Practice question

Microtubule associated proteins of structural type stabilize filaments by binding along walls and bridging protofilaments reducing catastrophe and increasing flexural rigidity. Members include MAP2 and tau families as well as MAP4 sharing homologous microtubule binding repeat domains but exhibiting expression differences: tau enriched in axons MAP2 in dendrites MAP4 broadly in non neuronal tissues and also neurons providing versatility. Tau and MAP2 classically promote assembly and bundling reducing catastrophe promoting rescue and increasing persistence length. MAP4 participates similarly forming flexible side arms that project outward crosslinking microtubules and regulating organelle spacing and cell shape. Recent work shows MAP4 can stabilize mitotic spindle and interphase arrays while doublecortin also stabilizes. XMAP215 acts as polymerase not pure stabilizer alone EB1 tracks plus ends. MAP4 exemplifies MAP that stabilizes particularly useful example for neuronal and non neuronal context where multiple isoforms cooperate to create durable tracks resisting compressive forces during growth cone advance and maintaining axonal transport corridors essential for neuronal function.