Solitary chemosensory cell development and function

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PROJECT SUMMARY Novel approaches to airway epithelial study have broadened our understanding of its diverse cellular makeup, developmental regulators, response to injury, and cell interactions involved in local tissue function. Recent work by our group and others has demonstrated a role for airway solitary chemosensory cells (SCCs) in detection of irritants within the airway surface liquid, signal transduction through canonical bitter taste signaling effectors, and initiation of a multifaceted immune response. Interestingly, lineage implications from RNAseq based approached in mouse and human lung studies suggest a possible relationship between SCCs and other rare airway cell types including the ionocyte and the neuroendocrine cell. Our central hypothesis is that human SCCs encompass a heterogeneous population that is modulated in the allergic inflammatory setting, and uniquely express cell-specific chemosensory receptors to detect human disease-associated compounds. This hypothesis has been formulated on the basis of publications and preliminary data produced in the applicant's laboratory during the K23 mentored research period, and Co-I Vladar's long-standing interest in airway epithelial repair. To test this—and generate tools for further mechanistic study—we will utilize a platform of retroviral gene transfer to genetically modify SCCs in human cell culture. We will pursue two aims: (1) characterization of SCC differentiation using the hTRPM5p-GFP lentiviral reporter in normal and allergic human primary sinonasal epithelial cell culture; and (2) test human SCC functional responses to disease-associated airborne irritants using a real-time TRPM5-mCherry/GCaMP6 Ca2+ reporter in primary HSNEC culture. Our long-term goal is to determine the functional role(s) of SCCs and chemosensory cell types in airway epithelial homeostasis, and to translate these findings into a cohesive understanding of airway mucosal immunity in human health and disease. Notably, limitations of available methods for labeling and isolating this rare cell type from human tissues have resulted in challenges in translating findings from mouse to human. This innovative proposal represents a significant conceptual departure from the status quo, and will utilize novel methodologies to test specific hypotheses and for general discovery in an area where little is known. The proposed research is significant because it is expected to advance understanding of how SCCs function as environmental sensory that regulate epithelial homeostasis. Ultimately, such knowledge has the potential to be developed into effective therapies for inflammatory airway disorders, a pressing need given the significant incidence and burden of these diseases.