A genome-wide CRISPR functional survey of the human phagocytosis molecular machinery
Phagocytosis, the process of engulfing large particles by cells, is a multilayered biological activity driving tissue clearance and host defense. Dysregulation of phagocytosis is connected to autoimmunity, accumulation of toxic disease proteins, and increased risks for infections. Despite its importance and multiple roles, we lack a full understanding of the cellular machinery involved in executing and regulating the process, including the coordination with other cellular events. To create a functional map in human cells, we performed a reporter- and FACS-based genome-wide CRISPR/Cas9 knock-out screen that identified 716 genes. Mapping the gene hits to a comprehensive protein-protein interaction network annotated for functional cellular processes, allowed to highlight those protein complexes identified multiple times, to identify missing components of the cellular phagocytosis network, and to suggest functional partition among complexes. We validate complexes known to be involved, such as the Arp2/3 complex, the vacuolar-ATPase-Rag machinery, and the Wave-2 complex, as well as processes previously not or only poorly associated with phagocytosis. Among the novel, phagocytosis-relevant cellular functions validated are the oligosaccharyltransferase complex (MAGT1/SLC58A1, DDOST, STT3B, and RPN2) as well as the hypusine pathway (eIF5A, DHPS, and DOHH). Overall, our network of phagocytosis regulators and effectors maps elements of cargo uptake, cargo shuffling and cargo biotransformation through the cell, providing a valuable resource for the identification of potential novel drivers for diseases of the endo-lysosomal system. We further propose that our approach of mining and integrating publicly available protein-protein interaction data with datasets derived from reporter-based genome-wide screens offers a broadly applicable way to functionally map biological processes onto the molecular machinery of the cell. Summary blurbThe validation and interpretation of a FACS reporter-based genome-wide CRISPR/Cas9 knock-out screen through protein-protein interaction data yields a comprehensive view of the molecular network regulating and executing phagocytosis in human cells.