In situ photoaffinity labeling of the target protein for lembehyne A, a neuronal differentiation inducer.

A C(36) linear acetylene alcohol, lembehyne A (LB-A), induces neuronal differentiation against neuroblastoma cells morphologically and also functionally. The differentiation and cytostatic effect induced by LB-A was specific to neuroblastoma, Neuro 2A cells. To identify the target protein for LB-A, a radioactive photoaffinity probe, [(125)I]18-(2'-azido-5'-iodo-benzoyloxy)-LB-18 ([(125)I]azido-LB-18), was synthesized. As a result of in situ labeling experiments against Neuro 2A cells, a protein of M(r) 30 kDa was photolabeled specifically. This labeling was inhibited in the presence of LB-A or the active analogs of LB-A, whereas the inactive analogs showed no inhibitory effect on this labeling. These results suggest that this protein of M(r) 30 kDa is the target protein for LB-A and may play an important role for the neuronal differentiation in neuroblastoma, Neuro 2A cells.