The protein segregase VCP/p97 promotes host antifungal defense via regulation of SYK activation.

Abstract

C-type lectin receptors (CLRs) are essential to execute host defense against fungal infection. Nevertheless, a comprehensive understanding of the molecular underpinnings of CLR signaling remains a work in progress. Here, we searched for yet-to-be-identified tyrosine-phosphorylated proteins in Dectin-1 signaling and linked the stress-response protein valosin containing protein (VCP)/p97 to Dectin-1 signaling. Knockdown of VCP expression or chemical inhibition of VCP's segregase activity dampened Dectin-1-elicited SYK activation in BMDMs and BMDCs, leading to attenuated expression of proinflammatory cytokines/chemokines such as TNF-α, IL-6 and CXCL1. Biochemical analyses demonstrated that VCP and its cofactor UFD1 form a complex with SYK and its phosphatase SHP-1 following Dectin-1 ligation, and knockdown of VCP led to a more prominent SYK and SHP-1 association. Further, SHP-1 became polyubiquitinated upon Dectin-1 activation, and VCP or UFD1 overexpression accelerated SHP-1 degradation. Conceivably, VCP may promote Dectin-1 signaling by pulling the ubiquitinated SHP-1 out of the SYK complex for degradation. Finally, genetic ablation of VCP in the neutrophil and macrophage compartment rendered the mice highly susceptible to infection by Candida albicans, an observation also phenocopied by administering the VCP inhibitor. These results collectively demonstrate that VCP is a previously unappreciated signal transducer of the Dectin-1 pathway and a crucial component of antifungal defense, and suggest a new mechanism regulating SYK activation.