Otop1, short for Otopetrin 1, is a proton-selective ion channel. It is crucial for multiple biological functions, especially in taste sensation and potentially in alkaline sensing. In the taste system, it functions as a sensor for sour taste [3,4], ammonium chloride taste [2], and is expressed in sour (Type III) taste receptor cells (TRCs) [2]. It may also participate in alkaline sensation in vertebrates as it can be directly activated by extracellular alkali [1].

In Otop1-/-mouse strains, taste responses to NH4Cl measured from isolated Type III TRCs or gustatory nerves were strongly attenuated or eliminated, revealing its role in mediating a major component of the taste of NH4Cl [2]. Also, knockout of Otop1 in mice eliminates acid responses from sour-sensing TRCs, indicating its essentiality in sour sensing [4].

In conclusion, Otop1 is an important ion channel in taste transduction, being involved in sensing both acidic and certain alkaline-related taste stimuli. The use of Otop1 knockout mouse models has significantly contributed to understanding its role in taste-related biological processes, specifically in sour and ammonium chloride taste perception.

References:

1. Tian, Lifeng, Zhang, Hao, Yang, Shilong, Luo, Lei, Lai, Ren. 2023. Vertebrate OTOP1 is also an alkali-activated channel. In Nature communications, 14, 26. doi:10.1038/s41467-022-35754-9. https://pubmed.ncbi.nlm.nih.gov/36596786/

2. Liang, Ziyu, Wilson, Courtney E, Teng, Bochuan, Kinnamon, Sue C, Liman, Emily R. 2023. The proton channel OTOP1 is a sensor for the taste of ammonium chloride. In Nature communications, 14, 6194. doi:10.1038/s41467-023-41637-4. https://pubmed.ncbi.nlm.nih.gov/37798269/

3. Taruno, Akiyuki, Nomura, Kengo, Kusakizako, Tsukasa, Nureki, Osamu, Foskett, J Kevin. 2020. Taste transduction and channel synapses in taste buds. In Pflugers Archiv : European journal of physiology, 473, 3-13. doi:10.1007/s00424-020-02464-4. https://pubmed.ncbi.nlm.nih.gov/32936320/

4. Zhang, Jin, Jin, Hao, Zhang, Wenyi, Ye, Mingyu, Zuker, Charles S. 2019. Sour Sensing from the Tongue to the Brain. In Cell, 179, 392-402.e15. doi:10.1016/j.cell.2019.08.031. https://pubmed.ncbi.nlm.nih.gov/31543264/