ABSTRACT
Comprehensive development is critical for gut macrophages being essential for the intestinal immune system. However, the underlying mechanisms of macrophage development in the colon remain elusive. To investigate the function of branched-chain amino acids in the development of gut macrophages, an inducible knock-out mouse model for the branched-chain amino acid transporter CD98hc in CX3CR1+ macrophages was generated. The relatively selective deletion of CD98hc in macrophage populations leads to attenuated severity of chemically-induced colitis that we assessed by clinical, endoscopic, and histological scoring. Single-cell RNA sequencing of colonic lamina propria macrophages revealed that conditional deletion of CD98hc alters the "monocyte waterfall"-development to MHC II+ macrophages. The change in the macrophage development after deletion of CD98hc is associated with increased apoptotic gene expression. Our results show that CD98hc deletion changes the development of colonic macrophages.
Subject(s)
Amino Acids, Branched-Chain/metabolism , Colitis/metabolism , Colon/metabolism , Fusion Regulatory Protein 1, Heavy Chain/deficiency , Intestinal Mucosa/metabolism , Macrophages/metabolism , Adolescent , Adult , Aged , Aged, 80 and over , Animals , Apoptosis , Apoptosis Regulatory Proteins/genetics , Apoptosis Regulatory Proteins/metabolism , CX3C Chemokine Receptor 1/genetics , CX3C Chemokine Receptor 1/metabolism , Colitis/chemically induced , Colitis/pathology , Colitis/prevention & control , Colitis, Ulcerative/diagnosis , Colitis, Ulcerative/genetics , Colitis, Ulcerative/metabolism , Colon/ultrastructure , Crohn Disease/diagnosis , Crohn Disease/genetics , Crohn Disease/metabolism , Dextran Sulfate , Disease Models, Animal , Female , Fusion Regulatory Protein 1, Heavy Chain/genetics , Gene Expression Regulation , Humans , Intestinal Mucosa/ultrastructure , Macrophages/ultrastructure , Male , Mice, Inbred C57BL , Mice, Knockout , Middle Aged , Phenotype , RNA-Seq , Single-Cell Analysis , Young AdultABSTRACT
Mechanical and metabolic cues independently contribute to the regulation of cell and tissue homeostasis. However, how they cross-regulate each other during this process remains largely unknown. Here, we show that cellular metabolism can regulate integrin rigidity-sensing via the sphingolipid metabolic pathway controlled by the amino acid transporter and integrin coreceptor CD98hc (SLC3A2). Genetic invalidation of CD98hc in dermal cells and tissue impairs rigidity sensing and mechanical signaling downstream of integrins, including RhoA activation, resulting in aberrant tissue mechanical homeostasis. Unexpectedly, we found that this regulation does not occur directly through regulation of integrins by CD98hc but indirectly, via the regulation of sphingolipid synthesis and the delta-4-desaturase DES2. Loss of CD98hc decreases sphingolipid availability preventing proper membrane recruitment, shuttling and activation of upstream regulators of RhoA including Src kinases and GEF-H1. Altogether, our results unravel a novel cross-talk regulation between integrin mechanosensing and cellular metabolism which may constitute an important new regulatory framework contributing to mechanical homeostasis.
