title: Effect of cigarette smoke exposure and structural modifications on the α-1 Antitrypsin interaction with caspases.
abstract: α-1 Antitrypsin (A1AT) is a serpin with a major protective effect against cigarette smoke-induced emphysema development, and patients with mutations of the A1AT gene display a markedly increased risk for developing emphysema. We reported that A1AT protects lung endothelial cells from apoptosis and inhibits caspase-3 activity. It is not clear if cigarette smoking or A1AT mutations alter the caspase-3 inhibitory activity of A1AT and if this serpin alters the function of other caspases. We tested the hypothesis that the caspase-3 inhibitory activity of A1AT is impaired by cigarette smoking and that the A1AT RCL, the key antiprotease domain of the serpin, is required for its interaction with the caspase. We examined the caspase-3 inhibitory activity of human A1AT purified from plasma of actively smoking and nonsmoking individuals, either affected or unaffected with chronic obstructive pulmonary disease. We also tested the caspase inhibitory activity of two mutant forms of A1AT, the recombinant human piZZ and the RCL-deleted (RCL-null) A1AT forms. A1AT purified from the blood of active smokers exhibited marked attenuation in its caspase-3 inhibitory activity, independent of disease status. In vitro exposure of the normal (MM) form of A1AT to cigarette smoke extract reduced its ability to interact with caspase-3, measured by isothermal titration calorimetry, as did the deletion of the RCL, but not the ZZ point mutation. In cell-free assays A1AT was capable of inhibiting all executioner caspases, -3, -7 and especially -6, but not the initiator or inflammatory caspases. The inhibitory effect of A1AT against caspase-6 was tested in vivo, where overexpression of both human MM and ZZ-A1AT via adeno-associated virus transduction significantly protected against apoptosis and against airspace damage induced by intratracheal instillation of caspase-6 in mice. These data indicate a specific inhibitory effect of A1AT on executioner caspases, which is profoundly attenuated by active exposure to cigarette smoking and is dependent on the protein RCL, but is not affected by the PiZZ mutation.
authors.affiliation: Department of Medicine, Indiana University, Indianapolis, Indiana 46202, USA.
authors.forename: Angelia D
authors.initials: AD
authors.lastname: Lockett
authors.forename: Mary
authors.initials: M
authors.lastname: Van Demark
authors.forename: Yuan
authors.initials: Y
authors.lastname: Gu
authors.forename: Kelly S
authors.initials: KS
authors.lastname: Schweitzer
authors.forename: Ninotchka
authors.initials: N
authors.lastname: Sigua
authors.forename: Krzysztof
authors.initials: K
authors.lastname: Kamocki
authors.forename: Iwona
authors.initials: I
authors.lastname: Fijalkowska
authors.forename: Jana
authors.initials: J
authors.lastname: Garrison
authors.forename: Amanda J
authors.initials: AJ
authors.lastname: Fisher
authors.forename: Karina
authors.initials: K
authors.lastname: Serban
authors.forename: Robert A
authors.initials: RA
authors.lastname: Wise
authors.forename: Terence R
authors.initials: TR
authors.lastname: Flotte
authors.forename: Christian
authors.initials: C
authors.lastname: Mueller
authors.forename: Robert G
authors.initials: RG
authors.lastname: Presson
authors.forename: Horia I
authors.initials: HI
authors.lastname: Petrache
authors.forename: Rubin M
authors.initials: RM
authors.lastname: Tuder
authors.forename: Irina
authors.initials: I
authors.lastname: Petrache
mesh_terms: D000328:Adult; D000368:Aged; D000818:Animals; D053148:Caspase 3 / Q000378:metabolism*; D053178:Caspase 6 / Q000494:pharmacology; D053179:Caspase 7 / Q000378:metabolism; D005260:Female; D006801:Humans; D051379:Mice; D008810:Mice, Inbred C57BL; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000378:metabolism*; D012907:Smoking / Q000378:metabolism*; D019896:alpha 1-Antitrypsin Deficiency / Q000378:metabolism*
chemical_list: D053148:Caspase 3; D053178:Caspase 6; D053179:Caspase 7