bcl-2 bcl-2 bcl-2 (b-cell lymphoma 2), encoded in humans by the bcl2 gene, is the founding member of the bcl-2 family of regulator proteins that regulate cell death (apoptosis), by either inhibiting (anti-apoptotic) or inducing (pro-apoptotic) apoptosis. it was the first apoptosis regulator identified in any organism. bcl2available structurespdbortholog search: pdbe rcsb list of pdb id codes1g5m, 1gjh, 1ysw, 2o21, 2o22, 2o2f, 2w3l, 2xa0, 4aq3, 4ieh, 4lvt, 4lxd, 4man, 5agw, 5agx, 5fcgidentifiersaliasesbcl2, bcl-2, ppp1r50, b-cell cll/lymphoma 2, apoptosis regulator, bcl2 apoptosis regulator, genes, bcl-2external idsomim: 151430 mgi: 88138 homologene: 527 genecards: bcl2 gene location (human)chr.chromosome 18 (human)band18q21.33start63,123,346 bpend63,320,128 bpgene location (mouse)chr.chromosome 1 (mouse)band1 e2.1|1 49.76 cmstart106,465,908 bpend106,642,004 bprna expression patternbgeehumanmouse (ortholog)top expressed insuperficial temporal arteryachilles tendoninferior olivary nucleusoptic nervetrigeminal ganglioninternal globus pallidusexternal globus palliduscaput epididymisseminal vesiculalymph nodetop expressed inascending aortaaortic valveirisciliary bodybloodvas deferensretinal pigment epitheliumpaneth cellspleendermismore reference expression databiogpsmore reference expression datagene ontologymolecular function protein phosphatase binding transcription factor binding protein phosphatase 2a binding channel inhibitor activity protein homodimerization activity channel activity protease binding protein binding sequence-specific dna binding bh3 domain binding identical protein binding protein heterodimerization activity ubiquitin protein ligase binding cellular component cytoplasm cytosol nuclear membrane membrane mitochondrion nucleus mitochondrial membrane myelin sheath mitochondrial outer membrane endoplasmic reticulum pore complex integral component of membrane intracellular anatomical structure endoplasmic reticulum membrane nucleoplasm protein-containing complex biological process negative regulation of neuron apoptotic process intrinsic apoptotic signaling pathway in response to oxidative stress ureteric bud development renal system process organ growth t cell differentiation in thymus lymphocyte homeostasis response to steroid hormone positive regulation of catalytic activity ear development glomerulus development post-embryonic development cellular response to dna damage stimulus t cell homeostasis negative regulation of ossification negative regulation of g1/s transition of mitotic cell cycle positive regulation of smooth muscle cell migration regulation of protein localization t cell differentiation b cell lineage commitment response to ischemia regulation of mitochondrial membrane permeability humoral immune response defense response to virus mesenchymal cell development positive regulation of multicellular organism growth animal organ morphogenesis developmental pigmentation hair follicle morphogenesis b cell differentiation cell population proliferation metanephros development melanocyte differentiation negative regulation of autophagy positive regulation of neuron maturation negative regulation of myeloid cell apoptotic process cellular response to hypoxia pigment granule organization negative regulation of cell population proliferation b cell receptor signaling pathway cellular response to organic substance regulation of apoptotic process response to cytokine cellular response to glucose starvation regulation of protein stability ossification positive regulation of melanocyte differentiation axon regeneration kidney development actin filament organization thymus development negative regulation of intrinsic apoptotic signaling pathway negative regulation of apoptotic signaling pathway response to nicotine spleen development endoplasmic reticulum calcium ion homeostasis positive regulation of skeletal muscle fiber development response to oxidative stress lymphoid progenitor cell differentiation positive regulation of peptidyl-serine phosphorylation cd8-positive, alpha-beta t cell lineage commitment reactive oxygen species metabolic process negative regulation of retinal cell programmed cell death branching involved in ureteric bud morphogenesis gland morphogenesis positive regulation of cell growth positive regulation of b cell proliferation negative regulation of cell growth response to gamma radiation positive regulation of intrinsic apoptotic signaling pathway response to toxic substance digestive tract morphogenesis neuron apoptotic process male gonad development regulation of protein heterodimerization activity regulation of glycoprotein biosynthetic process regulation of viral genome replication female pregnancy negative regulation of mitochondrial depolarization protein dephosphorylation protein polyubiquitination cellular calcium ion homeostasis b cell homeostasis behavioral fear response oocyte development regulation of cell-matrix adhesion response to iron ion negative regulation of cell migration regulation of autophagy positive regulation of developmental pigmentation developmental growth regulation of transmembrane transporter activity ovarian follicle development regulation of gene expression negative regulation of calcium ion transport into cytosol negative regulation of osteoblast proliferation homeostasis of number of cells within a tissue pigmentation response to radiation regulation of catalytic activity peptidyl-threonine phosphorylation regulation of protein homodimerization activity negative regulation of anoikis response to hydrogen peroxide t cell lineage commitment cochlear nucleus development leukocyte homeostasis regulation of programmed cell death regulation of calcium ion transport axonogenesis negative regulation of cellular ph reduction response to glucocorticoid regulation of cell cycle regulation of mitochondrial membrane potential melanin metabolic process focal adhesion assembly positive regulation of protein insertion into mitochondrial membrane involved in apoptotic signaling pathway b cell proliferation intrinsic apoptotic signaling pathway in response to endoplasmic reticulum stress immune system development apoptotic mitochondrial changes peptidyl-serine phosphorylation regulation of nitrogen utilization cell morphogenesis positive regulation of cell population proliferation negative regulation of reactive oxygen species metabolic process response to uv-b regulation of developmental pigmentation negative regulation of extrinsic apoptotic signaling pathway in absence of ligand extrinsic apoptotic signaling pathway via death domain receptors release of cytochrome c from mitochondria negative regulation of mitotic cell cycle extrinsic apoptotic signaling pathway in absence of ligand apoptotic process transmembrane transport intrinsic apoptotic signaling pathway in response to dna damage growth cell-cell adhesion cytokine-mediated signaling pathway negative regulation of apoptotic process hemopoiesis regulation of growth negative regulation of intrinsic apoptotic signaling pathway in response to dna damage by p53 class mediator sources:amigo / quickgoorthologsspecieshumanmouseentrez59612043ensemblensg00000171791ensmusg00000057329uniprotp10415p10417refseq (mrna)nm_000633nm_000657nm_009741nm_177410refseq (protein)np_000624np_000648np_033871np_803129location (ucsc)chr 18: 63.12 – 63.32 mbchr 1: 106.47 – 106.64 mbpubmed searchwikidataview/edit humanview/edit mouse bcl-2 derives its name from b-cell lymphoma 2, as it is the second member of a range of proteins initially described in chromosomal translocations involving chromosomes 14 and 18 in follicular lymphomas. orthologs (such as bcl2 in mice) have been identified in numerous mammals for which complete genome data are available. like bcl3, bcl5, bcl6, bcl7a, bcl9, and bcl10, it has clinical significance in lymphoma. isoforms the two isoforms of bcl-2, isoform 1, and isoform 2, exhibit a similar fold. however, results in the ability of these isoforms to bind to the bad and bak proteins, as well as in the structural topology and electrostatic potential of the binding groove, suggest differences in antiapoptotic activity for the two isoforms. normal physiological function bcl-2 is localized to the outer membrane of mitochondria, where it plays an important role in promoting cellular survival and inhibiting the actions of pro-apoptotic proteins. the pro-apoptotic proteins in the bcl-2 family, including bax and bak, normally act on the mitochondrial membrane to promote permeabilization and release of cytochrome c and ros, that are important signals in the apoptosis cascade. these pro-apoptotic proteins are in turn activated by bh3-only proteins, and are inhibited by the function of bcl-2 and its relative bcl-xl. there are additional non-canonical roles of bcl-2 that are being explored. bcl-2 is known to regulate mitochondrial dynamics, and is involved in the regulation of mitochondrial fusion and fission. additionally, in pancreatic beta-cells, bcl-2 and bcl-xl are known to be involved in controlling metabolic activity and insulin secretion, with inhibition of bcl-2/xl showing increasing metabolic activity, but also additional ros production; this suggests it has a protective metabolic effect in conditions of high demand. role in disease damage to the bcl-2 gene has been identified as a cause of a number of cancers, including melanoma, breast, prostate, chronic lymphocytic leukemia, and lung cancer, and a possible cause of schizophrenia and autoimmunity. it is also a cause of resistance to cancer treatments. cancer cancer can be seen as a disturbance in the homeostatic balance between cell growth and cell death. over-expression of anti-apoptotic genes, and under-expression of pro-apoptotic genes, can result in the lack of cell death that is characteristic of cancer. an example can be seen in lymphomas. the over-expression of the anti-apoptotic bcl-2 protein in lymphocytes alone does not cause cancer. but simultaneous over-expression of bcl-2 and the proto-oncogene myc may produce aggressive b-cell malignancies including lymphoma. in follicular lymphoma, a chromosomal translocation commonly occurs between the fourteenth and the eighteenth chromosomes – t(14;18) – which places the bcl-2 gene from chromosome 18 next to the immunoglobulin heavy chain locus on chromosome 14. this fusion gene is deregulated, leading to the transcription of excessively high levels of bcl-2. this decreases the propensity of these cells for apoptosis. bcl-2 expression is frequent in small cell lung cancer, accounting for 76% cases in one study. auto-immune diseases apoptosis plays an active role in regulating the immune system. when it is functional, it can cause immune unresponsiveness to self-antigens via both central and peripheral tolerance. in the case of defective apoptosis, it may contribute to etiological aspects of autoimmune diseases. the autoimmune disease type 1 diabetes can be caused by defective apoptosis, which leads to aberrant t cell aicd and defective peripheral tolerance. due to the fact that dendritic cells are the immune system's most important antigen-presenting cells, their activity must be tightly regulated by mechanisms such as apoptosis. researchers have found that mice containing dendritic cells that are bim -/-, thus unable to induce effective apoptosis, have autoimmune diseases more so than those that have normal dendritic cells. other studies have shown that dendritic cell lifespan may be partly controlled by a timer dependent on anti-apoptotic bcl-2. other apoptosis plays an important role in regulating a variety of diseases. for example, schizophrenia is a psychiatric disorder in which an abnormal ratio of pro- and anti-apoptotic factors may contribute towards pathogenesis. some evidence suggests that this may result from abnormal expression of bcl-2 and increased expression of caspase-3. diagnostic use antibodies to bcl-2 can be used with immunohistochemistry to identify cells containing the antigen. in healthy tissue, these antibodies react with b-cells in the mantle zone, as well as some t-cells. however, positive cells increase considerably in follicular lymphoma, as well as many other forms of cancer. in some cases, the presence or absence of bcl-2 staining in biopsies may be significant for the patient's prognosis or likelihood of relapse. targeted therapies targeted and selective bcl-2 inhibitors that have been in development or are currently in the clinic include: oblimersen an antisense oligonucleotide drug, oblimersen (g3139), was developed by genta incorporated to target bcl-2. an antisense dna or rna strand is non-coding and complementary to the coding strand (which is the template for producing respectively rna or protein). an antisense drug is a short sequence of rna that hybridises with and inactivates mrna, preventing the protein from being formed. human lymphoma cell proliferation (with t(14;18) translocation) could be inhibited by antisense rna targeted at the start codon region of bcl-2 mrna. in vitro studies led to the identification of genasense, which is complementary to the first 6 codons of bcl-2 mrna. these showed successful results in phase i/ii trials for lymphoma. a large phase iii trial was launched in 2004. as of 2016, the drug had not been approved and its developer was out of business. abt-737 and navitoclax (abt-263) in the mid-2000s, abbott laboratories developed a novel inhibitor of bcl-2, bcl-xl and bcl-w, known as abt-737. this compound is part of a group of bh3 mimetic small molecule inhibitors (smi) that target these bcl-2 family proteins, but not a1 or mcl-1. abt-737 is superior to previous bcl-2 inhibitors given its higher affinity for bcl-2, bcl-xl and bcl-w. in vitro studies showed that primary cells from patients with b-cell malignancies are sensitive to abt-737. abt-737 does not directly induce apoptosis; it enhances the effects of apoptotic signals and causes single-agent-mechanism-based killing of cells in small-cell lung carcinoma and lymphoma lines. in animal models, it improves survival, causes tumor regression and cures a high percentage of mice. in preclinical studies utilizing patient xenografts, abt-737 showed efficacy for treating lymphoma and other blood cancers. because of its unfavorable pharmacologic properties abt-737 is not appropriate for clinical trials, while its orally bioavailable derivative navitoclax (abt-263) has similar activity on small cell lung cancer (sclc) cell lines and has entered clinical trials. while clinical responses with navitoclax were promising, mechanistic dose-limiting thrombocytopenia was observed in patients under treatment due to bcl-xl inhibition in platelets. venetoclax (abt-199) due to dose-limiting thrombocytopenia of navitoclax as a result of bcl-xl inhibition, abbvie successfully developed the highly selective inhibitor venetoclax (abt-199), which inhibits bcl-2, but not bcl-xl or bcl-w. clinical trials studied the effects of venetoclax, a bh3-mimetic drug designed to block the function of the bcl-2 protein, on patients with chronic lymphocytic leukemia (cll). good responses have been reported and thrombocytopenia was no longer observed. a phase 3 trial started in dec 2015. it was approved by the us fda in april 2016 as a second-line treatment for cll associated with 17-p deletion. this was the first fda approval of a bcl-2 inhibitor. in