1979
DOI: 10.1172/jci109341
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Excretion-Reuptake Route of β-Hexosaminidase in Normal and I-Cell Disease Cultured Fibroblasts

Abstract: A B S T R A C T It has been proposed that in cultured fibroblasts the final packaging of enzymes in lysosomes re(luires excretion followed by pinocytosis by neighboring cells via a carbohydrate-specific receptor mechanism. It has also been proposed that the abnormally high activity of lysosomal enzymiies in the medium of cultured fibroblasts from patients with I-cell disease (mucolipidosis II) results from an altered carbohydrate recognition residue on the enzymes which prevents reuptake into the cells. With 8… Show more

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Cited by 75 publications
(38 citation statements)
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“…The MPRI/IGF II receptor is an attractive candidate, as it may not only be involved in endocytosis for catalytic activity in a prelysosomal compartment, but also possibly trigger mechanisms normally activated by the binding of IGF II, resulting in cell proliferation (31,32). Involvement of the MPRc/IGF II receptor, however, seems unlikely in our case because M6P at a concentration that effectively prevents lysosomal enzyme binding (20) did not significantly inhibit Hex A effect (Fig. 5).…”
Section: Discussionmentioning
confidence: 74%
“…The MPRI/IGF II receptor is an attractive candidate, as it may not only be involved in endocytosis for catalytic activity in a prelysosomal compartment, but also possibly trigger mechanisms normally activated by the binding of IGF II, resulting in cell proliferation (31,32). Involvement of the MPRc/IGF II receptor, however, seems unlikely in our case because M6P at a concentration that effectively prevents lysosomal enzyme binding (20) did not significantly inhibit Hex A effect (Fig. 5).…”
Section: Discussionmentioning
confidence: 74%
“…Chloroquine an(l NH4Cl, which inhibit enzyme uptake noncompetitively (28), likewise cause increased extracellular accumulation of enzyme and decrease(l incorporation into lysosomes, although by a mechanism different from the I-cell mutation (10). On the other hand, at a concentration that comnpletely inhibits uptake of exogenous enzyme, mannose 6-phosphate does not decrease the intracellular level of endogenous enzymes and increases only slightly the extracellular level (10,(29)(30)(31) …”
Section: Discussionmentioning
confidence: 99%
“…22); the dialyzed compounds were incubated for 30 min at 4°C in a 6:1 (TTC/Hex A) molar ratio to obtain mixed disulfides, followed by further dialysis in saline. Recovery was -50% by enzyme activity against 4-methylumbelliferyl N-acetylglucosaminide (4MUG) (23) (1 unit = 1 nmol of 4MUG cleaved per hr at 37°C), 4MUG 6-sulfate (24), and GM2 ganglioside [GalNAcI31--4(NeuAca2--*3)Galp1-4Glc---Cer] (GM2) (25) (27) were detectable in 42% and 71% of the cells by 3 and 4 DIV, respectively, consistent with neuronal identity. These cultures were used at 2-3 DIV, when the number of processbearing neurons was highest.…”
Section: Methodsmentioning
confidence: 99%