Soluble expression of recombinant midgut zymogen (native propeptide) proteases from the Aedes aegypti Mosquito Utilizing E. coli as a host

Biochemical and physiological characterization of Aedes aegypti midgut chymotrypsin

The Aedes aegypti mosquito is a vector of dengue, Zika, and chikungunya. The mosquito's reliance on blood facilitates the transmission of these viral pathogens to humans. Digestion of blood proteins depends on the biphasic expression of serine proteases, with trypsin-like activity contributing to most of the activity in the midgut. Other proteases found (serine collagenase- and chymotrypsin-like) are thought to contribute to digestion, but their roles are largely understudied. Thus, elucidating the activity and specific roles of all midgut proteases will help understand the complexity of the digestion process and help validate them as potential targets for the development of a new vector control strategy. Herein, we focused on characterizing the activity profile and role of Ae. aegypti chymotrypsin (AaCHYMO). Knockdown studies resulted in elimination and significant reduction of chymotrypsin-like activity in blood fed midgut extracts, while in vitro fluorescent and blood protein digestion assays revealed important substrate specificity differences. Interestingly, knockdown of AaCHYMO did not impact fecundity, indicating the presence of an intricate network of proteases working collectively to degrade blood proteins. Further, knockdown of the ecdysone receptor (EcR) led to a decrease in overall AaCHYMO expression and activity in the mosquito, which may play an important regulatory role.

Comprehensive proteolytic profiling of Aedes aegypti mosquito midgut extracts: Unraveling the blood meal protein digestion system

To sustain the gonotrophic cycle, the Aedes aegypti mosquito must acquire a blood meal from a human or other vertebrate host. However, in the process of blood feeding, the mosquito may facilitate the transmission of several bloodborne viral pathogens (e.g., dengue, Zika, and chikungunya). The blood meal is essential as it contains proteins that are digested into polypeptides and amino acid nutrients that are eventually used for egg production. These proteins are digested by several midgut proteolytic enzymes. As such, the female mosquito's reliance on blood may serve as a potential target for vector and viral transmission control. However, this strategy may prove to be challenging since midgut proteolytic activity is a complex process dependent on several exo- and endo-proteases. Therefore, to understand the complexity of Ae. aegypti blood meal digestion, we used Multiplex Substrate Profiling by Mass Spectrometry (MSP-MS) to generate global proteolytic profiles of sugar- and blood-fed midgut tissue extracts, along with substrate profiles of recombinantly expressed midgut proteases. Our results reveal a shift from high exoproteolytic activity in sugar-fed mosquitoes to an expressive increase in endoproteolytic activity in blood-fed mosquitoes. This approach allowed for the identification of 146 cleaved peptide bonds (by the combined 6 h and 24 h blood-fed samples) in the MSP-MS substrate library, and of these 146, 99 (68%) were cleaved by the five recombinant proteases evaluated. These reveal the individual contribution of each recombinant midgut protease to the overall blood meal digestion process of the Ae. aegypti mosquito. Further, our molecular docking simulations support the substrate specificity of each recombinant protease. Therefore, the present study provides key information of midgut proteases and the blood meal digestion process in mosquitoes, which may be exploited for the development of potential inhibitor targets for vector and viral transmission control strategies.

Biochemical and physiological characterization of Aedes aegypti midgut chymotrypsin

The Aedes aegypti mosquito is a vector of dengue, Zika, and chikungunya. The mosquito's reliance on blood facilitates the transmission of these viral pathogens to humans. Digestion of blood proteins depends on the biphasic expression of serine proteases, with trypsin-like activity contributing to most of the activity in the midgut. Other proteases found (serine collagenase- and chymotrypsin-like) are thought to contribute to digestion, but their roles are largely understudied. Thus, elucidating the activity and specific roles of all midgut proteases will help understand the complexity of the digestion process and help validate them as potential targets for the development of a new vector control strategy. Herein, we focused on characterizing the activity profile and role of Ae. aegypti chymotrypsin (AaCHYMO). Knockdown studies resulted in elimination and significant reduction of chymotrypsin-like activity in blood fed midgut extracts, while in vitro fluorescent and blood protein digestion assays revealed important substrate specificity differences. Interestingly, knockdown of AaCHYMO did not impact fecundity, indicating the presence of an intricate network of proteases working collectively to degrade blood proteins. Further, knockdown of the ecdysone receptor (EcR) led to a decrease in overall AaCHYMO expression and activity in the mosquito, which may play an important regulatory role.

Improving the Capstone Biochemistry Lab and Evolution to a Course-Based Undergraduate Research Experience: Lessons Learned from the COVID-19 Online Modality

The restructuring of an upper division biochemistry lab capstone course intended for biochemistry students with a range of laboratory experience was explored. A goal of the course was to give students practice with necessary skills in biochemical and biological techniques, especially for an entry level general position in biotechnology. The immediate impact of the online capstone course mandated by the COVID-19 pandemic limited students on learning essential hands-on research skills but evolved during the transition back to in-person instruction to include more elements of in-person practice. This article highlights the evolution of the capstone biochemistry lab to an in-person CURE capstone lab, with lessons learned and resources successfully used during the COVID-19 remote course. These include changes in the way information was disseminated, access to online resources, and modifications in student assessments. This article documents how course evolution resulted in a shift in pedagogical strategies leading to building a community of biochemistry learners that could be used to help college faculty in developing a CURE capstone lab.

MPEPE, a predictive approach to improve protein expression in E. coli based on deep learning

The expression of proteins in Escherichia coli is often essential for their characterization, modification, and subsequent application. Gene sequence is the major factor contributing expression. In this study, we used the expression data from 6438 heterologous proteins under the same expression condition in E. coli to construct a deep learning classifier for screening high- and low-expression proteins. In conjunction with conserved residue analysis to minimize functional disruption, a mutation predictor for enhanced protein expression (MPEPE) was proposed to identify mutations conducive to protein expression. MPEPE identified mutation sites in laccase 13B22 and the glucose dehydrogenase FAD-AtGDH, that significantly increased both expression levels and activity of these proteins. Additionally, a significant correlation of 0.46 between the predicted high level expression propensity with the constructed models and the protein abundance of endogenous genes in E. coli was also been detected. Therefore, the study provides foundational insights into the relationship between specific amino acid usage, codon usage, and protein expression, and is essential for research and industrial applications.

A Heterologous Viral Protein Scaffold for Chimeric Antigen Design: An Example PCV2 Virus Vaccine Candidate

Recombinant vaccines have low-cost manufacturing, regulatory requirements, and reduced side effects compared to attenuated or inactivated vaccines. In the porcine industry, post-weaning multisystemic disease syndrome generates economic losses, characterized by progressive weight loss and weakness in piglets, and it is caused by porcine circovirus type 2 (PCV2). We designed a chimeric antigen (Qm1) to assemble the main exposed epitopes of the Cap-PCV2 protein on the capsid protein of the tobacco necrosis virus (TNV). This design was based on the Cap-N-terminal of an isolated PCV2 virus obtained in Chile. The virus was characterized, and the sequence was clustered within the PCV2 genotype b clade. This chimeric protein was expressed as inclusion bodies in both monomeric and multimeric forms, suggesting a high-molecular-weight aggregate formation. Pigs immunized with Qm1 elicited a strong and specific antibody response, which reduced the viral loads after the PCV2 challenge. In conclusion, the implemented design allowed for the generation of an effective vaccine candidate. Our proposal could be used to express the domains or fragments of antigenic proteins, whose structural complexity does not allow for low-cost production in Escherichia coli. Hence, other antigen domains could be integrated into the TNV backbone for suitable antigenicity and immunogenicity. This work represents new biotechnological strategies, with a reduction in the costs associated with vaccine development.