A tyrosine residue in TM6 of the Vanilloid Receptor TRPV1 involved in desensitization and calcium permeability of capsaicin-activated currents

The Vanilloid Receptor TRPV1 is a non-selective cation channel with a high relative Ca²⁺ permeability. TRPV1 exhibits slow desensitization, a potential mechanism regulating adaptation of peripheral sensory neurons to noxious stimuli. The predicted folding pattern of TRPV1 resembles that of voltage-gated channels. Sequence alignment of segments 6 of TRPV1 and voltage-gated Na⁺ channels reveals a conserved aromatic amino acid that in Na⁺ channels is involved in fast inactivation and pharmacological block. We found that replacing this tyrosine Y671 by positively charged lysine (K) completely abrogated Ca²⁺-dependent desensitization. Y671K also exhibited significant reduction in Ca²⁺ permeability that was not responsible for the lack in desensitization. Substitution of Y671 with negatively charged aspartate or uncharged alanine slightly altered desensitization but left Ca²⁺ permeability unchanged. Substitution of Y671 with positively charged arginine produced a phenotype similar to Y671K. We propose that residue Y671 is critical for the high relative Ca²⁺ permeability of TRPV1 and participates in the structural rearrangements of the channel protein leading to Ca²⁺-dependent desensitization.