The overall goal of this project involves a synergistic approach of multi-scale modeling and experimental observation to elucidate the fundamental mechanisms underlying cellular calcium signaling. Cytosolic Ca2+ transients serve as a ubiquitous signaling mechanism that regulates 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 millimeters and minutes, involving `phonemes'of Ca2+ constructed hierarchically through the activity of individual channels;multiple channels within 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 employ a dual, tightly integrated and iterative approach of data-driven mathematical modeling together with experimental measurements involving electrophysiological single-channel recording and high-resolution cellular Ca2+ imaging to elucidate how 'elementary'Ca2+ events involving individual channels and clusters are triggered and coupled to produce global cellular calcium signals.
Specific aims are to: (i) characterize the gating and Ca2+ permeation properties of IP3R, and develop a predictive mathematical model to account for its complex regulation by IP3 and Ca2+;(ii) observe and model the stochastic, Ca2+-mediated functional coupling between individual channels within a cluster, and;(iii) determine the mechanisms underlying cluster-cluster interactions that allow for propagation of global signals and the powerful differential modulation of this process by Ca2+ buffers of differing kinetics. We focus on IP3 signaling in a single experimentally-tractable system (human SH- SY5Y neuroblastoma cells), but 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 five Lead Investigators, with expertise and responsibilities as follows: John Pearson. Los Alamos. Theoretician - provides overall direction and synthesis of data; construction of low-dimensional IP3 receptor model and comprehensive multi-scale cellular models. Kevin Foskett and Daniel Mak U. Penn. Experimentalists - electrophysiological single-channel recording and IP3 receptor/channel modeling. Ian Parker. U.C. Irvine. Experimentalist - cytosolic Ca2+ imaging and modeling. Jianwei Shuai. Xiamen University. Theoretician. Computer modeling of Ca2+ signals. 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 Alzheimers, bipolar disorder, and heart failure.

Public Health Relevance

This unique integrative approach to discover the fundamental mechanisms by which intracellular Ca2+ signals are generated will fundamentally enhance our understanding of their normal functioning and provide insights into how their disruption affects numerous diseases as varied as pancreatitis and Alzheimer's.

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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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
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
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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