Biology subjects

Kohno, K.

Publications and source records attributed to Kohno, K..

5 recordsLinked to original sources

bioRxiv2025

Gelsolin Counteracts ER Stress-Driven Inflammatory Circuits in Psoriasis-like Dermatitis

Psoriasis is a chronic inflammatory skin disorder driven by amplified communication between immune cells and keratinocytes. Here, we show that imiquimod (IMQ) triggers organelle stress responses that directly contribute to this pathogenic circuit. In dendritic cells (DCs), IMQ promotes formation of ER-mitochondria contact sites (MAMs), inducing ER stress and activation of the unfolded protein response (UPR). These pathways act independently of, yet converge with, TLR7/MyD88 signaling to enhance IL-23 expression. IMQ also increases cytosolic Ca{superscript 2}+, facilitating NLRP3 inflammasome activation and release of mitochondrial DNA (mtDNA). In parallel, keratinocytes exposed to IMQ activate UPR-dependent genes, including Defb14 (mBD14), a psoriasis-associated antimicrobial peptide. Extracellular mtDNA and mBD14 then cooperatively stimulate plasmacytoid DCs through TLR9, establishing a feed-forward inflammatory loop. We further identify Gelsolin as a direct IMQ-binding protein that mitigates IMQ-induced ER stress; its loss amplifies ER stress, UPR activation, and oxidative stress, and its expression is reduced in human psoriatic lesions. Thus, MAM-UPR signaling links intracellular organelle stress to the intercellular networks that drive psoriatic inflammation, with Gelsolin acting as a critical intrinsic safeguard.

immunology↗

bioRxiv2024

Interleukin-4 induces CD11c+ microglia leading to amelioration of neuropathic pain in mice

Neuropathic pain, a debilitating chronic pain condition, is a major clinical challenge. The pleiotropic cytokine interleukin-4 (IL-4) has been shown to suppress neuropathic pain in rodent models, but its underlying mechanism remains unclear. Here, we show that intrathecal administration of IL-4 to mice with spinal nerve transection (SpNT) increased the number of CD11c+ microglia (a microglia subset important for pain remission) in the spinal dorsal horn (SDH) and that this effect of IL-4 was essential for its ameliorating effect on SpNT-induced pain hypersensitivity. Furthermore, in mice with spared nerve injury (SNI), another model in which pain remission does not occur, the emergence of CD11c+ SDH microglia was curtailed, but intrathecal IL-4 increased their emergence and ameliorated pain hypersensitivity in a CD11c+ microglia-dependent manner. Our study reveals a mechanism by which intrathecal IL-4 ameliorates pain hypersensitivity after nerve injury and provides evidence that IL-4 increases CD11c+ microglia with a function that ameliorates neuropathic pain.

pharmacology and toxicology↗

bioRxiv2020

Hepatocyte-specific deletion of XBP1 sensitizes mice to liver injury through hyperactivation of IRE1α

X-box binding protein-1 (XBP1) is a transcription factor that plays a central role in controlling cellular responses to endoplasmic reticulum (ER) stress. Under stress conditions, the transcriptionally active form of XBP1 is generated by unique splicing of Xbp1 mRNA by the ER-resident protein inositol-requiring enzyme-1 (IRE1). Genetic deletion of XBP1 has multiple consequences: some resulting from the loss of the transcription factor per se, and others related to compensatory upstream activation of IRE1. The objective of the current study was to investigate the effects of XBP1 deletion in adult mouse liver and determine to what extent they are direct or indirect. XBP1 was deleted specifically from hepatocytes in adult Xbp1fl/fl mice using AAV8-Transthyretin-Cre (Xbp1{Delta}hep). Xbp1{Delta}hep mice exhibited no liver disease at baseline, but developed acute biochemical and histologic liver injury in response to a dietary challenge with fructose for 4 wk. Fructose-mediated liver injury in Xbp1{Delta}hep mice coincided with heightened IRE1 activity, as demonstrated by cJun phosphorylation and regulated IRE1 -dependent RNA decay (RIDD). Activation of eIF2 was also evident, with associated up-regulation of the pro-apoptotic molecules CHOP, BIM and PUMA. To determine whether the adverse consequences of liver-specific XBP1 deletion were due to XBP1 loss or heightened IRE1 activity, we repeated a fructose challenge in mice with liver-specific deletion of both XBP1 and IRE1 (Xbp1{Delta}hep;IRE1{Delta}hep). Xbp1{Delta}hep;IRE1{Delta}hep mice were protected from fructose-mediated liver injury and failed to exhibit any of the signs of ER stress seen in mice lacking XBP1 alone. The protective effect of IRE1 deletion persisted even with long-term exposure to fructose. Xbp1{Delta}hep mice developed liver fibrosis at 16 wk, but Xbp1{Delta}hep;IRE1{Delta}hep mice did not. Overall, the results indicate that the deleterious effects of hepatocyte-specific XBP1 deletion are due primarily to hyperactivation of IRE1. They support further exploration of IRE1 as a contributor to acute and chronic liver diseases.

cell biology↗

bioRxiv2019

Genome-wide survey of ribosome collision

In protein synthesis, ribosome movement is not always smooth and is rather often impeded for numerous reasons. Although the deceleration of the ribosome defines the fates of the mRNAs and synthesizing proteins, fundamental issues remain to be addressed, including where ribosomes pause in mRNAs, what kind of RNA/amino acid sequence causes this pause, and the physiological significance of this slowdown of protein synthesis. Here, we surveyed the positions of ribosome collisions caused by ribosome pausing in humans and zebrafish on a genome-wide level using modified ribosome profiling. The collided ribosomes, i.e., disomes, emerged at various sites: the proline-proline-lysine motif, stop codons, and the 3' untranslated region (UTR). The number of ribosomes involved in a collision is not limited to two, but rather four to five ribosomes can form a queue of ribosomes. In particular, XBP1, a key modulator of the unfolded protein response, shows striking queues of collided ribosomes and thus acts as a substrate for ribosome-associated quality control (RQC) to avoid the accumulation of undesired proteins in the absence of stress. Our results provide an insight into the causes and consequences of ribosome slowdown by dissecting the specific architecture of ribosomes.

molecular biology↗

bioRxiv2019

Structural and mutational analysis of the ribosome-arresting human XBP1u

XBP1u, a central component of the unfolded protein response (UPR), is a mammalian protein containing a functionally critical translational arrest peptide (AP). Here, we present a 3 [A] cryo-EM structure of the stalled human XBP1u AP. It forms a unique turn in the upper part of the ribosomal exit tunnel and causes a subtle distortion of the peptidyl transferase center, explaining the temporary translational arrest induced by XBP1u. During ribosomal pausing the hydrophobic region 2 (HR2) of XBP1u is recognized by SRP, but fails to efficiently gate the Sec61 translocon. An exhaustive mutagenesis scan of the XBP1u AP revealed that only 10 out of 21 mutagenized positions in the XBP1u AP are optimal with respect to translational arrest activity. Thus, XBP1u has evolved to induce an intermediate level of translational arrest, allowing efficient targeting by SRP without activating the Sec61 channel and thereby serving its central function in the UPR.

biochemistry↗