非運動性キネシンKIF7がヘッジホッグシグナル伝達における機能に適応させる保存されたキネシン原理

KIF7 is an atypical, non-motile kinesin that regulates Hedgehog signaling by concentrating GLI transcription factors at the cilium tip. How canonical kinesin principles for intracellular transport are repurposed to support KIF7's function as a signaling scaffold remains unclear. KIF7 exists in an autoinhibited state that is relieved by GLI binding, promoting microtubule association. We examined this regulatory mechanism by combining HDX-MS and AlphaFold modeling of a minimal KIF7 dimer, both alone and in complex with the GLI2 zinc-finger domain. Our HDX-MS data indicate that the highly negatively charged neck-coil dimerization domain of KIF7, which serves as the GLI2-binding site, is intramolecularly protected in the absence of GLI2. Consistent with this, AlphaFold models suggest that the motor domain folds back onto the neck-coil via KIF7's unusually long neck-linker, sterically occluding the microtubule-binding interface. This occurs through a mechanism conceptually analogous to, but structurally distinct from, autoinhibition in motile kinesins. GLI2 binding to the KIF7 neck-coil displaces the motor domain and induces allosteric changes that propagate to the microtubule-binding surface, thereby activating microtubule binding. ATP turnover further modulates KIF7's microtubule binding-unbinding equilibrium. Together, these findings reveal how a kinesin is adapted for a non-motile function as a scaffold in Hedgehog signaling.