LowTempGAL: a highly responsive low temperature-inducible GAL system in Saccharomyces cerevisiae.

Temperature is an important control factor for biologics biomanufacturing in precision fermentation. Here, we explored a highly responsive low temperature-inducible genetic system (LowTempGAL) in the model yeast Saccharomyces cerevisiae. Two temperature biosensors, a heat-inducible degron and a heat-inducible protein aggregation domain, were used to regulate the GAL activator Gal4p, rendering the leaky LowTempGAL systems. Boolean-type induction was achieved by implementing a second-layer control through low-temperature-mediated repression on GAL repressor gene GAL80, but suffered delayed response to low-temperature triggers and a weak response at 30°C. Application potentials were validated for protein and small molecule production. Proteomics analysis suggested that residual Gal80p and Gal4p insufficiency caused suboptimal induction. 'Turbo' mechanisms were engineered through incorporating a basal Gal4p expression and a galactose-independent Gal80p-supressing Gal3p mutant (Gal3Cp). Varying Gal3Cp configurations, we deployed the LowTempGAL systems capable for a rapid stringent high-level induction upon the shift from a high temperature (37-33°C) to a low temperature (≤30°C). Overall, we present a synthetic biology procedure that leverages 'leaky' biosensors to deploy highly responsive Boolean-type genetic circuits. The key lies in optimisation of the intricate layout of the multi-factor system. The LowTempGAL systems may be applicable in non-conventional yeast platforms for precision biomanufacturing.

Dysregulation of tyrosinase activity: a potential link between skin disorders and neurodegeneration.

OBJECTIVES: The co-occurrence of melanoma and Parkinson's disease (PD) is higher than expected. We review the relationship between melanoma and PD, then proffer a hypothesis of how dysregulated human tyrosinase could be involved in both diseases via the loss of dopamine and neuromelanin-positive neurons in PD and the genesis alterations in melanin content during melanoma. KEY FINDINGS: There are a surprising number of links between skin disorders and neurodegenerative diseases. Some risk factors related to the co-occurrence of PD and melanoma have been extensively investigated over the past 15 years. It has been proposed that human tyrosinase, an enzyme participating in the biosynthesis of neuromelanin in the brain and of melanin in the skin, plays a role. Abnormally dysregulated human tyrosinase impacts the genesis and progression of melanoma and PD. SUMMARY: The dual role of human tyrosinase places it as the potential critical link between these seemingly distinct conditions. Detecting and monitoring human tyrosinase activity in the progression of melanoma and PD opens new opportunities for early diagnosis and treatment of both diseases.

Tyrosinase inhibitors as potential antibacterial agents.

Tyrosinase is a copper-containing enzyme that catalyzes the biosynthesis of melanin. This enzyme is present in bacteria, fungi, plants and animals, and plays multiple roles in pigmentation, wound healing, radiation protection, primary immune responses and the undesirable browning of fruits and vegetables. Selective tyrosinase inhibitors hence have potential application in diverse areas of agriculture, cosmetics and pharmaceuticals. In the past decade many natural and synthetic tyrosinase inhibitors have been evaluated, with many reported to also possess intrinsic antibacterial activity. Further, the enzyme product melanin has been shown to compromise the activity of traditional antibiotics. Due to the antibiotic resistance crisis and the slow development of new antibiotics, tyrosinase inhibitors may have potential for development of novel antimicrobials or antibiotic adjuvants that enhance activity of incumbent drugs. This review focuses on the antibacterial activity of natural and synthetic tyrosinase inhibitors reported in the past ten years and explores the possibilities for synergism of anti-tyrosinase with anti-bacterials.

Development of Polyelectrolyte Complexes for the Delivery of Peptide-Based Subunit Vaccines against Group A Streptococcus.

Peptide subunit vaccines hold great potential compared to traditional vaccines. However, peptides alone are poorly immunogenic. Therefore, it is of great importance that a vaccine delivery platform and/or adjuvant that enhances the immunogenicity of peptide antigens is developed. Here, we report the development of two different systems for the delivery of lipopeptide subunit vaccine (LCP-1) against group A streptococcus: polymer-coated liposomes and polyelectrolyte complexes (PECs). First, LCP-1-loaded and alginate/trimethyl chitosan (TMC)-coated liposomes (Lip-1) and LCP-1/alginate/TMC PECs (PEC-1) were examined for their ability to trigger required immune responses in outbred Swiss mice; PEC-1 induced stronger humoral immune responses than Lip-1. To further assess the adjuvanting effect of anionic polymers in PECs, a series of PECs (PEC-1 to PEC-5) were prepared by mixing LCP-1 with different anionic polymers, namely alginate, chondroitin sulfate, dextran, hyaluronic acid, and heparin, then coated with TMC. All produced PECs had similar particle sizes (around 200 nm) and surface charges (around + 30 mV). Notably, PEC-5, which contained heparin, induced higher antigen-specific systemic IgG and mucosal IgA titers than all other PECs. PEC systems, especially when containing heparin and TMC, could function as a promising platform for peptide-based subunit vaccine delivery for intranasal administration.

Recent Advances in the Development of Peptide Vaccines and Their Delivery Systems Against Group A Streptococcus.

Group A Streptococcus (GAS) infection can cause a variety of diseases in humans, ranging from common sore throats and skin infections, to more invasive diseases and life-threatening post-infectious diseases, such as rheumatic fever and rheumatic heart disease. Although research has been ongoing since 1923, vaccines against GAS are still not available to the public. Traditional approaches taken to develop vaccines for GAS failed due to poor efficacy and safety. Fortunately, headway has been made and modern subunit vaccines that administer minimal bacterial components provide an opportunity to finally overcome previous hurdles in GAS vaccine development. This review details the major antigens and strategies used for GAS vaccine development. The combination of antigen selection, peptide epitope modification and delivery systems have resulted in the discovery of promising peptide vaccines against GAS; these are currently in preclinical and clinical studies.