Biology subjects

Kanekura, K.

Publications and source records attributed to Kanekura, K..

3 recordsLinked to original sources

bioRxiv2026

Inflammatory restraint and membrane lipid integrity protect hematopoietic stem cells under stress

Life-long production of blood requires the preservation of hematopoietic stem cell (HSCs) regenerative capacity during inflammation. The cytokine, Thrombopoietin (THPO), is essential for HSC maintenance yet its role during inflammatory stress remains incompletely understood. Long-term repopulating potential was rapidly depleted in THPO-deficient HSCs upon poly(I:C) administration through inflammatory pyroptosis. Transcriptomic and chromatin accessibility analyses revealed constitutive interferon (IFN) pathway activation in THPO-deficient HSCs, characterized by enhanced STAT1 signaling, increased accessibility of STAT and IRF motifs, and elevated expression of IFN-stimulated genes. Lipidomic profiling further identified selective shifts in sphingomyelin (SM) species and enrichment of features associated with increased bilayer rigidity. THPO-deficient HSCs displayed elevated membrane SM incorporation, impaired membrane fluidity and altered membrane ultrastructure. Genetic ablation of Stat1 normalized membrane lipid abnormalities and reduced pyroptotic activation and restored HSC survival and regenerative function under inflammatory stress. Together, these findings identify a STAT1 and SM metabolism as critical THPO downstream to protect HSCs from inflammatory pyroptosis. Our results reveal membrane lipid homeostasis as a fundamental mechanism through which cytokine signaling safeguards HSC function during stress.

cell biology↗

bioRxiv2024

Serine chirality guides metabolic flow between one-carbon metabolism and neuromodulator synthesis

O_SCPLOWLC_SCPLOW-serine serves as a central metabolic node that integrates glycolytic flux, lipid metabolism, and one-carbon metabolism. In the mature central nervous system, O_SCPLOWLC_SCPLOW-serine is actively stereo-converted to O_SCPLOWDC_SCPLOW-serine, which functions as a neurotransmitter. However, the role of O_SCPLOWDC_SCPLOW-serine in cellular metabolism remains unclear. Here, we show that O_SCPLOWDC_SCPLOW-serine competes with mitochondrial O_SCPLOWLC_SCPLOW-serine transport, thereby suppressing one-carbon metabolism. Metabolomic analysis revealed that O_SCPLOWDC_SCPLOW-serine reduces intracellular glycine and formate levels, indicating inhibition of the initial step of the one-carbon pathway. Molecular dynamics simulations and enzymatic assays revealed that O_SCPLOWDC_SCPLOW-serine has low affinity for serine hydroxymethyltransferase 2 (Shmt2), which catalyzes the first step in mitochondrial one-carbon metabolism, and does not directly inhibit its activity. Instead, membrane transport assays demonstrated that O_SCPLOWDC_SCPLOW-serine competes with mitochondrial O_SCPLOWLC_SCPLOW-serine transport, depleting the substrate of Shmt2. Functionally, under O_SCPLOWLC_SCPLOW-serine poor conditions in vitro and ex vivo, O_SCPLOWDC_SCPLOW-serine inhibited the proliferation of immature and undifferentiated neural cells including glioblastoma stem cells, which depend highly on one-carbon metabolism. Notably, endogenous O_SCPLOWDC_SCPLOW-serine levels were low during early neurodevelopment, but increased with maturation, coinciding with a shift in the transcriptional profiles of serine metabolic enzymes at the cellular level. Given that O_SCPLOWLC_SCPLOW-serine supports neurodevelopment and O_SCPLOWDC_SCPLOW-serine modulates neurotransmission, this developmental shift in serine enantiomer metabolism appears to align with the functional transitions of the maturing nervous system. Thus, our findings reveal that serine chirality can influence mitochondrial substrate availability and one-carbon flux, offering previously unappreciated insight into the stereoselective regulation of cellular metabolism.

developmental biology↗

bioRxiv2021

An improved molecular crowding sensor CRONOS for detection of crowding changes in membrane-less organelles under pathological conditions.

Membrane-less organelles (MLOs) formed by liquid-liquid phase separation (LLPS) play pivotal roles in biological processes. During LLPS, proteins and nucleotides are extremely condensed, resulting in changes of their conformation and biological functions. Disturbed LLPS homeostasis in MLOs cause fatal diseases such as amyotrophic lateral sclerosis. Therefore, it is important to detect changes of the degree of crowding in MLOs. However, it has not been investigated well due to lack of an appropriate method. To address this, we developed a genetically-encoded molecular crowding sensor CRONOS that senses the degree of macromolecular crowding in MLOs using fluorescence resonance energy transfer (FRET) system. CRONOS is a very bright biosensor with wider dynamic range and detect changes in the macromolecular volume fraction better than the previously reported mCer-mCit sensor in solution. By fusing to scaffold protein of each MLO, we successfully delivered CRONOS to MLO of interest and detected previously undescribed difference of the degree of crowding in each MLO. If not tagged, CRONOS localized to interstitial space of MLOs, giving us the crowding information of inspace. CRONOS also detected changes of degree of macromolecular crowding in nucleolus induced by environmental stress or inhibition of transcription. These findings suggest that CRONOS can be a useful tool for determination of molecular crowding and detection of pathological changes in MLOs in live cells.

biochemistry↗