wrocklage
authors.forename: Cécile
authors.initials: C
authors.lastname: Debacker
authors.forename: Adrien
authors.initials: A
authors.lastname: Jézégou
authors.forename: Thomas
authors.initials: T
authors.lastname: Reinheckel
authors.forename: Andrej
authors.initials: A
authors.lastname: Hasilik
authors.forename: Paul
authors.initials: P
authors.lastname: Saftig
authors.forename: Bernd
authors.initials: B
authors.lastname: Schröder
mesh_terms: D000818:Animals; D056668:Cathepsin L / Q000235:genetics / Q000378:metabolism*; D019295:Computational Biology; D004594:Electrophysiology; D019084:Fluorescent Antibody Technique, Indirect; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D047468:Immunoprecipitation; D051907:Lysosomal Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D014981:Xenopus
chemical_list: D051907:Lysosomal Membrane Proteins; D026901:Membrane Transport Proteins; D009363:Neoplasm Proteins; D056668:Cathepsin L