Accumulation of catalytically active proteases in lacrimal gland acinar cell endosomes during chronic ex vivo muscarinic receptor stimulation.

摘要: Chronic muscarinic stimulation induces functional quiescence (Scand J Immunol 2003;58:550–65) and alters the traffic of immature cathepsin B (Exp Eye Res 2004;79:665–75) in lacrimal acinar cells. To test whether active proteases aberrantly accumulate endosomes, cell samples were cultured 20 h with without 10-µm carbachol (CCh), incubated [125I]-bovine serum albumin then lysed analysed by subcellular fractionation. CCh decreased total cysteine protease S activities isolated lysosome, redistributing them to early endocytic biosynthetic compartments. [125I] accumulation all compartments cells loaded absence inhibitors; inhibitor, leupeptin, prevented endosomal decrease but not lysosomal decrease. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis autoradiography demonstrated [125I]-labelled proteolytic products endomembrane both control CCh-stimulated cells, even presence analysis indicated that increased amount endosomes. Two-dimensional fractionation analyses suggest CCh-induced redistributions result from blocks late endosome trans-Golgi network. Therefore, we conjecture chronic acetylcholine receptor leads aberrant processing autoantigens whence previously cryptic epitopes may be secreted underlying interstitial space.