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Tashiro D, Suetaka S, Sato N, Ooka K, Kunihara T, Kudo H, Inatomi J, Hayashi Y, Arai M. Intron-Encoded Domain of Herstatin, An Autoinhibitor of Human Epidermal Growth Factor Receptors, Is Intrinsically Disordered. Front Mol Biosci 2022; 9:862910. [PMID: 35573740 PMCID: PMC9100580 DOI: 10.3389/fmolb.2022.862910] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Accepted: 03/31/2022] [Indexed: 11/17/2022] Open
Abstract
Human epidermal growth factor receptors (HER/ERBB) form dimers that promote cell proliferation, migration, and differentiation, but overexpression of HER proteins results in cancer. Consequently, inhibitors of HER dimerization may function as effective antitumor drugs. An alternatively spliced variant of HER2, called herstatin, is an autoinhibitor of HER proteins, and the intron 8-encoded 79-residue domain of herstatin, called Int8, binds HER family receptors even in isolation. However, the structure of Int8 remains poorly understood. Here, we revealed by circular dichroism, NMR, small-angle X-ray scattering, and structure prediction that isolated Int8 is largely disordered but has a residual helical structure. The radius of gyration of Int8 was almost the same as that of fully unfolded states, although the conformational ensemble of Int8 was less flexible than random coils. These results demonstrate that Int8 is intrinsically disordered. Thus, Int8 is an interesting example of an intrinsically disordered region with tumor-suppressive activity encoded by an intron. Furthermore, we show that the R371I mutant of Int8, which is defective in binding to HER2, is prone to aggregation, providing a rationale for the loss of function.
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Affiliation(s)
- Daisuke Tashiro
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Shunji Suetaka
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Nao Sato
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Koji Ooka
- Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo, Japan
| | - Tomoko Kunihara
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Hisashi Kudo
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Junichi Inatomi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Yuuki Hayashi
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
| | - Munehito Arai
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan
- Department of Physics, Graduate School of Science, The University of Tokyo, Tokyo, Japan
- *Correspondence: Munehito Arai,
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HER2-PI9 and HER2-I12: two novel and functionally active splice variants of the oncogene HER2 in breast cancer. J Cancer Res Clin Oncol 2021; 147:2893-2912. [PMID: 34136934 PMCID: PMC8397700 DOI: 10.1007/s00432-021-03689-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2021] [Accepted: 06/05/2021] [Indexed: 11/03/2022]
Abstract
In this study, two novel alternative splice variants of HER2, named HER2-PI9 and HER2-I12, were identified in breast cancer cell lines and breast tumour tissues. Whilst HER2-P19 arises from the inclusion of an 117 bp cassette-exon of intron 9 of HER2, HER2-I12 results from intron 12 inclusion. In silico analyses were performed to predict the amino acid sequences of these two HER2 novel variants. To confirm their protein expression, plasmid vectors were generated and transfected into the HER2 negative breast cancer cell line, MCF-7. Additionally, their functional properties in oncogenic signalling were confirmed. Expression of HER2-PI9 and HER2-I12 was successful and matched the in silico predictions. Importantly, these splice variants can modulate the phosphorylation levels of extracellular signal-related kinase 1/2 (ERK1/2) and Akt/protein kinase B (Akt) signalling in MCF-7 breast cancer cells. Enhanced cellular proliferation, migration and invasion were observed in the case of the HER2-I12 expressing model. In human tissues and breast carcinoma tumours both variants were present. This study reveals two novel splice variants of HER2. Additionally, the potential biological activity for HER2-PI9 and HER2-I12 in breast cancer cells is also reported..
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Hart V, Gautrey H, Kirby J, Tyson-Capper A. HER2 splice variants in breast cancer: investigating their impact on diagnosis and treatment outcomes. Oncotarget 2020; 11:4338-4357. [PMID: 33245725 PMCID: PMC7679030 DOI: 10.18632/oncotarget.27789] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2020] [Accepted: 10/10/2020] [Indexed: 02/07/2023] Open
Abstract
Overexpression of the HER2 receptor occurs in approximately 20% of breast cancer patients. HER2 positivity is associated with poor prognosis and aggressive tumour phenotypes, which led to rapid progress in HER2 targeted therapeutics and diagnostic testing. Whilst these advances have greatly increased patients' chances of survival, resistance to HER2 targeted therapies, be that intrinsic or acquired, remains a problem. Different forms of the HER2 protein exist within tumours in tandem and can display altered biological activities. Interest in HER2 variants in breast cancer increased when links between resistance to anti-HER2 therapies and a particular variant, Δ16-HER2, were identified. Moreover, the P100 variant potentially reduces the efficacy of the anti-HER2 therapy trastuzumab. Another variant, Herstatin, exhibits 'auto-inhibitory' behaviour. More recently, new HER2 variants have been identified and are currently being assessed for their pro- and anti-cancer properties. It is important when directing the care of patients to consider HER2 variants collectively. This review considers HER2 variants in the context of the tumour environment where multiple variants are co-expressed at altered ratios. This study also provides an up to date account of the landscape of HER2 variants and links this to patterns of resistance against HER2 therapies and treatment plans.
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Affiliation(s)
- Vic Hart
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Hannah Gautrey
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - John Kirby
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
| | - Alison Tyson-Capper
- Translational and Clinical Research Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, UK
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Splicing regulatory factors in breast cancer hallmarks and disease progression. Oncotarget 2019; 10:6021-6037. [PMID: 31666932 PMCID: PMC6800274 DOI: 10.18632/oncotarget.27215] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2019] [Accepted: 08/29/2019] [Indexed: 12/31/2022] Open
Abstract
By regulating transcript isoform expression levels, alternative splicing provides an additional layer of protein control. Recent studies show evidence that cancer cells use different splicing events to fulfill their requirements in order to develop, progress and metastasize. However, there has been less attention for the role of the complex catalyzing the complicated multistep splicing reaction: the spliceosome. The spliceosome consists of multiple sub-complexes in total comprising 244 proteins or splice factors and 5 associated RNA molecules. Here we discuss the role of splice factors in the oncogenic processes tumors cells need to fulfill their oncogenic properties (the so-called the hallmarks of cancer). Despite the fact that splice factors have been investigated only recently, they seem to play a prominent role in already five hallmarks of cancer: angiogenesis, resisting cell death, sustaining proliferation, deregulating cellular energetics and invasion and metastasis formation by affecting major signaling pathways such as epithelial-to-mesenchymal transition, the Warburg effect, DNA damage response and hormone receptor dependent proliferation. Moreover, we could relate expression of representative genes of four other hallmarks (enabling replicative mortality, genomic instability, avoiding immune destruction and evading growth suppression) to splice factor levels in human breast cancer tumors, suggesting that also these hallmarks could be regulated by splice factors. Since many splice factors are involved in multiple hallmarks of cancer, inhibiting splice factors might provide a new layer of oncogenic control and a powerful method to combat breast cancer progression.
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Silipo M, Gautrey H, Satam S, Lennard T, Tyson-Capper A. How is Herstatin, a tumor suppressor splice variant of the oncogene HER2, regulated? RNA Biol 2016; 14:536-543. [PMID: 27935425 DOI: 10.1080/15476286.2016.1267074] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
The human epidermal growth factor receptor 2 (HER2)/receptor tyrosine-protein kinasebB-2 (ERBB2) is overexpressed in 20-30% of breast tumors leading to faster growing and more aggressive tumors. Alternative splicing generates a functionally distinct HER2 variant called Herstatin, which is produced by the inclusion of intron 8. Herstatin acts as a tumor suppressor by effectively blocking HER2 activity and cell proliferation, while promoting apoptosis. In the present study we investigated HER2 pre-mRNA regulatory sequences and splicing factors which regulate the alternative splicing of Herstatin. A Herstatin minigene, comprising exon 8/intron 8/exon 9 of HER2 was generated and subsequent in vitro splicing assays revealed that RNA secondary structure and somatic mutations did not impact on inclusion of intron 8. However, using RNase-assisted RNA chromatography, followed by mass spectrometry, we identified six RNA-binding proteins (splicing factors) that bind to RNA sequences surrounding exon 8/intron 8 and intron 8/exon 9 boundaries; these included hnRNP I, H1, D, A2/B1 and hnRNPA1 plus the SR protein SRSF1. Specifically, overexpression of hnRNP A1 significantly increased retention of intron 8 resulting in higher levels of Herstatin in SKBR3 breast cancer cells whereas SRSF1 only had a marginal effect in decreasing Herstatin but increased exogenous HER2 levels under these experimental conditions. In conclusion, we have identified the first splicing factors and regulatory sequences that are involved in the production of Herstatin.
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Affiliation(s)
- Marco Silipo
- a Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University , Newcastle , UK
| | - Hannah Gautrey
- a Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University , Newcastle , UK
| | - Swapna Satam
- a Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University , Newcastle , UK
| | - Thomas Lennard
- b Northern Institute for Cancer Research, Faculty of Medical Sciences, Newcastle University , Newcastle , UK
| | - Alison Tyson-Capper
- a Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University , Newcastle , UK
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Dittrich A, Gautrey H, Browell D, Tyson-Capper A. The HER2 Signaling Network in Breast Cancer--Like a Spider in its Web. J Mammary Gland Biol Neoplasia 2014; 19:253-70. [PMID: 25544707 DOI: 10.1007/s10911-014-9329-5] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/18/2014] [Accepted: 12/14/2014] [Indexed: 12/21/2022] Open
Abstract
The human epidermal growth factor receptor 2 (HER2) is a major player in the survival and proliferation of tumour cells and is overexpressed in up to 30 % of breast cancer cases. A considerable amount of work has been undertaken to unravel the activity and function of HER2 to try and develop effective therapies that impede its action in HER2 positive breast tumours. Research has focused on exploring the HER2 activated phosphoinositide-3-kinase (PI3K)/AKT and rat sarcoma/mitogen-activated protein kinase (RAS/MAPK) pathways for therapies. Despite the advances, cases of drug resistance and recurrence of disease still remain a challenge to overcome. An important aspect for drug resistance is the complexity of the HER2 signaling network. This includes the crosstalk between HER2 and hormone receptors; its function as a transcription factor; the regulation of HER2 by protein-tyrosine phosphatases and a complex network of positive and negative feedback-loops. This review summarises the current knowledge of many different HER2 interactions to illustrate the complexity of the HER2 network from the transcription of HER2 to the effect of its downstream targets. Exploring the novel avenues of the HER2 signaling could yield a better understanding of treatment resistance and give rise to developing new and more effective therapies.
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Affiliation(s)
- A Dittrich
- Institute of Cellular Medicine, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, NE2 4HH, UK
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7
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Conformational flexibility of the ErbB2 ectodomain and trastuzumab antibody complex as revealed by molecular dynamics and principal component analysis. J Mol Model 2012; 19:1227-36. [DOI: 10.1007/s00894-012-1661-3] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2012] [Accepted: 10/22/2012] [Indexed: 01/22/2023]
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Lv M, Qiao C, Jiang N, Li X, Yu M, Hou C, Li Y, Feng J, Shen B. The peptide derived from erbB2 auto-inhibitor herstatin shared in the same epitope and function with functional antibody 2C4. Mol Biotechnol 2011; 51:174-82. [PMID: 22139885 DOI: 10.1007/s12033-011-9454-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
Abstract
Previous studies have shown that different epitopes of HER2 exhibit distinct functions and that the epitope bound by the antibody 2C4 plays a role in formation of hetereodimers between HER2 and other receptors of the HER family. In this study, we used computer modeling to determine that the epitope of HER2 which the C-terminal 79 amino acids of herstatin (named HSTC79) binds is similar to that bound by 2C4. Based on these theoretical results, recombinant HSTC79 fused with GST was expressed in Escherichia coli and purified by affinity chromatography. Experimental analysis showed that HSTC79 did specifically bind to HER2 and that the epitope of HER2 identified by HSTC79 was near that identified by 2C4. Furthermore, HSTC79 inhibited the growth of HER2-overexpressing cells. These results highlight the fact that the binding site architecture and certain key residues of HER2 may be very helpful for understanding the protein's biological role and providing insights for designing novel inhibitors of HER2.
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Affiliation(s)
- Ming Lv
- Institute of Basic Medical Sciences, Beijing 100850, People's Republic of China
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9
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Gao F, Hu XY, Xie XJ, Xu QY, Wang YP, Liu XB, Xiang MX, Sun Y, Wang JA. Heat shock protein 90 protects rat mesenchymal stem cells against hypoxia and serum deprivation-induced apoptosis via the PI3K/Akt and ERK1/2 pathways. J Zhejiang Univ Sci B 2010; 11:608-17. [PMID: 20669351 DOI: 10.1631/jzus.b1001007] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Mesenchymal stem cell (MSC) transplantation has shown a therapeutic potential to repair the ischemic and infracted myocardium, but the effects are limited by the apoptosis and loss of donor cells in host cardiac microenvironment. The aim of this study is to explore the cytoprotection of heat shock protein 90 (Hsp90) against hypoxia and serum deprivation-induced apoptosis and the possible mechanisms in rat MSCs. Cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Apoptosis was assessed by Hoechst 33258 nuclear staining and flow cytometric analysis with annexin V/PI staining. The gene expression of Toll-like receptor-4 (TLR-4) and V-erb-b2 erythroblastic leukemia viral oncogene homolog 2 (ErbB2) was detected by real-time polymerase chain reaction (PCR). The protein levels of cleaved caspase-3, Bcl-2, Bcl-xL, Bax, total-ERK, phospho-ERK, total-Akt, phospho-Akt, and Hsp90 were detected by Western blot. The production of nitric oxide was measured by spectrophotometric assay. Hsp90 improves MSC viability and protects MSCs against apoptosis induced by serum deprivation and hypoxia. The protective role of Hsp90 not only elevates Bcl-2/Bax and Bcl-xL/Bax expression and attenuates cleaved caspase-3 expression via down-regulating membrane TLR-4 and ErbB2 receptors and then activating their downstream PI3K/Akt and ERK1/2 pathways, but also enhances the paracrine effect of MSCs. These findings demonstrated a novel and effective treatment strategy against MSC apoptosis in cell transplantation.
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Affiliation(s)
- Feng Gao
- Department of Cardiology, the Second Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
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10
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Koletsa T, Kostopoulos I, Charalambous E, Christoforidou B, Nenopoulou E, Kotoula V. A splice variant of HER2 corresponding to Herstatin is expressed in the noncancerous breast and in breast carcinomas. Neoplasia 2008; 10:687-96. [PMID: 18592003 PMCID: PMC2434206 DOI: 10.1593/neo.08314] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2008] [Revised: 04/26/2008] [Accepted: 04/28/2008] [Indexed: 12/21/2022]
Abstract
Herstatin (HST) is an alternatively spliced HER2 product with growth-inhibitory properties in experimental cancer systems. The role of HST in adult human tissues and disease remains unexplored. Here, we investigated HST expression at the mRNA and protein (immunohistochemistry [IHC]) level in parallel with parameters reflecting HER activation in 187 breast carcinomas and matched noncancerous breast tissues (NCBT). Noncancerous breast tissues demonstrated the highest HST/HER2 transcript ratios corresponding to a few positive epithelial and stromal cells by IHC. Although HST/HER2 transcript ratios in tumors were inversely associated with HER2 IHC grading (P = .0048 for HER2 IHC-1+ and P = .0006 for HER2 IHC-2+ vs HER2-negative tumors), relative HST expression within the same tumor/NCBT system remained constant. HST/HER2 ratios did not predict the presence of HST protein, which was found in 46 (25%) of 187 tumors. A subgroup of HER2 IHC-3+ tumors exhibited high HST/HER2 transcript ratios, strong HST protein positivity, and cytoplasmic phospho-Akt/PKB and p21(CIP1/WAF1) localization. In conclusion, HST may act as a paracrine factor in the adult breast. Because HST is described as an endogenous pan-HER inhibitor, the presence of this protein in breast carcinomas may portent the inefficiency of exogenous efforts to block HER2 dimerization, whereas its absence may justify such interventions.
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Affiliation(s)
| | - Ioannis Kostopoulos
- Department of Pathology, Aristotle University Medical School, Thessaloniki, Greece
| | - Elpida Charalambous
- Department of Pathology, Aristotle University Medical School, Thessaloniki, Greece
| | | | - Eleni Nenopoulou
- Department of Pathology, Aristotle University Medical School, Thessaloniki, Greece
| | - Vassiliki Kotoula
- Department of Pathology, Aristotle University Medical School, Thessaloniki, Greece
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11
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Wang J, Feng J, Shi M, Qian L, Chen L, Yu M, Xu R, Shen B, Guo N. De novo design of ErbB2 epitope targeting fusion protein stabilized by coiled coil structure. Mol Immunol 2008; 45:106-16. [PMID: 17572496 DOI: 10.1016/j.molimm.2007.05.001] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Revised: 04/30/2007] [Accepted: 05/08/2007] [Indexed: 01/07/2023]
Abstract
The extracellular cysteine-rich domains of ErbB2 receptors play important roles in ligand binding and receptor dimerization. The aim of the present study was to design a novel peptide exerting cytostatic effect toward ErbB2-overexpressing tumors based on one of the cysteine-rich domain (S1) of ErbB2. In order to create a stable molecule with unique structural and binding property, a chimeric molecule PL45 composed of ErbB2 S1 domain targeting peptide and the five stranded coiled coil domain from cartilage oligomeric matrix protein (COMP) was generated. PL45 was efficiently expressed in Escherichia coli and exhibited remarkable thermal and pH stability. It was capable of interfering with dimerization of ErbB2 and inhibiting the growth of ErbB2-overexpressing tumor cells in vitro and in vivo. The results provide evidence that the coiled coil structure can be used as a new scaffold to stabilize short peptides with potential application for anti-cancer immunotherapy and S1 domain of ErbB2 is a promising target for drug design.
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Affiliation(s)
- Jianing Wang
- Institute of Basic Medical Sciences, Taiping Road 27, Beijing 100850, PR China
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12
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Fisher MC, Clinton GM, Maihle NJ, Dealy CN. Requirement for ErbB2/ErbB signaling in developing cartilage and bone. Dev Growth Differ 2007; 49:503-13. [PMID: 17555517 DOI: 10.1111/j.1440-169x.2007.00941.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
During endochondral ossification, the skeletal elements of vertebrate limbs form and elongate via coordinated control of chondrocyte and osteoblast differentiation and proliferation. The role of signaling by the ErbB family of receptor tyrosine kinases, which consists of ErbB1 (epidermal growth factor receptor or EGFR), ErbB2, ErbB3 and ErbB4, has been little studied during cartilage and bone development. Signaling by the ErbB network generates a diverse array of cellular responses via formation of ErbB dimers activated by distinct ligands that produce distinct signal outputs. Herstatin is a soluble ErbB2 receptor that acts in a dominant negative fashion to inhibit ErbB signaling by binding to endogenous ErbB receptors, preventing functional dimer formation. Here, we examine the effects of Herstatin on limb skeletal element development in transgenic mice, achieved via Prx1 promoter-driven expression in limb cartilage and bone. The limb skeletal elements of Prx1-Herstatin embryos are shortened, and chondrocyte maturation and osteoblast differentiation are delayed. In addition, proliferation by chondrocytes and periosteal cells of Prx1-Herstatin limb skeletal elements is markedly reduced. Our study identifies requirements for ErbB signaling in the maintenance of chondrocyte and osteoblast proliferation involved in the timely progression of chondrocyte maturation and periosteal osteoblast differentiation.
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Affiliation(s)
- Melanie C Fisher
- Center for Regenerative Medicine and Skeletal Development, Department of Reconstructive Sciences, University of Connecticut Health Center, 263 Farmington Avenue, Farmington, Connecticut 06030, USA
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Hu P, Zhou T, Qian L, Wang J, Shi M, Yu M, Yang Y, Zhang X, Shen B, Guo N. Sequestering ErbB2 in endoplasmic reticulum by its autoinhibitor from translocation to cell surface: An autoinhibition mechanism of ErbB2 expression. Biochem Biophys Res Commun 2006; 342:19-27. [PMID: 16469294 DOI: 10.1016/j.bbrc.2006.01.115] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2006] [Accepted: 01/24/2006] [Indexed: 11/30/2022]
Abstract
ErbB2 is differentially overexpressed in tumor versus host tissues, suggesting that an autoregulation mechanism may modulate the expression of ErbB2 and control cell growth. A truncated ErbB2 extracellular domain, herstatin has been shown to bind to ErbB2 and inhibit the growth of tumor cells expressing ErbB2. In the present study, the interaction of herstatin and ErbB2 in vivo was observed by confocal microscopy. The aggregation of ErbB2 and herstatin was found in endoplasmic reticulum (ER). The decrease of ErbB2 on the cell surface was accompanied with the increased colocalization of ErbB2 and herstatin in the cytoplasm, suggesting that the formation of ErbB2/herstatin complex may prevent transit from ER to cell surface of ErbB2. The formation of ErbB2 and herstatin complex was further confirmed by immunoprecipitation. The results demonstrate that sequestering ErbB2 molecules intracellularly by herstatin may be a possible mechanism of the cell growth inhibition.
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Affiliation(s)
- Pinliang Hu
- Institute of Basic Medical Sciences, Beijing, PR China
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14
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Sweeney C, Miller JK, Shattuck DL, Carraway KL. ErbB receptor negative regulatory mechanisms: implications in cancer. J Mammary Gland Biol Neoplasia 2006; 11:89-99. [PMID: 16865534 DOI: 10.1007/s10911-006-9015-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Activation of ErbB receptor tyrosine kinases (RTKs) must be precisely regulated to ensure the fidelity of developmental and homeostatic processes mediated by growth factors. Insufficient receptor stimulation will lead to defects in tissue development, while excessive stimulation can lead to hyperplastic events associated with cancer and other diseases. A coordinated balance of the intensity and timing of receptor signaling, achieved through both receptor activation and negative regulatory mechanisms, is required for signaling fidelity. While considerable effort has gone into understanding mechanisms by which ErbB receptors are activated, our understanding of the suppression of growth factor receptor activity remains limited. While ligand-stimulated receptor degradation is the most thoroughly examined mechanism for preventing hyper-signaling by ErbBs, recent studies indicate that several other mechanisms act directly on receptors to suppress receptor levels, or the magnitude or duration of receptor signaling. ErbB receptor overexpression or aberrant activation contributes to the progression of numerous solid tumor types. Hence, tumor cells must overcome these endogenous receptor negative regulatory mechanisms before they can exploit ErbB receptors to achieve uncontrolled growth. Here we will discuss several proteins that directly interact with ErbB receptors to suppress signaling, highlighting the potential impact of their loss on tumor progression.
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Affiliation(s)
- Colleen Sweeney
- UC Davis Cancer Center, Research Bldg. III, rm 1400, 4645 2nd Avenue, Sacramento, CA 95817, USA.
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