Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P20645 (mannose-6-phosphate receptor)
 320 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have tried to characterize the intracellular compartments involved in the traffic of the thyroid prohormone thyroglobulin (Tg) from the site of storage, the follicular lumen, to the expected site(s) of proteolytic degradation, lysosomes. Electron microscope immunogold labeling with antibodies against Tg, cation-independent mannose-6-phosphate receptor (MPR), or arylsulfatase-A (ArS-A) was used to identify endocytic structures. The implication of these structures in the transport of Tg was analyzed by following the internalization and intracellular fate of Tg-colloidal gold complexes microinjected into the thyroid follicular lumen. Immunogold labeling was performed on ultrathin cryosections of intact pig tissue, in vitro reconstituted thyroid follicles (RTF), and isolated vesicles prepared by differential and isopycnic centrifugation. Microinjection experiments were carried out on RTF. Using double labeling for MPR and ArS-A, we characterized three types of structures: those slightly positive for MPR and ArS-A, those strongly positive for both markers, and those only positive for ArS-A. These compartments exhibited the properties of early endosomes (EE), late endosomes (LE), and lysosomes (L), respectively. Tg immunoreactivity was high in EE, low in LE, and undetectable in L. Similar morphological and immunochemical characteristics of EE, LE, and L were found in intact tissue, RTF, and isolated vesicles. Tg-gold complexes microinjected into the lumen of RTF were efficiently internalized within 5 min into structures with the appearance of EE. Sixty minutes after the injection, Tg-gold complexes were detected into LE and L. We present here the first direct experimental evidence for an involvement of endosomal compartments in the Tg internalization/degradation pathway. The data indicate that internalized Tg molecules are transported to EE and then transferred from EE to LE.
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PMID:Thyroglobulin internalized by thyrocytes passes through early and late endosomes. 191 1

We have studied the intracellular fate of the apolipoprotein B of copper-oxidized LDL in cultured J774 macrophages, using subcellular fractionation and immunofluorescence techniques. The oxidized apolipoprotein B, using cell fractionation, was located primarily in secondary lysosomes (identified using the lysosomal marker-enzyme aryl sulfatase). Light microscopy using antibodies to the mannose-6-phosphate receptor, the lysosomal membrane protein lgp 120, and oxidized LDL (biotinylated) confirmed that apo B of oxidized LDL did accumulate in secondary lysosomes rather than in endosomes. We conclude from these results that the oxidized apolipoprotein B of LDL reaches the secondary lysosomes, but is not efficiently degraded, leading to intracellular accumulation within this compartment. If this occurs in vivo it may influence the physiology of the macrophage and their subsequent roles in forming foam cells and the development of the fatty streaks of early atherosclerosis.
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PMID:Apolipoprotein B of oxidized LDL accumulates in the lysosomes of macrophages. 815 30

Mucopolysacchariodosis type VI (MPS VI) is the lysosomal storage disorder caused by the deficient activity of arylsulfatase B (ASB; N-acetylgalactosamine 4-sulfatase) and the subsequent accumulation of the glycosaminoglycan (GAG), dermatan sulfate. In this study, a retroviral vector containing the full-length human ASB cDNA was constructed and used to transduce skin fibroblasts, chondrocytes, and bone marrow cells from human patients, cats, or rats with MPS VI. The ASB vector expressed high levels of enzymatic activity in each of the cell types tested and, in the case of cat and rat cells, enzymatic expression led to complete normalization of 35SO4 incorporation. In contrast, overexpression of ASB in human MPS VI skin fibroblasts did not lead to metabolic correction. High-level ASB expression was detected for up to eight weeks in transduced MPS VI cat and rat bone marrow cultures, and PCR analysis demonstrated retroviral-mediated gene transfer to approximately 30-50% of the CFU GM-derived colonies. Notably, overexpression of ASB in bone marrow cells led to release of the enzyme into the media and uptake by MPS VI cat and rat skin fibroblasts and/or chondrocytes via the mannose-6-phosphate receptor system, leading to metabolic correction. Thus, these studies provide important rationale for the development of gene therapy for this disorder and lay the frame-work for future in vivo studies in the animal model systems.
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PMID:Arylsulfatase B activities and glycosaminoglycan levels in retrovirally transduced mucopolysaccharidosis type VI cells. Prospects for gene therapy. 875 62

Mucopolysaccharidosis type VI (MPS VI) is an autosomal recessive lysosomal storage disorder characterised by the deficiency of N-acetylgalactosamine 4-sulfatase (4S). MPS VI has also been described in the cat. As an initial step toward muscle-mediated gene therapy in the MPS VI cat, we have made two retroviral constructs (pLf4S and pLf4SSN) that transduce the feline 4S gene. Both constructs were designed to express the feline 4S sequence from the viral long terminal repeat promoter. In addition pLf4SSN expressed the neomycin resistance gene from the SV40 early promoter. Amphotrophic virus was produced for each construct and used to transduce feline MPS VI myoblasts. Lf4S- and Lf4SSN-transduced MPS VI feline myoblasts demonstrated correction of glycosaminoglycan storage and contained 55-fold and 3.5-fold elevated levels of 4S activity when compared with normal feline myoblasts respectively. Recombinant feline 4S (rf4S) secreted by Lf4S-transduced MPS VI myoblasts was shown to be endocytosed by MPS VI feline cells via the mannose-6-phosphate receptor system, leading to metabolic correction. The results from this study demonstrate that muscle-mediated gene replacement therapy may be a viable method for achieving circulating levels of recombinant f4S (rf4S) in the MPS VI cat.
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PMID:Feline mucopolysaccharidosis type VI: correction of glycosaminoglycan storage in myoblasts by retrovirus-mediated transfer of the feline N-acetylgalactosamine 4-sulfatase gene. 936 29

The abundance of amyloid beta peptide (A beta) and the selective loss of neurons are characteristics of Alzheimer's disease. However, subpopulations of brain cells survive, including neurons near A beta-rich plaques. The surviving neurons may have gene expression profiles that allow them to be resistant to A beta toxicity. Here we use the differential display technique to compare the profiles of gene expression in an A beta-resistant cell line with its parental cells. Prominent among the changes are two components of the endosomal-lysosomal system, insulin growth factor II receptor/mannose-6-phosphate receptor and arylsulfatase B. Both are more highly expressed in the A beta-resistant clone, and arylsulfatase is inducible by A beta and hydrogen peroxide. Another lysosomal enzyme, beta-glucuronidase, is also up-regulated in A beta-resistant cells. These results are consistent with the observation that the endosomal-lysosomal system is highly activated in Alzheimer's disease brains, and they raise the possibility that the high expression of endosomal-lysosomal components is important for neuronal survival in the presence of A beta.
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PMID:The up-regulation of endosomal-lysosomal components in amyloid beta-resistant cells. 1050 Nov 92

Mucopolysaccharidosis IVA (MPS IVA; Morquio A syndrome) is a lysosomal storage disorder caused by deficiency of N-acetylgalactosamine-6-sulfatase (GALNS), an enzyme that degrades keratan sulfate (KS). Currently no therapy for MPS IVA is available. We produced recombinant human (rh)GALNS as a potential enzyme replacement therapy for MPS IVA. Chinese hamster ovary cells stably overexpressing GALNS and sulfatase modifying factor-1 were used to produce active ( approximately 2 U/mg) and pure (>or=97%) rhGALNS. The recombinant enzyme was phosphorylated and was dose-dependently taken up by mannose-6-phosphate receptor (K(uptake) = 2.5 nM), thereby restoring enzyme activity in MPS IVA fibroblasts. In the absence of an animal model with a skeletal phenotype, we established chondrocytes isolated from two MPS IVA patients as a disease model in vitro. MPS IVA chondrocyte GALNS activity was not detectable and the cells exhibited KS storage up to 11-fold higher than unaffected chondrocytes. MPS IVA chondrocytes internalized rhGALNS into lysosomes, resulting in normalization of enzyme activity and decrease in KS storage. rhGALNS treatment also modulated gene expression, increasing expression of chondrogenic genes Collagen II, Collagen X, Aggrecan and Sox9 and decreasing abnormal expression of Collagen I. Intravenous administration of rhGALNS resulted in biodistribution throughout all layers of the heart valve and the entire thickness of the growth plate in wild-type mice. We show that enzyme replacement therapy with recombinant human GALNS results in clearance of keratan sulfate accumulation, and that such treatment ameliorates aberrant gene expression in human chondrocytes in vitro. Penetration of the therapeutic enzyme throughout poorly vascularized, but clinically relevant tissues, including growth plate cartilage and heart valve, as well as macrophages and hepatocytes in wild-type mouse, further supports development of rhGALNS as enzyme replacement therapy for MPS IVA.
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PMID:Enzyme replacement in a human model of mucopolysaccharidosis IVA in vitro and its biodistribution in the cartilage of wild type mice. 2080 38