Abstract
Firstly, our research group identified Sutai pigs’ phenotypes that exhibited extreme resistance and susceptibility to the Escherichia coli F18 respectively, and then eight ETEC (Enterotoxigenic Escherichia coli) F18-resistant piglets and eight ETEC F18-sensitive piglets were selected. Then, the TAP1 (Transporter associated with antigen processing) mRNA relative expression levels were analyzed in 11 tissues of the resistant and susceptible phenotypes. Simultaneously, we detected the genetic variations in exon 3 of the TAP1 gene and evaluated the TAP1 mRNA expression levels among the different genotype pigs to study the effects of the genetic variation on gene expression, and the E. coli F18 resistance. The results revealed higher expression levels in the resistant genotypes than that in the susceptible genotypes in 11 tissues, with significant differences in the spleen, lymph node, lung, thymus, duodenum and jejunum. Furthermore, a G729A mutation was identified in the TAP1 gene exon 3, and this mutation deviates from Hardy-Weinberg equilibrium (p < 0.01). The TAP1 mRNA levels in GG genotype were significantly higher than that in the other two genotypes, with significant differences in the liver, lung, kidney, thymus, lymph node, duodenum and jejunum tissues. We speculated that high expression of the TAP1 gene might confer resistance against the E. coli F18, the G729A mutation had a significant effect on the mRNA expression, and individuals with the GG genotype possessed a stronger ability to resist the E. coli F18 infection.
Highlights
Transporter associated with antigen processing (TAP) is a protein transporter that consists of two protein subunits, TAP1 and TAP2
The adherence assay showed that small intestinal epithelial cells from eight ETEC F18-resistant piglets in this experiment displayed nearly no adherence with E.coli bacteria
There were significant differences in the spleen, lymph node, lung, thymus, jejunum, and duodenum between the resistant and susceptible genotypes (p < 0.05). These results indicated that the higher mRNA expression level might confer resistance to pathogenic infection
Summary
Transporter associated with antigen processing (TAP) is a protein transporter that consists of two protein subunits, TAP1 and TAP2. Both these subunits have an N-terminal membrane-spanning domain and a C-terminal nucleotide-binding domain, and together they form a heterodimer that plays a pivotal role in intracellular antigen presentation by translocating intracellular antigenic peptides from the cytosol into the lumen of the endoplasmic reticulum (ER) [1]. TAP1 is responsible for the transport of peptides generated by proteasomal degradation to the ER lumen, after which they are transported to the cell surface in conjunction with MHC class I molecules, inducing specific recognition and processing by. MHC class I molecules require TAP1 to overcome their structural instability during maturation and transportation.
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