Insights into the Function and Evolution of Taste 1 Receptor Gene Family in the Carnivore Fish Gilthead Seabream (<i>Sparus aurata</i>)

• Main Authors: Anna Rita Angotzi, Sara Puchol, Jose M. Cerdá-Reverter, Sofia Morais
• Format: Article
• Language: English
• Published: MDPI AG 2020-10-01
• Series: International Journal of Molecular Sciences
• Subjects: <i>T1R</i> receptors; <i>G</i>αi protein; <i>alpha subunit</i>; taste; umami; amino acids
• Online Access: https://www.mdpi.com/1422-0067/21/20/7732

A plethora of molecular and functional studies in tetrapods has led to the discovery of multiple taste 1 receptor (<i>T1R</i>) genes encoding G-protein coupled receptors (<i>GPCRs</i>) responsible for sweet (<i>T1R2</i> + <i>T1R3</i>) and umami (<i>T1R1 </i>+ <i>T1R3</i>) taste. In fish, the <i>T1R</i> gene family repertoires greatly expanded because of several <i>T1R2</i> gene duplications, and recent studies have shown <i>T1R2</i> functional divergence from canonical mammalian sweet taste perceptions, putatively as an adaptive mechanism to develop distinct feeding strategies in highly diverse aquatic habitats. We addressed this question in the carnivore fish gilthead seabream (<i>Sparus aurata</i>), a model species of aquaculture interest, and found that the <i>saT1R</i> gene repertoire consists of eight members including <i>saT1R1</i>, <i>saT1R3</i> and six <i>saT1R2a</i>-<i>f </i>gene duplicates, adding further evidence to the evolutionary complexity of fish<i>T1Rs</i> families. To analyze <i>saT1R</i> taste functions, we first developed a stable gene reporter system based on Ca²⁺-dependent calcineurin/<i>NFAT</i> signaling to examine specifically in vitro the responses of a subset of <i>saT1R</i> heterodimers to L-amino acids (L-AAs) and sweet ligands. We show that although differentially tuned in sensitivity and magnitude of responses, <i>saT1R1</i>/<i>R3</i>, <i>saT1R2a</i>/<i>R3</i> and <i>saT1R2b</i>/<i>R3</i> may equally serve to transduce amino acid taste sensations. Furthermore, we present preliminary information on the potential involvement of the <i>Gi</i> protein <i>alpha subunits saGαi1</i> and <i>saGαi2</i> in taste signal transduction.