text: Pretreatment with lysosomal enzyme inhibitors [(2S, 3S)trans-epoxysuccinyl-L-leucylamido-3-methylbutane ethyl ester or chloroquine] or proteasome inhibitors (<< proteasome >> inhibitor I, [[ MG-132 ]], or lactacystin) decreased the extent of U50,488H-induced down-regulation.