Disordered regions in the IRE1α ER lumenal domain mediate its stress-induced clustering.

Conserved signaling cascades monitor protein-folding homeostasis to ensure proper cellular function. One of the evolutionary conserved key players is IRE1, which maintains endoplasmic reticulum (ER) homeostasis through the unfolded protein response (UPR). Upon accumulation of misfolded proteins in the ER, IRE1 forms clusters on the ER membrane to initiate UPR signaling. What regulates IRE1 cluster formation is not fully understood. Here, we show that the ER lumenal domain (LD) of human IRE1α forms biomolecular condensates in vitro. IRE1α LD condensates were stabilized both by binding to unfolded polypeptides as well as by tethering to model membranes, suggesting their role in assembling IRE1α into signaling-competent stable clusters. Molecular dynamics simulations indicated that weak multivalent interactions drive IRE1α LD clustering. Mutagenesis experiments identified disordered regions in IRE1α LD to control its clustering in vitro and in cells. Importantly, dysregulated clustering of IRE1α mutants led to defects in IRE1α signaling. Our results revealed that disordered regions in IRE1α LD control its clustering and suggest their role as a common strategy in regulating protein assembly on membranes.

A Comparative Molecular Dynamics Study of Selected Point Mutations in the Shwachman-Bodian-Diamond Syndrome Protein SBDS.

The Shwachman-Diamond Syndrome (SDS) is an autosomal recessive disease whose majority of patients display mutations in a ribosome assembly protein named Shwachman-Bodian-Diamond Syndrome protein (SBDS). A specific therapy for treating this rare disease is missing, due to the lack of knowledge of the molecular mechanisms responsible for its pathogenesis. Starting from the observation that SBDS single-point mutations, localized in different domains of the proteins, are responsible for an SDS phenotype, we carried out the first comparative Molecular Dynamics simulations on three SBDS mutants, namely R19Q, R126T and I212T. The obtained 450-ns long trajectories were compared with those returned by both the open and closed forms of wild type SBDS and strongly indicated that two distinct conformations (open and closed) are both necessary for the proper SBDS function, in full agreement with recent experimental observations. Our study supports the hypothesis that the SBDS function is governed by an allosteric mechanism involving domains I and III and provides new insights into SDS pathogenesis, thus offering a possible starting point for a specific therapeutic option.

Alcohol consumption after laparoscopic sleeve gastrectomy: 1-year results.

INTRODUCTION: Laparoscopic sleeve gastrectomy (SG) represents, at present, the most performed bariatric procedure worldwide with excellent long-term results on weight loss and comorbidities control. After the gastrectomy procedure, together with hormonal modification, several changes in taste and habits occur, including the potential modification in alcohol consumption. The aim of this prospective study was to determine the frequency and the amount of alcohol use before and after SG using a modified version of the Alcohol Use Disorder Identification Test (AUDIT) at 1-year follow-up and eventually to evaluate relationships between different ages and sexes. MATERIALS AND METHODS: A total of 142 patients were prospectively enrolled and evaluated before and 1 year after SG with a modified AUDIT. The exclusion criteria were as follows: history of alcohol abuse, presence of psychopathology or cognitive impairments, diabetes mellitus type II decompensated, or previous gastrointestinal, liver, and pancreatic resective surgery. Subgroup analyses were performed between male and female and between under and over 40 years old. RESULTS: The median AUDIT score decreased from 2.70 (range 1-18) before surgery to 1.38 (range 1-7) after 1 year of SG, indicating a marked reduction in alcohol use. The most consumed alcoholic drink was beer (36.6%/n = 52) while after surgery the consumption of beer decreased considerably (21.1%/n = 30). The frequency of alcohol consumption also decreased: at baseline 45% of patients consumed alcoholic drinks "from 2 to 4 times per month", whereas 26 and 39.4% consumed alcohol "never" and "less than once a month," respectively. After surgery, nobody consumed more then six alcoholic drinks. No differences were found between the subgroups in terms of alcohol consumption and social behavior. CONCLUSIONS: The alcohol preference is modified and decreased 1 year after SG and this could be related to the strict nutritional follow-up and to the hormonal changes. Studies with large samples and long-term follow-up are needed to confirm our data. LEVEL OF EVIDENCE: IV.