Vav proteins are key regulators of Card9 signaling for innate antifungal immunity

Fungal infections are major causes of morbidity and mortality, especially in immunocompromised individuals. The innate immune system senses fungal pathogens through a family of Syk-coupled C-type lectin receptors (CLRs), which signal through the conserved immune adapter Card9. Although Card9 complexes are essential for antifungal defense in humans and mice, the mechanisms that couple CLR-proximal events to Card9 control are not well defined. Here, using a proteomic approach, we identified Vav proteins as key activators of the Card9 pathway. Vav1, Vav2 and Vav3 cooperate downstream of Dectin-1, Dectin-2 and Mincle to selectively engage Card9 for NF-?B control and proinflammatory gene transcription but are not involved in MAPK activation. Although Vav family members show functional redundancy, Vav1/2/3 triple-deficient cells are severely impaired for NF-?B and cytokine responses upon stimulation with CLR agonists or hyphae, and Vav1/2/3-/- mice phenocopy Card9-/- animals with extreme susceptibility to fungi and rapid mortality upon Candida albicans infection. In this context, Vav3 is the single most important Vav in mice, and a polymorphism in human VAV3 is associated with susceptibility to candidemia in patients. Our results reveal a molecular mechanism for CLR-mediated Card9 regulation that controls innate immunity to fungal infections. Overall design: RNA profiles of unstimulated or Curdlan-stimulated bone marrow-derived dendritic cells (BMDCs) from wild type (WT) and Vav1/2/3-/- (VAV KO) mice were generated by deep sequencing, in triplicate, using Illumina HiSeq 2000.

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Roth S, Bergmann H, Jaeger M, Yeroslaviz A, Neumann K, Koenig PA, Prazeres da Costa C, Vanes L, Kumar V, Johnson M, Menacho-Márquez M, Habermann B, Tybulewicz VL, Netea M, Bustelo XR, Ruland J