[대학원 생명과학과 세미나 안내]
연사 : 이헌상 교수(고려대학교 생명과학과)
연제 : A functional genomics approach to map extracellular interactions
일시 : 2022년 05월 27일 (금) 오후 4시 30분
장소 : 대면 및 온라인 화상 강의로 진행됩니다.
Abstract
Part 1. Development of a novel high-throughput receptor-ligand interaction platform.
It is estimated that cells encode for about 3,000 secreted proteins and 2,500 cell surface receptors. Many of secreted proteins act as signaling molecules, such as hormones, growth factors, and other autocrine/paracrine factors. In particular, stem cell secretes many proteins with regeneration capacity. These factors act by triggering a signaling cascade once bound by a cell surface cognate receptor on a target cell. Intuitively, to understand mechanisms underlying these biological processes, secreted proteins need to be paired to their cognate receptors. What is more, it is also a critical step in designing therapeutics, with about 60% of drugs targeting cell surface receptors. However, there are no easily scalable methods for studying receptor/ligand interactions in an unbiased fashion and consequently, a substantial fraction of receptors and ligands remain orphans.
Here, we established a high-throughput receptor-ligand screening platform by combining exotoxin-based fusion protein toxins with genome-scale/cell surfaceome-scale CRISPR-Cas9 screens. The rationale was to generate a recombinant toxin with its native receptor-binding domain replaced with a secreted ligand and utilize it to treat a genome-wide/cell surfaceome-wide pool of knockout cells generated by CRISPR-Cas9. Cells that lack the cognate receptor conferred resistance to the recombinant toxin treatment and identified by next-gen sequencing. Moreover, screens also revealed receptor maturation factors required for their cell surface expression. The developed screening platform is currently being used to systematically decode the extracellular receptor-ligand interaction network.
Part 2. Identification of a host receptor for C.sordelli lethal toxin TcsL
Clostridium sordellii lethal toxin (TcsL) is responsible for an almost invariably lethal toxic shock syndrome associated with gynecological C. sordellii infections. Here, using CRISPR/Cas9 screening, we identify semaphorins SEMA6A and SEMA6B as TcsL receptors. We show with cryo-EM that TcsL uses the same interface to bind SEMA6A that the highly related C. difficile TcdB toxin uses to bind Frizzled receptors. Remarkably, reciprocal mutations in this evolutionarily divergent surface are sufficient to switch receptor specificity between the toxins. We also demonstrate that soluble SEMA6A fragment can protect mice from TcsL-induced edema, validating the physiological role of SEMA6A in toxic shock syndrome and highlighting a potential strategy to block this otherwise untreatable lethal disease.