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Kalina Hristova

Sijia Li, Sarah Y Kim, Anna E Pittman, Gavin M King, William C Wimley, Kalina Hristova
Potent macromolecule-sized poration of lipid bilayers by the macrolittins, a synthetically evolved family of pore-forming peptides. Sijia Li1, Sarah Y. Kim1, Anna E. Pittman3, Gavin M. King3,4, William C. Wimley2* and Kalina Hristova1* 1Materials Science and Engineering, Johns Hopkins University, Baltimore, MD 21218 2Biochemistry and Molecular Biology, Tulane University School of Medicine, New Orleans, LA 70112 3Physics and Astronomy, University of Missouri, Columbia, MO, 65201 4Biochemistry, University of Missouri, Columbia, MO, 65201 *Address correspondence to wwimley@tulane...
April 25, 2018: Journal of the American Chemical Society
Jóhannes Guðbrandsson, Sigríður Rut Franzdóttir, Bjarni Kristófer Kristjánsson, Ehsan Pashay Ahi, Valerie Helene Maier, Kalina Hristova Kapralova, Sigurður Sveinn Snorrason, Zophonías Oddur Jónsson, Arnar Pálsson
Phenotypic differences between closely related taxa or populations can arise through genetic variation or be environmentally induced, leading to altered transcription of genes during development. Comparative developmental studies of closely related species or variable populations within species can help to elucidate the molecular mechanisms related to evolutionary divergence and speciation. Studies of Arctic charr ( Salvelinus alpinus ) and related salmonids have revealed considerable phenotypic variation among populations and in Arctic charr many cases of extensive variation within lakes (resource polymorphism) have been recorded...
2018: PeerJ
Nuala Del Piccolo, Kalina Hristova
Adaptor proteins are a class of cytoplasmic proteins that bind to phosphorylated residues in receptor tyrosine kinases and trigger signaling cascades that control critically important cellular processes, such as cell survival, growth, differentiation, and motility. Here, we seek to characterize the interaction between epidermal growth factor receptor (EGFR) and the cytoplasmic adaptor protein growth factor receptor-bound protein 2 (Grb2) in a cellular context. To do so, we explore the utility of a highly biologically relevant model system, mammalian cells under reversible osmotic stress, and a recently introduced Förster resonance energy transfer microscopy method, fully quantified spectral imaging...
September 19, 2017: Biophysical Journal
Kalina Hristova
No abstract text is available yet for this article.
September 2017: Biochimica et Biophysica Acta
Deo R Singh, Fozia Ahmed, Sarvenaz Sarabipour, Kalina Hristova
Epithelial cadherin (Ecadherin) is responsible for the intercellular cohesion of epithelial tissues. It forms lateral clusters within adherens cell-cell junctions, but its association state outside these clusters is unknown. Here, we use a quantitative Forster resonance energy transfer (FRET) approach to show that Ecadherin forms constitutive dimers and that these dimers exist independently of the actin cytoskeleton or cytoplasmic proteins. The dimers are stabilized by intermolecular contacts that occur along the entire length of Ecadherin, with the intracellular domains having a surprisingly strong favorable contribution...
July 7, 2017: Journal of Molecular Biology
Jing He, Lilia I Melnik, Alexander Komin, Gregory Wiedman, Taylor Fuselier, Cameron F Morris, Charles G Starr, Peter C Searson, William R Gallaher, Kalina Hristova, Robert F Garry, William C Wimley
The Ebola virus (EBOV) genome encodes for a partly conserved, 40-residue, nonstructural polypeptide, called the delta peptide, which is produced in abundance during Ebola virus disease. The function of the delta peptide is unknown, but sequence analysis has suggested that delta peptide could be a viroporin, belonging to a diverse family of membrane-permeabilizing small polypeptides involved in replication and pathogenesis of numerous viruses. Full length and conserved C-terminal delta peptide fragments permeabilize the plasma membranes of nucleated cells of rodent, dog, monkey and human origin, increase ion permeability across confluent cell monolayers and permeabilize synthetic lipid bilayers...
May 24, 2017: Journal of Virology
Roxanne Glazier, Khalid Salaita
Mammalian and bacterial cells sense and exert mechanical forces through the process of mechanotransduction, which interconverts biochemical and physical signals. This is especially important in contact-dependent signaling, where ligand-receptor binding occurs at cell-cell or cell-ECM junctions. By virtue of occurring within these specialized junctions, receptors engaged in contact-dependent signaling undergo oligomerization and coupling with the cytoskeleton as part of their signaling mechanisms. While our ability to measure and map biochemical signaling within cell junctions has advanced over the past decades, physical cues remain difficult to map in space and time...
September 2017: Biochimica et Biophysica Acta
Inhee Chung
Receptor tyrosine kinases (RTK) are important cell surface receptors that transduce extracellular signals across the plasma membrane. The traditional view of how these receptors function is that ligand binding to the extracellular domains acts as a master-switch that enables receptor monomers to dimerize and subsequently trans-phosphorylate each other on their intracellular domains. However, a growing body of evidence suggests that receptor oligomerization is not merely a consequence of ligand binding, but is instead part of a complex process responsible for regulation of receptor activation...
September 2017: Biochimica et Biophysica Acta
Christopher King, Valerica Raicu, Kalina Hristova
FRET is an indispensable experimental tool for studying membrane proteins. Currently, two models are available for researchers to determine the oligomerization state of membrane proteins in a static quenching FRET experiment: the model of Veatch and Stryer, derived in 1977, and the kinetic theory-based model for intraoligomeric FRET, derived in 2007. Because of confinement in two dimensions, a substantial amount of FRET is generated by energy transfer between fluorophores located in separate oligomers in the two-dimensional bilayer...
March 31, 2017: Journal of Biological Chemistry
Eduard V Bocharov, Georgy V Sharonov, Olga V Bocharova, Konstantin V Pavlov
Among membrane receptors, the single-span receptor protein kinases occupy a broad but specific functional niche determined by distinctive features of the underlying transmembrane signaling mechanisms that are briefly overviewed on the basis of some of the most representative examples, followed by a more detailed discussion of several hierarchical levels of organization and interactions involved. All these levels, including single-molecule interactions (e.g., dimerization, liganding, chemical modifications), local processes (e...
September 2017: Biochimica et Biophysica Acta
David Holowka, Barbara Baird
The cell surface receptor for epidermal growth factor (EGFR), a receptor tyrosine kinase, is a key player in normal cell growth and proliferation. Mutations in this receptor often lead to oncological transformation and other pathologies. Because of its representation of the receptor tyrosine kinase family and its important role in health and disease, a broad range of studies have been carried out in many laboratories to investigate the structural basis for transmembrane receptor activation and the resulting assembly of cytosolic signaling components...
September 2017: Biochimica et Biophysica Acta
Gregory Wiedman, Sarah Y Kim, Elmer Zapata-Mercado, William C Wimley, Kalina Hristova
pH-triggered membrane-permeabilizing peptides could be exploited in a variety of applications, such as to enable cargo release from endosomes for cellular delivery, or as cancer therapeutics that selectively permeabilize the plasma membranes of malignant cells. Such peptides would be especially useful if they could enable the movement of macromolecules across membranes, a rare property in membrane-permeabilizing peptides. Here we approach this goal by using an orthogonal high-throughput screen of an iterative peptide library to identify peptide sequences that have the following two properties: (i) little synthetic lipid membrane permeabilization at physiological pH 7 at high peptide concentration and (ii) efficient formation of macromolecule-sized defects in synthetic lipid membranes at acidic pH 5 and low peptide concentration...
January 18, 2017: Journal of the American Chemical Society
Michael R Stoneman, Joel D Paprocki, Gabriel Biener, Koki Yokoi, Aishwarya Shevade, Sergei Kuchin, Valerică Raicu
Transmembrane proteins known as G protein-coupled receptors (GPCRs) have been shown to form functional homo- or hetero-oligomeric complexes, although agreement has been slow to emerge on whether homo-oligomerization plays functional roles. Here we introduce a platform to determine the identity and abundance of differing quaternary structures formed by GPCRs in living cells following changes in environmental conditions, such as changes in concentrations. The method capitalizes on the intrinsic capability of FRET spectrometry to extract oligomer geometrical information from distributions of FRET efficiencies (or FRET spectrograms) determined from pixel-level imaging of cells, combined with the ability of the statistical ensemble approaches to FRET to probe the proportion of different quaternary structures (such as dimers, rhombus or parallelogram shaped tetramers, etc...
September 2017: Biochimica et Biophysica Acta
Vikas K Parmar, Ellinor Grinde, Joseph E Mazurkiewicz, Katharine Herrick-Davis
Even though there are hundreds of reports in the published literature supporting the hypothesis that G protein-coupled receptors (GPCR) form and function as dimers this remains a highly controversial area of research and mechanisms governing homodimer formation are poorly understood. Crystal structures revealing homodimers have been reported for many different GPCR. For adrenergic receptors, a potential dimer interface involving transmembrane domain 1 (TMD1) and helix 8 (H8) was identified in crystal structures of the beta1-adrenergic (β1-AR) and β2-AR...
September 2017: Biochimica et Biophysica Acta
Nuala Del Piccolo, Sarvenaz Sarabipour, Kalina Hristova
The activity of receptor tyrosine kinases (RTKs) is controlled through their lateral association in the plasma membrane. RTKs are believed to form both homodimers and heterodimers, and the different dimers are believed to play unique roles in cell signaling. However, RTK heterodimers remain poorly characterized, as compared with homodimers, because of limitations in current experimental methods. Here, we develop a FRET-based methodology to assess the thermodynamics of hetero-interactions in the plasma membrane...
January 27, 2017: Journal of Biological Chemistry
Deo R Singh, Fozia Ahmed, Michael D Paul, Manasee Gedam, Elena B Pasquale, Kalina Hristova
All members of the Eph receptor family of tyrosine kinases contain a SAM domain near the C terminus, which has been proposed to play a role in receptor homotypic interactions and/or interactions with binding partners. The SAM domain of EphA2 is known to be important for receptor function, but its contribution to EphA2 lateral interactions in the plasma membrane has not been determined. Here we use a FRET-based approach to directly measure the effect of the SAM domain on the stability of EphA2 dimers on the cell surface in the absence of ligand binding...
January 2017: Biochimica et Biophysica Acta
Sarvenaz Sarabipour, Kalina Hristova
Missense mutations that introduce or remove cysteine residues in receptor tyrosine kinases are believed to cause pathologies by stabilizing the active receptor tyrosine kinase dimers. However, the magnitude of this stabilizing effect has not been measured for full-length receptors. Here, we characterize the dimer stabilities of three full-length fibroblast growth factor receptor (FGFR) mutants harboring pathogenic cysteine substitutions: the C178S FGFR1 mutant, the C342R FGFR2 mutant, and the C228R FGFR3 mutant...
October 9, 2016: Journal of Molecular Biology
Deo R Singh, Elena B Pasquale, Kalina Hristova
BACKGROUND: The EphA2 receptor tyrosine kinase is known to promote cancer cell malignancy in the absence of activation by ephrin ligands. This behavior depends on high EphA2 phosphorylation on Ser897 and low tyrosine phosphorylation, resulting in increased cell migration and invasiveness. We have previously shown that EphA2 forms dimers in the absence of ephrin ligand binding, and that dimerization of unliganded EphA2 can decrease EphA2 Ser897 phosphorylation. We have also identified a small peptide called YSA, which binds EphA2 and competes with the naturally occurring ephrin ligands...
September 2016: Biochimica et Biophysica Acta
Sarvenaz Sarabipour, Kurt Ballmer-Hofer, Kalina Hristova
VEGFR-2 is the primary regulator of angiogenesis, the development of new blood vessels from pre-existing ones. VEGFR-2 has been hypothesized to be monomeric in the absence of bound ligand, and to undergo dimerization and activation only upon ligand binding. Using quantitative FRET and biochemical analysis, we show that VEGFR-2 forms dimers also in the absence of ligand when expressed at physiological levels, and that these dimers are phosphorylated. Ligand binding leads to a change in the TM domain conformation, resulting in increased kinase domain phosphorylation...
April 7, 2016: ELife
Sarvenaz Sarabipour, Kalina Hristova
The G380R mutation in the transmembrane domain of FGFR3 is a germline mutation responsible for most cases of Achondroplasia, a common form of human dwarfism. Here we use quantitative Fӧster Resonance Energy Transfer (FRET) and osmotically derived plasma membrane vesicles to study the effect of the achondroplasia mutation on the early stages of FGFR3 signaling in response to the ligands fgf1 and fgf2. Using a methodology that allows us to capture structural changes on the cytoplasmic side of the membrane in response to ligand binding to the extracellular domain of FGFR3, we observe no measurable effects of the G380R mutation on FGFR3 ligand-bound dimer configurations...
July 2016: Biochimica et Biophysica Acta
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