Microtubule-associated protein 2 (MAP2) is a neuronal phosphoprotein that regulates the structure and stability of microtubules, neuronal morphogenesis, cytoskeleton dynamics and organelle trafficking in axons and dendrites. Phosphorylation of MAP2 modulates its association with the cytoskeleton and is developmentally regulated. Serine 136, threonine 1620 and threonine 1623 of MAP2 are phosphorylated by GSK3 and p44/42 MAP kinases. Phosphorylation at threonine 1620/1623 by GSK3 inhibits MAP2 association with microtubules and microtubule stability.