GSDMA mutations influence autophagy-mediated asthma

• Applicant: Dr. Verena Schmitt
• Subject Area: Clinical Immunology and Allergology
• Term: from 2022 to 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 504226461

Asthma is the most common chronic inflammatory disease resulting from a complex interplay of environmental and genetic factors. Despite the identification of a large number of genetic loci associated with asthma, how these genetic variants promote disease is still poorly understood. The region on 17q21 remains the leading asthma susceptibility locus. While most studies focused on ORMDL3, we and others have identified additional genes in this region contributing to the predisposition to asthma. Our comprehensive fine mapping analyses demonstrated that some of the strongest association signals were observed within Gasdermin A (GSDMA). In contrast to other risk genetic variants in the 17q21 locus that are predominantly non-coding, GSDMA asthma associations resulted from amino acid changes predicted to alter the secondary structure of the GSDMA protein. Because of the tight linkage in 17q21, it remains unclear which functional variants underlie disease susceptibility and what the molecular mechanisms might be. The primary goal of this proposal is to understand the function of GSDMA and the contribution of asthma-risk GSDMA missense mutations to the disease. Mutations in GSDMA3, one of the three GSDMA orthologues in mice, were shown to regulate autophagy, a process essential for cellular homeostasis and cell survival under stress. Although autophagy has been linked to pulmonary diseases including asthma, data are conflicting. We detected GSDMA protein expression in human activated airway epithelial cells and CD4+ T cells, cell types relevant in the development of asthma. In addition, GSDMA levels were altered in response to modulation of the autophagic activity. We also provided first evidence that an asthma associated GSDMA missense mutation may be involved in the regulation of autophagy in human CD4+ T cells. Guided by our preliminary data, the objectives of this application address several critical questions to establish the link between GSDMA, autophagy, and asthma. By overexpressing wildtype and mutated GSDMA in vitro in alveolar epithelial cells by retroviral transduction, we will determine which of the four asthma associated GSDMA missense mutations contribute to autophagy regulation. In a cohort of asthmatics and healthy controls, we will investigate the effect of a functionally relevant GSDMA mutation on autophagy regulation in differentiated epithelial (air-liquid interface) and CD4+ T cells. Through this study, we will be able to delineate for the first time the specific molecular and cellular influence of GSDMA mutations on basal and activated autophagy in both cell types from the same patient in response to autophagy induction or inhibition and the impact on the release of pro-allergic cytokines. This assembly of data will reveal a mechanism of impaired autophagy in the innate and adaptive immune system contributing to asthma pathogenesis in patients with a defined GSDMA genotype with the potential for novel therapeutic interventions.

• DFG Programme: Research Grants
• Co-Investigator: Professorin Michaela Schedel-Bockholt, Ph.D.