Distinct properties of Ca²⁺-calmodulin binding to N- and C-terminal regulatory regions of the TRPV1 channel

Journal Article · Thu Nov 01 00:00:00 EDT 2012 · Journal of General Physiology

DOI:https://doi.org/10.1085/jgp.201210810· OSTI ID:1054358

Lau, Sze-Yi; Procko, Erik; Gaudet, Rachelle ^[1]

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1. Harvard

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 (Ca²⁺–CaM) in complex with the TRPV1-CT segment, determined to 1.95-Å resolution. The two lobes of Ca²⁺–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 Ca²⁺–CaM, respectively. This structure is similar to canonical Ca²⁺–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 Ca²⁺–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 Ca²⁺–CaM-binding site on TRPV1-ARD abolished desensitization in response to repeated application of capsaicin, whereas mutation of the Ca²⁺–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.

• Research Organization: Advanced Photon Source (APS), Argonne National Laboratory (ANL), Argonne, IL (US)
• Sponsoring Organization: USDOE Office of Science (SC)
• OSTI ID: 1054358
• Journal Information: Journal of General Physiology, Journal Name: Journal of General Physiology Journal Issue: (5) ; 2012 Vol. 140; ISSN 0022-1295
• Country of Publication: United States
• Language: ENGLISH