Fig. 2.

Interaction of proline derivatives with the amino acid transporter PAT2. A. l-[³H]Proline (100 μM) uptake (pH 5.5, Na⁺-free, 40 min) in PAT2-expressing oocytes in the absence (control) and presence of unlabelled proline (Pro) or related derivatives (all 10 mM), l-thiaproline (TCA), trans-4-hydroxy-l-proline (T4HP), 3,4-dehydro-d,l-proline (DHP), cis-4-hydroxy-d-proline (CHDP), trans-3-hydroxy-l-proline (T3HP) and cis-4-hydroxy-l-proline (CHLP). Results are expressed as PAT2-specific uptake (following subtraction of uptake in water-injected oocytes under identical experimental conditions). Data are mean ± SEM (n = 28–30). ***, p < 0.001; *, p < 0.05, versus control. B. Concentration-dependent inhibition of PAT2-mediated l-[³H]proline uptake (as in A above) by trans-4-hydroxy-l-proline (T4HP, filled squares, n = 20), trans-3-hydroxy-l-proline (T3HP, open squares, n = 7), and cis-4-hydroxy-l-proline (CHLP, filled triangles, n = 19) (all 0.01–20 mM). Results are expressed as a percentage of the uptake in the absence of inhibitor (after subtraction of uptake in water-injected oocytes). Data are mean ± SEM. C. Representative current traces from PAT2-expressing and water-injected oocytes upon exposure to proline and related derivatives (all 10 mM) measured by TEVC. D. Mean data for part C showing PAT2-mediated current (following subtraction of current induced in water-injected oocytes) evoked by proline and related derivatives. Data are mean ± SEM (n = 4–5). ***, p < 0.001; *, p < 0.05; ns, p > 0.05, versus current change in water-injected oocytes.