Publications by authors named "Tomomi Kanai"

3 Publications

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Direct Observation of Conversion From Walled Cells to Wall-Deficient L-Form and in Indicates the Essentiality of the Outer Membrane for Proliferation of L-Form Cells.

Front Microbiol 2021 11;12:645965. Epub 2021 Mar 11.

Department of Life Science, College of Science, Rikkyo University, Tokyo, Japan.

Gram-negative bacteria such as are surrounded by an outer membrane, which encloses a peptidoglycan layer. Even if thinner than in many Gram-positive bacteria, the peptidoglycan in allows cells to withstand turgor pressure in hypotonic medium. In hypertonic medium, treated with a cell wall synthesis inhibitor such as penicillin G form wall-deficient cells. These so-called L-form cells grow well under anaerobic conditions (i.e., in the absence of oxidative stress), becoming deformed and dividing as L-form. Upon removal of the inhibitor, they return to the walled rod-shaped state. Recently, the outer membrane was reported to provide rigidity to Gram-negative bacteria and to strengthen wall-deficient cells. However, it remains unclear why L-form cells need the outer membrane for growth. Using a microfluidic system, we found that, upon treatment with the outer membrane-disrupting drugs polymyxin B and polymyxin B nonapeptide or with the outer membrane synthesis inhibitor CHIR-090, the cells lysed during cell deformation and division, indicating that the outer membrane was important even in hypertonic medium. L-form cells could return to rod-shaped when trapped in a narrow space, but not in a wide space, likely due to insufficient physical force. Outer membrane rigidity could be compromised by lack of outer membrane proteins; Lpp, OmpA, or Pal. Deletion of caused cells to lyse during cell deformation and cell division. In contrast, and mutants could be deformed and return to small oval cells even when less physical force was exerted. These results strongly suggest that wall-deficient cells require a rigid outer membrane to survive, but not too rigid to prevent them from changing cell shape.
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http://dx.doi.org/10.3389/fmicb.2021.645965DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7991099PMC
March 2021

Generation of a p16 Reporter Mouse and Its Use to Characterize and Target p16 Cells In Vivo.

Cell Metab 2020 11 18;32(5):814-828.e6. Epub 2020 Sep 18.

Division of Molecular Regulation of Inflammatory and Immune Diseases, Research Institute of Biomedical Sciences, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-0022, Japan.

Cell senescence plays a key role in age-associated organ dysfunction, but the in vivo pathogenesis is largely unclear. Here, we generated a p16-Cre-tdTomato mouse model to analyze the in vivo characteristics of p16 cells at a single-cell level. We found tdTomato-positive p16 cells detectable in all organs, which were enriched with age. We also found that these cells failed to proliferate and had half-lives ranging from 2.6 to 4.2 months, depending on the tissue examined. Single-cell transcriptomics in the liver and kidneys revealed that p16 cells were present in various cell types, though most dominant in hepatic endothelium and in renal proximal and distal tubule epithelia, and that these cells exhibited heterogeneous senescence-associated phenotypes. Further, elimination of p16 cells ameliorated nonalcoholic steatohepatitis-related hepatic lipidosis and immune cell infiltration. Our new mouse model and single-cell analysis provide a powerful resource to enable the discovery of previously unidentified senescence functions in vivo.
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http://dx.doi.org/10.1016/j.cmet.2020.09.006DOI Listing
November 2020

Exclusion of assembled MreB by anionic phospholipids at cell poles confers cell polarity for bidirectional growth.

Mol Microbiol 2017 May 24;104(3):472-486. Epub 2017 Feb 24.

Department of Life Science, College of Science, Rikkyo University, 3-34-1 Nishi-Ikebukuro, Toshima-ku, Tokyo, 171-8501, Japan.

Cell polarity determines the direction of cell growth in bacteria. MreB actin spatially regulates peptidoglycan synthesis to enable cells to elongate bidirectionally. MreB densely localizes in the cylindrical part of the rod cell and not in polar regions in Escherichia coli. When treated with A22, which inhibits MreB polymerization, rod-shaped cells became round and MreB was diffusely distributed throughout the cytoplasmic membrane. A22 removal resulted in restoration of the rod shape. Initially, diffuse MreB started to re-assemble, and MreB-free zones were subsequently observed in the cytoplasmic membrane. These MreB-free zones finally became cell poles, allowing the cells to elongate bidirectionally. When MreB was artificially located at the cell poles, an additional pole was created, indicating that artificial localization of MreB at the cell pole induced local peptidoglycan synthesis. It was found that the anionic phospholipids (aPLs), phosphatidylglycerol and cardiolipin, which were enriched in cell poles preferentially interact with monomeric MreB compared with assembled MreB in vitro. MreB tended to localize to cell poles in cells lacking both aPLs, resulting in production of Y-shaped cells. Their findings indicated that aPLs exclude assembled MreB from cell poles to establish cell polarity, thereby allowing cells to elongate in a particular direction.
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http://dx.doi.org/10.1111/mmi.13639DOI Listing
May 2017