The Solute Carrier 15 (SLC15) family includes H+-coupled membrane transporters known for their role in the cellular uptake/reuptake of di/tripeptides and peptidomimetic molecules. Among its members, SLC15A1 (PepT1) mediates intestinal absorption by transporting luminal di/tripeptides with an electrogenic process that follows Michaelis Menten kinetics. Due to the teleost specific whole-genome duplication event, two pept1 paralogues pept1b and pept1a, are found in the genome of teleost species. The function of PepT1b transporters is known in several teleosts, including zebrafish (Danio rerio) and Atlantic salmon (Salmo salar). In this study, we functionally characterized zebrafish PepT1a (zfPepT1a) and salmon PepT1a (asPepT1a) to gain insights into their role in animal nutrition. Their function, measured as the current elicited in the presence of substrates, were recorded using Two-Electrode Voltage-Clamp technique after heterologous expression in Xenopus laevis oocytes. For both PepT1a transporters, the Gly-Gln transport followed Michaelis Menten type saturation kinetics with apparent affinity (1/K0.5) and maximal relative current (Imax) values differently affected by membrane potential and external pH. Regarding Imax, the asPepT1a was only slightly affected by pH, whereas zfPepT1a showed a larger increase at pH 7.6 than pH 6.5 similarly to zfPepT1b. For all transporters (PepT1a and b of zebrafish and salmon), the K0.5 was in the hundreds of micromolar range and only slightly voltage-dependent at pH 6.5. At pH 7.6, all transporters K0.5 values increased to millimolar range, but only PepT1a was strongly voltage-dependent. A clear different substrate preference between PepT1a and b was highlighted when testing charged substrates (Gly-Lys, Lys-Gly, Met-Lys, Lys-Met, Gly-Asp and Asp-Gly). Our data supports the hypothesis that PepT1a and PepT1b have distinct roles in intestinal peptide recognition and transport.
A comparative electrophysiological characterization of Slc15a1 transporters, PepT1a and PepT1b, of two teleost fishes
Vacca F;Barca A;Verri T;
2019-01-01
Abstract
The Solute Carrier 15 (SLC15) family includes H+-coupled membrane transporters known for their role in the cellular uptake/reuptake of di/tripeptides and peptidomimetic molecules. Among its members, SLC15A1 (PepT1) mediates intestinal absorption by transporting luminal di/tripeptides with an electrogenic process that follows Michaelis Menten kinetics. Due to the teleost specific whole-genome duplication event, two pept1 paralogues pept1b and pept1a, are found in the genome of teleost species. The function of PepT1b transporters is known in several teleosts, including zebrafish (Danio rerio) and Atlantic salmon (Salmo salar). In this study, we functionally characterized zebrafish PepT1a (zfPepT1a) and salmon PepT1a (asPepT1a) to gain insights into their role in animal nutrition. Their function, measured as the current elicited in the presence of substrates, were recorded using Two-Electrode Voltage-Clamp technique after heterologous expression in Xenopus laevis oocytes. For both PepT1a transporters, the Gly-Gln transport followed Michaelis Menten type saturation kinetics with apparent affinity (1/K0.5) and maximal relative current (Imax) values differently affected by membrane potential and external pH. Regarding Imax, the asPepT1a was only slightly affected by pH, whereas zfPepT1a showed a larger increase at pH 7.6 than pH 6.5 similarly to zfPepT1b. For all transporters (PepT1a and b of zebrafish and salmon), the K0.5 was in the hundreds of micromolar range and only slightly voltage-dependent at pH 6.5. At pH 7.6, all transporters K0.5 values increased to millimolar range, but only PepT1a was strongly voltage-dependent. A clear different substrate preference between PepT1a and b was highlighted when testing charged substrates (Gly-Lys, Lys-Gly, Met-Lys, Lys-Met, Gly-Asp and Asp-Gly). Our data supports the hypothesis that PepT1a and PepT1b have distinct roles in intestinal peptide recognition and transport.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
