Mannose 6-phosphate-independent Lysosomal Sorting of LIMP-2

Blanz J, Zunke F, Markmann S, Damme M, Braulke T, Saftig P, Schwake M (2015)

Publication Type: Journal article

Publication year: 2015

Journal

Traffic Wiley-Blackwell

Book Volume: 16

Pages Range: 1127-1136

Journal Issue: 10

DOI: 10.1111/tra.12313

Abstract

The widely accepted view that β-glucocerebrosidase (GC) is targeted to lysosomes by the lysosomal integral membrane protein type 2 (LIMP-2) independent of the mannose 6-phosphate (M6P) pathway has been recently challenged by the identification of a putative M6P residue in the crystalized LIMP-2 ectodomain. We demonstrate that LIMP-2 and GC reach lysosomes independent of the M6P pathway in fibroblasts and in purified liver lysosomes. Additionally, LIMP-2 could not be affinity-purified using M6P-specific antibodies. Our data prove M6P-independent lysosomal sorting of LIMP-2 and GC. The lysosomal integral membrane protein type 2 (LIMP-2/SCARB2) has been described as a mannose 6-phosphate (M6P)-independent trafficking receptor for β-glucocerebrosidase (GC). Recently, a putative M6P residue in a crystal structure of a recombinantly expressed LIMP-2 ectodomain has been reported. Based on surface plasmon resonance and fluorescence lifetime imaging analyses, it was suggested that the interaction of soluble LIMP-2 with the cation-independent M6P receptor (MPR) results in M6P-dependent targeting of LIMP-2 to lysosomes. As the physiological relevance of this observation was not addressed, we investigated M6P-dependent delivery of LIMP-2 to lysosomes in murine liver and mouse embryonic fibroblasts. We demonstrate that LIMP-2 and GC reach lysosomes independent of the M6P pathway. In fibroblasts lacking either MPRs or the M6P-forming N-acetylglucosamine (GlcNAc)-1-phosphotransferase, LIMP-2 still localizes to lysosomes. Immunoblot analyses also revealed comparable LIMP-2 levels within lysosomes purified from liver of wild-type (wt) and GlcNAc-1-phosphotransferase-defective mice. Heterologous expression of the luminal domain of LIMP-2 in wild-type, LIMP-2-deficient and GlcNAc-1-phosphotransferase-defective cells further established that the M6P modification is dispensable for lysosomal sorting of LIMP-2. Finally, cathepsin Z, a known GlcNAc-1-phosphotransferase substrate, but not LIMP-2, could be precipitated with M6P-specific antibodies. These data prove M6P-independent lysosomal sorting of LIMP-2 and subsequently GC in vivo.

Authors with CRIS profile

Friederike Zunke

Involved external institutions

Christian-Albrechts-Universität zu Kiel DE Germany (DE) Universitätsklinikum Hamburg-Eppendorf (UKE) DE Germany (DE) Universität Bielefeld DE Germany (DE)

How to cite

APA:

Blanz, J., Zunke, F., Markmann, S., Damme, M., Braulke, T., Saftig, P., & Schwake, M. (2015). Mannose 6-phosphate-independent Lysosomal Sorting of LIMP-2. Traffic, 16(10), 1127-1136. https://doi.org/10.1111/tra.12313

MLA:

Blanz, Judith, et al. "Mannose 6-phosphate-independent Lysosomal Sorting of LIMP-2." Traffic 16.10 (2015): 1127-1136.

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