Domain 5 of the cation-independent mannose 6-phosphate receptor preferentially binds phosphodiesters (mannose 6-phosphate N-acetylglucosamine ester).

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Chavez CA, Bohnsack RN, Kudo M, Gotschall RR, Canfield WM, Dahms NM

Domain 5 of the cation-independent mannose 6-phosphate receptor preferentially binds phosphodiesters (mannose 6-phosphate N-acetylglucosamine ester).

Biochemistry. 2007 Nov 6;46(44):12604-17. Epub 2007 Oct 10.

PubMed ID

17927214 [ View in PubMed

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Abstract

The 300 kDa cation-independent mannose 6-phosphate receptor (CI-MPR) and the 46 kDa cation-dependent MPR (CD-MPR) are key components of the lysosomal enzyme targeting system that bind newly synthesized mannose 6-phosphate (Man-6-P)-containing acid hydrolases and divert them from the secretory pathway. Previous studies have mapped two high-affinity Man-6-P binding sites of the CI-MPR to domains 1-3 and 9 and one low-affinity site to domain 5 within its 15-domain extracytoplasmic region. A structure-based sequence alignment predicts that domain 5 contains the four conserved residues (Gln, Arg, Glu, Tyr) identified as essential for Man-6-P binding by the CD-MPR and domains 1-3 and 9 of the CI-MPR. Here we show by surface plasmon resonance (SPR) analyses of constructs containing single amino acid substitutions that these conserved residues (Gln-644, Arg-687, Glu-709, Tyr-714) are critical for carbohydrate recognition by domain 5. Furthermore, the N-glycosylation site at position 711 of domain 5, which is predicted to be located near the binding pocket, has no influence on the carbohydrate binding affinity. Endogenous ligands for the MPRs that contain solely phosphomonoesters (Man-6-P) or phosphodiesters (mannose 6-phosphate N-acetylglucosamine ester, Man-P-GlcNAc) were generated by treating the lysosomal enzyme acid alpha-glucosidase (GAA) with recombinant GlcNAc-phosphotransferase and uncovering enzyme (N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase). SPR analyses using these modified GAAs demonstrate that, unlike the CD-MPR or domain 9 of the CI-MPR, domain 5 exhibits a 14-18-fold higher affinity for Man-P-GlcNAc than Man-6-P, implicating this region of the receptor in targeting phosphodiester-containing lysosomal enzymes to the lysosome.

DrugBank Data that Cites this Article

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Alglucosidase alfa	Cation-dependent mannose-6-phosphate receptor	Protein	Humans	Yes	Binder	Details
N-Acetylglucosamine	N-acetylglucosamine-1-phosphodiester alpha-N-acetylglucosaminidase	Protein	Humans	Unknown	Not Available	Details