Isolation and characterization of possible target proteins responsible for neurite outgrowth induced by a tripeptide aldehyde in PC12H cells.

A tripeptide protease inhibitor, benzyloxycarbonyl-Leu-Leu-Leu-aldehyde (ZLLLal), induces the outgrowth of one or two long neurites from PC12 cells. Since this neurite outgrowth is different from that induced by nerve growth factor (NGF) in some aspects, the existence of a molecule that regulates neurite formation in PC12 cells was expected. To identify a target molecule, Leu-Leu-Leu-aldehyde (LLLal) was immobilized as a ligand for affinity chromatography. Proteins of 33-kDa, 35-kDa, and 180-kDa from the membrane and cytoplasmic fractions of PC12 cells bound specifically to the affinity column. ZLLL-COOH has no ability to induce neurite outgrowth, and the 33-kDa, 35-kDa, and 180-kDa proteins do not bind to an LLL-COOH coupled affinity column. By using the LLLal-affinity column, the 33-kDa/35-kDa proteins were found to be converted to 36-kDa/38-kDa proteins during brain development in rats. These results suggest that LLLal-binding proteins are involved in neuronal differentiation.