Signaling mechanism of extracellular RNA in endothelial cells.
Extracellular RNA has been shown to induce vascular endothelial growth factor (VEGF)-dependent hyperpermeability in vivo as well as in vitro. Studies were performed to investigate the mechanism of these effects. For permeability studies primary cultures of porcine brain-derived microvascular endothelial cells (BMECs) and for all other analytical studies the human brain endothelial cell line HCMEC/D3 or human umbilical vein endothelial cells (HUVECs) were used. RNA, but not DNA, initiated signaling events by binding of VEGF to neuropilin-1, followed by VEGF-R2 phosphorylation, activation of phospholipase C (PLC), and intracellular release of Ca(2+). Activation of these pathways by RNA also resulted in the release of von Willebrand Factor from Weibel-Palade bodies. Pretreatment of cells with heparinase totally abrogated the RNA-induced permeability changes, whereas RNA together with VEGF completely restored VEGF-R2-mediated hyperpermeability. Although poly:IC increased the interleukin-6 release via activation of toll-like receptor-3 (TLR-3), permeability changes mediated by poly:IC or RNA remained unchanged after blocking TLR-3 or NF-kB activation. These results indicate that extracellular RNA serves an important cofactor function to engage VEGF for VEGF-R2-dependent signal transduction, reminiscent of the coreceptor mechanism mediated by proteoglycans, which might be of relevance for the mobilization and cellular activities of RNA-binding cytokines in general.
Fischer
Silvia
S
Department of Biochemistry, Medical School Justus-Liebig-Universität, Friedrichstrasse 24, D-35392 Giessen, Germany.
Nishio
Miwako
M
Peters
Saskia C
SC
Tschernatsch
Marlene
M
Walberer
Maureen
M
Weidemann
Susanne
S
Heidenreich
Regina
R
Couraud
Pierre O
PO
Weksler
Babette B
BB
Romero
Ignacio A
IA
Gerriets
Tibo
T
Preissner
Klaus T
KT
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002199:Capillary Permeability; D002478:Cells, Cultured; D042783:Endothelial Cells / Q000378:metabolism*; D004730:Endothelium, Vascular / Q000166:cytology*; D006801:Humans; D039942:Neuropilin-1 / Q000378:metabolism; D011485:Protein Binding; D012313:RNA / Q000494:pharmacology*; D015398:Signal Transduction; D013552:Swine; D010738:Type C Phospholipases / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000378:metabolism*; D040301:Vascular Endothelial Growth Factor Receptor-2 / Q000378:metabolism*
D042461:Vascular Endothelial Growth Factor A; D039942:Neuropilin-1; D012313:RNA; D040301:Vascular Endothelial Growth Factor Receptor-2; D010738:Type C Phospholipases; D002118:Calcium