title: Bacterial Heat Shock Protein GroEL (Hsp64) Exerts Immunoregulatory Effects on T Cells by Utilizing Apoptosis.
abstract: Aggregatibacter actinomycetemcomitans (Aa) expresses a 64-kDa GroEL protein belonging to the heat shock family of proteins. This protein has been shown to influence human host cells, but the apoptotic capacity of the GroEL protein regarding T cells is not yet known. The purpose of this study was to investigate the ability of A. actinomycetemcomitans GroEL (AaGroEL) protein to induce human peripheral blood T-cell apoptosis. Endogenous, purified AaGroEL protein was used as an antigen. In AaGroEL-treated T cells, the data indicated that phosphatidylserine exposure, an early apoptotic event, was dose- and time-dependent. The AaGroEL-treated T cells were also positive for active caspase-3 in a dose-dependent manner. The rate of AaGroEL-induced apoptosis was suppressed by the addition of the general caspase inhibitor Z-VAD-FMK. Furthermore, cleaved caspase-8 bands (40/36 kDa and 23 kDa) were identified in cells responding to AaGroEL. DNA fragmentation was also detected in the AaGroEL-treated T cells. Overall, we demonstrated that the endogenous GroEL from A. actinomycetemcomitans has the capacity to induce T-cell apoptosis.
authors.affiliation: Department of Molecular Biology and Genetics, Izmir Institute of Technology, Izmir, Turkey.
authors.forename: Ayten
authors.initials: A
authors.lastname: Nalbant
authors.affiliation: Department of Molecular Biology and Genetics, Izmir Institute of Technology, Izmir, Turkey.|Department of Medical Biochemistry, Dokuz Eylul University, Izmir, Turkey.
authors.forename: Melis
authors.initials: M
authors.lastname: Kant
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000378:metabolism*; D000590:Amino Acid Chloromethyl Ketones / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects*; D001426:Bacterial Proteins / Q000302:isolation & purification / Q000378:metabolism / Q000633:toxicity*; D053148:Caspase 3 / Q000378:metabolism; D053181:Caspase 8 / Q000378:metabolism; D061945:Caspase Inhibitors / Q000494:pharmacology; D002462:Cell Membrane / Q000187:drug effects / Q000378:metabolism; D002478:Cells, Cultured; D018834:Chaperonin 60 / Q000302:isolation & purification / Q000378:metabolism / Q000633:toxicity*; D053938:DNA Fragmentation / Q000187:drug effects; D006801:Humans; D008856:Microscopy, Fluorescence; D013601:T-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism
chemical_list: D000590:Amino Acid Chloromethyl Ketones; D001426:Bacterial Proteins; D061945:Caspase Inhibitors; D018834:Chaperonin 60; C096713:benzyloxycarbonylvalyl-alanyl-aspartyl fluoromethyl ketone; D053148:Caspase 3; D053181:Caspase 8