Transient receptor potential (TRP) protein expression in the corneal epithelial layer contributes to the maintenance of tissue transparency. These proteins are members of a superfamily that form nonselective cation channels. This superfamily is a product of 28 different genes that are subdivided into six different subfamilies according to differences in amino acid sequence homology. The six subfamilies have very diverse functions. They are: 1) canonical (C); 2) vanilloid (V); 3) melastatin (M); 4) ankyrin (A); 5) polycystin (PP); 6) mucolipin (ML). TRP channels are composed of four monomeric subunits that are either members of the same or different subfamilies. In the corneal epithelium, C, V, and A subfamily subtype expression was identified. These include TRPV1-4, TRPC4, and TRPA1, which upon activation by either environmental stresses or selective ligands induce adaptive responses to stresses through transient increases in Ca2+ influx. Even though TRPs' Ca2+ permeability is variable relative to other cations, TRP activation is sufficient to stimulate mitogen-activated protein kinase cascade signaling through epidermal growth factor receptor transactivation. The host of TRP-mediated responses includes stimulation of cell proliferation, migration, regulatory volume behavior, and the release of a host of proinflammatory cytokines and chemoattractants. This review describes the multiple roles of these different channel subtypes in eliciting responses underlying maintenance of corneal epithelial function in health and disease.
- Wound healing