Isolation of sympathonectin; a substrate-bound protein which induces preferential growth of sympathetic fibers in vitro.

A protein named 'sympathonectin', was purified from chick heart cell-conditioned medium (HCM), on the basis of its ability to direct the neurite outgrowth of cultured sympathetic neurons. The most purified fraction showed a doublet band on SDS-PAGE with an apparent molecular weight of 370 kDa. The biological activity of sympathonectin was over 100 times higher than that of laminin. Immunoblotting with anti-sympathonectin of the 100,000 x g pellet (particulate) fraction of HCM identified a distinct 370 kDa band; this molecule did not react to the anti-laminin serum. The immunohistochemical analysis showed that the antibody against sympathonectin stained heart tissue but not skeletal muscle tissue, whereas anti-laminin serum stained both tissues. These results suggest that sympathonectin may play a role during sympathetic innervation of target organs.