title: A novel apoptotic pathway in quiescent lymphocytes identified by inhibition of a post-proline cleaving aminodipeptidase: a candidate target protease, quiescent cell proline dipeptidase.
abstract: The vast majority of lymphocytes in vivo persist in a quiescent state. These resting lymphocytes are maintained through a cellular program that suppresses apoptosis. We show here that quiescent PBMC, but not activated PBMC or transformed lymphocytes, die in the presence of highly specific post-proline aminodipeptidase inhibitors. This form of death has the hallmarks of apoptosis, such as phosphatidylserine externalization and loss of mitochondrial transmembrane potential. However, it differs from apoptosis induced by gamma irradiation in the same cells or by Fas ligation in transformed lymphocytes in terms of caspase involvement. In addition, the aminodipeptidase inhibitor-induced cell death, but not gamma-irradiation-mediated apoptosis, can be prevented by inhibition of the proteasome complex. The target of these inhibitors is not CD26/DPPIV, but probably a novel serine protease, quiescent cell proline dipeptidase, that we have recently isolated and cloned. These studies will yield a better understanding of the requirements and the mechanisms that mediate quiescent lymphocyte homeostasis in vivo.
authors.affiliation: Department of Pathology, Program in Immunology, Tufts University School of Medicine, Boston, MA 02111, USA.
authors.forename: M
authors.initials: M
authors.lastname: Chiravuri
authors.forename: T
authors.initials: T
authors.lastname: Schmitz
authors.forename: K
authors.initials: K
authors.lastname: Yardley
authors.forename: R
authors.initials: R
authors.lastname: Underwood
authors.forename: Y
authors.initials: Y
authors.lastname: Dayal
authors.forename: B T
authors.initials: BT
authors.lastname: Huber
mesh_terms: D017209:Apoptosis / Q000187:drug effects / Q000276:immunology*; D001897:Boronic Acids / Q000378:metabolism; D020169:Caspases / Q000378:metabolism; D016923:Cell Death / Q000187:drug effects / Q000276:immunology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004150:Dipeptidases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D018819:Dipeptidyl Peptidase 4 / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000378:metabolism / Q000494:pharmacology; D006801:Humans; D006868:Hydrolysis; D007399:Interphase / Q000187:drug effects / Q000276:immunology; D008214:Lymphocytes / Q000187:drug effects / Q000201:enzymology* / Q000648:ultrastructure; D008854:Microscopy, Electron; D009097:Multienzyme Complexes / Q000378:metabolism; D011392:Proline / Q000031:analogs & derivatives / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex; D011499:Protein Processing, Post-Translational / Q000187:drug effects / Q000276:immunology*; D016192:Resting Phase, Cell Cycle / Q000276:immunology; D013379:Substrate Specificity / Q000276:immunology
chemical_list: D001897:Boronic Acids; D004791:Enzyme Inhibitors; D009097:Multienzyme Complexes; D011392:Proline; D004150:Dipeptidases; C022449:proline dipeptidase; D018819:Dipeptidyl Peptidase 4; D020169:Caspases; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex