Janessa Gerhart

Related Articles

Disrupting the transmembrane domain-mediated oligomerization of protein tyrosine phosphatase receptor J inhibits EGFR-driven cancer cell phenotypes.

J Biol Chem. 2019 12 06;294(49):18796-18806

Authors: Bloch E, Sikorski EL, Pontoriero D, Day EK, Berger BW, Lazzara MJ, Thévenin D

Abstract
Receptor protein tyrosine phosphatases (RPTPs) play critical regulatory roles in mammalian signal transduction. However, the structural basis for the regulation of their catalytic activity is not fully understood, and RPTPs are generally not therapeutically targetable. This knowledge gap is partially due to the lack of known natural ligands or selective agonists of RPTPs. Contrary to what is known from structure-function studies of receptor tyrosine kinases (RTKs), RPTP activities have been reported to be suppressed by dimerization, which may prevent RPTPs from accessing their RTK substrates. We report here that homodimerization of protein tyrosine phosphatase receptor J (PTPRJ, also known as DEP-1) is regulated by specific transmembrane (TM) residues. We found that disrupting these interactions destabilizes homodimerization of full-length PTPRJ in cells, reduces the phosphorylation of the known PTPRJ substrate epidermal growth factor receptor (EGFR) and of other downstream signaling effectors, antagonizes EGFR-driven cell phenotypes, and promotes substrate access. We demonstrate these observations in human cancer cells using mutational studies and identified a peptide that binds to the PTPRJ TM domain and represents the first example of an allosteric agonist of RPTPs. The results of our study provide fundamental structural and functional insights into how PTPRJ activity is tuned by TM interactions in cells. Our findings also open up opportunities for developing peptide-based agents that could be used as tools to probe RPTPs' signaling mechanisms or to manage cancers driven by RTK signaling.

PMID: 31676686 [PubMed - indexed for MEDLINE]

Formyl-peptide receptor activation enhances phagocytosis of community-acquired methicillin-resistant Staphylococcus aureus.

J Infect Dis. 2019 Oct 01;:

Authors: Weiß E, Schlatterer K, Beck C, Peschel A, Kretschmer D

Abstract
Formyl-peptide receptors (FPRs) are important pattern recognition receptors that sense specific bacterial peptides. FPRs are highly expressed on neutrophils and monocytes, and their activation promotes the migration of phagocytes to sites of infection. It is currently unknown, if FPRs may also influence subsequent processes such as bacterial phagocytosis and killing. Staphylococcus aureus, especially highly pathogenic community-acquired methicillin-resistant S. aureus (MRSA) strains, release high amounts of FPR2 ligands, the phenol-soluble modulins (PSMs). We demonstrate that FPR activation leads to upregulation of complement receptors 1 and 3 as well as FCγ receptor I on neutrophils and, consequently, increased opsonic phagocytosis of S. aureus and other pathogens. Increased phagocytosis promotes killing of S. aureus and IL-8 release by neutrophils. We show here for the first time that FPRs govern opsonic phagocytosis. Manipulation of FPR2 activation could open new therapeutic opportunities against bacterial pathogens.

PMID: 31573600 [PubMed - as supplied by publisher]

Small-molecule-based regulation of RNA-delivered circuits in mammalian cells

Small-molecule-based regulation of RNA-delivered circuits in mammalian cells, Published online: 16 October 2018; doi:10.1038/s41589-018-0146-9

Engineering of small-molecule-responsive RNA-binding proteins enables chemical regulation of modified mRNA or RNA replicon expression within mammalian cells for applications in synthetic circuit design and RNA-centered therapeutics.

Metabolic repair through emergence of new pathways in Escherichia coli

Metabolic repair through emergence of new pathways in <i>Escherichia coli</i>, Published online: 16 October 2018; doi:10.1038/s41589-018-0149-6

In response to the deletion of key genes involved in biosynthesis of the essential CoA precursor β-alanine, Escherichia coli overcomes this pathway damage by successively evolving alternative metabolic pathways.

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Direct protein-lipid interactions shape the conformational landscape of secondary transporters.

Nat Commun. 2018 10 08;9(1):4151

Authors: Martens C, Shekhar M, Borysik AJ, Lau AM, Reading E, Tajkhorshid E, Booth PJ, Politis A

Abstract
Secondary transporters undergo structural rearrangements to catalyze substrate translocation across the cell membrane - yet how such conformational changes happen within a lipid environment remains poorly understood. Here, we combine hydrogen-deuterium exchange mass spectrometry (HDX-MS) with molecular dynamics (MD) simulations to understand how lipids regulate the conformational dynamics of secondary transporters at the molecular level. Using the homologous transporters XylE, LacY and GlpT from Escherichia coli as model systems, we discover that conserved networks of charged residues act as molecular switches that drive the conformational transition between different states. We reveal that these molecular switches are regulated by interactions with surrounding phospholipids and show that phosphatidylethanolamine interferes with the formation of the conserved networks and favors an inward-facing state. Overall, this work provides insights into the importance of lipids in shaping the conformational landscape of an important class of transporters.

PMID: 30297844 [PubMed - indexed for MEDLINE]

CRISPR mutagenesis screening of mice

CRISPR mutagenesis screening of mice, Published online: 08 October 2018; doi:10.1038/s41556-018-0224-y

Functional genetic screening of mice and other mammals is exceedingly challenging. A CRISPR-based mutagenesis screen in mice has successfully revealed amino acids vital for protein function of the DND1 gene, missense mutations of which lead to defects in primordial germ cell development.

This Perspective discusses the concept of immune normalization and how its underlying principles may help to augment, as well as design, cancer immunotherapies.

Therapeutic antibody-based cancer treatment leads to ADCP-induced, AIM2-mediated immunosuppression by macrophages that can be overcome with concomitant immune checkpoint blockade.

A DNA nanoplatform‐based co‐delivery system containing two linear shRNA transcription templates against tumor‐associated genes (Pgp and survive) and a chemotherapeutic drug (doxorubicin, DOX) was constructed for synergistic therapy of multidrug resistant (MDR) tumors in vivo.

Abstract

Multidrug resistance (MDR) is a major obstacle in the clinical treatment of cancer. Herein, a facile strategy is reported to construct a versatile DNA nanostructure as a co‐delivery vector of RNA interference (RNAi) and chemodrugs to combat multidrug‐resistant tumor (MCF‐7R) in vitro and in vivo. In the tailored nanocarrier, two linear small hairpin RNA (shRNA) transcription templates targeting MDR‐associated genes (gene of P‐glycoprotein, a typical drug efflux pump; and gene of survivin, a representative anti‐apoptotic protein) are precisely organized in the chemodrug (doxorubicin, DOX) pre‐loaded DNA origami. With the incorporation of active targeting and controlled‐release elements, these multifunctional DNA nanocarriers can successfully enter the target MCF‐7R cells and synergistically inhibit tumor growth without apparent systemic toxicity. This tailored DNA nanoplatform, which combines RNAi therapy and chemotherapy, provides a new strategy for the treatment of multidrug‐resistant tumors.

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Activity of a novel antimicrobial peptide against Pseudomonas aeruginosa biofilms.

Sci Rep. 2018 10 03;8(1):14728

Authors: Beaudoin T, Stone TA, Glibowicka M, Adams C, Yau Y, Ahmadi S, Bear CE, Grasemann H, Waters V, Deber CM

Abstract
With the increasing recognition of biofilms in human disease, the development of novel antimicrobial therapies is of critical importance. For example, in patients with cystic fibrosis (CF), the acquisition of host-adapted, chronic Pseudomonas aeruginosa infection is associated with a decline in lung function and increased mortality. Our objective was to test the in vitro efficacy of a membrane-active antimicrobial peptide we designed, termed 6K-F17 (sequence: KKKKKK-AAFAAWAAFAA-NH2), against multidrug resistant P. aeruginosa biofilms. This peptide displays high antimicrobial activity against a range of pathogenic bacteria, yet is non-hemolytic to human erythrocytes and non-toxic to human bronchial epithelial cells. In the present work, P. aeruginosa strain PAO1, and four multidrug resistant (MDR) isolates from chronically infected CF individuals, were grown as 48-hour biofilms in a static biofilm slide chamber model. These biofilms were then exposed to varying concentrations of 6K-F17 alone, or in the presence of tobramycin, prior to confocal imaging. Biofilm biovolume and viability were assessed. 6K-F17 was able to kill biofilms - even in the presence of sputum - and greatly reduce biofilm biovolume in PAO1 and MDR isolates. Strikingly, when used in conjunction with tobramycin, low doses of 6K-F17 significantly potentiated tobramycin killing, leading to biofilm destruction.

PMID: 30283025 [PubMed - indexed for MEDLINE]

Detecting antibodies in blood is as simple as it can get. In their Communication on https://doi.org/10.1002/anie.201808070page 15369 ff., D. Citterio, M. Merkx et al. integrate antibody‐targeting bioluminescent sensing proteins and other essential assay components into a microfluidic paper‐based analytical device. A drop of blood, a digital camera, and twenty minutes are all that is required to detect the presence and the concentration of multiple antibodies in whole blood based on the color of the emitted light.

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Chemical synthesis of transmembrane peptide and its application for research on the transmembrane-juxtamembrane region of membrane protein.

Biopolymers. 2016 Nov 04;106(4):613-21

Authors: Sato T

Abstract
Membrane proteins possess one or more hydrophobic regions that span the membrane and interact with the lipids that constitute the membrane. The interactions between the transmembrane (TM) region and lipids affect the structure and function of these membrane proteins. Molecular characterization of synthetic TM peptides in lipid bilayers helps to understand how the TM region participates in the formation of the structure and in the function of membrane proteins. The use of synthetic peptides enables site-specific labeling and modification and allows for designing of an artificial TM sequence. Research involving such samples has resulted in significant increase in the knowledge of the mechanisms that govern membrane biology. In this review, the chemical synthesis of TM peptides has been discussed. The preparation of synthetic TM peptides is still not trivial; however, the accumulated knowledge summarized here should provide a basis for preparing samples for spectroscopic analyses. The application of synthetic TM peptides for gaining insights into the mechanism of signal transduction by receptor tyrosine kinase (RTK) has also been discussed. RTK is a single TM protein and is one of the difficult targets in structural biology as crystallization of the full-length receptor has not been successful. This review describes the structural characterization of the synthetic TM-juxtamembrane sequence and proposes a possible scheme for the structural changes in this region for the activation of ErbBs, the epidermal growth factor receptor family. © 2015 Wiley Periodicals, Inc. Biopolymers (Pept Sci) 106: 613-621, 2016.

PMID: 26573237 [PubMed - indexed for MEDLINE]

Abstract

Real-time imaging of translation activities on individual mRNAs in live cells enables the detection of transient translational responses to environmental stresses, motion dynamics of individual polysomes at different subcellular compartments, and local translation and active transport of polysomes in the dendrites of neurons.

A diagnostic platform utilizing biomolecular sensors and CRISPR-based technology allows rapid, specific, and low-cost detection of the Zika virus at clinically relevant concentrations.

Abstract