title: Transamidase site-targeted agents alter the conformation of the transglutaminase cancer stem cell survival protein to reduce GTP binding activity and cancer stem cell survival.
abstract: Type 2 transglutaminase (TG2) is an important cancer stem cell survival protein that exists in open and closed conformations. The major intracellular form is the closed conformation that functions as a GTP-binding GTPase and is required for cancer stem cell survival. However, at a finite rate, TG2 transitions to an open conformation that exposes the transamidase catalytic site involved in protein-protein crosslinking. The activities are mutually exclusive, as the closed conformation has GTP binding/GTPase activity, and the open conformation transamidase activity. We recently showed that GTP binding, but not transamidase activity, is required for TG2-dependent cancer stem cell invasion, migration and tumour formation. However, we were surprised that transamidase site-specific inhibitors reduce cancer stem cell survival. We now show that compounds NC9, VA4 and VA5, which react exclusively at the TG2 transamidase site, inhibit both transamidase and GTP-binding activities. Transamidase activity is inhibited by direct inhibitor binding at the transamidase site, and GTP binding is blocked because inhibitor interaction at the transamidase site locks the protein in the extended/open conformation to disorganize/inactivate the GTP binding/GTPase site. These findings suggest that transamidase site-specific inhibitors can inhibit GTP binding/signalling by driving a conformation change that disorganizes the TG2 GTP binding to reduce TG2-dependent signalling, and that drugs designed to target this site may be potent anti-cancer agents.
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: C
authors.initials: C
authors.lastname: Kerr
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: H
authors.initials: H
authors.lastname: Szmacinski
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: M L
authors.initials: ML
authors.lastname: Fisher
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: B
authors.initials: B
authors.lastname: Nance
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: J R
authors.initials: JR
authors.lastname: Lakowicz
authors.affiliation: Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: A
authors.initials: A
authors.lastname: Akbar
authors.affiliation: Department of Chemistry and Biomolecular Sciences, University of Ottawa, Ottawa, Ontario, Canada.
authors.forename: J W
authors.initials: JW
authors.lastname: Keillor
authors.affiliation: Institute for Bioscience and Biotechnology Research and Center for Biomolecular Therapeutics, Rockville, Maryland, USA.
authors.forename: T
authors.initials: T
authors.lastname: Lok Wong
authors.affiliation: Institute for Bioscience and Biotechnology Research and Center for Biomolecular Therapeutics, Rockville, Maryland, USA.
authors.forename: R
authors.initials: R
authors.lastname: Godoy-Ruiz
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|The Marlene and Stewart Greenebaum Cancer Center, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|Institute for Bioscience and Biotechnology Research and Center for Biomolecular Therapeutics, Rockville, Maryland, USA.
authors.forename: E A
authors.initials: EA
authors.lastname: Toth
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|The Marlene and Stewart Greenebaum Cancer Center, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|Institute for Bioscience and Biotechnology Research and Center for Biomolecular Therapeutics, Rockville, Maryland, USA.
authors.forename: D J
authors.initials: DJ
authors.lastname: Weber
authors.affiliation: Department of Biochemistry and Molecular Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|Department of Dermatology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|Department of Reproductive Biology, The University of Maryland School of Medicine, Baltimore, Maryland, USA.|The Marlene and Stewart Greenebaum Cancer Center, The University of Maryland School of Medicine, Baltimore, Maryland, USA.
authors.forename: R L
authors.initials: RL
authors.lastname: Eckert
mesh_terms: D019881:Aminoacyltransferases / Q000037:antagonists & inhibitors* / Q000737:chemistry; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001665:Binding Sites / Q000187:drug effects; D020134:Catalytic Domain / Q000187:drug effects / Q000235:genetics; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002478:Cells, Cultured; D019204:GTP-Binding Proteins / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D055786:Gene Knockout Techniques; D006160:Guanosine Triphosphate / Q000378:metabolism*; D006801:Humans; D058990:Molecular Targeted Therapy; D014411:Neoplastic Stem Cells / Q000187:drug effects* / Q000502:physiology*; D011485:Protein Binding / Q000187:drug effects; D011487:Protein Conformation / Q000187:drug effects; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases / Q000037:antagonists & inhibitors* / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism
chemical_list: D000970:Antineoplastic Agents; D006160:Guanosine Triphosphate; D019881:Aminoacyltransferases; C023175:transamidases; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; D019204:GTP-Binding Proteins