Discovery of Selective Small-Molecule CD80 Inhibitors

Protein-protein interactions are widely found in biological systems controlling diverse cellular events. Because these interactions are implicated in many diseases such as autoimmunity and cancer, regulation of protein-protein interactions provides ideal targets for drug intervention. The CD80-CD28 costimulatory pathway plays a critical role in regulation of the immune response and thus constitutes an attractive target for therapeutic manipulation of autoimmune diseases. The objective of this study is to identify small compounds disrupting these pivotal protein-protein interactions. Compounds that specifically blocked binding of CD80 to CD28 were identified using a strategy involving a cell-based scintillation proximity assay as the initial step. Secondary screening (e.g., by analyzing the direct binding of these compounds to the target immobilized on a biosensor surface) revealed that these compounds are highly selective CD80 binders. Screening of structurally related derivatives led to the identification of the chemical features required for inhibition of the CD80-CD28 interaction. In addition, the optimization process led to a 10-fold increase in binding affinity of the CD80 inhibitors. Using this approach, the authors identify low-molecular-weight compounds that specifically and with high potency inhibit the interaction between CD80 and CD28. These compounds serve as promising starting points for further development of CD80 inhibitors as potential immunomodulatory drugs. ( Journal of Biomolecular Screening 2007:464-472)

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Mitochondria: Regulators of Cell Death and Survival

The Scientific World JOURNAL ◽

10.1100/tsw.2002.809 ◽

2002 ◽

Vol 2 ◽

pp. 1569-1578 ◽

Cited By ~ 34

Author(s):

David J. Granville ◽

Roberta A. Gottlieb

Keyword(s):

Cell Death ◽

Conformational Changes ◽

Protein Interactions ◽

Apoptotic Cell ◽

Critical Role ◽

Death Process ◽

Protein Protein Interactions ◽

Ionic Changes ◽

A Cell ◽

Cyt C

The past 5 years has seen an intense surge in research devoted toward understanding the critical role of mitochondria in the regulation of cell death. Apoptosis can be initiated by a wide array of stimuli, inducing multiple signaling pathways that, for the most part, converge at the mitochondrion. Although classically considered the powerhouses of the cell, it is now understood that mitochondria are also “gatekeepers” that ultimately determine the fate of the cell. The mitochondrial decision as to whether a cell lives or dies is complex, involving protein-protein interactions, ionic changes, reactive oxygen species, and other mechanisms that require further elucidation. Once the death process is initiated, mitochondria undergo conformational changes, resulting in the release of cytochrome c (cyt c), caspases, endonucleases, and other factors leading to the onset and execution of apoptosis. The present review attempts to outline the complex milieu of events regulating the mitochondrial commitment to and processes involved in the implementation of the executioner phase of apoptotic cell death.

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Exploring Proteomic Drug Targets, Therapeutic Strategies and Protein - Protein Interactions in Cancer: Mechanistic View

Current Cancer Drug Targets ◽

10.2174/1568009618666180803104631 ◽

2019 ◽

Vol 19 (6) ◽

pp. 430-448 ◽

Cited By ~ 1

Author(s):

Khalid Bashir Dar ◽

Aashiq Hussain Bhat ◽

Shajrul Amin ◽

Syed Anjum ◽

Bilal Ahmad Reshi ◽

...

Keyword(s):

Protein Interactions ◽

High Throughput Screening ◽

Critical Role ◽

Cancer Therapeutics ◽

Adaptor Proteins ◽

Therapeutic Strategies ◽

Small Gtpases ◽

Beta Catenin ◽

Protein Protein Interactions ◽

Apoptosis Protein

Protein-Protein Interactions (PPIs) drive major signalling cascades and play critical role in cell proliferation, apoptosis, angiogenesis and trafficking. Deregulated PPIs are implicated in multiple malignancies and represent the critical targets for treating cancer. Herein, we discuss the key protein-protein interacting domains implicated in cancer notably PDZ, SH2, SH3, LIM, PTB, SAM and PH. These domains are present in numerous enzymes/kinases, growth factors, transcription factors, adaptor proteins, receptors and scaffolding proteins and thus represent essential sites for targeting cancer. This review explores the candidature of various proteins involved in cellular trafficking (small GTPases, molecular motors, matrix-degrading enzymes, integrin), transcription (p53, cMyc), signalling (membrane receptor proteins), angiogenesis (VEGFs) and apoptosis (BCL-2family), which could possibly serve as targets for developing effective anti-cancer regimen. Interactions between Ras/Raf; X-linked inhibitor of apoptosis protein (XIAP)/second mitochondria-derived activator of caspases (Smac/DIABLO); Frizzled (FRZ)/Dishevelled (DVL) protein; beta-catenin/T Cell Factor (TCF) have also been studied as prospective anticancer targets. Efficacy of diverse molecules/ drugs targeting such PPIs although evaluated in various animal models/cell lines, there is an essential need for human-based clinical trials. Therapeutic strategies like the use of biologicals, high throughput screening (HTS) and fragment-based technology could play an imperative role in designing cancer therapeutics. Moreover, bioinformatic/computational strategies based on genome sequence, protein sequence/structure and domain data could serve as competent tools for predicting PPIs. Exploring hot spots in proteomic networks represents another approach for developing targetspecific therapeutics. Overall, this review lays emphasis on a productive amalgamation of proteomics, genomics, biochemistry, and molecular dynamics for successful treatment of cancer.

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Coiled-coil networking shapes cell molecular machinery

Molecular Biology of the Cell ◽

10.1091/mbc.e12-05-0396 ◽

2012 ◽

Vol 23 (19) ◽

pp. 3911-3922 ◽

Cited By ~ 44

Author(s):

Yongqiang Wang ◽

Xinlei Zhang ◽

Hong Zhang ◽

Yi Lu ◽

Haolong Huang ◽

...

Keyword(s):

Protein Interactions ◽

Critical Role ◽

Coiled Coil ◽

Coiled Coils ◽

Protein Protein Interactions ◽

Full Spectrum ◽

Kinetochore Assembly ◽

Genome Wide ◽

Molecular Machinery ◽

Systematic Understanding

The highly abundant α-helical coiled-coil motif not only mediates crucial protein–protein interactions in the cell but is also an attractive scaffold in synthetic biology and material science and a potential target for disease intervention. Therefore a systematic understanding of the coiled-coil interactions (CCIs) at the organismal level would help unravel the full spectrum of the biological function of this interaction motif and facilitate its application in therapeutics. We report the first identified genome-wide CCI network in Saccharomyces cerevisiae, which consists of 3495 pair-wise interactions among 598 predicted coiled-coil regions. Computational analysis revealed that the CCI network is specifically and functionally organized and extensively involved in the organization of cell machinery. We further show that CCIs play a critical role in the assembly of the kinetochore, and disruption of the CCI network leads to defects in kinetochore assembly and cell division. The CCI network identified in this study is a valuable resource for systematic characterization of coiled coils in the shaping and regulation of a host of cellular machineries and provides a basis for the utilization of coiled coils as domain-based probes for network perturbation and pharmacological applications.

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Proteomic Characterization of Protein-Protein Interactions

Austin Biology ◽

10.26420/austinbiol.2021.1027 ◽

2021 ◽

Vol 4 (1) ◽

Author(s):

Veenstra TD ◽

Keyword(s):

Protein Interactions ◽

Disease Diagnosis ◽

Cell System ◽

Protein Protein Interactions ◽

Novel Technologies ◽

Cell Functions ◽

Single Protein ◽

A Cell ◽

Molecular Components

Identifying all the molecular components within a living cell is the first step into understanding how it functions. To further understand how a cell functions requires identifying the interactions that occur between these components. This fact is especially relevant for proteins. No protein within a human cell functions on its own without interacting with another biomolecule - usually another protein. While Protein-Protein Interactions (PPI) have historically been determined by examining a single protein per study, novel technologies developed over the past couple of decades are enabling high-throughput methods that aim to describe entire protein networks within cells. In this review, some of the technologies that have led to these developments are described along with applications of these techniques. Ultimately the goal of these technologies is to map out the entire circuitry of PPI within human cells to be able to predict the global consequences of perturbations to the cell system. This predictive capability will have major impacts on the future of both disease diagnosis and treatment.

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A cell-penetrant lactam-stapled peptide for targeting eIF4E protein-protein interactions

European Journal of Medicinal Chemistry ◽

10.1016/j.ejmech.2020.112655 ◽

2020 ◽

Vol 205 ◽

pp. 112655

Author(s):

Erin E. Gallagher ◽

Arya Menon ◽

Alyah F. Chmiel ◽

Kirsten Deprey ◽

Joshua A. Kritzer ◽

...

Keyword(s):

Protein Interactions ◽

Protein Protein Interactions ◽

Stapled Peptide ◽

A Cell

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Dependence of KCC2 K-Cl cotransporter activity on a conserved carboxy terminus tyrosine residue

AJP Cell Physiology ◽

10.1152/ajpcell.2000.279.3.c860 ◽

2000 ◽

Vol 279 (3) ◽

pp. C860-C867 ◽

Cited By ~ 73

Author(s):

Kevin Strange ◽

Thomas D. Singer ◽

Rebecca Morrison ◽

Eric Delpire

Keyword(s):

Protein Interactions ◽

Regulatory Protein ◽

Phosphorylation Site ◽

Fold Increase ◽

Tyrosine Residue ◽

Carboxy Terminus ◽

Protein Protein Interactions ◽

Pharmacological Studies ◽

Osmotic Homeostasis ◽

Tyrosine Phosphorylation Site

K-Cl cotransporters (KCC) play fundamental roles in ionic and osmotic homeostasis. To date, four mammalian KCC genes have been identified. KCC2 is expressed exclusively in neurons. Injection of Xenopus oocytes with KCC2 cRNA induced a 20-fold increase in Cl−-dependent, furosemide-sensitive K+ uptake. Oocyte swelling increased KCC2 activity 2–3 fold. A canonical tyrosine phosphorylation site is located in the carboxy termini of KCC2 (R1081–Y1087) and KCC4, but not in other KCC isoforms. Pharmacological studies, however, revealed no regulatory role for phosphorylation of KCC2 tyrosine residues. Replacement of Y1087 with aspartate or arginine dramatically reduced K+ uptake under isotonic and hypotonic conditions. Normal or near-normal cotransporter activity was observed when Y1087 was mutated to phenylalanine, alanine, or isoleucine. A tyrosine residue equivalent to Y1087 is conserved in all identified KCCs from nematodes to humans. Mutation of the Y1087 congener in KCC1 to aspartate also dramatically inhibited cotransporter activity. Taken together, these results suggest that replacement of Y1087 and its congeners with charged residues disrupts the conformational state of the carboxy terminus. We postulate that the carboxy terminus plays an essential role in maintaining the functional conformation of KCC cotransporters and/or is involved in essential regulatory protein-protein interactions.

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Proteomic analysis of palmitoylated platelet proteins

Blood ◽

10.1182/blood-2011-05-353078 ◽

2011 ◽

Vol 118 (13) ◽

pp. e62-e73 ◽

Cited By ~ 77

Author(s):

Louisa Dowal ◽

Wei Yang ◽

Michael R. Freeman ◽

Hanno Steen ◽

Robert Flaumenhaft

Keyword(s):

Protein Interactions ◽

Protein Identification ◽

Global Analysis ◽

Critical Role ◽

Myeloid Cell ◽

Metabolic Labeling ◽

Protein Protein Interactions ◽

Proteomic Approach ◽

Protein Palmitoylation ◽

Liquid Chromatography Tandem Mass

Abstract Protein palmitoylation is a dynamic process that regulates membrane targeting of proteins and protein-protein interactions. We have previously demonstrated a critical role for protein palmitoylation in platelet activation and have identified palmitoylation machinery in platelets. Using a novel proteomic approach, Palmitoyl Protein Identification and Site Characterization, we have begun to characterize the human platelet palmitoylome. Palmitoylated proteins were enriched from membranes isolated from resting platelets using acyl-biotinyl exchange chemistry, followed by identification using liquid chromatography-tandem mass spectrometry. This global analysis identified > 1300 proteins, of which 215 met criteria for significance and represent the platelet palmitoylome. This collection includes 51 known palmitoylated proteins, 61 putative palmitoylated proteins identified in other palmitoylation-specific proteomic studies, and 103 new putative palmitoylated proteins. Of these candidates, we chose to validate the palmitoylation of triggering receptors expressed on myeloid cell (TREM)–like transcript-1 (TLT-1) as its expression is restricted to platelets and megakaryocytes. We determined that TLT-1 is a palmitoylated protein using metabolic labeling with [3H]palmitate and identified the site of TLT-1 palmitoylation as cysteine 196. The discovery of new platelet palmitoyl protein candidates will provide a resource for subsequent investigations to validate the palmitoylation of these proteins and to determine the role palmitoylation plays in their function.

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A proline-rich sequence unique to MEK1 and MEK2 is required for raf binding and regulates MEK function.

Molecular and Cellular Biology ◽

10.1128/mcb.15.10.5214 ◽

1995 ◽

Vol 15 (10) ◽

pp. 5214-5225 ◽

Cited By ~ 137

Author(s):

A D Catling ◽

H J Schaeffer ◽

C W Reuter ◽

G R Reddy ◽

M J Weber

Keyword(s):

Protein Interactions ◽

Critical Role ◽

Phosphorylation Site ◽

Specific Protein ◽

Protein Protein Interactions ◽

Serum Stimulation ◽

And Function

Mammalian MEK1 and MEK2 contain a proline-rich (PR) sequence that is absent both from the yeast homologs Ste7 and Byr1 and from a recently cloned activator of the JNK/stress-activated protein kinases, SEK1/MKK4. Since this PR sequence occurs in MEKs that are regulated by Raf family enzymes but is missing from MEKs and SEKs activated independently of Raf, we sought to investigate the role of this sequence in MEK1 and MEK2 regulation and function. Deletion of the PR sequence from MEK1 blocked the ability of MEK1 to associate with members of the Raf family and markedly attenuated activation of the protein in vivo following growth factor stimulation. In addition, this sequence was necessary for efficient activation of MEK1 in vitro by B-Raf but dispensable for activation by a novel MEK1 activator which we have previously detected in fractionated fibroblast extracts. Furthermore, we found that a phosphorylation site within the PR sequence of MEK1 was required for sustained MEK1 activity in response to serum stimulation of quiescent fibroblasts. Consistent with this observation, we observed that MEK2, which lacks a phosphorylation site at the corresponding position, was activated only transiently following serum stimulation. Finally, we found that deletion of the PR sequence from a constitutively activated MEK1 mutant rendered the protein nontransforming in Rat1 fibroblasts. These observations indicate a critical role for the PR sequence in directing specific protein-protein interactions important for the activation, inactivation, and downstream functioning of the MEKs.

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Protein–protein interactions in intracellular Ca2+-release channel function

Biochemical Journal ◽

10.1042/bj3370345 ◽

1999 ◽

Vol 337 (3) ◽

pp. 345-361 ◽

Cited By ~ 8

Author(s):

John J. MACKRILL

Keyword(s):

Protein Interactions ◽

Ryanodine Receptors ◽

Accessory Proteins ◽

Protein Protein Interactions ◽

Release Channel ◽

Specific Effects ◽

Complex Protein ◽

A Cell ◽

And Function ◽

Opposing Effects

Release of Ca2+ ions from intracellular stores can occur via two classes of Ca2+-release channel (CRC) protein, the inositol 1,4,5-trisphosphate receptors (InsP3Rs) and the ryanodine receptors (RyRs). Multiple isoforms and subtypes of each CRC class display distinct but overlapping distributions within mammalian tissues. InsP3Rs and RyRs interact with a plethora of accessory proteins which modulate the activity of their intrinsic channels. Although many aspects of CRC structure and function have been reviewed in recent years, the properties of proteins with which they interact has not been comprehensively surveyed, despite extensive current research on the roles of these modulators. The aim of this article is to review the regulation of CRC activity by accessory proteins and, wherever possible, to outline the structural details of such interactions. The CRCs are large transmembrane proteins, with the bulk of their structure located cytoplasmically. Intra- and inter-complex protein–protein interactions between these cytoplasmic domains also regulate CRC function. Some accessory proteins modulate channel activity of all CRC subtypes characterized, whereas other have class- or even isoform-specific effects. Certain accessory proteins exert both direct and indirect forms of regulation on CRCs, occasionally with opposing effects. Others are themselves modulated by changes in Ca2+ concentration, thereby participating in feedback mechanisms acting on InsP3R and RyR activity. CRCs are therefore capable of integrating numerous signalling events within a cell by virtue of such protein–protein interactions. Consequently, the functional properties of InsP3Rs and RyRs within particular cells and subcellular domains are ‘customized ’ by the accessory proteins present.

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Determining rewiring effects of alternatively spliced isoforms on protein-protein interactions using a computational approach

10.1101/256834 ◽

2018 ◽

Author(s):

Oleksandr Narykov ◽

Nathan Johnson ◽

Dmitry Korkin

Keyword(s):

Protein Interactions ◽

Molecular Mechanisms ◽

Critical Role ◽

Computational Approach ◽

Superior Performance ◽

Large Set ◽

Protein Protein Interactions ◽

Specific Expression ◽

Alternatively Spliced ◽

Specific Regulation

AbstractThe critical role of alternative splicing (AS) in cell functioning has recently become apparent, whether in studying tissue-or cell-specific regulation, or understanding molecular mechanisms governing a complex disorder. Studying the rewiring, or edgetic, effects of alternatively spliced isoforms on protein interactome can provide system-wide insights into these questions. Unfortunately, high-throughput experiments for such studies are expensive and time-consuming, hence the need to develop an in-silico approach. Here, we formulated the problem of characterization the edgetic effects of AS on protein-protein interactions (PPIs) as a binary classification problem and introduced a first computational approach to solve it. We first developed a supervised feature-based classifier that benefited from the traditional features describing a PPI, the problem-specific features that characterized the difference between the reference and alternative isoforms, and a novel domain interaction potential that allowed pinpointing the domains employed during a specific PPI. We then expanded this approach by including a large set of unlabeled interactomics data and developing a semi-supervised learning method. Our method called AS-IN (Alternatively Splicing INteraction prediction) Tool was compared with the state-of-the-art PPI prediction tools and showed a superior performance, achieving 0.92 in precision and recall. We demonstrated the utility of AS-IN Tool by applying it to the transcriptomic data obtained from the brain and liver tissues of a healthy mouse and western diet fed mouse that developed type two diabetes. We showed that the edgetic effects of differentially expressed transcripts associated with the disease condition are system-wide and unlikely to be detected by looking only at the gene-specific expression levels.

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