Ubiquitous glycans facilitate a plethora of important interactions namely cancer-host, host-pathogen, host-self interactions. Interaction with theses carbohydrates is enabled by lectins and the effects of these interactions can range from redundant to essential. Lectins are exposed on mammalian cell surfaces where they identify the information encoded in glycans and transfer it into signal transduction pathways. Such signal transduction pathways are complex and difficult to analyse. However, quantitative data with single cell resolution provides means to disentangle the associated signalling cascades. C-Type lectin receptors (CLRs) expressed on immune cells were chosen as a model system to study their capacity to transmit information encoded in glycans of incoming particles. To this end, monocytic cell lines cell lines expressing DC-SIGN, MCL, dectin-1, dectin-2, and mincle, as well as TNFAR and TLR-1&2 were established. Based on the study of Cheong et al., 2011 the amount of transmitted information was quantified by following NFκB dependent GFP expression. While most receptors did have a channel capacity of at least 1 bit, it was found that dectin-2 has a lower capacity to transmit information than other lectins. Especially the comparison to the related lectin mincle is interesting, since mincle uses the same pathway effectively. Furthermore, information transmission of dectin-2 could not be enhanced by other lectins or signalling molecules. Yet upon closer analysis it was found that the
sensitivity of the dectin-2 signal transduction pathway can be enhanced by overexpression of its co- receptor FcRγ, but surprisingly its transmitted information cannot. Moreover, it was suggested how
potential autoimmunity might be a cause for dectin-2’s inefficient signalling. The question of signal integration was also approached: How do cells combine the flow of information from multiple receptors? It was shown that the signal of dectin-2 and dectin-1 are being integrated as a compromise between both receptors. The reason for this compromise might be the activity of the phosphoprotein SYK, present in both dectin-1 and dectin-2 signal transduction pathways. By using the established assays and cell lines, soluble beta glucans (SBGs) were discovered to be potent
stimulators of dectin-1, where sensitivity to the SBGs was highly variable and dependent on their β- glucan side chains. Various different ligands for mincle on the other hand resulted in a similar signalling
behaviour. Building on insight in targeted delivery to lectins, it was shown how nucleic acids can be delivered to Langerin expressing cells and used to reprogramme the cells, a technology of tremendous potential for vaccination strategies and (non-germline) genetic editing.
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Taken together, the concepts of information theory with single cell resolved data enabled the quantification of CLRs signalling behaviour and signal integration. By using dectin-2 and other lectins as example it was demonstrated how the receptor itself determine the efficiency and therefore outcome of the signal transduction pathways. Moreover, the potential to explore glycan lectins interactions in drug targeting was exemplified by delivering mRNA via Langerin or demonstrating the dependency of dectin-1 sensitivity upon the β-glucan side chains of its ligands.
