Receptors and Channels

Gap junction beta-2 protein (connexin-26) is a transmembrane channel that, together with other connexins, forms a gap junction. Gap junctions allow low MW materials to flow from one cell to a neighboring cell. Defects in connexin-26 are the cause of deafness autosomal recessive type 1A (DFNB1A). DFNB1A is a form of sensorineural hearing loss. Sensorineural deafness results from damage to the neural receptors of the inner ear, the nerve pathways to the brain, or the area of the brain that receives sound information.

Gap junction alpha-1 protein (connexin-43) is a transmembrane channel that, together with other connexins, forms a gap junction. Gap junctions allow low MW materials to flow from one cell to a neighboring cell. Defects in connexin-43 are the cause of autosomal dominant oculodentodigital dysplasia (ODDD), also known as oculodentoosseous dysplasia. ODDD is a highly penetrant syndrome presenting with craniofacial (ocular, nasal, dental) and limb dysmorphisms, spastic paraplegia, and neurodegeneration.

Aquaporin-1 (AQP1) forms a water-specific channel that provides the plasma membranes of red cells and kidney proximal tubules with high permeability to water, thereby permitting water to move in the direction of an osmotic gradient. AQP1 is responsible for the Colton blood group system. Approximately 92% of Caucasians are Co(A+B-) (Ala-46), approximately 8% are Co(A+B+), and only 0.2% are Co(A-B+) (Val-46). Co(A-B-), which is very rare, is due to a complete absence of AQP1. AQP1 is pharmacologically inhibited by submillimolar concentrations of mercury.

Lymphatic vessel endothelial hyaluronic acid receptor 1 (LYVE-1) is a ligand-specific transporter trafficking between intracellular organelles and the plasma membrane. LYVE-1 is involved in autocrine regulation of cell growth mediated by growth regulators containing cell surface retention sequence binding (CRS). LYVE-1 acts as a hyaluronan transporter either by mediating its uptake for catabolism within lymphatic endothelial cells or its transport into the lumen of afferent lymphatic vessels for subsequent re-uptake and degradation in lymph nodes.