Epibolin: a protein of human plasma that supports epithelial cell movement.

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Abstract
Earlier studies suggested that there is a specific activity in mammalian serum and plasma that supports epidermal (epithelial) cell movement. This activity was shown to be nondialyzable and heat labile. Using standard biochemical procedures-i.e., ammonium sulfate fractionation, ion-exchange and gel filtration chromatography, isoelectric precipitation and preparative polyacrylamide gel electrophoresis a factor was purified from human plasma that supports epidermal cell movement. The factor travels as an apparent single band on disc gel electrophoresis and corresponds to a glycosylated single-chain protein of .apprx. 65,000 .+-. 3,000 daltons The purified fraction is necessary and sufficient for epithelial cell movement in 3 in vitro assays: spreading of dissociated epidermal cells, outgrowth of epithelial sheets from skin explants, and epiboly, epithelial sheet movement over a floating skin explant. The purified fraction is active at a concentration of 1-2 .mu.g/ml of growth medium. It is destroyed by trypsin and its activity is augmented > 10-fold by a 2nd, as yet unpurified, fraction of plasma. Apparently a single protein of plasma support epidermal cell movement and this protein may play an important role in wound closure. It was named epibolin, because it supports epiboly, the most biologically relevant of the assays.