The exit from G(0) into the cell cycle requires and is controlled by sarco(endo)plasmic reticulum Ca2+ pump.
The intracellular calcium pump sarco(endo)plasmic reticulum Ca2+ (SERCA) is responsible for the formation of the Ca2+ gradient across the endoplasmic reticulum membrane, and this gradient is used to generate the Ca2- signal during agonist-stimulated cell growth. In the present study, the role of SERCA in both cell cycle and growth control was investigated using cultured rat aortic endothelial cells (RAEC). Using a novel DNA transfection approach, cell lines were established that showed varying degree of SERCA activity through the down-regulation of the endogenous SERCA gene (B. F. Liu, X. Xu, R. Fridman, S. Muallem, and T. H. Kuo, J. Biol. Chem. 271, 1--9, 1996). Cell proliferation studies indicated that the lower SERCA expressing cells exhibited a slower growth pattern without altering the doubling time which was similar for both parental and transfected RAEC lines. G1 to S phase transition was prolonged with a smaller proportion of cells entering DNA synthesis as indicated by thymidine incorporation assay. Comparison of transfected cell lines indicated a tight coupling of SERCA activity and the length of the G1 period. Down-regulation of SERCA gene expression was accompanied by increased mRNA levels of p21 (WAF1/CIP1), a universal cell cycle inhibitor. The delay in G1 to S progression also coincided with the up-regulation of p53 mRNA and underphosphorylation of the retinoblastoma protein. This study suggests that Ca2+ metabolism in the agonist mobilizable pool controls the cell cycle through the regulation of genes operating in the critical G1 to S checkpoint.
Cheng
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Department of Pathology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA.
Liu
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BF
Yu
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Y
Diglio
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C
Kuo
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TH
D000818:Animals; D001011:Aorta / Q000378:metabolism / Q000648:ultrastructure; D001692:Biological Transport; D002118:Calcium / Q000378:metabolism*; D000252:Calcium-Transporting ATPases / Q000378:metabolism; D002478:Cells, Cultured; D004730:Endothelium, Vascular / Q000378:metabolism* / Q000648:ultrastructure; D051381:Rats; D016192:Resting Phase, Cell Cycle; D012519:Sarcoplasmic Reticulum / Q000378:metabolism; D015398:Signal Transduction
D000252:Calcium-Transporting ATPases; D002118:Calcium