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Biology subjects

Mitchell, U.

Publications and source records attributed to Mitchell, U..

2 recordsLinked to original sources

High-Throughput De Novo Protein Design Yields Novel Immunomodulatory Agonists

Cytokines regulate cell behavior by bringing together specific receptor subunits to trigger downstream signaling. Designed molecules that bring together non-natural receptor pairs could have novel signaling responses and cell specificities. We present a high-throughput de-novo design approach to create novel cytokines by generating and fusing pairs of computationally designed binders. By combining 33 designed receptor-binding domains, we generated over a thousand potential de novo designed "Novokines", of which 75 activated pSTAT signaling in peripheral blood mononuclear cells. We characterized 18 of these, including new pairings of established common receptors, cross-family pairings such as TrkA-{gamma}common, and a series of pairings with interferon receptor-1 (IFNAR1), revealing that IFNAR1 can function as a versatile common receptor similar to {gamma}common or {beta}common. We identify novokines that drive monocyte proliferation, T cell survival and CD4+ T cell-specific proliferation. Our framework provides a blueprint for expanding the understanding of cytokine signaling and generating novel therapeutic proteins.

synthetic biology↗

A conserved electron transport chain sensitizes Bacteroides to a pore-forming type VI secretion toxin

Data suggest that antagonism between bacteria is prevalent within the gut microbiome. Such antagonism could have profound consequences on the fitness of species; however, the susceptibility determinants to even the most pervasive antagonistic factors in this ecosystem remain incompletely understood. Here, we screened for genetic factors that impact the susceptibility of Bacteroides to type VI secretion system (T6SS)-delivered toxins. This revealed that the Bte2 family of pore-forming toxins, which are widespread in B. fragilis and other human gut-associated Bacteroidales, strictly require the H+/Na+-translocating ferredoxin:NAD+ reductase (Rnf) electron transport chain within target cells in order to intoxicate. In Bacteriodes, the precise metabolic role of the conserved Rnf pathway has not been defined. We establish that the Rnf complex is important for redox balancing within cells utilizing sugars derived from dietary fiber and is critical for fitness in vivo. Surprisingly, we find that while the intact Rnf membrane complex is required for Bte2 intoxication, Rnf-catalyzed electron transport is dispensable. We propose that the Rnf complex facilitates Bte2 membrane insertion, leading to intoxication via membrane depolarization. Our data suggest that T6SS toxins may avoid collateral damage within a complex ecosystem by recognizing discriminatory features of competitor species. SignificancePathways for interbacterial antagonism are prevalent in the gut microbiome. The breadth of targeting and specificity determinants of these systems remain largely uncharacterized. We discovered that a widespread pore-forming toxin produced by gut Bacteroidales requires the conserved Rnf protein complex in target organisms. Although this complex is dispensable during in vitro growth, we show it is required for Bacteroides fitness during colonization of the mammalian gut. Our data support a model in which transient interaction between the toxin and Rnf enables rearrangement of the protein, facilitating membrane insertion. Related toxins found in Proteobacteria lack the requirement for Rnf, suggesting that competition between Bacteroidales species in the gut may be driving specialization of their antibacterial toxins.

microbiology↗