Cystine depletion by WR-1065 in cystinotic cells. Mechanism of action.
Cystinotic leucocytes and skin fibroblasts incubated with the aminothiol N-(2'-mercaptoethyl)-1,3-propanediamine (WR-1065) exhibited substantial intralysosomal cystine depletion within 2 hr. Wr-2721, the thiol phosphorylated derivative of WR-1065, did not lower cystinotic leucocyte cystine in 1 hr but depleted cystinotic fibroblasts of cystine after 21 hr. Concentrations of cysteamine (beta-mercaptoethylamine) equimolar with those of WR-1065 depleted cystine more rapidly than did WR-1065, but the extent of cystine depletion by WR-1065 approached that for cysteamine when longer periods of incubation or higher concentrations were used. Cystine depletion by WR-1065 was slower for leucocyte lysosomal granular fractions than for whole leucocytes. L-[35S]Cystine-labeled fibroblasts exposed to WR-1065 exhibited new compounds not seen when cells were incubated without WR-1065: WR-1065-cysteine, cysteamine-cysteine and cysteamine-glutathione mixed disulfides. L-[35S]Cystine-loaded lysosome-rich granular fractions from cystinotic leucocytes incubated with WR-1065 formed WR-1065-cysteine mixed disulfide but no cysteamine-cysteine mixed disulfide. We suggest that WR-2721 is dephosphorylated intracellularly to the free thiol, WR-1065, which subsequently is converted to cysteamine by an unknown route. Intracellular cysteamine then enters the lysosome and reacts with free cystine to form cysteamine-cysteine mixed disulfide and cysteine which move into the cytosol and the incubation medium where they participate in further interchange reactions with free thiols present there, namely WR-1065 and glutathione.
Butler
J D
JD
Gahl
W A
WA
Tietze
F
F
D004999:Amifostine / Q000494:pharmacology; D002648:Child; D002675:Child, Preschool; D003543:Cysteamine / Q000494:pharmacology; D003553:Cystine / Q000378:metabolism*; D003554:Cystinosis / Q000188:drug therapy / Q000378:metabolism*; D006801:Humans; D066298:In Vitro Techniques; D008624:Mercaptoethylamines / Q000494:pharmacology*; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D013462:Sulfur Radioisotopes
D008624:Mercaptoethylamines; D011837:Radiation-Protective Agents; D013462:Sulfur Radioisotopes; C020174:N-(2-mercaptoethyl)-1,3-diaminopropane; D003553:Cystine; D003543:Cysteamine; D004999:Amifostine