Replicative capacity of SARS-CoV-2 omicron variants BA.5 and BQ.1.1 at elevated temperatures

新型コロナウイルス・オミクロン株のBA.5系統およびBQ.1.1系統が、高温で増殖しづらいことを解明. 京都大学プレスリリース. 2023-04-27

Ubiquitin carboxyl-terminal hydrolase L1 promotes hypoxia-inducible factor 1-dependent tumor cell malignancy in spheroid models

Hypoxia‐inducible factor 1 (HIF‐1) is a critical heterodimeric transcription factor for tumor malignancy. Recently, ubiquitin carboxyl‐terminal hydrolase L1 (UCHL1) has been reported to function as a deubiquitinating enzyme for the stabilization of its α subunit (HIF‐1α). In the present study, we showed that UCHL1 inhibition can be an effective therapeutic strategy against HIF‐1‐dependent tumor malignancy. In 2D monolayer culture, a UCHL1 inhibitor suppressed HIF activity and decreased the transcription of HIF downstream genes by inhibiting the UCHL1‐mediated accumulation of HIF‐1α. Phenotypically, UCHL1 inhibition remarkably blocked cell migration. In 3D spheroid culture models, ectopic expression of UCHL1 significantly upregulated malignancy‐related factors such as solidity, volume, as well as viable cell number in an HIF‐1α‐dependent manner. Conversely, inhibition of the UCHL1‐HIF‐1 pathway downregulated these malignancy‐related factors and also abolished UCHL1‐mediated cell proliferation and invasiveness. Finally, inhibition of UCHL1 promoted HIF‐1α degradation and lowered the expression of HIF‐1 target genes in the 3D model, as also observed in 2D monolayer culture. Our research indicates that the UCHL1‐HIF‐1 pathway plays a crucial role in tumor malignancy, making it a promising therapeutic target for cancer chemotherapy

Involvement of protein kinase in Δ12-prostaglandin J2-induced expression of rat heme oxygenase-1 gene

AbstractWe recently identified the cis-regulatory element and its specific nuclear binding factors for Δ12-prostaglandin (PG) J2-induced expression of the rat heme oxygenase, HO-1 [Koizumi, T., Odani, N., Okuyama, T., Ichikawa, A. and Negishi, M. (1995)J. Biol. Chem. 270, in press]. Here we further examined the molecular mechanism underlying the Δ12-PGJ2-induced HO-1 gene expression. Protein kinase inhibitors, 2-aminopurine and staurosporine, suppressed the Δ12-PGJ2-induced HO-1 mRNA and the nuclear protein binding to the Δ12-PGJ2-responsivecis-regulatory element in rat basophilic leukemia cells. Furthermore, the nuclear protein binding to the element was suppressed by in vitro phosphatase treatment of the nuclear proteins from Δ12-PGJ2-treated cells. These findings suggest that Δ12-PGJ2 induces the expression of the HO-1 gene through phosphorylation of the nuclear proteins which bind to the Δ12-PGJ2-responsive element

EFA6 activates Arf6 and participates in its targeting to the Flemming body during cytokinesis.

The small GTPase Arf6 is transiently associated with the ingressing cleavage furrow and subsequently targeted to the Flemming body during cytokinesis, suggesting its activation around the cleavage furrow. Here, we show that EFA6 (exchange factor for Arf6) localizes on the cleavage furrow through its PH domain. Time-lapse analysis showed that both EFA6 and Arf6 are transiently localized around the ingressing cleavage furrow, but only Arf6 is subsequently targeted to the Flemming body. Expression of an EFA6 mutant suppresses Arf6 recruitment onto the Flemming body. These results suggest that EFA6 participates in activation of Arf6 around the cleavage furrow during cytokinesis

SNAP23/25 and VAMP2 mediate exocytic event of transferrin receptor-containing recycling vesicles

We recently showed that Rab11 is involved not only in formation of recycling vesicles containing the transferrin (Tfn)–transferrin receptor (TfnR) complex at perinuclear recycling endosomes but also in tethering of recycling vesicles to the plasma membrane (PM) in concert with the exocyst tethering complex. We here aimed at identifying SNARE proteins responsible for fusion of Tfn–TfnR-containing recycling vesicles with the PM, downstream of the exocyst. We showed that exocyst subunits, Sec6 and Sec8, can interact with SNAP23 and SNAP25, both of which are PM-localizing Qbc-SNAREs, and that depletion of SNAP23 and/or SNAP25 in HeLa cells suppresses fusion of Tfn–TfnR-containing vesicles with the PM, leading to accumulation of the vesicles at the cell periphery. We also found that VAMP2, an R-SNARE, is colocalized with endocytosed Tfn on punctate endosomal structures, and that its depletion in HeLa cells suppresses recycling vesicle exocytosis. These observations indicate that fusion of recycling vesicles with the PM downstream of the exocyst is mediated by SNAP23/25 and VAMP2, and provide novel insight into non-neuronal roles of VAMP2 and SNAP25

Structural basis for Arf6-MKLP1 complex formation on the Flemming body responsible for cytokinesis

正常な細胞分裂に不可欠なタンパク質の機能と構造を解明. 京都大学プレスリリース. 2012-05-31.A small GTPase, Arf6, is involved in cytokinesis by localizing to the Flemming body (the midbody). However, it remains unknown how Arf6 contributes to cytokinesis. Here, we demonstrate that Arf6 directly interacts with mitotic kinesin-like protein 1 (MKLP1), a Flemming body-localizing protein essential for cytokinesis. The crystal structure of the Arf6-MKLP1 complex reveals that MKLP1 forms a homodimer flanked by two Arf6 molecules, forming a 2:2 heterotetramer containing an extended β-sheet composed of 22 β-strands that spans the entire heterotetramer, suitable for interaction with a concave membrane surface at the cleavage furrow. We show that, during cytokinesis, Arf6 is first accumulated around the cleavage furrow and, prior to abscission, recruited onto the Flemming body via interaction with MKLP1. We also show by structure-based mutagenesis and siRNA-mediated knockdowns that the complex formation is required for completion of cytokinesis. A model based on these results suggests that the Arf6-MKLP1 complex plays a crucial role in cytokinesis by connecting the microtubule bundle and membranes at the cleavage plane

Cryptotanshinone is a candidate therapeutic agent for interstitial lung disease associated with a BRICHOS-domain mutation of SFTPC

Summary: Interstitial lung disease (ILD) represents a large group of diseases characterized by chronic inflammation and fibrosis of the lungs, for which therapeutic options are limited. Among several causative genes of familial ILD with autosomal dominant inheritance, the mutations in the BRICHOS domain of SFTPC cause protein accumulation and endoplasmic reticulum stress by misfolding its proprotein. Through a screening system using these two phenotypes in HEK293 cells and evaluation using alveolar epithelial type 2 (AT2) cells differentiated from patient-derived induced pluripotent stem cells (iPSCs), we identified Cryptotanshinone (CPT) as a potential therapeutic agent for ILD. CPT decreased cell death induced by mutant SFTPC overexpression in A549 and HEK293 cells and ameliorated the bleomycin-induced contraction of the matrix in fibroblast-dependent alveolar organoids derived from iPSCs with SFTPC mutation. CPT and this screening strategy can apply to abnormal protein-folding-associated ILD and other protein-misfolding diseases