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Byerly CD, Zhu B, Warwick PA, Patterson LL, Pittner NA, McBride JW. Ehrlichia chaffeensis TRP120 ubiquitinates tumor suppressor APC to modulate Hippo and Wnt signaling. Front Cell Dev Biol 2024; 12:1327418. [PMID: 38562145 PMCID: PMC10982408 DOI: 10.3389/fcell.2024.1327418] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 03/05/2024] [Indexed: 04/04/2024] Open
Abstract
Ehrlichia chaffeensis: TRP120 is a multifunctional effector that acts as a ligand mimic to activate evolutionary conserved eukaryotic signaling pathways Notch, Wnt, Hedgehog and Hippo. In addition, TRP120 is also a HECT E3 ubiquitin ligase known to ubiquitinate several host cell regulatory proteins (FBW7, PCGF5 and ENO-1) for degradation. We previously determined that TRP120 ubiquitinates the Notch negative regulator, FBW7, to maintain Notch signaling and promote infection. In this study, we investigated a potential mechanism used by Ehrlichia chaffeensis to maintain Hippo and Wnt signaling by ubiquitinating the tumor suppressor, adenomatous polyposis coli (APC), a negative regulator of Wnt and Hippo signaling. We determined that APC was rapidly degraded during E. chaffeensis infection despite increased APC transcription. Moreover, RNAi knockdown of APC significantly increased E. chaffeensis infection and coincided with increased active Yap and β-catenin in the nucleus. We observed strong nuclear colocalization between TRP120 and APC in E. chaffeensis-infected THP-1 cells and after ectopic expression of TRP120 in HeLa cells. Additionally, TRP120 interacted with both APC full length and truncated isoforms via co-immunoprecipitation. Further, TRP120 ubiquitination of APC was demonstrated in vitro and confirmed by ectopic expression of a TRP120 HECT Ub ligase catalytic site mutant. This study identifies APC as a TRP120 HECT E3 Ub ligase substrate and demonstrates that TRP120 ligase activity promotes ehrlichial infection by degrading tumor suppressor APC to positively regulate Hippo and Wnt signaling.
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Affiliation(s)
| | | | | | | | | | - Jere W. McBride
- Departments of Pathology, Microbiology and Immunology, Center for Biodefense and Emerging Infectious Diseases, Sealy Institute for Vaccine Sciences and Institute for Human Infections and Immunity, University of Texas Medical Branch, Galveston, TX, United States
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Huang J, Xie P, Dong Y, An W. Inhibition of Drp1 SUMOylation by ALR protects the liver from ischemia-reperfusion injury. Cell Death Differ 2021; 28:1174-1192. [PMID: 33110216 PMCID: PMC8027887 DOI: 10.1038/s41418-020-00641-7] [Citation(s) in RCA: 49] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2020] [Revised: 10/08/2020] [Accepted: 10/08/2020] [Indexed: 01/30/2023] Open
Abstract
Hepatic ischemic reperfusion injury (IRI) is a common complication of liver surgery. Although an imbalance between mitochondrial fission and fusion has been identified as the cause of IRI, the detailed mechanism remains unclear. Augmenter of liver regeneration (ALR) was reported to prevent mitochondrial fission by inhibiting dynamin-related protein 1 (Drp1) phosphorylation, contributing partially to its liver protection. Apart from phosphorylation, Drp1 activity is also regulated by small ubiquitin-like modification (SUMOylation), which accelerates mitochondrial fission. This study aimed to investigate whether ALR-mediated protection from hepatic IRI might be associated with an effect on Drp1 SUMOylation. Liver tissues were harvested from both humans and from heterozygous ALR knockout mice, which underwent IRI. The SUMOylation and phosphorylation of Drp1 and their modulation by ALR were investigated. Hepatic Drp1 SUMOylation was significantly increased in human transplanted livers and IRI-livers of mice. ALR-transfection significantly decreased Drp1 SUMOylation, attenuated the IRI-induced mitochondrial fission and preserved mitochondrial stability and function. This study showed that the binding of transcription factor Yin Yang-1 (YY1) to its downstream target gene UBA2, a subunit of SUMO-E1 enzyme heterodimer, was critical to control Drp1 SUMOylation. By interacting with YY1, ALR inhibits its nuclear import and dramatically decreases the transcriptional level of UBA2. Consequently, mitochondrial fission was significantly reduced, and mitochondrial function was maintained. This study showed that the regulation of Drp1 SUMOylation by ALR protects mitochondria from fission, rescuing hepatocytes from IRI-induced apoptosis. These new findings provide a potential target for clinical intervention to reduce the effects of IRI during hepatic surgery.
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Affiliation(s)
- Jing Huang
- grid.24696.3f0000 0004 0369 153XDepartment of Cell Biology, Capital Medical University and the Municipal Key Laboratory for Liver Protection and Regulation of Regeneration, Beijing, China
| | - Ping Xie
- grid.24696.3f0000 0004 0369 153XDepartment of Cell Biology, Capital Medical University and the Municipal Key Laboratory for Liver Protection and Regulation of Regeneration, Beijing, China
| | - Yuan Dong
- grid.24696.3f0000 0004 0369 153XDepartment of Cell Biology, Capital Medical University and the Municipal Key Laboratory for Liver Protection and Regulation of Regeneration, Beijing, China
| | - Wei An
- grid.24696.3f0000 0004 0369 153XDepartment of Cell Biology, Capital Medical University and the Municipal Key Laboratory for Liver Protection and Regulation of Regeneration, Beijing, China
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Parker TW, Rudeen AJ, Neufeld KL. Oncogenic Serine 45-Deleted β-Catenin Remains Susceptible to Wnt Stimulation and APC Regulation in Human Colonocytes. Cancers (Basel) 2020; 12:cancers12082114. [PMID: 32751567 PMCID: PMC7464804 DOI: 10.3390/cancers12082114] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2020] [Revised: 07/25/2020] [Accepted: 07/28/2020] [Indexed: 11/16/2022] Open
Abstract
The Wnt/β-catenin signaling pathway is deregulated in nearly all colorectal cancers (CRCs), predominantly through mutation of the tumor suppressor Adenomatous Polyposis Coli (APC). APC mutation is thought to allow a “just-right” amount of Wnt pathway activation by fine-tuning β-catenin levels. While at a much lower frequency, mutations that result in a β-catenin that is compromised for degradation occur in a subset of human CRCs. Here, we investigate whether one such “stabilized” β-catenin responds to regulatory stimuli, thus allowing β-catenin levels conducive for tumor formation. We utilize cells harboring a single mutant allele encoding Ser45-deleted β-catenin (β-catΔS45) to test the effects of Wnt3a treatment or APC-depletion on β-catΔS45 regulation and activity. We find that APC and β-catΔS45 retain interaction with Wnt receptors. Unexpectedly, β-catΔS45 accumulates and activates TOPflash reporter upon Wnt treatment or APC-depletion, but only accumulates in the nucleus upon APC loss. Finally, we find that β-catenin phosphorylation at GSK-3β sites and proteasomal degradation continue to occur in the absence of Ser45. Our results expand the current understanding of Wnt/β-catenin signaling and provide an example of a β-catenin mutation that maintains some ability to respond to Wnt, a possible key to establishing β-catenin activity that is “just-right” for tumorigenesis.
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Validation and application of a novel APC antibody in western blotting, immunoprecipitation, and immunohistochemistry. Med Mol Morphol 2018; 51:227-236. [DOI: 10.1007/s00795-018-0196-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2018] [Accepted: 06/14/2018] [Indexed: 01/05/2023]
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5
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Gao FJ, Shi L, Hines T, Hebbar S, Neufeld KL, Smith DS. Insulin signaling regulates a functional interaction between adenomatous polyposis coli and cytoplasmic dynein. Mol Biol Cell 2017; 28:587-599. [PMID: 28057765 PMCID: PMC5328618 DOI: 10.1091/mbc.e16-07-0555] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2016] [Revised: 12/23/2016] [Accepted: 12/30/2016] [Indexed: 12/24/2022] Open
Abstract
Diabetes is linked to an increased risk for colorectal cancer, but the mechanistic underpinnings of this clinically important effect are unclear. Here we describe an interaction between the microtubule motor cytoplasmic dynein, the adenomatous polyposis coli tumor suppressor protein (APC), and glycogen synthase kinase-3β (GSK-3β), which could shed light on this issue. GSK-3β is perhaps best known for glycogen regulation, being inhibited downstream in an insulin-signaling pathway. However, the kinase is also important in many other processes. Mutations in APC that disrupt the regulation of β-catenin by GSK-3β cause colorectal cancer in humans. Of interest, both APC and GSK-3β interact with microtubules and cellular membranes. We recently demonstrated that dynein is a GSK-3β substrate and that inhibition of GSK-3β promotes dynein-dependent transport. We now report that dynein stimulation in intestinal cells in response to acute insulin exposure (or GSK-3β inhibition) is blocked by tumor-promoting isoforms of APC that reduce an interaction between wild-type APC and dynein. We propose that under normal conditions, insulin decreases dynein binding to APC to stimulate minus end-directed transport, which could modulate endocytic and secretory systems in intestinal cells. Mutations in APC likely impair the ability to respond appropriately to insulin signaling. This is exciting because it has the potential to be a contributing factor in the development of colorectal cancer in patients with diabetes.
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Affiliation(s)
- Feng J Gao
- Department of Physiology, Johns Hopkins University School of Medicine, Baltimore, MD 21025
| | - Liang Shi
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208
| | - Timothy Hines
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208
| | - Sachin Hebbar
- Department of Anesthesiology and Critical Medicine, Johns Hopkins University School of Medicine, Baltimore, MD 21287
| | - Kristi L Neufeld
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS 66045
| | - Deanna S Smith
- Department of Biological Sciences, University of South Carolina, Columbia, SC 29208
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Wnt/β-catenin signaling plays an ever-expanding role in stem cell self-renewal, tumorigenesis and cancer chemoresistance. Genes Dis 2016; 3:11-40. [PMID: 27077077 PMCID: PMC4827448 DOI: 10.1016/j.gendis.2015.12.004] [Citation(s) in RCA: 203] [Impact Index Per Article: 25.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
Wnt signaling transduces evolutionarily conserved pathways which play important roles in initiating and regulating a diverse range of cellular activities, including cell proliferation, calcium homeostasis, and cell polarity. The role of Wnt signaling in controlling cell proliferation and stem cell self-renewal is primarily carried out through the canonical pathway, which is the best-characterized the multiple Wnt signaling branches. The past 10 years has seen a rapid expansion in our understanding of the complexity of this pathway, as many new components of Wnt signaling have been identified and linked to signaling regulation, stem cell functions, and adult tissue homeostasis. Additionally, a substantial body of evidence links Wnt signaling to tumorigenesis of cancer types and implicates it in the development of cancer drug resistance. Thus, a better understanding of the mechanisms by which dysregulation of Wnt signaling precedes the development and progression of human cancer may hasten the development of pathway inhibitors to augment current therapy. This review summarizes and synthesizes our current knowledge of the canonical Wnt pathway in development and disease. We begin with an overview of the components of the canonical Wnt signaling pathway and delve into the role this pathway has been shown to play in stemness, tumorigenesis, and cancer drug resistance. Ultimately, we hope to present an organized collection of evidence implicating Wnt signaling in tumorigenesis and chemoresistance to facilitate the pursuit of Wnt pathway modulators that may improve outcomes of cancers in which Wnt signaling contributes to aggressive disease and/or treatment resistance.
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Wang L, Liu X, Gusev E, Wang C, Fagotto F. Regulation of the phosphorylation and nuclear import and export of β-catenin by APC and its cancer-related truncated form. J Cell Sci 2014; 127:1647-59. [PMID: 24496450 DOI: 10.1242/jcs.131045] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
We report the first direct analysis of the endogenous β-catenin phosphorylation activity in colon cancer SW480 cells. By comparing parental SW480 cells that harbor a typical truncated adenomatous polyposis coli (APC) form, cells expressing full-length APC and APC-depleted cells, we provide the formal demonstration that APC is necessary for β-catenin phosphorylation, both for priming of the protein at residue serine 45 and for the subsequent phosphorylation of residues 33, 37 and 41. Truncated APC still sustains a surprisingly high phosphorylation activity, which requires the protein to bind to β-catenin through the APC 20-amino-acid (20AA) repeats, thus providing a biochemical explanation for the precise truncations found in cancer cells. We also show that most of the β-catenin phosphorylation activity is associated with a dense insoluble fraction. We finally examine the impact of full-length and truncated APC on β-catenin nuclear transport. We observe that β-catenin is transported much faster than previously thought. Although this fast translocation is largely insensitive to the presence of wild-type or truncated APC, the two forms appear to limit the pool of β-catenin that is available for transport, which could have an impact on β-catenin nuclear activities in normal and cancer cells.
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Affiliation(s)
- Lili Wang
- Department of Clinical Laboratory, Qilu Hospital, Shandong University, Jinan, Shandong 250012, China
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Elliott KL, Catimel B, Church NL, Coates JL, Burgess AW, Layton MJ, Faux MC. Immunopurification of adenomatous polyposis coli (APC) proteins. BMC Res Notes 2013; 6:429. [PMID: 24156781 PMCID: PMC4015550 DOI: 10.1186/1756-0500-6-429] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2013] [Accepted: 10/21/2013] [Indexed: 11/26/2022] Open
Abstract
Background The adenomatous polyposis coli (APC) tumour suppressor gene encodes a 2843 residue (310 kDa) protein. APC is a multifunctional protein involved in the regulation of β-catenin/Wnt signalling, cytoskeletal dynamics and cell adhesion. APC mutations occur in most colorectal cancers and typically result in truncation of the C-terminal half of the protein. Results In order to investigate the biophysical properties of APC, we have generated a set of monoclonal antibodies which enable purification of recombinant forms of APC. Here we describe the characterisation of these anti-APC monoclonal antibodies (APC-NT) that specifically recognise endogenous APC both in solution and in fixed cells. Full-length APC(1–2843) and cancer-associated, truncated APC proteins, APC(1–1638) and APC(1–1311) were produced in Sf9 insect cells. Conclusions Recombinant APC proteins were purified using a two-step affinity approach using our APC-NT antibodies. The purification of APC proteins provides the basis for detailed structure/function analyses of full-length, cancer-truncated and endogenous forms of the protein.
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Affiliation(s)
| | | | | | | | | | | | - Maree C Faux
- Ludwig Institute for Cancer Research-Parkville branch, Parkville, VIC 3050, Australia.
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9
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Abstract
The Wnt/β-catenin pathway is highly regulated to insure the correct temporal and spatial activation of its target genes. In the absence of a Wnt stimulus, the transcriptional coactivator β-catenin is degraded by a multiprotein "destruction complex" that includes the tumor suppressors Axin and adenomatous polyposis coli (APC), the Ser/Thr kinases GSK-3 and CK1, protein phosphatase 2A (PP2A), and the E3-ubiquitin ligase β-TrCP. The complex generates a β-TrCP recognition site by phosphorylation of a conserved Ser/Thr-rich sequence near the β-catenin amino terminus, a process that requires scaffolding of the kinases and β-catenin by Axin. Ubiquitinated β-catenin is degraded by the proteasome. The molecular mechanisms that underlie several aspects of destruction complex function are poorly understood, particularly the role of APC. Here we review the molecular mechanisms of destruction complex function and discuss several potential roles of APC in β-catenin destruction.
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Affiliation(s)
- Jennifer L Stamos
- Departments of Structural Biology and Molecular and Cellular Physiology, Stanford University School of Medicine, Stanford, CA 94305, USA
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Song J, Hao Y, Du Z, Wang Z, Ewing RM. Identifying novel protein complexes in cancer cells using epitope-tagging of endogenous human genes and affinity-purification mass spectrometry. J Proteome Res 2012; 11:5630-41. [PMID: 23106643 DOI: 10.1021/pr300598t] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
Abstract
Affinity-purification mass spectrometry (AP-MS) is the preeminent technique for identification of eukaryotic protein complexes in vivo. AP-MS workflows typically express epitope-tagged bait proteins, immunopurify, and then identify associated protein complexes using mass spectrometry. However, challenges of existing strategies include the construction of expression vectors for large open reading frames and the possibility that overexpression of bait proteins may result in expression of nonphysiological levels of the bait protein with concomitant perturbation of endogenous protein complexes. To address these issues, we use human cell lines with epitope-tagged endogenous genes as AP-MS substrates to develop a platform that we call "knock-in AP-MS", thereby avoiding the challenges of expression vector construction and ensuring that expression of tagged proteins is driven by endogenous regulatory mechanisms. Using three different bait genes (MRE11A, DNMT1 and APC), we show that cell lines expressing epitope-tagged endogenous genes make good substrates for sensitive and reproducible identification of protein interactions using AP-MS. In particular, we identify novel interactors of the important oncoprotein Adenomatous Polyposis Coli (APC), including an interaction with Flightless-1 homologue (FLII) that is enriched in nuclear fractions.
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Affiliation(s)
- Jing Song
- Center for Proteomics and Bioinformatics, Department of Genetics and Genome Science, Case Western Reserve University School of Medicine, Cleveland, Ohio 44106, United States
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11
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Weston L, Coutts AS, La Thangue NB. Actin nucleators in the nucleus: an emerging theme. J Cell Sci 2012; 125:3519-27. [PMID: 22935654 DOI: 10.1242/jcs.099523] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Actin is an integral component of the cytoskeleton, forming a plethora of macromolecular structures that mediate various cellular functions. The formation of such structures relies on the ability of actin monomers to associate into polymers, and this process is regulated by actin nucleation factors. These factors use monomeric actin pools at specific cellular locations, thereby permitting rapid actin filament formation when required. It has now been established that actin is also present in the nucleus, where it is implicated in chromatin remodelling and the regulation of eukaryotic gene transcription. Notably, the presence of typical actin filaments in the nucleus has not been demonstrated directly. However, studies in recent years have provided evidence for the nuclear localisation of actin nucleation factors that promote cytoplasmic actin polymerisation. Their localisation to the nucleus suggests that these proteins mediate collaboration between the cytoskeleton and the nucleus, which might be dependent on their ability to promote actin polymerisation. The nature of this cooperation remains enigmatic and it will be important to elucidate the physiological relevance of the link between cytoskeletal actin networks and nuclear events. This Commentary explores the current evidence for the nuclear roles of actin nucleation factors. Furthermore, the implication of actin-associated proteins in relaying exogenous signals to the nucleus, particularly in response to cellular stress, will be considered.
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Affiliation(s)
- Louise Weston
- Laboratory of Cancer Biology, Department of Oncology, University of Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, UK.
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12
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Brüning-Richardson A, Langford KJ, Ruane P, Lee T, Askham JM, Morrison EE. EB1 is required for spindle symmetry in mammalian mitosis. PLoS One 2011; 6:e28884. [PMID: 22216133 PMCID: PMC3244432 DOI: 10.1371/journal.pone.0028884] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2011] [Accepted: 11/16/2011] [Indexed: 12/30/2022] Open
Abstract
Most information about the roles of the adenomatous polyposis coli protein (APC) and its binding partner EB1 in mitotic cells has come from siRNA studies. These suggest functions in chromosomal segregation and spindle positioning whose loss might contribute to tumourigenesis in cancers initiated by APC mutation. However, siRNA-based approaches have drawbacks associated with the time taken to achieve significant expression knockdown and the pleiotropic effects of EB1 and APC gene knockdown. Here we describe the effects of microinjecting APC- or EB1- specific monoclonal antibodies and a dominant-negative EB1 protein fragment into mammalian mitotic cells. The phenotypes observed were consistent with the roles proposed for EB1 and APC in chromosomal segregation in previous work. However, EB1 antibody injection also revealed two novel mitotic phenotypes, anaphase-specific cortical blebbing and asymmetric spindle pole movement. The daughters of microinjected cells displayed inequalities in microtubule content, with the greatest differences seen in the products of mitoses that showed the severest asymmetry in spindle pole movement. Daughters that inherited the least mobile pole contained the fewest microtubules, consistent with a role for EB1 in processes that promote equality of astral microtubule function at both poles in a spindle. We propose that these novel phenotypes represent APC-independent roles for EB1 in spindle pole function and the regulation of cortical contractility in the later stages of mitosis. Our work confirms that EB1 and APC have important mitotic roles, the loss of which could contribute to CIN in colorectal tumour cells.
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Affiliation(s)
- Anke Brüning-Richardson
- Leeds Institute of Molecular Medicine, University of Leeds, St. James's University Hospital, Leeds, United Kingdom.
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Lui C, Mills K, Brocardo MG, Sharma M, Henderson BR. APC as a mobile scaffold: regulation and function at the nucleus, centrosomes, and mitochondria. IUBMB Life 2011; 64:209-14. [PMID: 22162224 DOI: 10.1002/iub.599] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2011] [Accepted: 11/02/2011] [Indexed: 12/13/2022]
Abstract
Genetic mutations of adenomatous polyposis coli (APC) predispose to high risk of human colon cancer. APC is a large tumor suppressor protein and truncating mutations disrupt its normal roles in regulating cell migration, DNA replication/repair, mitosis, apoptosis, and turnover of oncogenic β-catenin. APC is targeted to multiple subcellular sites, and here we discuss recent evidence implicating novel protein interactions and functions of APC in the nucleus and at centrosomes and mitochondria. The ability of APC to shuttle between these and other cell locations is hypothesized to be integral to its cellular function.
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Affiliation(s)
- Christina Lui
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, New South Wales, Australia
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14
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Effects of epigenetic-based anti-cancer drugs in leukaemia and multiple myeloma cells. Cell Biol Int 2011; 35:1195-203. [DOI: 10.1042/cbi20100820] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Chen Y, Tian X, Kim WY, Snider WD. Adenomatous polyposis coli regulates axon arborization and cytoskeleton organization via its N-terminus. PLoS One 2011; 6:e24335. [PMID: 21915313 PMCID: PMC3167844 DOI: 10.1371/journal.pone.0024335] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2011] [Accepted: 08/04/2011] [Indexed: 01/23/2023] Open
Abstract
Conditional deletion of APC leads to marked disruption of cortical development and to excessive axonal branching of cortical neurons. However, little is known about the cell biological basis of this neuronal morphological regulation. Here we show that APC deficient cortical neuronal growth cones exhibit marked disruption of both microtubule and actin cytoskeleton. Functional analysis of the different APC domains revealed that axonal branches do not result from stabilized β-catenin, and that the C-terminus of APC containing microtubule regulatory domains only partially rescues the branching phenotype. Surprisingly, the N-terminus of APC containing the oligomerization domain and the armadillo repeats completely rescues the branching and cytoskeletal abnormalities. Our data indicate that APC is required for appropriate axon morphological development and that the N-terminus of APC is important for regulation of the neuronal cytoskeleton.
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Affiliation(s)
- Youjun Chen
- Department of Cell and Molecular Physiology and Neuroscience Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
| | - Xu Tian
- Hefei National Laboratory for Physical Sciences at Microscale and School of Life Sciences, University of Science and Technology of China, Hefei, Anhui Province, People's Republic of China
| | - Woo-Yang Kim
- Department of Developmental Neuroscience, Munroe-Meyer Institute, University of Nebraska Medical Center, Omaha, Nebraska, United States of America
| | - William D. Snider
- Department of Cell and Molecular Physiology and Neuroscience Center, School of Medicine, University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, United States of America
- * E-mail:
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16
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Schneikert J, Brauburger K, Behrens J. APC mutations in colorectal tumours from FAP patients are selected for CtBP-mediated oligomerization of truncated APC. Hum Mol Genet 2011; 20:3554-64. [PMID: 21665989 DOI: 10.1093/hmg/ddr273] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
The germline transmission of a mutation in the adenomatous polyposis coli (APC) gene leads to cancer of the gastro-intestinal tract upon somatic inactivation of the remaining allele in familial adenomatous polyposis (FAP) patients. APC mutations result in truncated products that have primarily lost the ability to properly regulate the level of the transcription factor β-catenin. However, colorectal cancer cells from FAP patients always retain a truncated APC product and the reasons for this strong selective pressure are not understood. We describe here the surprising property for the transcriptional repressor C-terminal binding protein (CtBP) to promote the oligomerization of truncated APC through binding to the 15 amino acid repeats of truncated APC. CtBP can bind to either first, third or fourth 15 amino acid repeats, but not to the second. CtBP-mediated oligomerization requires both dimerization domains of truncated APC as well as CtBP dimerization. The analysis of the position of the mutations along the APC sequence in adenomas from FAP patients reveals that the presence of the first 15 amino acid repeat is almost always selected in the resulting truncated APC product. This suggests that the sensitivity of truncated APC to oligomerization by CtBP constitutes an essential facet of tumour development.
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Affiliation(s)
- Jean Schneikert
- Nikolaus-Fiebiger-Center for Molecular Medicine, University of Erlangen-Nu¨rnberg, Glu¨ckstrasse 6, 91054 Erlangen,Germany.
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17
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Brocardo MG, Borowiec JA, Henderson BR. Adenomatous polyposis coli protein regulates the cellular response to DNA replication stress. Int J Biochem Cell Biol 2011; 43:1354-64. [PMID: 21664290 DOI: 10.1016/j.biocel.2011.05.013] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 05/12/2011] [Accepted: 05/24/2011] [Indexed: 10/18/2022]
Abstract
The adenomatous polyposis coli (APC) tumor suppressor traffics between nucleus and cytoplasm to perform distinct functions. Here we identify a specific role for APC in the DNA replication stress response. The silencing of APC caused an accumulation of asynchronous cells in early S phase and delayed S phase progression in cells released from hydroxyurea-mediated replication arrest. Immunoprecipitation assays revealed a selective binding of APC to replication protein A 32kDa subunit (RPA32), and the APC-RPA32 complex increased at chromatin after hydroxyurea treatment. Interestingly, APC knock-down prevented accumulation at chromatin of the stress-induced S33- and S29-phosphorylated forms of RPA32, and reduced the expression of ATR-phosphorylated forms of S317-phospho-Chk1 and γ-H2AX. Using RPA32-inducible cells we showed that reconstitution of RPA32 diminished the S-phase delay caused by loss of APC. In contrast to full-length APC, the truncated APC mutant protein expressed in SW480 colon cancer cells was impaired in its binding and regulation of RPA32, and failed to regulate cell cycle after replication stress. We propose that APC associates with RPA at stalled DNA replication forks and promotes the ATR-dependent phosphorylation of RPA32, Chk1 and γ-H2AX in response to DNA replication stress, thereby influencing the rate of re-entry into the cell cycle.
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Affiliation(s)
- Mariana G Brocardo
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia.
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18
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Zhou MN, Kunttas-Tatli E, Zimmerman S, Zhouzheng F, McCartney BM. Cortical localization of APC2 plays a role in actin organization but not in Wnt signaling in Drosophila. J Cell Sci 2011; 124:1589-600. [PMID: 21486956 DOI: 10.1242/jcs.073916] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
The tumor suppressor Adenomatous polyposis coli (APC) has roles in both Wnt signaling and in actin and microtubule organization. Within the cell, APC proteins have been reported to localize in the cytoplasm, at the cell cortex and in the nucleus. How these localizations relate to the functions of the protein is an aspect of APC biology that is poorly understood. Using Drosophila S2 cells, we have dissected the structural and functional requirements for the cortical localization of Drosophila APC2. Here, we show that both the Armadillo repeats and a novel C-terminal domain are necessary for the cortical localization of APC2 in S2 cells and in the embryo, and that neither domain alone is sufficient for this localization. Furthermore, we show that the Armadillo repeats mediate self-association of APC2 molecules. To test the function of the cortical localization of APC2, we asked whether an APC2 protein deleted for the C-terminal localization domain could rescue APC mutant defects in Wnt signaling and actin organization in the Drosophila embryo. We show that although cortical localization is required for the APC2 function in organizing actin, cortical localization is dispensable for its role in regulating Wnt signaling.
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Affiliation(s)
- Meng-Ning Zhou
- Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, PA 15213, USA
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Lee YH, Tan HT, Chung MCM. Subcellular fractionation methods and strategies for proteomics. Proteomics 2010; 10:3935-56. [DOI: 10.1002/pmic.201000289] [Citation(s) in RCA: 74] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
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Balaz P, Plaschke J, Krüger S, Görgens H, Schackert HK. TCF-3, 4 protein expression correlates with beta-catenin expression in MSS and MSI-H colorectal cancer from HNPCC patients but not in sporadic colorectal cancers. Int J Colorectal Dis 2010; 25:931-9. [PMID: 20532534 DOI: 10.1007/s00384-010-0959-9] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 05/21/2010] [Indexed: 02/04/2023]
Abstract
PURPOSE The beta-catenin-T-cell factor-4 (TCF-4) complex is the main control switch of cell proliferation and differentiation of normal and malignant intestinal cells. The aim of our study was to analyze the protein expression of components of the Wnt pathway in microsatellite stable (MSS) and highly unstable (MSI-H) sporadic and hereditary nonpolyposis colorectal cancer (HNPCC) in human colorectal cancers. METHODS Sixty seven colorectal tumors comprising of 15 sporadic MSS, 12 sporadic microsatellite instability colorectal tumors and 40 tumors from HNPCC patients, of which 20 were MSS and 20 MSI-H, were analyzed for the expression of APC, beta-catenin, and TCF-3, 4 proteins by immunohistochemistry. RESULTS We found a significant difference in cytoplasmic APC expression frequency between sporadic MSS (52%) and HNPCC tumors (78%), whereas no difference was detected between MSI-H and MSS or HNPCC tumors. All tumor groups showed a similar pattern of decreased membranous staining and increased cytoplasmic and nuclear staining for beta-catenin compared to normal cells. Moreover, the TCF-3, 4 protein expression was higher (43%) in HNPCC-associated MSS tumors compared to sporadic tumors (14%; analysis of variance (ANOVA) p < 0.05). For HNPCC tumors, the subcellular beta-catenin expression (membranous, cytoplasmic, and nuclear) correlated with the nuclear TCF-3, 4 signal in MSS tumors (Spearman correlation p < 0.0007) and MSI-H tumors (Spearman correlation p < 0.0001). CONCLUSION We have shown a previously unknown difference in TCF-3, 4 protein expression between sporadic and HNPCC MSS tumors. In addition, we found no difference in nuclear beta-catenin signal intensity, which may be caused by an alteration in Wnt pathway in MSS sporadic tumors by unknown mechanisms leading to lower TCF-3, 4 protein expression. This hypothesis has to be tested in future investigations.
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Affiliation(s)
- Peter Balaz
- Department of Surgical Research, Technische Universität Dresden, Dresden, Germany
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Wang Y, Azuma Y, Friedman DB, Coffey RJ, Neufeld KL. Novel association of APC with intermediate filaments identified using a new versatile APC antibody. BMC Cell Biol 2009; 10:75. [PMID: 19845967 PMCID: PMC2774295 DOI: 10.1186/1471-2121-10-75] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Accepted: 10/21/2009] [Indexed: 12/28/2022] Open
Abstract
BACKGROUND As a key player in suppression of colon tumorigenesis, Adenomatous Polyposis Coli (APC) has been widely studied to determine its cellular functions. However, inconsistencies of commercially available APC antibodies have limited the exploration of APC function. APC is implicated in spindle formation by direct interactions with tubulin and microtubule-binding protein EB1. APC also interacts with the actin cytoskeleton to regulate cell polarity. Until now, interaction of APC with the third cytoskeletal element, intermediate filaments, has remained unexamined. RESULTS We generated an APC antibody (APC-M2 pAb) raised against the 15 amino acid repeat region, and verified its reliability in applications including immunoprecipitation, immunoblotting, and immunofluorescence in cultured cells and tissue. Utilizing this APC-M2 pAb, we immunoprecipitated endogenous APC and its binding proteins from colon epithelial cells expressing wild-type APC. Using Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS), we identified 42 proteins in complex with APC, including beta-catenin and intermediate filament (IF) proteins lamin B1 and keratin 81. Association of lamin B1 with APC in cultured cells and human colonic tissue was verified by co-immunoprecipitation and colocalization. APC also colocalized with keratins and remained associated with IF proteins throughout a sequential extraction procedure. CONCLUSION We introduce a versatile APC antibody that is useful for cell/tissue immunostaining, immunoblotting and immunoprecipitation. We also present evidence for interactions between APC and IFs, independent of actin filaments and microtubules. Our results suggest that APC associates with all three major components of the cytoskeleton, thus expanding potential roles for APC in the regulation of cytoskeletal integrity.
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Affiliation(s)
- Yang Wang
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
| | - Yoshiaki Azuma
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
| | - David B Friedman
- Mass Spectrometry Research Center, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Robert J Coffey
- Departments of Cell and Developmental Biology and Medicine, Vanderbilt University Medical Center, Nashville, TN, USA
| | - Kristi L Neufeld
- Department of Molecular Biosciences, University of Kansas, Lawrence, KS, USA
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Kawasaki Y, Tsuji S, Sagara M, Echizen K, Shibata Y, Akiyama T. Adenomatous polyposis coli and Asef function downstream of hepatocyte growth factor and phosphatidylinositol 3-kinase. J Biol Chem 2009; 284:22436-22443. [PMID: 19525225 DOI: 10.1074/jbc.m109.020768] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Mutations of the tumor suppressor adenomatous polyposis coli (APC) are responsible for sporadic and familial colorectal tumors. APC negatively regulates Wnt signaling by inducing beta-catenin degradation. It has also been shown that APC plays a role in the organization of cytoskeletal networks. APC interacts with Asef and Asef2, Rac1- and Cdc42-specific guanine nucleotide exchange factors (GEFs), and stimulates their GEF activity; thereby regulating cell morphology, adhesion, and migration. Truncated mutant APCs present in colorectal tumor cells activate Asef and Asef2 constitutively and contribute to their aberrant migratory properties. We show here that hepatocyte growth factor (HGF), as well as basic fibroblast growth factor (bFGF) and epidermal growth factor (EGF), induce the accumulation and colocalization of APC and Asef in membrane ruffles and lamellipodia of epithelial cells. Both APC and Asef were found to be required for HGF-induced cell migration. Furthermore, we show that the effects of HGF, bFGF, and EGF on APC and Asef are mediated by the activation of phosphatidylinositol 3-kinase (PI3-kinase) and require the PH domain of Asef. These results suggest that Asef and APC function downstream of HGF and PI3-kinase, and play critical roles in growth factor-mediated regulation of cell morphology and migration.
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Affiliation(s)
- Yoshihiro Kawasaki
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113, Japan
| | - Shinnosuke Tsuji
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113, Japan
| | - Masaki Sagara
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113, Japan
| | - Kanae Echizen
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113, Japan
| | - Yoko Shibata
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113, Japan
| | - Tetsu Akiyama
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Tokyo 113, Japan
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Brocardo M, Henderson BR. Detection of cytoplasmic and nuclear localization of adenomatous polyposis coli (APC) protein in cells. Methods Mol Biol 2009; 468:77-89. [PMID: 19099247 DOI: 10.1007/978-1-59745-249-6_6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/11/2023]
Abstract
The adenomatous polyposis coli (APC) tumour suppressor gene is mutated in the majority of colon cancers. APC is a multi-domain protein whose distribution at different subcellular locations correlates with unique cellular processes. Our laboratory has focused on the link between APC subcellular location and function, and has characterized pathways for the trafficking of APC both into and out of the nucleus. Antibody specificity is an important factor in the determination of APC localization, and in this chapter we outline a strategy for the unambiguous detection of APC using a combination of biochemical and cell biology approaches.
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Affiliation(s)
- Mariana Brocardo
- Westmead Millennium Institute, The University of Sydney, NSW, Australia
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Wassermann S, Scheel SK, Hiendlmeyer E, Palmqvist R, Horst D, Hlubek F, Haynl A, Kriegl L, Reu S, Merkel S, Brabletz T, Kirchner T, Jung A. p16INK4a is a beta-catenin target gene and indicates low survival in human colorectal tumors. Gastroenterology 2009; 136:196-205.e2. [PMID: 18951899 DOI: 10.1053/j.gastro.2008.09.019] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/13/2007] [Revised: 08/15/2008] [Accepted: 09/11/2008] [Indexed: 01/21/2023]
Abstract
BACKGROUND & AIMS Human colorectal carcinomas display an infiltrative front of invasion where tumor cells undergo an epithelomesenchymal transition associated with low survival. Epithelomesenchymal transition is regulated by a nuclear beta-catenin accumulation, and subsequently, activation of beta-catenin/TCF4 target genes similar to CYCLIN D(1). Unexpectedly, these tumor cells are characterized by low proliferation, which correlates with the expression of the cell cycle inhibitor p16(INK4A). Therefore, we investigated the molecular mechanism of the transcriptional regulation of p16(INK4A) in colorectal cancer and its correlation with survival. METHODS Molecular biological techniques were used for investigating the transcriptional mechanisms of the p16(INK4A) gene regulation. Moreover, p16(INK4A) expression was correlated with the 10-year survival of patients with colorectal carcinomas. RESULTS In colorectal carcinomas, expression of the p16(INK4A) gene is regulated by beta-catenin/TCF4 and correlates with low survival rates of patients with tumors displaying an infiltrative front of invasion. CONCLUSIONS beta-catenin/TCF4 regulates cell cycle promoting (c-MYC, CYCLIN D(1)) and inhibiting genes (p16(INK4A)) at the same time in the mesenchymally differentiated tumor cells at the front of invasion. The function of p16(INK4A) seems to supersede in this context thus leading to low proliferation. Moreover, these tumor cells seem to govern the outcome of colorectal cancer independently of their proliferation.
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Affiliation(s)
- Stella Wassermann
- Pathologisch-Anatomisches Institut der Universität Erlangen-Nürnberg, Erlangen, Germany
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Kennell J, Cadigan KM. APC and beta-catenin degradation. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2009; 656:1-12. [PMID: 19928348 DOI: 10.1007/978-1-4419-1145-2_1] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Affiliation(s)
- Jennifer Kennell
- Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI, USA
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Abstract
Mutational inactivation of the tumor suppressor gene APC (Adenomatous polyposis coli) is thought to be an initiating step in the progression of the vast majority ofcolorectal cancers. Attempts to understand APC function have revealed more than a dozen binding partners as well as several subcellular localizations including at cell-cell junctions, associated with microtubules at the leading edge of migrating cells, at the apical membrane, in the cytoplasm and in the nucleus. The present chapter focuses on APC localization and functions in the nucleus. APC contains two classical nuclear localization signals, with a third domain that can enhance nuclear import. Along with two sets of nuclear export signals, the nuclear localization signals enable the large APC protein to shuttle between the nucleus and cytoplasm. Nuclear APC can oppose beta-catenin-mediated transcription. This down-regulation of nuclear beta-catenin activity by APC most likely involves nuclear sequestration of beta-catenin from the transcription complex as well as interaction of APC with transcription corepressor CtBP. Additional nuclear binding partners for APC include transcription factor activator protein AP-2alpha, nuclear export factor Crm1, protein tyrosine phosphatase PTP-BL and perhaps DNA itself. Interaction of APC with polymerase beta and PCNA, suggests a role for APC in DNA repair. The observation that increases in the cytoplasmic distribution of APC correlate with colon cancer progression suggests that disruption of these nuclear functions of APC plays an important role in cancer progression. APC prevalence in the cytoplasm of quiescent cells points to a potential function for nuclear APC in control of cell proliferation. Clear definition of APC's nuclear function(s) will expand the possibilities for early colorectal cancer diagnostics and therapeutics targeted to APC.
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27
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Brocardo M, Henderson BR. APC shuttling to the membrane, nucleus and beyond. Trends Cell Biol 2008; 18:587-96. [DOI: 10.1016/j.tcb.2008.09.002] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Revised: 09/13/2008] [Accepted: 09/16/2008] [Indexed: 11/29/2022]
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Kohler EM, Chandra SHV, Behrens J, Schneikert J. -Catenin degradation mediated by the CID domain of APC provides a model for the selection of APC mutations in colorectal, desmoid and duodenal tumours. Hum Mol Genet 2008; 18:213-26. [DOI: 10.1093/hmg/ddn338] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
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29
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Qian J, Sarnaik AA, Bonney TM, Keirsey J, Combs KA, Steigerwald K, Acharya S, Behbehani GK, Barton MC, Lowy AM, Groden J. The APC tumor suppressor inhibits DNA replication by directly binding to DNA via its carboxyl terminus. Gastroenterology 2008; 135:152-62. [PMID: 18474248 PMCID: PMC2832605 DOI: 10.1053/j.gastro.2008.03.074] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/18/2007] [Revised: 02/26/2008] [Accepted: 03/27/2008] [Indexed: 01/11/2023]
Abstract
BACKGROUND & AIMS The APC tumor suppressor is well known for its ability to regulate Wnt signaling through mediation of beta-catenin levels in the cell. Transient over expression of the tumor suppressor gene APC in colon cancer cells prevents entry into S phase of the cell cycle, a phenotype only partially restored by cotransfection of a transcriptionally active form of beta-catenin. In an attempt to define its transcription-independent tumor suppressor functions, we tested whether APC directly affects DNA replication. METHODS A transcriptionally quiescent in vitro DNA replication system, the polymerase chain reaction, DNA binding assays, and transient transfections in colon cancer cell lines were used to determine the effects of APC on DNA replication and the mechanism by which it works. RESULTS We report that exogenous full-length APC inhibits replication of template DNA through a function that maps to amino acids 2140-2421, a region of the protein commonly lost by somatic or germline mutation. This segment of APC directly interacts with DNA, while mutation of the DNA-binding S(T)PXX motifs within it abolishes DNA binding and reduces inhibition of DNA replication. Phosphorylation of this segment by cyclin-dependent kinases also reduces inhibition of DNA replication. Furthermore, transient transfection of an APC segment encoding amino acids 2140-2421 into a colon cancer cell line with mutant APC prevents cell cycle progression into or through S phase. CONCLUSIONS Our results suggest that APC can negatively regulate cell cycle progression through inhibition of DNA replication by direct interaction with DNA.
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Affiliation(s)
- Jiang Qian
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, OH 43210-2207,Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Amod A. Sarnaik
- Division of Surgical Oncology in the Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Tera M. Bonney
- Division of Surgical Oncology in the Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Jeremy Keirsey
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, OH 43210-2207
| | - Kelly A. Combs
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Kira Steigerwald
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Samir Acharya
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, OH 43210-2207
| | - Gregory K. Behbehani
- Department of Molecular Genetics, Biochemistry and Microbiology, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Michelle C. Barton
- Department of Biochemistry and Molecular Biology, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030
| | - Andy M. Lowy
- Division of Surgical Oncology in the Department of Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267
| | - Joanna Groden
- Department of Molecular Virology, Immunology and Medical Genetics, The Ohio State University, Columbus, OH 43210-2207,To whom reprint requests should be addressed:
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Hendriksen J, Jansen M, Brown CM, van der Velde H, van Ham M, Galjart N, Offerhaus GJ, Fagotto F, Fornerod M. Plasma membrane recruitment of dephosphorylated beta-catenin upon activation of the Wnt pathway. J Cell Sci 2008; 121:1793-802. [PMID: 18460581 DOI: 10.1242/jcs.025536] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The standard model of Wnt signaling specifies that after receipt of a Wnt ligand at the membranous receptor complex, downstream mediators inhibit a cytoplasmic destruction complex, allowing beta-catenin to accumulate in the cytosol and nucleus and co-activate Wnt target genes. Unexpectedly, shortly after Wnt treatment, we detected the dephosphorylated form of beta-catenin at the plasma membrane, where it displayed a discontinuous punctate labeling. This pool of beta-catenin could only be detected in E-cadherin(-/-) cells, because in E-cadherin(+/+) cells Wnt-induced, membranous beta-catenin was concealed by a constitutive junctional pool. Wnt-signaling-dependent dephosphorylated beta-catenin colocalized at the plasma membrane with two members of the destruction complex -- APC and axin -- and the activated Wnt co-receptor LRP6. beta-catenin induced through the Wnt receptor complex was significantly more competent transcriptionally than overexpressed beta-catenin, both in cultured cells and in early Xenopus embryos. Our data reveal a new step in the processing of the Wnt signal and suggest regulation of signaling output beyond the level of protein accumulation.
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Affiliation(s)
- Jolita Hendriksen
- Department of Tumor Biology, The Netherlands Cancer Institute, Amsterdam, The Netherlands
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31
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Kouzmenko AP, Takeyama K, Kawasaki Y, Akiyama T, Kato S. Truncation mutations abolish chromatin-associated activities of adenomatous polyposis coli. Oncogene 2008; 27:4888-99. [PMID: 18454178 DOI: 10.1038/onc.2008.127] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The adenomatous polyposis coli (APC) is a tumor suppressor whose loss of function leads to colon cancer. APC shuttles between the nucleus and cytoplasm, however its role in the nucleus remains elusive. We have found that nuclear APC specifically associates with transcriptionally active chromatin through structural elements located downstream to the region of frequent truncation mutations found in colorectal tumors. We show that a recombinant APC fragment comprising such elements associates in vivo with euchromatin and preferentially binds in vitro to acetylated histone H3. Induction of DNA double-strand breaks (DSB) stimulates accumulation of APC at the damaged DNA chromatin marked by histone H2AX and S139-phosphorylated histone H2AX. A nuclear complex containing the DNA-dependent protein kinase catalytic subunit (DNAPKcs) and APC associates with chromatin in response to DNA DSB. APC knockdown with siRNA decreased the rate of DNA DSB-induced S139 histone H2AX phosphorylation in cells expressing endogenous full-length APC, but not in colon cancer cells with its truncation mutants, whereas ectopic APC expression stimulated the H2AX phosphorylation regardless of the type of endogenous APC. Our data suggest that APC involves in the DSB DNA repair and that truncation mutations impair chromatin-associated functions of APC.
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Affiliation(s)
- A P Kouzmenko
- Department of Nuclear Signaling, Institute of Molecular and Cellular Biosciences, University of Tokyo, Bunkyo-ku, Tokyo, Japan
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Ohshima R, Ohta T, Wu W, Koike A, Iwatani T, Henderson M, Watts CKW, Otsubo T. Putative tumor suppressor EDD interacts with and up-regulates APC. Genes Cells 2008; 12:1339-45. [PMID: 18076571 DOI: 10.1111/j.1365-2443.2007.01138.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Adenomatous polyposis coli (APC), whose mutation causes colorectal cancers, is a key player in the Wnt signaling pathway. While the role of APC in inhibition of beta-catenin/LEF1-dependent activation of transformation-inducing genes has been intensively studied and well established, regulation of APC expression at the protein level is only partially understood. Here we report that APC is up-regulated by EDD, the mammalian orthologue of Drosophila melanogaster"hyperplastic discs" gene (hyd) that is considered to be a putative tumor suppressor. Screening of APC immunocomplexes by mass spectrometry identified EDD as a putative APC-interacting protein. Exogenously expressed and endogenous APC interacted with EDD in vivo. Indirect immunofluorescent analyses demonstrated that APC and EDD co-localized in the cytoplasm of the cell. Over-expression of EDD enhanced the protein expression level of APC and its binding partner Axin, resulting in inhibition of Wnt signaling downstream of beta-catenin. Conversely, siRNA knock-down of EDD down-regulated APC at the protein level without altering its mRNA level, causing enhanced protein expression of beta-catenin. Thus, through protein-protein interaction, EDD stabilizes APC and up-regulates APC's function to inhibit beta-catenin, suggesting that EDD could act as a colorectal tumor suppressor.
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Affiliation(s)
- Ryuichi Ohshima
- Division of Gastroenterological Surgery, Department of Surgery, St. Marianna University School of Medicine, Kawasaki 216-8511, Japan
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Brocardo M, Lei Y, Tighe A, Taylor SS, Mok MT, Henderson BR. Mitochondrial Targeting of Adenomatous Polyposis Coli Protein Is Stimulated by Truncating Cancer Mutations. J Biol Chem 2008; 283:5950-9. [DOI: 10.1074/jbc.m708775200] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
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Davies ML, Roberts GT, Stuart N, Wakeman JA. Analysis of a panel of antibodies to APC reveals consistent activity towards an unidentified protein. Br J Cancer 2007; 97:384-90. [PMID: 17595655 PMCID: PMC2360331 DOI: 10.1038/sj.bjc.6603873] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
Acquisition of truncating mutations in the adenomatous polyposis coli (APC) protein underlies the progression of the majority of sporadic and familial colorectal cancers. As such, the localisation patterns and interacting partners of APC have been extensively studied in a range of systems, relying on the use of a broad panel of antibodies. Until recently, antibodies to APC have been used largely unchecked. However, several recent reports have been invaluable in clarifying the use of a number of antibodies commonly used to detect APC. Here, we analyse the specificity of a further subset of antibodies to APC. We used a panel of six commercially available antibodies (directed to the amino and carboxy termini of APC) and confirm the detection of full-length APC by immunoblotting. We demonstrate that a 150 kDa protein, also reproducibly detected by this panel of antibodies, is unlikely to be APC. We present data for the immunological staining patterns of the APC antibodies and validate the results through RNAi. Using this approach, we confirm that the apical staining pattern, observed by immunofluorescence and previously reported in cell systems, is unlikely to be APC. Finally, we present our data as a summary of APC-antibody specificities for APC.
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Affiliation(s)
- M L Davies
- North West Cancer Research Fund Institute, School of Biological Sciences, University of Wales Bangor, Bangor LL57 2UW, UK.
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Senda T, Iizuka-Kogo A, Onouchi T, Shimomura A. Adenomatous polyposis coli (APC) plays multiple roles in the intestinal and colorectal epithelia. Med Mol Morphol 2007; 40:68-81. [PMID: 17572842 DOI: 10.1007/s00795-006-0352-5] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2006] [Accepted: 12/19/2006] [Indexed: 01/17/2023]
Abstract
The adenomatous polyposis coli (APC) gene is mutated in familial adenomatous polyposis and in most sporadic colorectal tumors. During both embryonic and postnatal periods, APC is widely expressed in a variety of tissues, including the brain and gastrointestinal tract. The APC gene product (APC) is a large multidomain protein consisting of 2843 amino acids. APC downregulates the Wnt signaling pathway through its binding to beta-catenin and Axin. Most mutated APC proteins in colorectal tumors lack the beta-catenin-binding regions and fail to inhibit Wnt signaling, leading to the overproliferation of tumor cells. Several mouse models (APC580D, APCDelta716, APC1309, APCMin, APC1638T) have been established to investigate carcinogenesis caused by APC mutations. APC also binds to APC-stimulated guanine nucleotide exchange factor, the kinesin superfamily-associated protein 3, IQGAP1, microtubules, EB1, and discs large (DLG). APC has both nuclear localization signals and nuclear export signals in its molecule, suggesting its occasional nuclear localization and export of beta-catenin from the nucleus. APC is highly expressed in the intestinal and colorectal epithelia and may be involved in homeostasis of the enterocyte renewal phenomena, in which proliferation, migration, differentiation, and apoptosis are highly regulated both temporally and spatially. Through the many binding proteins mentioned, APC can exert multiple functions involved in epithelial homeostasis.
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Affiliation(s)
- Takao Senda
- Department of Anatomy I, Fujita Health University School of Medicine, Toyoake, Aichi, 470-1192, Japan.
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Abstract
The tumour suppressor adenomatous polyposis coli (APC) is mutated in sporadic and familial colorectal tumours. APC binds to beta-catenin, a key component of the Wnt signalling pathway, and induces its degradation. In addition to this role, there is increasing evidence for additional roles of APC, including the organization of cytoskeletal networks. APC interacts with microtubules and accumulates at their plus ends in membrane protrusions. Also, it has been reported that APC is associated with the plasma membrane in an actin-dependent manner. Moreover, APC interacts with IQGAP1, an effector of Rac1 and Cdc42, and APC-stimulated guanine nucleotide exchange factor (Asef), a Rac1-specific guanine nucleotide exchange factor (GEF). IQGAP1 mediates association of APC with cortical actin in the leading edge of migrating cell and both proteins are required for cell polarization and directional migration. APC interacts with Asef and stimulates its activity, thereby regulating the actin cytoskeletal network, cell morphology, adhesion and migration. Truncated mutant APCs present in colorectal tumour cells activate Asef constitutively and contribute to their aberrant migratory properties, which may be important for adenoma formation as well as tumour progression to invasive malignancy.
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Affiliation(s)
- T Akiyama
- Laboratory of Molecular and Genetic Information, Institute for Molecular and Cellular Biosciences, The University of Tokyo, Bunkyo-ku, Tokyo, Japan.
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37
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Kroboth K, Newton IP, Kita K, Dikovskaya D, Zumbrunn J, Waterman-Storer CM, Näthke IS. Lack of adenomatous polyposis coli protein correlates with a decrease in cell migration and overall changes in microtubule stability. Mol Biol Cell 2006; 18:910-8. [PMID: 17192415 PMCID: PMC1805109 DOI: 10.1091/mbc.e06-03-0179] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
Most sporadic colorectal tumors carry truncation mutations in the adenomatous polyposis coli (APC) gene. The APC protein is involved in many processes that govern gut tissue. In addition to its involvement in the regulation of beta-catenin, APC is a cytoskeletal regulator with direct and indirect effects on microtubules. Cancer-related truncation mutations lack direct and indirect binding sites for microtubules in APC, suggesting that loss of this function contributes to defects in APC-mutant cells. In this study, we show that loss of APC results in disappearance of cellular protrusions and decreased cell migration. These changes are accompanied by a decrease in overall microtubule stability and also by a decrease in posttranslationally modified microtubules in the cell periphery particularly the migrating edge. Consistent with the ability of APC to affect cell shape, the overexpression of APC in cells can induce cellular protrusions. These data demonstrate that cell migration and microtubule stability are linked to APC status, thereby revealing a weakness in APC-deficient cells with potential therapeutic implications.
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Affiliation(s)
- Karin Kroboth
- *Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom; and
| | - Ian P. Newton
- *Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom; and
| | - Katsuhiro Kita
- Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037
| | - Dina Dikovskaya
- *Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom; and
| | - Jürg Zumbrunn
- *Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom; and
| | | | - Inke S. Näthke
- *Division of Cell and Developmental Biology, School of Life Sciences, University of Dundee, Dundee DD1 5EH, United Kingdom; and
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Langford KJ, Lee T, Askham JM, Morrison EE. Adenomatous polyposis coli localization is both cell type and cell context dependent. ACTA ACUST UNITED AC 2006; 63:483-92. [PMID: 16767746 DOI: 10.1002/cm.20139] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The adenomatous polyposis coli (APC) tumor suppressor protein is mutated in most colorectal carcinomas. In addition to its role in WNT signaling it is proposed to be involved in both cell migration and mitosis. Although a variety of studies have shown an APC localization along lateral membranes of adjacent epithelial cells the existence of a cortical APC localization in mammalian cells remains controversial. To address this we have used matched rat epithelial (NRK-52E) and fibroblast (NRK-49F) cell lines to investigate the localization of APC. Subconfluent cultures of NRK-52E and -49F cells displayed microtubule-associated APC populations by immunostaining. However, confluent NRK-52E, but not -49F monolayers, exhibited a cortical APC distribution. Cortical APC localized in close proximity to a number of cell junction proteins in a microtubule-independent manner while calcium switch experiments suggested that APC was recruited to the cortex only when junction assembly was complete. Confluent NRK-49F and -52E cells also showed contrasting APC localizations in response to monolayer wounding. Our data suggests APC cortical localization is a feature of confluent epithelioid cells and that the subcellular distribution of APC is therefore dependent upon both cell type and context.
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Affiliation(s)
- K J Langford
- CRUK Clinical Centre at Leeds, Division of Cancer Medicine Research, St James's University Hospital, UK.
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39
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Benhamouche S, Decaens T, Godard C, Chambrey R, Rickman DS, Moinard C, Vasseur-Cognet M, Kuo CJ, Kahn A, Perret C, Colnot S. Apc tumor suppressor gene is the "zonation-keeper" of mouse liver. Dev Cell 2006; 10:759-70. [PMID: 16740478 DOI: 10.1016/j.devcel.2006.03.015] [Citation(s) in RCA: 400] [Impact Index Per Article: 22.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2005] [Revised: 03/08/2006] [Accepted: 03/23/2006] [Indexed: 12/26/2022]
Abstract
The molecular mechanisms by which liver genes are differentially expressed along a portocentral axis, allowing for metabolic zonation, are poorly understood. We provide here compelling evidence that the Wnt/beta-catenin pathway plays a key role in liver zonation. First, we show the complementary localization of activated beta-catenin in the perivenous area and the negative regulator Apc in periportal hepatocytes. We then analyzed the immediate consequences of either a liver-inducible Apc disruption or a blockade of Wnt signaling after infection with an adenovirus encoding Dkk1, and we show that Wnt/beta-catenin signaling inversely controls the perivenous and periportal genetic programs. Finally, we show that genes involved in the periportal urea cycle and the perivenous glutamine synthesis systems are critical targets of beta-catenin signaling, and that perturbations to ammonia metabolism are likely responsible for the death of mice with liver-targeted Apc loss. From our results, we propose that Apc is the liver "zonation-keeper" gene.
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Affiliation(s)
- Samira Benhamouche
- Institut Cochin, Département GDPM, INSERM U567, CNRS, UMR-S 8104, Paris, F-75014, France
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40
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Krieghoff E, Behrens J, Mayr B. Nucleo-cytoplasmic distribution of beta-catenin is regulated by retention. J Cell Sci 2006; 119:1453-63. [PMID: 16554443 DOI: 10.1242/jcs.02864] [Citation(s) in RCA: 199] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
beta-catenin is the central signalling molecule of the canonical Wnt pathway, where it activates target genes in a complex with LEF/TCF transcription factors in the nucleus. The regulation of beta-catenin activity is thought to occur mainly on the level of protein degradation, but it has been suggested that beta-catenin nuclear localization and hence its transcriptional activity may additionally be regulated via nuclear import by TCF4 and BCL9 and via nuclear export by APC and axin. Using live-cell microscopy and fluorescence recovery after photobleaching (FRAP), we have directly analysed the impact of these factors on the subcellular localization of beta-catenin, its nucleo-cytoplasmic shuttling and its mobility within the nucleus and the cytoplasm. We show that TCF4 and BCL9/Pygopus recruit beta-catenin to the nucleus, and APC, axin and axin2 enrich beta-catenin in the cytoplasm. Importantly, however, none of these factors accelerates the nucleo-cytoplasmic shuttling of beta-catenin, i.e. increases the rate of beta-catenin nuclear import or export. Moreover, the cytoplasmic enrichment of beta-catenin by APC and axin is not abolished by inhibition of CRM-1-dependent nuclear export. TCF4, APC, axin and axin2 move more slowly than beta-catenin in their respective compartment, and concomitantly decrease beta-catenin mobility. Together, these data indicate that beta-catenin interaction partners mainly regulate beta-catenin subcellular localization by retaining it in the compartment in which they are localized, rather than by active transport into or out of the nucleus.
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Affiliation(s)
- Eva Krieghoff
- Nikolaus-Fiebiger-Center for Molecular Medicine, University of Erlangen-Nürnberg, Glückstr. 6, 91054 Erlangen, Germany
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41
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Yang J, Zhang W, Evans PM, Chen X, He X, Liu C. Adenomatous polyposis coli (APC) differentially regulates beta-catenin phosphorylation and ubiquitination in colon cancer cells. J Biol Chem 2006; 281:17751-7. [PMID: 16798748 DOI: 10.1074/jbc.m600831200] [Citation(s) in RCA: 165] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Most colorectal cancers have mutations of the adenomatous polyposis coli (APC) gene or the beta-catenin gene that stabilize beta-catenin and activate beta-catenin target genes, leading ultimately to cancer. The molecular mechanisms of APC function in beta-catenin degradation are not completely known. APC binds beta-catenin and is involved in the Axin complex, suggesting that APC regulates beta-catenin phosphorylation. Some evidence also suggests that APC regulates beta-catenin nuclear export. Here, we examine the effects of APC mutations on beta-catenin phosphorylation, ubiquitination, and degradation in the colon cancer cell lines SW480, DLD-1, and HT29, each of which contains a different APC truncation. Although the current models suggest that beta-catenin phosphorylation should be inhibited by APC mutations, we detected significant beta-catenin phosphorylation in these cells. However, beta-catenin ubiquitination and degradation were inhibited in SW480 but not in DLD-1 and HT29 cells. The ubiquitination ofbeta-catenin in SW480 cells can be rescued by exogenous expression of APC. The APC domains required for beta-catenin ubiquitination were analyzed. Our results suggest that APC regulates beta-catenin phosphorylation and ubiquitination by distinct domains and by separate molecular mechanisms.
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Affiliation(s)
- Jun Yang
- Sealy Center for Cancer Cell Biology and Department of Biochemistry and Molecular Biology, University of Texas Medical Branch, Galveston, TX 77555, USA
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42
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Sharma M, Leung L, Brocardo M, Henderson J, Flegg C, Henderson BR. Membrane localization of adenomatous polyposis coli protein at cellular protrusions: targeting sequences and regulation by beta-catenin. J Biol Chem 2006; 281:17140-17149. [PMID: 16621792 DOI: 10.1074/jbc.m513027200] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Adenomatous polyposis coli protein (APC) translocates to, and stabilizes, the plus-ends of microtubules. In microtubule-dependent cellular protrusions, APC frequently accumulates in peripheral clusters at the basal membrane. APC targeting to membrane clusters is important for cell migration, but the localization mechanism is poorly understood. In this study, we performed deletion mapping and defined a minimal sequence (amino acids 1-2226) that efficiently targets APC to membrane clusters. This sequence lacks DLG-1 and EB1 binding sites, suggesting that these partners are not absolutely required for APC membrane targeting. A series of APC sequences were transiently expressed in cells and compared for their ability to compete endogenous APC at the membrane; potent inhibition of endogenous APC targeting was elicited by the Armadillo- (binds KAP3A, B56alpha, and ASEF) and beta-catenin-binding domains. The Armadillo domain was predicted to inhibit APC membrane localization through sequestration of the kinesin-KAP3A complex. The role of beta-catenin in APC membrane localization was unexpected but affirmed by overexpressing the APC binding sequence of beta-catenin, which similarly reduced APC membrane staining. Furthermore, we used RNA interference to show that loss of beta-catenin reduced APC at membrane clusters in migrating cells. In addition, we report that transiently expressed APC-yellow fluorescent protein co-localized with beta-catenin, KAP3A, EB1, and DLG-1 at membrane clusters, but only beta-catenin stimulated APC anchorage at the membrane. Our findings identify beta-catenin as a regulator of APC targeting to membrane clusters and link these two proteins to cell migration.
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Affiliation(s)
- Manisha Sharma
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia
| | - Louie Leung
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia
| | - Mariana Brocardo
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia
| | - Jasmine Henderson
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia
| | - Cameron Flegg
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia
| | - Beric R Henderson
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, Westmead, New South Wales 2145, Australia.
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Langford KJ, Askham JM, Lee T, Adams M, Morrison EE. Examination of actin and microtubule dependent APC localisations in living mammalian cells. BMC Cell Biol 2006; 7:3. [PMID: 16423286 PMCID: PMC1386658 DOI: 10.1186/1471-2121-7-3] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Accepted: 01/19/2006] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The trafficking of the adenomatous polyposis coli (APC) tumour suppressor protein in mammalian cells is a perennially controversial topic. Immunostaining evidence for an actin-associated APC localisation at intercellular junctions has been previously presented, though live imaging of mammalian junctional APC has not been documented. RESULTS Using live imaging of transfected COS-7 cells we observed intercellular junction-associated pools of GFP-APC in addition to previously documented microtubule-associated GFP-APC and a variety of minor localisations. Although both microtubule and junction-associated populations could co-exist within individual cells, they differed in their subcellular location, dynamic behaviour and sensitivity to cytoskeletal poisons. GFP-APC deletion mutant analysis indicated that a protein truncated immediately after the APC armadillo repeat domain retained the ability to localise to adhesive membranes in transfected cells. Supporting this, we also observed junctional APC immunostaining in cultures of human colorectal cancer cell line that express truncated forms of APC. CONCLUSION Our data indicate that APC can be found in two spatially separate populations at the cell periphery and these populations can co-exist in the same cell. The first localisation is highly dynamic and associated with microtubules near free edges and in cell vertices, while the second is comparatively static and is closely associated with actin at sites of cell-cell contact. Our imaging confirms that human GFP-APC possesses many of the localisations and behaviours previously seen by live imaging of Xenopus GFP-APC. However, we report the novel finding that GFP-APC puncta can remain associated with the ends of shrinking microtubules. Deletion analysis indicated that the N-terminal region of the APC protein mediated its junctional localisation, consistent with our observation that truncated APC proteins in colon cancer cell lines are still capable of localising to the cell cortex. This may have implications for the development of colorectal cancer.
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Affiliation(s)
- Kelly J Langford
- CRUK Clinical Centre at Leeds, Division of Cancer Medicine Research, St James's University Hospital, Leeds, LS9 7TF, UK
| | - Jon M Askham
- CRUK Clinical Centre at Leeds, Division of Cancer Medicine Research, St James's University Hospital, Leeds, LS9 7TF, UK
| | - Tracy Lee
- CRUK Clinical Centre at Leeds, Division of Cancer Medicine Research, St James's University Hospital, Leeds, LS9 7TF, UK
| | - Matthew Adams
- CRUK Clinical Centre at Leeds, Division of Cancer Medicine Research, St James's University Hospital, Leeds, LS9 7TF, UK
| | - Ewan E Morrison
- CRUK Clinical Centre at Leeds, Division of Cancer Medicine Research, St James's University Hospital, Leeds, LS9 7TF, UK
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44
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Catimel B, Nice EC, Kärrlander M, Ross J, Catimel J, Burgess AW, Faux M. Purification and characterization of a high specificity polyclonal antibody to the adenomatous polyposis coli tumour suppressor protein. Biomed Chromatogr 2006; 20:569-75. [PMID: 16779787 DOI: 10.1002/bmc.648] [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: 12/21/2022]
Abstract
Recombinant proteins, commonly expressed in fusion with an affinity tag to facilitate purification, are often used as immunogens for polyclonal antibody production. Careful immunopurification of the antibody product is often the key to obtaining a high-specificity polyclonal antibody against the protein domain of interest. This study describes the purification and characterization of such an antibody directed against the adenomatous polyposis coli (APC) tumour suppressor. We used a combination of affinity chromatography and biosensor analysis to optimize and monitor antibody purification. This antibody was then characterized by immunoprecipitation, proteomic analyses and immunofluorescence staining and shown to be a valuable reagent for the study of APC biology. Using this antibody we successfully isolated and identified APC, using MS/MS, from transfected cell lines. A novel phosphorylation site on APC was identified at ser 1436. Similar strategies involving multiple immuno-affinity steps coupled with surface plasmon resonance (SPR), immunoprecipitation proteomic and immunofluorescence analyses should be generally applicable for the purification and characterization of other polyclonal antibodies.
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Affiliation(s)
- Bruno Catimel
- Ludwig Institute for Cancer Research, PO Royal Melbourne Hospital, Parkville, Victoria, Australia
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45
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Abstract
The role of wild-type adenomatous polyposis coli (APC) protein in native epithelia is poorly understood. The present study examined the relationships between wild-type APC and beta-catenin expression in an established model of hyperproliferation, transmissible murine colonic hyperplasia (TMCH). Distal colonic crypts isolated from normal or TMCH mice were: (i) fractionated into cytosolic and nuclear components for Western blotting and immunoprecipitation (IP), (ii) extracted for total RNA isolation for Northern blotting and, (iii) analysed immunohistochemically by confocal microscopy. Western blots performed sequentially through day 12 TMCH with N-terminal APC antibodies revealed increased abundance of approximately 312 kDa (p312) protein by day 6 (4.0 +/- 0.75-fold, n = 6) that peaked by day 9, before declining by day 12. A approximately 130 kDa (p130) band appeared at day 9 and increased by day 12 (1.5 +/- 0.11-fold, n = 6). A C-terminal antibody detected only p312. APC mRNA level did not change during TMCH and appearance of p130 was not due to alternative splicing. Co-IP with N-terminal anti-APC antibodies, revealed APC's association with beta-catenin both at day 6 and day 12. p130, but not p312, associated predominantly with beta-catenin at day 12 during co-IP with anti-beta-catenin. p130 also selectively accumulated in the nucleus, bound to nuclear beta-catenin at day 12. Immunocytochemistry with N-terminal antibodies revealed an increasing crypt base : surface gradient of APC within the apical pole/apical-lateral membranes at day 6. At day 12, intense apical/cytoplasmic and occasional nuclear staining along the longitudinal crypt axis was observed. Full-length APC increases during epithelial hyperproliferation and may represent a homoeostatic response. The dramatic increase in cytoplasmic and sporadic nuclear APC staining at day 12 with N-terminal antibodies may represent p130. The nuclear accumulation of p130 may be a novel mechanism regulating nuclear beta-catenin function during TMCH.
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Affiliation(s)
- Shahid Umar
- Department of Internal Medicine, Division of Gastroenterology and Hepatology, University of Texas Medical Branch, Galveston, 77555-0632, USA.
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46
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Näthke I. Relationship between the role of the adenomatous polyposis coli protein in colon cancer and its contribution to cytoskeletal regulation. Biochem Soc Trans 2005; 33:694-7. [PMID: 16042576 DOI: 10.1042/bst0330694] [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] [Indexed: 12/18/2022]
Abstract
A unique feature of colon cancer is that truncation mutations in the APC (adenomatous polyposis coli) gene are common to most tumours. The high penetrance of APC mutations, especially in gut epithelium, supports the idea that APC may be involved in a number of the processes that govern the normal maintenance of this tissue: differentiation, migration, proliferation and apoptosis. Indeed, APC is involved in the regulation of β-catenin and it also is an important regulator of the cytoskeleton. Thus mutations in APC lead to the accumulation of β-catenin, which causes changes in differentiation, and they also produce changes in cytoskeletal organization, which results in altered cell migration and disrupted mitotic spindles. The function of APC in cytoskeletal organization is related to its effect on microtubules and F-actin. Depleting APC from cultured cells leads to changes in cytoskeletal organization. In addition, N-terminal fragments of APC, like those commonly found in tumours, compromise cell migration in Dictyostelium and in early developing chicken embryos. Consistent with the idea that such dominant effects are normally balanced by interactions within the full-length molecule, protein interactions of N-terminal fragments expressed in tumour cells can be altered by binding to C-terminal regions of APC commonly lost in tumours. This review summarizes effects of APC on the cytoskeleton and discusses how these functions of APC may contribute to its role in cancer.
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Affiliation(s)
- I Näthke
- Cell and Developmental Biology, University of Dundee, Dow Street, Dundee DD1 5EH, Scotland, UK.
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47
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Abstract
The subcellular location and function of many proteins are regulated by nuclear-cytoplasmic shuttling. BRCA1 and BARD1 provide an interesting model system for understanding the influence of protein dimerization on nuclear transport and localization. These proteins function predominantly in the nucleus to regulate cell cycle progression, DNA repair/recombination and gene transcription, and their export to the cytoplasm has been linked to apoptosis. Germ-line mutations in the BRCA1/BRCA2 and BARD1 genes predispose to risk of breast/ovarian cancer, and certain mutations impair protein function and nuclear accumulation. BRCA1 and BARD1 shuttle between the nucleus and cytoplasm; however heterodimerization masks the nuclear export signals located within each protein, causing nuclear retention of the BRCA1-BARD1 complex and potentially influencing its role in DNA repair, cell survival and regulation of centrosome duplication. This review discusses BRCA1, BRCA2 and BARD1 subcellular localization with emphasis on regulation of transport by protein dimerization and its functional implications.
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Affiliation(s)
- Beric R Henderson
- Westmead Institute for Cancer Research, University of Sydney, Westmead Millennium Institute at Westmead Hospital, New South Wales, Australia.
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