The overall goal of this project involves a synergistic approach of multi-scale modeling and experimental observation to elucidate the fundamental mechanisms underlying inositol trisphosphate (IP3)-mediated cellular Ca2+ signaling. Cytosolic Ca2+ transients ubiquitously regulate cellular functions as diverse as secretion, contraction and proliferation. Information is encoded by spatio-temporal patterns of cytosolic Ca2+ signals at scales ranging from nanometers and microseconds to micrometers and minutes, involving a hierarchy of 'phonemes'of Ca2+ generated by individual channels, channels clusters, and interactions between clusters. These levels cannot simultaneously be observed by any single experimental technique, and the shorter scales are below experimental resolution. We therefore integrate data-driven mathematical modeling together with experimental electrophysiological and imaging measurements to elucidate how 'elementary'Ca2+ events involving individual channels and clusters are triggered and coupled to produce global cellular Ca2+ signals.
Specific aims are to: (i) characterize the gating and Ca permeation properties of the IP3 receptor (IP3R), and 2+ develop a predictive Markov model to account for its complex regulation by IP3 and Ca;(ii) experimentally 2+ determine the spatial distribution and functional interactions between IP3R and apply the IP3R model to develop a stochastic cluster model based on cellular observations;(iii) determine the mechanisms underlying cluster-cluster interactions and IP3 diffusion that underlie global cellular signals. We focus on IP3 signaling in single experimentally-tractable system (human type 1 IP3R expressed in DT40 cells and native in SH-SY5Y neuroblastoma cells), and further investigate perturbations induced by Alzheimer's-causing presenilin mutations. Moreover, the experimental and theoretical tools we develop will be widely applicable, and the emergent principles will illuminate fundamental mechanisms of Ca2+ signaling in many cell types. Our group involves three Lead Investigators, with expertise and responsibilities as follows: John E. Pearson. Los Alamos. Theoretician - provide overall direction of the project and synthesis of data;construct minimal Markov model for InsP3R gating and comprehensive multi-scale cellular models. Don-On D. Mak U. Penn. Experimentalist - single-channel electrophysiological recording and modeling. Ian Parker. U.C. Irvine. Experimentalist - cytosolic Ca2+ imaging and modeling. Our results will help elucidate the mechanisms underlying complex calcium signals that regulate the normal functioning of almost all cells in the body, and whose disruption is implicated in diseases as diverse as Alzheimer's, bipolar disorder, and heart failure.

Public Health Relevance

Specific patterns of calcium signals regulate crucial functions in all cells of the body, and disruptions of these signals are implicated in diseases including Alzheimer's. We will combine electrophysiological and imaging techniques together with theoretical modeling to elucidate the fundamental mechanisms by which intracellular calcium signals are generated at levels from the single-molecule to whole cell, with the dual aims of better understanding their normal functioning and how disorders in calcium signaling may lead to disease.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Modeling and Analysis of Biological Systems Study Section (MABS)
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Chin, Jean
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Los Alamos National Lab
Los Alamos
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Shah, Syed Islamuddin; Smith, Martin; Swaminathan, Divya et al. (2018) CellSpecks: A Software for Automated Detection and Analysis of Calcium Channels in Live Cells. Biophys J 115:2141-2151
Ellefsen, Kyle L; Parker, Ian (2018) Dynamic Ca2+ imaging with a simplified lattice light-sheet microscope: A sideways view of subcellular Ca2+ puffs. Cell Calcium 71:34-44
Toglia, Patrick; Demuro, Angelo; Mak, Don-On Daniel et al. (2018) Data-driven modeling of mitochondrial dysfunction in Alzheimer's disease. Cell Calcium 76:23-35
Shah, Syed Islamuddin; Demuro, Angelo; Mak, Don-On Daniel et al. (2018) TraceSpecks: A Software for Automated Idealization of Noisy Patch-Clamp and Imaging Data. Biophys J 115:9-21
Toglia, Patrick; Ullah, Ghanim; Pearson, John E (2017) Analyzing optical imaging of Ca2+ signals via TIRF microscopy: The limits on resolution due to chemical rates and depth of the channels. Cell Calcium 67:65-73
Parker, Ian; Evans, Katrina T; Ellefsen, Kyle et al. (2017) Lattice light sheet imaging of membrane nanotubes between human breast cancer cells in culture and in brain metastases. Sci Rep 7:11029
Lock, Jeffrey T; Smith, Ian F; Parker, Ian (2017) Comparison of Ca2+puffs evoked by extracellular agonists and photoreleased IP3. Cell Calcium 63:43-47
Dickinson, George D; Ellefsen, Kyle L; Dawson, Silvina Ponce et al. (2016) Hindered cytoplasmic diffusion of inositol trisphosphate restricts its cellular range of action. Sci Signal 9:ra108
Toglia, Patrick; Cheung, King-Ho; Mak, Don-On Daniel et al. (2016) Impaired mitochondrial function due to familial Alzheimer's disease-causing presenilins mutants via Ca(2+) disruptions. Cell Calcium 59:240-50
Lock, Jeffrey T; Parker, Ian; Smith, Ian F (2016) Communication of Ca(2+) signals via tunneling membrane nanotubes is mediated by transmission of inositol trisphosphate through gap junctions. Cell Calcium 60:266-72

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