Mice Lacking α/β Subunits of GlcNAc-1-Phosphotransferase Exhibit Growth Retardation, Retinal Degeneration, and Secretory Cell Lesions

Gelfman, Claire M.; Vogel, Peter; Issa, Tawfik; Turner, C. Alexander; Lee, Wang-Sik; Kornfeld, Stuart; Rice, Dennis S.

doi:10.1167/iovs.07-0452

Cited by 59 publications

(80 citation statements)

References 33 publications

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“…These results are consistent with the fact that the ␥ gene knock-out mice have a significantly milder phenotype than the ␣/␤ gene knock-out mice. While both types of knock-out mice have striking elevations of their serum acid hydrolases, the ␣/␤ gene knock-out mice are small and develop severe retinal degeneration that leads to blindness by 5 months of age whereas the ␥ gene knockout mice are of normal size and do not exhibit retinal degeneration (21). The findings are also in line with the genetic analysis of patients with ML II and ML III showing that mutations of the ␥ gene result in the milder ML III phenotype whereas mutations of the ␣/␤ gene can lead to either ML II or ML III (8 -17).…”

Section: Discussionmentioning

confidence: 99%

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Murine UDP-GlcNAc:Lysosomal Enzyme N-Acetylglucosamine-1-phosphotransferase Lacking the γ-Subunit Retains Substantial Activity toward Acid Hydrolases

Lee

Payne

Gelfman

et al. 2007

Journal of Biological Chemistry

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UDP-GlcNAc:lysosomal enzyme N-acetylglucosamine-1-phosphotransferase (GlcNAc-1-phosphotransferase) mediates the first step in the synthesis of the mannose 6-phosphate recognition marker on acid hydrolases. The transferase exists as an ␣ 2 ␤ 2 ␥ 2 hexameric complex with the ␣-and ␤-subunits derived from a single precursor molecule. The catalytic function of the transferase is attributed to the ␣-and ␤-subunits, whereas the ␥-subunit is believed to be involved in the recognition of a conformation-dependent protein determinant common to acid hydrolases. Using knock-out mice with mutations in either the ␣/␤ gene or the ␥ gene, we show that disruption of the ␣/␤ gene completely abolishes phosphorylation of high mannose oligosaccharides on acid hydrolases whereas knock-out of the ␥ gene results in only a partial loss of phosphorylation. These findings demonstrate that the ␣/␤-subunits, in addition to their catalytic function, have some ability to recognize acid hydrolases as specific substrates. This process is enhanced by the ␥-subunit.

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Section: Discussionmentioning

confidence: 99%

“…Mating between the heterozygous mice gave rise to homozygous animals. The characterization of the mutant mice will be described elsewhere (21).…”

Section: Methodsmentioning

confidence: 99%

Murine UDP-GlcNAc:Lysosomal Enzyme N-Acetylglucosamine-1-phosphotransferase Lacking the γ-Subunit Retains Substantial Activity toward Acid Hydrolases

Lee

Payne

Gelfman

et al. 2007

Journal of Biological Chemistry

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“…[21][22][23] This model is limited by the fact that early developmental processes cannot be followed in these animals due to intrauterine gestation. Kornfeld and colleagues 24,25 have also characterized a GNPTAB knockout mouse, which exhibits retinal degeneration, reduced size, and pathological lesions in several exocrine glands. Although chondrocytes from these mice were found to be hypertrophic and often distended, fibrocytes and mesenchymal cells did not develop the cytoplasmic vacuolar inclusions characteristically observed in human ML-II and ML-III patients.…”

Section: -15mentioning

confidence: 99%

Altered Chondrocyte Differentiation and Extracellular Matrix Homeostasis in a Zebrafish Model for Mucolipidosis II

Flanagan-Steet

Sias

Steet

2009

The American Journal of Pathology

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Mucolipidosis II (ML-II) is a pediatric disorder causedby defects in the biosynthesis of mannose 6-phosphate, the carbohydrate recognition signal responsible for targeting certain acid hydrolases to lysosomes. The mechanisms underlying the developmental defects of ML-II are largely unknown due in part to the lack of suitable animal models. To overcome these limitations, we developed a model for ML-II in zebrafish by inhibiting the expression of N-acetylglucosamine-1-phosphotransferase, the enzyme that initiates mannose 6-phosphate biosynthesis. Morphant embryos manifest craniofacial defects , impaired motility , and abnormal otolith and pectoral fin development. Decreased mannose phosphorylation of several lysosomal glycosidases was observed in morphant lysates, consistent with the reduction in phosphotransferase activity. Investigation of the craniofacial defects in the morphants uncovered striking changes in the timing and localization of both type II collagen and Sox9 expression , suggestive of an accelerated chondrocyte differentiation program. Accumulation of type II collagen was also noted within misshapen cartilage elements at later stages of development. Furthermore, we observed abnormal matrix formation and calcium deposition in morphant otoliths. Collectively, these data provide new insight into the developmental pathology of ML-II and suggest that altered production and/or homeostasis of extracellular matrix proteins are integral to the disease process. These findings highlight the potential of the zebrafish system in studying lysosomal disease pathogenesis.

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“…It has recently been reported that mice with disruption of the Gnptab gene exhibit many of the characteristic findings of patients with ML II, whereas mice with inactivation of the Gnptg gene have a much milder phenotype (10,11). Biochemical analysis showed that loss of the Gnptab gene products totally abolished the formation of the Man-6-P recognition marker on the acid hydrolases, whereas loss of the ␥ subunit decreased phosphorylation of the hydrolases to a variable extent, but in no instance was phosphorylation completely lost (12).…”

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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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Mice Lacking α/β Subunits of GlcNAc-1-Phosphotransferase Exhibit Growth Retardation, Retinal Degeneration, and Secretory Cell Lesions

Cited by 59 publications

References 33 publications

Murine UDP-GlcNAc:Lysosomal Enzyme N-Acetylglucosamine-1-phosphotransferase Lacking the γ-Subunit Retains Substantial Activity toward Acid Hydrolases

Murine UDP-GlcNAc:Lysosomal Enzyme N-Acetylglucosamine-1-phosphotransferase Lacking the γ-Subunit Retains Substantial Activity toward Acid Hydrolases

Altered Chondrocyte Differentiation and Extracellular Matrix Homeostasis in a Zebrafish Model for Mucolipidosis II

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

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