Mps1Mph1 kinase phosphorylates Mad3 to inhibit Cdc20Slp1-APC/C and maintain spindle checkpoint arrests

<div><p>The spindle checkpoint is a mitotic surveillance system which ensures equal segregation of sister chromatids. It delays anaphase onset by inhibiting the action of the E3 ubiquitin ligase known as the anaphase promoting complex or cyclosome (APC/C). Mad3/BubR1 is a key component of the mitotic checkpoint complex (MCC) which binds and inhibits the APC/C early in mitosis. Mps1^Mph1 kinase is critical for checkpoint signalling and MCC-APC/C inhibition, yet few substrates have been identified. Here we identify Mad3 as a substrate of fission yeast Mps1^Mph1 kinase. We map and mutate phosphorylation sites in Mad3, producing mutants that are targeted to kinetochores and assembled into MCC, yet display reduced APC/C binding and are unable to maintain checkpoint arrests. We show biochemically that Mad3 phospho-mimics are potent APC/C inhibitors <i>in vitro</i>, demonstrating that Mad3p modification can directly influence Cdc20^Slp1-APC/C activity. This genetic dissection of APC/C inhibition demonstrates that Mps1^Mph1 kinase-dependent modifications of Mad3 and Mad2 act in a concerted manner to maintain spindle checkpoint arrests.</p></div

What gastroenterologists should know about SARS–CoV 2 vaccine: World Endoscopy Organization perspective

BACKGROUND: The novel Coronavirus (SARS‐CoV‐2) has caused almost 2 million deaths worldwide. Both Food and Drug Administration and European Medicines Agency have recently approved the first COVID‐19 vaccines, and a few more are going to be approved soon. METHODS: Several different approaches have been used to stimulate the immune system in mounting a humoral response. As more traditional approaches are under investigation (inactivated virus vaccines, protein subunit vaccines, recombinant virus vaccines), more recent and innovative strategies have been tried (non‐replicating viral vector vaccines, RNA based vaccines, DNA based vaccines). RESULTS: Since vaccinations campaigns started in December 2020 in both the US and Europe, gastroenterologists will be one of the main sources of information regarding SARS‐CoV 2 vaccination for patients in their practice, including vulnerable patients such as those with Inflammatory Bowel Disease (IBD), patients with chronic liver disease, and GI cancer patients. CONCLUSIONS: Thus, we must ourselves be well educated and updated in order to provide unambiguous counseling to these categories of vulnerable patients. In this commentary, we aim to provide a comprehensive review of both approved COVID‐19 vaccines and the ones still under development, and explore potential risks, benefits and prioritization of vaccination

Pathological Changes in Pulmonary Circulation in Carbon Tetrachloride (ccl4)-Induced Cirrhotic Mice

Lack of an experimental model of portopulmonary hypertension (POPH) has been a major obstacle in understanding of pathophysiological mechanisms underlying the disease.We investigated the effects of CCl4-mediated cirrhosis on the pulmonary vasculature, as an initial step towards an improved understanding of POPH.Male C57BL/6 mice received intraperitoneal injection of either sterile olive oil or CCl4 3 times/week for 12 weeks. Cirrhosis and portal hypertension were confirmed by evidence of bridging fibrosis and nodule formation in CCl4-treated liver determined by trichrome/picrosirius red staining and an increase in spleen weight/body weight ratio, respectively. Staining for the oxidative stress marker, 4-hydroxynonenal (4-HNE), was strong in the liver but was absent in the lung, suggesting that CCl4 did not directly induce oxidative injury in the lung. Pulmonary acceleration time (PAT) and the ratio of PAT/pulmonary ejection time (PET) measured by echocardiography were significantly decreased in cirrhotic mice. Increase in right ventricle (RV) weight/body weight as well as in the weight ratio of RV/(left ventricle + septum) further demonstrated the presence of pathological changes in the pulmonary circulation in these mice. Histological examination revealed that lungs of cirrhotic mice have excessive accumulation of perivascular collagen and thickening of the media of the pulmonary artery.Collectively, our data demonstrate that chronic CCl4 treatment induces pathological changes in pulmonary circulation in cirrhotic mice. We propose that this murine cirrhotic model provides an exceptional tool for future studies of the molecular mechanisms mediating pulmonary vascular diseases associated with cirrhosis and for evaluation of novel therapeutic interventions