Phosphatidylinositol 3-kinase and calcium-activated transcription pathways are required for VLDL-induced smooth muscle cell proliferation.
Little is known regarding the molecular mechanisms of atherogenicity of triglyceride-rich lipoproteins such as very low-density lipoproteins (VLDLs). We examined the effect of VLDL on proliferation of rat aortic smooth muscle cells, intracellular Ca2+ handling, and activity of cAMP-responsive element binding protein (CREB) and nuclear factor of activated T cells (NFAT) transcription factors. VLDL, isolated from human serum, dose- and time-dependently promoted proliferation. After 4 hours of exposure to VLDL (0.15 g/L proteins), the caffeine-induced Ca2+ release was inhibited and the IP3-sensitive Ca2+ release induced by ATP (10 micromol/L) was markedly prolonged. In quiescent cells, CREB was phosphorylated (pCREB) and NFAT was present in the cytosol, whereas in cells exposed to VLDL for 4 to 24 hours, pCREB disappeared and NFAT was translocated to the nucleus. VLDL-induced NFAT translocation and proliferation were blocked by cyclosporin A and LY294002 involving calcineurin and phosphatidylinositol 3-kinase (PI3K) pathways. Indeed, VLDLs rapidly phosphorylate protein kinase B and glycogen synthase kinase-3beta in a PI3K-dependent way. These results provide the first evidence that VLDLs induce smooth muscle cell proliferation by activating the PI3K pathway and nuclear NFAT translocation. Blockade of the Ca2+-induced Ca2+ release mechanism and dephosphorylation of pCREB contribute but were not sufficient to induce a proliferating phenotype.
INSERM U446/IFR-75, Institut de signalisation et innovation thérapeutique, Faculté de Pharmacie, Tour D4, 5 rue JB Clément, 92296 Châtenay-Malabry, France.
Larissa
L
Lipskaia
Marie-Luce
ML
Pourci
Claudine
C
Deloménie
Laurent
L
Combettes
Dominique
D
Goudounèche
Jean-Louis
JL
Paul
Thierry
T
Capiod
Anne-Marie
AM
Lompré
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D000818:Animals; D019703:Calcineurin / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D020013:Calcium Signaling / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006801:Humans; D007424:Intracellular Fluid / Q000378:metabolism; D008079:Lipoproteins, VLDL / Q000494:pharmacology*; D008297:Male; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D000081082:Phosphoinositide-3 Kinase Inhibitors; D010766:Phosphorylation / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D014157:Transcription Factors / Q000378:metabolism; D014158:Transcription, Genetic / Q000502:physiology*
D019703:Calcineurin; D002118:Calcium; D017362:Cyclic AMP Response Element-Binding Protein; D004268:DNA-Binding Proteins; D004791:Enzyme Inhibitors; D008079:Lipoproteins, VLDL; D050778:NFATC Transcription Factors; D009687:Nuclear Proteins; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D014157:Transcription Factors