Muramatsu H, Shirahama H, Yonezawa S, Maruta H, Muramatsu T
Department of Biochemistry, Faculty of Medicine, Kagoshima University, Japan.
Dev Biol. 1993 Oct;159(2):392-402. doi: 10.1006/dbio.1993.1250.
Midkine (MK) is a heparin-binding growth factor specified by a retinoic acid responsive gene. A rabbit was immunized against recombinant MK produced in L cells, and the resulting antibody was affinity purified using MK-glutathione S-transferase fusion protein as a ligand. The MK-specific antibody was used to investigate the function and distribution of MK. MK of the same size as the recombinant MK produced in L cells (13 kDa) was strongly detected in a 13-day rat embryo. Weak expression was observed in the brains of a 19-day embryo, neonates, and adults. In the 13-day mouse embryos, high levels of MK were detected on the surfaces of brain cells, as well as in basement membranes and in the epithelial cells of the intestine, the jaw, and the rib. Nerve cells from the brains of 13-day or 19-day rat embryos extended neurites about twofold more efficiently on MK-coated dishes than on poly-L-lysine-coated dishes. Furthermore, anti-MK antibody inhibited neurite extension not only on MK-coated dishes, but also on poly-L-lysine-coated dishes. These results suggest that MK is an endogenous neurite outgrowth factor involved in the development of the central nervous system. Anti-MK antibody was also found to inhibit growth of Wilms' tumor cells, which secreted MK into culture medium. Thus, overproduction of MK is involved in enhanced growth of Wilms' tumor cells.
中期因子（MK）是一种由视黄酸反应基因所确定的肝素结合生长因子。用在L细胞中产生的重组MK对一只兔子进行免疫，并用MK-谷胱甘肽S-转移酶融合蛋白作为配体对所得抗体进行亲和纯化。用MK特异性抗体来研究MK的功能和分布。在13日龄大鼠胚胎中强烈检测到与在L细胞中产生的重组MK大小相同（13 kDa）的MK。在19日龄胚胎、新生儿和成年动物的大脑中观察到弱表达。在13日龄小鼠胚胎中，在脑细胞表面以及基底膜和肠道、颌骨及肋骨的上皮细胞中检测到高水平的MK。来自13日龄或19日龄大鼠胚胎大脑的神经细胞在MK包被的培养皿上比在聚-L-赖氨酸包被的培养皿上更有效地延伸神经突约两倍。此外，抗MK抗体不仅抑制在MK包被培养皿上的神经突延伸，也抑制在聚-L-赖氨酸包被培养皿上的神经突延伸。这些结果表明，MK是一种参与中枢神经系统发育的内源性神经突生长因子。还发现抗MK抗体抑制威尔姆斯瘤细胞的生长，威尔姆斯瘤细胞将MK分泌到培养基中。因此，MK的过量产生与威尔姆斯瘤细胞的生长增强有关。
