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. 2006 Aug 4;103(33):12569–12574. doi: 10.1073/pnas.0602702103

Fig. 4.

Fig. 4.

PKD1L3 and PKD2L1 are stimulated by sour tastants. (A) HEK 293T cells expressing PKD1L3 and PKD2L1 or control pCI vector were stimulated with control buffer or buffer containing 25 mM citric acid. (B) Kinetics of the Fluo-4/Fura red ratio changes for 10 representative cells. (C) PKD1L3 and PKD2L1 respond to citric acid. In contrast, cells expressing PKD1L3 or PKD2L1 alone, or neither, do not respond. Fluorescent ratio of the entire field (≈200 cells) before and after stimulation (±SEM) are shown (n = 3–5). (D) Citric acid and HCl dose responses for PKD1L3 and PKD2L1. Bath solutions containing 5, 10, 15, 20, 25, or 30 mM citric acid (corresponding to pH 3.9, 3.2, 3.0, 2.8, 2.7, or 2.7, respectively) were applied. In addition, HCl at 9, 10, 11, 12, 13, 14, or 15 mM (corresponding to pH 3.3, 3.1, 2.9, 2.8, 2.7, 2.6, or 2.5, respectively) was applied. Normalized fractions of responders (±SEM) are shown (n = 4). (E) PKD1L3 and PKD2L1 do not respond to sweet, bitter, umami, and salty chemicals. Averages of the kinetics of 12–31 representative cells for each ligand are shown. These cells responded to 25 mM citric acid (data not shown). glu+IMP, l-glutamate plus inosine monophosphate; PTC, phenylthiocarbamide; PROP, 6-n-propylthiouracil.