Search

Paneth cells (PCs), a specialized secretory cell type in the small intestine, are increasingly recognized as having an essential role in host responses to microbiome and environmental stresses. Whether and how commensal and pathogenic microbes modify PC composition to modulate inflammation remain unclear. Using newly developed PC-reporter mice under conventional and gnotobiotic conditions, we determined PC transcriptomic heterogeneity in response to commensal and invasive microbes at single cell level. Infection expands the pool of CD74 + PCs, whose number correlates with auto or allogeneic inflammatory disease progressions in mice. Similar correlation was found in human inflammatory disease tissues. Infection-stimulated cytokines increase production of reactive oxygen species (ROS) and expression of a PC-specific mucosal pentraxin (Mptx2) in activated PCs. A PC-specific ablation of MyD88 reduced CD74 + PC population, thus ameliorating pathogen-induced systemic disease. A similar phenotype was also observed in mice lacking Mptx2. Thus, infection stimulates expansion of a PC subset that influences disease progression., (© 2023 The Authors. Published under the terms of the CC BY NC ND 4.0 license.)

Wntless (Wls) transports Wnt molecules for secretion; however, the cellular mechanism underlying the initial assembly of Wnt secretory vesicles is still not fully defined. Here, we performed proteomic and mutagenic analyses of mammalian Wls, and report a mechanism for formation of early Wnt secretory vesicles on ER membrane. Wls forms a complex with SEC12 (also known as PREB), an ER membrane-localized guanine nucleotide-exchange factor (GEF) activator of the SAR1 (the SAR1A isoform) small GTPase. Compared to palmitoylation-deficient Wnt molecules, binding of mature Wnt to Wls increases Wls-SEC12 interaction and promotes association of Wls with SAR1, the key activator of the COPII machinery. Incorporation of Wls into this exporting ER compartment is affected by Wnt ligand binding and SEC12 binding to Wls, as well as the structural integrity and, potentially, the folding of the cytosolic tail of Wls. In contrast, Wls-SEC12 binding is stable, with the interacting interface biochemically mapped to cytosolic segments of individual proteins. Mutant Wls that fails to communicate with the COPII machinery cannot effectively support Wnt secretion. These data suggest that formation of early Wnt secretory vesicles is carefully regulated to ensure proper export of functional ligands., Competing Interests: Competing interestsThe authors declare no competing or financial interests., (© 2017. Published by The Company of Biologists Ltd.)

The intestinal stem cell fuels the highest rate of tissue turnover in the body and has been implicated in intestinal disease and cancer; understanding the regulatory mechanisms controlling intestinal stem cell physiology is of great importance. Here, we provide evidence that the transcription factor YY1 is essential for intestinal stem cell renewal. We observe that YY1 loss skews normal homeostatic cell turnover, with an increase in proliferating crypt cells and a decrease in their differentiated villous progeny. Increased crypt cell numbers come at the expense of Lgr5(+) stem cells. On YY1 deletion, Lgr5(+) cells accelerate their commitment to the differentiated population, exhibit increased levels of apoptosis, and fail to maintain stem cell renewal. Loss of Yy1 in the intestine is ultimately fatal. Mechanistically, YY1 seems to play a role in stem cell energy metabolism, with mitochondrial complex I genes bound directly by YY1 and their transcript levels decreasing on YY1 loss. These unappreciated YY1 functions broaden our understanding of metabolic regulation in intestinal stem cell homeostasis.