Embigin is a fibronectin receptor that affects sebaceous gland differentiation and metabolism

Stem cell renewal and differentiation are regulated by interactions with the niche. Although multiple cell populations have been identified in distinct anatomical compartments, little is known about niche-specific molecular factors. Using skin as a model system and combining single-cell RNA-seq data analysis, immunofluorescence, and transgenic mouse models, we show that the transmembrane protein embigin is specifically expressed in the sebaceous gland and that the number of embigin-expressing cells is negatively regulated by Wnt. The loss of embigin promotes exit from the progenitor compartment and progression toward differentiation, and also compromises lipid metabolism. Embigin modulates sebaceous niche architecture by affecting extracellular matrix organization and basolateral targeting of monocarboxylate transport. We discover through ligand screening that embigin is a direct fibronectin receptor, binding to the N-terminal fibronectin domain without impairing integrin function. Our results solve the long-standing question of how embigin regulates cell adhesion and demonstrate a mechanism that couples adhesion and metabolism.</p

Tannins Can Have Direct Interactions with Anthelmintics: Investigations by Isothermal Titration Calorimetry

Plant tannins are known for their anthelmintic and antiparasitic activities and have been increasingly studied to battle the ever-growing problem of anthelmintic resistance. While tannins have been shown to exhibit these activities on their own, one approach would be to use them as complementary nutrients alongside commercial anthelmintics. So far, research on the interactions between tannins and anthelmintics is limited, and few studies have reported both synergistic and antagonistic effects depending on the type of tannin and the method used. These interactions could either strengthen or weaken the efficacy of commercial anthelmintics, especially if tannin-rich diets are combined with anthelmintics used as oral drenches. To study these interactions, a series of hydrolysable tannins (HTs) was selected, and their direct interactions with thiabendazole (TBZ) were evaluated by isothermal titration calorimetry (ITC), which allowed the detection of the exothermic interaction but also the roles and significances of different structural features of HTs in these interactions. Our results show that HTs can have a direct interaction with the benzimidazole anthelmintic TBZ and that the interaction is strengthened by increasing the number of free galloyl groups and the overall molecular flexibility of HTs

Early Chordate Origin of the Vertebrate Integrin αI Domains

<div><p>Half of the 18 human integrins α subunits have an inserted αI domain yet none have been observed in species that have diverged prior to the appearance of the urochordates (ascidians). The urochordate integrin αI domains are not human orthologues but paralogues, but orthologues of human αI domains extend throughout later-diverging vertebrates and are observed in the bony fish with duplicate isoforms. Here, we report evidence for orthologues of human integrins with αI domains in the agnathostomes (jawless vertebrates) and later diverging species. Sequence comparisons, phylogenetic analyses and molecular modeling show that one nearly full-length sequence from lamprey and two additional fragments include the entire integrin αI domain region, have the hallmarks of collagen-binding integrin αI domains, and we show that the corresponding recombinant proteins recognize the collagen GFOGER motifs in a metal dependent manner, unlike the α1I domain of the ascidian <i>C. intestinalis</i>. The presence of a functional collagen receptor integrin αI domain supports the origin of orthologues of the human integrins with αI domains prior to the earliest diverging extant vertebrates, a domain that has been conserved and diversified throughout the vertebrate lineage.</p></div

Multivariate plots reflect the details of the phylogenetic analyses.

<p>(A) Full-length sequences of the integrin α subunit, (B) sequence regions shared in common with Pma_f1-3, and (C) the αI domain region. The plots were based on distances (JTT scoring) obtained from the sequence alignments. The plots show the relationships among the sequences for the three most informative dimensions and the percentage variance accounted for along the axis is indicated.</p

Binding of Pma_f αI domains to rat collagen I as a function of the concentration of Pma_f αI.

<p>(A–C) Binding affinities of Pma_f αI domains to rat collagen I were estimated by fitting binding data using a hyperbolic function, which is identical to Hill's equation when h = 1. BSA was used as a control.</p

Key features of the integrin αI domain.

<p>(A) Alignment of representative sequences, including the three sea lamprey fragments, one short EST fragment derived from the inshore hagfish genome, and four sequences from the elephant shark genome (highlighted in bold). The residues DxSxS…D…T of MIDAS (in bold) function to bind directly or via water molecules to the metal ion where natural ligands bind via a glutamate residue. The sequence ESH (bold) is characteristic of collagen-binding αI domains; the αC helix (bold) is a distinctive hallmark of the collagen receptor α subunits. The intrinsic glutamate ligand (bold) of the αI domain binds to MIDAS of the βI-like domain in integrins that have the inserted αI domain. Structure of the α2I domain without (B) (PDB code: 1AOX; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112064#pone.0112064-Emsley1" target="_blank">[14]</a>) and with (C) bound GFOGER tripeptide (PDB code: 1DZI; <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0112064#pone.0112064-Emsley2" target="_blank">[15]</a>). The peptide binds to the metal (yellow sphere) at MIDAS via glutamate E11 of the peptide. Consequently, the αC helix unravels and the α6 helix lengthens.</p

Summary of integrin evolution across a broad range of species: αI domain specialization, as seen in humans, is a vertebrate invention.

<p>Individual domains having the same fold class as integrin component domains (i.e. β propeller, immunoglobulin fold, epidermal growth factor fold, vWFA) are observed already in prokaryotes but the earliest diverging sets of identifiable integrin subunits have been observed in the choanozoan <i>C. owczarzaki</i>, a single-cell eukaryote. The number of α and β subunits expands with increasing organismal complexity with 18 α and 8 β subunits forming up to 24 heterodimers in humans. Integrins undergo considerable functional diversification with the introduction of the αI domain in some α subunits. Tunicates like <i>C. intestinalis</i> and <i>H. roretzi</i> are the earliest diverging organisms where integrins with αI domains have been identified, but they are not direct vertebrate orthologues as they form a distinct clade. αI domain containing fragments can be detected in the lamprey <i>P. marinus</i> and possibly the hagfish <i>E. burgeri</i>; both are extant representatives of the first vertebrates. The lamprey fragments share characteristic features in common with the human collagen-binding αI domain group and they bind different mammalian collagens at MIDAS; four shark sequences are orthologues of the corresponding human α subunits, three collagen binding and one from the leukocyte clade, and duplicate isoforms are observed in observed in bony fish e.g. <i>D. rerio</i>, <i>C. carpio</i> and <i>O. niloticus</i>.</p