title: Mechanisms of Siglec-F-induced eosinophil apoptosis: a role for caspases but not for SHP-1, Src kinases, NADPH oxidase or reactive oxygen.
abstract: BACKGROUND
  Siglec-F and Siglec-8 are functional paralog proapoptotic cell surface receptors expressed on mouse and human eosinophils, respectively. Whereas Siglec-8 mediated death involves caspases and/or reactive oxygen species (ROS) generation and mitochondrial injury, very little is known about Siglec-F-mediated signaling and apoptosis. Therefore the objective of the current experiments was to better define apoptosis pathways mediated by Siglec-F and Siglec-8. Given that Siglec-F-induced apoptosis is much less robust than Siglec-8-induced apoptosis, we hypothesized that mechanisms involved in cell death via these receptors would differ.
  
  
  METHODS
  Consequences of engagement of Siglec-F on mouse eosinophils were studied by measuring ROS production, and by performing apoptosis assays using eosinophils from normal, hypereosinophilic, NADPH oxidase-deficient, src homology domain-containing protein tyrosine phosphatase (SHP)-1-deficient, and Lyn kinase-deficient mice. Inhibitors of caspase and Src family kinase activity were also used.
  
  
  RESULTS
  Engagement of Siglec-F induced mouse eosinophil apoptosis that was modest in magnitude and dependent on caspase activity. There was no detectable ROS generation, or any role for ROS, NADPH oxidase, SHP-1, or Src family kinases in this apoptotic process.
  
  
  CONCLUSIONS
  These data suggest that Siglec-F-mediated apoptosis is different in both magnitude and mechanisms when compared to published data on Siglec-8-mediated human eosinophil apoptosis. One likely implication of this work is that models targeting Siglec-F in vivo in mice may not provide identical mechanistic predictions for consequences of Siglec-8 targeting in vivo in humans.
authors.affiliation: Division of Allergy and Clinical Immunology, Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Maryland, United States of America.
authors.forename: Hui
authors.initials: H
authors.lastname: Mao
authors.forename: Gen
authors.initials: G
authors.lastname: Kano
authors.forename: Sherry A
authors.initials: SA
authors.lastname: Hudson
authors.forename: Mary
authors.initials: M
authors.lastname: Brummet
authors.forename: Nives
authors.initials: N
authors.lastname: Zimmermann
authors.forename: Zhou
authors.initials: Z
authors.lastname: Zhu
authors.forename: Bruce S
authors.initials: BS
authors.lastname: Bochner
mesh_terms: D000818:Animals; D015214:Antigens, Differentiation, Myelomonocytic / Q000378:metabolism*; D017209:Apoptosis / Q000502:physiology*; D020169:Caspases / Q000378:metabolism*; D004804:Eosinophils / Q000378:metabolism* / Q000502:physiology*; D037102:Lectins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D019255:NADPH Oxidases / Q000378:metabolism; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; D019061:src-Family Kinases / Q000378:metabolism
chemical_list: D015214:Antigens, Differentiation, Myelomonocytic; D037102:Lectins; D017382:Reactive Oxygen Species; D063265:Sialic Acid Binding Immunoglobulin-like Lectins; C443130:Siglecf protein, mouse; D019255:NADPH Oxidases; C060902:lyn protein-tyrosine kinase; D019061:src-Family Kinases; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; C509248:Ptpn6 protein, mouse; D020169:Caspases