title: Lysosomal chymotrypsin B potentiates apoptosis via cleavage of Bid.
abstract: We have reported that chymotrypsin B (CtrB) is not just a digestive enzyme but is also stored in lysosomes. Herein, we demonstrated a broad distribution of CtrB and explored the involvement of CtrB in apoptosis. Exposure of RH-35 cells to H(2)O(2) or palmitate induced the redistribution of lysosomal CtrB into the cytoplasm as a result of lysosomal membrane permeabilization (LMP). Suppression of CtrB significantly blocked apoptosis, while overexpression of CtrB sensitized apoptosis markedly. CtrB could cleave Bid under neutral conditions. In RH-35 cells with Bid silenced, apoptosis induced by CtrB protein was attenuated, suggesting that CtrB mediates apoptosis of RH-35 cells mainly through processing Bid. Our data also suggest that LMP occurs earlier than mitochondrial outer membrane permeabilization; Bid activation initiated by caspase-8 might be reinforced by CtrB in consequence of LMP, which causes a positive feedback loop leading to the accumulation of tBid, and results in lysosome- and mitochondrion-dependent apoptosis.
authors.affiliation: National Laboratory of Biomacromolecules, Institute of Biophysics, Chinese Academy of Sciences, 15 Datun Road, Chaoyang District, Beijing, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Zhao
authors.forename: Xingyu
authors.initials: X
authors.lastname: Zhao
authors.forename: Yaping
authors.initials: Y
authors.lastname: Tu
authors.forename: Qi
authors.initials: Q
authors.lastname: Miao
authors.forename: Dongxu
authors.initials: D
authors.lastname: Cao
authors.forename: Wenjuan
authors.initials: W
authors.lastname: Duan
authors.forename: Yang
authors.initials: Y
authors.lastname: Sun
authors.forename: Jincheng
authors.initials: J
authors.lastname: Wang
authors.forename: Taotao
authors.initials: T
authors.lastname: Wei
authors.forename: Fuyu
authors.initials: F
authors.lastname: Yang
mesh_terms: D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid / Q000031:analogs & derivatives; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D053181:Caspase 8 / Q000378:metabolism; D002918:Chymotrypsin / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006861:Hydrogen Peroxide / Q000378:metabolism / Q000494:pharmacology; D007425:Intracellular Membranes / Q000378:metabolism; D008247:Lysosomes / Q000201:enzymology / Q000378:metabolism*; D008928:Mitochondria / Q000378:metabolism / Q000502:physiology; D051336:Mitochondrial Membranes / Q000378:metabolism; D011506:Proteins / Q000378:metabolism / Q000494:pharmacology / Q000502:physiology*
chemical_list: D011506:Proteins; D012856:4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfonic Acid; C032526:4-benzamido-4'-isothiocyanostilbene-2,2'-disulfonate; D006861:Hydrogen Peroxide; D002918:Chymotrypsin; C117609:chymotrypsin B; D053181:Caspase 8