The femtomolar-acting NAP interacts with microtubules: Novel aspects of astrocyte protection.

Activity-dependent neuroprotective protein (ADNP), a gene product essential for brain formation, contains a short octapeptide sequence NAPVSIPQ (NAP) that protects neurons against a wide variety of insults. At the pico-molar concentration range, NAP provides neuroprotection by direct interaction with neurons. At the femtomolar concentration range, NAP requires the presence of glial cells to provide neuroprotection. To further understand the mechanism of neuroprotection afforded by NAP, specific binding proteins were searched for. Tubulin, the major subunit protein of microtubules, was identified as a NAP binding molecule. NAP structure allows membrane penetration, followed by tubulin binding and facilitation of microtubule assembly toward cellular protection in astrocytes. NAP (10(-15) M) promoted microtubule assembly in vitro and protected astrocytes against zinc intoxication which is associated with microtubule disruption. A two hour incubation period of astrocytes with femtomolar concentrations of NAP resulted in microtubule re-organization and transient increases in immunoreactive non-phosphorylated tau. Microtubules are the key component of the neuronal and glial cytoskeleton that regulates cell division, differentiation and protection, while tau pathology is a major contributor to Alzheimer's disease and other dementias. The findings described here may open up new horizons in research and development of neuroprotective compounds.