Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04626 (erbB-2)
 5,251 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Previously, a panel of mouse monoclonal antibodies (mAbs) to several tumor-associated antigens was chemically crosslinked to an IgG1 anti-human transferrin receptor antibody, 454A12. We called this new class of bispecific antibodies (BmAbs) "antigen forks" and showed that these antigen forks inhibited but did not completely prevent tumor cell growth. We speculated that the conjugates acted by heterologously crosslinking two antigens in a manner that interfered with the functions of one or both. The most effective BmAbs all shared one specificity for the human transferrin receptor. A monoclonal antibody to this receptor has been shown by others to reduce tumor cell growth when used with the iron chelator deferoxamine. When we combined our antigen forks with deferoxamine, two of five BmAbs synergized with deferoxamine to arrest tumor cell count at or below input levels. The most effective BmAbs were 317G5/454A12 (3/4) and 520C9/454A12 (5/4). mAb 317G5 recognizes a 42-kDa tumor-associated glycoprotein, and mAb 520C9 recognizes the c-erbB-2 protooncogene product. BmAb 3/4 was most effective against colorectal cancer cell line HT-29, and BmAb 5/4 was most effective against breast cancer cell line SK-BR-3. When deferoxamine and BmAb were replaced by fresh medium after a 6- or 7-day treatment period, no regrowth of tumor cells was observed during the next 4 days, although regrowth was seen if either deferoxamine or BmAb was used alone. Our results show that BmAbs with specificities for transferrin receptor and certain tumor-associated antigens effectively inhibit tumor growth in vitro. When used in combination with deferoxamine, such BmAbs may have therapeutic potential for the treatment of cancer.
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PMID:In vitro tumor growth inhibition by bispecific antibodies to human transferrin receptor and tumor-associated antigens is augmented by the iron chelator deferoxamine. 876 64

Pseudomonas exotoxin (PE) requires proteolytic cleavage to generate a 37-kDa C-terminal fragment that translocates to the cytosol and ADP-ribosylates elongation factor 2. Cleavage within cells is mediated by furin, occurs between arginine 279 and glycine 280, and requires an arginine at both P1 and P4 residues. To study the proteolytic processing of PE-derived chimeric toxins, TGFalpha-PE38 (transforming growth factor fused to the domains II and III of PE) and a mutant form, TGFalpha-PE38gly279, were each produced in Escherichia coli. When assessed on various epidermal growth factor (EGF) receptor-positive cell lines, TGFalpha-PE38 was 100-500-fold more toxic than TGFalpha-PE38gly279. In contrast to PE, where cleavage by furin is only evident at pH 5.5, furin cleaved TGFalpha-PE38 over a broad pH range, while TGFalpha-PE38gly279 was resistant to cleavage. TGFalpha-PE38 was poorly toxic for furin-deficient LoVo cells, unless it was first pretreated in vitro with furin. Furin treatment produced a nicked protein that was 30-fold more toxic than its unnicked counterpart. Using the single chain immunotoxin HB21scFv-PE40 as a substrate, furin-mediated processing of an antibody-based immunotoxin was also evaluated. HB21scFv-PE40, which targets cells expressing the transferrin receptor, was cleaved in a similar fashion to that of TGFalpha-PE38 and nicked HB21scFv-PE40 exhibited increased toxicity for LoVo cells. In short-term experiments, the rate of reduction in protein synthesis by furin-nicked immunotoxins was increased compared with unnicked protein, indicating that cleavage by furin can be a rate-limiting step. We conclude that furin-mediated cleavage of PE-derived immunotoxins is important for their cytotoxic activity.
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PMID:Furin-mediated cleavage of Pseudomonas exotoxin-derived chimeric toxins. 939 13

An increasing number of independent studies indicate that the atypical protein kinase C (PKC) isoforms (aPKCs) are critically involved in the control of cell proliferation and survival. The aPKCs are targets of important lipid mediators such as ceramide and the products of the PI 3-kinase. In addition, the aPKCs have been shown to interact with Ras and with two novel proteins, LIP (lambda-interacting protein; a selective activator of lambda/iotaPKC) and the product of par-4 (a gene induced during apoptosis), which is an inhibitor of both lambda/iotaPKC and zetaPKC. LIP and Par-4 interact with the zinc finger domain of the aPKCs where the lipid mediators have been shown to bind. Here we report the identification of p62, a previously described phosphotyrosine-independent p56(lck) SH2-interacting protein, as a molecule that interacts potently with the V1 domain of lambda/iotaPKC and, albeit with lower affinity, with zetaPKC. We also show in this study that ectopically expressed p62 colocalizes perfectly with both lambda/iotaPKC and zetaPKC. Interestingly, the endogenous p62, like the ectopically expressed protein, displays a punctate vesicular pattern and clearly colocalizes with endogenous lambda/iotaPKC and endogenous zetaPKC. P62 colocalizes with Rab7 and partially with lamp-1 and limp-II as well as with the epidermal growth factor (EGF) receptor in activated cells, but not with Rab5 or the transferrin receptor. Of functional relevance, expression of dominant negative lambda/iotaPKC, but not of the wild-type enzyme, severely impairs the endocytic membrane transport of the EGF receptor with no effect on the transferrin receptor. These findings strongly suggest that the aPKCs are anchored by p62 in the lysosome-targeted endosomal compartment, which seems critical for the control of the growth factor receptor trafficking. This is particularly relevant in light of the role played by the aPKCs in mitogenic cell signaling events.
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PMID:Localization of atypical protein kinase C isoforms into lysosome-targeted endosomes through interaction with p62. 956 25

Although interactions between the mu2 subunit of the clathrin adaptor protein complex AP-2 and tyrosine-based internalization motifs have been implicated in the selective recruitment of cargo molecules into coated pits, the functional significance of this interaction for endocytosis of many types of membrane proteins remains unclear. To analyze the function of mu2-receptor interactions, we constructed an epitope-tagged mu2 that incorporates into AP-2 and is targeted to coated pits. Mutational analysis revealed that Asp176 and Trp421 of mu2 are involved in the interaction with internalization motifs of TGN38 and epidermal growth factor (EGF) receptor. Inducible overexpression of mutant mu2, in which these two residues were changed to alanines, resulted in metabolic replacement of endogenous mu2 in AP-2 complexes and complete abrogation of AP-2 interaction with the tyrosine-based internalization motifs. As a consequence, endocytosis of the transferrin receptor was severely impaired. In contrast, internalization of the EGF receptor was not affected. These results demonstrate the potential usefulness of the dominant-interfering approach for functional analysis of the adaptor protein family, and indicate that clathrin-mediated endocytosis may proceed in both a mu2-dependent and -independent manner.
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PMID:Inhibition of the receptor-binding function of clathrin adaptor protein AP-2 by dominant-negative mutant mu2 subunit and its effects on endocytosis. 1022 63

Advances in molecular and cell biology have led to further understanding of the mechanisms of malignant growth and metastasis in human breast cancer cells. Initiation and progression of breast cancer results from mutations and the abnormal expression of many genes that control cellular proliferation, differentiation, invasion, metastasis and sensitivity to therapy (chemotherapy and radiation therapy). Inhibition of host immunity also plays a role in breast cancer progression. Many genes have been selected as targets for antisense therapy, including HER-2/neu, PKA, TGF-alpha, EGFR, TGF-beta, IGFIR, P12, MDM2, BRCA, Bcl-2, ER, VEGF, MDR, ferritin, transferrin receptor, IRE, C-fos, HSP27, C-myc, C-raf and metallothionein genes. The strategy behind antisense therapy is the development of specific therapeutic agents that aim to correct the mutations and abnormal expression of cellular genes in breast tumour cells by decreasing gene expression, inducing degradation of target mRNA and causing premature termination of transcription. Many in vitro and in vivo studies have investigated the therapeutic efficacy of oligonucleotides and antisense RNAs. These studies have demonstrated specific inhibition of tumour cell growth by antisense therapy and have shown synergistic inhibitory effects between antisense oligonucleotides or antisense RNA and conventional chemotherapeutic drugs used in the treatment of breast cancer. Antisense oligonucleotides have been modified to improve their ability to penetrate cells, bind to gene sequences and downregulate target gene function. Many delivery systems for antisense RNA and antisense oligonucleotides have been developed, including virus vectors (retrovirus, adenovirus and adeno-associate virus) and liposomes, to carry the antisense RNA or oligonucleotides through the cell membrane into the cytoplasm and nucleus of the tumour cells. However, in order to determine their feasibility antisense therapies need to be further investigated to determine their antitumour activity, pharmacokinetics and toxicity in breast cancer patients.
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PMID:Gene targets of antisense therapies in breast cancer. 1222 74

Breast cancer is one kind of multi-gene related malignancy. Overexpression of some oncogenes such as HER-2 (c-erbB-2, Neu), bcl-2/bcl-xL, protein kinase A (PKA), and transferrin receptor gene (TfR gene), etc significantly affect the prognosis of breast cancer. It was shown that specific suppression of the overexpressed genes above resulted in the improvement of the therapy of breast cancer. Antisense interference, one of useful tools for inhibiting the overexpression of specific oncogenes, was involved in the therapy of breast cancer in recent years. Data indicated that antisense oligonucleotides (ON) could inhibit specially the expression of the target genes on mRNA or protein levels in most of cases; some ON candidates showed encouraging therapeutic effects in vitro and in vivo on breast cancer cell lines or xenografts. Furthermore, the combination use of the antisense ON and normal chemotherapeutic agents indicated synergistic antitumor effects, which was probably the best utilization of antisense ON in the treatment of breast cancer.
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PMID:Advancements of antisense oligonucleotides in treatment of breast cancer. 1267 65

In contrast to the epidermal growth factor (EGF) receptor, ErbB2 is known to remain at the plasma membrane after ligand binding and dimerization. However, why ErbB2 is not efficiently down-regulated has remained elusive. Basically, two possibilities exist: ErbB2 is internalization resistant or it is efficiently recycled after internalization. By a combination of confocal microscopy, immunogold labeling electron microscopy, and biochemical techniques we show that ErbB2 is preferentially associated with membrane protrusions. Moreover, it is efficiently excluded from clathrin-coated pits and is not seen in transferrin receptor-containing endosomes. This pattern is not changed after binding of EGF, heregulin, or herceptin. The exclusion from coated pits is so pronounced that it cannot just be explained by lack of an internalization signal. Although ErbB2 is a raft-associated protein, the localization of ErbB2 to protrusions is not a result of raft binding. Also, an intact actin cytoskeleton is not required for keeping ErbB2 away from coated pits. However, after efficient cross-linking, ErbB2 is removed from protrusions to occur on the bulk membrane, in coated pits, and in endosomes. These data show that ErbB2 is a remarkably internalization-resistant receptor and suggest that the mechanism underlying the firm association of ErbB2 with protrusions also is the reason for this resistance.
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PMID:Association with membrane protrusions makes ErbB2 an internalization-resistant receptor. 1474 16

Membrane microdomains, the so-called lipid rafts, function as platforms to concentrate receptors and assemble the signal transduction machinery. Internalization, in most cases, is carried out by different specialized structures, the clathrin-coated pits. Here, we show that several endocytic proteins are efficiently recruited to morphologically identified plasma membrane lipid rafts, upon activation of the epidermal growth factor (EGF) receptor (EGFR), a receptor tyrosine kinase. Analysis of detergent-resistant membrane fractions revealed that the EGF-dependent association of endocytic proteins with rafts is as efficient as that of signaling effector molecules, such as Grb2 or Shc. Finally, the EGFR, but not the nonsignaling transferrin receptor, could be localized in nascent coated pits that almost invariably contained raft membranes. Thus, specialized membrane microdomains have the ability to assemble both the molecular machineries necessary for intracellular propagation of EGFR effector signals and for receptor internalization.
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PMID:Relationships between EGFR signaling-competent and endocytosis-competent membrane microdomains. 1577 53

We describe a novel syntaxin family member, syntaxin 9 (Syn 9), which does not possess a typical C-terminal hydrophobic tail anchor. Syn 9 has, however, a Q-SNARE domain and an overall homology to syntaxins (with the highest overall homology with mammalian syntaxin 11). Syn 9 is enriched in some epithelial cells, particularly that of the stomach lining and the skin. At the skin, it is found in the epidermal layers as well as structures associated with hair follicles. A biochemical interaction screen revealed that Syn 9 interacts specifically with the epidermal growth factor (EGF) receptor. Overexpression of Syn 9 perturbed EGF receptor endocytosis but does not appear to affect the internalization of the transferrin receptor. Syn 9 may therefore have a role in EGF receptor transport and signaling in certain epithelial cell types.
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PMID:Syntaxin 9 is enriched in skin hair follicle epithelium and interacts with the epidermal growth factor receptor. 1642 May 29

The early endosome is organised into domains to ensure the separation of cargo. Activated mitogenic receptors, such as epidermal growth factor (EGF) receptor, are concentrated into vacuoles enriched for the small GTPase Rab5, which progressively exclude nutrient receptors, such as transferrin receptor, into neighbouring tubules. These vacuoles become enlarged, increase their content of intralumenal vesicles as EGF receptor is sorted from the limiting membrane, and eventually mature to late endosomes. Maturation is governed by the loss of Rab5 and is accompanied by the movement of endosomes along microtubules towards the cell centre. Here, we show that EGF relocates to the cell centre in a dynein-dependent fashion, concomitant with the sorting away of transferrin receptor, although it remains in Rab5-positive early endosomes. When dynein function is acutely disrupted, efficient recycling of transferrin from EGF-containing endosomes is retarded, loss of Rab5 is slowed and endosome enlargement is reduced.
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PMID:Dynein is required for receptor sorting and the morphogenesis of early endosomes. 1717 37


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