Vol. 56, Issue 1, 185-195, July 1999

The Staurosporine-Like Compound L-753,000 (NB-506) Potentiates the Neurotrophic Effects of Neurotrophin-3 by Acting Selectively at the TrkA Receptor

Scott Pollack, Lisa Young, James Bilsland, Neil Wilkie, Semantha Ellis, Franz Hefti, Howard Broughton, and Sarah Harper

Departments of Biochemistry (S.P., N.W., S.E., F.H.), Pharmacology (L.Y., J.B., F.H., S.H.), and Medicinal Chemistry (F.H., H.B.), Merck Sharp and Dohme Research Laboratories, Neuroscience Research Centre, Harlow, Essex, United Kingdom

K-252b, a member of the staurosporine family of protein kinase inhibitors, selectively potentiates the activation of the nerve growth factor receptor, TrkA, by a nonpreferred ligand, neurotrophin-3 (NT-3), in a variety of cell types. At higher (micromolar) concentrations of K-252b, an inhibitory effect occurs because of the inhibitory action of K-252b on the Trk kinase. By examining analogs of K-252b, we identified the compound L-753,000 (NB-506), which potentiates the action of NT-3 on TrkA but is devoid of the inhibitory action of K-252b. L-753,000 was effective at nanomolar concentrations in a Chinese hamster ovary cell line that expressed TrkA but was devoid of p75, the low-affinity neurotrophin receptor. L-753,000 also potentiated the activation of mitogen-activating protein kinase signaling (downstream from Trk activation) by NT-3 in this cell line. Although L-753,000, like K-252b, had a negligible effect in the absence of NT-3, the compound was found to potentiate NT-3-induced survival in both rat and chick primary cultures of dissociated dorsal root ganglia (DRG) and on neurite outgrowth of chick DRG explants. Unlike K-252b, which at micromolar concentrations inhibits the survival response of NT-3 in dissociated rat DRG, L-753,000 continued to potentiate the actions of NT-3 up to a concentration of 10 µM. Furthermore, the compound, unlike K-252b, did not inhibit an unrelated protein kinase, protein kinase C, at concentrations up to 10 µM. Because L-753,000 selectively potentiates the NT-3-induced stimulation of TrkA without inhibiting Trks and other protein kinases, it represents a novel class of selective modifiers of neurotrophin actions.