Intestinal amino acid availability via PEPT-1 affects TORC1/2 signaling and the unfolded protein response

J Proteome Res. 2014 Aug 1;13(8):3685-92. doi: 10.1021/pr5002669. Epub 2014 Jul 16.

Abstract

The intestinal peptide transporter PEPT-1 plays an important role in development, growth, reproduction, and stress tolerance in Caenorhabditis elegans, as revealed by the severe phenotype of the pept-1-deficient strain. The reduced number of offspring and increased stress resistance were shown to result from changes in the insulin/IGF-signaling cascade. To further elucidate the regulatory network behind the phenotypic alterations in PEPT1-deficient animals, a quantitative proteome analysis combined with transcriptome profiling was applied. Various target genes of XBP-1, the major mediator of the unfolded protein response, were found to be downregulated at the mRNA and protein levels, accompanied by a reduction of spliced xbp-1 mRNA. Proteome analysis also revealed a markedly reduced content of numerous ribosomal proteins. This was associated with a reduction in the protein synthesis rate in pept-1 C. elegans, a process that is strictly regulated by the TOR (target of rapamycine) complex, the cellular sensor for free amino acids. These data argue for a central role of PEPT-1 in cellular amino acid homeostasis. In PEPT-1 deficiency, amino acid levels dropped systematically, leading to alterations in protein synthesis and in the IRE-1/XBP-1 pathway.

MeSH terms

  • ATP-Binding Cassette Transporters / genetics*
  • ATP-Binding Cassette Transporters / metabolism
  • Amino Acids / analysis*
  • Animals
  • Blotting, Western
  • Caenorhabditis elegans
  • Caenorhabditis elegans Proteins / genetics*
  • Caenorhabditis elegans Proteins / metabolism*
  • Carrier Proteins / genetics
  • Carrier Proteins / metabolism*
  • DNA Primers / genetics
  • Gene Expression Profiling
  • Gene Expression Regulation / genetics
  • Gene Expression Regulation / physiology*
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2
  • Multiprotein Complexes / metabolism
  • Proteomics
  • Reverse Transcriptase Polymerase Chain Reaction
  • Signal Transduction / genetics*
  • TOR Serine-Threonine Kinases / metabolism
  • Unfolded Protein Response / genetics
  • Unfolded Protein Response / physiology*

Substances

  • ATP-Binding Cassette Transporters
  • Amino Acids
  • Caenorhabditis elegans Proteins
  • Carrier Proteins
  • DNA Primers
  • Multiprotein Complexes
  • XBP-1 protein, C elegans
  • pept-1 protein, C elegans
  • TOR Serine-Threonine Kinases
  • Mechanistic Target of Rapamycin Complex 1
  • Mechanistic Target of Rapamycin Complex 2