Browsing by Author "Reissaus, Christopher A."
Now showing 1 - 7 of 7
Results Per Page
Sort Options
Item Author Correction: Super-resolution microscopy compatible fluorescent probes reveal endogenous glucagon-like peptide-1 receptor distribution and dynamics(Nature Publishing Group, 2020-10-09) Ast, Julia; Arvaniti, Anastasia; Fine, Nicholas H. F.; Nasteska, Daniela; Ashford, Fiona B.; Stamataki, Zania; Koszegi, Zsombor; Bacon, Andrea; Jones, Ben J.; Lucey, Maria A.; Sasaki, Shugo; Brierley, Daniel I.; Hastoy, Benoit; Tomas, Alejandra; D’Agostino, Giuseppe; Reimann, Frank; Lynn, Francis C.; Reissaus, Christopher A.; Linnemann, Amelia K.; D’Este, Elisa; Calebiro, Davide; Trapp, Stefan; Johnsson, Kai; Podewin, Tom; Broichhagen, Johannes; Hodson, David J.; Pediatrics, School of MedicineItem Endoplasmic reticulum stress alters ryanodine receptor function in the murine pancreatic β cell(American Society for Biochemistry and Molecular Biology, 2018-11-12) Yamamoto, Wataru R.; Bone, Robert N.; Sohn, Paul; Syed, Farooq; Reissaus, Christopher A.; Mosley, Amber L.; Wijeratne, Aruna B.; True, Jason D.; Tong, Xin; Kono, Kono; Evans-Molina, Carmella; Biochemistry and Molecular Biology, School of MedicineAlterations in endoplasmic reticulum (ER) calcium (Ca2+) levels diminish insulin secretion and reduce β-cell survival in both major forms of diabetes. The mechanisms responsible for ER Ca2+ loss in β cells remain incompletely understood. Moreover, a specific role for either ryanodine receptor (RyR) or inositol 1,4,5-triphosphate receptor (IP3R) dysfunction in the pathophysiology of diabetes remains largely untested. To this end, here we applied intracellular and ER Ca2+ imaging techniques in INS-1 β cells and isolated islets to determine whether diabetogenic stressors alter RyR or IP3R function. Our results revealed that the RyR is sensitive mainly to ER stress–induced dysfunction, whereas cytokine stress specifically alters IP3R activity. Consistent with this observation, pharmacological inhibition of the RyR with ryanodine and inhibition of the IP3R with xestospongin C prevented ER Ca2+ loss under ER and cytokine stress conditions, respectively. However, RyR blockade distinctly prevented β-cell death, propagation of the unfolded protein response (UPR), and dysfunctional glucose-induced Ca2+ oscillations in tunicamycin-treated INS-1 β cells and mouse islets and Akita islets. Monitoring at the single-cell level revealed that ER stress acutely increases the frequency of intracellular Ca2+ transients that depend on both ER Ca2+ leakage from the RyR and plasma membrane depolarization. Collectively, these findings indicate that RyR dysfunction shapes ER Ca2+ dynamics in β cells and regulates both UPR activation and cell death, suggesting that RyR-mediated loss of ER Ca2+ may be an early pathogenic event in diabetes.Item Interleukin-6 Reduces β-Cell Oxidative Stress by Linking Autophagy With the Antioxidant Response(American Diabetes Association, 2018-08) Marasco, Michelle R.; Conteh, Abass M.; Reissaus, Christopher A.; Cupit, John E.; Appleman, Evan M.; Mirmira, Raghavendra G.; Linnemann, Amelia K.; Pediatrics, School of MedicineProduction of reactive oxygen species (ROS) is a key instigator of β-cell dysfunction in diabetes. The pleiotropic cytokine interleukin 6 (IL-6) has previously been linked to β-cell autophagy but has not been studied in the context of β-cell antioxidant response. We used a combination of animal models of diabetes and analysis of cultured human islets and rodent β-cells to study how IL-6 influences antioxidant response. We show that IL-6 couples autophagy to antioxidant response and thereby reduces ROS in β-cells and human islets. β-Cell-specific loss of IL-6 signaling in vivo renders mice more susceptible to oxidative damage and cell death through the selective β-cell toxins streptozotocin and alloxan. IL-6-driven ROS reduction is associated with an increase in the master antioxidant factor NRF2, which rapidly translocates to the mitochondria to decrease mitochondrial activity and stimulate mitophagy. IL-6 also initiates a robust transient decrease in cellular cAMP levels, likely contributing to the stimulation of mitophagy to mitigate ROS. Our findings suggest that coupling autophagy to antioxidant response in β-cells leads to stress adaptation that can reduce cellular apoptosis. These findings have implications for β-cell survival under diabetogenic conditions and present novel targets for therapeutic intervention.Item PIE-FLIM Measurements of Two Different FRETBased Biosensor Activities in the Same Living Cells(Cell Press, 2020-04-21) Reissaus, Christopher A.; Day, Kathleen H.; Mirmira, Raghavendra G.; Dunn, Kenneth W.; Pavalko, Fredrick M.; Day, Richard N.; Pediatrics, School of MedicineWe report the use of pulsed interleaved excitation (PIE)-fluorescence lifetime imaging microscopy (FLIM) to measure the activities of two different biosensor probes simultaneously in single living cells. Many genetically encoded biosensors rely on the measurement of Förster resonance energy transfer (FRET) to detect changes in biosensor conformation that accompany the targeted cell signaling event. One of the most robust ways of quantifying FRET is to measure changes in the fluorescence lifetime of the donor fluorophore using FLIM. The study of complex signaling networks in living cells demands the ability to track more than one of these cellular events at the same time. Here, we demonstrate how PIE-FLIM can separate and quantify the signals from different FRET-based biosensors to simultaneously measure changes in the activity of two cell signaling pathways in the same living cells in tissues. The imaging system described here uses selectable laser wavelengths and synchronized detection gating that can be tailored and optimized for each FRET pair. Proof-of-principle studies showing simultaneous measurement of cytosolic calcium and protein kinase A activity are shown, but the PIE-FLIM approach is broadly applicable to other signaling pathways.Item Platelet-type 12-lipoxygenase deletion provokes a compensatory 12/15-lipoxygenase increase that exacerbates oxidative stress in mouse islet β cells(American Society for Biochemistry and Molecular Biology, 2019-04-19) Conteh, Abass M.; Reissaus, Christopher A.; Hernandez-Perez, Marimar; Nakshatri, Swetha; Anderson, Ryan M.; Mirmira, Raghavendra G.; Tersey, Sarah A.; Linnemann, Amelia K.; Biochemistry and Molecular Biology, School of MedicineIn type 1 diabetes, an autoimmune event increases oxidative stress in islet β cells, giving rise to cellular dysfunction and apoptosis. Lipoxygenases are enzymes that catalyze the oxygenation of polyunsaturated fatty acids that can form lipid metabolites involved in several biological functions, including oxidative stress. 12-Lipoxygenase and 12/15-lipoxygenase are related but distinct enzymes that are expressed in pancreatic islets, but their relative contributions to oxidative stress in these regions are still being elucidated. In this study, we used mice with global genetic deletion of the genes encoding 12-lipoxygenase (arachidonate 12-lipoxygenase, 12S type [Alox12]) or 12/15-lipoxygenase (Alox15) to compare the influence of each gene deletion on β cell function and survival in response to the β cell toxin streptozotocin. Alox12−/− mice exhibited greater impairment in glucose tolerance following streptozotocin exposure than WT mice, whereas Alox15−/− mice were protected against dysglycemia. These changes were accompanied by evidence of islet oxidative stress in Alox12−/− mice and reduced oxidative stress in Alox15−/− mice, consistent with alterations in the expression of the antioxidant response enzymes in islets from these mice. Additionally, islets from Alox12−/− mice displayed a compensatory increase in Alox15 gene expression, and treatment of these mice with the 12/15-lipoxygenase inhibitor ML-351 rescued the dysglycemic phenotype. Collectively, these results indicate that Alox12 loss activates a compensatory increase in Alox15 that sensitizes mouse β cells to oxidative stress.Item Super-resolution microscopy compatible fluorescent probes reveal endogenous glucagon-like peptide-1 receptor distribution and dynamics(Nature Research, 2020-01-24) Ast, Julia; Arvaniti, Anastasia; Fine, Nicholas H. F.; Nasteska, Daniela; Ashford, Fiona B.; Stamataki, Zania; Zania, Zsombor; Bacon, Andrea; Jones, Ben J.; Lucey, Maria A.; Sasaki, Shugo; Brierley, Daniel I.; Hastoy, Benoit; Tomas, Alejandra; D’Agostino, Giuseppe; Reimann, Frank; Lynn, Francis C.; Reissaus, Christopher A.; Linnemann, Amelia K.; D’Este, Elisa; Calebiro, Davide; Trapp, Stefan; Johnsson, Kai; Podewin, Tom; Broichhagen, Johannes; Hodson, David J.; Pediatrics, School of MedicineThe glucagon-like peptide-1 receptor (GLP1R) is a class B G protein-coupled receptor (GPCR) involved in metabolism. Presently, its visualization is limited to genetic manipulation, antibody detection or the use of probes that stimulate receptor activation. Herein, we present LUXendin645, a far-red fluorescent GLP1R antagonistic peptide label. LUXendin645 produces intense and specific membrane labeling throughout live and fixed tissue. GLP1R signaling can additionally be evoked when the receptor is allosterically modulated in the presence of LUXendin645. Using LUXendin645 and LUXendin651, we describe islet, brain and hESC-derived β-like cell GLP1R expression patterns, reveal higher-order GLP1R organization including membrane nanodomains, and track single receptor subpopulations. We furthermore show that the LUXendin backbone can be optimized for intravital two-photon imaging by installing a red fluorophore. Thus, our super-resolution compatible labeling probes allow visualization of endogenous GLP1R, and provide insight into class B GPCR distribution and dynamics both in vitro and in vivo.Item A Versatile, Portable Intravital Microscopy Platform for Studying Beta-cell Biology In Vivo(Springer Nature, 2019-06-11) Reissaus, Christopher A.; Piñeros, Annie R.; Twigg, Ashley N.; Orr, Kara S.; Conteh, Abass M.; Martinez, Michelle M.; Kamocka, Malgorzata M.; Day, Richard N.; Tersey, Sarah A.; Mirmira, Raghavendra G.; Dunn, Kenneth W.; Linnemann, Amelia K.; Pediatrics, School of MedicineThe pancreatic islet is a complex micro-organ containing numerous cell types, including endocrine, immune, and endothelial cells. The communication of these systems is lost upon isolation of the islets, and therefore the pathogenesis of diabetes can only be fully understood by studying this organized, multicellular environment in vivo. We have developed several adaptable tools to create a versatile platform to interrogate β-cell function in vivo. Specifically, we developed β-cell-selective virally-encoded fluorescent protein biosensors that can be rapidly and easily introduced into any mouse. We then coupled the use of these biosensors with intravital microscopy, a powerful tool that can be used to collect cellular and subcellular data from living tissues. Together, these approaches allowed the observation of in vivo β-cell-specific ROS dynamics using the Grx1-roGFP2 biosensor and calcium signaling using the GcAMP6s biosensor. Next, we utilized abdominal imaging windows (AIW) to extend our in vivo observations beyond single-point terminal measurements to collect longitudinal physiological and biosensor data through repeated imaging of the same mice over time. This platform represents a significant advancement in our ability to study β-cell structure and signaling in vivo, and its portability for use in virtually any mouse model will enable meaningful studies of β-cell physiology in the endogenous islet niche.