J Gen Physiol. 2012 Nov;140(5):541-55. doi: 10.1085/jgp.201210810.
Distinct properties of Ca2+-calmodulin binding to N- and C-terminal regulatory regions of the TRPV1 channel.
Lau, S. Y., Procko, E., Gaudet, R.,
["Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA."]
["Department of Molecular and Cellular Biology, Harvard University, Cambridge, MA 02138, USA."]
Transient receptor potential (TRP) vanilloid 1 (TRPV1) is a molecular pain receptor belonging to the TRP superfamily of nonselective cation channels. As a polymodal receptor, TRPV1 responds to heat and a wide range of chemical stimuli. The influx of calcium after channel activation serves as a negative feedback mechanism leading to TRPV1 desensitization. The cellular calcium sensor calmodulin (CaM) likely participates in the desensitization of TRPV1. Two CaM-binding sites are identified in TRPV1: the N-terminal ankyrin repeat domain (ARD) and a short distal C-terminal (CT) segment. Here, we present the crystal structure of calcium-bound CaM (Ca(2+)-CaM) in complex with the TRPV1-CT segment, determined to 1.95-A resolution. The two lobes of Ca(2+)-CaM wrap around a helical TRPV1-CT segment in an antiparallel orientation, and two hydrophobic anchors, W787 and L796, contact the C-lobe and N-lobe of Ca(2+)-CaM, respectively. This structure is similar to canonical Ca(2+)-CaM-peptide complexes, although TRPV1 contains no classical CaM recognition sequence motif. Using structural and mutational studies, we established the TRPV1 C terminus as a high affinity Ca(2+)-CaM-binding site in both the isolated TRPV1 C terminus and in full-length TRPV1. Although a ternary complex of CaM, TRPV1-ARD, and TRPV1-CT had previously been postulated, we found no biochemical evidence of such a complex. In electrophysiology studies, mutation of the Ca(2+)-CaM-binding site on TRPV1-ARD abolished desensitization in response to repeated application of capsaicin, whereas mutation of the Ca(2+)-CaM-binding site in TRPV1-CT led to a more subtle phenotype of slowed and reduced TRPV1 desensitization. In summary, our results show that the TRPV1-ARD is an important mediator of TRPV1 desensitization, whereas TRPV1-CT has higher affinity for CaM and is likely involved in separate regulatory mechanisms.
PMID: 23109716

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Validation: In vitro validation
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Assay with recombinant proteins | Reference | |||||||||
TRP channel construct | Interactor construct | |||||||||
TRP channel | Interactor | Method | Species | Region | Expression system | Species | Region | Expression system | ||
TRPV1 |
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Calmodulin | Fast performance liquid chromatography | Rat | 759-802 | E. coli | Human | Full-length | E. coli | 23109716 |
TRPV1 |
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Calmodulin | X-ray diffraction-structural analysis | Rat | 784-798 | E. coli | Human | Full-length | E. coli | 23109716 |
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

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Characterization
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Binding region mapping | Stoichiometry | Affinity (Kd) | Reference | |||||||
TRP channel | Interactor | |||||||||
TRP channel | Interactor | Method | Species | Region | Species | Region | ||||
TRPV1 |
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Calmodulin | X-ray diffraction-structural analysis | Rat | 784-798 | Human | 11-145 | 23109716 |
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)

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Functional consequence
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TRP channel | Interactor | Method | Post-translational modification | Subcellular trafficking | Activity | Reference | ||||||
TRPV1 |
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Calmodulin | Patch clamp | Sensitization | 23109716 |
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click the arrow icon to show interactions only between the corresponding TRP channel and the interactor)
