Patent WO-2009008950-A2 (WO)
Title: Identification of trpml3 (mcoln3) as a salty taste receptor and use in assays for identifying taste (salty) modulators and/or therapeutics that modulate sodium transport, absorption or excretion and/or aldosterone and/or vasopressin production or release
Inventor: MOYER BRYAN
IPC: C12N5/10
Filed: 2008-06-06
Abstract: The present invention relates to high-throughput mammalian and medium-throughput oocyte-based electrophysiological assays for identifying human TRPML3 modulators, preferably TRPML3 enhancers. Compounds that modulate TRPML3 function in the assay are expected to affect salty taste in humans. The inventive electrophysiological assays, such as the two-electrode voltage-clamp technique, facilitate the identification of compounds which specifically modulate human TRPML3. The assays of the invention provide a robust screen useful to detect compounds that facilitate (enhance) or inhibit TRPML3 function. Compounds that enhance or block TRPML3 channel activity should thereby modulate salty taste. In addition, these compounds may be used to regulate sodium excretion, urinary output and other biological functions relating to sodium levels. This invention relates to the elucidation that TRPML3 is involved in salty taste perception in primates including humans and likely other mammals (given the significance of sodium and other ions to physiological functions and conditions this phenotype is likely strongly conserved in different animals). The TRPML3 gene also modulates one or more of sodium metabolism, sodium excretion, blood pressure, fluid retention, cardiac function and urinary functions such as urine production and excretion. The inventors have identified TRPML3 as encoding a salty taste receptor in primates and humans (and likely other mammals) based on gene expression assays which have determined that TRPML3 is expressed specifically in taste bud cells and not in lingual epithelial cells, similar assays that have determined that TRPML3 is specifically expressed or enriched in the top half of taste bud cells in a subset of taste cells which do not express TRPM5 or PKD2L1, prior reports that document the expression of TRPML3 in other sensory organs such as the ear (therefore further substantiating the role of TRPML3 as a 'professional' sensory gene), the strong expression of TRPML3 in the adrenal glands which play a strong role in regulation of sodium metabolism (as they regulate aldosterone a key molecule in sodium metabolism), and related thereto the fact that an autoimmune disease that elicits strong salt cravings, Addison's disease, involves destruction of the adrenal glands, and functional (electrophysiological) studies which indicate that TRPML3 conducts sodium and exhibits biochemical characteristics consistent with a human salty taste receptor (passes K+, Li+, and is amiloride-insensitive.) This application also discloses novel rationales and methods for identifying primate taste-specific genes, including genes involved in salty taste perception, especially human salty taste perception, as well as genes involved in sweet, bitter, umami, and sour taste and other taste perceptions including fat taste, and genes involved in other taste cell or taste receptor related activities such as digestive function and digestive related diseases, taste cell turnover, immunoregulation of the oral and digestive tract, and metabolic regulation such as in diabetes and obesity. The genes identified using these methods, can be used in assays for identifying taste modulators (enhancers or blockers) and potential therapeutics that modulate the activity of these genes. These compounds have potential application in modulating (enhancing or blocking) taste perception, especially salty, fat or sour taste perception and as potential therapeutics. In addition, this invention relates to novel methods for identifying taste-specific genes that can be used as markers for different taste cell types, including sweet, bitter, umami, sour, salt, and other taste cells in mammals as well as assays that measure the activity of the sweet, bitter, umami, or sour receptor in the presence of these genes to identify modulators of sweet, bitter, umami, and sour taste and to identify therapeutics especially for treating digestive or metabolic disorders, taste loss, and or