Biology subjects

Ushida, T.

Publications and source records attributed to Ushida, T..

3 recordsLinked to original sources

bioRxiv2023

Ras Activation by Hydrostatic Pressure is Enhanced by GAP and GEF in vitro

Hydrostatic pressure (HP) is a necessary stimulus for cell differentiation and growth in cultured chondrocytes. Assuming that Ras activation is involved in HP-induced reactions, if cellular Ras activity is increased by HP, Ras itself, Raf, Ras regulators including GTPase activating proteins (GAP) and guanine nucleotide exchange factors (GEF), then the upstream receptor and/or interactions between them should have HP sensitivity. Based on this hypothesis, we first attempted to examine whether Ras is activated by HP, and in the affirmative, identify which factors displayed HP sensitivity using an in vitro system to measure Ras activity. This in vitro system included mRaichu, a FRET-based Ras activity probe, to which two-point mutations were introduced to reduce Ras-independent signals. This improved Raichu was used to investigate the HP sensitivity of two components, the GAP domain (GAPd) derived from p120GAP and the GEF domain (GEFd) derived from hSOS-1. It was found that HP weakly activated Ras activity in the absence of GAPd and GEFd, presumably by facilitating GDP dissociation from Ras. A low concentration of GAPd enhanced HP-induced Ras activation by 16.3% whereas high concentrations of GAPd removed HP sensitivity, suggesting that HP partially dissociates GAPd from the GAPd-Ras-GDP complex and reduces the fraction of inactive Ras. Moreover, a broad concentration range of GEFd also enhanced HP-induced Ras activation. Given that HP also increased Ras activity under a condition mimicking cellular Ras activity, we propose that Ras activation is involved in the differentiation and growth stimulation of chondrocytes by HP. Statement of SignificanceThe Ras-cycle has been implicated in the regulation of growth and differentiation of eukaryotic cells. Here, we investigated the relationship between hydrostatic pressure (HP) and components of the Ras-cycle: Ras-Raf, the GAP domain, and the GEF domain. Generally, HP tends to weaken protein-protein and protein-ligand interactions, but in this study, a seemingly positive response was observed: HP-induced Ras activation. Additionally, this response was enhanced by the GEF domain and the GAP domain. Thus, given the multiple cellular functions of Ras and the responses of the Ras-cycle to HP, this study will help clarify the molecular mechanism by which HP modulates cellular functions, particularly in chondrocytes, which are subjected to repetitive HP stimuli in vivo.

biophysics↗

bioRxiv2021

Transgenerational impact of aberrant inflammation in rat pregnancy

Children of women with pre-eclampsia have increased risk of cardiovascular (CV) and metabolic disease in adult life. Furthermore, the risk of pregnancy complications is higher in daughters born to women affected by pre-eclampsia than in daughters born after uncomplicated pregnancies. While aberrant inflammation contributes to the pathophysiology of pregnancy complications, including pre-eclampsia, the contribution of maternal inflammation to subsequent risk of CV and metabolic disease as well as pregnancy complications in the offspring remains unclear. Here we demonstrate that 24-week-old female rats (F1) born to dams (F0) exposed to lipopolysaccharide (LPS) during pregnancy (to induce inflammation) exhibited mild systolic dysfunction, increased cardiac growth-related gene expression, abnormal glucose tolerance and coagulopathy; whereas male F1 offspring exhibited abnormal glucose tolerance and increased visceral fat accumulation compared with F1 sex-matched offspring born to saline-treated dams. Both male and female F1 offspring born to LPS-treated dams had evidence of anemia. Fetuses (F2) from F1 females born to LPS-treated dams were growth restricted, and this reduction in fetal growth was associated with increased CD68 positivity and decreased expression of glucose transporter-1 in their utero-placental units. These results indicate that abnormal maternal inflammation can contribute to increased risk of CV and metabolic disease in offspring, and that the effects of inflammation may be transgenerational. This study provides evidence in support of early screening for CV and metabolic disease, as well as pregnancy complications in offspring affected by pre-eclampsia or other pregnancy complications associated with aberrant inflammation.

developmental biology↗

bioRxiv2020

microRNAs slow translating ribosomes to prevent protein misfolding

An evolutionarily conserved mechanism, use of non-optimal codons, slows ribosomes during translation to allow proper folding of nascent polypeptides. However, until now, it was unknown whether any eukaryote-specific mechanisms exist for this purpose. Here, we propose that miRNAs slow translating ribosomes to prevent protein misfolding, with little negative effect on protein abundance. To prove this, we bioinformatically analyze ribosome profiling and miRNA binding sites and biochemically confirm that miRNA deficiency causes severe misfolding, which is rescued by slowing translating ribosomes. We demonstrate that non-cleaving shRNAs, targeting regions where elongation rates become faster in miRNA-deficient cells, improve protein folding with minimal effects on protein abundance. These results reveal broader functionality of miRNAs and a previously unknown mechanism to prevent protein misfolding. One Sentence SummaryEukaryote use of miRNAs prevents protein misfolding in a target-specific manner.

biochemistry↗