Effect of N-terminal Deletion on Biological Activity of Vascular Endothelial Cell Growth Inhibitor

( Department of
Microbiology, Second Military Medical University, Shanghai 200433, China )

Abstract
Vascular endothelial cell growth inhibitor (VEGI) is
a novel cytokine which belongs to the TNF superfamily. It can inhibit the
proliferation of endothelial cells and neovascularization. However, little
is known about the structure-function relationship of VEGI. In order to study
the effect of the N-terminus of VEGI on biological properties, the sequence
alignment among VEGI and TNF superfamily members based on structure knowledge
was done, and then two truncated forms of VEGI were constructed, in which
43 and 51 amino acids from N-terminus were deleted and named VEGI131
and VEGI123. Recombinant proteins were generated from E. coli. The expression rates were 25.2% (VEGI131) and 27.8%
(VEGI123) of total bacterial proteins. After purification the purity
reached 92.5% (VEGI131) and 91.6% (VEGI123). VEGI131
showed significant inhibitory effect on growth of human umbilical vein endothelial
cells (HUVEC), IC50 of VEGI131 being 35 mg/L. Under
the same conditions, IC50 of VEGI151 (the wild type
of VEGI) was 27 mg/L, but VEGI123 showed no inhibitory effect.
On chick choriallantic membrane (CAM) assay, VEGI151 markedly reduced
the number of main vessels, and VEGI131 decreased capillary number,
while the effect of VEGI123 was almost the same as control. These
results suggest that the first 43 amino acids from N-terminus of VEGI have
no significant effect on biological activity, but the amino acids 44-51 at
N-terminus are required for full biological activity.