Fig. 5.

Interaction of piperidine carboxylates with PAT2. Representative current traces using PAT2-expressing and water-injected oocytes during exposure to glycine (Gly, 0.3 or 10 mM) and/or: A. l-pipecolic acid (l-Pip); B. d-pipecolic acid (d-Pip), nipecotic acid (Nip), isonipecotic acid (Isonip) (all 10 mM). C. Mean PAT2-specific current observed in parts A–B. Data represent the relative change in current observed when glycine (+ Gly), isonipecotic acid (+ Isonip), nipecotic acid (+ Nip), d-pipecolic acid (+ d-Pip) or l-pipecolic acid (+ l-Pip) (all 10 mM) are added to the superfusate in the continued presence of 0.3 mM glycine (control). Results are expressed as the fold change in current relative to that caused by 0.3 mM glycine. Data for glycine (n = 10) and l-pipecolic acid (n = 5) are mean ± SEM, and for isonipecotic acid, nipecotic acid and d-pipecolic acid are mean ± SD (n = 3). **, p < 0.01; *, p < 0.05; ns, p > 0.05, versus the current observed in the presence of 0.3 mM glycine (paired, two-tailed Student's t-test). D. Representative current traces using PAT2-expressing or water-injected oocytes during exposure to a saturating concentration (3 mM) of glycine (Gly) in the presence and absence of 10 mM l-pipecolic acid (l-Pip). E. Mean data for part D showing PAT2-specific current. Data are mean ± SEM (n = 4). **, p < 0.01; *, p < 0.05, versus the current observed in the presence of 3 mM glycine alone. F. [³H]Glycine (filled squares) and l-[³H]pipecolic acid (open squares) (both 0.01–10 mM) uptake (pH 5.5, Na⁺-free) in PAT2-expressing oocytes. Results are expressed as PAT2-specific uptake (following subtraction of uptake in water-injected oocytes). Data are mean ± SEM (n = 10). G. pH-Dependent [³H]glycine (filled squares) and l-[³H]pipecolic acid (open squares) (both 10 μM) uptake in PAT2-expressing oocytes at extracellular pH 5.5–8.0 (Na⁺-free). Results are expressed as PAT2-specific uptake. Data are mean ± SEM (n = 9–10).