The apolipoprotein E type 4 allele is a susceptibility gene for late-onset 
Alzheimer's disease. Apolipoprotein E is found in neurons, some of which contain 
paired helical filaments made of the microtubule-associated protein tau. 
Previous studies have demonstrated that the apoE3 isoform, but not the apoE4 
isoform, binds tau with high avidity. Because the microtubule-associated protein 
MAP2c also effects microtubule assembly and stability, we examined interactions 
between apoE isoforms and MAP2c. Similar to the tau-binding results, apoE3, but 
not apoE4, bound MAP2c. Binding was detectable down to 10(-9) M MAP2c and 10(-8) 
M apoE3. Isoform-specific interactions of apoE with the microtubule-associated 
proteins MAP2c and tau might affect intracellular maintenance of microtubules 
and could contribute to a time-dependent pathogenesis of Alzheimer's disease.