Practice question

Stable microtubule subsets resist cold and nocodazole depolymerization due to decoration by classical structural MAPs reducing dynamics. Members include MAP2 and tau families as well as MAP1B and CLASP. MAP2 specifically expressed in neurons predominantly dendritic compartment forms projection domain protruding from filament serving as spacing crosslinker and microtubule binding repeats with positive charge neutralizing acidic tubulin C terminal tails bridging adjacent protofilaments reinforcing lateral contacts mechanically stiffening filament suppressing catastrophe by maintaining straight lattice conformation resisting GDP induced curling. Activity promotes rescue and long lived polymer essential for dendrite morphogenesis. Modulated by phosphorylation through MARK CDK5 reducing affinity to allow remodeling during branching and synaptic plasticity. CLASP also suppresses catastrophe at plus ends but MAP2 binds along lattice providing continuous stability. Katanin severs rather than stabilizes tau similar to MAP2 in axons. Therefore MAP2 exemplifies microtubule binding protein that suppresses catastrophe promotes stability crucial for dendrite outgrowth and plasticity maintenance and transport fidelity.