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Gelineau-van Waes J, Maddox JR, Smith LM, van Waes M, Wilberding J, Eudy JD, Bauer LK, Finnell RH. Microarray analysis of E9.5 reduced folate carrier (RFC1; Slc19a1) knockout embryos reveals altered expression of genes in the cubilin-megalin multiligand endocytic receptor complex. BMC Genomics 2008; 9:156. [PMID: 18400109 PMCID: PMC2383917 DOI: 10.1186/1471-2164-9-156] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2007] [Accepted: 04/09/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The reduced folate carrier (RFC1) is an integral membrane protein and facilitative anion exchanger that mediates delivery of 5-methyltetrahydrofolate into mammalian cells. Adequate maternal-fetal transport of folate is necessary for normal embryogenesis. Targeted inactivation of the murine RFC1 gene results in post-implantation embryolethality, but daily folic acid supplementation of pregnant dams prolongs survival of homozygous embryos until mid-gestation. At E10.5 RFC1-/- embryos are developmentally delayed relative to wildtype littermates, have multiple malformations, including neural tube defects, and die due to failure of chorioallantoic fusion. The mesoderm is sparse and disorganized, and there is a marked absence of erythrocytes in yolk sac blood islands. The identification of alterations in gene expression and signaling pathways involved in the observed dysmorphology following inactivation of RFC1-mediated folate transport are the focus of this investigation. RESULTS Affymetrix microarray analysis of the relative gene expression profiles in whole E9.5 RFC1-/- vs. RFC1+/+ embryos identified 200 known genes that were differentially expressed. Major ontology groups included transcription factors (13.04%), and genes involved in transport functions (ion, lipid, carbohydrate) (11.37%). Genes that code for receptors, ligands and interacting proteins in the cubilin-megalin multiligand endocytic receptor complex accounted for 9.36% of the total, followed closely by several genes involved in hematopoiesis (8.03%). The most highly significant gene network identified by Ingenuitytrade mark Pathway analysis included 12 genes in the cubilin-megalin multiligand endocytic receptor complex. Altered expression of these genes was validated by quantitative RT-PCR, and immunohistochemical analysis demonstrated that megalin protein expression disappeared from the visceral yolk sac of RFC1-/- embryos, while cubilin protein was widely misexpressed. CONCLUSION Inactivation of RFC1 impacts the expression of several ligands and interacting proteins in the cubilin-amnionless-megalin complex that are involved in the maternal-fetal transport of folate and other nutrients, lipids and morphogens such as sonic hedgehog (Shh) and retinoids that play critical roles in normal embryogenesis.
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Affiliation(s)
- Janee Gelineau-van Waes
- Department of Genetics, Cell Biology & Anatomy, University of Nebraska Medical Center, Omaha, NE 68198-5455, USA.
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52
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Diwakar R, Pearson AL, Colville-Nash P, Baines DL, Dockrell MEC. Role played by disabled-2 in albumin induced MAP Kinase signalling. Biochem Biophys Res Commun 2007; 366:675-80. [PMID: 18070591 DOI: 10.1016/j.bbrc.2007.11.171] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2007] [Accepted: 11/27/2007] [Indexed: 10/22/2022]
Abstract
Albumin has been shown to activate the mitogen activated protein kinase (MAPK) pathway in proximal tubular cells (PTECs) of the kidney. Megalin, the putative receptor for albumin has potential signalling properties. However, the mechanisms by which megalin signals are unclear. The adaptor phosphoprotein Disabled-2 (Dab2) is known to interact with the cytoplasmic tail of megalin and may be involved in albumin-mediated MAPK signalling. In this study, we investigated the role of Dab2 in albumin-mediated MAPK signalling and further studied the role of Dab2 in albumin-induced TGFbeta-1 secretion, a MAPK dependent event. We used RNA interference to knockdown Dab2 protein abundance in HKC-8 cells a model of human PTECs. Albumin activated ERK1,2 and Elk-1 in a MEK-1 dependent manner and resulted in secretion of TGFbeta-1. In the absence of albumin, knockdown of Dab2 resulted in a trend towards increase in pERK1,2 consistent with its putative role as an inhibitor of cell proliferation. However albumin-induced ERK1,2 activation was completely abolished by Dab2 knockdown. Dab2 knockdown did not however result in inhibition of albumin-induced TGFbeta-1 secretion. These results suggest that Dab2 is a ligand dependent bi-directional regulator of ERK1,2 activity by demonstrating that in addition to its more traditional role as an inhibitor of ERK1,2 it may also activate ERK1,2.
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Affiliation(s)
- Ramaswamy Diwakar
- South West Thames Institute for Renal Research, St. Helier Hospital, Wrythe Lane, Carshalton, Surrey SM5 1AA, UK
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53
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Abstract
beta-Catenin-mediated Wnt signaling is essential in embryonic development and in adult tissues. Recent studies have demonstrated that Axin not only plays an important inhibitory role in coordinating beta-catenin degradation, but is itself degraded by the low-density-lipoprotein receptor-related protein (LRP)5/6 Wnt co-receptor. Here, we demonstrate that the endocytic adaptor molecule Disabled-2 (Dab2), which we have previously demonstrated to act as an inhibitor of beta-catenin signaling, interacts with Axin and prevents its interaction with and degradation by the LRP5 co-receptor, thereby increasing its half-life and stabilization. Dab2 levels induced during retinoic acid-induced differentiation of F9, or during transforming growth factor-beta-induced epithelial-mesenchymal transdifferentiation of mouse mammary epithelial cells result in the stabilization of Axin and concomitant inhibition of beta-catenin signaling. Ectopic expression of Dab2 in F9 cells as well as in transformed cell lines results in increased Axin expression and attenuation of Wnt-mediated signaling. We conclude that Dab2 may play an important role in the maintenance of the differentiated state and restrain Wnt-mediated proliferation through its association with and modulation of Axin.
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54
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The inhibitory effects of Disabled-2 (Dab2) on Wnt signaling are mediated through Axin. Oncogene 2007. [PMID: 17922036 DOI: 10.1038/sj.onc.121082] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
beta-Catenin-mediated Wnt signaling is essential in embryonic development and in adult tissues. Recent studies have demonstrated that Axin not only plays an important inhibitory role in coordinating beta-catenin degradation, but is itself degraded by the low-density-lipoprotein receptor-related protein (LRP)5/6 Wnt co-receptor. Here, we demonstrate that the endocytic adaptor molecule Disabled-2 (Dab2), which we have previously demonstrated to act as an inhibitor of beta-catenin signaling, interacts with Axin and prevents its interaction with and degradation by the LRP5 co-receptor, thereby increasing its half-life and stabilization. Dab2 levels induced during retinoic acid-induced differentiation of F9, or during transforming growth factor-beta-induced epithelial-mesenchymal transdifferentiation of mouse mammary epithelial cells result in the stabilization of Axin and concomitant inhibition of beta-catenin signaling. Ectopic expression of Dab2 in F9 cells as well as in transformed cell lines results in increased Axin expression and attenuation of Wnt-mediated signaling. We conclude that Dab2 may play an important role in the maintenance of the differentiated state and restrain Wnt-mediated proliferation through its association with and modulation of Axin.
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55
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Karam JA, Shariat SF, Huang HY, Pong RC, Ashfaq R, Shapiro E, Lotan Y, Sagalowsky AI, Wu XR, Hsieh JT. Decreased DOC-2/DAB2 Expression in Urothelial Carcinoma of the Bladder. Clin Cancer Res 2007; 13:4400-6. [PMID: 17671122 DOI: 10.1158/1078-0432.ccr-07-0287] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
PURPOSE DOC-2/DAB2 (differentially expressed in ovarian carcinoma-2/disabled-2), a potential tumor suppressor gene, is underexpressed in several cancers. Little is known about the expression of this gene in urothelial carcinoma of the bladder (UCB). We profiled DOC-2/DAB2 expression in mouse and human normal and neoplastic urothelia. EXPERIMENTAL DESIGN Immunohistochemical staining for DOC-2/DAB2 was carried out on tissue specimens from two transgenic mouse models with urothelium-specific molecular alterations and on a tissue microarray containing cores from 9 normal controls, 44 patients who underwent transurethral resection of the bladder tumor (TURBT), 195 patients who underwent radical cystectomy for UCB, and 39 lymph nodes with metastatic UCB. RESULTS Normal mouse urothelium stained uniformly with DOC-2/DAB2. Weaker staining was observed in low-grade, superficial papillary bladder tumors from transgenic mice harboring constitutively active Ha-Ras, whereas carcinoma in situ-like lesions and high-grade bladder tumors from transgenic mice expressing a SV40 T antigen completely lacked DOC-2/DAB2 expression. In human tissues, DOC-2/DAB2 expression was decreased in 11% of normal bladder specimens, 59% of TURBT specimens, 65% of radical cystectomy specimens, and 77% of the metastatic lymph node specimens. Decreased DOC-2/DAB2 expression was associated with advanced pathologic stage (P = 0.023), lymph node metastases (P = 0.050), and lymphovascular invasion (P < 0.001). In univariable, but not in multivariable analysis, decreased DOC-2/DAB2 was associated with an increased probability of bladder cancer recurrence (log-rank test, P = 0.020) and bladder cancer-specific mortality (log-rank test, P = 0.023). CONCLUSIONS Decreased DOC-2/DAB2 expression seems to occur early in bladder tumorigenesis and becomes more prominent in advanced stages of UCB.
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MESH Headings
- Adaptor Proteins, Signal Transducing/metabolism
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/physiology
- Adult
- Aged
- Aged, 80 and over
- Animals
- Apoptosis Regulatory Proteins
- Biomarkers, Tumor/metabolism
- Carcinoma, Transitional Cell/metabolism
- Carcinoma, Transitional Cell/secondary
- Carcinoma, Transitional Cell/surgery
- Cohort Studies
- Cystectomy
- Female
- Humans
- Lymphatic Metastasis
- Male
- Mice
- Mice, Transgenic
- Middle Aged
- Neoplasm Invasiveness
- Neoplasm Recurrence, Local/metabolism
- Neoplasm Recurrence, Local/pathology
- Neoplasm Staging
- Survival Rate
- Tumor Suppressor Proteins
- Urinary Bladder Neoplasms/metabolism
- Urinary Bladder Neoplasms/pathology
- Urinary Bladder Neoplasms/surgery
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Affiliation(s)
- Jose A Karam
- Department of Urology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, USA
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56
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Romero DG, Yanes LL, de Rodriguez AF, Plonczynski MW, Welsh BL, Reckelhoff JF, Gomez-Sanchez EP, Gomez-Sanchez CE. Disabled-2 is expressed in adrenal zona glomerulosa and is involved in aldosterone secretion. Endocrinology 2007; 148:2644-52. [PMID: 17303656 DOI: 10.1210/en.2006-1509] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
The differentiation of the adrenal cortex into functionally specific zones is probably due to differential temporal gene expression during fetal growth, development, and adulthood. In our search for adrenal zona glomerulosa-specific genes, we found that Disabled-2 (Dab2) is expressed in the zona glomerulosa of the rat adrenal gland using a combination of laser capture microdissection, mRNA amplification, cDNA microarray hybridization, and real-time RT-PCR. Dab2 is an alternative spliced mitogen-regulated phosphoprotein with features of an adaptor protein and functions in signal transduction, endocytosis, and tissue morphogenesis during embryonic development. We performed further studies to analyze adrenal Dab2 localization, regulation, and role in aldosterone secretion. We found that Dab2 is expressed in the zona glomerulosa and zona intermedia of the rat adrenal cortex. Low-salt diet treatment increased Dab2-long isoform expression at the mRNA and protein level in the rat adrenal gland, whereas high-salt diet treatment did not cause any significant modification. Angiotensin II infusion caused a transient increase in both Dab2 isoform mRNAs in the rat adrenal gland. Dab2 overexpression in H295R human adrenocortical cells caused an increase in aldosterone synthase expression and up-regulated aldosterone secretion under angiotensin II-stimulated conditions. In conclusion, Dab2 is an adrenal gland zona glomerulosa- and intermedia-expressed gene that is regulated by aldosterone secretagogues such as low-salt diet or angiotensin II and is involved in aldosterone synthase expression and aldosterone secretion. Dab2 may therefore be a modulator of aldosterone secretion and be involved in mineralocorticoid secretion abnormalities.
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Affiliation(s)
- Damian G Romero
- Division of Endocrinology, Department of Medicine, Montgomery VA Medical Center and The University of Mississippi Medical Center, 2500 North State Street, Jackson, MS 39216, USA.
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57
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Huang CH, Cheng JC, Chen JC, Tseng CP. Evaluation of the role of Disabled-2 in nerve growth factor-mediated neurite outgrowth and cellular signalling. Cell Signal 2007; 19:1339-47. [PMID: 17317100 DOI: 10.1016/j.cellsig.2007.01.019] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2006] [Revised: 01/10/2007] [Accepted: 01/10/2007] [Indexed: 11/18/2022]
Abstract
Disabled-2 (DAB2) is an adapter protein that plays a key role in cell proliferation and differentiation. We reported here that DAB2 is expressed in various regions of rat central nervous system and is most abundant in the olfactory bulb. The up-regulation of DAB2 upon 5,7-dihydroxytryptamine-induced spinal cord lesion implicates that DAB2 may participate in the regulation of neuronal plasticity. To investigate DAB2 function in the regulation of neurite outgrowth, the rat p59 and p82 form of DAB2 was individually and stably expressed in the PC12 cells. Both p59 and p82 inhibited nerve growth factor (NGF)-induced neurite outgrowth concomitantly with a decrease in the expression of neuron-specific cytoskeleton protein beta-tubulin III. To unveil the molecular mechanism of DAB2 in NGF signaling, we found that RhoA-GTPase activity was up-regulated in DAB2 stable lines whereas the Ras/MAPK and PI3-kinase/Akt signaling was not affected. The inhibitory effect of DAB2 on NGF-mediated neurite outgrowth was reversed by the pretreatment of Rho-kinase (ROCK) inhibitor Y27632, implicating that DAB2 modulates RhoA/ROCK signaling. Together, this study defines a role of DAB2 in the control of neuronal plasticity and demonstrates for the first time that DAB2 is a negative regulator in NGF-mediated neurite outgrowth.
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Affiliation(s)
- Ching-Hui Huang
- Graduate Institute of Basic Medical Sciences, Chang Gung University, Taoyuan 333, Taiwan, Republic of China
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58
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Kumbar DH, VanBergen A, Ocampo C, Muangmingsuk S, Griffin AJ, Gupta M. Adapter molecule DOC-2 is differentially expressed in pressure and volume overload hypertrophy and inhibits collagen synthesis in cardiac fibroblasts. J Appl Physiol (1985) 2007; 102:2024-32. [PMID: 17255372 DOI: 10.1152/japplphysiol.00924.2006] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
DOC-2 (differentially expressed in ovarian carcinoma) is involved in Ras-, β-integrin-, PKC-, and transforming growth factor-β-mediated cell signaling. These pathways are implicated in the accumulation of extracellular matrix proteins during progression of hypertrophy to heart failure; however, the role of DOC-2 in cardiac pathophysiology has never been examined. This study was undertaken to 1) analyze DOC-2 expression in primary cultures of cardiac fibroblasts and cardiac myocytes and in the heart following different types of hemodynamic overloads and 2) examine its role in growth factor-mediated ERK activation and collagen production. Pressure overload and volume overload were induced for 10 wk in Sprague-Dawley rats by aortic constriction and by aortocaval shunt, respectively. ANG II (0.3 mg·kg−1·day−1) was infused for 2 wk. Results showed that, compared with myocytes, DOC-2 was found abundantly expressed in cardiac fibroblasts. Treatment of cardiac fibroblasts with ANG II and TPA resulted in increased expression of DOC-2. Overexpression of DOC-2 in cardiac fibroblasts led to inhibition of hypertrophy agonist-stimulated ERK activation and collagen expression. An inverse correlation between collagen and DOC-2 was observed in in vivo models of cardiac hypertrophy; in pressure overload and after ANG II infusion, increased collagen mRNA correlated with reduced DOC-2 levels, whereas in volume overload increased DOC-2 levels were accompanied by unchanged collagen mRNA. These data for the first time describe expression of DOC-2 in the heart and demonstrate its modulation by growth-promoting agents in cultured cardiac fibroblasts and in in vivo models of heart hypertrophy. Results suggest a role of DOC-2 in cardiac remodeling involving collagen expression during chronic hemodynamic overload.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/metabolism
- Angiotensin II/metabolism
- Angiotensin II/pharmacology
- Animals
- Aorta, Abdominal/surgery
- Arteriovenous Shunt, Surgical
- Cardiomegaly/genetics
- Cardiomegaly/metabolism
- Cardiomegaly/pathology
- Cardiomegaly/physiopathology
- Cells, Cultured
- Collagen/biosynthesis
- Collagen/genetics
- Disease Models, Animal
- Extracellular Signal-Regulated MAP Kinases/antagonists & inhibitors
- Extracellular Signal-Regulated MAP Kinases/metabolism
- Fibroblasts/drug effects
- Fibroblasts/metabolism
- Fibroblasts/pathology
- Flavonoids/pharmacology
- Gene Expression
- Ligation
- Myocytes, Cardiac/drug effects
- Myocytes, Cardiac/metabolism
- Myocytes, Cardiac/pathology
- Phorbol Esters/pharmacology
- Phosphorylation
- Protein Kinase C/metabolism
- Protein Kinase Inhibitors/pharmacology
- RNA, Messenger/metabolism
- Rats
- Rats, Sprague-Dawley
- Signal Transduction/drug effects
- Transfection
- Ventricular Remodeling
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Affiliation(s)
- Deepa H Kumbar
- The Heart Institute for Children, Advocate Hope Children's Hospital, Oak Lawn, IL, USA
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Xenopus Dab2 is required for embryonic angiogenesis. BMC DEVELOPMENTAL BIOLOGY 2006; 6:63. [PMID: 17176484 PMCID: PMC1766927 DOI: 10.1186/1471-213x-6-63] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2006] [Accepted: 12/19/2006] [Indexed: 12/21/2022]
Abstract
BACKGROUND The molecular mechanisms governing the formation of the embryonic vascular system remain poorly understood. Here, we show that Disabled-2 (Dab2), a cytosolic adaptor protein, has a pivotal role in the blood vessel formation in Xenopus early embryogenesis. RESULTS Xenopus Disabled-2 (XDab2) is spatially localized to the blood vessels including the intersomitic veins (ISV) in early embryos. Both antisense morpholino oligonucleotide (MO)-mediated knockdown and overexpression of XDab2 inhibit the formation of ISV, which arise from angiogenesis. In addition, we found that activin-like signaling is essential for this angiogenic event. Functional assays in Xenopus animal caps reveal that activin-like signals induce VEGF expression and this induction can be inhibited by XDab2 depletion. However, XDab2 MO has no effects on the induction of other target genes by activin-like signals. Furthermore, we show that the disruption of the sprouting ISV in XDab2-depleted embryos can be rescued by coexpression of VEGF. CONCLUSION Taking together, we suggest that XDab2 regulates the embryonic angiogenesis by mediating the VEGF induction by activin-like signaling in Xenopus early development.
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Anupam K, Tusharkant C, Gupta SD, Ranju R. Loss of disabled-2 expression is an early event in esophageal squamous tumorigenesis. World J Gastroenterol 2006; 12:6041-5. [PMID: 17009406 PMCID: PMC4124415 DOI: 10.3748/wjg.v12.i37.6041] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
AIM: Disabled-2 (DAB2) is a candidate tumor-suppressor gene identified in ovarian cancer that negatively influences mitogenic signal transduction of growth factors and blocks ras activity. In a recent study, we observed down-regulation of DAB2 transcripts in ESCCs using cDNA microarrays. In the present study, we aimed to determine the clinical significance of loss of DAB2 protein in esophageal tumorigenesis, hypothesizing that DAB2 promoter hypermethylation-mediated gene silencing may account for loss of the protein.
METHODS: DAB2 expression was analyzed by immunohistochemistry in 50 primary esophageal squamous cell carcinomas (ESCCs), 30 distinct hyperplasia, 15 dysplasia and 10 non-malignant esophageal tissues. To determine whether promoter hypermethylation contributes to loss of DAB2 expression in ESCCs, methylation status of DAB2 promoter was analyzed in DAB2 immuno-negative tumors using methylation-specific PCR.
RESULTS: Loss of DAB2 protein was observed in 5/30 (17%) hyperplasia, 10/15 (67%) dysplasia and 34/50 (68%) ESCCs. Significant loss of DAB2 protein was observed from esophageal normal mucosa to hyperplasia, dysplasia and invasive cancer (Ptrend < 0.001). Promoter hypermethylation of DAB2 was observed in 2 of 10 (20%) DAB2 immuno-negative ESCCs.
CONCLUSION: Loss of DAB2 protein expression occurs in early pre-neoplastic stages of development of esophageal cancer and is sustained down the tumorigenic pathway. Infrequent DAB2 promoter methylation in ESCCs suggests that epigenetic gene silencing is only one of the mechanisms causing loss of DAB2 expression in ESCCs.
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MESH Headings
- Adaptor Proteins, Signal Transducing/genetics
- Adaptor Proteins, Signal Transducing/metabolism
- Adult
- Apoptosis Regulatory Proteins
- Carcinoma, Squamous Cell/genetics
- Carcinoma, Squamous Cell/metabolism
- Carcinoma, Squamous Cell/pathology
- Cell Transformation, Neoplastic/genetics
- Cell Transformation, Neoplastic/metabolism
- Cell Transformation, Neoplastic/pathology
- DNA Methylation
- DNA, Neoplasm/genetics
- DNA, Neoplasm/metabolism
- Down-Regulation
- Esophageal Neoplasms/genetics
- Esophageal Neoplasms/metabolism
- Esophageal Neoplasms/pathology
- Esophagus/metabolism
- Esophagus/pathology
- Exons/genetics
- Female
- Gene Expression Regulation, Neoplastic
- Humans
- Hyperplasia
- Immunohistochemistry
- Male
- Middle Aged
- Oligonucleotide Array Sequence Analysis
- Tumor Suppressor Proteins
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Affiliation(s)
- Kumar Anupam
- Department of Biochemistry, All India Institute of Medical Sciences, Ansari Nagar, New Delhi 110029, India
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61
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Yang DH, Fazili Z, Smith ER, Cai KQ, Klein-Szanto A, Cohen C, Horowitz IR, Xu XX. Disabled-2 heterozygous mice are predisposed to endometrial and ovarian tumorigenesis and exhibit sex-biased embryonic lethality in a p53-null background. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 169:258-67. [PMID: 16816378 PMCID: PMC1698752 DOI: 10.2353/ajpath.2006.060036] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Disabled-2 (Dab2) is a phosphoprotein involved in cellular signal transduction and endocytic trafficking. The expression of Dab2 is frequently lost or suppressed in several epithelial tumors, and studies of its cellular function and growth suppressive activity when re-expressed in cancer cells led to the suggestion that Dab2 is a tumor suppressor. A role for Dab2 in epithelial cell positioning organization was derived from study of knockout mice: homozygous deletion of dab2 results in early embryonic lethality due to the disorganization of the primitive endoderm, the first epithelium in early embryos. We now report that dab2 heterozygous mice develop uterine hyperplasia and ovarian preneoplastic morphological changes at a high frequency. Crossing into a p53(-/-) background unexpectedly produced few female dab2(+/-):p53(-/-) mice, while the male dab2(+/-):p53(-/-) were born at the expected Mendelian frequency. The tumor-prone phenotype of dab2(+/-) mice provides additional support for a role of human Dab2 as a tumor suppressor, and the sex-biased embryonic lethality suggests a genetic interaction between p53 and dab2 genes in female mice.
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Affiliation(s)
- Dong-Hua Yang
- Ovarian Cancer and Tumor Cell Biology Programs, Fox Chase Cancer Center, 333 Cottman Ave., Philadelphia, PA 19111-2497, USA
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62
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Keyel PA, Mishra SK, Roth R, Heuser JE, Watkins SC, Traub LM. A single common portal for clathrin-mediated endocytosis of distinct cargo governed by cargo-selective adaptors. Mol Biol Cell 2006; 17:4300-17. [PMID: 16870701 PMCID: PMC1635374 DOI: 10.1091/mbc.e06-05-0421] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Sorting of transmembrane cargo into clathrin-coated vesicles requires endocytic adaptors, yet RNA interference (RNAi)-mediated gene silencing of the AP-2 adaptor complex only disrupts internalization of a subset of clathrin-dependent cargo. This suggests alternate clathrin-associated sorting proteins participate in cargo capture at the cell surface, and a provocative recent proposal is that discrete endocytic cargo are sorted into compositionally and functionally distinct clathrin coats. We show here that the FXNPXY-type internalization signal within cytosolic domain of the LDL receptor is recognized redundantly by two phosphotyrosine-binding domain proteins, Dab2 and ARH; diminishing both proteins by RNAi leads to conspicuous LDL receptor accumulation at the cell surface. AP-2-dependent uptake of transferrin ensues relatively normally in the absence of Dab2 and ARH, clearly revealing delegation of sorting operations at the bud site. AP-2, Dab2, ARH, transferrin, and LDL receptors are all present within the vast majority of clathrin structures at the surface, challenging the general existence of specialized clathrin coats for segregated internalization of constitutively internalized cargo. However, Dab2 expression is exceptionally low in hepatocytes, likely accounting for the pathological hypercholesterolemia that accompanies ARH loss.
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Affiliation(s)
- Peter A. Keyel
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Sanjay K. Mishra
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Robyn Roth
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - John E. Heuser
- Department of Cell Biology and Physiology, Washington University School of Medicine, St. Louis, MO 63110
| | - Simon C. Watkins
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
| | - Linton M. Traub
- *Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, Pittsburgh, PA 15261; and
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63
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Maurer ME, Cooper JA. Endocytosis of megalin by visceral endoderm cells requires the Dab2 adaptor protein. J Cell Sci 2005; 118:5345-55. [PMID: 16263760 DOI: 10.1242/jcs.02650] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rapid endocytosis of lipoprotein receptors involves NPxY signals contained in their cytoplasmic tails. Several proteins, including ARH and Dab2, can bind these sequences, but their importance for endocytosis may vary in different cell types. The lipoprotein receptor megalin is expressed in the visceral endoderm (VE), a polarized epithelium that supplies maternal nutrients to the early mammalian embryo. Dab2 is also expressed in the VE, and is required for embryo growth and gastrulation. Here, we show that ARH is absent from the VE, and Dab2 is required for uptake of megalin, its co-receptor cubilin, and a cubilin ligand, transferrin, from the brush border of the VE into intracellular vesicles. By making isoform-specific knock-in mice, we show that the p96 splice form of Dab2, which binds endocytic proteins, can fully rescue endocytosis. The more abundant p67 isoform, which lacks some endocytic protein binding sites, only partly rescues endocytosis. Endocytosis of cubilin is also impaired in VE and in mid-gestation visceral yolk sac when p96 is absent. These studies suggest that Dab2 p96 mediates endocytosis of megalin in the VE. In addition, rescue of embryonic viability correlates with endocytosis, suggesting that endocytosis mediated by Dab2 is important for normal development.
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MESH Headings
- Adaptor Proteins, Signal Transducing/deficiency
- Adaptor Proteins, Vesicular Transport/deficiency
- Adaptor Proteins, Vesicular Transport/genetics
- Adaptor Proteins, Vesicular Transport/metabolism
- Alternative Splicing/genetics
- Animals
- Apoptosis Regulatory Proteins
- Cell Survival
- Embryo, Mammalian/cytology
- Embryo, Mammalian/metabolism
- Embryo, Mammalian/ultrastructure
- Embryonic Development
- Endocytosis
- Endoderm/cytology
- Endoderm/metabolism
- Low Density Lipoprotein Receptor-Related Protein-2/metabolism
- Mice
- Organ Specificity
- Protein Isoforms
- Protein Transport
- RNA, Messenger/genetics
- RNA, Messenger/metabolism
- Receptors, Cell Surface/metabolism
- Transgenes/genetics
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Affiliation(s)
- Meghan E Maurer
- Division of Basic Sciences and Molecular and Cellular Biology Program, Fred Hutchinson Cancer Research Center, 1100 Fairview Ave N, Seattle, WA 98109, USA
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64
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Zhou J, Hernandez G, Tu SW, Scholes J, Chen H, Tseng CP, Hsieh JT. Synergistic induction of DOC-2/DAB2 gene expression in transitional cell carcinoma in the presence of GATA6 and histone deacetylase inhibitor. Cancer Res 2005; 65:6089-96. [PMID: 16024609 DOI: 10.1158/0008-5472.can-04-3672] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The down-regulation of DOC-2/DAB2 gene, which encodes a unique phosphoprotein modulating signal pathways elicited by exogenous stimuli, is often associated with several cancer types; however, the underlying mechanism is still unknown. Dramatically different expression levels of DOC-2/DAB2 mRNA and protein are observed among several human transitional cell carcinoma (TCC) cell lines, suggesting that transcriptional regulation may play a role in these cells. In this study, we have shown that the histone acetylation status associated with the 5' upstream regulatory sequence of DOC-2/DAB2 gene is one of the key determinants for its gene expression. In addition, GATA6 but not other GATA family members, such as GATA2 and GATA4, can specifically induce DOC-2/DAB2 promoter activity, although GATA transcription factors share a very similar DNA-binding sequence. We also show that increased histone acetylation and the presence of GATA6 have a synergistic effect on DOC-2/DAB2 promoter activity, which results in the elevation of DOC-2/DAB2 protein expression. Thus, we conclude that transcriptional regulation of DOC-2/DAB2 gene in human TCC is determined by histone acetylation and a specific transcription factor (i.e., GATA6), which underlie the reduced DOC-2/DAB2 protein expression in TCC cells.
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MESH Headings
- Acetylation
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport/biosynthesis
- Adaptor Proteins, Vesicular Transport/genetics
- Apoptosis Regulatory Proteins
- Base Sequence
- Carcinoma, Transitional Cell/enzymology
- Carcinoma, Transitional Cell/genetics
- Carcinoma, Transitional Cell/metabolism
- Cell Line, Tumor
- Chromatin/genetics
- Chromatin/metabolism
- DNA-Binding Proteins/biosynthesis
- DNA-Binding Proteins/genetics
- DNA-Binding Proteins/metabolism
- Depsipeptides/pharmacology
- Down-Regulation
- GATA6 Transcription Factor
- Gene Expression Regulation, Neoplastic
- Genes, Tumor Suppressor
- Genetic Vectors/genetics
- Histone Deacetylase Inhibitors
- Histone Deacetylases/metabolism
- Histones/metabolism
- Humans
- Molecular Sequence Data
- Promoter Regions, Genetic
- Transcription Factors/biosynthesis
- Transcription Factors/genetics
- Transcription Factors/metabolism
- Transfection
- Tumor Suppressor Proteins
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Affiliation(s)
- Jian Zhou
- Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9110, USA
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65
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Airik R, Kärner M, Karis A, Kärner J. Gene expression analysis of Gata3-/- mice by using cDNA microarray technology. Life Sci 2005; 76:2559-68. [PMID: 15769480 DOI: 10.1016/j.lfs.2004.10.054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2004] [Accepted: 10/18/2004] [Indexed: 11/22/2022]
Abstract
Transcription factor Gata3 is implicated in the formation of autosomal dominant hypoparathyroidism, sensorineural deafness, and renal anomaly (HDR) syndrome. We pursued to identify the potential Gata3 target genes by profiling the gene expression pattern in E9.5 Gata3-/- mouse embryos. Altogether four independent microarray hybridizations were carried out on NIA Mouse15K cDNA arrays. We discovered two hundred and sixty one genes that are downregulated in Gata3 mutant embryos at E9.5 (with a minimal 2.0-fold change). The majority of the differentially expressed genes belong to two functional groups--genes involved in transcription regulation and cellular signaling. One of the genes discovered to be downregulated in Gata3 mutant embryos was tumor suppressor gene Disabled 2. The validity of this finding was checked by using the whole mount in situ hybridization technology. This study revealed that the sites, where Dab2 is downregulated in the mutant embryos partly overlap with the Gata3 expression domains, including the mid-embryo region, branchial arches and facio-acoustic (VII-VIII) neural crest complex. This is the first time when tumor supressor gene Dab2 is shown to be implicated in the defective phenotype of Gata3 mutant mice.
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Affiliation(s)
- Rannar Airik
- Department of Developmental Biology, Institute of Zoology and Hydrobiology, University of Tartu, Vanemuise 46, 51014 Tartu, Estonia
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66
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Nagai J, Christensen EI, Morris SM, Willnow TE, Cooper JA, Nielsen R. Mutually dependent localization of megalin and Dab2 in the renal proximal tubule. Am J Physiol Renal Physiol 2005; 289:F569-76. [PMID: 15870384 DOI: 10.1152/ajprenal.00292.2004] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Disabled-2 (Dab2) is a cytoplasmic adaptor protein that binds to the cytoplasmic tail of the multiligand endocytic receptor megalin, abundantly expressed in renal proximal tubules. Deletion of Dab2 induces a urinary increase in specific plasma proteins such as vitamin D binding protein and retinol binding protein (Morris SM, Tallquist MD, Rock CO, and Cooper JA. EMBO J 21: 1555-1564, 2002). However, the subcellular localization of Dab2 in the renal proximal tubule and its function have not been fully elucidated yet. Here, we report the characterization of Dab2 in the renal proximal tubule. Immunohistocytochemistry revealed colocalization with megalin in coated pits and vesicles but not in dense apical tubules and the brush border. Kidney-specific megalin knockout almost abolished Dab2 staining, indicating that Dab2 subcellular localization requires megalin in the proximal tubule. Reciprocally, knockout of Dab2 led to a redistribution of megalin from endosomes to microvilli. In addition, there was an overall decrease in levels of megalin protein observed by immunoblotting but no decrease in clathrin or alpha-adaptin protein levels or in megalin mRNA. In rat yolk sac epithelial BN16 cells, Dab2 was present apically and colocalized with megalin. Introduction of anti-Dab2 antibody into BN16 cells decreased the internalization of 125I-labeled receptor-associated protein, substantiating the role of Dab2 in megalin-mediated endocytosis. The present study shows that Dab2 is localized in the apical endocytic apparatus of the renal proximal tubule and that this localization requires megalin. Furthermore, the study suggests that the urinary loss of megalin ligands observed in Dab2 knockout mice is caused by suboptimal trafficking of megalin, leading to decreased megalin levels.
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Affiliation(s)
- J Nagai
- Cell Biology, Institute of Anatomy, Univ. of Aarhus, University Park, Bldg. 234, DK-8000 Aarhus C, Denmark
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67
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Dance AL, Miller M, Seragaki S, Aryal P, White B, Aschenbrenner L, Hasson T. Regulation of myosin-VI targeting to endocytic compartments. Traffic 2005; 5:798-813. [PMID: 15355515 DOI: 10.1111/j.1600-0854.2004.00224.x] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Myosin-VI has been implicated in endocytic trafficking at both the clathrin-coated and uncoated vesicle stages. The identification of alternative splice forms led to the suggestion that splicing defines the vesicle type to which myosin-VI is recruited. In contrast to this hypothesis, we find that in all cell types examined, myosin-VI is associated with uncoated endocytic vesicles, regardless of splice form. GIPC, a PDZ-domain containing adapter protein, co-assembles with myosin-VI on these vesicles. Myosin-VI is only recruited to clathrin-coated vesicles in cells that express high levels of Dab2, a clathrin-binding adapter protein. Overexpression of Dab2 is sufficient to reroute myosin-VI to clathrin-coated pits in cells where myosin-VI is normally associated with uncoated vesicles. In normal rat kidney (NRK) cells, which express high endogenous levels of Dab2, splicing of the globular tail domain further modulates targeting of ectopically expressed myosin-VI. Although myosin-VI can be recruited to clathrin-coated pits, we find no requirement for myosin-VI motor activity in endocytosis in NRK cells. Instead, our data suggest that myosin-VI recruitment to clathrin-coated pits may be an early step in the recruitment of GIPC to the vesicle surface.
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Affiliation(s)
- Amber L Dance
- Section of Cell and Developmental Biology, Division of Biological Sciences, University of California at San Diego, La Jolla, CA 92093, USA
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68
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Prunier C, Howe PH. Disabled-2 (Dab2) is required for transforming growth factor beta-induced epithelial to mesenchymal transition (EMT). J Biol Chem 2005; 280:17540-8. [PMID: 15734730 DOI: 10.1074/jbc.m500974200] [Citation(s) in RCA: 109] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Transforming growth factor beta (TGFbeta) induces an epithelial to mesenchymal transition (EMT) during both physiological and pathological processes; however, the mechanism underlying this transition is not fully elucidated. Here, we have demonstrated that TGFbeta induces the expression of the adaptor molecule disabled-2 (Dab2) concomitant with the promotion of EMT. We show that TGFbeta induces a transient accumulation of Dab2 to the membrane and increases Dab2 binding to beta1 integrin. Furthermore, small interfering RNA (siRNA)-mediated silencing of Dab2 expression in mouse mammary gland epithelial cells results in inhibition of integrin activation, shown by a decrease of both TGFbeta-induced focal adhesion kinase phosphorylation and cellular adherence, leading to apoptosis and inhibition of EMT. Forced re-expression of human Dab2, not targeted by the mouse siRNA sequence, rescues cells from apoptosis and restores TGFbeta-mediated integrin activation and EMT. These results are confirmed in the F9 teratocarcinoma cell line, a model for retinoic acid-induced visceral endoderm differentiation in which we demonstrate that ablation of retinoic acid-induced Dab2 expression levels, by stable siRNA silencing of Dab2, blocks visceral endoderm differentiation. Our findings indicate that Dab2 plays an important regulatory role during cellular differentiation and that induction of differentiation in the absence of Dab2 expression commits the cell to apoptosis.
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Affiliation(s)
- Céline Prunier
- Department of Cell Biology, The Lerner Research Institute, Cleveland Clinic Lerner College of Medicine, Cleveland Clinic Foundation, Cleveland, Ohio 44195, USA
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69
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Moon C, Lee J, Ahn M, Shin T. Involvement of Disabled-2 protein in the central nervous system inflammation following experimental cryoinjury of rat brains. Neurosci Lett 2005; 378:88-91. [PMID: 15774263 DOI: 10.1016/j.neulet.2004.12.016] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 12/06/2004] [Accepted: 12/06/2004] [Indexed: 11/21/2022]
Abstract
Disabled-2 (Dab-2) functions in the mitogenic signal transduction pathway, and is expressed in a variety of tissues. We investigated the roles of Dab-2 expression in the rat brain following experimental cryoinjury in relation to central nervous system (CNS) inflammation. Western blot analysis showed that Dab-2 expression increased significantly (p < 0.001) in the frontal cortex 4-14 days after cryoinjury, and declined slightly thereafter. Immunohistochemistry showed that Dab-2 immunostaining occurred in most of the vessels in the control cerebral cortex. After cryoinjury, Dab-2 was localized in the majority of inflammatory cells (especially in ED1-positive macrophages) in the core and periphery, as well as in vessels. These findings suggest that Dab-2 is involved in the inflammation that follows CNS injury through the migration of activated inflammatory cells in the rat brain.
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Affiliation(s)
- Changjong Moon
- Department of Veterinary Medicine, Cheju National University, Jeju 690-756, South Korea
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70
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Katyal S, Godbout R. Alternative splicing modulates Disabled-1 (Dab1) function in the developing chick retina. EMBO J 2004; 23:1878-88. [PMID: 15057276 PMCID: PMC394239 DOI: 10.1038/sj.emboj.7600185] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2003] [Accepted: 03/04/2004] [Indexed: 11/10/2022] Open
Abstract
The Reelin-Disabled 1 (Dab1)-signaling pathway plays a critical role in neuronal cell positioning in the brain. We have isolated two alternatively spliced variants of Dab1 from chick retina, an early form (chDab1-E) expressed in undifferentiated cells and a late form (chDab1-L) expressed in amacrine and ganglion cells. A key difference between the two forms is the exclusion in chDab1-E of two Src-related tyrosine kinase recognition sites implicated in Reelin-mediated Dab1 tyrosine phosphorylation. Retinal cultures transfected with a chDab1-L expression construct undergo a dramatic change in morphology, accompanied by the formation of numerous thin elongated processes, increased tyrosine phosphorylation, activation of Src family kinase(s) and increased levels of the axonal outgrowth protein growth-associated protein-43. In contrast, chDab1-E transfectants retain an undifferentiated morphology. Mutational analysis implicates a specific tyrosine (tyr-198) in the morphological and biochemical alterations associated with chDab1-L expression. We propose that alternative splicing of chDab1 represents an effective and flexible way of regulating the Reelin-Dab1-signaling pathway in a mixed cell population, by ensuring that secreted Reelin activates the signaling cascade only in target neuronal cells.
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Affiliation(s)
- Sachin Katyal
- Department of Oncology, Cross Cancer Institute, University of Alberta, Alberta, Canada
| | - Roseline Godbout
- Department of Oncology, Cross Cancer Institute, University of Alberta, Alberta, Canada
- Department of Oncology, Cross Cancer Institute, University of Alberta, 11560 University Avenue, CDN-Edmonton, Alberta, Canada T6G 1Z2. Tel.: +1 780 432 8901; Fax: +1 780 432 8892; E-mail:
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71
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Nagai J, Takano M. Molecular Aspects of Renal Handling of Aminoglycosides and Strategies for Preventing the Nephrotoxicity. Drug Metab Pharmacokinet 2004; 19:159-70. [PMID: 15499183 DOI: 10.2133/dmpk.19.159] [Citation(s) in RCA: 167] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Aminoglycosides such as gentamicin and amikacin are the most commonly used antibiotics worldwide in the treatment of Gram-negative bacterial infections. However, serious complications like nephrotoxicity and ototoxicity are dose-limiting factors in the use of aminoglycosides. A relatively large amount of the intravenously administered dose is accumulated in the kidney (about 10% of dose), whereas little distribution of aminoglycosides to other tissues is observed. Aminoglycosides are taken up in the epithelial cells of the renal proximal tubules and stay there for a long time, resulting in nephrotoxicity. Acidic phospholipids are considered as a binding site for aminoglycosides in the brush-border membrane of the proximal tubular cells. More recently, it has been reported that megalin, a giant endocytic receptor abundantly expressed at the apical membrane of renal proximal tubules, plays an important role in binding and endocytosis of aminoglycosides in the proximal tubular cells. The elucidation of the aminoglycoside-binding receptor would help design a strategy to prevent against aminoglycoside-induced nephrotoxicity. In this review, we summarize recent advances in the understandings of the molecular mechanisms responsible for renal accumulation of aminoglycosides, especially megalin-mediated endocytosis. In addition, approaches toward prevention of aminoglycoside-induced nephrotoxicity are discussed, based on the molecular mechanisms of the renal accumulation of aminoglycosides.
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Affiliation(s)
- Junya Nagai
- Department of Pharmaceutics and Therapeutics, Graduate School of Biomedical Sciences, Hiroshima University, Japan
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72
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Yun M, Keshvara L, Park CG, Zhang YM, Dickerson JB, Zheng J, Rock CO, Curran T, Park HW. Crystal structures of the Dab homology domains of mouse disabled 1 and 2. J Biol Chem 2003; 278:36572-81. [PMID: 12826668 DOI: 10.1074/jbc.m304384200] [Citation(s) in RCA: 101] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Disabled (Dab) 1 and 2 are mammalian homologues of Drosophila DAB. Dab1 is a key cytoplasmic mediator in Reelin signaling that controls cell positioning in the developing central nervous system, whereas Dab2 is an adapter protein that plays a role in endocytosis. DAB family proteins possess an amino-terminal DAB homology (DH) domain that is similar to the phosphotyrosine binding/phosphotyrosine interaction (PTB/PI) domain. We have solved the structures of the DH domains of Dab2 (Dab2-DH) and Dab1 (Dab1-DH) in three different ligand forms, ligand-free Dab2-DH, the binary complex of Dab2-DH with the Asn-Pro-X-Tyr (NPXY) peptide of amyloid precursor protein (APP), and the ternary complex of Dab1-DH with the APP peptide and inositol 1,4,5-trisphosphate (Ins-1,4,5-P3, the head group of phosphatidylinositol-4,5-diphosphate (PtdIns-4,5-P2)). The similarity of these structures suggests that the rigid Dab DH domain maintains two independent pockets for binding of the APP/lipoprotein receptors and phosphoinositides. Mutagenesis confirmed the structural determinants specific for the NPXY sequence and PtdIns-4,5-P2 binding. NMR spectroscopy confirmed that the DH domain binds to Ins-1,4,5-P3 independent of the NPXY peptides. These findings suggest that simultaneous interaction of the rigid DH domain with the NPXY sequence and PtdIns-4,5-P2 plays a role in the attachment of Dab proteins to the APP/lipoprotein receptors and phosphoinositide-rich membranes.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport/chemistry
- Adaptor Proteins, Vesicular Transport/metabolism
- Amyloid beta-Protein Precursor/chemistry
- Animals
- Apoptosis Regulatory Proteins
- Binding Sites
- Cell Membrane/metabolism
- Crystallography, X-Ray
- DNA, Complementary/metabolism
- Genes, Tumor Suppressor
- Inositol 1,4,5-Trisphosphate/chemistry
- Ligands
- Magnetic Resonance Spectroscopy
- Mice
- Models, Molecular
- Mutagenesis, Site-Directed
- Mutation
- Nerve Tissue Proteins/chemistry
- Nerve Tissue Proteins/metabolism
- Peptides/chemistry
- Phosphatidylinositol 4,5-Diphosphate/chemistry
- Phospholipids/chemistry
- Phosphorylation
- Protein Binding
- Protein Structure, Tertiary
- Proteins/chemistry
- Proteins/metabolism
- Reelin Protein
- Signal Transduction
- Tumor Suppressor Proteins
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Affiliation(s)
- Mikyung Yun
- Department of Structural Biology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105-2794, USA
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73
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McDonough AA, Biemesderfer D. Does membrane trafficking play a role in regulating the sodium/hydrogen exchanger isoform 3 in the proximal tubule? Curr Opin Nephrol Hypertens 2003; 12:533-41. [PMID: 12920402 DOI: 10.1097/00041552-200309000-00009] [Citation(s) in RCA: 36] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
PURPOSE OF REVIEW The proximal tubule sodium/hydrogen exchanger continuously reabsorbs the bulk of the filtered sodium, controlling salt delivery to the distal nephron which is critical for tubuloglomerular feedback autoregulation and for fine control of salt excretion in the distal nephron. This review focuses on recent studies of the mechanisms of regulation of sodium transport in the proximal tubule, and addresses whether results from studies in proximal tubule cell lines are applicable to the proximal tubule in situ. RECENT FINDINGS Recent in-vivo studies provided evidence that sodium/hydrogen exchanger isoform 3 can move into and out of the apical microvilli accompanied by parallel changes in renal sodium transport: the exchanger is retracted from the microvilli in response to hypertension, parathyroid hormone or dopamine treatment and moved into the microvilli in response to sympathetic nervous system stimulation, puromycin aminonucleoside induced nephritic syndrome, and insulin treatment. Studies in cultured opossum kidney proximal tubule cells provided evidence for clathrin coated vesicle mediated, dynamin dependent, cytoskeleton dependent internalization of sodium/hydrogen exchanger isoform 3 from the surface to an endosomal pool in response to dopamine or parathyroid hormone. In the intact proximal tubule there is evidence for a two-step internalization process: (1) from villi to the intermicrovillar cleft region and (2) to a higher density membrane pool that may be either below the microvilli or deep in intermicrovillar clefts. Recent studies have described a significant inactive pool of the exchanger in the intermicrovillar region in vivo that may serve as a storage and recruitable pool. SUMMARY The molecular mechanisms responsible for increasing or decreasing sodium transport in the proximal tubule appear to include redistribution of sodium/hydrogen exchanger isoform 3 to or from the microvillar region. Detailed studies in cultured proximal tubule cell lines provide evidence for endocytosis and exocytosis of the exchanger dependent on cytoskeleton and clathrin coated vesicles. In vivo, the apical membrane is differentiated into discrete villar and intermicrovillar membrane domains and the intermicrovillar domain, not observed in cultured cells, may serve as a recruitable storage pool for sodium/hydrogen exchanger isoform 3.
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Affiliation(s)
- Alicia A McDonough
- Department of Physiology, University of Southern California Keck School of Medicine, Los Angeles, California 90089-9142, USA.
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74
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Abstract
Actin is found at the cortex of the cell where endocytosis occurs, but does it play a role in this essential process? Recent studies on the unconventional myosin, myosin VI, an actin-based molecular motor, provide compelling evidence that this myosin and therefore actin is involved in two distinct steps of endocytosis in higher eukaryotes: the formation of clathrin-coated vesicles and the movement of nascent uncoated vesicles from the actin-rich cell periphery to the early endosome. Three distinct adapter proteins--GIPC, Dab2 and SAP97--that associate with the cargo-binding tail domain of myosin VI have been identified. These proteins may recruit myosin VI to its sites of action.
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Affiliation(s)
- Tama Hasson
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California at San Diego, 2129 Bonner Hall, MC 0368, 9500 Gilman Drive, La Jolla, CA 92093-0368, USA.
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75
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Homayouni R, Magdaleno S, Keshvara L, Rice DS, Curran T. Interaction of Disabled-1 and the GTPase activating protein Dab2IP in mouse brain. BRAIN RESEARCH. MOLECULAR BRAIN RESEARCH 2003; 115:121-9. [PMID: 12877983 DOI: 10.1016/s0169-328x(03)00176-1] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
Abstract
The Reelin signaling pathway controls neuronal positioning during mammalian brain development by binding to the very low density lipoprotein receptor and apolipoprotein E receptor-2, and signaling through the intracellular adapter protein Disabled-1 (Dab1). To identify new components in the Reelin signaling pathway, we used a yeast two-hybrid screen to select Dab1-interacting proteins. Here, we report the characterization of a new mouse Dab1-interacting protein that is orthologous to rat Dab2IP, a Ras-GTPase activating protein previously shown to bind to Dab2/DOC. The interaction of Dab1 and Dab2IP was confirmed in biochemical assays and by co-immunoprecipitation from brain lysates. The site of interaction between Dab1 and Dab2IP was narrowed to the Dab1-PTB domain and the NPxY motif in Dab2IP. The deduced amino acid sequence of mouse Dab2IP encompasses 1,208 residues containing several protein interaction motifs as well as a Ras-like GAP-related domain. Northern blot analysis revealed at least two isoforms of Dab2IP mRNA in the brain, both of which exhibited increased expression during development. In situ hybridization analyses indicated that Dab2IP mRNA is diffusely expressed throughout the developing and the adult brain. Using a polyclonal antiserum specific for Dab2IP, we observed protein expression in the soma and processes of neurons in a variety of brain structures, including the developing cerebral cortex. Our findings suggest that Dab2IP may function as a downstream effector in the Reelin signaling pathway that influences Ras signaling during brain development.
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Affiliation(s)
- Ramin Homayouni
- Department of Neurology, University of Tennessee, 855 Monroe Avenue, 416 Link Building, Memphis, TN 38163, USA.
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76
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Abstract
Disabled-2 (Dab2; also known as p96 and DOC-2) is a signal transduction protein that has been implicated in the control of cell growth. Dab2 is known to be a phosphoprotein, but little is known about the kinases that phosphorylate Dab2. We have found that Dab2 phosphorylation is markedly increased during the mitosis phase of the cell cycle. This phosphorylation is blocked by roscovitine, a selective inhibitor of cyclin-dependent kinases. Dab2 robustly coimmunoprecipitates from cells with the cyclin-dependent kinase cdc2, and purified cdc2 can phosphorylate purified Dab2 fusion proteins in vitro on multiple sites. Cellular phosphorylation of Dab2 by cdc2 promotes the association of Dab2 with Pin1, a peptidylprolyl isomerase that regulates the rate of Dab2 dephosphorylation. These findings reveal that Dab2 is differentially phosphorylated during the cell cycle by cdc2 and provide a potential feedback mechanism by which Dab2 inhibition of cell growth and proliferation may be regulated.
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Affiliation(s)
- Junqi He
- Department of Pharmacology, Rollins Research Center, Emory University School of Medicine, Atlanta, GA 30322, USA
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77
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Chen WF, Huang MH, Tzang CH, Yang M, Wong MS. Inhibitory actions of genistein in human breast cancer (MCF-7) cells. BIOCHIMICA ET BIOPHYSICA ACTA 2003; 1638:187-96. [PMID: 12853125 DOI: 10.1016/s0925-4439(03)00082-6] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
Abstract
Genistein, a natural isoflavanoid phytoestrogen, is thought to be the active ingredient in soy that possesses breast cancer preventive properties. The molecular mechanisms that are involved in its cancer preventive properties have not been completely understood. The present study is designed to investigate the mechanism involved in the inhibitory action of genistein in MCF-7 cells. Genistein at 50 and 100 microM significantly arrested the growth of MCF-7 cells at G2/M phase (P<0.05) and decreased at the proliferative S phase (P<0.05). Using cDNA microarray technology, genes differentially regulated by genistein were identified. In particular, as confirmed by reverse transcriptase-polymerase chain reaction (RT-PCR), genistein up-regulated heat shock protein 105 (HSP) mRNA and down-regulated mRNA expression of serum response factor (SRF), estrogen receptor (ER) alpha, disabled homolog 2 (DOC 2) and recombination activation gene 1 (RAG-1). Using real time RT-PCR, we have shown that HSP and SRF mRNA were both regulated by genistein in a time- and dose-dependent manner; however, it appears that only the effect of genistein on SRF mRNA, but not HSP mRNA expression, can be partially abolished by cotreatment with estrogen antagonist ICI 182,780. Western blotting analysis showed that the expressions of the ERalpha and SRF protein decreased significantly with genistein treatment (P<0.05). These results suggest that the inhibitory action of genistein on human breast cancer cells appears to be complex and is only partially mediated by the alteration of estrogen receptor-dependent pathways.
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Affiliation(s)
- Wen-Fang Chen
- Central Laboratory of the Institute of Molecular Technology for Drug Discovery and Synthesis, Department of Applied Biology and Chemical Technology, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, PR China
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78
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Stolt PC, Jeon H, Song HK, Herz J, Eck MJ, Blacklow SC. Origins of peptide selectivity and phosphoinositide binding revealed by structures of disabled-1 PTB domain complexes. Structure 2003; 11:569-79. [PMID: 12737822 DOI: 10.1016/s0969-2126(03)00068-6] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Formation of the mammalian six-layered neocortex depends on a signaling pathway that involves Reelin, the very low-density lipoprotein receptor, the apolipoprotein E receptor-2 (ApoER2), and the adaptor protein Disabled-1 (Dab1). The 1.5 A crystal structure of a complex between the Dab1 phosphotyrosine binding (PTB) domain and a 14-residue peptide from the ApoER2 tail explains the unusual preference of Dab1 for unphosphorylated tyrosine within the NPxY motif of the peptide. Crystals of the complex soaked with the phosphoinositide PI-4,5P(2) (PI) show that PI binds to conserved basic residues on the PTB domain opposite the peptide binding groove. This finding explains how the Dab1 PTB domain can simultaneously bind PI and the ApoER2 tail. Recruitment of the Dab1 PTB domain to PI-rich regions of the plasma membrane may facilitate association with the Reelin receptor cytoplasmic tails to transduce a critical positional cue to migrating neurons.
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Affiliation(s)
- Peggy C Stolt
- Department of Pathology, Brigham and Women's Hospital and Harvard Medical School, 75 Francis Street, Boston, MA 02115, USA
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79
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Tseng CP, Huang CL, Huang CH, Cheng JC, Stern A, Tseng CH, Chiu DTY. Disabled-2 small interfering RNA modulates cellular adhesive function and MAPK activity during megakaryocytic differentiation of K562 cells. FEBS Lett 2003; 541:21-7. [PMID: 12706813 DOI: 10.1016/s0014-5793(03)00281-3] [Citation(s) in RCA: 56] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Previous studies have shown that Disabled-2 (DAB2) is up-regulated during megakaryocytic differentiation of human K562 cells. To delineate the consequences of DAB2 induction, a DNA vector-based small interfering RNA (siRNA) was designed to intervene in DAB2 expression. We found that DAB2 siRNA specifically inhibited DAB2 induction, resulting in the modulation of cell-cell adhesion and mitogen-activated protein kinase (MAPK) phosphorylation. The morphological changes and beta3 integrin expression associated with megakaryocytic differentiation were not affected. Since the MAPK pathway has been shown to involve DAB2 induction [Tseng et al., Biochem. Biophys. Res. Commun. 285 (2001) 129-135], our results suggest a reciprocal regulation between DAB2 and MAPK in the differentiation of K562 cells. In addition, we have demonstrated for the first time that DAB2 siRNA is a valuable tool for unveiling the biological consequences of DAB2 expression.
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Affiliation(s)
- Ching-Ping Tseng
- Graduate Institute of Medical Biotechnology Chang Gung University, Kweishan, Taoyuan, Taiwan.
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80
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Zhou J, Scholes J, Hsieh JT. Characterization of a novel negative regulator (DOC-2/DAB2) of c-Src in normal prostatic epithelium and cancer. J Biol Chem 2003; 278:6936-41. [PMID: 12473651 DOI: 10.1074/jbc.m210628200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
DOC-2/DAB2 is a potent tumor suppressor in many cancer types including prostate cancer. In prostate cancer, expression of DOC-2/DAB2 can inhibit its growth. Our recent studies demonstrate that DOC-2/DAB2 can suppress both protein kinase C and peptide growth factor-elicited signal pathways via the Ras-mitogen-activated protein kinase pathway. In this study, we further showed that the proline-rich domain of DOC-2/DAB2 could also interact with proteins containing the Src homology 3 domain, such as Src and Fgr. The binding of c-Src to DOC-2/DAB2 was enhanced in cells treated with growth factor, and this interaction resulted in c-Src inactivation. The c-Src inactivation was evidenced by the decreased tyrosine 416 phosphorylation of c-Src and reduced downstream effector activation. It appears that DOC-2/DAB2 can bind to Src homology 3 domain of c-Src and maintain it in an inactive conformation. Thus, this study provides a new mechanism for modulating c-Src in prostatic epithelium and cancer.
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Affiliation(s)
- Jian Zhou
- Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9110, USA
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81
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Yang DH, Smith ER, Roland IH, Sheng Z, He J, Martin WD, Hamilton TC, Lambeth JD, Xu XX. Disabled-2 is essential for endodermal cell positioning and structure formation during mouse embryogenesis. Dev Biol 2002; 251:27-44. [PMID: 12413896 DOI: 10.1006/dbio.2002.0810] [Citation(s) in RCA: 135] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The signal transduction adapter protein Disabled-2 (Dab2) is one of the two mammalian orthologs of the Drosophila Disabled. The brain-specific Disabled-1 (Dab1) functions in positional organization of brain cells during development. Dab2 is widely distributed and is highly expressed in many epithelial cell types. The dab2 gene was interrupted by in-frame insertion of beta-galactosidase (LacZ) in embryonic stem cells and transgenic mice were produced. Dab2 expression was first observed in the primitive endoderm at E4.5, immediately following implantation. The homozygous Dab2-deficient mutant is embryonic lethal (earlier than E6.5) due to defective cell positioning and structure formation of the visceral endoderm. In E5.5 dab2 (-/-) conceptus, visceral endoderm-like cells are present in the deformed primitive egg cylinder; however, the visceral endoderm cells are not organized, the cells of the epiblast have not expanded, and the proamniotic cavity fails to form. Disorganization of the visceral endodermal layer is evident, as cells with positive visceral endoderm markers are scattered throughout the dab2 (-/-) conceptus. Only degenerated remains were observed at E6.5 for dab2 (-/-) embryos, and by E7.5, the defective embryos were completely reabsorbed. In blastocyst in vitro culture, initially cells with characteristics of endoderm, trophectoderm, and inner cell mass were observed in the outgrowth of the hatched dab2 (-/-) blastocysts. However, the dab2 (-/-) endodermal cells are much more dispersed and disorganized than those from wild-type blastocysts, the inner cell mass fails to expand, and the outgrowth degenerates by day 7. Thus, Dab2 is required for visceral endodermal cell organization during early mouse development. The absence of an organized visceral endoderm in Dab2-deficient conceptus leads to the growth failure of the inner cell mass. We suggest that Dab2 functions in a signal pathway to regulate endodermal cell organization using endocytosis of ligands from the blastocoel cavity as a positioning cue.
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Affiliation(s)
- Dong-Hua Yang
- Department of Medical Oncology, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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82
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Mishra SK, Keyel PA, Hawryluk MJ, Agostinelli NR, Watkins SC, Traub LM. Disabled-2 exhibits the properties of a cargo-selective endocytic clathrin adaptor. EMBO J 2002; 21:4915-26. [PMID: 12234931 PMCID: PMC126284 DOI: 10.1093/emboj/cdf487] [Citation(s) in RCA: 259] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Clathrin-coated pits at the cell surface select material for transportation into the cell interior. A major mode of cargo selection at the bud site is via the micro 2 subunit of the AP-2 adaptor complex, which recognizes tyrosine-based internalization signals. Other internalization motifs and signals, including phosphorylation and ubiquitylation, also tag certain proteins for incorporation into a coated vesicle, but the mechanism of selection is unclear. Disabled-2 (Dab2) recognizes the FXNPXY internalization motif in LDL-receptor family members via an N-terminal phosphotyrosine-binding (PTB) domain. Here, we show that in addition to binding AP-2, Dab2 also binds directly to phosphoinositides and to clathrin, assembling triskelia into regular polyhedral coats. The FXNPXY motif and phosphoinositides contact different regions of the PTB domain, but can stably anchor Dab2 to the membrane surface, while the distal AP-2 and clathrin-binding determinants regulate clathrin lattice assembly. We propose that Dab2 is a typical member of a growing family of cargo-specific adaptor proteins, including beta-arrestin, AP180, epsin, HIP1 and numb, which regulate clathrin-coat assembly at the plasma membrane by synchronizing cargo selection and lattice polymerization events.
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Affiliation(s)
- Sanjay K Mishra
- Department of Cell Biology and Physiology, University of Pittsburgh School of Medicine, 3500 Terrace Street, S325BST, Pittsburgh, PA 15261, USA
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83
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Kleeff J, Huang Y, Mok SC, Zimmermann A, Friess H, Büchler MW. Down-regulation of DOC-2 in colorectal cancer points to its role as a tumor suppressor in this malignancy. Dis Colon Rectum 2002; 45:1242-8. [PMID: 12352243 DOI: 10.1007/s10350-004-6399-2] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
PURPOSE Colorectal cancer is the second most common cause of cancer death and the fourth most prevalent carcinoma in the Western world. Loss of tumor-suppressor gene function in colon cancer leads to ineffective negative growth regulation that is normally exerted by growth-suppressing factors. DOC-2/hDAB2 is a newly identified candidate tumor-suppressor gene in ovarian cancer and choriocarcinoma. In these tumors it negatively influences mitogenic signal transduction of growth factors and blocks ras activity. In the present study we sought to determine the role of DOC-2 in colorectal cancer. METHODS DOC-2 expression was analyzed by Northern blot analysis, hybridization, and immunohistochemistry in 27 primary and metastatic colorectal cancers and in 15 normal colon tissues in correlation with clinicopathologic data. RESULTS Northern blot analysis demonstrated a decrease of DOC-2 messenger RNA levels in primary and metastatic colorectal cancers compared with normal controls. In normal colorectal tissues, DOC-2 immunoreactivity was strongly present on the surface columnar epithelial cells. In contrast, DOC-2 immunoreactivity was weak to moderate in the epithelium of colorectal cancers, and the intensity of the signals in colorectal cancer was greatly decreased compared with the normal colorectal tissues. In addition, DOC-2 immunoreactivity in lymph node and liver metastasis was weak to absent in the cancer cells and significantly decreased compared with their primary tumors. CONCLUSIONS The expression of DOC-2 is down-regulated in primary tumors and metastases of colorectal cancer, which suggests that DOC-2 functions as a tumor suppressor in this malignancy.
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Affiliation(s)
- Jörg Kleeff
- Department of General Surgery, University of Heidelberg, Germany
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84
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Yang DH, Smith ER, Cohen C, Wu H, Patriotis C, Godwin AK, Hamilton TC, Xu XX. Molecular events associated with dysplastic morphologic transformation and initiation of ovarian tumorigenicity. Cancer 2002; 94:2380-92. [PMID: 12015763 DOI: 10.1002/cncr.10497] [Citation(s) in RCA: 63] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Abstract
BACKGROUND Disabled-2 (Dab2), a candidate tumor suppressor of ovarian carcinoma, frequently (around 80%) loses its expression in ovarian tumors. Expression of exogenous Dab2 in tumor cell lines negatively regulates growth and suppresses the downstream signal of the Ras/mitogen activated protein kinase mitogenic pathway. The inactivation of Dab2 is believed to be an early event in ovarian tumorigenicity. METHODS The authors analyzed the correlation among expression of Dab2, presence of basement membrane (collagen IV and laminin), morphologic alteration of the surface epithelial cells, and expression of the mitotic index marker Mib-1 in 50 archived ovarian tumors by an immunohistochemical approach. The stainings of Dab2, Mib-1, collagen IV, and laminin in premalignant lesions bordering both normal and neoplastic ovarian surface epithelium from adjacent slides were analyzed in 50 ovarian tumors. RESULTS In these 50 ovarian tumors, the percentage of Mib-1 positive tumor cells distributed in a wide range, from 1% to 75%, and there has no strong correlation with the expression of Dab2. However, in the premalignant regions bordering tumor and normal ovarian surface epithelium, the loss of Dab2 expression closely correlated with the dysplastic morphologic transition and Mib-1 expression of the ovarian surface epithelial cells. In 20 foci in 12 out of the 50 tumors, a transition from normal to neoplastic morphology within a contiguous epithelium was observed, and in all cases the morphologic change correlated with the loss of Dab2 staining. In addition, the collagen and laminin staining of the basement membrane were absent or weakened in pre-malignant epithelium prior to loss of Dab2 expression in all these 20 cases. Nevertheless, collagen IV and laminin were detectable in established adenomas on the same tumor slides. CONCLUSIONS The loss of Dab2 is closely associated with the transition of ovarian surface epithelial cells to premalignant states and is likely involved in the initiation of ovarian tumorigenicity. Transient loss of collagen IV and laminin in the basement membrane of the premalignant epithelium and subsequent inactivation of Dab2 are common early events associated with tumorigenicity of the ovarian surface epithelium.
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Affiliation(s)
- Dong-Hua Yang
- Ovarian Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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85
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Morris SM, Arden SD, Roberts RC, Kendrick-Jones J, Cooper JA, Luzio JP, Buss F. Myosin VI binds to and localises with Dab2, potentially linking receptor-mediated endocytosis and the actin cytoskeleton. Traffic 2002; 3:331-41. [PMID: 11967127 DOI: 10.1034/j.1600-0854.2002.30503.x] [Citation(s) in RCA: 209] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
Myosin VI, an actin-based motor protein, and Disabled 2 (Dab2), a molecule involved in endocytosis and cell signalling, have been found to bind together using yeast and mammalian two-hybrid screens. In polarised epithelial cells, myosin VI is known to be associated with apical clathrin-coated vesicles and is believed to move them towards the minus end of actin filaments, away from the plasma membrane and into the cell. Dab2 belongs to a group of signal transduction proteins that bind in vitro to the FXNPXY sequence found in the cytosolic tails of members of the low-density lipoprotein receptor family. The central region of Dab2, containing two DPF motifs, binds to the clathrin adaptor protein AP-2, whereas a C-terminal region contains the binding site for myosin VI. This site is conserved in Dab1, the neuronal counterpart of Dab2. The interaction between Dab2 and myosin VI was confirmed by in vitro binding assays and coimmunoprecipitation and by their colocalisation in clathrin-coated pits/vesicles concentrated at the apical domain of polarised cells. These results suggest that the myosin VI-Dab2 interaction may be one link between the actin cytoskeleton and receptors undergoing endocytosis.
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Affiliation(s)
- Shelli M Morris
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109-1024, USA
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86
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Wang Z, Tseng CP, Pong RC, Chen H, McConnell JD, Navone N, Hsieh JT. The mechanism of growth-inhibitory effect of DOC-2/DAB2 in prostate cancer. Characterization of a novel GTPase-activating protein associated with N-terminal domain of DOC-2/DAB2. J Biol Chem 2002; 277:12622-31. [PMID: 11812785 DOI: 10.1074/jbc.m110568200] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
DOC-2/DAB2 is a member of the disable gene family with tumor-inhibitory activity. Its down-regulation is associated with several neoplasms, and serine phosphorylation of its N terminus modulates DOC-2/DAB2's inhibitory effect on AP-1 transcriptional activity. We describe the cloning of DIP1/2, a novel gene that interacts with the N-terminal domain of DOC-2/DAB2. DIP1/2 is a novel GTPase-activating protein containing a Ras GTPase-activating protein homology domain (N terminus) and two other unique domains (i.e. 10 proline repeats and leucine zipper). Interaction between DOC-2/DAB2 and DIP1/2 is detected in normal tissues such as the brain and prostate. Altered expression of these two proteins is often detected in prostate cancer cells. Indeed, the presence of DIP1/2 effectively blocks mitogen-induced gene expression and inhibits the growth of prostate cancer. Thus, DOC-2/DAB2 and DIP1/2 appear to represent a unique negative regulatory complex that maintains cell homeostasis.
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Affiliation(s)
- Zhi Wang
- Department of Urology, University of Texas Southwestern Medical Center at Dallas, 5323 Harry Hines Blvd., Dallas, TX 75390-9110, USA
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87
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Morris SM, Tallquist MD, Rock CO, Cooper JA. Dual roles for the Dab2 adaptor protein in embryonic development and kidney transport. EMBO J 2002; 21:1555-64. [PMID: 11927540 PMCID: PMC125955 DOI: 10.1093/emboj/21.7.1555] [Citation(s) in RCA: 174] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
The Disabled-2 (Dab2) gene has been proposed to act as a tumor suppressor. Cell culture studies have implicated Dab2 in signal transduction by mitogens, TGFbeta and endocytosis of lipoprotein receptors. To identify in vivo functions of Dab2, targeted mutations were made in the mouse. In the absence of Dab2, embryos arrest prior to gastrulation with a phenotype reminiscent of those caused by deletion of some TGFbeta signal transduction molecules involved in Nodal signaling. Dab2 is expressed in the extra-embryonic visceral endoderm but not in the epiblast. Dab2 could be conditionally deleted from the embryo without affecting normal development, showing that Dab2 is required in the visceral endoderm but dispensable in the embryo proper. Conditionally mutant Dab2(-/-) mice are overtly normal, but have reduced clathrin-coated pits in kidney proximal tubule cells and excrete specific plasma proteins in the urine, consistent with reduced transport by a lipoprotein receptor, megalin/gp330, in the proximal tubule. This evidence indicates that Dab2 is pleiotropic and regulates both visceral endoderm function and lipoprotein receptor trafficking in vivo.
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Affiliation(s)
- Shelli M. Morris
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109 and
St Jude Children’s Research Hospital, Protein Science Division, Department of Infectious Diseases, Memphis, TN 38101, USA Present address: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA Corresponding author e-mail:
| | - Michelle D. Tallquist
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109 and
St Jude Children’s Research Hospital, Protein Science Division, Department of Infectious Diseases, Memphis, TN 38101, USA Present address: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA Corresponding author e-mail:
| | - Charles O. Rock
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109 and
St Jude Children’s Research Hospital, Protein Science Division, Department of Infectious Diseases, Memphis, TN 38101, USA Present address: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA Corresponding author e-mail:
| | - Jonathan A. Cooper
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109 and
St Jude Children’s Research Hospital, Protein Science Division, Department of Infectious Diseases, Memphis, TN 38101, USA Present address: Department of Molecular Biology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA Corresponding author e-mail:
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88
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Rosenbauer F, Kallies A, Scheller M, Knobeloch KP, Rock CO, Schwieger M, Stocking C, Horak I. Disabled-2 is transcriptionally regulated by ICSBP and augments macrophage spreading and adhesion. EMBO J 2002; 21:211-20. [PMID: 11823414 PMCID: PMC125345 DOI: 10.1093/emboj/21.3.211] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Mice lacking transcription factor interferon consensus sequence binding protein (ICSBP) develop a syndrome similar to human chronic myeloid leukemia and are immunodeficient. In order to define the molecular mechanisms responsible for the cellular defects of ICSBP(-/-) mice, we used bone marrow-derived macrophages (BMM) to identify genes deregulated in the absence of ICSBP. Here, we report that disabled-2 (Dab2), a signal phosphoprotein, is transcriptionally up-regulated and accumulates in the cytoskeleton/membrane fraction of ICSBP(-/-) BMM. Moreover, our results revealed Dab2 as a novel IFN-gamma-response gene. Both ICSBP and the Ets-transcription factor PU.1 bind to the Dab2 promoter, whereby ICSBP represses PU.1-induced Dab2 promoter transactivation in vitro. Notably, repression of Dab2 expression by ICSBP is also found in myeloid progenitors. Overexpression of Dab2 leads to accelerated cell adhesion and spreading, accompanied by enhanced actin fiber formation. Furthermore, cell adhesion induces transient Dab2 phosphorylation and its translocation to the cytoskeletal/membrane fraction. Our results identify a novel role of Dab2 as an inducer of cell adhesion and spreading, and strongly suggest that the up-regulation of Dab2 contributes to the hematopoietic defect seen in ICSBP(-/-) mice.
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Affiliation(s)
- Frank Rosenbauer
- Department of Molecular Genetics, Institute of Molecular Pharmacology, and Benjamin Franklin Medical Center, Free University of Berlin, Krahmerstrasse 6, D-12207 Berlin, Germany,
Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA and Heinrich-Pette-Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany Present address: Hematology/Oncology Division, Harvard Institutes of Medicine, Boston, MA 02155, USA Present address: GenPat77 Pharmacogenetics, D-10115 Berlin, Germany Corresponding author e-mail: F.Rosenbauer and A.Kallies contributed equally to this work
| | | | | | - Klaus-Peter Knobeloch
- Department of Molecular Genetics, Institute of Molecular Pharmacology, and Benjamin Franklin Medical Center, Free University of Berlin, Krahmerstrasse 6, D-12207 Berlin, Germany,
Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA and Heinrich-Pette-Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany Present address: Hematology/Oncology Division, Harvard Institutes of Medicine, Boston, MA 02155, USA Present address: GenPat77 Pharmacogenetics, D-10115 Berlin, Germany Corresponding author e-mail: F.Rosenbauer and A.Kallies contributed equally to this work
| | - Charles O. Rock
- Department of Molecular Genetics, Institute of Molecular Pharmacology, and Benjamin Franklin Medical Center, Free University of Berlin, Krahmerstrasse 6, D-12207 Berlin, Germany,
Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA and Heinrich-Pette-Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany Present address: Hematology/Oncology Division, Harvard Institutes of Medicine, Boston, MA 02155, USA Present address: GenPat77 Pharmacogenetics, D-10115 Berlin, Germany Corresponding author e-mail: F.Rosenbauer and A.Kallies contributed equally to this work
| | - Maike Schwieger
- Department of Molecular Genetics, Institute of Molecular Pharmacology, and Benjamin Franklin Medical Center, Free University of Berlin, Krahmerstrasse 6, D-12207 Berlin, Germany,
Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA and Heinrich-Pette-Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany Present address: Hematology/Oncology Division, Harvard Institutes of Medicine, Boston, MA 02155, USA Present address: GenPat77 Pharmacogenetics, D-10115 Berlin, Germany Corresponding author e-mail: F.Rosenbauer and A.Kallies contributed equally to this work
| | - Carol Stocking
- Department of Molecular Genetics, Institute of Molecular Pharmacology, and Benjamin Franklin Medical Center, Free University of Berlin, Krahmerstrasse 6, D-12207 Berlin, Germany,
Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA and Heinrich-Pette-Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany Present address: Hematology/Oncology Division, Harvard Institutes of Medicine, Boston, MA 02155, USA Present address: GenPat77 Pharmacogenetics, D-10115 Berlin, Germany Corresponding author e-mail: F.Rosenbauer and A.Kallies contributed equally to this work
| | - Ivan Horak
- Department of Molecular Genetics, Institute of Molecular Pharmacology, and Benjamin Franklin Medical Center, Free University of Berlin, Krahmerstrasse 6, D-12207 Berlin, Germany,
Department of Infectious Diseases, St Jude Children’s Research Hospital, Memphis, TN 38105, USA and Heinrich-Pette-Institute for Experimental Virology and Immunology, D-20251 Hamburg, Germany Present address: Hematology/Oncology Division, Harvard Institutes of Medicine, Boston, MA 02155, USA Present address: GenPat77 Pharmacogenetics, D-10115 Berlin, Germany Corresponding author e-mail: F.Rosenbauer and A.Kallies contributed equally to this work
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89
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Herrick TM, Cooper JA. A hypomorphic allele of dab1 reveals regional differences in reelin-Dab1 signaling during brain development. Development 2002; 129:787-96. [PMID: 11830577 DOI: 10.1242/dev.129.3.787] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The disabled 1 (Dab1) p80 protein is essential for reelin signaling during brain development. p80 has an N-terminal domain for association with reelin receptors, followed by reelin-dependent tyrosine phosphorylation sites and about 310 C-terminal residues of unknown function. We have generated mutant mice that express only a natural splice form of Dab1, p45, that lacks the C-terminal region of p80. The normal development of these mice implies that the receptor-binding region and tyrosine phosphorylation sites of p80 are sufficient for reelin signaling. However, a single copy of the truncated gene does not support normal development of the neocortex and hippocampus. The CA1 region of the hippocampus is split into two well-organized layers, while the marginal zone of the neocortex is invaded by late-born cortical plate neurons. The haploinsufficiency of the p45 allele of Dab1 implies that the C terminus of p80 affects the strength of reelin-Dab1 signaling, yet there is no apparent change in reelin-dependent tyrosine phosphorylation of p45 relative to p80. Therefore, we suggest that the C-terminal region of Dab1 p80 is involved in signaling to downstream effector molecules. Furthermore, the presence of late-born cortical plate neurons in the marginal zone reveals a requirement for reelin-Dab1 signaling in late-born cortical plate neurons, and helps distinguish models for the cortical inversion in the reeler mutant mouse.
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Affiliation(s)
- Tara M Herrick
- Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue N, Seattle, WA 98109, USA
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90
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Smith ER, Capo-chichi CD, He J, Smedberg JL, Yang DH, Prowse AH, Godwin AK, Hamilton TC, Xu XX. Disabled-2 mediates c-Fos suppression and the cell growth regulatory activity of retinoic acid in embryonic carcinoma cells. J Biol Chem 2001; 276:47303-10. [PMID: 11577091 DOI: 10.1074/jbc.m106158200] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
F9 embryonic stem cell-like teratocarcinoma cells are widely used to study early embryonic development and cell differentiation. The cells can be induced by retinoic acid to undergo endodermal differentiation. The retinoic acid-induced differentiation accompanies cell growth suppression, and thus, F9 cells are also often used as a model for analysis of retinoic acid biological activity. We have recently shown that MAPK activation and c-Fos expression are uncoupled in F9 cells upon retinoic acid-induced endodermal differentiation. The expression of the candidate tumor suppressor Disabled-2 is induced and correlates with cell growth suppression in F9 cells. We were not able to establish stable Disabled-2 expression by cDNA transfection in F9 cells without induction of spontaneous cell differentiation. Transient transfection of Dab2 by adenoviral vector nevertheless suppresses Elk-1 phosphorylation, c-Fos expression, and cell growth. In PA-1, another teratocarcinoma cell line of human origin that has no or very low levels of Disabled-2, retinoic acid fails to induce Disabled-2, correlating with a lack of growth suppression, although PA-1 is responsive to retinoic acid in morphological change. Transfection and expression of Disabled-2 in PA-1 cells mimic the effects of retinoic acid on growth suppression; the Disabled-2-expressing cells reach a much lower saturation density, and serum-stimulated c-Fos expression is greatly suppressed and disassociated from MAPK activation. Thus, Dab2 is one of the principal genes induced by retinoic acid involved in cell growth suppression, and expression of Dab2 alone is sufficient for uncoupling of MAPK activation and c-Fos expression. Resistance to retinoic acid regulation in PA-1 cells likely results from defects in retinoic acid up-regulation of Dab2 expression.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport
- Adenoviridae/genetics
- Animals
- Apoptosis Regulatory Proteins
- Blotting, Northern
- Blotting, Western
- Carcinoma, Embryonal/metabolism
- Cell Differentiation
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Enzyme Activation
- Flow Cytometry
- Genes, Tumor Suppressor
- Humans
- MAP Kinase Signaling System
- Mice
- Models, Biological
- Proteins/metabolism
- Proto-Oncogene Proteins c-fos/metabolism
- Signal Transduction
- Time Factors
- Transfection
- Tretinoin/chemistry
- Tretinoin/metabolism
- Tretinoin/pharmacology
- Tumor Cells, Cultured
- Tumor Suppressor Proteins
- Up-Regulation
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Affiliation(s)
- E R Smith
- Ovarian Cancer Program, Fox Chase Cancer Center, 7701 Burholme Ave., Philadelphia, PA 19111, USA
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91
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Homayouni R, Rice DS, Curran T. Disabled-1 interacts with a novel developmentally regulated protocadherin. Biochem Biophys Res Commun 2001; 289:539-47. [PMID: 11716507 DOI: 10.1006/bbrc.2001.5998] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Disabled-1 (Dab1) is an intracellular adapter protein that mediates the effect of Reelin on neuronal migration and cell positioning during mammalian brain development. To identify components of the Reelin-Dab1 signaling pathway, we searched for proteins that interact with Dab1 using a yeast two-hybrid strategy. We found that the Dab1 phosphotyrosine binding (PTB) domain interacts with a novel protocadherin, orthologous to human protocadherin 18. Mouse Pcdh18 (mPcdh18), which consists of four exons similar to other protocadherin family members, maps to chromosome 3. The deduced amino acid sequence of mPcdh18 contains six extracellular cadherin motifs, a single transmembrane region, and a large intracellular domain. The site of Dab1 interaction was localized to the C-terminal 243 residues of mPcdh18. Expression analyses revealed that mPcdh18 is present in a variety of tissues in the embryo, but in adult mice it is primarily expressed in lung and kidney. In embryonic brain, mPcdh18 expression is temporally and spatially regulated. Our results indicate that mPcdh18 participates in signaling pathways involving PTB-containing proteins and suggest that it may play a role during brain development.
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Affiliation(s)
- R Homayouni
- Department of Developmental Neurobiology, St. Jude Children's Research Hospital, Memphis, Tennessee 38105, USA
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92
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Segarini PR, Nesbitt JE, Li D, Hays LG, Yates JR, Carmichael DF. The low density lipoprotein receptor-related protein/alpha2-macroglobulin receptor is a receptor for connective tissue growth factor. J Biol Chem 2001; 276:40659-67. [PMID: 11518710 DOI: 10.1074/jbc.m105180200] [Citation(s) in RCA: 158] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Connective tissue growth factor (CTGF) expression is regulated by transforming growth factor-beta (TGF-beta) and strong up-regulation occurs during wound healing; in situ hybridization data indicate that there are high levels of CTGF expression in fibrotic lesions. Recently the binding parameters of CTGF to both high and lower affinity cell surface binding components have been characterized. Affinity cross-linking and SDS-polyacrylamide gel electrophoresis analysis demonstrated the binding of CTGF to a cell surface protein with a mass of approximately 620 kDa. We report here the purification of this protein by affinity chromatography on CTGF coupled to Sepharose and sequence information obtained by mass spectroscopy. The binding protein was identified as the multiligand receptor, low density lipoprotein receptor-related protein/alpha2-macroglobulin receptor (LRP). The identification of LRP as a receptor for CTGF was validated by several studies: 1) binding competition with many ligands that bind to LRP, including receptor-associated protein; 2) immunoprecipitation of CTGF-receptor complex with LRP antibodies; and 3) cells that are genetically deficient for LRP were unable to bind CTGF. Last, CTGF is rapidly internalized and degraded and this process is LRP-dependent. In summary, our data indicate that LRP is a receptor for CTGF, and may play an important role in mediating CTGF biology.
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Affiliation(s)
- P R Segarini
- FibroGen, Inc., South San Francisco, California 94080, USA
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93
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Wang SC, Makino K, Xia W, Kim JS, Im SA, Peng H, Mok SC, Singletary SE, Hung MC. DOC-2/hDab-2 inhibits ILK activity and induces anoikis in breast cancer cells through an Akt-independent pathway. Oncogene 2001; 20:6960-4. [PMID: 11687976 DOI: 10.1038/sj.onc.1204873] [Citation(s) in RCA: 42] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2001] [Revised: 07/31/2001] [Accepted: 07/31/2001] [Indexed: 01/13/2023]
Abstract
DOC-2/hDab-2 was identified due to the loss of its expression in primary ovarian cancer cells. It is believed that loss of DOC-2/hDab-2 expression is one of the early events of ovarian malignancy. These results suggest a function of DOC-2/hDab-2 as a tumor suppressor. However, it is not clear how DOC-2/hDab-2 negatively regulates cancer cell growth. In this report, we demonstrate that DOC-2/hDab-2 expression in breast cancer cells resulted in sensitivity to suspension-induced cell death (anoikis). This event was associated with the down-regulation of the integrin-linked kinase (ILK) activity. Since ILK is a key factor in regulating the cellular signaling in responding to the extracellular signals through adhesion molecules like integrins, our results indicate that DOC-2/hDab-2 may prevent tumor growth and invasion by modulating the anti-apoptotic ILK pathway.
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Affiliation(s)
- S C Wang
- Department of Molecular and Cellular Oncology, The University of Texas, M.D. Anderson Cancer Center, Houston, Texas 77030, USA
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94
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Smith ER, Smedberg JL, Rula ME, Hamilton TC, Xu XX. Disassociation of MAPK activation and c-Fos expression in F9 embryonic carcinoma cells following retinoic acid-induced endoderm differentiation. J Biol Chem 2001; 276:32094-100. [PMID: 11402055 DOI: 10.1074/jbc.m105009200] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Retinoic acid induces cell differentiation and suppresses cell growth in a wide spectrum of cell lines, and down-regulation of activator protein-1 activity by retinoic acid contributes to these effects. In embryonic stem cell-like F9 teratocarcinoma cells, which are widely used to study retinoic acid actions on gene regulation and early embryonic differentiation, retinoic acid treatment for 4 days resulted in suppression of cell growth and differentiation into primitive and then visceral endoderm-like cells, accompanied by a suppression of serum-induced c-Fos expression. The MAPK (ERK) pathway was involved in mitogenic signaling in F9 cells stimulated with serum. Surprisingly, although c-Fos expression was reduced, the MAPK activity was not decreased by retinoic acid treatment. We found that retinoic acid treatment inhibited the phosphorylation of Elk-1, a target of activated MAPK required for c-Fos transcription. In F9 cells, the MAPK/MEK inhibitor PD98059 suppressed Elk-1 phosphorylation and c-Fos expression, indicating that MAPK activity is required for Elk-1 phosphorylation/activation. Phosphoprotein phosphatase 2B (calcineurin), the major phosphatase for activated Elk-1, is not the target in the disassociation of MAPK activation and c-Fos expression since its inhibition by cyclosporin A or activation by ionomycin had no significant effects on serum-stimulated c-Fos expression and Elk-1 phosphorylation. Thus, we conclude that retinoic acid treatment to induce F9 cell differentiation uncouples Ras/MAPK activation from c-Fos expression by reduction of Elk-1 phosphorylation through a mechanism not involving the activation of phosphoprotein phosphatase 2B.
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Affiliation(s)
- E R Smith
- Ovarian Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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95
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Sheng Z, Smith ER, He J, Tuppen JA, Martin WD, Dong FB, Xu XX. Chromosomal location of murine disabled-2 gene and structural comparison with its human ortholog. Gene 2001; 268:31-9. [PMID: 11368898 DOI: 10.1016/s0378-1119(01)00401-2] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Disabled-2 (Dab2) is one of the two mammalian orthologs of the Drosophila Disabled. The three spliced forms, p96, p93, and p67 of murine Dab2 cDNAs were first isolated as phosphoproteins functioning in the macrophage CSF-1 signal transduction pathway. Subsequently, the involvement of Dab2 in ovarian cancer development has been investigated: Dab2 expression is lost or greatly diminished in breast and ovarian cancers, and gene deletions have been found. Regulation of Disabled-2 expression is also found to be important in development and physiological functions. Structural information of the murine Dab2 gene is essential for studies of transcription regulation and gene function in mouse models. In this study, the mouse Dab2 gene coding sequence was identified and sequenced from three lambda phage clones containing the gene. Two BAC clones of mouse genomic DNA were also used to identify the sequences of the non-coding first exon and promoter. The first exon is separated from the second exon by a large (15 kb) intron. The mouse gene is about 40 kb in size and consists of 15 exons, producing a 3.6 kb message. The translation initiation site resides in the middle of the second exon. The mouse Dab2 gene structure is very similar to that of its human ortholog in exon/intron sizes and promoter sequences. The chromosomal localization of mouse Dab2 was mapped by FISH to chromosome 15A2, a site of syntax with the human 5p12 where human Dab2 gene resides. The information on the mouse Dab2 gene structure and promoter will be invaluable in studies of the involvement of Dab2 gene in cancer, expression, physiological function, and development in mouse models.
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Affiliation(s)
- Z Sheng
- Department of Biochemistry, Emory University School of Medicine, Atlanta, GA 30322, USA
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96
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Hocevar BA, Smine A, Xu XX, Howe PH. The adaptor molecule Disabled-2 links the transforming growth factor beta receptors to the Smad pathway. EMBO J 2001; 20:2789-801. [PMID: 11387212 PMCID: PMC125498 DOI: 10.1093/emboj/20.11.2789] [Citation(s) in RCA: 195] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Using a genetic complementation approach we have identified disabled-2 (Dab2), a structural homolog of the Dab1 adaptor molecule, as a critical link between the transforming growth factor beta (TGFbeta) receptors and the Smad family of proteins. Expression of wild-type Dab2 in a TGFbeta-signaling mutant restores TGFbeta-mediated Smad2 phosphorylation, Smad translocation to the nucleus and Smad-dependent transcriptional responses. TGFbeta stimulation triggers a transient increase in association of Dab2 with Smad2 and Smad3, which is mediated by a direct interaction between the N-terminal phosphotyrosine binding domain of Dab2 and the MH2 domain of Smad2. Dab2 associates with both the type I and type II TGFbeta receptors in vivo, suggesting that Dab2 is part of a multiprotein signaling complex. Together, these data indicate that Dab2 is an essential component of the TGFbeta signaling pathway, aiding in transmission of TGFbeta signaling from the TGFbeta receptors to the Smad family of transcriptional activators.
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Affiliation(s)
| | | | - Xiang-Xi Xu
- Department of Cell Biology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195 and
Department of Biochemistry and Winship Cancer Center, Emory University School of Medicine, Atlanta, GA 30322, USA Corresponding author e-mail:
| | - Philip H. Howe
- Department of Cell Biology, The Lerner Research Institute, Cleveland Clinic Foundation, Cleveland, OH 44195 and
Department of Biochemistry and Winship Cancer Center, Emory University School of Medicine, Atlanta, GA 30322, USA Corresponding author e-mail:
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97
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Huang Y, Friess H, Kleeff J, Esposito I, Zhu Z, Liu S, Mok SC, Zimmermann A, Büchler MW. Doc-2/hDab2 expression is up-regulated in primary pancreatic cancer but reduced in metastasis. J Transl Med 2001; 81:863-73. [PMID: 11406647 DOI: 10.1038/labinvest.3780295] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
SUMMARY DOC-2/hDab2 (DOC-2) has tumor suppressive functions in ovarian cancer and choriocarcinoma. In these tumors, it negatively influences mitogenic signal transduction of growth factors and blocks ras activity. Pancreatic cancer exhibits a high frequency of K-ras gene mutations; however, it is not known whether DOC-2 expression is altered in these tumors. Therefore, we investigated DOC-2 expression in 22 pancreatic adenocarcinomas and in 6 pancreatic cancer cell lines. Findings in human tumors were compared with normal controls and correlated with clinicopathological data. Additionally, the influence of K-ras on DOC-2 transcription was investigated. Northern blot and Western blot analyses both demonstrated an increase of DOC-2 mRNA and protein levels in primary pancreatic cancers in comparison with normal controls. In situ hybridization showed DOC-2 mRNA expression in the majority of cancer cells of primary tumors, as well as in chronic pancreatitis-like lesions surrounding the cancer mass. Immunohistochemistry mirrored the in situ hybridization findings. In contrast, levels of expression of DOC-2 in lymph node metastases were markedly decreased in comparison with levels in primary tumors. In addition, in 5 metastatic pancreatic cancer cell lines, DOC-2 mRNA and protein levels were low, whereas quantitative RT-PCR demonstrated relatively higher levels in a nonmetastatic pancreatic cancer cell line. In conclusion, DOC-2 is overexpressed in primary pancreatic adenocarcinoma but down-regulated in metastatic disease, suggesting a tumor suppressor function of DOC-2 in the late steps of pancreatic carcinogenesis.
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Affiliation(s)
- Y Huang
- Department of Visceral and Transplantation Surgery, University of Bern, Inselspital, Bern, Switzerland.
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98
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Zhou J, Hsieh JT. The inhibitory role of DOC-2/DAB2 in growth factor receptor-mediated signal cascade. DOC-2/DAB2-mediated inhibition of ERK phosphorylation via binding to Grb2. J Biol Chem 2001; 276:27793-8. [PMID: 11371563 DOI: 10.1074/jbc.m102803200] [Citation(s) in RCA: 86] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
DOC-2/DAB2 (differentially expressed in ovarian carcinoma-2/disabled 2) appears to be a potential tumor suppressor gene with a growth inhibitory effect on several cancer types. Previously, we have shown that DOC-2/DAB2 suppresses protein kinase C-induced AP-1 activation, which is modulated by serine 24 phosphorylation in the N terminus of DOC-2/DAB2. However, the functional impact of the C terminus of DOC-2/DAB2, containing three proline-rich domains, has not been explored. In this study, we examined this functional role in modulating signaling mediated by peptide growth factor receptor tyrosine kinase, particularly because it involves the interaction with Grb2. Using sequence-specific peptides, we found that the second proline-rich domain of DOC-2/DAB2 is the key binding site to Grb2 in the presence of growth factors. Such elevated binding interrupts the binding between SOS and Grb2, which consequently suppresses downstream ERK phosphorylation. Reduced ERK phosphorylation was restored when the binding between DOC-2/DAB2 and Grb2 was interrupted by a specific peptide or by increasing the expression of Grb2. Furthermore, the C terminus of the DOC-2/DAB2 construct can inhibit the AP-1 activity elicited by growth factors. We conclude that DOC-2/DAB2, a potent negative regulator, can suppress ERK activation by interrupting the binding between Grb2 and SOS that is elicited by peptide growth factors. This study further illustrates that DOC-2/DAB2 has multiple effects on the RAS-mediated signal cascades active in cancer cells.
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MESH Headings
- Adaptor Proteins, Signal Transducing
- Adaptor Proteins, Vesicular Transport
- Animals
- Apoptosis Regulatory Proteins
- Binding Sites
- COS Cells
- DNA, Complementary/metabolism
- Dose-Response Relationship, Drug
- Enzyme Activation
- Epidermal Growth Factor/metabolism
- GRB2 Adaptor Protein
- Genes, Reporter
- Genes, Tumor Suppressor
- Luciferases/metabolism
- Mitogen-Activated Protein Kinases
- PC12 Cells
- Peptides/chemistry
- Phosphorylation
- Plasmids/metabolism
- Precipitin Tests
- Proline/chemistry
- Proline/metabolism
- Protein Binding
- Protein Kinase C/metabolism
- Protein Structure, Tertiary
- Proteins/metabolism
- Rats
- Receptors, Growth Factor/metabolism
- Recombinant Proteins/metabolism
- Signal Transduction
- Son of Sevenless Protein, Drosophila/metabolism
- Time Factors
- Transfection
- Tumor Cells, Cultured
- Tumor Suppressor Proteins
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Affiliation(s)
- J Zhou
- Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9110, USA
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99
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He J, Smith ER, Xu XX. Disabled-2 exerts its tumor suppressor activity by uncoupling c-Fos expression and MAP kinase activation. J Biol Chem 2001; 276:26814-8. [PMID: 11359772 DOI: 10.1074/jbc.m101820200] [Citation(s) in RCA: 39] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Disabled-2 (Dab2) is a putative tumor suppressor in breast and ovarian cancers. Its expression is lost in a majority of tumors, and homozygous deletions have been identified in a small percentage of tumors. Dab2 expression is absent or very low in the majority of breast and ovarian cancer cell lines, including MCF-7 and SK-Br-3 breast cancer cells. Transfection and expression of Dab2 in MCF-7 and SK-Br-3 cells suppress tumorigenicity. The cells reach a much lower saturation density and have reduced ability to form colonies on agar plates. In examining the signal transduction pathway of Dab2-transfected cells, we found that serum-stimulated c-Fos expression was greatly suppressed; however, the effects of Dab2 on MAPK family kinases were not as consistent. In MCF-7 and SK-Br-3 cells, although c-Fos expression was suppressed, the Erk1/2, JNK, and p38(MAPK) activities were unchanged or even increased. Serum-stimulated c-Fos expression is dependent on MAPK/Erk activity because the MEK inhibitor PD98059 suppresses Erk activity and c-Fos expression. Therefore, Dab2 appears to uncouple MAPK activation and c-fos transcription. Thus, we conclude that Dab2 re-expression suppresses tumorigenicity by reducing c-Fos expression at a site downstream of the activation of MAPK family kinases. Because Dab2 is frequently lost in cancer, the uncoupling of MAPK activation and c-Fos expression may be a favored target for inactivation in tumorigenicity.
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Affiliation(s)
- J He
- Ovarian Cancer Program, Fox Chase Cancer Center, Philadelphia, Pennsylvania 19111, USA
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100
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Abstract
Disabled-2 (Dab2) is a widely expressed relative of Disabled-1, a neuron-specific signal-transduction protein that binds to and receives signals from members of the low-density lipoprotein receptor (LDLR) family. Members of the LDLR family internalize through clathrin-coated pits and vesicles to endosomes, from where they return to the cell surface through the secretory pathway. In this study, we show that the Dab2 phosphotyrosine-binding domain binds peptides containing the sequence FXN-PXY. This core sequence is found in the intracellular domains of LDLR family members and is important for receptor internalization. Dab2 transiently colocalizes with the LDLR in clathrin-coated pits, but is absent from endosomes and lysosomes. Dab2 is alternatively spliced and its localization depends on a region of the protein that contains two DPF motifs that are present in the p96 Dab2 protein and absent in the p67 splice variant. This region is sufficient to confer Dab2 binding to the alpha-adaptin subunit of the clathrin adaptor protein, AP-2. Overexpression of p96 but not of p67 Dab2 disrupts the localization of AP-2. These findings suggest that in addition to previously reported signal-transduction functions, Dab2 could also act as an adaptor protein that may regulate protein trafficking.
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Affiliation(s)
- S M Morris
- Fred Hutchinson Cancer Research Center, Division of Basic Sciences, 1100 Fairview Avenue North, Seattle, WA 98109-1024, USA
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