Intracellular localization of beta-glucuronidase in fibroblasts after direct transfer from macrophages.
The subcellular distribution of beta-glucuronidase acquired by deficient human fibroblasts during co-culture with peritoneal macrophages was compared with that taken up by receptor-mediated endocytosis. Labelled enzyme taken up via receptors was located initially in a low-density endosomal fraction and was transferred to lysosomes within a few minutes. The beta-glucuronidase acquired during 24 h of co-culture was present almost entirely within lysosomes and had a distribution profile identical with that of endogenous beta-hexosaminidase. Monensin prevented transfer of radiolabelled enzyme from endosomes to lysosomes and had a similar effect on the distribution of enzyme acquired by direct transfer, causing beta-glucuronidase to accumulate within endosomes. When the temperature was lowered from 37 degrees C to 19 degrees C, the rate of transfer of enzyme from endosomes to lysosomes was decreased during both direct transfer and indirect receptor-mediated endocytosis. These results show that a lysosomal enzyme acquired by direct transfer during cell-to-cell contact follows a similar intracellular route and has a similar distribution to that of enzymes taken up via cell-surface receptors.
Dean
M F
MF
Kennedy Institute of Rheumatology, Hammersmith, London, U.K.
Martin
J C
JC
D002450:Cell Communication; D002478:Cells, Cultured; D011992:Endosomes / Q000201:enzymology; D005347:Fibroblasts / Q000201:enzymology*; D005966:Glucuronidase / Q000378:metabolism*; D006801:Humans; D008247:Lysosomes / Q000201:enzymology; D008264:Macrophages / Q000201:enzymology*; D008985:Monensin / Q000494:pharmacology; D013347:Subcellular Fractions / Q000201:enzymology; D013696:Temperature; D001619:beta-N-Acetylhexosaminidases / Q000378:metabolism
D008985:Monensin; D005966:Glucuronidase; D001619:beta-N-Acetylhexosaminidases