AJP - Cell Physiology, Vol 263, Issue 3 C551-C562, Copyright © 1992 by American Physiological Society
Fetuin: its enigmatic property of growth promotion
Z. Nie
Department of Cellular and Molecular Physiology, Harvard Medical School, Boston, Massachusetts 02115.
A variety of cell types in culture respond to fetuin, a glycoprotein from
fetal bovine serum, which is often an important supplement to many
serum-free media. Bovine fetuin preparation has been shown to inhibit
trypsin activity and promote cellular attachment, growth, and
differentiation in many different culture systems. In addition, fetuin
associates with various growth factors or growth-promoting substances.
However, whether the growth-promoting activity of fetuin preparation is due
to fetuin per se or to its minor contaminant(s) has been a long-standing
puzzle. The present review surveys the literature concerning this enigmatic
property of fetuin and summarizes three possibilities: 1) fetuin itself is
active, although the majority of studies do not support this; 2) various
contaminants of fetuin preparations, including potentially unidentified
ones, are responsible for the activity, a possibility supported by numerous
reports; and 3) one of the fetuin subspecies, one of its contaminants, or a
combination of both of these is responsible for growth of a specific cell
type. In addition, the basic physicochemical properties and other
biological functions of fetuin have also been presented.
