Expression, purification and preliminary crystallographic analysis of Drosophila melanogaster lysosomal α-mannosidase

Equi-MOI ratio for rapid baculovirus-mediated multiprotein co-expression in insect cells integrating selenomethionine for structural studies

Proteins often co-exist as multicomponent assemblies, making their co-expression essential in recombinant production processes. The baculovirus expression vector system is commonly used to produce recombinant multiprotein complexes mostly for structural and functional studies. Although AI-enhanced tools, such as AlphaFold, have revolutionized protein structure prediction, solving the phase problem remains the most significant challenge in X-ray crystallography for determining entirely novel, dynamic, or complex protein structures. To address this challenge, the early incorporation of selenomethionine into native proteins during production is especially advantageous for facilitating experimental phasing. Here, we describe a fast, effective, and versatile research protocol that uniquely combines these two challenging features. The principle of this method is based on using co-infection of several recombinant baculoviruses in so-called equal multiplicity of infection (MOI) or equi-MOI ratio, while at the same time, the balanced selenomethionine incorporation takes place to allow for an accelerated workflow. The delicate balance between individual conditions for producing selenomethionine-incorporated multiprotein complexes with high efficiency has been developed over several years of studying protein complexes; therefore, many useful tips and tricks are provided as well. Moreover, this protocol is straightforward to implement in any wet lab.

Combined Transcriptomic and Proteomic Analysis of Perk Toxicity Pathways

In Drosophila, endoplasmic reticulum (ER) stress activates the protein kinase R-like endoplasmic reticulum kinase (dPerk). dPerk can also be activated by defective mitochondria in fly models of Parkinson's disease caused by mutations in pink1 or parkin. The Perk branch of the unfolded protein response (UPR) has emerged as a major toxic process in neurodegenerative disorders causing a chronic reduction in vital proteins and neuronal death. In this study, we combined microarray analysis and quantitative proteomics analysis in adult flies overexpressing dPerk to investigate the relationship between the transcriptional and translational response to dPerk activation. We identified tribbles and Heat shock protein 22 as two novel Drosophila activating transcription factor 4 (dAtf4) regulated transcripts. Using a combined bioinformatics tool kit, we demonstrated that the activation of dPerk leads to translational repression of mitochondrial proteins associated with glutathione and nucleotide metabolism, calcium signalling and iron-sulphur cluster biosynthesis. Further efforts to enhance these translationally repressed dPerk targets might offer protection against Perk toxicity.

Human recombinant lysosomal enzymes produced in microorganisms

Lysosomal storage diseases (LSDs) are caused by accumulation of partially degraded substrates within the lysosome, as a result of a function loss of a lysosomal protein. Recombinant lysosomal proteins are usually produced in mammalian cells, based on their capacity to carry out post-translational modifications similar to those observed in human native proteins. However, during the last years, a growing number of studies have shown the possibility to produce active forms of lysosomal proteins in other expression systems, such as plants and microorganisms. In this paper, we review the production and characterization of human lysosomal proteins, deficient in several LSDs, which have been produced in microorganisms. For this purpose, Escherichia coli, Saccharomyces cerevisiae, Pichia pastoris, Yarrowia lipolytica, and Ogataea minuta have been used as expression systems. The recombinant lysosomal proteins expressed in these hosts have shown similar substrate specificities, and temperature and pH stability profiles to those produced in mammalian cells. In addition, pre-clinical results have shown that recombinant lysosomal enzymes produced in microorganisms can be taken-up by cells and reduce the substrate accumulated within the lysosome. Recently, metabolic engineering in yeasts has allowed the production of lysosomal enzymes with tailored N-glycosylations, while progresses in E. coli N-glycosylations offer a potential platform to improve the production of these recombinant lysosomal enzymes. In summary, microorganisms represent convenient platform for the production of recombinant lysosomal proteins for biochemical and physicochemical characterization, as well as for the development of ERT for LSD.