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Bcl-2 Family

The Bcl-2 family of proteins is characterized by the presence of at least one Bcl-2 homology (BH) domain. There are a total of 25 members in the Bcl-2 family known to date, which are further divided into three subfamilies: anti-apoptotic group, pro-apoptotic group, and BH3-only proteins. The BH3-only proteins are largely responsible for sensing the apoptotic signals and then transmitting them to other Bcl-2 family members. Bcl-2-family proteins regulate all major types of cell death, including apoptosis, necrosis and autophagy, thus operating as nodal points at the convergence of multiple pathways with broad relevance to oncology.

Sino Biological provides a comprehensive set of tools for Bcl-2 family related studies, including proteins, antibodies (rabbit mAbs, mouse mAbs, and rabbit pAbs), ELISA kits, and ORF cDNA clones.

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    Bcl-2 Family Background

    The Bcl-2 family of proteins is characterized by the presence of at least one Bcl-2 homology (BH) domain. These proteins govern mitochondrial outer membrane permeabilization (MOMP) and can be either pro-apoptotic or anti-apoptotic. The founding member of the Bcl-2 protein family, Bcl-2 itself, was discovered during molecular analysis of the t14–18 chromosomal translocation in B cell lymphoma. Since then, the family has grown to ∼20 members; there are a total of 25 genes in the Bcl-2 family known to date. All Bcl-2 family proteins contain at least one of the four conserved α-helical motifs known as Bcl-2 homology (BH1, BH2, BH3, and BH4) domains. These proteins are further divided into three subfamilies based on their function and structure. The anti-apoptotic members include Bcl-2, Bcl-XL, Mcl-1, Bcl-w and A1/Bfl1. The second subfamily is the pro-apoptotic group, highlighted by Bax and Bak. Finally, the third subfamily is the BH3-only group, so named because their sequence homology with the rest of the family is restricted to the BH3 domain. The BH3-only proteins are largely responsible for sensing the apoptotic signals and then transmitting them to other Bcl-2 family members.

    Apoptosis is a critical process for the maintenance of tissue homeostasis and prevention of tumorigenesis. Proteins of the Bcl-2 family are the central regulators of the intrinsic apoptotic pathway. The BH3-only Bcl-2 family proteins are regarded as the initial responders to incoming stress signals and developmental cues and exhibit both stimulus and cell type-specific activities. They then transmit the stress signals to other Bcl-2 family members. Each BH3-only protein is capable of interacting with some or all of the Bcl-2 family members with differing affinities, allowing for cell- and tissue-specific responses to various stress stimuli. In addition, transcriptional regulation, post-transcriptional modifications, modification of BH3-only proteins and other apoptotic proteins are significant components of stress stimuli response. A lot of enzymes and transcription factors are involved, such as caspases, PI3K/Akt pathway, p53, NFκB, etc.

    Bcl-2-family proteins regulate all major types of cell death, including apoptosis, necrosis and autophagy, thus operating as nodal points at the convergence of multiple pathways with broad relevance to oncology. The Bcl-2 family of proteins is a common target for deregulation in cancer, with several anti-apoptotic members being overexpressed and pro-apoptotic members being mutated or silenced in a variety of tumor types. For example, Bcl-2 was discovered to be overexpressed in human B-cell lymphomas as it is located near chromosomal translocation break points frequently found in those cancers. Further studies demonstrated that Bcl-2 protein levels can be elevated due to loss of promoter methylation, loss of microRNA expression and gene amplifications, indicating that elevated Bcl-2 expression is a significant factor in a number of cancers.

    Bcl-2 Family References

      1. Tsujimoto Y, et al. (1985) Involvement of the bcl-2 gene in human follicular lymphoma. Science. 228(4706):1440-3.
      2. Oltvai ZN, et al. (1993) Bcl-2 heterodimerizes in vivo with a conserved homolog, Bax, that accelerates programmed cell death. Cell 74: 609–619.
      3. Adams JM. (2003) Ways of dying: multiple pathways to apoptosis. Genes Dev 17: 2481–2495.
      4. Yip KW, et al. (2008) Bcl-2 family proteins and cancer. Oncogene. 27(50):6398-406.
      5. Szegezdi E, et al. (2009) Bcl-2 family on guard at the ER. Am J Physiol Cell Physiol. 296(5):C941-53.
      6. Leibowitz B, et al. (2010) Mitochondrial signaling in cell death via the Bcl-2 family. Cancer Biol Ther. 9(6):417-22.