Document text
Principal Investigator: Carmella Evans-Molina
Organization: INDIANA UNIVERSITY INDIANAPOLIS
Fiscal Year: 2024
Award: $403,201
Funding agency: National Institute of Diabetes and Digestive and Kidney Diseases
PROJECT SUMMARY/ABSTRACT
Despite the importance of β cell failure in the progression of diabetes (type 1, type 2, and multiple monogenic
forms), the underlying molecular mechanisms responsible for β cell dysfunction remain incompletely understood.
Release of insulin from the pancreatic β cell occurs in response to dynamic changes in cytosolic calcium (Ca2+)
levels. To date, the majority of studies of β cell physiology have focused on the regulation of Ca2+ influx via
plasma membrane ion channels, which have traditionally been more amenable to study via electrophysiological
approaches. These studies have supported a dominant role for KATP channel-dependent plasma membrane
depolarization and Ca2+ influx via voltage-gated Ca2+ channels in the regulation of insulin release, especially in
response to very high concentrations of glucose. However, recent improvements in high temporal resolution
imaging pioneered by our group have enabled the detection of robust Ca2+ signals in β cells stimulated with more
physiologically relevant glucose concentrations, even in the absence of changes in plasma membrane potential,
pointing to a critical role for the regulated release of Ca2+ from intracellular stores. In support of this, our published
and preliminary data show that pharmacological manipulation of the activity of intracellular ryanodine receptors
(RYR) uniquely modulates these ultrafast Ca2+ release events, even in voltage-clamp conditions, while also
impacting glucose-stimulated insulin secretion. Together with other groups, we have found that the RYR2 isoform
predominates in pancreatic β cells, and importantly showed using qRT-PCR and mass spectometry-based
proteomics that RYR2 mRNA and protein can be identified in human and mouse islets and purified β cells.
Furthermore, our preliminary data indicate that mice with β cell selective Ryr2 knockout have reduced insulin
secretion and glucose intolerance, while ex vivo studies suggest that ER Ca2+ leak via dysregulated RYR activity
leads to alterations in β cell Ca2+ signalling and accelerated β cell death. Against this background, we
hypothesize that RYR2 channels serve as critical rheostats of β cell health and function and that they play key
roles in diabetes progression. To test this hypothesis, we have assembled a multidisciplinary MPI team with
expertise in β cell biology, diabetes physiology, quantitative imaging, and disease modelling, and three specific
aims are proposed. In Specific Aim 1, we will quantify β cell RYR2 activity and roles in pancreatic slices and in
vivo using intravital imaging. Specific Aim 2 will determine the in vivo role of β cell RYR2 in insulin secretion, β
cell survival, and glucose homeostasis using a highly β cell-specific knockout mouse model. Specific Aim 3 will
utilize mass spectrometry to determine mechanisms underlying ER stress-induced RYR2 dysfunction and in vitro
and in vivo mouse models to define how ER stress-induced RYR2 dysfunction impacts β cell Ca2+ signaling and
survival.
Terms: <2-photon><ATP phosphohydrolase (Ca(2+)-transporting)><Acceleration><Address><Adult-Onset Diabetes Mellitus><Age><Alleles><Allelomorphs><Apoptosis><Apoptosis Pathway><Beta Cell><Biophysics><Body Tissues><Bolus><Bolus Infusion><Ca Release Channel-Ryanodine Receptor><Ca(2+)-Transporting ATPase><Ca2+ ATPase><Ca2+ transporting ATPase><Calcium><Calcium ATPase><Calcium Adenosine Triphosphatase><Calcium Channel><Calcium Channel Antagonist Receptor><Calcium Channel Blocker Receptors><Calcium Ion Channels><Calcium Ion Signaling><Calcium Oscillations><Calcium Pump><Calcium Signaling><Calcium Waves><Calcium-Ryanodine Receptor Complex><Cell Body><Cell Communication and Signaling><Cell Death><Cell Function><Cell Physiology><Cell Process><Cell Signaling><Cell Survival><Cell Viability><Cell membrane><Cells><Cellular Function><Cellular Physiology><Cellular Process><Cellular biology><Chiro-Inositol><Clampings><Closure by clamp><Common Rat Strains><Complex><Cytoplasmic Membrane><D-Glucose><Data><Data Science><Detection><Dextrose><Diabetes Mellitus><Dysfunction><ER stress><Electrophysiology><Electrophysiology (science)><Endoplasmic Reticulum><Equilibrium><Ergastoplasm><Event><Failure><Functional disorder><Genes><Genetic><Glucose><Glucose Intolerance><Health><Human><Humulin R><IP3R><IP3R1><ITPR1><ITPR1 gene><Image><In Vitro><Individual><Inflammatory><Inositol><Inositol 1,4,5-Triphosphate Receptor Type 1><Insp3r1><Insulin><Insulin Cell><Insulin Secreting Cell><Intracellular Communication and Signaling><Ion Channel><Ionic Channels><Isoforms><KO mice><Ketosis-Resistant Diabetes Mellitus><Knock-out><Knock-out Mice><Knockout><Knockout Mice><Knowledge><Link><Maintenance><Mass Photometry/Spectrum Analysis><Mass Spectrometry><Mass Spectroscopy><Mass Spectrum><Mass Spectrum Analyses><Mass Spectrum Analysis><Maturity-Onset Diabetes Mellitus><Measures><Mediating><Membrane><Membrane Channels><Membrane Potentials><Mesoinositol><Messenger RNA><Metabolic><Metabolic stress><Mice><Mice Mammals><Modeling><Modern Man><Molecular><Monitor><Morphology><Murine><Mus><NIDDM><Neurophysiology / Electrophysiology><Non-Insulin Dependent Diabetes><Non-Insulin-Dependent Diabetes Mellitus><Noninsulin Dependent Diabetes><Noninsulin Dependent Diabetes Mellitus><Novolin R><Null Mouse><Organelles><Pancreas><Pancreatic><Pancreatic beta Cell><Pancreatic β-Cell><Pattern><Physics><Physiologic><Physiological><Physiology><Physiopathology><Plasma Membrane><Play><Process><Production><Programmed Cell Death><Proliferating><Protein Isoforms><Proteins><Proteomics><Publishing><Pump><Quantitative RTPCR><Quantitative Reverse Transcriptase PCR><Rat><Rats Mammals><Rattus><Reagent><Receptor Protein><Regular Insulin><Regulation><Reproducibility><Research><Resting Potentials><Role><RyR2><Ryanodine Receptor><Ryanodine Receptor Calcium Release Channel><Shapes><Signal Transduction><Signal Transduction Systems><Signaling><Slice><Slow-Onset Diabetes Mellitus><Stable Diabetes Mellitus><Stress><Structure of beta Cell of islet><Subcellular Process><T2 DM><T2D><T2DM><Testing><Tissues><Transmembrane Potentials><Type 2 Diabetes Mellitus><Type 2 diabetes><Type II Diabetes Mellitus><Type II diabetes><VDCC><Voltage-Dependent Calcium Channels><Work><adult onset diabetes><ages><balance><balance function><biological signal transduction><biophysical foundation><biophysical principles><biophysical sciences><blood glucose regulation><calcium indicator><calcium transporting ATPase><cell biology><diabetes><diet-associated obesity><diet-induced obesity><diet-related obesity><disease model><disorder model><electrophysiological><endoplasmic reticulum stress><experiment><experimental research><experimental study><experiments><glucose control><glucose homeostasis><glucose regulation><glucose tolerance><image-based method><imaging><imaging approach><imaging based approach><imaging method><imaging modality><impaired glucose tolerance><improved><in vivo><induced Cre><inducible Cre><insulin regulation><insulin secretion><intra-vital imaging><intra-vital microscopy><intravital imaging><intravital microscopy><islet><ketosis resistant diabetes><light microscopy><mRNA><maturity onset diabetes><membrane structure><mitochondrial metabolism><mouse model><multidisciplinary><murine model><necrocytosis><novel><pancreas beta cell><pancreas β cell><pancreatic b-cell><pathophysiology><pharmacologic><plasmalemma><qRTPCR><quantitative imaging><receptor><response><social role><temporal measurement><temporal resolution><time measurement><tool><triphosphate><tripolyphosphate><two-photon><type 1 and type 2 diabetes><type 2 DM><type I and type II diabetes><type II DM><type two diabetes><uptake><voltage><voltage clamp><β-cell><β-cells><βCell>