K252a and staurosporine microbial alkaloid toxins as prototype of neurotropic drugs.

K252 family of alkaloid toxins-kinase inhibitors are the most widely used compounds in biological research on the role of protein kinases in cellular transduction systems, biological functions and pathophysiology of neurological disorders. The wide research interest in these toxins is due to their potency in inhibiting cellular protein kinases. However, lack of kinase specificity is one of their major drawbacks. Synthesis of new K252 derivatives can be expected to open up a new generation of kinase inhibitors. Staurosporine might be considered as a prototype neurotropic drug in view of its ability to induce neurite outgrowth and to increase tau protein levels. Because it mimics some of the neuroprotective effects of NGF and might blocks certain signals required to enhance cellular levels and/or beta amyloid processing, staurosporine might play a beneficial role in the treatment of Alzheimer's disease. The ability of staurosporine to promote neuronal regeneration and brain cholinergic neurons survival has been also demonstrated in animal studies (Nabeshima et al., 1991). The beneficial effects of K252a on the experimental autoimmune encephalomyelitis (EAE) disease mice model and it's ability to supress macrophage activation suggest an important role of protein kinases inhibitors as immunosupressive agents. These results may also point to the potential clinical relevance of K252 microbial toxins as prototypes for the development of new drugs for the management of neuronal diseases.