Intracellular localization of β-glucuronidase in fibroblasts after direct transfer from macrophages

Abstract

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.

Uptake of Oxidized LDL by Macrophages Differs From That of Acetyl LDL and Leads to Expansion of an Acidic Endolysosomal Compartment

“…Macrophages were disrupted and fractionated essentially as described by Dean and Martin. 24 Cells were gently removed from the plates by using cell lifters and sedimented at 1100g for 10 minutes at 4°C. Between 10 6 and 2ϫ10 6 cells were resuspended in 2 mL of cold 10 mmol/L Tris, 0.25 mol/L sucrose, and 1 mmol/L EDTA (pH 7.5) and disrupted by N 2 cavitation at 445 kPa (mouse peritoneal macrophages) or 310 kPa (J774 cells) for 15 minutes in a precooled Kontes mini celldisruption chamber (Mandel Scientific).…”

β-Glucuronidase and hexosaminidase are marker enzymes for different compartments of the endo-lysosomal system in mussel digestive cells

“…The transfer of β-Gus from cell to cell has been reported in various vertebrate cell models in which it may be achieved by two alternative mechanisms: (1) secretion of inactive proenzyme from a cell, followed by endocytosis into another cell and post-endocytic maturation of the enzyme to its active form; and (2) direct enzyme transfer through the cell membranes of two adjacent cells (Dean and Martin 1988;Bou-Gharios et al 1991, 1993. The present results indicate that, in the mussel digestive gland, β-Gus might well be released to the alveolar lumen in secretory granules produced by basophilic cells and endocytosed by digestive cells.…”

“…fibroblasts) after ciMPR-mediated endocytosis of the enzyme synthesised in a source cell (i.e. macrophages and lymphocytes; Dean and Martin 1988;Bou-Gharios et al 1991, 1993.…”

Intercellular transport of lysosomal acid lipase mediates lipoprotein cholesteryl ester metabolism in a human vascular endothelial cell-fibroblast coculture system.

“…Macrophages can acquire acid hydrolases through a receptor-mediated process that involves recognition of mannosyl-, N-acetylglucosaminyl-, and L-fucosyl residues of glycoproteins (Shepherd and Stahl, 1984); the expression of this receptor is regulated by glucocorticoid hormones. Acid hydrolases may also be transported from macrophages (McNamara et al, 1985;Dean and Martin, 1988) and lymphocytes (Olsen et al, 1981;Abraham et al, 1985) by direct contact between donor and recipient cells. The prevalence of leukocytes in atherosclerotic lesions points up the need to consider all of these possible mechanisms for intercellular hydrolase exchange among cells of the vascular wall.…”