Response gene to complement 32 is required for C5b-9 induced cell cycle activation in endothelial cells.
Proliferation of vascular endothelial cells (EC) and smooth muscle cells (SMC) is a critical event in angiogenesis and atherosclerosis. We previously showed that the C5b-9 assembly during complement activation induces cell cycle in human aortic EC (AEC) and SMC. C5b-9 can induce the expression of Response Gene to Complement (RGC)-32 and over expression of this gene leads to cell cycle activation. Therefore, the present study was carried out to test the requirement of endogenous RGC-32 for the cell cycle activation induced by C5b-9 by knocking-down its expression using siRNA. We identified two RGC-32 siRNAs that can markedly reduce the expression of RGC-32 mRNA in AEC. RGC-32 silencing in these cells abolished DNA synthesis induced by C5b-9 and serum growth factors, indicating the requirement of RGC-32 activity for S-phase entry. RGC-32 siRNA knockdown also significantly reduced the C5b-9 induced CDC2 activation and Akt phosphorylation. CDC2 does not play a role in G1/S transition in HeLa cells stably overexpressing RGC-32. RGC-32 was found to physically associate with Akt and was phosphorylated by Akt in vitro. Mutation of RGC-32 protein at Ser 45 and Ser 47 prevented Akt mediated phosphorylation. In addition, RGC-32 was found to regulate the release of growth factors from AEC. All these data together suggest that cell cycle induction by C5b-9 in AEC is RGC-32 dependent and this is in part through regulation of Akt and growth factor release.
Fosbrink
Matthew
M
Department of Neurology, University of Maryland, School of Medicine, Baltimore, MD 21201, USA.
Cudrici
Cornelia
C
Tegla
Cosmin A
CA
Soloviova
Kateryna
K
Ito
Takahiro
T
Vlaicu
Sonia
S
Rus
Violeta
V
Niculescu
Florin
F
Rus
Horea
H
D000328:Adult; D043925:Angiogenesis Inducing Agents / Q000378:metabolism; D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle / Q000187:drug effects*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D015938:Complement Membrane Attack Complex / Q000494:pharmacology*; D050760:Cyclin-Dependent Kinase Inhibitor p27 / Q000378:metabolism; D042783:Endothelial Cells / Q000166:cytology* / Q000187:drug effects* / Q000201:enzymology; D004789:Enzyme Activation / Q000187:drug effects; D006367:HeLa Cells; D006801:Humans; D008565:Membrane Proteins / Q000378:metabolism; D009124:Muscle Proteins / Q000235:genetics / Q000378:metabolism*; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation / Q000187:drug effects; D011485:Protein Binding / Q000187:drug effects; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism
D043925:Angiogenesis Inducing Agents; C103706:CDC6 protein, human; D018797:Cell Cycle Proteins; D015938:Complement Membrane Attack Complex; D008565:Membrane Proteins; D009124:Muscle Proteins; D009419:Nerve Tissue Proteins; D009687:Nuclear Proteins; C098069:PIGF protein, human; C115049:RGCC protein, human; D050760:Cyclin-Dependent Kinase Inhibitor p27; D051057:Proto-Oncogene Proteins c-akt; D016203:CDC2 Protein Kinase