Interactions between anti-ErbB2 antibody A21 and the ErbB2 extracellular domain provide a basis for improving A21 affinity

Anti-ErbB2 antibodies are well researched for the therapy of ErbB2-overexpressing tumors. The therapeutic potential and efficacy of these antibodies are closely related to their affinities to ErbB2. Previously we reported that an anti-ErbB2 antibody A21 targeting a conformational epitope comprising several loops in ErbB2 extracellular subdomain I and II could inhibit the proliferation of ErbB2-overexpressing cancer cells in vitro and in vivo. Here we found that another structureless and non-conserved loop in subdomain I of ErbB2 extracellular domain (ECD) was important for binding to A21, and then the antigen-contact sites on A21 were determined by site-directed mutation. The loop was constructed by molecular modeling, and a new model of A21-ErbB2 complex was generated by docking using the crystal structure of the scfv A21 and the model of ErbB2 ECD with the loop built. Based on the complex model, computational design for A21 affinity improvement was performed to enhance its affinity to ErbB2. Two mutants with about 1.7-fold improvement in affinity were obtained. Our study provided a rational molecular basis for affinity improvement and mechanism investigation of A21.     

Conformational transition and energy landscape of ErbB4 activated by neuregulin1β: one microsecond molecular dynamics simulations

ErbB4, a receptor tyrosine kinase of the ErbB family, plays crucial roles in cell growth and differentiation, especially in the development of the heart and nervous system. Ligand binding to its extracellular region could modulate the activation process. To understand the mechanism of ErbB4 activation induced by ligand binding, we performed one microsecond molecular dynamics (MD) simulations on the ErbB4 extracellular region (ECR) with and without its endogenous ligand neuregulin1β (NRG1β). The conformational transition of the ECR-ErbB4/NRG1β complex from a tethered inactive conformation to an extended active-like form has been observed, while such large and function-related conformational change has not been seen in the simulation on the ECR-ErbB4, suggesting that ligand binding is indeed the active inducing force for the conformational transition and further dimerization. On the basis of MD simulations and principal component analysis, we constructed a rough energy landscape for the conformational transition of ECR-ErbB4/NRG1β complex, suggesting that the conformational change from the inactive state to active-like state involves a stable conformation. The energy barrier for the tether opening was estimated as ~2.7 kcal/mol, which is very close to the experimental value (1-2 kcal/mol) reported for ErbB1. On the basis of the simulation results, an atomic mechanism for the ligand-induced activation of ErbB4 was postulated. The present MD simulations provide a new insight into the conformational changes underlying the activation of ErbB4.     

Molecular insight into the T798M gatekeeper mutation-caused acquired resistance to tyrosine kinase inhibitors in ErbB2-positive breast cancer

Human epidermal growth factor receptor 2 (ErbB2) is an attractive therapeutic target for metastatic breast cancer. The kinase has been clinically observed to harbor a gatekeeper mutation T798M in its active site, which causes acquired resistance to the first-line targeted breast cancer therapy with small-molecule tyrosine kinase inhibitors. Previously, several theories have been proposed to explain the molecular mechanism of gatekeeper mutation-caused drug resistance, such as blocking of inhibitor binding and increasing of ATP affinity. In the current study, the direct binding of three wild type-selective inhibitors (Lapatinib, AEE788 and TAK-285) and two wild type-sparing inhibitors (Staurosporine and Bosutinib) to the wild-type ErbB2 and its T798M mutant are investigated in detail by using rigorous computational analysis and binding affinity assay. Substitution of the polar threonine with a bulky methionine at residue 798 can impair and improve the direct binding affinity of wild type-selective and wild type-sparing inhibitors, respectively. Hindrance effect is responsible for the affinity decrease of wild type-selective inhibitors, while additional nonbonded interactions contribute to the affinity increase of wild type-sparing inhibitors, thus conferring selectivity to the inhibitors for mutant over wild type. The binding affinity of Staurosporine and Bosutinib to ErbB2 kinase domain is improved by 11.9-fold and 2.1-fold upon T798M mutation, respectively. Structural analysis reveals that a nonbonded network of S–π contact interactions (for Staurosporine) or an S-involving halogen bond (for Bosutinib) forms with the sulfide group of mutant Met798 residue.     

Inhibitors of tyrosine kinase proteins induced Ras signaling pathway as potential anti-tumor agents

Cellular signaling pathways induced by growth-factor receptors with tyrosine kinase activity are frequently deregulated in cancer. Anti-tumor agents that inhibit their enzymatic tyrosine kinase activity have been designed and are now used in human chemotherapy. We review here our data constituting an alternative way to interrupt over-expressed signaling pathway by inhibiting protein-protein interactions. In our approach, the adaptor protein Grb2 over-expressed in connection with HER2/ErbB2/neu in Ras signaling pathway was chosen as a target. Peptides and peptidomimetics with very high affinities for either SH3 or SH2 domains of Grb2 were rationally designed from structural data. We describe their synthesis, their capacity to interrupt the signaling pathway and their anti-proliferative activity. To cite this article: M. Vidal et al., C. R. Chimie 8 (2005).     

Hole burning spectroscopy of ribonuclease A

We present pressure tuning hole burning experiments with the enzyme ribonuclease A using the UV-absorbing amino acid tyrosine as a probe. We show that, at 2 K, the protein is intact, and that at least four different regions which we associate with different tyrosine sites can be distinguished through their specific response to pressure. For one site we could determine the compressibility to 0.15 GPa(-1). Upon denaturing the protein with guanidine hydrochloride, one of the tyrosine sites is preserved to a large extent. Reducing the sulfur bonds has a more drastic effect: the tyrosine sites lose most of their individual features and their compressibilities come close to that of tyrosine in solution.     

Surface plasmon resonance immunosensor for ErbB2 breast cancer biomarker determination in human serum and raw cancer cell lysates

A highly sensitive surface plasmon resonance (SPR) immunosensor for the important ErbB2 breast cancer biomarker has been developed. Optimization of the assay has been carried out, including signal enhancement employing gold nanoparticles (GNPs). The effect of the signal amplification of the GNPs has been also studied. The assay has been tested with clinically relevant matrices. Results in 50% human serum yielded a LOD of 180 pg mL⁻¹ which is a concentration 83 times lower than the clinical cut-off. Raw lysates from model breast cancer cell lines (SK-BR-3, MCF-7 and MDA-MB-436) have been also assayed and higher quantities of the ErbB2 protein were clearly observed in the ErbB2 over-expressing case (SK-BR-3). The results confirmed that the simple and highly sensitive SPR immunosensor represents a feasible tool for ErbB2 detection.     

Interactome of ErbB4 unveiled

MacBeath and colleagues (Kaushansky et al., 2008) use a protein array technology to find binding partners of ErbB4 in a genome-wide and quantitative fashion, shedding new light on how ErbB4 initiates cellular signaling events and why ErbB4 is not a potent oncogene.     

Excited‐State Proton Transfer Can Tune the Color of Protein Fluorescent Markers

We show by quantum mechanical/molecular mechanical (QM/MM) simulations that phenylbenzothiazoles undergoing an excited‐state proton transfer (ESPT) can be used to probe protein binding sites. For 2‐(2′‐hydroxy‐4′‐aminophenyl)benzothiazole (HABT) bound to a tyrosine kinase, the absolute and relative intensities of the fluorescence bands arising from the enol and keto forms are found to be strongly dependent on the active‐site conformation. The emission properties are tuned by hydrogen‐bonding interactions of HABT with the neighboring amino acid T766 and with active‐site water. The use of ESPT tuners opens the possibility of creating two‐color fluorescent markers for protein binding sites, with potential applications in the detection of mutations in cancer cell lines.     

PSGL-1——一种介导白细胞粘附的重要分子

PSGL-1是90年代初期发现的一种粘附分子，具有同源二聚体的结构，为一种跨膜的糖蛋白，表达于白细胞的表面，成熟PSGL-1分子上具有很多O-连接的糖基化位点，岩藻糖基化，唾液酸化和NH2末端酪氨酸的硫酸化对于PSGL-1的功能十分重要，PSGL-1是选择素P的配体，与选择素P具有特殊的亲和性，PSGL-1同时也是选择素L和选择素E的配体，PSGL-1与选择素分子的相互作用在白细胞粘附的起始阶段发挥着重要作用，PSGL-1在介导白细胞粘附的同时可以转导胞外信号，促进白细胞活化并使其稳定粘附，白细胞粘附具有重要的生理意义。     

A dendritic cell-like biomimetic nanoparticle enhances T cell activation for breast cancer immunotherapy

Cancer immunotherapy has remarkably improved the therapeutic effect of melanoma and non-small cell lung cancer in the clinic. Nevertheless, it showed disappointing clinical outcomes for treating immunosuppressive tumors, wherein aggressive T cells are rather limited in tumor sites. Therefore, regulating the behavior of T cells in tumor sites to increase their attack ability for suppressing the immunosuppressive tumor is highly desirable. Inspiringly, we designed a dendritic cell-like biomimetic nanoparticle (DMSNs³@HA) to regulate the behavior of T cells for improving the immunotherapy effect against immunosuppressive tumors. In this work, anti-CD3 and anti-CD28 were responsible for mimicking dendritic cells to activate T cells, and anti-PD-1 for blocking the pathway of PD-1/PD-L1 to break the immune “brake”, which synergistically regulated the behavior of T cells to attack cancer cells. Experimental results indicated that DMSNs³@HA can effectively activate T cells and improve their immune response to significantly inhibit the growth of breast cancer. Moreover, it also proved that T cell activation combining immune checkpoint blocking induced the “1 + 1 >2” immunotherapy effect against immunosuppressive tumors. We expect that this strategy will provide new insights into tumor immunotherapy by modulating T cell behavior.

A dendritic cell-like biomimetic nanoparticle has been designed to regulate the behavior of T cells for improving the immunotherapy effect against immunosuppressive tumors.     

Genetically encoding protein oxidative damage

Posttranslational modification of tyrosine residues in proteins, to produce 3-nitrotyrosine (3-NT), is associated with over 50 disease states including transplant rejection, lung infection, central nervous system and ocular inflammation shock, cancer, and neurological disorders (for example, Alzheimer's disease, Parkinson's disease, and stroke). The levels of 3-NT increase in aging tissue, and levels of 3-NT in proteins are a predictor of disease risk. Here we report the evolution and characterization of an aminoacyl-tRNA synthetase/tRNA pair for the cotranslational, site-specific incorporation of 3-NT into proteins at genetically encoded sites. To demonstrate the utility of our approach for studying the effect on protein function of nitration on sites defined in vivo, we prepared manganese superoxide dismutase (MnSOD) that is homogeneously nitrated at a site known to be modified in disease-related inflammatory responses, and we measured the effect of this defined modification on protein function.     

Rapid Tyrosine Phosphorylation of HS1 in the Response of Mouse Lymphoma L5178Y-R Cells to Photodynamic Treatment Sensitized by the Phthalocyanine Pc 4

Abstract— The ability of photodynamic treatment (PDT) with the phthalocyanine Pc 4 to activate cellular signal transduction pathways in murine lymphoma L5178Y-R cells has been assessed by observing increases in protein tyrosine phosphorylation at early times post-PDT. Western blot analysis with an anti-phosphotyrosine antibody revealed a dramatic increase in phosphorylation of two major protein bands of Mr -80000 and -55000 in response to PDT. The increase was PDT dose-dependent, occurred as early as 20 s after initiation of light exposure of Pc 4-pre-loaded cells and was amplified by the presence of the protein tyrosine phosphatase inhibitor, sodium ortho-vanadate (NaV0₄). By immunoprecipitation, one of the Mr –80000 phosphorylated proteins has been identified as HS1, a substrate of nonreceptor-type protein tyrosine kinases. Although vanadate greatly enhanced the level and extent of PDT-induced phosphorylation, it had no influence on overall photocytotoxicity or on the rate of apoptotic DNA fragmentation. Genistein, an inhibitor of protein tyrosine kinases, diminished tyrosine phosphorylation of the Mr –80000 and other proteins and dramatically potentiated cell killing induced by PDT but did not significantly affect PDT-induced apoptosis. The results suggest that PDT rapidly activates a membrane-associated src family kinase(s) in L5178Y-R cells, one substrate of which is HS1, and that protein tyrosine phosphorylation is part of a stress response, protecting a portion of the cells from the lethal effects of PDT but not altering the mechanism by which they die.     

Diastereomer-specific effects of double-stranded peptides conjugated with -L-Tyr-L-Phe- or -L-Tyr-D-Phe- residues on tyrosine phosphorylation and inhibition of src(ts)NRK, A431, MCF-7, and DU145 cell growth

The interaction between growth inhibition and chirality, especially of diastereomers, has an important modifying effect on cancer cell proliferation. Previously, we have reported on the design, synthesis, and chemical properties of a series of novel, double-stranded peptides, (y-AA-x-AA)(2)-(CH(2))(12), with -y-AA-x-AA- and -z-AA-y-AA-x-AA- sequences conjugated to the spacer. Here, we extend those results by showing that (D-, L-) and (L-, D-) diastereomers are more potent inhibitors of tyrosine phosphorylation than (L-, L-). Although the replacement of the L-Phe-L-Phe sequence with L-Tyr-L-Phe produces a less active inhibitor, the double-stranded peptide conjugated with L-Tyr-D-Phe is more active than that conjugated with L-Tyr-L-Phe. In addition, we show that SDS-PAGE gel profiles of tyrosine phosphorylation following treatment with bis(y-Tyr-x-Phe)-N,N-dodecane-1,12-diamine appear very similar to profiles of tyrosine phosphorylation following treatment with an analog of the tyrosine kinase inhibitor, erbstatin. Moreover, the level of autophosphorylation of the epidermal growth factor receptor kinase domain (EGFRKD) treated with bis(L-Tyr-D-Phe)-N,N-dodecane-1,12-diamine was lower than that seen following treatment with bis(L-Phe-D-Phe)-N,N-dodecane-1,12-diamine. These data provide new insights for the control of cancer cell proliferation through drug designs which replace the less active -L-Phe-L-Phe- (and -D-Phe-L-Phe-) with the more active -L-Tyr-L-Phe- (and -L-Tyr-D-Phe-) sequence.     

Studies of ligand-induced site-specific phosphorylation of epidermal growth factor receptor

The epidermal growth factor receptor (EGFR) is a receptor tyrosine kinase involved in the regulation of growth in many animal cells, including cancer cells. Phosphorylation of specific tyrosine residues within the cytoplasmic domain of EGFR is part of the initial activation process that occurs upon ligand binding, and these phosphotyrosine residues subsequently serve as docking sites for intracellular signaling molecules. To study the phosphorylation on each individual site, EGFR generated from a human epidermoid carcinoma cell line (A431) was analyzed by mass spectrometry. Liquid chromatography combined with tandem mass spectrometry (LC/MS/MS) was used to identify the tryptic phosphopeptides and their sites of phosphorylation (Y992, Y1045, Y1068, Y1086, S1142, Y1148, and Y1173). Ion intensities for the phosphorylated and unphosphorylated tryptic peptides containing the sites of phosphorylation were measured, and the intensity ratios were used to assess the degree of phosphorylation at each site. Ligand concentrations were varied for epidermal growth factor (EGF) and transforming growth factor alpha (TGF alpha) as stimuli, and all of the EGFR tyrosine sites were consequently found to exhibit increased levels of phosphorylation, although at different rates and to different extents. Phosphorylation of Y992 appeared to plateau at lower concentrations of ligand, whereas the other sites continued to have increased phosphorylation throughout a wide range of concentrations. Only small differences could be detected between the EGF and the TGF alpha-induced EGFR phosphorylation. Pretreatment of A431 cells with a small molecule EGFR inhibitor nearly eliminated the ligand-induced phosphorylation on all of the sites except for Y992 and Y1068.     

甲烷氧化偶联W-Mn/SiO2催化剂上O2-脉冲频率效应(PFE)的研究

采用频率脉冲反应方法,以Mn-Na2WO4/S iO2催化剂上甲烷氧化偶联为探针反应,通过实时、原位的四极质谱检测手段,研究氧物种对甲烷C-H键选择性活化的微观历程.首次发现了Mn-Na2WO4/S iO2催化剂上O2-脉冲频率效应,即脉冲反应产物量随氧脉冲注入频率的增加而增加.研究结果表明,在反应条件下,Mn-Na2WO4/S iO2催化剂上有两种活化甲烷的氧物种同时存在,它们活化甲烷的方式不同。     

[~3H] TYROSINE BINDING TO PLASMA MEMBRANE PREPARATION OF RAT CORPORA LUTEA

Plasma membrane preparations of rat corpora lutea have been incubated with [~3H]tyrosine. [~3H]-tyrosine binding sites are demonstrated and Scatchard analysis shows that there exist two types of binding sites, one with high affinity and low capacity, the other with low affinity and high capacity. The kinetics studies demonstrate that the [~3H]tyrosine binding to the two types of binding sites is reversible and the speed of binding to the high affinity type is faster than that to the low affinity type. The analysis of the chemical structure of tyrosine analogues and related compounds with respect to the specificity of the binding sites reveal that both types of binding sites show specificity, but the specificity of the high affinity sites is higher than that of the low affinity sites. The relations of tyrosine structure to binding processing and to tyrosine inhibitory action on hCG-induced progesterone production are discussed. It is suggested that the high affinity binding sites might be regarded as "ty     

甲烷氧化偶联W-Mn／SiO2催化剂上02-脉冲频率效应（PFE）的研究

采用频率脉冲反应方法，以Mn-Na2WO4／SiO2催化剂上甲烷氧化偶联为探针反应，通过实时、原位的四极质谱检测手段，研究氧物种对甲烷C-H键选择性活化的微观历程．首次发现了Mn-Na2 WO4／SiO2催化剂上O2-脉冲频率效应，即脉冲反应产物量随氧脉冲注入频率的增加而增加．研究结果表明。在反应条件下，Mn-Na2 WO4／SiO2催化剂上有两种活化甲烷的氧物种同时存在，它们活化甲烷的方式不同。     

Mass spectrometry analysis of in vitro nitration of a recombinant human IgG1 monoclonal antibody

Nitration of a recombinant human monoclonal antibody was carried out in vitro by incubating the antibody with the nitrating reagent tetranitromethane (TNM). The susceptible sites of nitration were identified using high-performance liquid chromatography/mass spectrometry (HPLC/MS). In general, tyrosine residues in the variable domains of the antibody are more susceptible to nitration, while tyrosine residues in the constant domains are relatively resistant to nitration. However, one tyrosine residue in the CH1 domain and one tyrosine residue in the CH2 domain are highly susceptible to nitration. Interestingly, the susceptible tyrosine residue in the CH2 domain is followed by the conserved asparagine residue that is glycosylated.