EGF regulates plasminogen activator inhibitor-1 (PAI-1) by a pathway involving c-Src, PKCdelta, and sphingosine kinase 1 in glioblastoma cells.
Patients with gliomas expressing high levels of epidermal growth factor receptor (EGFR) and plasminogen activator inhibitor-1 (PAI-1) have a shorter overall survival prognosis. Moreover, EGF enhances PAI-1 expression in glioma cells. Although multiple known signaling cascades are activated by EGF in glioma cells, we show for the first time that EGF enhances expression of PAI-1 via sequential activation of c-Src, protein kinase C delta (PKCdelta), and sphingosine kinase 1 (SphK1), the enzyme that produces sphingosine-1-phosphate. EGF induced rapid phosphorylation of c-Src and PKCdelta and concomitant translocation of PKCdelta as well as SphK1 to the plasma membrane. Down-regulation of PKCdelta abolished EGF-induced SphK1 translocation and up-regulation of PAI-1 by EGF; whereas, down-regulation of PKCalpha had no effect on the EGF-induced PAI-1 activation but enhanced its basal expression. Similarly, inhibition of c-Src activity by PP2 blocked both EGF-induced translocation of SphK1 and PKCdelta to the plasma membrane and up-regulation of PAI-1 expression. Furthermore, SphK1 was indispensable for both EGF-induced c-Jun phosphorylation and PAI-1 expression. Collectively, our results provide a functional link between three critical downstream targets of EGF, c-Src, PKCdelta, and SphK1 that have all been implicated in regulating motility and invasion of glioma cells.
Paugh
Barbara S
BS
Department of Biochemistry and Molecular Biology, Virginia Commonwealth University School of Medicine/Massey Cancer Center, Richmond, VA 23298, USA.
Paugh
Steven W
SW
Bryan
Lauren
L
Kapitonov
Dmitri
D
Wilczynska
Katarzyna M
KM
Gopalan
Sunita M
SM
Rokita
Hanna
H
Milstien
Sheldon
S
Spiegel
Sarah
S
Kordula
Tomasz
T
D045744:Cell Line, Tumor; D004815:Epidermal Growth Factor / Q000494:pharmacology*; D005786:Gene Expression Regulation / Q000187:drug effects / Q000235:genetics; D005909:Glioblastoma / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D016328:NF-kappa B / Q000378:metabolism; D017853:Phosphotransferases (Alcohol Group Acceptor) / Q000378:metabolism*; D017395:Plasminogen Activator Inhibitor 1 / Q000235:genetics / Q000378:metabolism*; D051571:Protein Kinase C-alpha / Q000235:genetics / Q000378:metabolism; D051745:Protein Kinase C-delta / Q000235:genetics / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000378:metabolism*; D050791:STAT Transcription Factors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects*; D018808:Transcription Factor AP-1 / Q000378:metabolism; D000099157:Sphingosine Kinase
D004815:Epidermal Growth Factor; D016328:NF-kappa B; D017853:Phosphotransferases (Alcohol Group Acceptor); D017395:Plasminogen Activator Inhibitor 1; D051571:Protein Kinase C-alpha; D051745:Protein Kinase C-delta; D016392:Proto-Oncogene Proteins pp60(c-src); D050791:STAT Transcription Factors; D018808:Transcription Factor AP-1; D000099157:Sphingosine Kinase