title: Lipid raft-mediated uptake of cysteine-modified thioredoxin-1: apoptosis enhancement by inhibiting the endogenous thioredoxin-1.
abstract: Thioredoxin-1 (TRX) plays important roles in cellular signaling by controlling the redox state of cysteine residues in target proteins. TRX is released in response to oxidative stress and shows various biologic functions from the extracellular environment. However, the mechanism by which extracellular TRX transduces the signal into the cells remains unclear. Here we report that the cysteine modification at the active site of TRX promotes the internalization of TRX into the cells. TRX-C35S, in which the cysteine at residue 35 of the active site was replaced with serine, was internalized more effectively than wild-type TRX in human T-cell leukemia virus-transformed T cells. TRX-C35S bound rapidly to the cell surface and was internalized into the cells dependent on lipid rafts in the plasma membrane. This process was inhibited by wild-type TRX, reducing reagents such as dithiothreitol, and methyl-beta-cyclodextrin, which disrupts lipid rafts. Moreover, the internalized TRX-C35S binds to endogenous TRX, resulting in the generation of intracellular reactive oxygen species (ROS) and enhanced cis-diamine-dichloroplatinum (II) (CDDP)-induced apoptosis via a ROS-mediated pathway involving apoptosis signal-regulating kinase-1 (ASK-1) activation. These findings suggest that the cysteine at the active site of TRX plays a key role in the internalization and signal transduction of extracellular TRX into the cells.
authors.affiliation: Department of Biological Responses, Institute for Virus Research, Kyoto University, and Thioredoxin Project, Translational Research Center Kyoto University Hospital, Kyoto, Japan. nkondoh-ivr@umin.ac.jp
authors.forename: Norihiko
authors.initials: N
authors.lastname: Kondo
authors.forename: Yasuyuki
authors.initials: Y
authors.lastname: Ishii
authors.forename: Yong-Won
authors.initials: YW
authors.lastname: Kwon
authors.forename: Masaki
authors.initials: M
authors.lastname: Tanito
authors.forename: Junko
authors.initials: J
authors.lastname: Sakakura-Nishiyama
authors.forename: Michika
authors.initials: M
authors.lastname: Mochizuki
authors.forename: Michiyuki
authors.initials: M
authors.lastname: Maeda
authors.forename: Shigo
authors.initials: S
authors.lastname: Suzuki
authors.forename: Masami
authors.initials: M
authors.lastname: Kojima
authors.forename: Yong-Chul
authors.initials: YC
authors.lastname: Kim
authors.forename: Aoi
authors.initials: A
authors.lastname: Son
authors.forename: Hajime
authors.initials: H
authors.lastname: Nakamura
authors.forename: Junji
authors.initials: J
authors.lastname: Yodoi
mesh_terms: D019943:Amino Acid Substitution; D017209:Apoptosis; D003545:Cysteine; D006801:Humans; D019169:Jurkat Cells; D021962:Membrane Microdomains / Q000502:physiology*; D008954:Models, Biological; D011994:Recombinant Proteins / Q000378:metabolism; D013879:Thioredoxins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D011994:Recombinant Proteins; D013879:Thioredoxins; D003545:Cysteine