title: Processing and secretion of guanylate binding protein-1 depend on inflammatory caspase activity.
abstract: Human guanylate binding protein-1 (GBP-1) belongs to the family of large GTPases. The expression of GBP-1 is inducible by inflammatory cytokines, and the protein is involved in inflammatory processes and host defence against cellular pathogens. GBP-1 is the first GTPase which was described to be secreted by eukaryotic cells. Here, we report that precipitation of GBP-1 with GMP-agarose from cell culture supernatants co-purified a 47-kD fragment of GBP-1 (p47-GBP-1) in addition to the 67-kD full-length form. MALDI-TOF sequencing revealed that p47-GBP-1 corresponds to the C-terminal helical part of GBP-1 and lacks most of the globular GTPase domain. In silico analyses of protease target sites, together with cleavage experiments in vitro and in vivo, showed that p67-GBP-1 is cleaved by the inflammatory caspases 1 and 5, leading to the formation of p47-GBP-1. Furthermore, the secretion of p47-GBP-1 was found to occur via a non-classical secretion pathway and to be dependent on caspase-1 activity but independent of inflammasome activation. Finally, we showed that p47-GBP-1 represents the predominant form of secreted GBP-1, both in cell culture supernatants and, in vivo, in the cerebrospinal fluid of patients with bacterial meningitis, indicating that it may represent the biologically active form of extracellular GBP-1. These findings confirm the involvement of caspase-1 in non-classical secretion mechanisms and open novel perspectives for the extracellular function of secreted GBP-1.
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen, Translational Research Center, Erlangen, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Naschberger
authors.affiliation: Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen, Erlangen, Germany.
authors.forename: Walter
authors.initials: W
authors.lastname: Geißdörfer
authors.affiliation: Mikrobiologisches Institut - Klinische Mikrobiologie, Immunologie und Hygiene, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen, Erlangen, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Bogdan
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen, Translational Research Center, Erlangen, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Tripal
authors.affiliation: Institute of Molecular Immunology, Helmholtz Zentrum Munich, German Research Center for Environmental Health, Munich, Germany.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Kremmer
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen, Translational Research Center, Erlangen, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Stürzl
authors.affiliation: Division of Molecular and Experimental Surgery, Department of Surgery, Friedrich-Alexander-Universität (FAU) Erlangen-Nürnberg and Universitätsklinikum Erlangen, Translational Research Center, Erlangen, Germany.
authors.forename: Nathalie
authors.identifier: 0000-0002-0494-7117
authors.initials: N
authors.lastname: Britzen-Laurent
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000595:Amino Acid Sequence; D020170:Caspase 1 / Q000378:metabolism; D005260:Female; D019204:GTP-Binding Proteins / Q000134:cerebrospinal fluid / Q000737:chemistry / Q000378:metabolism*; D061307:Human Umbilical Vein Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism; D007249:Inflammation / Q000378:metabolism* / Q000473:pathology*; D007371:Interferon-gamma / Q000494:pharmacology; D008297:Male; D016920:Meningitis, Bacterial / Q000134:cerebrospinal fluid / Q000378:metabolism; D008875:Middle Aged; D008970:Molecular Weight; D011499:Protein Processing, Post-Translational / Q000187:drug effects; D055815:Young Adult
chemical_list: C490287:GBP1 protein, human; D058847:Inflammasomes; D007371:Interferon-gamma; D020170:Caspase 1; D019204:GTP-Binding Proteins
keywords: 
  HUVEC
  ; GTPase; Inflammation; Secretion; caspase-1; caspase-5; endothelial cells; guanylate binding protein; interferon