{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,9,19]],"date-time":"2025-09-19T10:54:10Z","timestamp":1758279250156},"reference-count":0,"publisher":"Rockefeller University Press","issue":"4","content-domain":{"domain":["rupress.org"],"crossmark-restriction":true},"short-container-title":[],"published-print":{"date-parts":[[1989,10,1]]},"abstract":"<jats:p>A mutant strain of Dictyostelium discoideum, HMW570, oversecretes several lysosomal enzyme activities during growth. Using a radiolabel pulse-chase protocol, we followed the synthesis and secretion of two of these enzymes, alpha-mannosidase and beta-glucosidase. A few hours into the chase period, HMW570 had secreted 95% of its radiolabeled alpha-mannosidase and 86% of its radiolabeled beta-glucosidase as precursor polypeptides compared to the secretion of less than 10% of these forms from wild-type cells. Neither alpha-mannosidase nor beta-glucosidase in HMW570 were ever found in the lysosomal fractions of sucrose gradients consistent with HMW570 being defective in lysosomal enzyme targeting. Also, both alpha-mannosidase and beta-glucosidase precursors in the mutant strain were membrane associated as previously observed for wild-type precursors, indicating membrane association is not sufficient for lysosomal enzyme targeting. Hypersecretion of the alpha-mannosidase precursor by HMW570 was not accompanied by major alterations in N-linked oligosaccharides such as size, charge, and ratio of sulfate and phosphate esters. However, HMW570 was defective in endocytosis. A fluid phase marker, [3H]dextran, accumulated in the mutant at one-half of the rate of wild-type cells and to only one-half the normal concentration. Fractionation of cellular organelles on self-forming Percoll gradients revealed that the majority of the fluid-phase marker resided in compartments in mutant cells with a density characteristic of endosomes. In contrast, in wild-type cells [3H]dextran was predominantly located in vesicles with a density identical to secondary lysosomes. Furthermore, the residual lysosomal enzyme activity in the mutant accumulated in endosomal-like vesicles. Thus, the mutation in HMW570 may be in a gene required for both the generation of dense secondary lysosomes and the sorting of lysosomal hydrolases.<\/jats:p>","DOI":"10.1083\/jcb.109.4.1445","type":"journal-article","created":{"date-parts":[[2004,5,15]],"date-time":"2004-05-15T00:18:20Z","timestamp":1084580300000},"page":"1445-1456","update-policy":"http:\/\/dx.doi.org\/10.1083\/jcb.crossmarkpolicy","source":"Crossref","is-referenced-by-count":19,"title":["A Dictyostelium discoideum mutant that missorts and oversecretes lysosomal enzyme precursors is defective in endocytosis."],"prefix":"10.1083","volume":"109","author":[{"given":"D L","family":"Ebert","sequence":"first","affiliation":[{"name":"Department of Bacteriology, University of Wisconsin, Madison 53706."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"H H","family":"Freeze","sequence":"additional","affiliation":[{"name":"Department of Bacteriology, University of Wisconsin, Madison 53706."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"J","family":"Richardson","sequence":"additional","affiliation":[{"name":"Department of Bacteriology, University of Wisconsin, Madison 53706."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"R L","family":"Dimond","sequence":"additional","affiliation":[{"name":"Department of Bacteriology, University of Wisconsin, Madison 53706."}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"J A","family":"Cardelli","sequence":"additional","affiliation":[{"name":"Department of Bacteriology, University of Wisconsin, Madison 53706."}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"291","published-online":{"date-parts":[[1989,10,1]]},"container-title":["The Journal of cell biology"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/rupress.org\/jcb\/article-pdf\/109\/4\/1445\/1462319\/1445.pdf","content-type":"application\/pdf","content-version":"vor","intended-application":"syndication"},{"URL":"https:\/\/rupress.org\/jcb\/article-pdf\/109\/4\/1445\/1462319\/1445.pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2023,7,22]],"date-time":"2023-07-22T00:49:20Z","timestamp":1689986960000},"score":1,"resource":{"primary":{"URL":"https:\/\/rupress.org\/jcb\/article\/109\/4\/1445\/28724\/A-Dictyostelium-discoideum-mutant-that-missorts"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[1989,10,1]]},"references-count":0,"journal-issue":{"issue":"4","published-print":{"date-parts":[[1989,10,1]]}},"URL":"https:\/\/doi.org\/10.1083\/jcb.109.4.1445","relation":{},"ISSN":["0021-9525","1540-8140"],"issn-type":[{"value":"0021-9525","type":"print"},{"value":"1540-8140","type":"electronic"}],"subject":[],"published":{"date-parts":[[1989,10,1]]}}}