Otopetrin proton channels as targets for pharmaceutical discovery

A method of identifying a modulator of otopetrin-mediated proton translocation activity comprising:

• (a) contacting an otopetrin polypeptide, or functional portion thereof, or host cell expressing said polypeptide with a test compound, wherein said otopetrin polypeptide is selected from the group consisting of:
• a mammalian otopetrin polypeptide;
• Otop1;
• Otop2;
• Otop3;
• an insect otopetrin polypeptide;
• and an otopetrin polypeptide that is at least 80% identical, at least 85% identical, at least 90% identical, at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, at least 99% identical, or 100% identical to an otopetrin polypeptide sequence of any one of SEQ ID Nos:1-9;
• and
• (b) determining a proton translocation activity mediated by the otopetrin polypeptide, or the functional portion thereof;
• wherein an increase or decrease of at least 1% of the proton translocation activity, compared to an amount of proton translocation activity determined in an absence of the test compound, identifies the test compound as a modulator of the proton translocation activity mediated by the otopetrin polypeptide, or the functional portion thereof.

A method of identifying a modulator of otopetrin-mediated proton translocation activity comprising:

• (a) measuring a proton translocation activity mediated by an otopetrin polypeptide, or a functional portion thereof, (i) in the presence of a test compound, and (ii) in the absence of the test compound, wherein said otopetrin polypeptide is selected from the group consisting of:
• a mammalian otopetrin polypeptide;
• Otop1;
• Otop2;
• Otop3;
• an insect otopetrin polypeptide;
• and an otopetrin polypeptide that is at least 80% identical, at least 85% identical, at least 90% identical, at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, at least 99% identical, or 100% identical to an otopetrin polypeptide sequence of any one of SEQ ID Nos:1-9;
• and
• (b) determining a difference between the proton translocation activity measured in (a)(i) compared to the proton translocation activity measured in (a)(ii), thereby identifying the test compound as a modulator of the proton translocation activity mediated by the otopetrin polypeptide, or the functional portion thereof.

A system for sensing proton translocation activity through a membrane channel, the system comprising:

• one or more heterologous otopetrin polypeptides selected from the group consisting of:
• a mammalian otopetrin polypeptide;
• Otop1;
• Otop2;
• Otop3;
• an insect otopetrin polypeptide;
• and an otopetrin polypeptide that is at least 80% identical, at least 85% identical, at least 90% identical, at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, at least 99% identical, or 100% identical to an otopetrin polypeptide sequence of any one of SEQ ID Nos:1-9;
• or a functional portion thereof;
• wherein the one or more otopetrin polypeptides is integrated into a membrane of a cell, wherein the cell comprises one or more nucleic acids that direct the expression of the one or more heterologous otopetrin polypeptides or functional portion thereof and the cell comprises a fluorescent pH indicator or a fluorescent calcium indicator.

A cell comprising a heterologous otopetrin polypeptide selected from the group consisting of:

• a mammalian otopetrin polypeptide;
• Otop1;
• Otop2;
• Otop3;
• an insect otopetrin polypeptide;
• and an otopetrin polypeptide that is at least 80% identical, at least 85% identical, at least 90% identical, at least 95% identical, at least 96% identical, at least 97% identical, at least 98% identical, at least 99% identical, or 100% identical to an otopetrin polypeptide sequence of any one of SEQ ID Nos:1-9;
• or a functional portion thereof;
• wherein the cell is:
• a mammalian cell;
• a non-human primate cell;
• an oocyte;
• a HEK-293 cell;
• a CHO cell;
• an insect cell;
• and/or
• a reptilian cell.