SLC15 family of peptide transporters in GtoPdb v.2021.3

The Solute Carrier 15 (SLC15) family of peptide transporters, alias H+-coupled oligopeptide cotransporter family, is a group of membrane transporters known for their key role in the cellular uptake of di- and tripeptides (di/tripeptides). Of its members, SLC15A1 (PEPT1) chiefly mediates intestinal absorption of luminal di/tripeptides from overall dietary protein digestion, SLC15A2 (PEPT2) mainly allows renal tubular reuptake of di/tripeptides from ultrafiltration and brain-to-blood efflux of di/tripeptides in the choroid plexus, SLC15A3 (PHT2) and SLC15A4 (PHT1) interact with both di/tripeptides and histidine, e.g. in certain immune cells, and SLC15A5 has unknown physiological function. In addition, the SLC15 family of peptide transporters variably interacts with a very large number of peptidomimetics and peptide-like drugs. It is conceivable, based on the currently acknowledged structural and functional differences, to divide the SLC15 family of peptide transporters into two subfamilies [3].

Growth Hormone Overexpression Induces Hyperphagia and Intestinal Morphophysiological Adaptations to Improve Nutrient Uptake in Zebrafish

Graphical AbstractGH overexpression increases the intestinal mass and absorptive surface area both through the direct effects of GH transgenics (up-regulating the expression of its cognate receptor and insulin-like growth factor, igf1a) and through indirect effects through an increase in the amount of food consumed. In addition, hyperphagia provides a greater amount of nutrients in the intestinal lumen and stimulates the synthesis of di- and tri-peptide transporters, which are the main route of absorption of dietary products from protein degradation.

Effects of Short-Term Fasting on mRNA Expression of Ghrelin and the Peptide Transporters PepT1 and 2 in Atlantic Salmon (Salmo salar)

Food intake is a vital process that supplies necessary energy and essential nutrients to the body. Information regarding luminal composition in the gastrointestinal tract (GIT) collected through mechanical and nutrient sensing mechanisms are generally conveyed, in both mammals and fish, to the hypothalamic neurocircuits. In this context, ghrelin, the only known hormone with an orexigenic action, and the intestinal peptide transporters 1 and 2, involved in absorption of dietary di- and tripeptides, exert important and also integrated roles for the nutrient uptake. Together, both are potentially involved in signaling pathways that control food intake originating from different segments of the GIT. However, little is known about the role of different paralogs and their response to fasting. Therefore, after 3 weeks of acclimatization, 12 Atlantic salmon (Salmo salar) post-smolt were fasted for 4 days to explore the gastrointestinal response in comparison with fed control (n = 12). The analysis covered morphometric (weight, length, condition factor, and wet content/weight fish %), molecular (gene expression variations), and correlation analyses. Such short-term fasting is a common and recommended practice used prior to any handling in commercial culture of the species. There were no statistical differences in length and weight but a significant lower condition factor in the fasted group. Transcriptional analysis along the gastrointestinal segments revealed a tendency of downregulation for both paralogous genes slc15a1a and slc15a1b and with significant lowered levels in the pyloric ceca for slc15a1a and in the pyloric ceca and midgut for slc15a1b. No differences were found for slc15a2a and slc15a2b (except a higher expression of the fasted group in the anterior midgut), supporting different roles for slc15 paralogs. This represents the first report on the effects of fasting on slc15a2 expressed in GIT in teleosts. Transcriptional analysis of ghrelin splicing variants (ghrl-1 and ghrl-2) showed no difference between treatments. However, correlation analysis showed that the mRNA expression for all genes (restricted to segment with the highest levels) were affected by the residual luminal content. Overall, the results show minimal effects of 4 days of induced fasting in Atlantic salmon, suggesting that more time is needed to initiate a large GIT response.

NPF genes excavation and their expression response to vernalization and nitrogen deficiency in allotetraploid rapeseed

Background The NITRATE TRANSPORTER 1/PEPTIDE TRANSPORTER FAMILY (NPF) genes, initially characterized as nitrate or peptide transporters in plants, involve in the transport of a large variety of substrates including amino acids, nitrate, auxin (IAA), jasmonates (JAs), abscisic acid (ABA) and gibberellins (GAs) and glucosinolates. The evolution and expression diversification of genes determine their functional differentiation in polyploid species. Results Among 169 NPF genes excavated in Brassica napus, 97 B. napus NPF (BnaNPF) genes evolved from B. rapa, and 72 BnaNPF genes from B. olereaca. They unevenly distributed on B. napus genome and exhibited obvious synteny with NPF genes in Arabidopsis thaliana, B. rapa and B. olereaca. BnaNPF genes were identified to show diversified expression patterns in 90 different organs or tissues based on transcriptome profile data. Besides, they exhibited complex expression changes in the development process of leaves, silique wall and seeds, which indicated that the expression of BnaNPF genes maybe respond to altered phytohormone and secondary metabolite content through combining with promoter elements enrichment analysis. Furthermore, many BnaNPF genes were detected to response to vernalization with two different patterns and 20 BnaNPF genes responded to nitrate deficiency. Conclusion The evolution of BnaNPF genes and their expression pattern including response to vernalization and nitrogen deficiency were characterized and provide valuable information for further functional characterization in rapeseed.

Regulation of Probiotics on Metabolism of Dietary Protein in Intestine

Proteins are indispensable components of living organisms, which are derived mainly from diet through metabolism. Dietary proteins are degraded by endogenous digestive enzymes to di- or tripeptides and free amino acids (AAs) in the small intestine lumen and then absorbed into blood and lymph through intestinal epithelial cells via diverse transporters. Microorganisms are involved not only in the proteins’ catabolism, but also the AAs, especially essential AAs, anabolism. Probiotics regulate these processes by providing exogenous proteases and AAs and peptide transporters, and reducing hazardous substances in the food and feed. But the core mechanism is modulating of the composition of intestinal microorganisms through their colonization and exclusion of pathogens. The other effects of probiotics are associated with normal intestinal morphology, which implies that the enterocytes secrete more enzymes to decompose dietary proteins and absorb more nutrients.

An opaque cell-specific expression program of secreted proteases and transporters allows cell-type cooperation in Candida albicans

An unusual feature of the opportunistic pathogen C. albicans is its ability to stochastically switch between two distinct, heritable cell types called white and opaque. Here, we show that only opaque cells, in response to environmental signals, massively up-regulate a specific group of secreted proteases and peptide transporters, allowing exceptionally efficient use of proteins as sources of nitrogen. We identify the specific proteases (members of the secreted aspartyl protease (SAP) family) needed for opaque cells to proliferate under these conditions, and we identify four transcriptional regulators of this specialized proteolysis and uptake program. We also show that, in mixed cultures, opaque cells enable white cells to also proliferate efficiently when proteins are the sole nitrogen source. Based on these observations, we suggest that one role of white-opaque switching is to create mixed populations where the different phenotypes derived from a single genome are shared between two distinct cell types.SummaryThe opportunistic human fungal pathogen Candida albicans switches between two distinct, heritable cell types, named “white” and “opaque.” We show that opaque cells, in response to proteins as the sole nitrogen source, up-regulate a specialized program, including specific secreted aspartyl proteases and peptide transporters. We demonstrate that, in mixed cultures, opaque cells enable white cells to respond and proliferate more efficiently under these conditions. These observations suggest that white-opaque switching creates mixtures of cells where the population characteristics - which derive from a single genome - reflect the contributions of two distinct cell types.Dataset Reference NumbersThe .RAW files for both sets of Mass Spectrometry experiments have been deposited at the ProteoSAFe resource (https://proteomics.ucsd.edu/ProteoSAFe/).MSP-MS experiment reference number: MSV000085279. For reviewer access use login “MSV000085279_reviewer” and password “candidamspms”.Proteomics experiment reference number: MSV000085283. For reviewer access use login “MSV000085283_reviewer” and password “candidaprot”.