title: Effect of Overproduction of Mitochondrial Uncoupling Protein 2 on Cos7 Cells: Induction of Senescent-like Morphology and Oncotic Cell Death.
abstract: The maintenance of mitochondrial membrane potential is essential for cell growth and survival. Mitochondrial uncoupling protein 2 plays the most important roles in uncoupling oxidative phosphorylation and decreasing mitochondrial O2- production by regulating the mitochondrial membrane potential. We propose that mouse UCP2 has two glycine-rich motifs, motif 1: EGIRGLWKG (170-178) and a known Walker A-like motif 2: EGPRAFYKG (264-272). These motifs seem to be important for the function of UCP2.
  
  
  
  We investigated the biological effects of overproduced-UCP2 and its physiological consequence in Cos7 cells.
  
  
  
  We introduced several amino acid changes in the motif 1. The expression vectors of the green fluorescent protein (GFP)-fused UCP2 and mutant UCP2 were constructed and expressed in Cos7 cells.
  
  
  
  The UCP2-GFP-expressed cells significantly down-regulated the mitochondrial membrane potentials and induced the enlarged cell shapes. Next we generated the stably UCP2-GFP-expressed Cos7 cells by selection with the antibiotic Genecitin (G418). Within the first few weeks following G418-selection, the stably UCP2-GFP-expressed cells could not divide well and gradually manifested the irregular and enlarged senescent-like cell morphology. The UCP2/K177E- or UCP2/G174L-expressed cells did not induce the enlarged cell shapes. Hence, UCP2/K177E and UCP2/G174L produced the functional incompetence of the glycine-rich motif 1. The senescent-like cells significantly decreased the mitochondrial membrane potentials and finally died nearly one month.
  
  
  
  Overproduction of UCP2 irreversibly reduces the mitochondrial membrane potentials and induces the senescent-like morphology and finally oncotic cell death in Cos7 cells. These changes seem to occur from the irreversible metabolic changes following total loss of cellular ATP.
authors: Department of Anatomy and Neurosciences, Nagoya University Graduate School of Medicine, 65 Tsurumai- Cho, Showa-Ku, Nagoya, Aichi 466-8550, Japan. knishio@med.nagoya-u.ac.jp.
authors: Koji
authors: K
authors: Nishio
authors: Qian
authors: Q
authors: Ma
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D019943:Amino Acid Substitution; D000818:Animals; D019556:COS Cells; D016923:Cell Death; D048430:Cell Shape; D016922:Cellular Senescence; D002522:Chlorocebus aethiops; D006801:Humans; D053078:Membrane Potential, Mitochondrial; D051379:Mice; D008928:Mitochondria / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D017382:Reactive Oxygen Species / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D014162:Transfection; D000071246:Uncoupling Protein 2 / Q000096:biosynthesis* / Q000737:chemistry / Q000235:genetics
chemical_list: D017382:Reactive Oxygen Species; D011993:Recombinant Fusion Proteins; C000604389:UCP2 protein, human; C000604390:Ucp2 protein, mouse; D000071246:Uncoupling Protein 2; D000255:Adenosine Triphosphate