Translational Medical Research Commons^™

Mitochondrial Ca2+ Uniporter (Mcu) Variants Form Plasma-Membrane Channels, Iuliia Polina, Jyotsna Mishra, Michael Cypress, Maria Landherr, Nedyalka Valkov, Isabel Chaput, Bridget Nieto, Brian Rhee, Ameneh Ahrari, Nathan Demichaelis, Kye-Im Jeon, Ulrike Mende, Peng Zhang, Bong Sook Jhun, Jin O-Uchi

Center for Translational Medicine Faculty Papers

MCU, originally known as CCDC109A, is widely recognized as the gene responsible for encoding a pore-forming subunit of a Ca2+-selective channel, mitochondrial Ca2+ uniporter complex (mtCUC). While MCU expression is typically highly mitochondrial-specific, we report here a protein variant derived from the MCU gene, termed MCU-S, which lacks the mitochondria-targeting sequence (MTS) and forms a Ca2+-permeable channel outside of mitochondria. The mRNA of MCU-S was ubiquitously expressed in all cell types/tissues tested, with particularly high expression in human platelets. MCU-S protein formed Ca2+ channels at the plasma membrane, which exhibited similar channel properties to those observed in mtCUC. MCU-S channels …

Cardiac Sr-Mitochondria Contacts-Impact On Cardiac Physiology And Mitochondrial Fitness, Celia Fernandez-Sanz, Shey-Shing Sheu, Sergio De La Fuente

Center for Translational Medicine Faculty Papers

In adult cardiomyocytes, within the Mitochondrial Associated Membranes (MAMs), the sarcoplasmic reticulum (SR) and mitochondria juxtapose each other, forming a unique and highly repetitive functional structure throughout the cells. These SR-mitochondria contact sites have emerged as critical structures that regulate various physiological processes, including lipid exchange, calcium (Ca²⁺) communication, control of excitation-contraction bioenergetics coupling, and reactive oxygen species (ROS) production. Over the years, several scientific studies have reported the accumulation of diverse proteins within these SR-mitochondria close contacts. Some proteins strategically accumulate in these areas to enhance their function, such as the mitochondrial Ca²⁺ uniporter, while others …

Sarcoplasmic Reticulum-Mitochondria Microdomains: Hugging And Kissing In The Heart, Bong Sook Jhun, Jin O-Uchi, Brian Rhee, Ameneh Ahrari, Nathan Demichaelis, Kye-Im Jeon, David M. Booth, Shey-Shing Sheu

Center for Translational Medicine Faculty Papers

Endoplasmic reticulum (ER)-mitochondrial (ER-Mito) interface, termed mitochondrial-ER contacts (MERCs), plays significant roles in the maintenance of bioenergetics and basal cell functions via the exchange of lipids, Ca 2 þ , and reactive oxygen species (ROS) in various cell types/tissues. Genetic deletion of mitofusin 2 (Mfn2), one of the key components of ER-Mito tethering, in cardiomy- ocytes (CMs) in vivo revealed the importance of the microdomains between mitochondria and sarcoplasmic reticulum (SR), a dif- ferentiated form of ER in muscle cells, for maintaining normal mitochondrial Ca 2 þ (mtCa 2 þ ) handling and bioenergetics in the adult heart. However, key …

Nitric Oxide Does Not Improve Liver Mitochondrial Function 48 Hours After Cecal Ligation And Perforation In Experimental Sepsis, Pierre Eyenga, Shey-Shing Sheu

Center for Translational Medicine Faculty Papers

Nitric oxide (NO) has a dual effect on mitochondria. Incubating liver mitochondria with NO improves oxidative phosphorylation (OXPHOS) efficiency by decreasing state 4 respiration more than ATP synthesis and preventing mitochondrial permeability transition pore (mPTP) opening. We evaluated the effect of L-arginine (L-arg), an NO donor, on isolated liver mitochondrial respiration and mPTP in sepsis. Male mice were subjected to cecal ligation and perforation (CLP) with saline resuscitation or sham. After 8, 24, and 48 h, with and without L-arg, we measured isolated liver mitochondrial respiration and cytochrome c oxidase (COX) activity using polarographic methods and calcium retention capacity (CRC) …

Identity, Structure, And Function Of The Mitochondrial Permeability Transition Pore: Controversies, Consensus, Recent Advances, And Future Directions, Paolo Bernardi, Christoph Gerle, Andrew P. Halestrap, Elizabeth A. Jonas, Jason Karch, Nelli Mnatsakanyan, Evgeny Pavlov, Shey-Shing Sheu, Alexander A. Soukas

Center for Translational Medicine Faculty Papers

The mitochondrial permeability transition (mPT) describes a Ca2+-dependent and cyclophilin D (CypD)-facilitated increase of inner mitochondrial membrane permeability that allows diffusion of molecules up to 1.5 kDa in size. It is mediated by a non-selective channel, the mitochondrial permeability transition pore (mPTP). Sustained mPTP opening causes mitochondrial swelling, which ruptures the outer mitochondrial membrane leading to subsequent apoptotic and necrotic cell death, and is implicated in a range of pathologies. However, transient mPTP opening at various sub-conductance states may contribute several physiological roles such as alterations in mitochondrial bioenergetics and rapid Ca2+ efflux. Since its discovery decades ago, intensive efforts …

Mitochondria As Causes Of And Therapeutic Targets In Chronic Post-Sepsis Skeletal Muscle Weakness, Meagan Scott Kingren

Theses and Dissertations--Pharmacology and Nutritional Sciences

Sepsis, or the organ damage that ensues after the body fails to properly contain a local infection, is the leading cause of in-patient hospitalization in the United States. Advances in critical care medicine over the last 20 years have enabled most sepsis patients to survive the life-threatening dysregulated immune response. However, a majority of survivors report chronic weakness and fatigue years after sepsis, and the cause of this weakness remains largely unknown. This dissertation work focused first on elucidating the major causes of post-sepsis muscle weakness (Aim 1). This aim involved a time-course study to determine when muscle weakness was …

Regulation Of Oxidative Phosphorylation Of Liver Mitochondria In Sepsis, Pierre Eyenga, Benjamin Rey, Lilia Eyenga, Shey-Shing Sheu

Center for Translational Medicine Faculty Papers

The link between liver dysfunction and decreased mitochondrial oxidative phosphorylation in sepsis has been clearly established in experimental models. Energy transduction is plastic: the efficiency of mitochondrial coupling collapses in the early stage of sepsis but is expected to increase during the recovery phases of sepsis. Among the mechanisms regulating the coupling efficiency of hepatic mitochondria, the slipping reactions at the cytochrome oxidase and ATP synthase seem to be a determining element, whereas other regulatory mechanisms such as those involving proton leakage across the mitochondrial membrane have not yet been formally proven in the context of sepsis. If the dysfunction …

Electrophysiological Properties Of The Mitochondrial Permeability Transition Pores: Channel Diversity And Disease Implication., M. A. Neginskaya, E. V. Pavlov, S.-S. Sheu

Center for Translational Medicine Faculty Papers

The mitochondrial permeability transition pore (mPTP) is a channel that, when open, is responsible for a dramatic increase in the permeability of the mitochondrial inner membrane, a process known as the mitochondrial permeability transition (mPT). mPTP activation during Ca2+ dyshomeostasis and oxidative stress disrupts normal mitochondrial function and induces cell death. mPTP opening has been implicated as a critical event in many diseases, including hypoxic injuries, neurodegeneration, and diabetes. Discoveries of recent years indicate that mPTP demonstrates very complicated behavior and regulation, and depending on specific induction or stress conditions, it can function as a high-conductance pore, a small channel, …

Metformin Enhances Autophagy And Normalizes Mitochondrial Function To Alleviate Aging-Associated Inflammation, Leena P. Bharath, Madhur Agrawal, Grace Mccambridge, Dequina A. Nicholas, Hatice Hasturk, Jing Liu, Lao Jiang, Rui Liu, Zhenheng Guo, Jude T. Deeney, Caroline M. Apovian, Jennifer Snyder-Cappione, Gregory S. Hawk, Rebecca M. Fleeman, Riley M. F. Pihl, Katherine Thompson, Anna C. Belkina, Licong Cui, Elizabeth A. Proctor, Philip A. Kern, Barbara S. Nikolajczyk

Clinical and Translational Science Faculty Publications

Age is a non-modifiable risk factor for the inflammation that underlies age-associated diseases; thus, anti-inflammaging drugs hold promise for increasing health span. Cytokine profiling and bioinformatic analyses showed that Th17 cytokine production differentiates CD4+ T cells from lean, normoglycemic older and younger subjects, and mimics a diabetes-associated Th17 profile. T cells from older compared to younger subjects also had defects in autophagy and mitochondrial bioenergetics that associate with redox imbalance. Metformin ameliorated the Th17 inflammaging profile by increasing autophagy and improving mitochondrial bioenergetics. By contrast, autophagy-targeting siRNA disrupted redox balance in T cells from young subjects and activated the Th17 …

The Short Variant Of Optic Atrophy 1 (Opa1) Improves Cell Survival Under Oxidative Stress., Hakjoo Lee, Sylvia B Smith, Shey-Shing Sheu, Yisang Yoon

Center for Translational Medicine Faculty Papers

Optic atrophy 1 (OPA1) is a dynamin protein that mediates mitochondrial fusion at the inner membrane. OPA1 is also necessary for maintaining the cristae and thus essential for supporting cellular energetics. OPA1 exists as membrane-anchored long form (L-OPA1) and short form (S-OPA1) that lacks the transmembrane region and is generated by cleavage of L-OPA1. Mitochondrial dysfunction and cellular stresses activate the inner membrane-associated zinc metallopeptidase OMA1 that cleaves L-OPA1, causing S-OPA1 accumulation. The prevailing notion has been that L-OPA1 is the functional form, whereas S-OPA1 is an inactive cleavage product in mammals, and that stress-induced OPA1 cleavage causes mitochondrial fragmentation …

Mitochondrial Quality Control In Age-Related Pulmonary Fibrosis., Willy Roque, Karina Cuevas-Mora, Freddy Romero

Center for Translational Medicine Faculty Papers

Idiopathic pulmonary fibrosis (IPF) is age-related interstitial lung disease of unknown etiology. About 100,000 people in the U.S have IPF, with a 3-year median life expectancy post-diagnosis. The development of an effective treatment for pulmonary fibrosis will require an improved understanding of its molecular pathogenesis and the "normal" and "pathological' hallmarks of the aging lung. An important characteristic of the aging organism is its lowered capacity to adapt quickly to, and counteract, disturbances. While it is likely that DNA damage, chronic endoplasmic reticulum (ER) stress, and accumulation of heat shock proteins are capable of initiating tissue repair, recent studies point …

Gsk3Β-Dependent Phosphorylation Of Cypd And Regulation Of Mptp Opening During Myocardial Infarction, Stephen Hurst, Ludovic Gomez, Shey-Shing Sheu

Center for Translational Medicine Posters

Background

Mitochondrial calcium overload and oxidative stress during ischemia reperfusion (I/R) injury remains a major obstacle during percutaneous coronary intervention after acute myocardial infarction. It often leads to an increased susceptibility for mitochondria permeability transition pore (mPTP) opening leading to cell death. Mitochondrial calcium overload and ROS have been identified as key triggers to open the mPTP for over 30 years, yet the exact mechanism has remained elusive. Additionally, glycogen synthase kinase 3β; (GSK-3β;) is proposed as one of the key molecules that regulate mitochondrial dysfunction and injury during I/R. Indeed inhibition of GSK-3β has been shown to be required …

Pyk2 Expression And Localization In Cardiac Mitochondria And Its Role In Mitochondrial Calcium Regulation, Ariele Baggett, Celia Fernandez-Sanz, Sergio De La Fuente, Johannes Hoek, Shey-Shing Sheu

Center for Translational Medicine Posters

TRPM2 is a non-selective cation channel located in the plasma membrane of the cell. Upon activation, the channel opens, allowing calcium to enter into the cytosol of the cell, leading ultimately to the phosphorylation and activation of the enzyme Pyk2 (proline-rich tyrosine kinase 2). Once phosphorylated, Pyk2 translocates from the cytosol to the mitochondria, where it regulates the formation of the pore component of the mitochondrial calcium uniporter (MCU) complex. Consequently, this interaction is a key factor in mitochondrial calcium uptake and therefore mitochondrial bioenergetics.

Endorepellin Remodels The Endothelial Transcriptome Toward A Pro-Autophagic And Pro-Mitophagic Gene Signature., Thomas Neill, Eva Andreuzzi, Zi-Xuan Wang, Stephen C. Peiper, Maurizo Mongiat, Renato V. Iozzo

Department of Pathology, Anatomy, and Cell Biology Faculty Papers

Regulation of autophagy by proteolytically cleaved fragments of heparan sulfate proteoglycans is a novel and current research focus in tumor biology. Endorepellin is the C-terminal angiostatic fragment of the heparan sulfate proteoglycan perlecan and induces autophagy in endothelial cells. To further investigate this property, we used NanoString, a digital PCR platform for measuring pre-defined transcripts in biological samples to analyze a custom subset of 95 autophagy-related genes in human umbilical vein endothelial cells treated with ultrapure human recombinant endorepellin. We discovered an endorepellin-evoked pro-autophagic and pro-mitophagic gene expression signatures, which included two coordinately up-regulated mitochondrial-associated genes encoding the E3 ubiquitin …

The Influence Of A Kdt501, A Novel Isohumulone, On Adipocyte Function In Humans, Brian S. Finlin, Beibei Zhu, Bernard P. Kok, Cristina Godio, Philip M. Westgate, Neile Grayson, Robert Sims, Jeffrey S. Bland, Enrique Saez, Philip A. Kern

Clinical and Translational Science Faculty Publications

Objective: In a phase II clinical trial in nine obese, insulin-resistant humans, we observed that treatment with KDT501, a novel isohumulone drug, increased total and high-molecular weight (HMW) adiponectin in plasma. The objective was to determine whether KDT501 increased adiponectin secretion from subcutaneous white adipose tissue (SC WAT) and the underlying mechanism(s).

Methods: Nine obese participants with either prediabetes or with normal glucose tolerance plus three features of metabolic syndrome were part of the study. SC WAT biopsies were performed before and after 28 days of KDT501 treatment in a clinical research setting. In addition, a cold stimulus was used …

New Insights Into Post-Sepsis Muscle Weakness Elucidated Using A Novel Animal Model, Allison M. Steele

Theses and Dissertations--Physiology

Sepsis is a severe life-threatening critical illness that damages multiple physiological systems. After hospital discharge, more than 70% of severe sepsis survivors report profound weakness which significantly impacts quality of life. Such weakness gives rise to new limitations of daily living, which ultimately leads to loss of independence in many patients. Despite wide recognition of this serious issue by clinicians and researchers alike, the mechanisms contributing to chronic skeletal muscle dysfunction after sepsis are not well understood. Lack of progress in this field is largely due to the absence of an appropriate animal model; current models are either too mild …

The Mitochondrial Ca(2+) Uniporter: Structure, Function, And Pharmacology., Jyotsna Mishra, Bong Sook Jhun, Stephen Hurst, Jin O-Uchi, György Csordás, Shey-Shing Sheu

Center for Translational Medicine Faculty Papers

Mitochondrial Ca(2+) uptake is crucial for an array of cellular functions while an imbalance can elicit cell death. In this chapter, we briefly reviewed the various modes of mitochondrial Ca(2+) uptake and our current understanding of mitochondrial Ca(2+) homeostasis in regards to cell physiology and pathophysiology. Further, this chapter focuses on the molecular identities, intracellular regulators as well as the pharmacology of mitochondrial Ca(2+) uniporter complex.

Targeting The Redox System To Overcome Mechanisms Of Drug Resistance In Chronic Lymphocytic Leukemia, Marcia A. Ogasawara

Dissertations and Theses (Open Access)

Chronic Lymphocytic Leukemia (CLL) is the most common form of leukemia diagnosed in Western countries and is characterized by clonal expansion of B cells. The clinical course of CLL is diverse and nearly 50% of patients present with chromosomal abnormalities. Deletion of the short arm on chromosome 17 (del17p) occurs in 5-7% of cases and presents with the shortest median survival time and often respond poorly to therapy. The tumor suppressor gene, TP53 is located on this region and it is well established that the p53 protein regulates multiple functions including: mitochondria biogenesis, response to DNA damage and redox balance. …