A yeast model of FUS/TLS-dependent cytotoxicity.

FUS/TLS is a nucleic acid binding protein that, when mutated, can cause a subset of familial amyotrophic lateral sclerosis (fALS). Although FUS/TLS is normally located predominantly in the nucleus, the pathogenic mutant forms of FUS/TLS traffic to, and form inclusions in, the cytoplasm of affected spinal motor neurons or glia. Here we report a yeast model of human FUS/TLS expression that recapitulates multiple salient features of the pathology of the disease-causing mutant proteins, including nuclear to cytoplasmic translocation, inclusion formation, and cytotoxicity. Protein domain analysis indicates that the carboxyl-terminus of FUS/TLS, where most of the ALS-associated mutations are clustered, is required but not sufficient for the toxicity of the protein. A genome-wide genetic screen using a yeast over-expression library identified five yeast DNA/RNA binding proteins, encoded by the yeast genes ECM32, NAM8, SBP1, SKO1, and VHR1, that rescue the toxicity of human FUS/TLS without changing its expression level, cytoplasmic translocation, or inclusion formation. Furthermore, hUPF1, a human homologue of ECM32, also rescues the toxicity of FUS/TLS in this model, validating the yeast model and implicating a possible insufficiency in RNA processing or the RNA quality control machinery in the mechanism of FUS/TLS mediated toxicity. Examination of the effect of FUS/TLS expression on the decay of selected mRNAs in yeast indicates that the nonsense-mediated decay pathway is probably not the major determinant of either toxicity or suppression.

Pre-procedural serum albumin concentration is associated with length of stay, discharge destination, and 90-day mortality in patients after transcatheter aortic valve replacement.

Background: As visceral protein expression may influence outcomes in patients with cardiovascular disease, we investigated whether pre-procedural albumin concentration is associated with length of stay (LOS) and 90-day mortality after transcatheter aortic valve repair (TAVR). Methods: We retrospectively analyzed data from TAVR patients at our institution between January 2013 and December 2017. For all patients, baseline albumin concentration was assessed between one and four weeks before the procedure. To investigate the association between albumin concentration and outcomes, we performed regression analyses, controlling for Society of Thoracic Surgeons, New York Heart Association classification, and Kansas City Cardiomyopathy Questionnaire 12 scores. Results: Three hundred eighty patients were included in the analyses. Cox-proportional hazards regression showed that patients with albumin concentrations <3.5 g/dL were 80% more likely to have prolonged ICU LOS (HR 1.79; 95%CI 1.04-2.57, P = 0.03) and 70% more likely to have prolonged hospital LOS (HR 1.68; 95%CI 1.01-2.46, P = 0.04) compared to patients with albumin concentrations >3.5 g/dL. Logistic regression showed that patients with albumin concentrations <3.5 g/dL were four times more likely to not survive to 90 days (OR 3.94; 1.13-12.63, P = 0.03) after their TAVR compared to patients with albumin concentrations >3.5 g/dL. Conclusion: Our data suggest that patients with pre-procedural albumin concentrations <3.5 g/dL are at an increased risk of adverse outcomes after TAVR compared to patients with albumin concentrations ≥3.5 g/dL. Prospective studies are needed to determine whether risk stratification based on pre-procedural albumin can improve outcomes and whether targeted interventions can improve pre-procedural albumin concentrations in potential TAVR candidates.

Functional links between Aß toxicity, endocytic trafficking, and Alzheimer's disease risk factors in yeast.

Aß (beta-amyloid peptide) is an important contributor to Alzheimer's disease (AD). We modeled Aß toxicity in yeast by directing the peptide to the secretory pathway. A genome-wide screen for toxicity modifiers identified the yeast homolog of phosphatidylinositol binding clathrin assembly protein (PICALM) and other endocytic factors connected to AD whose relationship to Aß was previously unknown. The factors identified in yeast modified Aß toxicity in glutamatergic neurons of Caenorhabditis elegans and in primary rat cortical neurons. In yeast, Aß impaired the endocytic trafficking of a plasma membrane receptor, which was ameliorated by endocytic pathway factors identified in the yeast screen. Thus, links between Aß, endocytosis, and human AD risk factors can be ascertained with yeast as a model system.

Role of Inn1 and its interactions with Hof1 and Cyk3 in promoting cleavage furrow and septum formation in S. cerevisiae.

Cytokinesis requires coordination of actomyosin ring (AMR) contraction with rearrangements of the plasma membrane and extracellular matrix. In Saccharomyces cerevisiae, new membrane, the chitin synthase Chs2 (which forms the primary septum [PS]), and the protein Inn1 are all delivered to the division site upon mitotic exit even when the AMR is absent. Inn1 is essential for PS formation but not for Chs2 localization. The Inn1 C-terminal region is necessary for localization, and distinct PXXP motifs in this region mediate functionally important interactions with SH3 domains in the cytokinesis proteins Hof1 (an F-BAR protein) and Cyk3 (whose overexpression can restore PS formation in inn1Delta cells). The Inn1 N terminus resembles C2 domains but does not appear to bind phospholipids; nonetheless, when overexpressed or fused to Hof1, it can provide Inn1 function even in the absence of the AMR. Thus, Inn1 and Cyk3 appear to cooperate in activating Chs2 for PS formation, which allows coordination of AMR contraction with ingression of the cleavage furrow.