Fucosylated glycoproteins and fucosylated glycolipids play opposing roles in cholera intoxication.

Cholera toxin (CT) is the etiological agent of cholera. Here we report that multiple classes of fucosylated glycoconjugates function in CT binding and intoxication of intestinal epithelial cells. In Colo205 cells, knockout of B3GNT5, the enzyme required for synthesis of lacto- and neolacto-series glycosphingolipids (GSLs), reduces CT binding but sensitizes cells to intoxication. Overexpressing B3GNT5 to generate more fucosylated GSLs confers protection against intoxication, indicating that fucosylated GSLs act as decoy receptors for CT. Knockout (KO) of B3GALT5 causes increased production of fucosylated O-linked and N-linked glycoproteins, and leads to increased CT binding and intoxication. Knockout of B3GNT5 in B3GALT5 KO cells eliminates production of fucosylated GSLs but increases intoxication, identifying fucosylated glycoproteins as functional receptors for CT. These findings provide insight into molecular determinants regulating CT sensitivity of host cells.

Loss of heat shock factor initiates intracellular lipid surveillance by actin destabilization.

Cells sense stress and initiate response pathways to maintain lipid and protein homeostasis. However, the interplay between these adaptive mechanisms is unclear. Herein, we demonstrate how imbalances in cytosolic protein homeostasis affect intracellular lipid surveillance. Independent of its ancient thermo-protective properties, the heat shock factor, HSF-1, modulates lipid metabolism and age regulation through the metazoan-specific nuclear hormone receptor, NHR-49. Reduced hsf-1 expression destabilizes the Caenorhabditis elegans enteric actin network, subsequently disrupting Rab GTPase-mediated trafficking and cell-surface residency of nutrient transporters. The ensuing malabsorption limits lipid availability, thereby activating the intracellular lipid surveillance response through vesicular release and nuclear translocation of NHR-49 to both increase nutrient absorption and restore lipid homeostasis. Overall, cooperation between these regulators of cytosolic protein homeostasis and lipid surveillance ensures metabolic health and age progression through actin integrity, endocytic recycling, and lipid sensing.

Age-Onset Phosphorylation of a Minor Actin Variant Promotes Intestinal Barrier Dysfunction.

Age-associated decay of intercellular interactions impairs the cells' capacity to tightly associate within tissues and form a functional barrier. This barrier dysfunction compromises organ physiology and contributes to systemic failure. The actin cytoskeleton represents a key determinant in maintaining tissue architecture. Yet, it is unclear how age disrupts the actin cytoskeleton and how this, in turn, promotes mortality. Here, we show that an uncharacterized phosphorylation of a low-abundant actin variant, ACT-5, compromises integrity of the C. elegans intestinal barrier and accelerates pathogenesis. Age-related loss of the heat-shock transcription factor, HSF-1, disrupts the JUN kinase and protein phosphatase I equilibrium which increases ACT-5 phosphorylation within its troponin binding site. Phosphorylated ACT-5 accelerates decay of the intestinal subapical terminal web and impairs its interactions with cell junctions. This compromises barrier integrity, promotes pathogenesis, and drives mortality. Thus, we provide the molecular mechanism by which age-associated loss of specialized actin networks impacts tissue integrity.