title: Tissue transglutaminase triggers oligomerization and activation of dual leucine zipper-bearing kinase in calphostin C-treated cells to facilitate apoptosis.
abstract: Although tissue transglutaminase (tTG) has been recognized as a mediator of apoptosis in various experimental models, little is currently known about the molecular mechanisms by which this protein modulates cell death. Recent work from our laboratory has shown that activation of tTG in cells exposed to the apoptotic inducer calphostin C triggers the crosslinking of dual leucine zipper-bearing kinase (DLK), a proapoptotic kinase acting as an essential component of the c-Jun amino-terminal kinase (JNK) signaling pathway. As a consequence of this observation, we have undertaken experiments to investigate the functional relevance of DLK oligomerization in tTG-mediated apoptosis. Our results indicate that, in cells undergoing calphostin C-induced apoptosis, tTG-dependent DLK oligomerization occurs early in the apoptotic response. Both immunocomplex kinase assays and immunoblotting with phosphospecific antibodies revealed that oligomer formation by tTG-mediated crosslinking reactions significantly enhanced the kinase activity of DLK and its ability to activate the JNK pathway. Moreover, functional studies demonstrate that tTG-mediated oligomerization of wild-type DLK sensitizes cells to calphostin C-induced apoptosis, while crosslinking of a kinase-inactive variant of DLK does not. Collectively, these data strongly suggest that tTG facilitates apoptosis, at least partly, by oligomerization and activation of the proapoptotic kinase DLK.
authors.affiliation: Département de biologie, Faculté des sciences, Université de Sherbrooke, Sherbrooke, Québec J1K 2R1, Canada.
authors.forename: K
authors.initials: K
authors.lastname: Robitaille
authors.forename: A
authors.initials: A
authors.lastname: Daviau
authors.forename: J
authors.initials: J
authors.lastname: Tucholski
authors.forename: G V W
authors.initials: GV
authors.lastname: Johnson
authors.forename: C
authors.initials: C
authors.lastname: Rancourt
authors.forename: R
authors.initials: R
authors.lastname: Blouin
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000187:drug effects* / Q000502:physiology; D019556:COS Cells; D002478:Cells, Cultured; D002522:Chlorocebus aethiops; D019281:Dimerization; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism; D048670:MAP Kinase Kinase 4; D020930:MAP Kinase Kinase Kinases / Q000378:metabolism*; D051379:Mice; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism; D041681:NIH 3T3 Cells; D009281:Naphthalenes / Q000494:pharmacology*; D011065:Poly(ADP-ribose) Polymerases / Q000378:metabolism; D011503:Transglutaminases / Q000378:metabolism*
chemical_list: D009281:Naphthalenes; D011503:Transglutaminases; D011065:Poly(ADP-ribose) Polymerases; D048031:JNK Mitogen-Activated Protein Kinases; D020930:MAP Kinase Kinase Kinases; C090757:mitogen-activated protein kinase kinase kinase 12; D048670:MAP Kinase Kinase 4; D020929:Mitogen-Activated Protein Kinase Kinases; C058819:calphostin C