Periodic Reporting for period 1 - PolTube (A molecular model of the microsporidian infection apparatus)
Periodo di rendicontazione: 2021-04-01 al 2022-09-30
Microsporidia are opportunistic fungal pathogens that infect organisms as evolutionarily divergent as protists and mammals. Due to their growing impact on the global food supply chain, the environment, and human health, these unusual spore-forming organisms have been classified as emerging pathogens of high priority. Intriguing cell biological features that are central to microsporidian infectivity and pose challenges to drug development are poorly understood. As energy parasites, microsporidia survive with the smallest eukaryotic genome and without classical mitochondria through an obligate intracellular lifestyle. A fascinating infection mechanism involving a long, hollow protein structure is essential for the environmental spore to efficiently invade hosts. The microsporidia-specific infection apparatus consists of several structural proteins that form the polar tube, which is used to inject the entire cytoplasm from the infectious spore into the host cell. The project PolTube aims to shed light on the intriguing features of microsporidia using structural biology techniques and provide new insights into the evolution, molecular specialization, and infection biology of these unique pathogens.
In the current funding period of PolTube, the main focus was to provide structural, mechanistic, and functional insights into the infection biology of Vairimorpha necatrix, a versatile microsporidian pathogen of lepidopterans. By using a combined approach of genomics, biochemistry, in-vivo methods, and structural biology techniques, we aimed to provide novel insights into microsporidia infection biology. We have obtained genome sequencing data and created a telomer-to-telomer assembly of a new eukaryotic genome, which provided a template for compositional analysis of biochemical samples of the polar tube using mass spectrometry. In addition, we have used single-particle cryo-electron microscopy to provide novel structural information on a highly compacted and inhibited eukaryotic proteasome, study an unusual lipid-protein tube polymer, and investigate the structure of a multidrug exporter.
The main results of this reporting period include genome sequencing information of a microsporidian pathogen and the discovery, structural and functional description of a novel inhibitory peptide, which simultaneously blocks all active sites of the microsporidian proteasome. We provide the first structure of the microsporidian proteasome, a prime target for antibiotics, and give insights into the specialization and evolution of a fascinating and understudied organism. Further, we deliver structural information of a factor blocking the microsporidian protein degradation machinery and provide an ideal template for future drug development.