The role of TRPC6 channels in neutrophil recruitment

• Applicant: Professor Dr. Albrecht Schwab
• Subject Area: Anatomy and Physiology
• Term: from 2016 to 2020
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 313658831

The recruitment of neutrophil granulocytes from the blood follows a well defined sequence of events including rolling, adhesion and transmigration which is then followed by chemotaxis towards a lesion. Firm adhesion to endothelial cells is integrin-dependent and occurs as a result of activation of G-protein coupled receptors (GPCRs) for chemoattractants (e.g. CXCR2). CXCR2 contains like most other GPCRs an allosteric binding site for Na+ ions. Na+ binding inhibits constitutive GPCR activity which may be as high as 50 % of agonist-stimulated activity. Thus, Na+ binding within GPCRs appears to be a way to ensure the full dynamic range of receptor activation by agonists. CXCR2 ligands, classified as "intermediary chemoattractants", drive chemotaxis of neutrophils towards the vicinity of a lesion. "End target" chemoattractants, released within the lesion and prototypically represented by fMLP, then take over. Thus, chemoattractants act in a spatially distinct order during neutrophil recruitment. Neutrophil recruitment is Ca2+ dependent. We have shown that TRPC6 channels are functionally coupled to CXCR2-dependent steps. However, the contribution of other molecularly defined Ca2+ influx channels to individual steps of the recruitment cascade and the underlying mechanisms are not well characterized. Here we want to test the hypothesis whether (i) TRPC6 and TRPM2 channels are functionally coupled to intermediary and end target receptors, respectively, and thereby act at spatially distinct steps of the recruitment cascade. (ii) TRPC6-dependent mechanisms of firm adhesion will be studied in detail with atomic force microscopic techniques. Finally, we want to investigate, whether (iii) TRPC6 channels which are also permeable to Na+ ions, are linked to CXCR2 receptors by modifying allosteric binding of Na+ ions to the receptor protein via their impact on the intracellular Na+ concentration and/or the cell membrane potential.

• DFG Programme: Research Grants