Mouse embryonic fibroblasts that are deficient in the two mannose 6-phosphate receptors (MPRs) MPR 46 and MPR 300 missort the majority (> or = 85%) of soluble lysosomal proteins into the medium. Human MPR 46 and MPR 300 were expressed in these cells to test whether overexpression of a single type of MPR can restore transport of lysosomal proteins to lysosomes. Only a partial correction of the missorting was observed after overexpression of MPR 46. Even at MPR 46 levels that are five times higher than the wild-type level, more than one third of the newly synthesized lysosomal proteins accumulates in the secretions. Two-fold overexpression of MPR 300 completely corrects the missorting of lysosomal enzymes. However, at least one fourth of the lysosomal enzymes are transported along a secretion-recapture pathway that is sensitive to mannose 6-phosphate in medium. In control fibroblasts that express both types of MPR, the secretion-recapture pathway is of minor importance. These results imply that neither overexpression of MPR 46 nor MPR 300 is sufficient for targeting of lysosomal proteins along intracellular routes.
Article|
August 01 1996
Neither type of mannose 6-phosphate receptor is sufficient for targeting of lysosomal enzymes along intracellular routes.
D Kasper,
D Kasper
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
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F Dittmer,
F Dittmer
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
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K von Figura,
K von Figura
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
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R Pohlmann
R Pohlmann
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
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D Kasper
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
F Dittmer
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
K von Figura
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
R Pohlmann
Georg-August-University, Abt. Biochemie II, Göttingen, Germany.
Online ISSN: 1540-8140
Print ISSN: 0021-9525
J Cell Biol (1996) 134 (3): 615–623.
Citation
D Kasper, F Dittmer, K von Figura, R Pohlmann; Neither type of mannose 6-phosphate receptor is sufficient for targeting of lysosomal enzymes along intracellular routes.. J Cell Biol 1 August 1996; 134 (3): 615–623. doi: https://doi.org/10.1083/jcb.134.3.615
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