Midkine

Midkine (MK, MDK), or Neurite Growth-promoting Factor 2, is a basic heparin-binding growth factor of low molecular weight, a member of the NEGF family founded by Pleiotrophin (NEGF1, 46% homologous with MK). It is a nonglycosylated protein, composed of two domains held by disulfide bridges. It is a developmentaly important retinoic acid-responsive gene product strongly induced during mid-gestation, hence the name midkine. Restricted mainly to certain tissues in the normal adult, it is strongly induced during oncogenesis, inflammation and tissue repair.

MK is pleiotropic, capable of exerting activities such as cell proliferation, cell migration, angiogenesis and fibrinolysis. A molecular complex containing receptor-type tyrosine phosphatase zeta (PTPζ), low density lipoprotein receptor-related protein (LRP), anaplastic leukemia kinase (ALK) and syndecans is considered to be its receptor.