TY - JOUR
T1 - Coordinating Etk/Bmx activation and VEGF upregulation to promote cell survival and proliferation
AU - Chau, Cindy H.
AU - Chen, Kai Yun
AU - Deng, Hong Tao
AU - Kim, Kwang Jin
AU - Hosoya, Ken Ichi
AU - Terasaki, Tetsuya
AU - Shih, Hsiu Ming
AU - Ann, David K.
N1 - Funding Information:
We thank Drs Rizwan Masood, Parkash Gill, Yun Qiu and Gary Bokoch for useful reagents and Dr Wei-Chiang Shen for helpful suggestions on the Matrigel assay. This work was supported in part by National Institute of Health Research grants R01 DE 10742 and R01 DE 14183 (to DK Ann), R01 HL 38658 and R01 HL 64365 (to K-J Kim), and Predoctoral Fellowship DE 07211 (to CH Chau).
PY - 2002/12/12
Y1 - 2002/12/12
N2 - Etk/Bmx, a member of the Tec family of non-receptor tyrosine kinase, is characterized by an N-terminal PH domain and has recently been shown to be involved in the regulation of various cellular processes, including proliferation, differentiation, motility and apoptosis. Since VEGF and the activation of its signaling pathway have been implicated in modulating a variety of biological responses, we characterized the role of Etk-dependent signaling pathways involved in the upregulation of VEGF expression, and explored the functional implications of this enhancement in sustaining cell proliferation and survival. Using Northern and Western analyses, transient transfections, and pharmacological agents, we demonstrate that Etk activation alone is sufficient to transcriptionally induce VEGF expression, independent of the previously identified hypoxia response element (HRE), in both Pa-4 epithelial and TR-BBB endothelial cells under normoxia. In addition, Etk utilizes both MEK/ERK and PI3-K/Pak1 signaling pathways in concert to activate VEGF transcription. Functionally, Etk activation elicits a profound stimulatory effect on TR-BBB cell proliferation and formation of capillary-like networks in Matrigel containing reduced levels of growth factors. Finally, antisense oligonucleotides against either endogenous VEGF or Etk abrogate the proliferation of Etk-activated TR-BBB cells, and exogenous VEGF treatment stimulates endogenous Etk tyrosine phosphorylation in HUVECs. Taken together, these results indicate that VEGF is both an Etk downstream target gene and an Etk upstream activator, constituting a reciprocal Etk-VEGF autoregulatory loop. These findings, to our knowledge, are the first delineation of a network of positive feedforward signaling pathways that converge on the Etk-VEGF axis, causally associating Etk-mediation of VEGF induction with enhanced cellular processes in both epithelial and endothelial cells.
AB - Etk/Bmx, a member of the Tec family of non-receptor tyrosine kinase, is characterized by an N-terminal PH domain and has recently been shown to be involved in the regulation of various cellular processes, including proliferation, differentiation, motility and apoptosis. Since VEGF and the activation of its signaling pathway have been implicated in modulating a variety of biological responses, we characterized the role of Etk-dependent signaling pathways involved in the upregulation of VEGF expression, and explored the functional implications of this enhancement in sustaining cell proliferation and survival. Using Northern and Western analyses, transient transfections, and pharmacological agents, we demonstrate that Etk activation alone is sufficient to transcriptionally induce VEGF expression, independent of the previously identified hypoxia response element (HRE), in both Pa-4 epithelial and TR-BBB endothelial cells under normoxia. In addition, Etk utilizes both MEK/ERK and PI3-K/Pak1 signaling pathways in concert to activate VEGF transcription. Functionally, Etk activation elicits a profound stimulatory effect on TR-BBB cell proliferation and formation of capillary-like networks in Matrigel containing reduced levels of growth factors. Finally, antisense oligonucleotides against either endogenous VEGF or Etk abrogate the proliferation of Etk-activated TR-BBB cells, and exogenous VEGF treatment stimulates endogenous Etk tyrosine phosphorylation in HUVECs. Taken together, these results indicate that VEGF is both an Etk downstream target gene and an Etk upstream activator, constituting a reciprocal Etk-VEGF autoregulatory loop. These findings, to our knowledge, are the first delineation of a network of positive feedforward signaling pathways that converge on the Etk-VEGF axis, causally associating Etk-mediation of VEGF induction with enhanced cellular processes in both epithelial and endothelial cells.
KW - Autocrine
KW - Etk
KW - Proliferation
KW - Survival
KW - VEGF
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U2 - 10.1038/sj.onc.1206032
DO - 10.1038/sj.onc.1206032
M3 - Article
C2 - 12483534
AN - SCOPUS:0037069931
VL - 21
SP - 8817
EP - 8829
JO - Oncogene
JF - Oncogene
SN - 0950-9232
IS - 57
ER -