Microtubule-Associated Proteins (MAPs): Life’s Mini Conveyor Belts
On the basis of their microtubule interaction motif, most structural MAPs belong to either the MAP1A/1B or the MAP2/Tau family, and key players are described below4,5. MAP1A is predominantly expressed in the dendrites of adult neurons where it is important for dendrite formation, while MAP1B is mainly expressed in the axons of developing neurons and plays a role in axonal outgrowth6. Another member of the MAP1A/1B family, MAP1S, is expressed in a variety of neuronal and non-neuronal tissues where it anchors the microtubule-organizing center to the centrosome during mitosis7,8. MAP2 is preferentially expressed in neurons, is important for crosslinking adjacent microtubules, and shares some functional redundancy with MAP1B9. It also interacts with F-actin, in a process thought to promote neurite outgrowth10. Tau is primarily found in axons and also shares some redundancy with MAP1B4. A hyperphosphorylated form of tau has been implicated in the pathology of Alzheimer disease11. The MAP2/Tau family also includes the neuronal and non-neuronal MAP4, important for cell division12.