Biology subjects

Lencer, W. I.

Publications and source records attributed to Lencer, W. I..

10 recordsLinked to original sources

bioRxiv2026

Blautia wexlerae Transforms Dietary Fatty Acids to Activate Enteroendocrine Signaling and Improve Metabolic Health in Mice and Humans

Metabolites produced by the gut microbiome influence host metabolic health, but how this occurs remains incompletely defined. Here, we report that a common human gut commensal, Blautia wexlerae, converts dietary fats into bioactive metabolites that induce gut hormone production to affect glucose metabolism and suppress appetite. We found that colonization with Blautia wexlerae correlated with healthier eating behaviors in humans. Blautia wexlerae encodes a unique acyl transferase and is capable of producing acyl amines from nutrient substrates. These Blautia acyl amines stimulated human enteroendocrine cells to secrete GLP-1 and other gut peptide hormones more potently than endogenously produced acyl amines. When fed to mice, acyl amines improved glycemic control and decreased appetite. In humans, higher stool levels of Blautia DNA encoding acyl amine synthesis genes correlated with leanness and decreased dietary fat intake. These results define a mechanism of action for how Blautia wexlerae affects host metabolic control.

microbiology↗

bioRxiv2025

Palmitoylated caveolin-1 enables endosome sorting of complex sphingolipids

Complex sphingolipids form in the Golgi apparatus and require transport by vesicular carriers to reach the plasma membrane (PM) where they assemble with cholesterol to affect membrane function. The caveolin proteins have been implicated in sphingolipid trafficking but by mechanisms unknown. Here, we found that cells lacking caveolin-1 (Cav1) distributed the complex sphingolipids to the lysosome rather than to the PM. This was not seen in Cavin-1 KO cells, implicating a function for Cav1 independent of caveolae. The defect in trafficking localized to the sorting endosome where the complex sphingolipids failed to enter recycling tubules serving the PM. Sphingolipid trafficking was rescued by over-expression of Cav1, but not by a Cav1 mutant that lacked the S-palmitoylation sites. Thus, noncaveolar and palmitoylated Cav1 appears to act as a chaperone, or selectivity filter, enabling entry of the complex sphingolipids into endocytic recycling tubules to shape the composition of the PM.

cell biology↗

bioRxiv2025

Trans-kingdom coupling of redox signaling to environmental cell stress responses through multiphase partitioning.

Reactive Oxygen Species (ROS) signaling is a conserved biological process with parallel functions in all evolutionary branches of life. Here, we identify Receptor for Activated C Kinase 1 (RACK1) as a conserved redox-regulated hub that integrates ROS signals to coordinate cellular stress responses. Using cysteine reactivity profiling in intestinal epithelial cells, we demonstrate that RACK1 undergoes NOX1-dependent oxidation at multiple residues, with C286 serving as a key regulatory site. Functional studies reveal that RACK1 negatively regulates NF{kappa}B signaling through redox-dependent interactions with upstream signaling complexes. Upon stress stimulation, RACK1 dynamically redistributes into membrane-less condensates that act as redox-privileged microenvironments enriched for hydrogen peroxide. We find that oxidized RACK1 condensates are conserved through evolution with analogous stress response behavior in bacteria and yeast indicating a ubiquitous and ancient stress sensor-effector system. Functionally, redox-dependent RACK1 activity links environmental stress to translational control, with oxidation promoting inhibition of protein synthesis. Furthermore, RACK1 mediates responses to diverse pathogen-associated stimuli, including viral and bacterial infection, highlighting its role in epithelial innate immune responses. Collectively, these findings establish RACK1 as a cellular node for redox signaling, operating within condensate-based microdomains to spatially encode oxidative signals and regulate environmental stress pathways in cells. Significance StatementThis study defines a mechanism by which cells achieve specificity in redox signaling through compartmentalization within condensates. By identifying RACK1 as a redox sensor-effector, we reveal an ancient and broadly conserved system linking environmental stress to innate immune signaling and translational control. The discovery of redox-privileged condensates provides a conceptual framework for understanding how transient ROS signals are stabilized and interpreted in epithelial biology, with implications for inflammatory diseases, host-pathogen interactions, and fundamental cellular stress responses.

cell biology↗

bioRxiv2025

TTC7A organizes glandular lumen formation in the intestine through a Class II phosphatidylinositol 3-kinase

The formation of a single central lumen is a critical step for glandular morphogenesis. Patients with loss of function variants in the chaperone protein TTC7A have multiple lumen formation in colonic crypt glands. We show that trafficking and localization of TTC7A to the plasma membrane is required for directionally specifying the apical membrane with TTC7A patient loss-of-function variants leading to mislocalized membrane and lumen formation. Our experiments show that TTC7A, in early stages of apical membrane development, functions as a molecular chaperone for the Class II phosphatidylinositol 3-kinase, PIK3C2A and is trafficked in Rab11a positive vesicles to generate phosphatidylinositol 3,4-bisphosphate (PI(3,4)P2). We show that the apical specification process is dependent on PIK3C2A dependent generation of PI(3,4)P2 in intestinal epithelia and that defective lumen formation can be rescued by exogenous PI(3,4)P2 or small molecules that modulate phosphoinositide homeostasis.

cell biology↗

bioRxiv2023

Bacterial Sphingolipids Exacerbate Colitis by Inhibiting ILC3-derived IL-22 Production.

Commensal bacteria of the Bacteroidetes phylum are the primary producers of sphingolipids in the gut lumen. These lipids serve dual roles as bacterial virulence factors and regulators of the host mucosal immune system, including regulatory T cells and invariant natural killer T cells (iNKT). Sphingolipid composition is significantly altered in fecal samples of patients with inflammatory bowel disease (IBD). However, the specific mechanisms by which bacterial sphingolipids modulate mucosal homeostasis and regulate intestinal inflammation remain unclear. In this study, we investigated the impact of bacterial sphingolipids on intestinal inflammation by mono-colonizing mice with Bacteroides fragilis strains that either express or lack sphingolipids during DSS-induced colitis. We discovered that B. fragilis sphingolipids exacerbate intestinal inflammation. Mice mono-colonized with B. fragilis lacking sphingolipids exhibited less severe DSS-induced colitis. This amelioration of colitis was associated with increased production of interleukin-22 (IL-22) by innate lymphoid cell type 3 (ILC3). Consistent with the inhibitory effect of sphingolipids on IL-22 production, mice colonized with B. fragilis lacking sphingolipids showed enhanced epithelial STAT3 activity, intestinal cell proliferation, and antimicrobial peptide production following DSS treatment compared to those colonized with B. fragilis producing sphingolipids. Additionally, colitis severity in mice colonized with B. fragilis lacking sphingolipids was exacerbated upon IL-22 blockade. Furthermore, our study reveals that bacterial sphingolipids restrict epithelial IL-18 production following DSS treatment and interfere with IL-22 production by a subset of ILC3 cells expressing both the interleukin-18 receptor (IL-18R) and major histocompatibility complex class II (MHC II). These findings indicate that B. fragilis-derived sphingolipids exacerbate mucosal inflammation by impeding epithelial IL-18 expression, resulting in compromised production of IL-22 by ILC3 cells. HighlightsO_LIB. fragilis-derived sphingolipids exacerbate DSS-induced colitis in mono-colonized C57BL/6 mice. C_LIO_LIB. fragilis-derived sphingolipids constrain ILC3-derived IL-22, leading to reduced colonic epithelial cell proliferation and compromised barrier function. C_LIO_LIB. fragilis-derived sphingolipids restrict epithelial NLRC4 inflammasome activation and IL-18 secretion. C_LIO_LIB. fragilis-derived sphingolipids modulate IL-22 production by IL18R+ MHC II+ ILC3s. C_LI

immunology↗

bioRxiv2023

Structural basis for recognition of unfolded proteins by the ER stress sensor ERN1/IRE1α

IRE1 is an endoplasmic reticulum sensor that recognizes misfolded proteins to activate the unfolded protein response (UPR). We used cholera toxin (CTx), which activates IRE1 in cells, to understand how unfolded proteins are recognized. In vitro, the A1 subunit of CTx (CTxA1) bound IRE1 lumenal domain (IRE1LD). Global unfolding was not required. Instead, IRE1LD recognized a 7-residue motif within a metastable region of CTxA1 that was also found in microbial and host proteins involved in IRE1 activation. Binding mapped to a pocket on IRE1LD normally occupied by a segment of the IRE1 C-terminal flexible loop implicated in IRE1 regulation. Mutation of the recognition motif blocked CTx-induced IRE1 activation in live cells. These findings describe a mechanism for substrate recognition by IRE1 that induces the UPR.

cell biology↗

bioRxiv2021

The epithelial-specific ER stress sensor IRE1β enables host-microbiota crosstalk to affect colon goblet cell development

Epithelial cells lining mucosal surfaces of the gastrointestinal and respiratory tracts uniquely express IRE1{beta} (Ern2), a paralogue of the most evolutionarily conserved endoplasmic reticulum stress sensor IRE1. How IRE1{beta} functions at the host-environment interface and why a second IRE1 paralogue evolved remain incompletely understood. Using conventionally raised and germ-free Ern2-/- mice, we found that IRE1{beta} was required for microbiota-induced goblet cell maturation and mucus barrier assembly in the colon. This occurred only after colonization of the alimentary tract with normal gut microflora, which induced IRE1{beta} expression. IRE1{beta} acted by splicing Xbp1 mRNA to expand ER function and prevent ER stress in goblet cells. Although IRE1 can also splice Xbp1 mRNA, it did not act redundantly to IRE1{beta} in this context. By regulating assembly of the colon mucus layer, IRE1{beta} further shaped the composition of the gut microbiota. Mice lacking IRE1{beta} had a dysbiotic microbial community that failed to induce goblet cell development when transferred into germ-free wild type mice. These results show that IRE1{beta} evolved at mucosal surfaces to mediate crosstalk between gut microbes and the colonic epithelium required for normal homeostasis and host defense.

cell biology↗

bioRxiv2021

Structural basis for acyl chain control over glycosphingolipid sorting and vesicular trafficking

The complex sphingolipids exhibit a diversity of ceramide acyl chain structures that influence their trafficking and intracellular distributions, but how the cell discerns among the different ceramides to affect such sorting remains unknown. To address mechanism, we synthesized a library of GM1 glycosphingolipids with naturally varied acyl chains and quantitatively assessed their sorting among different endocytic pathways. We found that a stretch of at least 14 saturated carbons extending from C1 at the water-bilayer interface dictated lysosomal sorting by exclusion from endosome sorting tubules. Sorting to the lysosome by the C14*-motif was cholesterol dependent. Perturbations of the C14*-motif by unsaturation enabled GM1 entry into endosomal sorting tubules of the recycling and retrograde pathways independently of cholesterol. Unsaturation occurring beyond the C14*-motif in very long acyl chains rescued lysosomal sorting. These results define a structural motif underlying membrane organization of sphingolipids and implicate cholesterol-sphingolipid nanodomain formation in sorting mechanisms.

cell biology↗

bioRxiv2020

Structured clustering of the glycosphingolipid GM1 is required for membrane curvature induced by cholera toxin

AB5 bacterial toxins and polyomaviruses induce membrane curvature as a mechanism to facilitate their entry into host cells. How membrane bending is accomplished is not yet fully understood but has been linked to the simultaneous binding of the pentameric B-subunit to multiple copies of their glycosphingolipid receptors. Here, we probe the toxin membrane binding and internalization mechanisms by using a combination of super-resolution and polarized localization microscopy. We show that cholera toxin subunit B (CTxB) can induce membrane curvature only when bound to multiple copies of its glycosphingolipid receptor, GM1, and the ceramide structure of GM1 is likely not a determinant of this activity as assessed in model membranes. A mutant CTxB capable of binding only a single GM1 fails to generate curvature either in model membranes or in cells and clustering the mutant CTxB-single-GM1 complexes by antibody cross-linking does not rescue the membrane curvature phenotype. We conclude that both the multiplicity and specific geometry of GM1 binding sites are necessary for the induction of membrane curvature. We expect this to be a general rule of membrane behavior for all AB5 toxins and polyomaviruses that bind glycosphingolipids to invade host cells. SIGNIFICANCE STATEMENTMembrane binding toxins demonstrate both a public health challenge and a bioengineering opportunity due to their efficient internalization into cells. These toxins multivalently bind to naturally occurring lipid receptors at the plasma membrane and initiate endocytosis. This manuscript reports the importance of structured lipid-receptor clustering for the induction of membrane bending. We also observed that the magnitude of membrane curvature was correlated to the stoichiometry of toxin-bound receptors. By identifying how these bacterial proteins initiate membrane curvature, these findings provide mechanistic insights into the early steps of pathogenic endocytosis.

biophysics↗

bioRxiv2019

IRE1β negatively regulates IRE1α signaling in response to endoplasmic reticulum stress

IRE1{beta} is an ER stress sensor uniquely expressed in epithelial cells lining mucosal surfaces. Here, we show that intestinal epithelial cells expressing IRE1{beta} have an attenuated response to ER stress. IRE1{beta} assembles with and blocks activation of the closely related and most evolutionarily ancient stress-sensor IRE1 to suppress stress-induced xbp1 splicing, a key mediator of the unfolded protein response. In comparison, IRE1{beta} has weak xbp1 splicing activity, largely explained by a non-conserved amino acid in the kinase domain that impairs its phosphorylation and restricts oligomerization. This enables IRE1{beta} to act as a dominant negative suppressor of IRE1. The inhibitory effect is amplified in cells by disrupting an XBP1-dependent feedback loop regulating stress-induced expression of IRE1. Thus IRE1{beta} functions to negatively regulate IRE1 signaling, perhaps enabling intestinal epithelial cells to manage the response to chronic stress stimuli at the host-environment interface.

cell biology↗