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apoptosis regulator The Bcl-2 (Bcl-2) Family (TC 1.A.21) The Bcl-2 family consists of the apoptosis regulator, Bcl-X, and its homologues. Bcl-X is a dominant regulator of programmed cell death in mammalian cells. The long form (Bcl-X(L)) displays cell death repressor activity, but the short isoform (Bcl-X(S)) and the b-isoform (Bcl-Xb) promote cell death. Bcl-X(L), Bcl-X(S) and Bcl-Xb are three isoforms derived by alternative RNA splicing. Bcl-X(S) forms heterodimers with Bcl-2. Homologues of Bcl-X include the Bax (rat; 192 aas; spQ63690) and Bak (mouse; 208 aas; spO08734) proteins which also influence apoptosis. Using isolated mitochondria, recombinant Bax and Bak have been shown to induce Dy loss, swelling and cytochrome c release. All of these changes are dependent on Ca2+ and are prevented by cyclosporin A and bongkrekic acid, both of which are known to close permeability transition pores (megachannels). Coimmimoprecipitation studies revealed that Bax and Bak interact with VDAC to form permeability transition pores. Thus, even though they can form channels in artificial membranes at acidic pH, proapoptotic Bcl-2 family proteins (including Bax and Bak) probably induce the mitochondrial permeability transition and cytochrome c release by interacting with permeability transition pores, the most important component for pore fomation of which is VDAC. [Regulatory functions, Other] |
Jiyao W et al.(2023). "The conserved domain database in 2023.",