Characterization and Regulation of the Amino Acid Transporter SNAT2 in the Small Intestine of Piglets.

Guangran Li,Jianjun Li,Guiping Guan,Yulong Yin,Bie Tan,Jing Wang,Fengna Li,Xiangfeng Kong,Gudrun A Brockmann

doi:10.1371/journal.pone.0128207

Abstract

The sodium-dependent neutral amino acid transporter 2 (SNAT2), which has dual transport/receptor functions, is well documented in eukaryotes and some mammalian systems, but has not yet been verified in piglets. The objective of this study was to investigate the characteristics and regulation of SNAT2 in the small intestine of piglets. The 1,521-bp porcine full cDNA sequence of SNAT2 (KC769999) from the small intestine of piglets was cloned. The open reading frame of cDNA encodes 506 deduced amino acid residues with a calculated molecular mass of 56.08 kDa and an isoelectric point (pI) of 7.16. Sequence alignment and phylogenetic analysis revealed that SNAT2 is highly evolutionarily conserved in mammals. SNAT2 mRNA can be detected in the duodenum, jejunum and ileum by real-time quantitative PCR. During the suckling period from days 1 to 21, the duodenum had the highest abundance of SNAT2 mRNA among the three segments of the small intestine. There was a significant decrease in the expression of SNAT2 mRNA in the duodenal and jejunal mucosa and in the expression of SNAT2 protein in the jejunal and ileal mucosa on day 1 after weaning (P < 0.05). Studies with enterocytes in vitro showed that amino acid starvation and supplementation with glutamate, arginine or leucine enhanced, while supplementation with glutamine reduced, SNAT2 mRNA expression (P < 0.05). These results regarding the characteristics and regulation of SNAT2 should help to provide some information to further clarify its roles in the absorption of amino acids and signal transduction in the porcine small intestine.

Highlights

In young piglets, the process of weaning may contribute to morphological and functional changes in the small intestine [1]
The open reading frame (ORF) of SLC38A2 from the small intestine of Duroc × (Landrace × Large Yorkshire) piglets was cloned and the sequence was added to GenBank
The ORF of SLC38A2 cDNA of 1,521 bp encoded a protein of 506 residues (Fig 1) with a calculated molecular mass of 56.08 kDa and an isoelectric point of 7.16

Summary

Introduction

The process of weaning may contribute to morphological and functional changes in the small intestine [1]. Dietary amino acids are a major fuel for the small intestinal mucosa and are necessary for maintaining the intestinal mucosal morphology and function in neonatal piglets [4]. Sodium-dependent neutral amino acid transporter 2 (SNAT2, encoded by the gene SLC38A2 (solute carrier family 38, member 2)) exhibits a dual transporter/receptor (“transceptor”) function and has been demonstrated in lower eukaryotes and some mammalian cells [7,8,9]. The aim of the present study was to clone the full sequence of SLC38A2 and explore the distribution and ontogenetic expression of SNAT2 during the suckling and postweaning periods, as well as the effects of substrates on the expression of SNAT2 in the small intestine, which should help to further elucidate the role of SNAT2 in the absorption of amino acids and signal transduction in the porcine small intestine

Objectives

Methods

Results

Conclusion