Biochemistry, Biophysics, and Structural Biology Commons^™

Ceramide Synthase Tlcd3b Is A Novel Gene Associated With Human Recessive Retinal Dystrophy, Renae Elaine Bertrand, Jun Wang, Kaitlyn H Xiong, Chinthana Thangavel, Xinye Qian, Rola Ba-Abbad, Qingnan Liang, Renata T Simões, Shirley A M Sampaio, Keren J Carss, F Lucy Raymond, Anthony G Robson, Andrew R Webster, Gavin Arno, Fernanda Belga Ottoni Porto, Rui Chen

Faculty, Staff and Students Publications

PURPOSE: Previous studies suggest that ceramide is a proapoptotic lipid as high levels of ceramides can lead to apoptosis of neuronal cells, including photoreceptors. However, no pathogenic variant in ceramide synthases has been identified in human patients and knockout of various ceramide synthases in mice has not led to photoreceptor degeneration.

METHODS: Exome sequencing was used to identify candidate disease genes in patients with vision loss as confirmed by standard evaluation methods, including electroretinography (ERG) and optical coherence tomography. The vision loss phenotype in mice was evaluated by ERG and histological analyses.

RESULTS: Here we have identified four patients with …

The Rac-Gef Tiam1 Promotes Dendrite And Synapse Stabilization Of Dentate Granule Cells And Restricts Hippocampal-Dependent Memory Functions, Jinxuan Cheng, Federico Scala, Francisco A Blanco, Sanyong Niu, Karen Firozi, Laura Keehan, Shalaka Mulherkar, Emmanouil Froudarakis, Lingyong Li, Joseph G Duman, Xiaolong Jiang, Kimberley F Tolias

Faculty, Staff and Students Publications

The dentate gyrus (DG) controls information flow into the hippocampus and is critical for learning, memory, pattern separation, and spatial coding, while DG dysfunction is associated with neuropsychiatric disorders. Despite its importance, the molecular mechanisms regulating DG neural circuit assembly and function remain unclear. Here, we identify the Rac-GEF Tiam1 as an important regulator of DG development and associated memory processes. In the hippocampus, Tiam1 is predominantly expressed in the DG throughout life. Global deletion of Tiam1 in male mice results in DG granule cells with simplified dendritic arbors, reduced dendritic spine density, and diminished excitatory synaptic transmission. Notably, DG …

Hermansky-Pudlak Syndrome-2 Alters Mitochondrial Homeostasis In The Alveolar Epithelium Of The Lung, Karina Cuevas-Mora, Willy Roque, Hoora Shaghaghi, Bernadette R Gochuico, Ivan O Rosas, Ross Summer, Freddy Romero

Faculty, Staff and Students Publications

BACKGROUND: Mitochondrial dysfunction has emerged as an important player in the pathogenesis of idiopathic pulmonary fibrosis (IPF), a common cause of idiopathic interstitial lung disease in adults. Hermansky-Pudlak syndrome (HPS) is a rare autosomal recessive disorder that causes a similar type of pulmonary fibrosis in younger adults, although the role of mitochondrial dysfunction in this condition is not understood.

METHODS: We performed a detailed characterization of mitochondrial structure and function in lung tissues and alveolar epithelial cells deficient in the adaptor protein complex 3 beta 1 (Ap3b1) subunit, the gene responsible for causing subtype 2 of HPS (HPS-2).

RESULTS: We …

Lkb1 And Ampk Instruct Cone Nuclear Position To Modify Visual Function, Courtney A Burger, Nicholas E Albrecht, Danye Jiang, Justine H Liang, Ross A Poché, Melanie A Samuel

Faculty, Staff and Students Publications

Cone photoreceptors detect light and are responsible for color vision. These cells display a distinct polarized morphology where nuclei are precisely aligned in the apical retina. However, little is known about the mechanisms involved in cone nuclear positioning or the impact of this organization on retina function. We show that the serine/threonine kinase LKB1 and one of its substrates, AMPK, regulate cone nuclear positioning. In the absence of either molecule, cone nuclei are misplaced along the axon, resulting in altered nuclear lamination. LKB1 is required specifically in cones to mediate this process, and disruptions in nuclear alignment result in reduced …

Calcium Ions Trigger The Exposure Of Phosphatidylserine On The Surface Of Necrotic Cells, Yoshitaka Furuta, Omar Pena-Ramos, Zao Li, Lucia Chiao, Zheng Zhou

Faculty, Staff and Students Publications

Intracellular Ca2+ level is under strict regulation through calcium channels and storage pools including the endoplasmic reticulum (ER). Mutations in certain ion channel subunits, which cause mis-regulated Ca2+ influx, induce the excitotoxic necrosis of neurons. In the nematode Caenorhabditis elegans, dominant mutations in the DEG/ENaC sodium channel subunit MEC-4 induce six mechanosensory (touch) neurons to undergo excitotoxic necrosis. These necrotic neurons are subsequently engulfed and digested by neighboring hypodermal cells. We previously reported that necrotic touch neurons actively expose phosphatidylserine (PS), an "eat-me" signal, to attract engulfing cells. However, the upstream signal that triggers PS externalization remained elusive. Here we …

The Gut Microbiome Contributes To Blood-Brain Barrier Disruption In Spontaneously Hypertensive Stroke Prone Rats, James W Nelson, Sharon C Phillips, Bhanu P Ganesh, Joseph F Petrosino, David J Durgan, Robert M Bryan

Faculty, Staff and Students Publications

In recent years, it has become apparent that the gut microbiome can influence the functioning and pathological states of organs and systems throughout the body. In this study, we tested the hypothesis that the gut microbiome has a major role in the disruption of the blood-brain barrier (BBB) in the spontaneously hypertensive stroke prone rats (SHRSP), an animal model for hypertensive cerebral small vessel disease (CSVD). Loss of BBB is thought to be an early and initiating component to the full expression of CSVD in animal models and humans. To test this hypothesis, newly born SHRSP pups were placed with …

Alpha-Single Chains Of Collagen Type Vi Inhibit The Fibrogenic Effects Of Triple Helical Collagen Vi In Hepatic Stellate Cells, Christian Freise, Hyunho Lee, Christopher Chronowski, Doug Chan, Jessica Cziomer, Martin Rühl, Tarkan Dagdelen, Maik Lösekann, Ulrike Erben, Andre Catic, Werner Tegge, Detlef Schuppan, Rajan Somasundaram, Ergun Sahin

Faculty, Staff and Students Publications

The interaction of extracellular matrix (ECM) components with hepatic stellate cells (HSCs) is thought to perpetuate fibrosis by stimulating signaling pathways that drive HSC activation, survival and proliferation. Consequently, disrupting the interaction between ECM and HSCs is considered a therapeutical avenue although respective targets and underlying mechanisms remain to be established. Here we have interrogated the interaction between type VI collagen (CVI) and HSCs based on the observation that CVI is 10-fold upregulated during fibrosis, closely associates with HSCs in vivo and promotes cell proliferation and cell survival in cancer cell lines. We exposed primary rat HSCs and a rat …

Mucins, Gut Microbiota, And Postbiotics Role In Colorectal Cancer, Ramesh Pothuraju, Sanjib Chaudhary, Satyanarayana Rachagani, Sukhwinder Kaur, Hemant K Roy, Michael Bouvet, Surinder K Batra

Faculty, Staff and Students Publications

An imbalance in the crosstalk between the host and gut microbiota affects the intestinal barrier function, which results in inflammatory diseases and colorectal cancer. The colon epithelium protects itself from a harsh environment and various pathogenic organisms by forming a double mucus layer, primarily comprising mucins. Recent studies are focusing on how dietary patterns alter the gut microbiota composition, which in turn regulates mucin expression and maintains the intestinal layers. In addition, modulation of gut microbiota by microbiotic therapy (involving fecal microbiota transplantation) has emerged as a significant factor in the pathologies associated with dysbiosis. Therefore, proper communication between host …

Small-Molecule Inhibitor Of Af9/Enl-Dot1l/Af4/Aff4 Interactions Suppresses Malignant Gene Expression And Tumor Grow, Fangrui Wu, Shenyou Nie, Yuan Yao, Tong Huo, Xin Li, Xiaowei Wu, Jidong Zhao, Yi-Lun Lin, Yinjie Zhang, Qianxing Mo, Yongcheng Song

Faculty, Staff and Students Publications

Chromosome translocations involving mixed lineage leukemia (MLL) gene cause acute leukemia with a poor prognosis. MLL is frequently fused with transcription cofactors AF4 (~35%), AF9 (25%) or its paralog ENL (10%). The AHD domain of AF9/ENL binds to AF4, its paralog AFF4, or histone-H3 lysine-79 (H3K79) methyltransferase DOT1L. Formation of AF9/ENL/AF4/AFF4-containing super elongation complexes (SEC) and the catalytic activity of DOT1L are essential for MLL-rearranged leukemia. Protein-protein interactions (PPI) between AF9/ENL and DOT1L/AF4/AFF4 are therefore a potential drug target.

Methods: Compound screening followed by medicinal chemistry was used to find inhibitors of such PPIs, which were examined for their biological …

Lrrtm4 Is A Member Of The Transsynaptic Complex Between Rod Photoreceptors And Bipolar Cells, Melina A Agosto, Theodore G Wensel

Faculty, Staff and Students Publications

Leucine rich repeat transmembrane (LRRTM) proteins are synaptic adhesion molecules with roles in synapse formation and signaling. LRRTM4 transcripts were previously shown to be enriched in rod bipolar cells (BCs), secondary neurons of the retina that form synapses with rod photoreceptors. Using two different antibodies, LRRTM4 was found to reside primarily at rod BC dendritic tips, where it colocalized with the transduction channel protein, TRPM1. LRRTM4 was not detected at dendritic tips of ON-cone BCs. Following somatic knockout of LRRTM4 in BCs by subretinal injection and electroporation of CRISPR/Cas9, LRRTM4 was abolished or reduced in the dendritic tips of transfected …

A Steroid Receptor Coactivator Stimulator (Mcb-613) Attenuates Adverse Remodeling After Myocardial Infarction, Lisa K Mullany, Aarti D Rohira, John P Leach, Jong H Kim, Tanner O Monroe, Andrea R Ortiz, Brittany Stork, M Waleed Gaber, Poonam Sarkar, Andrew G Sikora, Todd K Rosengart, Brian York, Yongcheng Song, Clifford C Dacso, David M Lonard, James F Martin, Bert W O'Malley

Faculty, Staff and Students Publications

Progressive remodeling of the heart, resulting in cardiomyocyte (CM) loss and increased inflammation, fibrosis, and a progressive decrease in cardiac function, are hallmarks of myocardial infarction (MI)-induced heart failure. We show that MCB-613, a potent small molecule stimulator of steroid receptor coactivators (SRCs) attenuates pathological remodeling post-MI. MCB-613 decreases infarct size, apoptosis, hypertrophy, and fibrosis while maintaining significant cardiac function. MCB-613, when given within hours post MI, induces lasting protection from adverse remodeling concomitant with: 1) inhibition of macrophage inflammatory signaling and interleukin 1 (IL-1) signaling, which attenuates the acute inflammatory response, 2) attenuation of fibroblast differentiation, and 3) promotion …

Mouse Models To Study The Pathophysiology Of Combined Methylmalonic Acidemia And Homocystinuria, Cblc Type, Tiffany Chern, Annita Achilleos, Xuefei Tong, Chih-Wei Hsu, Leeyean Wong, Ross A Poché

Faculty, Staff and Students Publications

Combined methylmalonic acidemia and homocystinuria, cblC type, is the most common inherited disorder of cobalamin metabolism and is characterized by severe fetal developmental defects primarily impacting the central nervous system, hematopoietic system, and heart. CblC was previously shown to be due to mutations in the MMACHC gene, which encodes a protein thought to function in intracellular cobalamin trafficking and biosynthesis of adenosylcobalamin (AdoCbl) and methylcobalamin (MeCbl). These coenzymes are required for the production of succinyl-CoA and methionine, respectively. However, it is currently unclear whether additional roles for MMACHC exist outside of cobalamin metabolism. Furthermore, due to a lack of sufficient …

Depletion Of Essential Isoprenoids And Er Stress Induction Following Acute Liver-Specific Deletion Of Hmg-Coa Reductase, Marco De Giorgi, Kelsey E Jarrett, Jason C Burton, Alexandria M Doerfler, Ayrea Hurley, Ang Li, Rachel H Hsu, Mia Furgurson, Kalyani R Patel, Jun Han, Christoph H Borchers, William R Lagor

Faculty, Staff and Students Publications

HMG-CoA reductase (Hmgcr) is the rate-limiting enzyme in the mevalonate pathway and is inhibited by statins. In addition to cholesterol, Hmgcr activity is also required for synthesizing nonsterol isoprenoids, such as dolichol, ubiquinone, and farnesylated and geranylgeranylated proteins. Here, we investigated the effects of Hmgcr inhibition on nonsterol isoprenoids in the liver. We have generated new genetic models to acutely delete genes in the mevalonate pathway in the liver using AAV-mediated delivery of Cre-recombinase (AAV-Cre) or CRISPR/Cas9 (AAV-CRISPR). The genetic deletion of Hmgcr by AAV-Cre resulted in extensive hepatocyte apoptosis and compensatory liver regeneration. At the biochemical …

Role For Carbohydrate Response Element-Binding Protein (Chrebp) In High Glucose-Mediated Repression Of Long Noncoding Rna Tug1, Jianyin Long, Daniel L Galvan, Koki Mise, Yashpal S Kanwar, Li Li, Naravat Poungavrin, Paul A Overbeek, Benny H Chang, Farhad R Danesh

Faculty, Staff and Students Publications

Long noncoding RNAs (lncRNAs) have been shown to play key roles in a variety of biological activities of the cell. However, less is known about how lncRNAs respond to environmental cues and what transcriptional mechanisms regulate their expression. Studies from our laboratory have shown that the lncRNA Tug1 (taurine upregulated gene 1) is crucial for the progression of diabetic kidney disease, a major microvascular complication of diabetes. Using a combination of proximity labeling with the engineered soybean ascorbate peroxidase (APEX2), ChIP-qPCR, biotin-labeled oligonucleotide pulldown, and classical promoter luciferase assays in kidney podocytes, we extend our initial observations in the current …

Ryanodine Receptor 1-Related Disorders: An Historical Perspective And Proposal For A Unified Nomenclature, Tokunbor A Lawal, Joshua J Todd, Jessica W Witherspoon, Carsten G Bönnemann, James J Dowling, Susan L Hamilton, Katherine G Meilleur, Robert T Dirksen

Faculty, Staff and Students Publications

The RYR1 gene, which encodes the sarcoplasmic reticulum calcium release channel or type 1 ryanodine receptor (RyR1) of skeletal muscle, was sequenced in 1988 and RYR1 variations that impair calcium homeostasis and increase susceptibility to malignant hyperthermia were first identified in 1991. Since then, RYR1-related myopathies (RYR1-RM) have been described as rare, histopathologically and clinically heterogeneous, and slowly progressive neuromuscular disorders. RYR1 variants can lead to dysfunctional RyR1-mediated calcium release, malignant hyperthermia susceptibility, elevated oxidative stress, deleterious post-translational modifications, and decreased RyR1 expression. RYR1-RM-affected individuals can present with delayed motor milestones, contractures, scoliosis, ophthalmoplegia, and respiratory insufficiency.Historically, RYR1-RM-affected individuals were …

Myosight-Semi-Automated Image Analysis Of Skeletal Muscle Cross Sections, Lyle W Babcock, Amy D Hanna, Nadia H Agha, Susan L Hamilton

Faculty, Staff and Students Publications

BACKGROUND: Manual analysis of cross-sectional area, fiber-type distribution, and total and centralized nuclei in skeletal muscle cross sections is tedious and time consuming, necessitating an accurate, automated method of analysis. While several excellent programs are available, our analyses of skeletal muscle disease models suggest the need for additional features and flexibility to adequately describe disease pathology. We introduce a new semi-automated analysis program, MyoSight, which is designed to facilitate image analysis of skeletal muscle cross sections and provide additional flexibility in the analyses.

RESULTS: We describe staining and imaging methods that generate high-quality images of immunofluorescent-labelled cross sections from mouse …

Structural Basis Of Ion Transport And Inhibition In Ferroportin, Yaping Pan, Zhenning Ren, Shuai Gao, Jiemin Shen, Lie Wang, Zhichun Xu, Ye Yu, Preetham Bachina, Hanzhi Zhang, Xiao Fan, Arthur Laganowsky, Nieng Yan, Ming Zhou

Faculty, Staff and Students Publications

Ferroportin is an iron exporter essential for releasing cellular iron into circulation. Ferroportin is inhibited by a peptide hormone, hepcidin. In humans, mutations in ferroportin lead to ferroportin diseases that are often associated with accumulation of iron in macrophages and symptoms of iron deficiency anemia. Here we present the structures of the ferroportin from the primate Philippine tarsier (TsFpn) in the presence and absence of hepcidin solved by cryo-electron microscopy. TsFpn is composed of two domains resembling a clamshell and the structure defines two metal ion binding sites, one in each domain. Both structures are in an outward-facing conformation, and …

Young Versus Aged Microbiota Transplants To Germ-Free Mice: Increased Short-Chain Fatty Acids And Improved Cognitive Performance, Juneyoung Lee, Venugopal R Venna, David J Durgan, Huanan Shi, Jacob Hudobenko, Nagireddy Putluri, Joseph Petrosino, Louise D Mccullough, Robert M Bryan

Faculty, Staff and Students Publications

Aging is associated with cognitive decline and decreased concentrations of short-chain fatty acids (SCFAs) in the gut. SCFAs are significant in that they are protective to the gut and other organs. We tested the hypothesis that the aged gut microbiome alone is sufficient to decrease SCFAs in the host and produce cognitive decline. Fecal transplant gavages (FTGs) from aged (18–20 months) or young (2–3 months) male C57BL/6 mice into germ-free male C57BL/6 mice (N = 11 per group) were initiated at ~3 months of age. Fecal samples were collected and behavioral testing was performed over the study period. Bacterial community …

Zmat3 Is A Key Splicing Regulator In The P53 Tumor Suppression Program, Kathryn T Bieging-Rolett, Alyssa M Kaiser, David W Morgens, Anthony M Boutelle, Jose A Seoane, Eric L Van Nostrand, Changyu Zhu, Shauna L Houlihan, Stephano S Mello, Brian A Yee, Jacob Mcclendon, Sarah E Pierce, Ian P Winters, Mengxiong Wang, Andrew J Connolly, Scott W Lowe, Christina Curtis, Gene W Yeo, Monte M Winslow, Michael C Bassik, Laura D Attardi

Faculty, Staff and Students Publications

Although TP53 is the most commonly mutated gene in human cancers, the p53-dependent transcriptional programs mediating tumor suppression remain incompletely understood. Here, to uncover critical components downstream of p53 in tumor suppression, we perform unbiased RNAi and CRISPR-Cas9-based genetic screens in vivo. These screens converge upon the p53-inducible gene Zmat3, encoding an RNA-binding protein, and we demonstrate that ZMAT3 is an important tumor suppressor downstream of p53 in mouse Kras

Adaptive Thermogenesis Enhances The Life-Threatening Response To Heat In Mice With An Ryr1 Mutation, Hui J Wang, Chang Seok Lee, Rachel Sue Zhen Yee, Linda Groom, Inbar Friedman, Lyle Babcock, Dimitra K Georgiou, Jin Hong, Amy D Hanna, Joseph Recio, Jong Min Choi, Ting Chang, Nadia H Agha, Jonathan Romero, Poonam Sarkar, Nicol Voermans, M Waleed Gaber, Sung Yun Jung, Matthew L Baker, Robia G Pautler, Robert T Dirksen, Sheila Riazi, Susan L Hamilton

Faculty, Staff and Students Publications

Mutations in the skeletal muscle Ca2+ release channel, the type 1 ryanodine receptor (RYR1), cause malignant hyperthermia susceptibility (MHS) and a life-threatening sensitivity to heat, which is most severe in children. Mice with an MHS-associated mutation in Ryr1 (Y524S, YS) display lethal muscle contractures in response to heat. Here we show that the heat response in the YS mice is exacerbated by brown fat adaptive thermogenesis. In addition, the YS mice have more brown adipose tissue thermogenic capacity than their littermate controls. Blood lactate levels are elevated in both heat-sensitive MHS patients with RYR1 mutations and YS mice due to …

Mir-30a Targets Gene Networks That Promote Browning Of Human And Mouse Adipocytes, Pradip K Saha, Mark P Hamilton, Kimal Rajapakshe, Vasanta Putluri, Jessica B Felix, Peter Masschelin, Aaron R Cox, Mandeep Bajaj, Nagireddy Putluri, Cristian Coarfa, Sean M Hartig

Faculty, Staff and Students Publications

MicroRNA-30a (miR-30a) impacts adipocyte function, and its expression in white adipose tissue (WAT) correlates with insulin sensitivity in obesity. Bioinformatic analysis demonstrates that miR-30a expression contributes to 2% of all miRNA expression in human tissues. However, molecular mechanisms of miR-30a function in fat cells remain unclear. Here, we expanded our understanding of how miR-30a expression contributes to antidiabetic peroxisome proliferator-activated receptor-γ (PPARγ) agonist activity and metabolic functions in adipocytes. We found that WAT isolated from diabetic patients shows reduced miR-30a levels and diminished expression of the canonical PPARγ target genes ADIPOQ and FABP4 relative to lean counterparts. In human adipocytes, …

An Autism-Linked Missense Mutation In Shank3 Reveals The Modularity Of Shank3 Function, Li Wang, Kaifang Pang, Kihoon Han, Carolyn J Adamski, Wei Wang, Lingjie He, Jason K Lai, Vitaliy V Bondar, Joseph G Duman, Ronald Richman, Kimberley F Tolias, Patrick Barth, Timothy Palzkill, Zhandong Liu, J Lloyd Holder, Huda Y Zoghbi

Faculty, Staff and Students Publications

Genome sequencing has revealed an increasing number of genetic variations that are associated with neuropsychiatric disorders. Frequently, studies limit their focus to likely gene-disrupting mutations because they are relatively easy to interpret. Missense variants, instead, have often been undervalued. However, some missense variants can be informative for developing a more profound understanding of disease pathogenesis and ultimately targeted therapies. Here we present an example of this by studying a missense variant in a well-known autism spectrum disorder (ASD) causing gene SHANK3. We analyzed Shank3's in vivo phosphorylation profile and identified S685 as one phosphorylation site where one ASD-linked variant has …

Ampk Regulation Of Raptor And Tsc2 Mediate Metformin Effects On Transcriptional Control Of Anabolism And Inflammation, Jeanine L Van Nostrand, Kristina Hellberg, En-Ching Luo, Eric L Van Nostrand, Alina Dayn, Jingting Yu, Maxim N Shokhirev, Yelena Dayn, Gene W Yeo, Reuben J Shaw

Faculty, Staff and Students Publications

Despite being the frontline therapy for type 2 diabetes, the mechanisms of action of the biguanide drug metformin are still being discovered. In particular, the detailed molecular interplays between the AMPK and the mTORC1 pathway in the hepatic benefits of metformin are still ill defined. Metformin-dependent activation of AMPK classically inhibits mTORC1 via TSC/RHEB, but several lines of evidence suggest additional mechanisms at play in metformin inhibition of mTORC1. Here we investigated the role of direct AMPK-mediated serine phosphorylation of RAPTOR in a new

Atrial Myocyte Nlrp3/Camkii Nexus Forms A Substrate For Postoperative Atrial Fibrillation, Jordi Heijman, Azinwi Phina Muna, Tina Veleva, Cristina E Molina, Henry Sutanto, Marcel Tekook, Qiongling Wang, Issam H Abu-Taha, Marcel Gorka, Stephan Künzel, Ali El-Armouche, Hermann Reichenspurner, Markus Kamler, Viacheslav Nikolaev, Ursula Ravens, Na Li, Stanley Nattel, Xander H T Wehrens, Dobromir Dobrev

Faculty, Staff and Students Publications

RATIONALE: Postoperative atrial fibrillation (POAF) is a common and troublesome complication of cardiac surgery. POAF is generally believed to occur when postoperative triggers act on a preexisting vulnerable substrate, but the underlying cellular and molecular mechanisms are largely unknown.

OBJECTIVE: To identify cellular POAF mechanisms in right atrial samples from patients without a history of atrial fibrillation undergoing open-heart surgery.

METHODS AND RESULTS: Multicellular action potentials, membrane ion-currents (perforated patch-clamp), or simultaneous membrane-current (ruptured patch-clamp) and [Ca

CONCLUSIONS: Preexisting Ca

Loss Of Speg Inhibitory Phosphorylation Of Ryanodine Receptor Type-2 Promotes Atrial Fibrillation, Hannah M Campbell, Ann P Quick, Issam Abu-Taha, David Y Chiang, Carlos F Kramm, Tarah A Word, Sören Brandenburg, Mohit Hulsurkar, Katherina M Alsina, Hui-Bin Liu, Brian Martin, Dennis Uhlenkamp, Oliver M Moore, Satadru K Lahiri, Eleonora Corradini, Markus Kamler, Albert J R Heck, Stephan E Lehnart, Dobromir Dobrev, Xander H T Wehrens

Faculty, Staff and Students Publications

BACKGROUND: Enhanced diastolic calcium (Ca

METHODS: Western blotting was performed with right atrial biopsies from patients with paroxysmal AF. SPEG atrial knockout mice were generated using adeno-associated virus 9. In mice, AF inducibility was determined using intracardiac programmed electric stimulation, and diastolic Ca

RESULTS: Western blotting revealed decreased SPEG protein levels in atrial biopsies from patients with paroxysmal AF in comparison with patients in sinus rhythm. SPEG atrial-specific knockout mice exhibited increased susceptibility to pacing-induced AF by programmed electric stimulation and enhanced Ca

CONCLUSIONS: Unlike other kinases (PKA, CaMKII) that increase RyR2 activity, SPEG phosphorylation reduces RyR2-mediated sarcoplasmic reticulum Ca

Characterization Of Retinal Biomechanical Properties Using Brillouin Microscopy, Yogeshwari S Ambekar, Manmohan Singh, Giuliano Scarcelli, Elda M Rueda, Benjamin M Hall, Ross A Poché, Kirill V Larin

Faculty, Staff and Students Publications

SIGNIFICANCE: The retina is critical for vision, and several diseases may alter its biomechanical properties. However, assessing the biomechanical properties of the retina nondestructively is a challenge due to its fragile nature and location within the eye globe. Advancements in Brillouin spectroscopy have provided the means for nondestructive investigations of retina biomechanical properties.

AIM: We assessed the biomechanical properties of mouse retinas using Brillouin microscopy noninvasively and showed the potential of Brillouin microscopy to differentiate the type and layers of retinas based on stiffness.

APPROACH: We used Brillouin microscopy to quantify stiffness of fresh and paraformaldehyde (PFA)-fixed retinas. As further …

Mtor-Initiated Metabolic Switch And Degeneration In The Retinal Pigment Epithelium, Young-Mi Go, Jing Zhang, Jolyn Fernandes, Christopher Litwin, Rui Chen, Theodore G Wensel, Dean P Jones, Jiyang Cai, Yan Chen

Faculty, Staff and Students Publications

The retinal pigment epithelium (RPE) is a particularly vulnerable tissue to age-dependent degeneration. Over the life span, the RPE develops an expanded endo-lysosomal compartment to maintain the high efficiency of phagocytosis and degradation of photoreceptor outer segments (POS) necessary for photoreceptor survival. As the assembly and activation of the mechanistic target of rapamycin complex 1 (mTORC1) occur on the lysosome surface, increased lysosome mass with aging leads to higher mTORC1 activity. The functional consequences of hyperactive mTORC1 in the RPE are unclear. In the current study, we used integrated high-resolution metabolomic and genomic approaches to examine mice with RPE-specific deletion …

Structure And Mechanism Of A Unique Diiron Center In Mammalian Stearoyl-Coa Desaturase, Jiemin Shen, Gang Wu, Ah-Lim Tsai, Ming Zhou

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Stearoyl-CoA desaturase 1 (SCD1) is a membrane-embedded metalloenzyme that catalyzes formation of a double-bond on a saturated acyl-CoA. SCD1 has a diiron center and its proper function requires an electron transport chain composed of NADH (or NADPH), cytochrome b5 reductase (b5R), and cytochrome b5 (cyt b5). Since SCD1 is a key regulator in fat metabolism and is required for survival of cancer cells, there is intense interest in targeting SCD1 for various metabolic diseases and cancers. Crystal structures of human and mouse SCD1 were reported recently, however, both proteins have two zinc ions instead of two iron ions in the …

Metabolism Of Jq1, An Inhibitor Of Bromodomain And Extra Terminal Bromodomain Proteins, In Human And Mouse Liver Microsomes†, Feng Li, Kevin R Mackenzie, Prashi Jain, Conrad Santini, Damian W Young, Martin M Matzuk

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JQ1 is a small-molecule inhibitor of the bromodomain and extra terminal (BET) protein family that potently inhibits the bromodomain testis-specific protein (BRDT), which is essential for spermatogenesis. JQ1 treatment produces a reversible contraceptive effect by targeting the activity of BRDT in mouse male germ cells, validating BRDT as a male contraceptive target. Although JQ1 possesses favourable physical properties, it exhibits a short half-life. Because the details of xenobiotic metabolism play important roles in the optimization of drug candidates and in determining the role of metabolism in drug efficacy, we investigated the metabolism of JQ1 in human and mouse liver microsomes. …

A Global Slc7a7 Knockout Mouse Model Demonstrates Characteristic Phenotypes Of Human Lysinuric Protein Intolerance, Bridget M Stroup, Ronit Marom, Xiaohui Li, Chih-Wei Hsu, Cheng-Yen Chang, Luan D Truong, Brian Dawson, Ingo Grafe, Yuqing Chen, Ming-Ming Jiang, Denise Lanza, Jennie Rose Green, Qin Sun, J P Barrish, Safa Ani, Audrey E Christiansen, John R Seavitt, Mary E Dickinson, Farrah Kheradmand, Jason D Heaney, Brendan Lee, Lindsay C Burrage

Faculty, Staff and Students Publications

Lysinuric protein intolerance (LPI) is an inborn error of cationic amino acid (arginine, lysine, ornithine) transport caused by biallelic pathogenic variants in SLC7A7, which encodes the light subunit of the y+LAT1 transporter. Treatments for the complications of LPI, including growth failure, renal disease, pulmonary alveolar proteinosis, autoimmune disorders and osteoporosis, are limited. Given the early lethality of the only published global Slc7a7 knockout mouse model, a viable animal model to investigate global SLC7A7 deficiency is needed. Hence, we generated two mouse models with global Slc7a7 deficiency (Slc7a7em1Lbu/em1Lbu; Slc7a7Lbu/Lbu and Slc7a7em1(IMPC)Bay/em1(IMPC)Bay; Slc7a7Bay/Bay) using CRISPR/Cas9 technology by introducing a deletion of exons …