title: Selective regulation of IP3-receptor-mediated Ca2+ signaling and apoptosis by the BH4 domain of Bcl-2 versus Bcl-Xl.
abstract: Antiapoptotic B-cell lymphoma 2 (Bcl-2) targets the inositol 1,4,5-trisphosphate receptor (IP(3)R) via its BH4 domain, thereby suppressing IP(3)R Ca(2+)-flux properties and protecting against Ca(2+)-dependent apoptosis. Here, we directly compared IP(3)R inhibition by BH4-Bcl-2 and BH4-Bcl-Xl. In contrast to BH4-Bcl-2, BH4-Bcl-Xl neither bound the modulatory domain of IP(3)R nor inhibited IP(3)-induced Ca(2+) release (IICR) in permeabilized and intact cells. We identified a critical residue in BH4-Bcl-2 (Lys17) not conserved in BH4-Bcl-Xl (Asp11). Changing Lys17 into Asp in BH4-Bcl-2 completely abolished its IP(3)R-binding and -inhibitory properties, whereas changing Asp11 into Lys in BH4-Bcl-Xl induced IP(3)R binding and inhibition. This difference in IP(3)R regulation between BH4-Bcl-2 and BH4-Bcl-Xl controls their antiapoptotic action. Although both BH4-Bcl-2 and BH4-Bcl-Xl had antiapoptotic activity, BH4-Bcl-2 was more potent than BH4-Bcl-Xl. The effect of BH4-Bcl-2, but not of BH4-Bcl-Xl, depended on its binding to IP(3)Rs. In agreement with the IP(3)R-binding properties, the antiapoptotic activity of BH4-Bcl-2 and BH4-Bcl-Xl was modulated by the Lys/Asp substitutions. Changing Lys17 into Asp in full-length Bcl-2 significantly decreased its binding to the IP(3)R, its ability to inhibit IICR and its protection against apoptotic stimuli. A single amino-acid difference between BH4-Bcl-2 and BH4-Bcl-Xl therefore underlies differential regulation of IP(3)Rs and Ca(2+)-driven apoptosis by these functional domains. Mutating this residue affects the function of Bcl-2 in Ca(2+) signaling and apoptosis.
authors.affiliation: Laboratory of Molecular and Cellular Signaling, Department of Molecular Cell Biology, Campus Gasthuisberg O/N-1 bus 802, Herestraat 49, BE-3000 Leuven, Belgium.
authors.forename: G
authors.initials: G
authors.lastname: Monaco
authors.forename: E
authors.initials: E
authors.lastname: Decrock
authors.forename: H
authors.initials: H
authors.lastname: Akl
authors.forename: R
authors.initials: R
authors.lastname: Ponsaerts
authors.forename: T
authors.initials: T
authors.lastname: Vervliet
authors.forename: T
authors.initials: T
authors.lastname: Luyten
authors.forename: M
authors.initials: M
authors.lastname: De Maeyer
authors.forename: L
authors.initials: L
authors.lastname: Missiaen
authors.forename: C W
authors.initials: CW
authors.lastname: Distelhorst
authors.forename: H
authors.initials: H
authors.lastname: De Smedt
authors.forename: J B
authors.initials: JB
authors.lastname: Parys
authors.forename: L
authors.initials: L
authors.lastname: Leybaert
authors.forename: G
authors.initials: G
authors.lastname: Bultynck
mesh_terms: D000595:Amino Acid Sequence; D000596:Amino Acids / Q000378:metabolism; D000818:Animals; D017209:Apoptosis; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling; D019610:Cytoprotection; D055767:Immobilized Proteins / Q000378:metabolism; D053496:Inositol 1,4,5-Trisphosphate Receptors / Q000737:chemistry* / Q000378:metabolism*; D051379:Mice; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000737:chemistry / Q000378:metabolism*; D051381:Rats; D016415:Sequence Alignment; D013329:Structure-Activity Relationship; D051020:bcl-X Protein / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000596:Amino Acids; D055767:Immobilized Proteins; D053496:Inositol 1,4,5-Trisphosphate Receptors; D019253:Proto-Oncogene Proteins c-bcl-2; D051020:bcl-X Protein; D002118:Calcium