Characterization of lysosomal enzymes from cultured cynomolgus monkey trabecular meshwork cells

The current study characterizes selected properties of lysosomal enzymes associated with cynomolgus monkey trabecular meshwork (MTM) cells. These proteins may participate in the turnover of macromolecules involved in regulating the aqueous outflow. Intracellular levels of lysosomal enzymes in MTM cells were similar to those found in cultured human fibroblasts. The presence of ammonium chloride increased the secretion rate of certain lysosomal enzymes from 47 to 122% of normal. Column chromatography of the secreted enzymes on the galactose-specific lectin Ricinus communis I demonstrated an increase in the number of accessible galactose residues on lysosomal enzymes secreted in the presence of ammonium chloride. The presence of mannose-6-phosphate receptors on the trabecular meshwork cells was demonstrated by the specific uptake of purified 125I-beta-D-glucosidase. This uptake represented 20% of that observed with cultured human fibroblasts and was inhibited only 50% by the presence of mannose-6-phosphate.