Searching for proteins that interact with the ectodomain of CLEC9A, the critical cDC1 receptor involved in binding exposed actin on dead cells, Tullet and Tan et al. found that RNF41, a highly conserved ubiquitin ligase, bound CLEC9A in biochemical assays and in cells. Genetic knockdown revealed a regulatory role for RNF41 in antigen presentation. Ubiquitination by the RING-domain of RNF41 resulted in downmodulation of CLEC9A at steady state, but binding to actin from dead cells abrogated that regulation and shifted the path of dead cell antigen-loaded CLEC9A to early endosomes for presentation.
Contributed by Ed Fritsch
ABSTRACT: The dendritic cell receptor Clec9A facilitates processing of dead cell-derived antigens for cross-presentation and the induction of effective CD8(+) T cell immune responses. Here, we show that this process is regulated by E3 ubiquitin ligase RNF41 and define a new ubiquitin-mediated mechanism for regulation of Clec9A, reflecting the unique properties of Clec9A as a receptor specialized for delivery of antigens for cross-presentation. We reveal RNF41 is a negative regulator of Clec9A and the cross-presentation of dead cell-derived antigens by mouse dendritic cells. Intriguingly, RNF41 regulates the downstream fate of Clec9A by directly binding and ubiquitinating the extracellular domains of Clec9A. At steady-state, RNF41 ubiquitination of Clec9A facilitates interactions with ER-associated proteins and degradation machinery to control Clec9A levels. However, Clec9A interactions are altered following dead cell uptake to favor antigen presentation. These findings provide important insights into antigen cross-presentation and have implications for development of approaches to modulate immune responses.