STMN2: Membrane-Binding Microtubule Regulator or Tubulin Effector?

STMN2, a protein implicated in motor neuron degeneration, is widely viewed as a membrane-associated microtubule inhibitor, but emerging evidence challenges whether this activity defined its cellular function. Three alternative models integrates available evidence to offer perspectives beyond microtubule regulation. The vesicle cargo adaptor model proposes that STMN2 recruits diverse cargos to transport vesicles for axonal delivery. The membrane-bound signaling messenger model links STMN2 turnover to local signaling, effector, degradation, or effector release. The traffic director model proposes that STMN2 regulates cargo routing between delivery and degradative pathways. These models are not mutually exclusive and position tubulin binding as a regulator of STMN2 function rather than its defining activity.