<p>TRPML2 activity is critical for endolysosomal integrity and chemokine secretion, and can be modulated by various ligands. Interestingly, two ML-SI3 isomers regulate TRPML2 oppositely. The molecular mechanism underlying this unique isomeric preference as well as the TRPML2 agonistic mechanism remains unknown. Here, we present six cryo-EM structures of human TRPML2 in distinct states revealing that the π-bulge of the S6 undergoes a π-α transition upon agonist binding, highlighting the remarkable role of the π-bulge in ion channel regulation. Moreover, we identify that PI(3,5)P<sub>2</sub> allosterically affects the pose of ML2-SA1, a TRPML2 specific activator, resulting in an open channel without the π-α transition. Functional and structural studies show that mutating the S5 of TRPML1 to that of TRPML2 enables the mutated TRPML1 to be activated by (+)ML-SI3 and ML2-SA1. Thus, our work elucidates the activation mechanism of TRPML channels and paves the way for the development of selective TRPML modulators.</p>

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TRPML2 in distinct states reveals the activation and modulation principles of the TRPML family

  • Philip Schmiege,
  • Dawid Jaślan,
  • Michael Fine,
  • Nidish Ponath Sadanandan,
  • Alexandra Hatton,
  • Nadia Elghobashi-Meinhardt,
  • Christian Grimm,
  • Xiaochun Li

摘要

TRPML2 activity is critical for endolysosomal integrity and chemokine secretion, and can be modulated by various ligands. Interestingly, two ML-SI3 isomers regulate TRPML2 oppositely. The molecular mechanism underlying this unique isomeric preference as well as the TRPML2 agonistic mechanism remains unknown. Here, we present six cryo-EM structures of human TRPML2 in distinct states revealing that the π-bulge of the S6 undergoes a π-α transition upon agonist binding, highlighting the remarkable role of the π-bulge in ion channel regulation. Moreover, we identify that PI(3,5)P2 allosterically affects the pose of ML2-SA1, a TRPML2 specific activator, resulting in an open channel without the π-α transition. Functional and structural studies show that mutating the S5 of TRPML1 to that of TRPML2 enables the mutated TRPML1 to be activated by (+)ML-SI3 and ML2-SA1. Thus, our work elucidates the activation mechanism of TRPML channels and paves the way for the development of selective TRPML modulators.