title: The Bcl-2/Bcl-xL inhibitor BH3I-2' affects the dynamics and subcellular localization of sumoylated proteins.
abstract: Sumoylation modulates many proteins implicated in apoptosis such as Fas, TNFR1, Daxx, p53 and its regulator MDM2. Some of these proteins, such as DRP-1, are involved in the intrinsic apoptosis pathway. The intrinsic pathway is regulated at the mitochondrial level by the Bcl-2 family of proteins. The small-molecule inhibitor BH3I-2' binds to the hydrophobic groove of the BH3 domain of anti-apoptotic proteins Bcl-xL and Bcl-2. Following treatment with this inhibitor in various experimental conditions, we observed decreased levels of detergent-soluble SUMO-1, an increase in the relative levels of detergent-insoluble sumoylated proteins, or both. Accordingly, immunofluorescence microscopy revealed that the relative numbers and intensities of endogenously or exogenously expressed SUMO-1 foci in the nucleus were increased following BH3I-2' treatment. MG132 caused a large increase in steady-state levels of SUMO-1 and of sumoylated proteins, and this was especially true for detergent-insoluble proteins. The conjugation-incompetent GG-to-AA SUMO-1 mutant, which did not form nuclear foci, was only present in the detergent-soluble lysate fraction and was insensitive to BH3I-2', implying that BH3I-2' specifically affects SUMO in its conjugated form. Finally, BH3I-2' had similar effects on SUMO-2 and SUMO-3 as it had on SUMO-1. In conclusion, BH3I-2' causes an intracellular redistribution of sumoylated proteins, more specifically their targeting to PML and non-PML nuclear bodies in which they may be degraded by the proteasome. Interestingly, knocking down Bcl-2 also altered levels of sumoylated proteins and their presence in detergent-insoluble compartments, confirming the role of Bcl-2 as a modulator of the sumoylation pathway.
authors: Laboratory of Retrovirology, Université du Québec à Trois-Rivières, 3351, Boulevard des Forges, C.P. 500, Trois-Rivières, Quebec, Canada G9A 5H7.
authors: Mélodie B
authors: MB
authors: Plourde
authors: Aïda
authors: A
authors: Morchid
authors: Lolita
authors: L
authors: Iranezereza
authors: Lionel
authors: L
authors: Berthoux
mesh_terms: D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D017209:Apoptosis / Q000187:drug effects; D001549:Benzamides / Q000494:pharmacology*; D002460:Cell Line; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D055785:Gene Knockdown Techniques; D006801:Humans; D042541:Intracellular Space / Q000187:drug effects* / Q000378:metabolism*; D061988:Proteasome Inhibitors / Q000494:pharmacology; D025842:SUMO-1 Protein / Q000378:metabolism / Q000494:pharmacology; D058207:Sumoylation / Q000187:drug effects*; D051020:bcl-X Protein / Q000037:antagonists & inhibitors*
chemical_list: C474172:3-iodo-5-chloro-N-(2-chloro-5-((4-chlorophenyl)sulphonyl)phenyl)-2-hydroxybenzamide; D001549:Benzamides; D061988:Proteasome Inhibitors; D025842:SUMO-1 Protein; D051020:bcl-X Protein