Dendritic cells (DCs) are innate immune cells with the specialized capacity to capture and present antigens to T cells for the initiation and regulation of adaptive immune responses. Clec9A is a DC receptor that enables recognition and processing of dead/damaged cells via exposed actin filaments and facilitates the cross-priming of cytotoxic T cells with dead cell-derived antigens. This process is integral for the induction ofappropriate anti-viral and anti-tumour immune responses.However, the mechanisms that govern dead cell processing and cross-presentation by Clec9A are poorly understood.
Our research has identified that the Clec9A extracellular domain interacts with the E3 ubiquitin ligase, RNF41. RNF41 regulates Clec9A through ubiquitination and subsequent proteasomal degradation. Furthermore, this process appears to be mediated by the ER-associated degradation (ERAD) pathway. While ERAD is traditionally associated with protein quality control at the ER through the recognition, ubiquitination and proteasomal degradation of misfolded proteins, it has become increasingly apparent that the ERAD pathway is also important for regulatingreceptorexpression levels at the ER. Our proteomics analysis of Clec9A has determined that the Clec9A-RNF41 complex selectively interacts with several ER-associated proteins. We are investigating the role of these novel interactions in the regulation of Clec9A for both newly synthesized Clec9A in the ER and following dead cell binding and internalisation from the cell surface. These novel Clec9A-RNF41 interacting proteins may present a pathway that enables RNF41 to bind and ubiquitinate Clec9A to regulate Clec9A receptor levels within DCs, and thus play an important role in modulating adaptive immune responses to infected cells or tumours.