Biology subjects

Kado, T.

Publications and source records attributed to Kado, T..

5 recordsLinked to original sources

bioRxiv2023

Isoxanthohumol improves obesity and glucose metabolism via inhibiting intestinal lipid absorption with a bloom of Akkermansia muciniphila in mice

AimsDysbiosis is an important factor that leads to metabolic disorders by disrupting energy balance and insulin sensitivity. A decrease in Akkermansia muciniphila is a phenotype of obesity-induced dysbiosis. Although interventions to increase A. muciniphila are expected to improve glucose metabolism, the underlying mechanism has not been fully understood. MethodsIsoxanthohumol (IX), a prenylated flavonoid found in beer hops was administered to high fat diet-fed mice. We analyzed glucose metabolism, gene expression profiles and histology of liver, epididymal adipose tissue and colon. Lipase activity, fecal lipid profiles and plasma metabolomic analysis were assessed. Fecal 16s rRNA sequencing was obtained and selected bacterial species were used for in vitro studies. Fecal microbiota transplantation and monocolonization were conducted to antibiotic-treated or germ-free (GF) mice. ResultsThe administration of IX lowered weight gain, decreased steatohepatitis and improved glucose metabolism. Mechanistically, IX inhibited pancreatic lipase activity and lipid absorption by decreasing the expression of the fatty acid transporter CD36 in the small intestine, which was confirmed by increased lipid excretion in feces. IX administration improved the gut barrier function and reduced metabolic endotoxemia. In contrast, the effects of IX were nullified by antibiotics. As revealed using 16S rRNA sequencing, the microbial community structure changed with a significant increase in the abundance of A. muciniphila in the IX-treated group. An anaerobic chamber study showed that IX selectively promoted the growth of A. muciniphila while exhibiting antimicrobial activity against some Bacteroides and Clostridium species. To further explore the direct effect of A. muciniphila on lipid and glucose metabolism, we monocolonized either A. muciniphila or Bacteroides thetaiotaomicron to GF mice. A. muciniphila monocolonization decreased CD36 expression in the jejunum and improved glucose metabolism, with decreased levels of multiple classes of fatty acids determined using plasma metabolomic analysis. ConclusionOur study confirmed a direct role of A. muciniphila in energy metabolism, which was induced by microbial actions of IX. These highlight new treatment strategies for preventing metabolic syndrome by boosting the gut microbiota with food components.

microbiology↗

bioRxiv2022

Genetic and lipidomic identification of tuberculostearic acid as a controller of mycobacterial membrane compartmentalization

Mycobacteria diverge in a basic way from other bacterial and eukaryotic cells based on their distinct membrane structures. Here we report genome-wide transposon sequencing to discover the controllers of membrane compartmentalization in Mycobacterium smegmatis. cfa, a gene that encodes a putative cyclopropane-fatty-acyl-phospholipid synthase, shows the most significant effect on recovery from a membrane destabilizer, dibucaine. Lipidomic analysis of cfa deletion mutants demonstrates an essential role of Cfa in the synthesis of specific membrane lipids containing a C19:0 monomethyl-branched stearic acid. This molecule, also known as tuberculostearic acid (TBSA), has been intensively studied for decades due to its high level and genus-specific expression in mycobacteria. The proposed Cfa-mediated conversion of an unsaturation to a methylation matched well with its proposed role in lateral membrane organization, so we used new tools to determine the non-redundant effects of Cfa and TBSA in mycobacterial cells. cfa expression regulated major classes of membrane lipids including phosphatidylinositols, phosphatidylethanolamines and phosphatidylinositol mannosides. Cfa localized within the intracellular membrane domain (IMD), where it controls both cellular growth and recovery from membrane fluidization by facilitating subpolar localization of the IMD. Overall, cfa controls lateral membrane partitioning but does not detectably alter orthogonal transmembrane permeability. More generally, these results support the proposed role of the subpolar IMD as a subcellular site of mycobacterial control of membrane function. SignificanceMycobacteria remain major causes of disease worldwide based in part on their unusual membrane structures, which interface with the host. Here we discover the long sought biosynthetic origin of tuberculostearic acid (TBSA), a major fatty acid found selectively in mycobacteria, as well as its role in mycobacterial cells. The lipid is produced by an enzyme called Cfa, whose loss causes a growth defect and slow reformation of a membrane domain near the pole of the rod-shaped cell. Thus, our study offers mechanistic insights to the intrinsic molecular factors critical for mycobacterial plasma membrane partitioning.

microbiology↗

bioRxiv2022

Inositol acylation of phosphatidylinositol mannosides: a rapid mass response to membrane fluidization in mycobacteria

Mycobacteria share an unusually complex, multilayered cell envelope, which contributes to adaptation to changing environments. The plasma membrane is the deepest layer of the cell envelope and acts as the final permeability barrier against outside molecules. There is an obvious need to maintain the plasma membrane integrity, but the adaptive responses of plasma membrane to stress exposure remain poorly understood. Using chemical treatment and heat stress to fluidize the membrane, we show here that phosphatidylinositol (PI)-anchored plasma membrane glycolipids known as PI mannosides (PIMs) rapidly remodel their structures upon membrane fluidization in Mycobacterium smegmatis. Without membrane stress, PIMs are predominantly in a tri-acylated form: two acyl chains of PI moiety plus one acyl chain modified at one of the mannose residues. Upon membrane fluidization, the fourth fatty acid is added to the inositol moiety of PIMs, making them tetra-acylated variants. PIM inositol acylation is a rapid response independent of de novo protein synthesis, representing one of the fastest mass conversions of lipid molecules found in nature. Strikingly, we found that M. smegmatis is more resistant to the bactericidal effect of a cationic detergent after benzyl alcohol preexposure. We further demonstrate that fluidization-induced PIM inositol acylation is conserved in pathogens such as Mycobacterium tuberculosis and Mycobacterium abscessus. Our results demonstrate that mycobacteria possess a mechanism to sense plasma membrane fluidity change. We suggest that inositol acylation of PIMs is a novel membrane stress response that enables mycobacterial cells to resist membrane fluidization.

biochemistry↗

bioRxiv2022

The cell wall polymer initiates plasma membrane partitioning in mycobacteria

Lateral partitioning of proteins and lipids shapes membrane function. In model membranes, partitioning can be influenced by interactions with other membranes and solid supports. While cellular membranes can departition in response to various perturbations, including disruption of bilayer-extrinsic structures, the mechanisms by which they partition de novo are largely unknown. The plasma membrane of Mycobacterium smegmatis can be spatially and biochemically departitioned by the fluidizing agent benzyl alcohol. By screening for mutants that are sensitive to benzyl alcohol, we show that the bifunctional cell wall synthase PonA2 promotes membrane partitioning and cell growth upon fluidizer washout. PonA2s role in membrane repartitioning and regrowth depends solely on its conserved transglycosylase domain. We find that the cell wall polymer, but not active cell wall polymerization, is critical for membrane partitioning. Our work highlights a key initiating role for bilayer-extrinsic structures in patterning cellular membranes.

molecular biology↗

bioRxiv2021

Cell wall damage reveals spatial flexibility in peptidoglycan synthesis and a non-redundant role for RodA in mycobacteria

Cell wall peptidoglycan is a heteropolymeric mesh that protects the bacteria from internal turgor and external insults. In many rod-shaped bacteria, peptidoglycan synthesis for normal growth is achieved by two distinct pathways: the Rod complex, comprised of MreB, RodA and a cognate class B PBP, and the class A PBPs. In contrast to laterally-growing bacteria, pole-growing mycobacteria do not encode an MreB homolog and do not require SEDS protein RodA for in vitro growth. However, RodA contributes to survival of Mycobacterium tuberculosis in some infection models, suggesting that the protein could have a stress-dependent role in maintaining cell wall integrity. Under basal conditions, we find here that the subcellular distribution of RodA largely overlaps with that of the aPBP PonA1, and that both RodA and the aPBPs promote polar peptidoglycan assembly. Upon cell wall damage, RodA fortifies M. smegmatis against lysis and, unlike aPBPs, contributes to a shift in peptidoglycan assembly from the poles to the sidewall. Neither RodA nor PonA1 relocalize; instead, the redistribution of nascent cell wall parallels that of peptidoglycan precursor synthase MurG. Our results support a model in which mycobacteria balance polar growth and cell-wide repair via spatial flexibility in precursor synthesis and extracellular insertion. ImportancePeptidoglycan synthesis is a highly successful target for antibiotics. The pathway has been extensively studied in model organisms under laboratory-optimized conditions. In natural environments, bacteria are frequently under attack. Moreover the vast majority of bacterial species are unlikely to fit a single paradigm because of differences in growth mode and/or envelope structure. Studying cell wall synthesis under non-optimal conditions and in non-standard species may improve our understanding of pathway function and suggest new inhibition strategies. Mycobacterium smegmatis, a relative of several notorious human and animal pathogens, has an unusual polar growth mode and multi-layered envelope. In this work we challenged M. smegmatis with cell wall-damaging enzymes to characterize the roles of cell wall-building enzymes when the bacterium is under attack.

microbiology↗