Medicine and Health Sciences Commons^™

Gasdermins In Apoptosis: New Players In An Old Game., Corey Rogers, Emad S. Alnemri

Department of Biochemistry and Molecular Biology Faculty Papers

Apoptosis is a form of programmed cell death (PCD) that plays critical physiological roles in removing superfluous or dangerous cell populations that are unneeded or threatening to the health of the host organism. Although the molecular pathways leading to activation of the apoptotic program have been extensively studied and characterized starting in the 1970s, new evidence suggests that members of the gasdermin superfamily are novel pore-forming proteins that augment apoptosis by permeabilizing the mitochondria and participate in the final stages of the apoptotic program by inducing secondary necrosis/pyroptosis. These findings may explain outstanding questions in the field such as why …

Allele-Specific Rna Interference Prevents Neuropathy In Charcot-Marie-Tooth Disease Type 2d Mouse Models., Kathryn H Morelli, Laurie B Griffin, Nettie K Pyne, Lindsay M Wallace, Allison M Fowler, Stephanie N Oprescu, Ryuichi Takase, Na Wei, Rebecca Meyer-Schuman, Dattatreya Mellacheruvu, Jacob O Kitzman, Samuel G Kocen, Timothy J Hines, Emily L Spaulding, James R Lupski, Alexey Nesvizhskii, Pedro Mancias, Ian J Butler, Xiang-Lei Yang, Ya-Ming Hou, Anthony Antonellis, Scott Q Harper, Robert W Burgess

Department of Biochemistry and Molecular Biology Faculty Papers

Gene therapy approaches are being deployed to treat recessive genetic disorders by restoring the expression of mutated genes. However, the feasibility of these approaches for dominantly inherited diseases - where treatment may require reduction in the expression of a toxic mutant protein resulting from a gain-of-function allele - is unclear. Here we show the efficacy of allele-specific RNAi as a potential therapy for Charcot-Marie-Tooth disease type 2D (CMT2D), caused by dominant mutations in glycyl-tRNA synthetase (GARS). A de novo mutation in GARS was identified in a patient with a severe peripheral neuropathy, and a mouse model precisely recreating the mutation …

Characterization Of Resistance To A Potent D-Peptide Hiv Entry Inhibitor., Amanda R Smith, Matthew T Weinstock, Amanda E Siglin, Frank G Whitby, J Nicholas Francis, Christopher P Hill, Debra M Eckert, Michael J Root, Michael S Kay

Department of Biochemistry and Molecular Biology Faculty Papers

BACKGROUND: PIE12-trimer is a highly potent D-peptide HIV-1 entry inhibitor that broadly targets group M isolates. It specifically binds the three identical conserved hydrophobic pockets at the base of the gp41 N-trimer with sub-femtomolar affinity. This extremely high affinity for the transiently exposed gp41 trimer provides a reserve of binding energy (resistance capacitor) to prevent the viral resistance pathway of stepwise accumulation of modest affinity-disrupting mutations. Such modest mutations would not affect PIE12-trimer potency and therefore not confer a selective advantage. Viral passaging in the presence of escalating PIE12-trimer concentrations ultimately selected for PIE12-trimer resistant populations, but required an extremely …

Structural And Functional Analysis Of Parameters Governing Tankyrase-1 Interaction With Telomeric Repeat-Binding Factor 1 And Gdp-Mannose 4,6-Dehydratase., Travis Eisemann, Marie-France Langelier, John M. Pascal

Department of Biochemistry and Molecular Biology Faculty Papers

Human tankyrase-1 (TNKS) is a member of the poly(ADPribose) polymerase (PARP) superfamily of proteins that posttranslationally modify themselves and target proteins with ADP-ribose (termed PARylation). The TNKS ankyrin repeat domain mediates interactions with a growing number of structurally and functionally diverse binding partners, linking TNKS activity to multiple critical cell processes, including Wnt signaling, Golgi trafficking, and telomere maintenance. However, some binding partners can engage TNKS without being modified, suggesting that separate parameters influence TNKS interaction and PARylation. Here, we present an analysis of the sequence and structural features governing TNKS interactions with two model binding partners: The PARylated partner …

Heme And Hemoglobin Utilization By Mycobacterium Tuberculosis., Avishek Mitra, Ying-Hui Ko, Gino Cingolani, Michael Niederweis

Department of Biochemistry and Molecular Biology Faculty Papers

Iron is essential for growth of Mycobacterium tuberculosis (Mtb), but most iron in the human body is stored in heme within hemoglobin. Here, we demonstrate that the substrate-binding protein DppA of the inner membrane Dpp transporter is required for heme and hemoglobin utilization by Mtb. The 1.27 Å crystal structure of DppA shows a tetrapeptide bound in the protein core and a large solvent-exposed crevice for heme binding. Mutation of arginine 179 in this cleft eliminates heme binding to DppA and prevents heme utilization by Mtb. The outer membrane proteins PPE36 and PPE62 are also required for heme and hemoglobin …

Structural Basis For The Homotypic Fusion Of Chlamydial Inclusions By The Snare-Like Protein Inca., Gino Cingolani, Michael Mccauley, Anna Lobley, Alexander J Bryer, Jordan Wesolowski, Deanna L Greco, Ravi K Lokareddy, Erik Ronzone, Juan R Perilla, Fabienne Paumet

Department of Biochemistry and Molecular Biology Faculty Papers

Many intracellular bacteria, including Chlamydia, establish a parasitic membrane-bound organelle inside the host cell that is essential for the bacteria's survival. Chlamydia trachomatis forms inclusions that are decorated with poorly characterized membrane proteins known as Incs. The prototypical Inc, called IncA, enhances Chlamydia pathogenicity by promoting the homotypic fusion of inclusions and shares structural and functional similarity to eukaryotic SNAREs. Here, we present the atomic structure of the cytoplasmic domain of IncA, which reveals a non-canonical four-helix bundle. Structure-based mutagenesis, molecular dynamics simulation, and functional cellular assays identify an intramolecular clamp that is essential for IncA-mediated homotypic membrane fusion during …

A Unique Role For Clathrin Light Chain A In Cell Spreading And Migration., Oxana M. Tsygankova, James H. Keen

Department of Biochemistry and Molecular Biology Faculty Papers

Clathrin heavy chain is the structural component of the clathrin triskelion, but unique functions for the two distinct and highly conserved clathrin light chains (CLCa and CLCb, also known as CLTA and CLTB, respectively) have been elusive. Here, we show that following detachment and replating, CLCa is uniquely responsible for promoting efficient cell spreading and migration. Selective depletion of CLCa, but not of CLCb, reduced the initial phase of isotropic spreading of HeLa, H1299 and HEK293 cells by 60-80% compared to siRNA controls, and wound closure and motility by ∼50%. Surface levels of β1-integrins were unaffected by CLCa depletion. However, …

Yeast Mitochondrial Protein Pet111p Binds Directly To Two Distinct Targets In Cox2 Mrna, Suggesting A Mechanism Of Translational Activation, Julia L Jones, Katharina B. Hofmann, Andrew T. Cowan, Dmitry Temiakov, Patrick Cramer, Michael Anikin

Department of Biochemistry and Molecular Biology Faculty Papers

The genes in mitochondrial DNA code for essential subunits of the respiratory chain complexes. In yeast, expression of mitochondrial genes is controlled by a group of gene-specific translational activators encoded in the nucleus. These factors appear to be part of a regulatory system that enables concerted expression of the necessary genes from both nuclear and mitochondrial genomes to produce functional respiratory complexes. Many of the translational activators are believed to act on the 5'-untranslated regions of target mRNAs, but the molecular mechanisms involved in this regulation remain obscure. In this study, we used a combination of in vivo and in …

Trna Methylation Is A Global Determinant Of Bacterial Multi-Drug Resistance., Isao Masuda, Ryuma Matsubara, Thomas Christian, Enrique R. Rojas, Srujana S. Yadavalli, Lisheng Zhang, Mark Goulian, Leonard J. Foster, Kerwyn Casey Huang, Ya-Ming Hou

Department of Biochemistry and Molecular Biology Faculty Papers

Gram-negative bacteria are intrinsically resistant to drugs because of their double-membrane envelope structure that acts as a permeability barrier and as an anchor for efflux pumps. Antibiotics are blocked and expelled from cells and cannot reach high-enough intracellular concentrations to exert a therapeutic effect. Efforts to target one membrane protein at a time have been ineffective. Here, we show that m ¹ G37-tRNA methylation determines the synthesis of a multitude of membrane proteins via its control of translation at proline codons near the start of open reading frames. Decreases in m ¹ G37 levels in Escherichia coli and Salmonella impair …

Gasdermin Pores Permeabilize Mitochondria To Augment Caspase-3 Activation During Apoptosis And Inflammasome Activation., Corey Rogers, Dan A. Erkes, Alexandria Nardone, Andrew E. Aplin, Teresa Fernandes-Alnemri, Emad S. Alnemri

Department of Biochemistry and Molecular Biology Faculty Papers

Gasdermin E (GSDME/DFNA5) cleavage by caspase-3 liberates the GSDME-N domain, which mediates pyroptosis by forming pores in the plasma membrane. Here we show that GSDME-N also permeabilizes the mitochondrial membrane, releasing cytochrome c and activating the apoptosome. Cytochrome c release and caspase-3 activation in response to intrinsic and extrinsic apoptotic stimuli are significantly reduced in GSDME-deficient cells comparing with wild type cells. GSDME deficiency also accelerates cell growth in culture and in a mouse model of melanoma. Phosphomimetic mutation of the highly conserved phosphorylatable Thr6 residue of GSDME, inhibits its pore-forming activity, thus uncovering a potential mechanism by which GSDME …

Loss-Of-Function Mutations In Lysyl-Trna Synthetase Cause Various Leukoencephalopathy Phenotypes, Chong Sun, Jie Song, Yanjun Jiang, Chongbo Zhao, Jiahong Lu, Yuxin Li, Yin Wang, Mingshi Gao, Jianying Xi, Sushan Luo, Meixia Li, Kevin Donaldson, Stephanie N. Oprescu, Thomas P. Slavin, Sansan Lee, Pilar L. Magoulas, Andrea M. Lewis, Lisa Emrick, Seema R. Lalani, Zhiyv Niu, Megan L. Landsverk, Magdalena Walkiewicz, Richard E. Person, Hui Mei, Jill A. Rosenfeld, Yaping Yang, Anthony Antonellis, Ya-Ming Hou, Jie Lin, Victor W. Zhang

Department of Biochemistry and Molecular Biology Faculty Papers

Objective: To expand the clinical spectrum of lysyl-tRNA synthetase (KARS) gene–related diseases, which so far includes Charcot-Marie-Tooth disease, congenital visual impairment and microcephaly, and nonsyndromic hearing impairment.

Methods: Whole-exome sequencing was performed on index patients from 4 unrelated families with leukoencephalopathy. Candidate pathogenic variants and their cosegregation were confirmed by Sanger sequencing. Effects of mutations on KARS protein function were examined by aminoacylation assays and yeast complementation assays.

Results: Common clinical features of the patients in this study included impaired cognitive ability, seizure, hypotonia, ataxia, and abnormal brain imaging, suggesting that the CNS involvement is the main …

Interaction Between The Bag1s Isoform And Hsp70 Mediates The Stability Of Anti-Apoptotic Proteins And The Survival Of Osteosarcoma Cells Expressing Oncogenic Myc., Victoria J. Gennaro, Helen Wedegaertner, Steven B. Mcmahon

Department of Biochemistry and Molecular Biology Faculty Papers

BACKGROUND: The oncoprotein MYC has the dual capacity to drive cell cycle progression or induce apoptosis, depending on the cellular context. BAG1 was previously identified as a transcriptional target of MYC that functions as a critical determinant of this cell fate decision. The BAG1 protein is expressed as multiple isoforms, each having an array of distinct biochemical functions; however, the specific effector function of BAG1 that directs MYC-dependent cell survival has not been defined.

METHODS: In our studies the human osteosarcoma line U2OS expressing a conditional MYC-ER allele was used to induce oncogenic levels of MYC. We interrogated MYC-driven survival …

Impaired Nuclear Export Of Polyglutamine-Expanded Androgen Receptor In Spinal And Bulbar Muscular Atrophy., Frederick J. Arnold, Anna Pluciennik, Diane E. Merry

Department of Biochemistry and Molecular Biology Faculty Papers

Spinal and bulbar muscular atrophy (SBMA) is a neuromuscular disease caused by polyglutamine (polyQ) expansion in the androgen receptor (AR). Prior studies have highlighted the importance of AR nuclear localization in SBMA pathogenesis; therefore, in this study, we sought to determine the role of AR nuclear export in the pathological manifestations of SBMA. We demonstrate here that the nuclear export of polyQ-expanded AR is impaired, even prior to the formation of intranuclear inclusions of aggregated AR. Additionally, we find that promoting AR export with an exogenous nuclear export signal substantially reduces its aggregation and blocks hormone-induced toxicity. Moreover, we show …

Codon-Specific Translation By M1g37 Methylation Of Trna, Ya-Ming Hou, Isao Masuda, Howard Gamper

Department of Biochemistry and Molecular Biology Faculty Papers

Although the genetic code is degenerate, synonymous codons for the same amino acid are not translated equally. Codon-specific translation is important for controlling gene expression and determining the proteome of a cell. At the molecular level, codon-specific translation is regulated by post-transcriptional epigenetic modifications of tRNA primarily at the wobble position 34 and at position 37 on the 3′-side of the anticodon. Modifications at these positions determine the quality of codon-anticodon pairing and the speed of translation on the ribosome. Different modifications operate in distinct mechanisms of codon-specific translation, generating a diversity of regulation that is previously unanticipated. Here we …