生长/分化因子MK家族的生物学作用的研究进展

孕中期肾蛋白（Ｍｉｄｋｉｎｅ，ＭＫ）和多效生长因子（Ｐｌｅｉｏｔｒｏｐｈｉｎ，ＰＴＮ）组成一种新的肝素结合生长／分化因子家族。它们都是分泌性单肽链蛋白，蛋白质结构都类似。ＭＫ和ＰＴＮ基因均可在胚胎发育期在多种组织大量表达，而仅ＰＴＮ在出生后，有一种神经系统的短暂表达高峰，两者不同地见于数种成年期组织。这些发现结合体外实验结果，提示它们在发育上有重要的促生长／分化作用，并具有神经营养活性，在成年期也有某些未知的生理功能。其中，尤以对神经系统的发育和维持最为重要。它们还可促进血管内皮细胞的纤溶活性，并可能作为肿瘤生长因子在某些肿瘤的发生中起作用

RESEARCH PROGRESS IN THE BIOLOGICAL ROLES OF THE MIDKINE FAMILY OF GROWTH/DIFFERENTIATION FACTORS

Midkine (MK) and pleiotrophin(PTN) constitute a new family of heparin binding growth/defferentiation factors.They are secreted proteins of a single polypeptide and are similar in protein and gene structures.Both MK and PTN gene are strongly expressed in a wide variaty of animal tissues during embryogenesis,but only PTN gene shows a transient postnatal peak of expression in the nervous system.They are differently found in several specific tissues in adult period.These findings suggest,together with the results of in vitro experiments,that they play important growth/differentiation roles in development,are neurotrophic,and have some unknown physiological functions in adult period,in which those in the development and maintenance of the nervous system are the most important.They can enhance the fibrinolytic activity of vascular endothelial cells and may also act as tumor growth factors in the progression of some tumors.