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).