Cation-independent Mannose 6-Phosphate Receptor

• Type of Material: Article
• Authors: Richard N. Bohnsack, Medical College of Wisconsin; Xuezheng Song, Emory University; Linda J. Olson, Medical College of Wisconsin; Mariko Kudo, Genzyme Corporation; Russell R. Gotschall, Genzyme Corporation; William M. Canfield, Genzyme Corporation; Richard Cummings, Emory University; David Smith, Emory University; Nancy M. Dahms, Medical College of Wisconsin
• Language: English
• Date: 2009-12-11
• Publisher: American Society for Biochemistry and Molecular Biology
• Publication Version: Final Published Version
• Copyright Statement: © 2009 by The American Society for Biochemistry and Molecular Biology, Inc.
• Final Published Version (URL): http://www.jbc.org/content/284/50/35215
• Title of Journal or Parent Work: Journal of Biological Chemistry
• ISSN: 0021-9258
• Volume: 284
• Issue: 50
• Start Page: 35215
• End Page: 35226
• Grant/Funding Information: This work was supported, in whole or in part, by National Institutes of Health Grants R01DK42667 (to N. M. D.) and GM085448 (to D. F. S.).
• Research Categories: Chemistry, Biochemistry

Abstract

The 300-kDa cation-independent mannose 6-phosphate receptor (CI-MPR), which contains multiple mannose 6-phosphate (Man-6-P) binding sites that map to domains 3, 5, and 9 within its 15-domain extracytoplasmic region, functions as an efficient carrier of Man-6-P-containing lysosomal enzymes. To determine the types of phosphorylated N-glycans recognized by each of the three carbohydrate binding sites of the CI-MPR, a phosphorylated glycan microarray was probed with truncated forms of the CI-MPR. Surface plasmon resonance analyses using lysosomal enzymes with defined N-glycans were performed to evaluate whether multiple domains are needed to form a stable, high affinity carbohydrate binding pocket. Like domain 3, adjacent domains increase the affinity of domain 5 for phosphomannosyl residues, with domain 5 exhibiting ∼60-fold higher affinity for lysosomal enzymes containing the phosphodiester Man-P-GlcNAc when in the context of a construct encoding domains 5–9. In contrast, domain 9 does not require additional domains for high affinity binding. The three sites differ in their glycan specificity, with only domain 5 being capable of recognizing Man-P-GlcNAc. In addition, domain 9, unlike domains 1–3, interacts with Man8GlcNAc2 and Man9GlcNAc2 oligosaccharides containing a single phosphomonoester. Together, these data indicate that the assembly of three unique carbohydrate binding sites allows the CI-MPR to interact with the structurally diverse phosphorylated N-glycans it encounters on newly synthesized lysosomal enzymes.