Information transfer in mammalian glycan-based communication

Abstract

Glycan-binding proteins, so-called lectins, are exposed on mammalian cell surfaces and decipher the information encoded within glycans translating it into biochemical signal transduction pathways in the cell. These glycan-lectin communication pathways are complex and difficult to analyse. However, quantitative data with single cell resolution provides means to disentangle the associated signalling cascades. We chose C-Type lectin receptors (CLRs) expressed on immune cells as a model system to study their capacity to transmit information encoded in glycans of incoming particles. Lectin receptor NF{kappa}B-reporter cell lines expressing DC-SIGN, MCL, dectin-1, dectin-2, and mincle, as well as TNFR and TLR-1&2 in monocytic cell lines were characterized by comparing their efficiency to transmit glycan-encoded information. The information content was measured by following NF{kappa}B dependent GFP expression. While most receptors did transmit information to NF{kappa}B efficiently, we found dectin-2 to be an inefficient signalling receptor. Yet upon closer analysis we show that the sensitivity of the dectin-2 signal transduction pathway (EC50) can be enhanced by overexpression of its co-receptor FcR{gamma}, while its transmitted information cannot. In this context, we expanded our investigation towards the integration of multiple signal transduction pathways, which is crucial during pathogen recognition. We show how lectin receptors using a similar signal transduction pathway (dectin-1 and dectin-2) are being integrated; by striking a compromise between the lectins. By using dectin-2 and other lectins as example we demonstrate how cellular heterogeneity and the receptor itself determine the efficiency and therefore outcome of the signal transduction pathways.