We have three main research themes.

Gating and Pharmacology:  One effort is on the molecular mechanism of Orai channel operation. How does depletion of Ca2+ in the ER trigger the opening of Orai channels in the plasma membrane? What are the structural features of store-operated channel proteins? How are store-operated channels regulated? We know that Orai channels are activated by a unusual mechanism involving coordinated redistributions of the ER Ca2+ sensor (STIM1) and the channel, which results in both molecules gathering at the same peripheral sub-cellular sites. This type of activation process, where the stimulus brings the sensor and the channel together in opposite membranes is unusual among ion channels. We study the molecular and cellular events of this process by patch-clamp electrophysiology and molecular dynamics simulations and various live-cell imaging techniques such as fluorescence resonance energy transfer (FRET) microscopy, total internal reflection (TIRF) microscopy, and calcium imaging.

Neuroscience:    In a second major area of investigation, we are studying the functions of Orai channels in the brain, in astrocytes, microglia, and neurons. Calcium signals mediate many critical functions in the brain, from gene expression to synaptic plasticity. The role of store-operated calcium signals in these cells and how these signals are coupled to downstream effector functions is not known. We have discovered that Orai channels function as a key pathway for Ca2+ entry in astrocytes, microglia, stem cells, and dendritic spines of neurons and generate Ca2+ oscillations which play critical roles in a diverse set of endpoints including gliotransmitter release, synaptic plasticity, and neuroinflammation. We are examining the role of Orai channel mediated Ca2+ signals for brain function both in health and in disease, focussing on cognition and behavioral learning and on pathologies such as neuropathic pain and depression. We use a multidisciplinary approach for this effort that incorporates optical measurements of vesicle release, slice electrophysiology, transcriptome analysis, and calcium imaging in conjunction with behavioral analysis of genetically modified mice to understand the functional architecture of calcium signaling networks in neurons and astrocytes and how they are coupled to their downstream effector functions.

Lung Biology:  In a third project, we are studying the properties and functions of store-operated channels in the airway epithelium of the lung. Airway epithelial cells do not merely comprise a passive barrier in the lung but play an active role in orchestrating inflammatory responses, tuning both innate and adaptive immune reactions by producing many secreted factors and interacting with immune cells. We have found that store-operated channels serve as a major route of Ca2+ entry in lung epithelial cells, and are important for gene expression and the production of proinflammatory cytokines. Using both human and mouse systems, we aim to understand the physiological roles of Orai channels for airway inflammation in its relevance for airway diseases including asthma.

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