NEUROTROPHIC AND NEUROPROTECTIVE EFFECTS OF NEURON-SPECIFIC ENOLASE ON CULTURED NEURONS FROM EMBRYONIC RAT-BRAIN

We previously reported that the gamma gamma-isozyme of enolase (neuron -specific enolase, NSE), one of the glycolytic enzymes, promoted the s urvival of embryonic rat neocortical neurons in culture, but alpha alp ha-isozyme (non-neuronal enolase) had no effect. In the present study, the neurotrophic effects of NSE on cultured mesencephalic and spinal neurons from rat embryo were examined. NSE promoted the survival of ne urons not only in neocortical cultures but also in mesencephalic and s pinal cord cultures. Furthermore, NSE showed neuroprotective action on cultured neocortical neurons in a low-oxygen atmosphere. By contrast, non-neuronal enolase did not show any neurotrophic or neuroprotective activities. To clarify the mechanism of the neurotrophic effect of NS E, the binding of NSE to cultured neurons was determined by radio-rece ptor assay using I-125-labelled NSE. The specific binding, which was d ose-dependent, saturable, and calcium-dependent, could be detected. Th ese results suggest that NSE has neurotrophic and neuroprotective effe cts on rather a broad spectrum of neurons in the central nervous syste m. The existence of specific binding of NSE to cultured neurons sugges ts the possibility that receptor-like or carrier-like molecules on the neuronal surface are involved in the neurotrophic activity of NSE.