Respiratory chain deficiency slows down cell-cycle progression via reduced ROS generation and is associated with a reduction of p21CIP1/WAF1.
We have used HeLa cells without mitochondrial DNA (rho0-cells) and transient rho0-phenocopies, obtained from wild-type cells by short-term treatment with ethidium bromide, to analyze how the absence of a functional mitochondrial respiratory chain slows down proliferation. We ruled out an energetic problem (ATP/ADP content) as well as defective synthesis of pyrimidine, iron-sulfur clusters or heme as important causes for the proliferative defect. Flow cytometric analysis revealed that reactive oxygen species were reduced in rho0-cells and in rho0-phenocopies, and that, quite unusually, all stages of the cell cycle were slowed down. Specific quenching of mitochondrial ROS with the ubiquinone analog MitoQ also resulted in slower growth. Some important cell-cycle regulators were reduced in rho0-cells: cyclin D3, cdk6, p18INK4C, p27KIP1, and p21CIP1/WAF1. In the rho0-phenocopies, the expression pattern did not fully duplicate the complex response observed in rho0-cells, and mainly p21CIP1/WAF1 was downregulated. Activities of the growth regulatory PKB/Akt and MAPK/ERK-signaling pathways did not correlate with proliferation rates of rho0-cells and rho0-phenocopies. Our study demonstrates that loss of a functional mitochondrial electron transport chain inhibits cell-cycle progression, and we postulate that this occurs through the decreased concentration of reactive oxygen species, leading to downregulation of p21CIP1/WAF1.
Schauen
Matthias
M
Institute of Vegetative Physiology, University of Köln, Köln, Germany. m.schauen@uni-koeln.de
Spitkovsky
Dimitry
D
Schubert
Jens
J
Fischer
Jürgen H
JH
Hayashi
Jun-ichi
J
Wiesner
Rudolf J
RJ
D000244:Adenosine Diphosphate / Q000378:metabolism; D000255:Adenosine Triphosphate / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000378:metabolism; D049108:Cell Enlargement; D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism*; D015536:Down-Regulation; D004996:Ethidium / Q000494:pharmacology; D048049:Extracellular Signal-Regulated MAP Kinases / Q000378:metabolism; D006367:HeLa Cells; D006418:Heme / Q000096:biosynthesis; D006801:Humans; D028361:Mitochondrial Diseases / Q000235:genetics / Q000378:metabolism*; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D017382:Reactive Oxygen Species / Q000378:metabolism*; D015398:Signal Transduction; D014529:Uridine / Q000494:pharmacology; D014544:Uridine Triphosphate / Q000378:metabolism
D018797:Cell Cycle Proteins; D050759:Cyclin-Dependent Kinase Inhibitor p21; D017382:Reactive Oxygen Species; D006418:Heme; D000244:Adenosine Diphosphate; D000255:Adenosine Triphosphate; D051057:Proto-Oncogene Proteins c-akt; D048049:Extracellular Signal-Regulated MAP Kinases; D004996:Ethidium; D014544:Uridine Triphosphate; D014529:Uridine