Blog
About

12
views
0
recommends
+1 Recommend
0 collections
    0
    shares
      • Record: found
      • Abstract: found
      • Article: not found

      The E1B 19K/Bcl-2–binding Protein Nip3 is a Dimeric Mitochondrial Protein that Activates Apoptosis

      Read this article at

      ScienceOpenPMC
      Bookmark
          There is no author summary for this article yet. Authors can add summaries to their articles on ScienceOpen to make them more accessible to a non-specialist audience.

          Abstract

          Nip3 (nineteen kD interacting protein-3) is an E1B 19K and Bcl-2 binding protein of unknown function. Nip3 is detected as both a 60- and 30-kD protein in vivo and in vitro and exhibits strong homologous interaction in a yeast two-hybrid system indicating that it can homodimerize. Nip3 is expressed in mitochondria and a mutant (Nip3 163) lacking the putative transmembrane domain and COOH terminus does not dimerize or localize to mitochondria. Transient transfection of epitope-tagged Nip3 in Rat-1 fibroblasts and MCF-7 breast carcinoma induces apoptosis within 12 h while cells transfected with the Nip3 163 mutant have a normal phenotype, suggesting that mitochondrial localization is necessary for induction of cell death. Nip3 overexpression increases the sensitivity to apoptosis induced by granzyme B and topoisomerase I and II inhibitors. After transfection, both Nip3 and Nip3 163 protein levels decrease steadily over 48 h indicating that the protein is rapidly degraded and this occurs in the absence of cell death. Bcl-2 overexpression initially delays the onset of apoptosis induced by Nip3 but the resistance is completely overcome in longer periods of incubation. Nip3 protein levels are much higher and persist longer in Bcl-2 expressing cells. In conclusion, Nip3 is an apoptosis-inducing dimeric mitochondrial protein that can overcome Bcl-2 suppression.

          Related collections

          Most cited references 38

          • Record: found
          • Abstract: found
          • Article: not found

          Prevention of apoptosis by Bcl-2: release of cytochrome c from mitochondria blocked.

          Bcl-2 is an integral membrane protein located mainly on the outer membrane of mitochondria. Overexpression of Bcl-2 prevents cells from undergoing apoptosis in response to a variety of stimuli. Cytosolic cytochrome c is necessary for the initiation of the apoptotic program, suggesting a possible connection between Bcl-2 and cytochrome c, which is normally located in the mitochondrial intermembrane space. Cells undergoing apoptosis were found to have an elevation of cytochrome c in the cytosol and a corresponding decrease in the mitochondria. Overexpression of Bcl-2 prevented the efflux of cytochrome c from the mitochondria and the initiation of apoptosis. Thus, one possible role of Bcl-2 in prevention of apoptosis is to block cytochrome c release from mitochondria.
            Bookmark
            • Record: found
            • Abstract: found
            • Article: not found

            Induction of apoptotic program in cell-free extracts: requirement for dATP and cytochrome c.

            A cell-free system based on cytosols of normally growing cells is established that reproduces aspects of the apoptotic program in vitro. The apoptotic program is initiated by addition of dATP. Fractionation of cytosol yielded a 15 kDa protein that is required for in vitro apoptosis. The absorption spectrum and protein sequence revealed that this protein is cytochrome c. Elimination of cytochrome c from cytosol by immunodepletion, or inclusion of sucrose to stabilize mitochondria during cytosol preparation, diminished the apoptotic activity. Adding back cytochrome c to the cytochrome c-depleted extracts restored their apoptotic activity. Cells undergoing apoptosis in vivo showed increased release of cytochrome c to their cytosol, suggesting that mitochondria may function in apoptosis by releasing cytochrome c.
              Bookmark
              • Record: found
              • Abstract: found
              • Article: not found

              The release of cytochrome c from mitochondria: a primary site for Bcl-2 regulation of apoptosis.

              In a cell-free apoptosis system, mitochondria spontaneously released cytochrome c, which activated DEVD-specific caspases, leading to fodrin cleavage and apoptotic nuclear morphology. Bcl-2 acted in situ on mitochondria to prevent the release of cytochrome c and thus caspase activation. During apoptosis in intact cells, cytochrome c translocation was similarly blocked by Bcl-2 but not by a caspase inhibitor, zVAD-fmk. In vitro, exogenous cytochrome c bypassed the inhibitory effect of Bcl-2. Cytochrome c release was unaccompanied by changes in mitochondrial membrane potential. Thus, Bcl-2 acts to inhibit cytochrome c translocation, thereby blocking caspase activation and the apoptotic process.
                Bookmark

                Author and article information

                Journal
                J Exp Med
                The Journal of Experimental Medicine
                The Rockefeller University Press
                0022-1007
                1540-9538
                15 December 1997
                : 186
                : 12
                : 1975-1983
                Affiliations
                From the [* ]Manitoba Institute of Cell Biology and the [§ ]Department of Human Genetics, University of Manitoba, Winnipeg, Manitoba, Canada; and the []Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada
                Author notes

                Address correspondence to Arnold H. Greenberg, Manitoba Institute of Cell Biology, University of Manitoba, 100 Olivia St., Winnipeg, MB Canada R3E OV9. Phone (204) 787-2112; Fax: (204) 787-2190; E-mail: agreenb@ 123456cc.umanitoba.ca

                Article
                2199165
                9396766
                Categories
                Article

                Medicine

                Comments

                Comment on this article