Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Incubation with the Bcl-2 antibody before fixation of tissues allowed good localization of the antigenic determinant. We showed that the Bcl-2 gene product in centroblastic-centrocytic lymphoma is mainly localized on the outer mitochondrial membrane and, to a lesser degree, on the nuclear envelope. No significant staining was found in other cytoplasmic domains. Careful examination also revealed that gold particles did not recognize an integral membrane epitope, but an antigenic determinant localized at a short distance from the cytoplasmic side of the membrane itself. This observation suggests that, by interacting with other cytoplasmic proteins, Bcl-2 plays some role in the cytoplasmic machinery involved in the regulation of programmed cell death.
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PMID:Localization of the Bcl-2 protein to the outer mitochondrial membrane by electron microscopy. 749 35

Apoptosis is a new concept which could be of great importance in the understanding and treatment of cancer. An important feature is the discovery of inhibitors of apoptosis, because they induce resistance to chemotherapeutic drugs and irradiation. Bcl-2 is the most well known of these apoptosis inhibitors. When it is overexpressed cells are less sensitive to cytotoxic drugs; on the contrary, when it is underexpressed they are more sensitive. Clinically, bcl-2 expression is associated with a poor prognosis in several cancers. Bcl-2 protein, p26-bcl-2, is located in the outer mitochondrial membrane, the nuclear envelope and the smooth endoplasmic reticulum. P26-bcl-2 is an antioxidant; this property could explain the anti-apoptotic activity since peroxides seem to be important mediators of apoptosis. Bcl-2 antisense oligonucleotides are able to reverse the apoptosis inhibition. New cancer treatments should take into account the expression of bcl-2.
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PMID:Anticancer drug resistance and inhibition of apoptosis. 782 61

The protein product of the oncogene bcl-2 is a potent inhibitor of apoptotic cell death. The Bcl-2 protein has variously been reported to reside in the nuclear envelope and endoplasmic reticulum or exclusively in the inner membrane of mitochondria. We therefore undertook a detailed analysis of the intracellular distribution of Bcl-2 by immunofluorescence, immunogold electron microscopy, and subcellular fractionation in three mouse cell lines expressing a human bcl-2 transgene and measured its importation into isolated mitochondria. By these methods, the protein was localized to the nuclear envelope, the endoplasmic reticulum, and the outer mitochondrial membrane. Any proposal for the mechanism by which Bcl-2 inhibits apoptosis must therefore accommodate the fact that Bcl-2 localizes to cytoplasmic membranes facing the cytosol.
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PMID:The protein product of the oncogene bcl-2 is a component of the nuclear envelope, the endoplasmic reticulum, and the outer mitochondrial membrane. 804 15

The Bcl-2 protein blocks programmed cell death and becomes overproduced in many follicular non-Hodgkin's lymphomas as the result of t(14; 18) translocations involving the Bcl-2 gene. Mcl-1 is a recently discovered gene whose encoded protein has significant homology with Bcl-2 but whose function remains unknown. In this study, we compared the in vivo patterns of Bcl-2 and Mcl-1 protein production in normal and neoplastic lymph node biopsies by immunohistochemical means using specific polyclonal antisera. Intracellular Mcl-1 immunoreactivity was located primarily in the cytosol in a punctate pattern and was also seen in association with the nuclear envelope in many cases, similar to the results obtained for Bcl-2, which resides in the outer mitochondrial membrane, nuclear envelope, and endoplasmic reticulum. In 4 of 4 reactive tonsils and 28 of 28 nodes with reactive follicular hyperplasia, reciprocal patterns of Bcl-2 and Mcl-1 protein expression were observed. Bcl-2 immunostaining was highest in mantle zone lymphocytes and absent from most germinal center cells, whereas Mcl-1 immunoreactivity was highest in germinal center lymphocytes and absent from mantle zone lymphocytes. Mcl-1 was also expressed in some interfollicular lymphocytes, particularly those that had the appearance of activated lymphocytes. Similar to the patterns of Bcl-2 and mcl-1 expression seen in reactive nodes, Mcl-1 protein was largely absent from the malignant cells in 2 of 2 mantle cell lymphomas, whereas strong Bcl-2 immunostaining was found in these cells. In contrast to normal nodes, however, the neoplastic follicles of t(14;18) containing follicular non-Hodgkin's lymphomas immunostained positively for both Bcl-2 and Mcl-1 in 24 of 27 cases. Intense immunostaining for Mcl-1 was also observed in Reed-Sternberg cells in 2 of 2 cases of Hodgkin's disease but Bcl-2 immunoreactivity was present at much lower levels. These findings demonstrate that the levels of Mcl-1 and Bcl-2 proteins are differentially regulated in normal and neoplastic cells in lymph nodes and thus suggest different roles for these proteins in the control of cell life and death in these tissues.
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PMID:Immunohistochemical analysis of Mcl-1 and Bcl-2 proteins in normal and neoplastic lymph nodes. 808 35

Bcl-2 is an integral membrane protein that functions as a suppressor of programmed cell death. It contains a COOH-terminal signal anchor sequence that is selective for import and insertion of Bcl-2 into the mitochondrial outer membrane and, by a different mechanism, can also direct the protein to other membrane sites. Deletion of the signal anchor sequence rendered Bcl-2 cytosolic and impaired its ability to prevent apoptotic death of human KB cells infected with a mutant form of adenovirus type 5 that does not make E1B 19-kDa protein. When the predicted transmembrane domain of the Bcl-2 signal anchor was replaced with that of the signal anchor of the yeast outer mitochondrial membrane protein, Mas70p, the Bcl-2/Mas70p hybrid was found to be very similar to Bcl-2 in its distribution within transfected KB cells, in its ability to heterodimerize with Bax, and in its ability to suppress apoptosis. These results are consistent with a model in which the transmembrane segment contributes to the function of Bcl-2 by targeting and anchoring the protein to strategic membrane locations in the cell. Concentration of Bcl-2 at these sites may contribute to its proposed role as regulator, or component, of an antioxidant pathway.
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PMID:Role of membrane anchor domain of Bcl-2 in suppression of apoptosis caused by E1B-defective adenovirus. 820 64

A multidisciplinary approach was taken to investigate the intracellular locations of the 26-kDa integral membrane protein encoded by the bcl-2 gene. Subcellular fractionation analysis of a t(14;18)-containing lymphoma cell line revealed the presence of Bcl-2 protein in nuclear, heavy-membrane, and light-membrane fractions but not in cytosol. Sedimentation of heavy-membrane fractions in Nycodenz and Percoll continuous gradients demonstrated comigration of p26-Bcl-2 with mitochondrial but not other organelle-associated proteins. Fractionation of light-membrane fractions using discontinuous sucrose-gradients revealed association of Bcl-2 protein primarily with lighter-density microsomes (smooth endoplasmic reticulum) as opposed to heavy-density microsomes (rough endoplasmic reticulum). Immune microscopy studies using laser-scanning microscopy, pre- and postembedding electron microscopic methods, and six different anti-Bcl-2 antibodies demonstrated Bcl-2 immunoreactivity in the nuclear envelope and outer mitochondrial membrane in a patchy distribution. Furthermore, anti-Bcl-2 antibody immunoreactivity generally appeared to directly overlie the nuclear envelope in high magnification electron microscopic studies, reminiscent of nuclear pore complexes. Addition of in vitro translated p26-Bcl-2 to isolated translocation-competent mitochondria revealed transmembrane domain-dependent association of Bcl-2 protein with mitochondria but provided no evidence for import into a protease-resistant compartment, consistent with immunomicroscopic localization to the outer mitochondrial membrane. Taken together, the findings demonstrate that p26-Bcl-2 resides primarily in the nuclear envelope, endoplasmic reticulum, and outer mitochondrial membrane in a nonuniform distribution suggestive of participation in protein complexes perhaps involved in some aspect of transport.
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PMID:Investigation of the subcellular distribution of the bcl-2 oncoprotein: residence in the nuclear envelope, endoplasmic reticulum, and outer mitochondrial membranes. 840 48

Bcl-2 belongs to a family of apoptosis-regulatory proteins which incorporate into the outer mitochondrial as well as nuclear membranes. The mechanism by which the proto-oncogene product Bcl-2 inhibits apoptosis is thus far elusive. We and others have shown previously that the first biochemical alteration detectable in cells undergoing apoptosis, well before nuclear changes become manifest, is a collapse of the mitochondrial inner membrane potential (delta psi m), suggesting the involvement of mitochondrial products in the apoptotic cascade. Here we show that mitochondria contain a pre-formed approximately 50-kD protein which is released upon delta psi m disruption and which, in a cell-free in vitro system, causes isolated nuclei to undergo apoptotic changes such as chromatin condensation and internucleosomal DNA fragmentation. This apoptosis-inducing factor (AIF) is blocked by N-benzyloxycarbonyl-Val-Ala-Asp.fluoromethylketone (Z-VAD.fmk), an antagonist of interleukin-1 beta-converting enzyme (ICE)-like proteases that is also an efficient inhibitor of apoptosis in cells. We have tested the effect of Bcl-2 on the formation, release, and action of AIF. When preventing mitochondrial permeability transition (which accounts for the pre-apoptotic delta psi m disruption in cells), Bcl-2 hyperexpressed in the outer mitochondrial membrane also impedes the release of AIF from isolated mitochondria in vitro. In contrast, Bcl-2 does not affect the formation of AIF, which is contained in comparable quantities in control mitochondria and in mitochondria from Bcl-2-hyperexpressing cells. Furthermore, the presence of Bcl-2 in the nuclear membrane does not interfere with the action of AIF on the nucleus, nor does Bcl-2 hyperexpression protect cells against AIF. It thus appears that Bcl-2 prevents apoptosis by favoring the retention of an apoptogenic protease in mitochondria.
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PMID:Bcl-2 inhibits the mitochondrial release of an apoptogenic protease. 887 5

A green fluorescent protein (GFP)-Raf-1 fusion protein was used to show that Bcl-2 can target this kinase to mitochondria. Active Raf-1 fused with targeting sequences from an outer mitochondrial membrane protein protected cells from apoptosis and resulted in phosphorylation of BAD, a proapoptotic Bcl-2 homolog. Plasma membrane-targeted Raf-1 did not protect from apoptosis and resulted in phosphorylation of ERK-1 and ERK-2. Untargeted active Raf-1 improved Bcl-2-mediated resistance to apoptosis, whereas a kinase-inactive Raf-1 mutant abrogated apoptosis suppression by Bcl-2. Bcl-2 can therefore target Raf-1 to mitochondrial membranes, allowing this kinase to phosphorylate BAD or possibly other protein substrates involved in apoptosis regulation.
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PMID:Bcl-2 targets the protein kinase Raf-1 to mitochondria. 892 27

Both physiological cell death (apoptosis) and at least some cases of accidental cell death (necrosis) involve a two-step-process. At first level, numerous physiological or pathological stimuli can trigger mitochondrial permeability transition which constitutes a rate-limiting event and initiates the common phase of the death process. Mitochondrial permeability transition (PT) involves the formation of proteaceous, regulated pores, probably by apposition of inner and outer mitochondrial membrane proteins which cooperate to form the mitochondrial PT pore complex. Inhibition of PT by pharmacological intervention on mitochondrial structures or mitochondrial expression of the apoptosis-inhibitory oncoprotein Bcl-2 thus can prevent cell death. At a second level, the consequences of mitochondrial dysfunction (collapse of the mitochondrial transmembrane potential, uncoupling of the respiratory chain, hyperproduction of superoxide anions, disruption of mitochondrial biogenesis, outflow of matrix calcium and glutathione, and release of soluble intermembrane proteins) can entail a biogenetic catastrophe culminating in the disruption of plasma membrane integrity (necrosis) and/or the activation and action of apoptogenic proteases with secondary endonuclease activation and consequent oligonucleosomal DNA fragmentation (apoptosis). The acquisition of the biochemical and ultrastructural features of apoptosis critically relies on the liberation of apoptogenic proteases or protease activators from the mitochondrial intermembrane space. This scenario applies to very different models of cell death. The notion that mitochondrial events control cell death has major implications for the development of death-inhibitory drugs.
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PMID:Mitochondrial implication in accidental and programmed cell death: apoptosis and necrosis. 923 43

Fas-driven apoptosis in Jurkat cells results in the inactivation of cytochrome c with cessation of oxygen consumption. Overexpression of Bcl-2 was found to protect against acidification and apoptosis mediated by Fas ligation in these cells. Bcl-2 is present in the outer mitochondrial membrane, but the molecular mechanism by which it protects cells is unknown. Because Bcl-2 projects into the mitochondrial intermembrane space and cytochrome c is located in the intermembrane space, we considered the possibility that Bcl-2 might protect cytochrome c from inactivation during Fas-mediated apoptosis. The present study shows that 1) in Jurkat cells, cytochrome c inactivation during Fas-driven apoptosis requires the permeabilization of the outer mitochondrial membrane; and 2) the post-mitochondrial fraction from CEM cells that overexpress Bcl-2 both prevents and reverses cytochrome c inactivation.
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PMID:Bcl-2 and the outer mitochondrial membrane in the inactivation of cytochrome c during Fas-mediated apoptosis. 926 20


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