Increasing Bioactivity of Flt3 Ligand by Fusing Two Identical Soluble Domains

Increasing
Bioactivity of Flt3 Ligand by Fusing Two Identical Soluble Domains

LU
Chang-Ming, YU Jian-Feng, HUANG Wei-Da1, ZHOU Xuan, ZHANG Wei-Yan, XI Hong,
ZHANG Xue-Guang*

(Biotechnology
Research Institute, Soochow University, Suzhou 215007, China)

Abstract
Flt3 ligand (FL) is a hematopoietic growth factor, initiating its in tracellular
signaling cascade by binding to counterpart receptor and driving receptor dimerization.
The native form of soluble FL in vivo is mainly monomeric. In this study,
we constructed a rFL-FL fusion protein cDNA by linking two copies of cDNA encoding
the soluble domain of FL in tandem and expressed it in Pichia pastoris.
On SDS-polyacrylamide gel electrophoresis, the rFL-FL fusion protein showed
a molecular weight of 43 kD, agreeing well with the predicted value. The 43
kD protein was further confirmed by Western blot using polyclonal rabbit anti-human
FL antibody. The rFL-FL fusion protein exhibited about 10-fold increment in
its activity on colony formation of bone marrow progenitor cells. RFL-FL fusion
protein also exerted more potent effect than monomeric FL on extending the survival
of starving Raji cells.