Perturbation of synapsins homeostasis through HIV-1 Tat-mediated suppression of BAG3 in primary neuronal cells
AuthorMohseni Ahooyi, T
SubjectAdaptor Proteins, Signal Transducing
Apoptosis Regulatory Proteins
Autophagy-Related Protein 5
tat Gene Products, Human Immunodeficiency Virus
Permanent link to this recordhttp://hdl.handle.net/20.500.12613/4545
MetadataShow full item record
Abstract© 2019, The Author(s). HIV-1 Tat is known to be released by HIV infected non-neuronal cells in the brain, and after entering neurons, compromises brain homeostasis by impairing pro-survival pathways, thus contributing to the development of HIV-associated CNS disorders commonly observed in individuals living with HIV. Here, we demonstrate that synapsins, phosphoproteins that are predominantly expressed in neuronal cells and play a vital role in modulating neurotransmitter release at the pre-synaptic terminal, and neuronal differentiation become targets for Tat through autophagy and protein quality control pathways. We demonstrate that the presence of Tat in neurons results in downregulation of BAG3, a co-chaperone for heat shock proteins (Hsp70/Hsc70) that is implicated in protein quality control (PQC) processes by eliminating mis-folded and damaged proteins, and selective macroautophagy. Our results show that treatment of cells with Tat or suppression of BAG3 expression by siRNA in neuronal cells disturbs subcellular distribution of synapsins and synaptotagmin 1 (Syt1) leading to their accumulation in the neuronal soma and along axons in a punctate pattern, rather than being properly distributed at axon-terminals. Further, our results revealed that synapsins partially lost their stability and their removal via lysosomal autophagy was noticeably impaired in cells with low levels of BAG3. The observed impairment of lysosomal autophagy, under this condition, is likely caused by cells losing their ability to process LC3-I to LC3-II, in part due to a decrease in the ATG5 levels upon BAG3 knockdown. These observations ascribe a new function for BAG3 in controlling synaptic communications and illuminate a new downstream target for Tat to elicit its pathogenic effect in impacting neuronal cell function and behavior.
Citation to related workSpringer Science and Business Media LLC
Has partCell Death and Disease
ADA complianceFor Americans with Disabilities Act (ADA) accommodation, including help with reading this content, please contact email@example.com
Showing items related by title, author, creator and subject.
Expanding the Spiroligomers Toolbox as Protein-Protein Interaction InhibitorsSchafmeister, Christian; Valentine, Ann M.; Andrade, Rodrigo B.; Schafmeister, Christian; Feitelson, Mark (Temple University. Libraries, 2017)This work presents the application of spiroligomers as inhibitors of protein-protein interactions. After the discovery of an acyl-transfer coupling reaction by Dr. Zachary Brown, a previous graduate student of Schafmeister group, the synthesis of highly functionalized spiroligomers that mimic the helical domain of p53 was undertaken before each molecule was tested for binding to HDM2, a natural binding partner of p53. A library of molecules was synthesized on solid support that altered the stereochemistry along the spiroligomer as well as the presented functional groups. It was determined that spiroligomers enter human liver cancer cells through passive diffusion and induces a biological response in both a dose- and time-dependent manner. The synthesis of additional spiroligomer analogues achieved low micromolar to high nanomolar range activity during screening in direct and competitive binding assays. In parallel to the project above, a series of spiroligomers that mimic the side chains of the leucine zipper region of Max were synthesized in an effort to disrupt the interaction of the protein with c-Myc. The series of compounds contained various stereocenter combinations and different functional groups as before but were made in solution before testing for inhibition. Initial binding assays resulted in low micromolar activity, however, secondary assays (ELISA and cellular assays) did not confirm the inhibitory effect of spiroligomers on the c-Myc/Max heterodimer. In summary, this work illustrates that spiroligomers are capable mimics of helical peptides and can induce a biological response.
IDENTIFICATION OF PROTEIN PARTNERS FOR NIBP, A NOVEL NIK-AND IKKB-BINDING PROTEIN THROUGH EXPERIMENTAL, COMPUTATIONAL AND BIOINFORMATICS TECHNIQUESKiani, Mohammad F.; Hu, Wenhui; Dunbrack, Roland L.; Lelkes, Peter I. (Temple University. Libraries, 2013)NIBP is a prototype member of a novel protein family. It forms a novel subcomplex of NIK-NIBP-IKKB and enhances cytokine-induced IKKB-mediated NFKB activation. It is also named TRAPPC9 as a key member of trafficking particle protein (TRAPP) complex II, which is essential in trans-Golgi networking (TGN). The signaling pathways and molecular mechanisms for NIBP actions remain largely unknown. The aim of this research is to identify potential proteins interacting with NIBP, resulting in the regulation of NFKB signaling pathways and other unknown signaling pathways. At the laboratory of Dr. Wenhui Hu in the Department of Neuroscience, Temple University, sixteen partner proteins were experimentally identified that potentially bind to NIBP. NIBP is a novel protein with no entry in the Protein Data Bank. From a computational and bioinformatics standpoint, we use prediction of secondary structure and protein disorder as well as homology-based structural modeling approaches to create a hypothesis on protein-protein interaction between NIBP and the partner proteins. Structurally, NIBP contains three distinct regions. The first region, consisting of 200 amino acids, forms a hybrid helix and beta sheet-based domain possibly similar to Sybindin domain. The second region comprised of approximately 310 residues, forms a tetratrico peptide repeat (TPR) zone. The third region is a 675 residue long all beta sheet and loops zone with as many as 35 strands and only 2 helices, shared by Gryzun-domain containing proteins. It is likely to form two or three beta sheet sandwiches. The TPR regions of many proteins tend to bind to the peptides from disordered regions of other proteins. Many of the 16 potential binding proteins have high levels of disorder. These data suggest that the TPR region in NIBP most likely binds with many of these 16 proteins through peptides and other domains. It is also possible that the Sybindin-like domain and the Gryzun-like domain containing beta sheet sandwiches bind to some of these proteins.
MARKOV STATE MODELS AND THEIR APPLICATIONS IN PROTEIN FOLDING SIMULATION, SMALL MOLECULE DESIGN, AND MEMBRANE PROTEIN MODELINGVoelz, Vincent; Voelz, Vincent; Levy, Ronald M.; Schafmeister, Christian; Carnevale, Vincenzo; Fiorin, Giacomo (Temple University. Libraries, 2015)This dissertation is focused on the application of Markov State Models on protein folding and designing of small drug-like molecules, as well as application of computational tools on the study of biological processes. The central focus of protein folding is to understand how proteins obtain their unique three-dimensional structure from their aminoacid sequences. The function of protein critically depends on its three- dimensional structure; hence, any internal (such as mutations) or external (such as high temperature) perturbation that obstructs three-dimensional structure of a protein will also interfere with its function. Many diseases are associated with inability of protein to form its unique structure. For example, sickle cell anemia is caused by a single mutation that changes glutamic acid to valine. Molecular dynamics (MD) simulations could be utilized to study protein folding and effects of perturbations on protein energy landscape; however, due to its inherent atomic resolution, MD simulations usually provide enormous amount of data even for small proteins. A thorough analysis and extraction of desired information from MD provided data could be extremely challenging and is well beyond human comprehension. Markov state models (MSMs) are proved to be apt for the analysis of large scale random processes and equilibrium conditions, hence it could be applied for protein folding studies. MSMs can be used to obtain long timescale information from short timescale simulations. In other words, the combination of many short simulations and MSMs is a powerful technique to study the folding mechanism of many proteins, even the ones with folding times over millisecond. This dissertation is centered on the use of MSMs and MD simulation in understanding protein folding and biological processes and is constructed as the following. The first chapter provides a brief introduction into MD simulation and the different techniques that could be used to facilitate simulations. Protein folding and its challenges are also discussed in chapter one. Finally, chapter one ends with describing MSMs and technical aspects of building them for protein folding studies. Chapter two is focused on using MD simulations and MSMs to design small protein like molecules to prevent biofilm propagation by disrupting its lifecycle. The biofilm lifecycle and strategy for its interruption is described first. Then, the designed molecules and their conformational sampling by MD simulations are explained. Next, the application of MSMs in obtaining and comparing equilibrium population of all designs are discussed. At the end of chapter two, the molecular descriptions of best designs are explained. Chapter three is focused on the effects of mutations on the energy landscape of a sixteen residue protein from c-terminal hairpin of protein G, GB1. Three mutations, tz4, tz5, and tz6 are discussed, and their folding rates and folding mechanisms are compared with wild-type GB1 using MSMs built from a significantly large MD simulation data set (aggregating over 9 millisecond). Finally, chapter four is focused on the application of MD simulations on understanding the selectivity of Na,K-ATPase, a biologically critical protein that transports sodium ions outside and potassium ions inside against their concentration gradient in almost all eukaryotic cells. Multiple MD approaches, including metadynamics and free energy perturbation methods are used to describe the origins of selectivity for Na,K-ATPase.