时 间：2018年7月17日 10:00-11:30
主 持 人：肖百龙老师
报 告 人：Donald L. Gill. (Department of Cellular and Molecular Physiology, Penn State University College of Medicine, Hershey, USA )
题 目: New Understanding on the STIM-Orai Coupling Interface
摘 要：Store-operated Ca2+ entry signals are mediated by plasma membrane Orai channels activated through intermembrane coupling with Ca2+-sensing STIM proteins in the endoplasmic reticulum. The nature of this elaborate Orai gating mechanism has remained enigmatic. Based on the Drosophila Orai structure, mammalian Orai1 channels are hexamers comprising three dimeric subunit pairs. We utilized concatenated Orai1 dimers to probe the function of key domains within the channel pore and gating regions. The Orai1-E106Q selectivity filter mutant, widely considered a dominant pore blocker, was surprisingly non-dominant within concatenated heterodimers with Orai1-WT. The Orai1-E106Q/WT heterodimer formed STIM1-activated nonselective cation channels with significantly enlarged apparent pore-diameter. Other E106 substitutions entirely blocked the function of heterodimers with Orai1-WT. The hydrophobic pore-lining mutation, V102C that constitutively opens channels, was suppressed by Orai1-WT in the heterodimer. In contrast, the naturally occurring R91W pore-lining mutation associated with human immunodeficiency, was a completely dominant-negative over Orai-WT in heterodimers. Heterodimers containing the inhibitory K85E mutation extending outward from the pore-helix, gave an interesting partial effect on both channel-activation and STIM1-binding, indicating an important allosteric link between the cytosolic Orai1 domains. The Orai1 C-terminal STIM1-binding domain mutation, L273D, powerfully blocked STIM1-induced channel activation. The Orai1-L273D/WT heterodimer had drastically impaired STIM1-induced channel-gating, but, unexpectedly, retained full STIM1-binding. This reveals the critical role of L273 in transducing the STIM1 binding signal into the allosteric conformational change that initiates channel gating. Overall, our results provide important new insights into the role of key functional domains that mediate STIM1-induced gating of the Orai1 channel.
简 介：Donald L. Gill – BIOGRAPHY.
Dr. Donald Gill is currently Professor and Chair of the Department of Cellular and Molecular Physiology at the Penn State University College of Medicine. He earned his Bachelor of Science degree in Biochemistry at the University of Sussex in England, in 1975, and his PhD in Biochemistry from the University of London, England in 1979, working with Roger Ekins on hormone receptor activation. After completing his PhD, Dr. Gill accepted a position as postdoctoral fellow at the National Institutes of Health in Bethesda, MD, where he worked with Martin Rodbell (Nobel Laureate in Physiology or Medicine in 1994) focusing on G proteins and signal transduction mechanisms. In 1982, Dr. Gill became Assistant Professor in the Department of Biochemistry and Molecular Biology at the University of Maryland School of Medicine in Baltimore, Maryland, where he started his own lab. While at Maryland, Dr. Gill achieved tremendous success and became a prominent researcher in the field of ion channel-mediated signal transduction. In 2007, Dr. Gill moved to Temple University and became Chair of Biochemistry Department. In 2014, Dr. Gill moved to become the new chair of the highly distinguished Department of Cellular and Molecular Physiology in the Penn State University College of Medicine.
His laboratory studies the function and control of calcium signals generated through the activation of calcium channels. His work has defined many novel parameters of the structure, function and control of the Ca2+ signaling machinery, focusing on smooth muscle and immune cell models to understand the extraordinary molecular cross-talk and functional integration that exists between Ca2+ sensors and Ca2+ channel proteins. In recent years, his lab has focused on the ubiquitously expressed STIM and Orai proteins that mediate essential Ca2+ signals in almost all cell types. Dr. Gill has over 120 peer-reviewed publications in many high tier journals, including Cell, Nature, Science, and PNAS. Dr. Gill also serves as reviewer for grant agencies including NIH, NSF and editor or reviewer for several renowned journals. He is also the founder of the well-known and highly subscribed Calcium Signaling Gordon Research Conference which he started in 1993, and has chaired numerous national and international symposia and conferences.