- Ruan lab @ Thomas Jefferson University
Protein kinases comprise a diverse group of proteins that facilitate the phosphorylation of serine, threonine, and tyrosine residues. Some of these kinases are anchored in the cell membrane, enabling them to sense external signals and initiate intracellular signaling cascades. This subgroup includes receptor tyrosine kinases and receptor serine/threonine kinases. Although these molecules play crucial roles in regulating physiological functions and are extensively implicated in human diseases, we currently lack a detailed atomic-level understanding of these intricate molecular machines. This knowledge gap primarily stems from the inherent flexibility of the single-pass transmembrane domain, which poses significant challenges for structural analysis of these kinase receptors. In this research direction, we aim to comprehensively characterize these proteins using structural, functional, and computational approaches. In particular, we want to answer the following three questions:
By addressing these critical questions, we aspire to gain insights into the diseases associated with these receptors and provide valuable information for the development of therapeutic strategies to combat these debilitating conditions.
Ischemic stroke is one of the leading causes of disability and death in the United States. Acid accumulation in the brain during ischemic stroke causes neurotoxicity and irreversible tissue damage. Understanding the factors that contribute to acid-induced cell death during ischemic stroke is thus critical to define the pathological process and develop effective treatment strategies. The proton-activated chloride (PAC) channel (also known as ASOR or PAORAC) is a recently discovered cellular pH-sensor that plays a critical role in determining the outcome of brain damage after ischemic stroke. Under acidic conditions, the activation of PAC allows an influx of chloride current into the neuron which further causes cell swelling and death. In 2019, the PAC gene was cloned by two independent groups and was found to be a novel chloride channel. In 2020, I revealed the first near-atomic cryo-EM structures of the human PAC channel at two different conformational states, including an apo state and a proton-bound non-conducting state (1). Through close collaboration with Dr. Zhaozhu Qiu from John Hopkins University, we later established the proton-sensing, channel desensitization, and lipid modulation mechanisms of the PAC channel (2,3,4). The long-term objective of this research is to unveil the molecular principles underlying PAC channel function in both physiological and pathological conditions, and to develop specific compounds that could be used to mitigate the effect of ischemic stroke in patients.
