title: The trans-membrane domain of Bcl-2α, but not its hydrophobic cleft, is a critical determinant for efficient IP3 receptor inhibition.
abstract: The anti-apoptotic Bcl-2 protein is emerging as an efficient inhibitor of IP3R function, contributing to its oncogenic properties. Yet, the underlying molecular mechanisms remain not fully understood. Using mutations or pharmacological inhibition to antagonize Bcl-2's hydrophobic cleft, we excluded this functional domain as responsible for Bcl-2-mediated IP3Rs inhibition. In contrast, the deletion of the C-terminus, containing the trans-membrane domain, which is only present in Bcl-2α, but not in Bcl-2β, led to impaired inhibition of IP3R-mediated Ca2+ release and staurosporine-induced apoptosis. Strikingly, the trans-membrane domain was sufficient for IP3R binding and inhibition. We therefore propose a novel model, in which the Bcl-2's C-terminus serves as a functional anchor, which beyond mere ER-membrane targeting, underlies efficient IP3R inhibition by (i) positioning the BH4 domain in the close proximity of its binding site on IP3R, thus facilitating their interaction; (ii) inhibiting IP3R-channel openings through a direct interaction with the C-terminal region of the channel downstream of the channel-pore. Finally, since the hydrophobic cleft of Bcl-2 was not involved in IP3R suppression, our findings indicate that ABT-199 does not interfere with IP3R regulation by Bcl-2 and its mechanism of action as a cell-death therapeutic in cancer cells likely does not involve Ca2+ signaling.
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Hristina
authors: H
authors: Ivanova
authors: Inserm U-1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer et LABEX (Laboratoire d'excellence), Université Lille1, 59655 Villeneuve d'Ascq, France.
authors: Abigael
authors: A
authors: Ritaine
authors: University of Rochester Medical Center School of Medicine and Dentistry, Rochester, NY 14642, USA.
authors: Larry
authors: L
authors: Wagner
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Tomas
authors: T
authors: Luyten
authors: Inserm U-1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer et LABEX (Laboratoire d'excellence), Université Lille1, 59655 Villeneuve d'Ascq, France.
authors: George
authors: G
authors: Shapovalov
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Kirsten
authors: K
authors: Welkenhuyzen
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Bruno
authors: B
authors: Seitaj
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Giovanni
authors: G
authors: Monaco
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Humbert
authors: H
authors: De Smedt
authors: Inserm U-1003, Equipe Labellisée par la Ligue Nationale Contre le Cancer et LABEX (Laboratoire d'excellence), Université Lille1, 59655 Villeneuve d'Ascq, France.
authors: Natalia
authors: N
authors: Prevarskaya
authors: University of Rochester Medical Center School of Medicine and Dentistry, Rochester, NY 14642, USA.
authors: David I
authors: DI
authors: Yule
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Jan B
authors: JB
authors: Parys
authors: Katholieke Universiteit Leuven, Laboratory of Molecular and Cellular Signaling, Department of Cellular and Molecular Medicine and Leuven Cancer Institute (LKI), BE-3000 Leuven, Belgium.
authors: Geert
authors: G
authors: Bultynck
mesh_terms: D017209:Apoptosis; D019086:Bridged Bicyclo Compounds, Heterocyclic / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000037:antagonists & inhibitors* / Q000737:chemistry; D000072417:Protein Domains; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry*; D013449:Sulfonamides / Q000494:pharmacology
chemical_list: D019086:Bridged Bicyclo Compounds, Heterocyclic; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019253:Proto-Oncogene Proteins c-bcl-2; D013449:Sulfonamides; C579720:venetoclax; D002118:Calcium
keywords: IP3 receptor; anti-apoptotic Bcl-2; calcium signaling; hydrophobic cleft; trans-membrane domain