National Institutes of Health/National Institute of Neurological Disorders and Stroke (NIH/NINDS)
R35NS097241
United States
National Institutes of Health/National Institute of Biomedical Imaging and Bioengineering (NIH/NIBIB)
DP2EB020402
United States
Citation
Journal: Nature / Year: 2017 Title: Cryo-electron microscopy structure of the lysosomal calcium-permeable channel TRPML3. Authors: Marscha Hirschi / Mark A Herzik / Jinhong Wie / Yang Suo / William F Borschel / Dejian Ren / Gabriel C Lander / Seok-Yong Lee / Abstract: The modulation of ion channel activity by lipids is increasingly recognized as a fundamental component of cellular signalling. The transient receptor potential mucolipin (TRPML) channel family ...The modulation of ion channel activity by lipids is increasingly recognized as a fundamental component of cellular signalling. The transient receptor potential mucolipin (TRPML) channel family belongs to the TRP superfamily and is composed of three members: TRPML1-TRPML3. TRPMLs are the major Ca-permeable channels on late endosomes and lysosomes (LEL). They regulate the release of Ca from organelles, which is important for various physiological processes, including organelle trafficking and fusion. Loss-of-function mutations in the MCOLN1 gene, which encodes TRPML1, cause the neurodegenerative lysosomal storage disorder mucolipidosis type IV, and a gain-of-function mutation (Ala419Pro) in TRPML3 gives rise to the varitint-waddler (Va) mouse phenotype. Notably, TRPML channels are activated by the low-abundance and LEL-enriched signalling lipid phosphatidylinositol-3,5-bisphosphate (PtdIns(3,5)P), whereas other phosphoinositides such as PtdIns(4,5)P, which is enriched in plasma membranes, inhibit TRPMLs. Conserved basic residues at the N terminus of the channel are important for activation by PtdIns(3,5)P and inhibition by PtdIns(4,5)P. However, owing to a lack of structural information, the mechanism by which TRPML channels recognize PtdIns(3,5)P and increase their Ca conductance remains unclear. Here we present the cryo-electron microscopy (cryo-EM) structure of a full-length TRPML3 channel from the common marmoset (Callithrix jacchus) at an overall resolution of 2.9 Å. Our structure reveals not only the molecular basis of ion conduction but also the unique architecture of TRPMLs, wherein the voltage sensor-like domain is linked to the pore via a cytosolic domain that we term the mucolipin domain. Combined with functional studies, these data suggest that the mucolipin domain is responsible for PtdIns(3,5)P binding and subsequent channel activation, and that it acts as a 'gating pulley' for lipid-dependent TRPML gating.
History
Deposition
Jun 8, 2017
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Header (metadata) release
Aug 9, 2017
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Map release
Oct 11, 2017
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Update
Mar 13, 2024
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Current status
Mar 13, 2024
Processing site: RCSB / Status: Released
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Structure visualization
Movie
Surface view with section colored by density value
Film or detector model: GATAN K2 SUMMIT (4k x 4k) / Detector mode: SUPER-RESOLUTION / Average exposure time: 12.0 sec. / Average electron dose: 63.0 e/Å2
Electron beam
Acceleration voltage: 300 kV / Electron source: FIELD EMISSION GUN
Electron optics
Illumination mode: FLOOD BEAM / Imaging mode: BRIGHT FIELD
Experimental equipment
Model: Titan Krios / Image courtesy: FEI Company
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Image processing
Startup model
Type of model: NONE
Final reconstruction
Applied symmetry - Point group: C4 (4 fold cyclic) / Resolution.type: BY AUTHOR / Resolution: 2.94 Å / Resolution method: FSC 0.143 CUT-OFF / Number images used: 104084
Initial angle assignment
Type: PROJECTION MATCHING
Final angle assignment
Type: PROJECTION MATCHING
FSC plot (resolution estimation)
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