Partial purification and characterization of a neurite outgrowth-promoting factor from chick heart-cell conditioned medium.

A factor in heart-cell conditioned medium (HCM), which adsorbs to the polyornithine-coated culture substratum, is known to induce neurite outgrowth from neurons in culture. This factor - termed the substrate conditioning factor (SCF) - was purified from chick HCM by fractionation with ammonium sulfate, DEAE Sepharose, and hydroxylapatite. A quantitative bioassay with dorsal root ganglion neurons in dissociated cell culture was used to determine the neurite outgrowth-promoting activity. More than 10,000-fold purification was achieved in the specific activity. SCF was sensitive to trypsin, and bound to the wheat germ lectin affinity column, indicating that SCF is a glycoprotein. The most purified fraction produced two major bands with apparent molecular weights of 360K and 220-240K on SDS-gel electrophoresis under reducing conditions. They were detected as radioactive bands when polypeptides synthesized by heart cells were metabolically labeled with [35S]methionine. These results suggest that the 360K and 220-240K components are required for the neurite outgrowth-promoting activity of SCF.