title: Regulation of perforin lysis: implications for protein disulfide isomerase proteins.
abstract: Perforin, a membrane-permeabilizing protein, is important to T cell cytotoxic action. Perforin has potential to damage the T cell in the endoplasmic reticulum (ER), is sequestered in granules, and later is exocytosed to kill cells. In the ER and after exocytosis, calcium and pH favor perforin activity. We found a novel perforin inhibitor associated with cytotoxic T cell granules and termed it Cytotoxic Regulatory Protein 2 (CxRP2). CxRP2 blocked lysis by granule extracts, recombinant perforin and T cells. Its effects lasted for hours. CxRP2 was calcium stable and refractory to inhibitors of granzyme and cathepsin proteases. Through mass spectrometric analysis of active 50-100 kDa proteins, we identified CxRP2 candidates. Protein disulfide isomerase A3 was the strongest candidate but was unavailable for testing; however, protein disulfide isomerase A1 had CxRP2 activity. Our results indicate that protein disulfide isomerases, in the ER or elsewhere, may protect T cells from their own perforin.
authors.affiliation: Department of Microbiology and Immunology MS320, University of Nevada, School of Medicine, Reno, NV 89557, USA. david@tamang.org
authors.forename: David L
authors.initials: DL
authors.lastname: Tamang
authors.forename: Bryce N
authors.initials: BN
authors.lastname: Alves
authors.forename: Viki
authors.initials: V
authors.lastname: Elliott
authors.forename: Doug
authors.initials: D
authors.lastname: Redelman
authors.forename: Renu
authors.initials: R
authors.lastname: Wadhwa
authors.forename: Stephanie A
authors.initials: SA
authors.lastname: Fraser
authors.forename: Dorothy
authors.initials: D
authors.lastname: Hudig
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D003594:Cytoplasmic Granules / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins / Q000378:metabolism; D006360:Heat-Shock Proteins / Q000378:metabolism; D007527:Isoenzymes / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018832:Molecular Chaperones / Q000378:metabolism; D054353:Perforin / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D011480:Protease Inhibitors / Q000378:metabolism; D019704:Protein Disulfide-Isomerases / Q000378:metabolism*; D051381:Rats; D013347:Subcellular Fractions / Q000378:metabolism; D013602:T-Lymphocytes, Cytotoxic / Q000166:cytology / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D000091342:Endoplasmic Reticulum Chaperone BiP; D018840:HSP70 Heat-Shock Proteins; D006360:Heat-Shock Proteins; D007527:Isoenzymes; D018832:Molecular Chaperones; D011480:Protease Inhibitors; C080352:mortalin; D054353:Perforin; D019704:Protein Disulfide-Isomerases