Focus on TRP channels in cystic fibrosis

The Transient Receptor Potential (TRP) protein superfamily is a group of cation channels expressed in various cell types and involved in respiratory diseases such as cystic fibrosis (CF), the genetic disease caused by CF Transmembrane conductance Regulator (CFTR) mutations. In human airway epithelial cells, there is growing evidence for a functional link between CFTR and TRP channels. TRP channels contribute to transmitting extracellular signals into the cells and, in an indirect manner, to CFTR activity via a Ca²⁺ rise signaling. Indeed, mutated CFTR-epithelial cells are characterized by an increased Ca²⁺ influx and, on the opposite, by a decreased of magnesium influx, both being mediated by TRP channels. This increasing cellular Ca²⁺ triggers the activation of calcium-activated chloride channels (CaCC) or CFTR itself, via adenylyl cyclase, PKA and tyrosine kinases activation, but also leads to an exaltation of the inflammatory response. Another shortcoming in mutated CFTR-epithelial cells is a [Mg²⁺]_i decrease, associated with impaired TRPM7 functioning. This deregulation has to be taken into consideration in CF physiopathology, as Mg²⁺ is required for ATP hydrolysis and CFTR activity. The modulation of druggable TRP channels could supplement CF therapy either an anti-inflammatory drug or for CFTR potentiation, according to the balance between exacerbation and respite phases. The present paper focus on TRPA1, TRPC6, TRPM7, TRPV2, TRPV4, TRPV6 and ORAI 1, the proteins identified, for now, as dysfunctional channels, in CF cells.