in vitro ubiquitination by E3 ligase Cbl-b

Fungal infections claim an estimated 1.5 million lives every year. Mechanisms that protect from fungal infections are still elusive. Recognition of fungal pathogens relies on C-type lectin receptors (CLR) and their downstream signaling kinase SYK. Here we report that the E3-ubiquitin-ligase CBL-B controls proximal C-type lectin receptor signaling in macrophages and dendritic cells. We show that CBL-B associates with SYK and ubiquitinates SYK, Dectin-1, and Dectin-2 upon fungal recognition. Functionally, CBL-B deficiency results in increased inflammasome activation, enhanced reactive oxygen species production, and increased fungal killing. Genetic deletion of Cblb protects mice from morbidity caused by cutaneous infection and markedly improves survival upon a lethal systemic infection with Candida albicans. Based on these findings, we engineered a cell-permeable CBL-B inhibitory peptide that protects mice from lethal C. albicans infections. We thus describe a key role for Cblb in the regulation of innate anti-fungal immunity and establish a novel paradigm for the treatment of fungal sepsis.