Caenorhabditis elegans ortholog of the p24/p22 subunit, DNC-3, is essential for the formation of the dynactin complex by bridging DNC-1/p150Glued and DNC-2/dynamitin

Dynactin is a multisubunit protein complex required for the activity of cytoplasmic dynein. In Caenorhabditis elegans, although 10 of the 11 dynactin subunits were identified based on the sequence similarities to their orthologs, the p24/p22 subunit has not been detected in the genome. Here, we demonstrate that DNC-3 (W10G11.20) is the functional counterpart of the p24/p22 subunit in C. elegans. RNAi phenotypes and subcellular localization of DNC-3 in early C. elegans embryos were nearly identical to those of the known dynactin components. All other dynactin subunits were co-immunoprecipitated with DNC-3, indicating that DNC-3 is a core component of dynactin. Furthermore, the overall secondary structure of DNC-3 resembles to those of the mammalian and yeast p24/p22. We found that DNC-3 is required for the localization of the DNC-1/p150Glued and DNC-2/dynamitin, the two components of the projection arm of dynactin, to the nuclear envelope of meiotic nuclei in the adult gonad. Moreover, DNC-3 physically interacted with DNC-1 and DNC-2 and significantly enhanced the binding ability between DNC-1 and DNC-2 in vitro. These results suggest that DNC-3 is essential for the formation of the projection arm subcomplex of dynactin

Notum produced by Paneth cells attenuates regeneration of aged intestinal epithelium

A decline in stem cell function impairs tissue regeneration during ageing, but the role of the stem-cell-supporting niche in ageing is not well understood. The small intestine is maintained by actively cycling intestinal stem cells that are regulated by the Paneth cell niche(1,2). Here we show that the regenerative potential of human and mouse intestinal epithelium diminishes with age owing to defects in both stem cells and their niche. The functional decline was caused by a decrease in stemness-maintaining Wnt signalling due to production of Notum, an extracellular Wnt inhibitor, in aged Paneth cells. Mechanistically, high activity of mammalian target of rapamycin complex 1 (mTORC1) in aged Paneth cells inhibits activity of peroxisome proliferator activated receptor alpha (PPAR-alpha)(3), and lowered PPAR-a activity increased Notum expression. Genetic targeting of Notum or Wnt supplementation restored function of aged intestinal organoids. Moreover, pharmacological inhibition of Notum in mice enhanced the regenerative capacity of aged stem cells and promoted recovery from chemotherapy-induced damage. Our results reveal a role of the stem cell niche in ageing and demonstrate that targeting of Notum can promote regeneration of aged tissues.Peer reviewe

Mule Regulates the Intestinal Stem Cell Niche via the Wnt Pathway and Targets EphB3 for Proteasomal and Lysosomal Degradation

The E3 ubiquitin ligase Mule is often overexpressed in human colorectal cancers, but its role in gut tumorigenesis is unknown. Here, we show in vivo that Mule controls murine intestinal stem and progenitor cell proliferation by modulating Wnt signaling via c-Myc. Mule also regulates protein levels of the receptor tyrosine kinase EphB3 by targeting it for proteasomal and lysosomal degradation. In the intestine, EphB/ephrinB interactions position cells along the crypt-villus axis and compartmentalize incipient colorectal tumors. Our study thus unveils an important new avenue by which Mule acts as an intestinal tumor suppressor by regulation of the intestinal stem cell niche

High fat diet enhances stemness and tumorigenicity of intestinal progenitors

Little is known about how pro-obesity diets regulate tissue stem and progenitor cell function. Here we find that high fat diet (HFD)-induced obesity augments the numbers and function of Lgr5+ intestinal stem-cells (ISCs) of the mammalian intestine. Mechanistically, HFD induces a robust peroxisome proliferator-activated receptor delta (PPAR-d) signature in intestinal stem and (non-ISC) progenitor cells, and pharmacologic activation of PPAR-d recapitulates the effects of a HFD on these cells. Like a HFD, ex vivo treatment of intestinal organoid cultures with fatty acid constituents of the HFD enhances the self-renewal potential of these organoid bodies in a PPAR-d dependent manner. Interestingly, HFD- and agonist-activated PPAR-d signaling endow organoid-initiating capacity to progenitors, and enforced PPAR-d signaling permits these progenitors to form in vivo tumors upon loss of the tumor suppressor Apc. These findings highlight how diet-modulated PPAR-d activation alters not only the function of intestinal stem and progenitor cells, but also their capacity to initiate tumors

Dietary Regulation of Adult Stem Cells

Purpose of Review: Dietary intake is a critical regulator of organismal physiology and health. Tissue homeostasis and regeneration are dependent on adult tissue stem cells that self-renew and differentiate into the specialized cell types. As stem cells respond to cues from their environment, dietary signals and nutrients influence tissue biology by altering the function and activity of adult stem cells. In this review, we highlight recent studies that illustrate how diverse diets such as caloric restriction, fasting, high-fat diets, and ketogenic diets impact stem cell function and their microenvironments. Recent Findings: Caloric restriction generally exerts positive effects on adult stem cells, notably increasing stem cell functionality in the intestine and skeletal muscle as well as increasing hematopoietic stem cell quiescence. Similarly, fasting confers protection of intestinal, hematopoietic, and neuronal stem cells against injury. High-fat diets induce intestinal stem cell niche independence and stem-like properties in intestinal progenitors, while high-fat diets impair hematopoiesis and neurogenesis. Summary: Caloric restriction and fasting are generally beneficial to adult stem cell function, while high-fat diets impair stem cell function or create opportunities for tumorigenesis. However, the effects of each diet on stem cell biology are complex and vary greatly between tissues. Given the recent interest in developing dietary interventions or mimetics as therapeutics, further studies, including on ketogenic diets, will be essential to understand how adult stem cells respond to diet-induced signals and physiology

High‐fat diet in a mouse insulin‐resistant model induces widespread rewiring of the phosphotyrosine signaling network

Abstract Obesity‐associated type 2 diabetes and accompanying diseases have developed into a leading human health risk across industrialized and developing countries. The complex molecular underpinnings of how lipid overload and lipid metabolites lead to the deregulation of metabolic processes are incompletely understood. We assessed hepatic post‐translational alterations in response to treatment of cells with saturated and unsaturated free fatty acids and the consumption of a high‐fat diet by mice. These data revealed widespread tyrosine phosphorylation changes affecting a large number of enzymes involved in metabolic processes as well as canonical receptor‐mediated signal transduction networks. Targeting two of the most prominently affected molecular features in our data, SRC‐family kinase activity and elevated reactive oxygen species, significantly abrogated the effects of saturated fat exposure in vitro and high‐fat diet in vivo. In summary, we present a comprehensive view of diet‐induced alterations of tyrosine signaling networks, including proteins involved in fundamental metabolic pathways