title: Bcl-2 homology domain 3-only proteins Puma and Bim mediate the vulnerability of CA1 hippocampal neurons to proteasome inhibition in vivo.
abstract: Bcl-2 homology domain 3 (BH3)-only proteins are pro-apoptotic Bcl-2 family members that play important roles in upstream cell death signalling during apoptosis. Proteasomal stress has been shown to contribute to the pathology of cerebral ischaemia and many neurodegenerative disorders. Here we explored the contribution of BH3-only proteins in mediating proteasome-inhibition-induced apoptosis in the murine brain in vivo. Stereotactic intrahippocampal microinjection of the selective proteasome inhibitor epoxomicin (2.5 nmol) induced a delayed apoptosis within only the CA1 hippocampal neurons and not neurons within the CA3 or dentate gyrus regions, a selective vulnerability similar to that seen during ischaemia. This injury developed over a time-course of 3 days and was characterized by positive terminal deoxynucleotidyl transferase dUTP nick end labelling staining and nuclear condensation. Previous work from our laboratory has identified the BH3-only protein p53-upregulated mediator of apoptosis (Puma) as mediating proteasome-inhibition-induced apoptosis in cultured neural cells. Genetic deletion of puma reduced the number of terminal deoxynucleotidyl transferase dUTP nick end labelling-positive cells within the CA1 following epoxomicin microinjection but it did not provide a complete protection. Subsequent studies identified the BH3-only protein Bim as also being upregulated during proteasome inhibition in organotypic hippocampal slice cultures and after epoxomicin treatment in vivo. Interestingly, the genetic deletion of bim also afforded significant neuroprotection, although this protection was less pronounced. In summary, we demonstrate that the BH3-only proteins Puma and Bim mediate the delayed apoptosis of CA1 hippocampal neurons induced by proteasome inhibition in vivo, and that either BH3-only protein can only partly compensate for the deficiency of the other.
authors.affiliation: Department of Physiology and Medical Physics and RCSI Neuroscience Research Centre, Royal College of Surgeons in Ireland, 123 St Stephen's Green, Dublin 2, Ireland.
authors.forename: Takuro
authors.initials: T
authors.lastname: Tsuchiya
authors.forename: Helena P
authors.initials: HP
authors.lastname: Bonner
authors.forename: Tobias
authors.initials: T
authors.lastname: Engel
authors.forename: Ina
authors.initials: I
authors.lastname: Woods
authors.forename: Satoshi
authors.initials: S
authors.lastname: Matsushima
authors.forename: Manus W
authors.initials: MW
authors.lastname: Ward
authors.forename: Waro
authors.initials: W
authors.lastname: Taki
authors.forename: David C
authors.initials: DC
authors.lastname: Henshall
authors.forename: Caoimhín G
authors.initials: CG
authors.lastname: Concannon
authors.forename: Jochen H M
authors.initials: JH
authors.lastname: Prehn
mesh_terms: D000818:Animals; D017209:Apoptosis / Q000502:physiology*; D051017:Apoptosis Regulatory Proteins / Q000235:genetics / Q000378:metabolism*; D000072224:Bcl-2-Like Protein 11; D015153:Blotting, Western; D006624:Hippocampus / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D007150:Immunohistochemistry; D020287:In Situ Nick-End Labeling; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009474:Neurons / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D009842:Oligopeptides / Q000633:toxicity; D061988:Proteasome Inhibitors; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D051017:Apoptosis Regulatory Proteins; D000072224:Bcl-2-Like Protein 11; C000606776:Bcl2l11 protein, mouse; D008565:Membrane Proteins; D009842:Oligopeptides; C488588:PUMA protein, mouse; D061988:Proteasome Inhibitors; D011518:Proto-Oncogene Proteins; D025521:Tumor Suppressor Proteins; C078846:epoxomicin