Inhibition of CBLB protects from lethal Candida albicans sepsis


Fungal infections claim an estimated 1.5 million lives each year. Mechanisms that protect from fungal infections are still elusive. Recognition of fungal pathogens relies on C-type lectin receptors (CLRs) and their downstream signaling kinase SYK. Here we report that the E3 ubiquitin ligase CBLB controls proximal CLR signaling in macrophages and dendritic cells. We show that CBLB associates with SYK and ubiquitinates SYK, dectin-1, and dectin-2 after fungal recognition. Functionally, CBLB 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 after a lethal systemic infection with Candida albicans. On the basis of these findings, we engineered a cell-permeable CBLB inhibitory peptide that protects mice from lethal C. albicans infections. We thus describe a key role for Cblb in the regulation of innate antifungal immunity and establish a novel paradigm for the treatment of fungal sepsis.

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Figure 1: Cblb regulates antifungal immunity.
Figure 2: Cblb in immune cells protects against fungal pathology.
Figure 3: Cblb controls antifungal activities of dendritic cells and macrophages.
Figure 4: Increased CLR-mediated signaling in the absence of Cblb.
Figure 5: CBLB ubiquitinates SYK.
Figure 6: CBLB inhibition enhances antifungal immunity.

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We thank all members of the Penninger laboratory for helpful discussions and technical support. We thank all members of the IMP-IMBA Biooptics service facility, especially G. Schmauss and T. Lendl, for assistance in cell sorting and image quantification. We also thank A. Piszczek and M. Zeba from the Vienna Biocenter Core Facilities (VBCF) for excellent histopathology services, and K. Mechtler, R. Imre, and M. Madalinski from the Protein Biochemistry facility for providing excellent mass spectrometry and peptide synthesis services. This work was supported by a consolidator ERC grant (F.I.), the EC FP7 project 'FUNGITECT' (K.K.), the FWF project P-25333 (K.K.), a Marie-Curie 'Innovative Training Networks' ImResFun grant (contract MC-ITN-606786; K.K.), an Advanced ERC grant (J.M.P.), an 'Era of Hope/Innovator Award' (J.M.P.), a Helmsley foundation VEO–IBD network grant (J.M.P.), and the Austrian Academy of Sciences (J.M.P.).

Author information

G.W., F.Z., K.K., and J.M.P. designed experiments; F.Z., I.K., and R.A.W. performed western blotting and immunoprecipitation experiments; R.A.W. performed immunohistochemistry; F.Z. performed Candida spp. and L. monocytogenes systemic infections, ELISAs, and ROS, caspase-8, and C. albicans killing assays; F.Z. and G.W. performed C. albicans skin infection experiments; G.W. and F.Z. performed qPCR; G.W. and L.T. performed flow cytometry; G.W. designed the TKB binding Antennapedia–SYK fusion peptide; T.A. and F.I. performed and analyzed in vitro ubiquitination assays; A.K. performed histopathologic analyses; W.Y.L. provided CblbC373A/C373A mice; G.B. and F.F. provided recombinant CBLB29–483 and Cys373Ala CBLB29–483; J.M.P. and K.K. supervised the study; and G.W. and J.M.P. coordinated the study and wrote the manuscript.

Correspondence to Karl Kuchler or Josef M Penninger.

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J.M.P., G.W., F.Z., and K.K. are inventors on a patent application describing the use of a TKB binding peptide as a therapeutic for the modulation of CBLB-regulated immune responses.

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Wirnsberger, G., Zwolanek, F., Asaoka, T. et al. Inhibition of CBLB protects from lethal Candida albicans sepsis. Nat Med 22, 915–923 (2016) doi:10.1038/nm.4134

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