Genome-wide screen identifies new set of genes for improved heterologous laccase expression in Saccharomyces cerevisiae.

The yeast Saccharomyces cerevisiae is widely used as a host cell for recombinant protein production due to its fast growth, cost-effective culturing, and ability to secrete large and complex proteins. However, one major drawback is the relatively low yield of produced proteins compared to other host systems. To address this issue, we developed an overlay assay to screen the yeast knockout collection and identify mutants that enhance recombinant protein production, specifically focusing on the secretion of the Trametes trogii fungal laccase enzyme. Gene ontology analysis of these mutants revealed an enrichment of processes including vacuolar targeting, vesicle trafficking, proteolysis, and glycolipid metabolism. We confirmed that a significant portion of these mutants also showed increased activity of the secreted laccase when grown in liquid culture. Notably, we found that the combination of deletions of OCA6, a tyrosine phosphatase gene, along with PMT1 or PMT2, two genes encoding ER membrane protein-O-mannosyltransferases involved in ER quality control, and SKI3, which encode for a component of the SKI complex responsible for mRNA degradation, further increased secreted laccase activity. Conversely, we also identified over 200 gene deletions that resulted in decreased secreted laccase activity, including many genes that encode for mitochondrial proteins and components of the ER-associated degradation pathway. Intriguingly, the deletion of the ER DNAJ co-chaperone gene SCJ1 led to almost no secreted laccase activity. When we expressed SCJ1 from a low-copy plasmid, laccase secretion was restored. However, overexpression of SCJ1 had a detrimental effect, indicating that precise dosing of key chaperone proteins is crucial for optimal recombinant protein expression. This study offers potential strategies for enhancing the overall yield of recombinant proteins and provides new avenues for further research in optimizing protein production systems.

Strategies and outcomes of extracorporeal membrane oxygenation use in peripartum patients: a single institution experience.

BACKGROUND: Extracorporeal membrane oxygenation (ECMO) use in peripartum patients is rare, and there is a gap in the literature on the outcomes and guidance on using ECMO in peripartum patients. This study describes ECMO strategies our institution uses for peripartum patients and reports outcomes of ECMO use in peripartum patients with respiratory and/or cardiac failure. METHODS: A case series of all peripartum patients, defined as pregnant or up to 6 weeks after delivery of an infant >20 weeks gestation, from 2018 to 2023 from a single center requiring ECMO support. Patients were included if ECMO was initiated in the setting of cardiac, pulmonary, or combined failure. Patient demographics, operative details, ECMO data, and adverse outcomes for maternal, fetus, and neonates were all collected. RESULTS: Eighteen patients met the inclusion criteria. The cohort had a mean maternal age of 30.7 years old and was racially diverse. A majority of this cohort tested positive for COVID-19 (n = 10, 55%). ECMO was a bridge to recovery for all patients, of whom 14 (78%) were discharged out of the hospital alive. No patients received transplantation or a durable mechanical device. The most common complications were infection (25%) and postpartum hemorrhage (22%). CONCLUSIONS: ECMO use in peripartum patients in a single tertiary center was associated with a high survival rate. Furthermore, a strong multidisciplinary team, careful reevaluation of clinical trajectory, and consideration of complications and risks associated with using ECMO in peripartum patients are possible frameworks to use when challenged with critically ill peripartum patients.

Identification of newly translated thermo-sensitive proteins using pulse SILAC mass spectrometry and the GAL promoter system.

Some newly translated proteins are more susceptible to misfolding and aggregation upon heat shock in comparison to other proteins. To study these newly translated thermo-sensitive proteins on a proteomic scale, we present here a protocol that combines pulse-SILAC with biochemical fractionation for mass spectrometry analysis, followed by an orthogonal validation protocol for selected candidates using the GAL promoter system in Saccharomyces cerevisiae. This approach can be further developed to study other stresses and specific post-translational modifications or adapted to mammalian cells. For complete details on the use and execution of this protocol, please refer to Zhu et al. (2022).1.

Pulse labeling reveals the tail end of protein folding by proteome profiling.

Accurate and efficient folding of nascent protein sequences into their native states requires support from the protein homeostasis network. Herein we probe which newly translated proteins are thermo-sensitive, making them susceptible to misfolding and aggregation under heat stress using pulse-SILAC mass spectrometry. We find a distinct group of proteins that is highly sensitive to this perturbation when newly synthesized but not once matured. These proteins are abundant and highly structured. Notably, they display a tendency to form ß sheet secondary structures, have more complex folding topology, and are enriched for chaperone-binding motifs, suggesting a higher demand for chaperone-assisted folding. These polypeptides are also more often components of stable protein complexes in comparison with other proteins. Combining these findings suggests the existence of a specific subset of proteins in the cell that is particularly vulnerable to misfolding and aggregation following synthesis before reaching the native state.

Identification of active sonochemical zones in a triple frequency ultrasonic reactor via physical and chemical characterization techniques.

Coupling multiple frequencies in ultrasonic systems is one of the highly desired area of research for sonochemists, as it is known for producing synergistic effects on various ultrasonic reactions. In this study, the characteristics of a hexagonal-shaped triple frequency ultrasonic reactor with the combination frequencies of 28, 40 and 70kHz were studied. The results showed that uniform temperature increment was achieved throughout the reactor at all frequency combinations. On the other hand, sonochemiluminescence emission and degradation rate of Rhodamine B varies throughout different areas of the reactor, indicating the presence of acoustic 'hot spots' at certain areas of the reactor. Also, coupling dual and triple frequencies showed a decrease in the hydroxyl radical (OH) production, suggesting probable wave cancelling effect in the system. The results can therefore be served as a guide to optimize the usage of a triple frequency ultrasonic reactor for future applications.