Transforming Growth Factor 1 Down-regulates Vascular Endothelial Growth Factor Receptor 2/flk-1 Expression in Vascular Endothelial Cells

doi:10.1074/jbc.271.19.11500

Transforming Growth Factor 1 Down-regulates Vascular Endothelial Growth Factor Receptor 2/flk-1 Expression in Vascular Endothelial Cells (*)

From the Department of Morphology and
Division of Oncology, University Medical Center, 1211 Geneva 4, Switzerland

^§ To whom correspondence should be addressed:
Dept. of Morphology, University Medical Center, 1, rue Michel Servet, 1211 Geneva 4, Switzerland.
Tel.: 0041-22-702-5291; Fax: 0041-22-347-3334. pepper{at}cmu.unige.ch.

Abstract

Although the importance of the vascular endothelial growth factor (VEGF)/VEGF tyrosine kinase receptor (VEGFR) system in angiogenesis is well established, very little is known about the regulation of VEGFR expression in vascular endothelial cells. We have cloned partial cDNAs encoding bovine VEGFR-1 (flt) and -2 (flk-1) and used them to study VEGFR expression by bovine microvascular- and large vessel-derived endothelial cells. Both cell lines express flk-1, but not flt. Transforming growth factor β1 (TGF-β1) reduced the high affinity I-VEGF binding capacity of both cell types in a dose-dependent manner, with a 2.0-2.7-fold decrease at 1-10 ng/ml. Cross-linking experiments revealed a decrease in I-VEGF binding to a cell surface monomeric protein corresponding to Flk-1 on the basis of its affinity for VEGF, molecular mass (185-190 kDa), and apparent internalization after VEGF binding. Immunoprecipitation and Western blot experiments demonstrated a decrease in Flk-1 protein expression, and TGF-β1 reduced flk-1 mRNA levels in a dose-dependent manner. These results imply that TGF-β1 is a major regulator of the VEGF/Flk-1 signal transduction pathway in endothelial cells.

Footnotes

↵* This work was supported by Swiss National Science Foundation Grants 3100-043364.95 and 32-39212.93. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore by hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.

The nucleotide sequence(s) reported in this paper has been submitted to the GenBank(™)/EMBL Data Bank with accession number(s) X94298 (bflk-1) and X94263 (bflt).
↵¹ The abbreviations used are:

VEGF

vascular endothelial growth factor

VEGFR

VEGF receptor

TGF-β1

transforming growth factor β1

RT-PCR

reverse transcription-polymerase chain reaction

bp

base pair(s)

BME

bovine microvascular endothelial

BAE

bovine aortic endothelial

DSS

dissuccinimidyl suberate

PVDF

polyvinylidene difluoride

PA

plasminogen activator.
- Received February 26, 1996.