Sunday, May 11, 2025
5/11/2025
Molecular mechanisms of proton-sensing in CO2-dependent breathing - Abstract GPR4 is a G-protein coupled receptor required for CO2-dependent breathing. In the brainstem, rising CO2 levels cause a decrease in pH that activates GPR4. Genetic knockout of GPR4 results in two pathological phenotypes - reduced CO2-dependent breathing and frequent apneas, which are both rescued by specific re-expression of GPR4 in the brainstem. This establishes a link between inactivation of GPR4 and symptoms for severe breathing disorders including congenital central hypoventilation syndrome (CCHS) and central sleep apnea (CSA). However we do not know how GPR4 senses pH, and we do not know how existing small molecules modulate GPR4. Through this proposal, I will determine the molecular mechanism of GPR4 activation to provide insights into the regulation of CO2-dependent breathing and to enable the development of small molecules that activate GPR4. In Aim 1, I will determine the molecular details of how protons activate GPR4. In Aim 2, I will decipher how current antagonists bind and inactive GPR4. To accomplish these aims, I will combine the techniques of biochemistry, structural biology (cryogenic electron microscopy), and pharmacology (mutagenesis and signaling assays). These studies will provide mechanistic insight into the regulation of GPR4 activity through protons and small molecules. This will expand our fundamental understanding of how protons drive CO2-dependent breathing, and this will enable the future development of small molecules that activate GPR4, which could be novel therapeutics for CCHS and CSA.
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