Pathway: TRP channels
Reactions in pathway: TRP channels :
TRP channels
Transient receptor potential (TRP) channel proteins were first discovered in Drosophila melanogaster and have many homologues in other species including humans. TRPs form cationic channels that can detect sensory stimuli such as temperature, pH or oxidative stress and transduce that into either electrical (change in membrane potential) or chemical signals (change in intracellular Ca2+ concentration). In humans, there are 28 TRP genes arranged into 6 subfamilies; TRPA, TRPC, TRPM, TRPML, TRPP, and TRPV (Wu et al. 2010). Each TRP channel subunit consists of six putative transmembrane-spanning segments (S1-S6) with a pore-forming loop between S5 and S6. These subunits assemble into tetramers to form functional channels. All functionally characterized TRP channels are permeable to Ca2+ except TRMP4 and 5 which are only permeable to monovalent cations such as Na+ (Latorre et al. 2009). Most TRPs can cause channelopathies which are risk factors for many disease states (Nilius & Owsianik 2010).
Ion channels mediate the flow of ions across the plasma membrane of cells. They are integral membrane proteins, typically a multimer of proteins, which, when arranged in the membrane, create a pore for the flow of ions. There are different types of ion channels. P-type ATPases undergo conformational changes to translocate ions. Ligand-gated ion channels operate like a gate, opened or closed by a chemical signal. Voltage-gated ion channels are activated by changes in electrical potential difference at the membrane (Purves, 2001; Kuhlbrandt, 2004).
By definition cells have a critical separation between inner (cytoplasmic) and outer (extracellular) compartments. This separation provides for protection, gradient assembly, and environmental control but at the same time isolates the interior compartments of the cell from energy resources, oxygen, and raw materials. Cells have evolved a myriad of mechanisms to regulate, and enable transportation of small molecules ascross plasma membranes and between cellular organelle compartments within cells.