Fibroblast growth factor 2 requires complex formation with ATP for neuroprotective activity

The neurotrophic and neuroprotective activity of fibroblast growth factor (FGF2) is well documented. In this study, we attempted to demonstrate that binding of ATP to FGF2 is essential for its neuroprotective effect. Incubation of primary cultures of rat embryonic (E18) cortical neurons with alkaline phosphatase decreased the ATP concentration in the culture medium from about 8 to 0.3 nM measured luminometrically. Reduction of ATP concentration below 1 nM abolished the neuroprotective effect of FGF2. However, when the more stable nucleotide triphosphate gammaS-ATP was used which could not be cleaved by alkaline phosphatase, FGF2 still protected the cultured cortical neurons against damage. In control experiments alkaline phosphatase alone did not influence neuroprotection. In addition, also ATPase and apyrase were used as ATP cleaving enzymes. Added to the culture medium, both enzymes were capable of decreasing ATP below the critical level of approximately 1 nM, and the neuroprotective activity of FGF2 was abolished. Thus, our results demonstrate for the first time that the FGF2/ATP complex but not FGF2 alone mediates neuroprotection.