Targeted disruption of the gene encoding the murine small subunit of carboxypeptidase N (CPN1) causes susceptibility to C5a anaphylatoxin-mediated shock.
Carboxypeptidase N (CPN) is a plasma zinc metalloprotease, which consists of two enzymatically active small subunits (CPN1) and two large subunits (CPN2) that protect the protein from degradation. Historically, CPN has been implicated as a major regulator of inflammation by its enzymatic cleavage of functionally important arginine and lysine amino acids from potent phlogistic molecules, such as the complement anaphylatoxins C3a and C5a. Because of no known complete CPN deficiencies, the biological impact of CPN in vivo has been difficult to evaluate. Here, we report the generation of a mouse with complete CPN deficiency by targeted disruption of the CPN1 gene. CPN1(-/-) mice were hypersensitive to lethal anaphylactic shock due to acute complement activation by cobra venom factor. This hypersensitivity was completely resolved in CPN1(-/-)/C5aR(-/-) but not in CPN1(-/-)/C3aR(-/-) mice. Moreover, CPN1(-/-) mice given C5a i.v., but not C3a, experienced 100% mortality. This C5a-induced mortality was reduced to 20% when CPN1(-/-) mice were treated with an antihistamine before C5a challenge. These studies describe for the first time a complete deficiency of CPN and demonstrate 1) that CPN plays a requisite role in regulating the lethal effects of anaphylatoxin-mediated shock, 2) that these lethal effects are mediated predominantly by C5a-induced histamine release, and 3) that C3a does not contribute significantly to shock following acute complement activation.
Research Center for Immunology and Autoimmune Diseases, Brown Foundation Institute of Molecular Medicine for the Prevention of Human Diseases, University of Texas Health Science Center at Houston, Houston, TX 77030, USA.
Stacey L
SL
Mueller-Ortiz
Dachun
D
Wang
John E
JE
Morales
Li
L
Li
Jui-Yoa
JY
Chang
Rick A
RA
Wetsel
D000818:Animals; D015139:Blotting, Southern; D015926:Complement C3a / Q000276:immunology / Q000378:metabolism; D015936:Complement C5a / Q000276:immunology / Q000378:metabolism*; D051056:Complement Inactivating Agents / Q000633:toxicity; D004198:Disease Susceptibility / Q000276:immunology; D004546:Elapid Venoms / Q000633:toxicity; D005260:Female; D006632:Histamine / Q000276:immunology / Q000378:metabolism; D006801:Humans; D001121:Lysine Carboxypeptidase / Q000235:genetics* / Q000276:immunology; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012769:Shock / Q000235:genetics* / Q000276:immunology
D051056:Complement Inactivating Agents; D004546:Elapid Venoms; C016310:cobra venom factor; D015926:Complement C3a; D015936:Complement C5a; D006632:Histamine; D001121:Lysine Carboxypeptidase