Molecular mechanism of hyperactivation conferred by a truncation of TRPA1

Abstract

A drastic TRPA1 mutant (R919*) identified in CRAMPT syndrome patients has not been mechanistically characterized. Here, we show that the R919* mutant confers hyperactivity when co-expressed with wild type (WT) TRPA1. Using functional and biochemical assays, we reveal that the R919* mutant co-assembles with WT TRPA1 subunits into heteromeric channels in heterologous cells that are functional at the plasma membrane. The R919* mutant hyperactivates channels by enhancing agonist sensitivity and calcium permeability, which could account for the observed neuronal hypersensitivity-hyperexcitability symptoms. We postulate that R919* TRPA1 subunits contribute to heteromeric channel sensitization by altering pore architecture and lowering energetic barriers to channel activation contributed by the missing regions. Our results expand the physiological impact of nonsense mutations, reveal a genetically tractable mechanism for selective channel sensitization, uncover insights into the process of TRPA1 gating, and provide an impetus for genetic analysis of patients with CRAMPT or other stochastic pain syndromes.

A drastic TRPA1 mutant was identified in patients with CRAMPT syndrome, but it has not been functionally characterized. Here, the authors find this mutant confers gain-of-function by co-assembling with wild type protein to form hyperactive channels.