Role of N-Linked Oligosaccharide Flexibility in Mannose Phosphorylation of Lysosomal Enzyme Cathepsin L

Warner, Jason; Thalhauser, Craig J.; Tao, Kai; Sahagian, G. Gary

doi:10.1074/jbc.m203097200

Cited by 24 publications

(13 citation statements)

References 29 publications

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“…This can be explained if some of the glycans have unfavorable locations on the surface of the hydrolase relative to the site of the protein recognition domains where GlcNAc-1-phosphotransferase docks. Presumably only glycans within a certain range of the docking site will be able to engage the catalytic elements of the transferase (34,35). We have previously speculated that binding of the ␥MRH domain to selected high mannose glycans with unfavorable locations may FIGURE 8.…”

Section: Discussionmentioning

confidence: 99%

Multiple Domains of GlcNAc-1-phosphotransferase Mediate Recognition of Lysosomal Enzymes

Meel¹,

Lee²,

Liu³

et al. 2016

Journal of Biological Chemistry

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The Golgi enzyme UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase), an ␣ 2 ␤ 2 ␥ 2 hexamer, mediates the initial step in the addition of the mannose 6-phosphate targeting signal on newly synthesized lysosomal enzymes. This tag serves to direct the lysosomal enzymes to lysosomes. A key property of GlcNAc-1-phosphotransferase is its unique ability to distinguish the 60 or so lysosomal enzymes from the numerous nonlysosomal glycoproteins with identical Asn-linked glycans. In this study, we demonstrate that the two Notch repeat modules and the DNA methyltransferase-associated protein interaction domain of the ␣ subunit are key components of this recognition process. Importantly, different combinations of these domains are involved in binding to individual lysosomal enzymes. This study also identifies the ␥-binding site on the ␣ subunit and demonstrates that in the majority of instances the mannose 6-phosphate receptor homology domain of the ␥ subunit is required for optimal phosphorylation. These findings serve to explain how GlcNAc-1-phosphotransferase recognizes a large number of proteins that lack a common structural motif.Correct targeting of newly synthesized acid hydrolases to lysosomes is essential for this organelle to maintain its function of degrading intracellular and endocytosed material. In higher eukaryotes, this process is mediated by the mannose 6-phosphate (Man-6-P) 5 recognition system whereby the newly synthesized acid hydrolases acquire Man-6-P residues in the Golgi that serve as high affinity ligands for binding to Man-6-P receptors (MPRs) in the trans-Golgi network and subsequent transport to the endo-lysosomal system (1). The initial and most critical step in the generation of the Man-6-P tag is mediated by the Golgi enzyme UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase). This enzyme binds selectively to conformation-dependent protein determinants in the 60 or so lysosomal acid hydrolases and transfers GlcNAc-1-P from UDP-GlcNAc to mannose residues on high mannose-type N-linked glycans of the hydrolases (2). The GlcNAc is subsequently excised by a second Golgi enzyme ("uncovering enzyme") to generate the high affinity Man-6-P ligand (3).GlcNAc-1-phosphotransferase is an ␣ 2 ␤ 2 ␥ 2 hexamer that is encoded by two genes (4 -7). The GNPTAB gene encodes the ␣ and ␤ subunits, whereas the GNPTG gene encodes the ␥ subunit. Enzyme kinetic studies have indicated that the ␣ and ␤ subunits specifically bind lysosomal acid hydrolases and mediate the catalytic function of the enzyme (8, 9). The ␥ subunit enhances the rate of GlcNAc-P transfer to a subset of the acid hydrolases without substantially altering the binding to these acceptors. Consistent with this, analysis of the level of mannose phosphorylation of the acid hydrolases in the brain of mice lacking the ␥ subunit, as estimated by the extent of binding to a cation-independent (CI)-MPR affinity resin, indicated that about one-third of the acid hydrol...

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Section: Discussionmentioning

confidence: 99%

Multiple Domains of GlcNAc-1-phosphotransferase Mediate Recognition of Lysosomal Enzymes

Meel¹,

Lee²,

Liu³

et al. 2016

Journal of Biological Chemistry

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“…Previous studies have reported that acid hydrolases with multiple N-linked glycans exhibit considerable variability in the extent of phosphorylation at the individual sites (44 -48). It has also been found that the introduction of new glycosylation sites on several acid hydrolases results in variable degrees of phosphorylation (24,49). These findings can be explained if the location of the N-linked glycans on the surface of the hydrolases varies relative to the position of the protein recognition domain.…”

Section: Discussionmentioning

confidence: 99%

Functions of the α, β, and γ Subunits of UDP-GlcNAc:Lysosomal Enzyme N-Acetylglucosamine-1-phosphotransferase

Qian

Lee

et al. 2010

Journal of Biological Chemistry

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UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase is an ␣ 2 ␤ 2 ␥ 2 hexamer that mediates the first step in the synthesis of the mannose 6-phosphate recognition marker on lysosomal acid hydrolases. Using a multifaceted approach, including analysis of acid hydrolase phosphorylation in mice and fibroblasts lacking the ␥ subunit along with kinetic studies of recombinant ␣ 2 ␤ 2 ␥ 2 and ␣ 2 ␤ 2 forms of the transferase, we have explored the function of the ␣/␤ and ␥ subunits. The findings demonstrate that the ␣/␤ subunits recognize the protein determinant of acid hydrolases in addition to mediating the catalytic function of the transferase. In mouse brain, the ␣/␤ subunits phosphorylate about one-third of the acid hydrolases at close to wild-type levels but require the ␥ subunit for optimal phosphorylation of the rest of the acid hydrolases. In addition to enhancing the activity of the ␣/␤ subunits toward a subset of the acid hydrolases, the ␥ subunit facilitates the addition of the second GlcNAc-P to high mannose oligosaccharides of these substrates. We postulate that the mannose 6-phosphate receptor homology domain of the ␥ subunit binds and presents the high mannose glycans of the acceptor to the ␣/␤ catalytic site in a favorable manner.In higher eukaryotes, newly synthesized acid hydrolases acquire mannose 6-phosphate (Man-6-P) 3 residues on their N-linked glycans as they traverse the Golgi (1). These residues serve as high affinity ligands for binding to Man-6-P receptors in the trans-Golgi network. The hydrolase-receptor complexes are then packaged into transport carriers for delivery to endosomes and lysosomes. The Man-6-P recognition marker is synthesized in two steps. First, UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase) binds to a conformation-dependent protein determinant on the acid hydrolase and transfers GlcNAc-1-P from UDP-GlcNAc to one or two of the mannose residues of the N-linked high mannose oligosaccharide. Second, N-acetylglucosamine 1-phosphodiester ␣-N-acetyglucosaminidase ("uncovering enzyme") excises the N-acetylglucosamine to generate the Man-6-P monoester.GlcNAc-1-phosphotransferase is a heterohexamer composed of three subunits (␣ 2 ␤ 2 ␥ 2 ) (2). The ␣ and ␤ subunits are encoded by a single gene GNPTAB, and the ␥ subunit is encoded by a separate gene GNPTG (3-5). Although it has been established that the ␣/␤ subunits contain the catalytic activity of the enzyme, the possible participation of these subunits in the recognition of the common protein determinant of the acid hydrolases has not been explored. Furthermore, the role(s) of the ␥ subunit is poorly understood. The initial insight into the function of the subunits came from studies of patients with the autosomal recessive lysosomal storage disorders termed mucolipidosis II (I-cell disease) and mucolipidosis III (pseudo-Hurler polydystrophy), the latter being the less severe of the two (6). These disorders arise from mutations in the genes encoding GlcNAc-1-phospho...

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“…If GNPTG would function in recognition of lysosomal hydrolases, its overexpression should impair sorting which subsequently results in hypersecretion of newly synthesized lysosomal enzymes into media. Because we have neither observed an increase in the secretion of metabolically labelled cathepsin D nor in the activities of three lysosomal enzymes in the media of GNPTG overexpressing cells, we hypothesize that GNPTG lacks the capability to bind to a conformation-dependent recognition domain present on the surface of many different lysosomal enzymes [24][25][26][27][28]. This hypothesis is supported by our previous studies demonstrating that no lysosomal enzymes could be eluted from a GNPTG affinity matrix [6].…”

Section: Accepted Manuscriptmentioning

confidence: 59%

Compensatory expression of human N-Acetylglucosaminyl-1-phosphotransferase subunits in mucolipidosis type III gamma

Pohl

Tiede

Castrichini

et al. 2009

Biochimica et Biophysica Acta (BBA) - Molecular Basis of Diseas

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The N-Acetylglucosaminyl-1-phosphotransferase plays a key role in the generation of mannose 6-phosphate (M6P) recognition markersessential for efficient transport of lysosomal hydrolases to lysosomes. The phosphotransferase is composed of six subunits (alpha2, beta2, gamma2). The alpha- and beta-subunits are catalytically active and encoded by a single gene, GNPTAB, whereas the gamma-subunit encoded by GNPTG is proposed to recognize conformational structures common to lysosomal enzymes. Defects in GNPTG cause mucolipidosis type III gamma, which is characterized by missorting and cellular loss of lysosomal enzymes leading to lysosomal accumulation of storage material. Using plasmon resonance spectrometry, we showed that recombinant gamma-subunit failed to bind the lysosomal enzyme arylsulfatase A. Additionally, the overexpression of the gamma-subunit in COS7 cells did not result in hypersecretion of newly synthesized lysosomal enzymes expected for competition for binding sites of the endogenous phosphotransferase complex. Analysis of fibroblasts exhibiting a novel mutation in GNPTG (c.619insT, p.K207IfsX7) revealed that the expression of GNPTAB was increased whereas in gamma-subunit overexpressing cells the GNPTAB mRNA was reduced. The data suggest that the gamma-subunit is important for the balance of phosphotransferase subunits rather for general binding of lysosomal enzymes.

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Role of N-Linked Oligosaccharide Flexibility in Mannose Phosphorylation of Lysosomal Enzyme Cathepsin L

Cited by 24 publications

References 29 publications

Multiple Domains of GlcNAc-1-phosphotransferase Mediate Recognition of Lysosomal Enzymes

Multiple Domains of GlcNAc-1-phosphotransferase Mediate Recognition of Lysosomal Enzymes

Functions of the α, β, and γ Subunits of UDP-GlcNAc:Lysosomal Enzyme N-Acetylglucosamine-1-phosphotransferase

Compensatory expression of human N-Acetylglucosaminyl-1-phosphotransferase subunits in mucolipidosis type III gamma

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