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Sadeqzadeh E, de Bock CE, Wojtalewicz N, Holt JE, Smith ND, Dun MD, Schwarte-Waldhoff I, Thorne RF. Furin processing dictates ectodomain shedding of human FAT1 cadherin. Exp Cell Res 2014; 323:41-55. [PMID: 24560745 DOI: 10.1016/j.yexcr.2014.02.012] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2013] [Revised: 01/09/2014] [Accepted: 02/04/2014] [Indexed: 10/25/2022]
Abstract
Fat1 is a single pass transmembrane protein and the largest member of the cadherin superfamily. Mouse knockout models and in vitro studies have suggested that Fat1 influences cell polarity and motility. Fat1 is also an upstream regulator of the Hippo pathway, at least in lower vertebrates, and hence may play a role in growth control. In previous work we have established that FAT1 cadherin is initially cleaved by proprotein convertases to form a noncovalently linked heterodimer prior to expression on the cell surface. Such processing was not a requirement for cell surface expression, since melanoma cells expressed both unprocessed FAT1 and the heterodimer on the cell surface. Here we further establish that the site 1 (S1) cleavage step to promote FAT1 heterodimerisation is catalysed by furin and we identify the cleavage site utilised. For a number of other transmembrane receptors that undergo heterodimerisation the S1 processing step is thought to occur constitutively but the functional significance of heterodimerisation has been controversial. It has also been generally unclear as to the significance of receptor heterodimerisation with respect to subsequent post-translational proteolysis that often occurs in transmembrane proteins. Exploiting the partial deficiency of FAT1 processing in melanoma cells together with furin-deficient LoVo cells, we manipulated furin expression to demonstrate that only the heterodimer form of FAT1 is subject to cleavage and subsequent release of the extracellular domain. This work establishes S1-processing as a clear functional prerequisite for ectodomain shedding of FAT1 with general implications for the shedding of other transmembrane receptors.
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Affiliation(s)
- Elham Sadeqzadeh
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia
| | - Charles E de Bock
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia
| | - Natalie Wojtalewicz
- Department of Internal Medicine, Knappschaftskrankenhaus, Ruhr-University Bochum, Bochum, Germany
| | - Janet E Holt
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Nathan D Smith
- ABRF, Research Services, University of Newcastle, Callaghan, NSW 2308, Australia
| | - Matthew D Dun
- School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia; Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia; Hunter Translational Cancer Research Unit, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia
| | | | - Rick F Thorne
- Hunter Medical Research Institute, New Lambton Heights, NSW 2305, Australia; Hunter Translational Cancer Research Unit, School of Biomedical Sciences and Pharmacy, University of Newcastle, Callaghan, NSW 2308, Australia; School of Environmental & Life Sciences, University of Newcastle, Callaghan, New South Wales, Australia.
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52
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Southan C, Hancock JM. A tale of two drug targets: the evolutionary history of BACE1 and BACE2. Front Genet 2013; 4:293. [PMID: 24381583 PMCID: PMC3865767 DOI: 10.3389/fgene.2013.00293] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2013] [Accepted: 11/29/2013] [Indexed: 11/22/2022] Open
Abstract
The beta amyloid (APP) cleaving enzyme (BACE1) has been a drug target for Alzheimer's Disease (AD) since 1999 with lead inhibitors now entering clinical trials. In 2011, the paralog, BACE2, became a new target for type II diabetes (T2DM) having been identified as a TMEM27 secretase regulating pancreatic β cell function. However, the normal roles of both enzymes are unclear. This study outlines their evolutionary history and new opportunities for functional genomics. We identified 30 homologs (UrBACEs) in basal phyla including Placozoans, Cnidarians, Choanoflagellates, Porifera, Echinoderms, Annelids, Mollusks and Ascidians (but not Ecdysozoans). UrBACEs are predominantly single copy, show 35-45% protein sequence identity with mammalian BACE1, are ~100 residues longer than cathepsin paralogs with an aspartyl protease domain flanked by a signal peptide and a C-terminal transmembrane domain. While multiple paralogs in Trichoplax and Monosiga pre-date the nervous system, duplication of the UrBACE in fish gave rise to BACE1 and BACE2 in the vertebrate lineage. The latter evolved more rapidly as the former maintained the emergent neuronal role. In mammals, Ka/Ks for BACE2 is higher than BACE1 but low ratios for both suggest purifying selection. The 5' exons show higher Ka/Ks than the catalytic section. Model organism genomes show the absence of certain BACE human substrates when the UrBACE is present. Experiments could thus reveal undiscovered substrates and roles. The human protease double-target status means that evolutionary trajectories and functional shifts associated with different substrates will have implications for the development of clinical candidates for both AD and T2DM. A rational basis for inhibition specificity ratios and assessing target-related side effects will be facilitated by a more complete picture of BACE1 and BACE2 functions informed by their evolutionary context.
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Affiliation(s)
- Christopher Southan
- IUPHAR Database and Guide to Pharmacology Web Portal Group, University/BHF Centre for Cardiovascular Science, Queen's Medical Research Institute, University of EdinburghEdinburgh, UK
| | - John M. Hancock
- Department of Physiology, Development and Neuroscience, University of CambridgeCambridge, UK
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Abstract
To date, 18 distinct receptor tyrosine kinases (RTKs) are reported to be trafficked from the cell surface to the nucleus in response to ligand binding or heterologous agonist exposure. In most cases, an intracellular domain (ICD) fragment of the receptor is generated at the cell surface and translocated to the nucleus, whereas for a few others the intact receptor is translocated to the nucleus. ICD fragments are generated by several mechanisms, including proteolysis, internal translation initiation, and messenger RNA (mRNA) splicing. The most prevalent mechanism is intramembrane cleavage by γ-secretase. In some cases, more than one mechanism has been reported for the nuclear localization of a specific RTK. The generation and use of RTK ICD fragments to directly communicate with the nucleus and influence gene expression parallels the production of ICD fragments by a number of non-RTK cell-surface molecules that also influence cell proliferation. This review will be focused on the individual RTKs and to a lesser extent on other growth-related cell-surface transmembrane proteins.
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Affiliation(s)
- Graham Carpenter
- Department of Biochemistry, Vanderbilt University School of Medicine, Nashville, Tennessee 37232-0146
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Smolarkiewicz M, Skrzypczak T, Wojtaszek P. The very many faces of presenilins and the γ-secretase complex. PROTOPLASMA 2013; 250:997-1011. [PMID: 23504135 PMCID: PMC3788181 DOI: 10.1007/s00709-013-0494-y] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2013] [Accepted: 03/01/2013] [Indexed: 05/02/2023]
Abstract
Presenilin is a central, catalytic component of the γ-secretase complex which conducts intramembrane cleavage of various protein substrates. Although identified and mainly studied through its role in the development of amyloid plaques in Alzheimer disease, γ-secretase has many other important functions. The complex seems to be evolutionary conserved throughout the Metazoa, but recent findings in plants and Dictyostelium discoideum as well as in archeons suggest that its evolution and functions might be much more diversified than previously expected. In this review, a selective survey of the multitude of functions of presenilins and the γ-secretase complex is presented. Following a brief overview of γ-secretase structure, assembly and maturation, three functional aspects are analyzed: (1) the role of γ-secretase in autophagy and phagocytosis; (2) involvement of the complex in signaling related to endocytosis; and (3) control of calcium fluxes by presenilins.
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Affiliation(s)
- Michalina Smolarkiewicz
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Tomasz Skrzypczak
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
| | - Przemysław Wojtaszek
- Department of Molecular and Cellular Biology, Faculty of Biology, Adam Mickiewicz University, Umultowska 89, 61-614 Poznań, Poland
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55
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Sandoval PC, Slentz DH, Pisitkun T, Saeed F, Hoffert JD, Knepper MA. Proteome-wide measurement of protein half-lives and translation rates in vasopressin-sensitive collecting duct cells. J Am Soc Nephrol 2013; 24:1793-805. [PMID: 24029424 DOI: 10.1681/asn.2013030279] [Citation(s) in RCA: 87] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
Vasopressin regulates water excretion, in part, by controlling the abundances of the water channel aquaporin-2 (AQP2) protein and regulatory proteins in the renal collecting duct. To determine whether vasopressin-induced alterations in protein abundance result from modulation of protein production, protein degradation, or both, we used protein mass spectrometry with dynamic stable isotope labeling in cell culture to achieve a proteome-wide determination of protein half-lives and relative translation rates in mpkCCD cells. Measurements were made at steady state in the absence or presence of the vasopressin analog, desmopressin (dDAVP). Desmopressin altered the translation rate rather than the stability of most responding proteins, but it significantly increased both the translation rate and the half-life of AQP2. In addition, proteins associated with vasopressin action, including Mal2, Akap12, gelsolin, myosin light chain kinase, annexin-2, and Hsp70, manifested altered translation rates. Interestingly, desmopressin increased the translation of seven glutathione S-transferase proteins and enhanced protein S-glutathionylation, uncovering a previously unexplored vasopressin-induced post-translational modification. Additional bioinformatic analysis of the mpkCCD proteome indicated a correlation between protein function and protein half-life. In particular, processes that are rapidly regulated, such as transcription, endocytosis, cell cycle regulation, and ubiquitylation are associated with proteins with especially short half-lives. These data extend our understanding of the mechanisms underlying vasopressin signaling and provide a broad resource for additional investigation of collecting duct function (http://helixweb.nih.gov/ESBL/Database/ProteinHalfLives/index.html).
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Affiliation(s)
- Pablo C Sandoval
- Epithelial Systems Biology Laboratory, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland
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56
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Hachmeister M, Bobowski KD, Hogl S, Dislich B, Fukumori A, Eggert C, Mack B, Kremling H, Sarrach S, Coscia F, Zimmermann W, Steiner H, Lichtenthaler SF, Gires O. Regulated intramembrane proteolysis and degradation of murine epithelial cell adhesion molecule mEpCAM. PLoS One 2013; 8:e71836. [PMID: 24009667 PMCID: PMC3756971 DOI: 10.1371/journal.pone.0071836] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2013] [Accepted: 07/03/2013] [Indexed: 01/28/2023] Open
Abstract
Epithelial cell adhesion molecule EpCAM is a transmembrane glycoprotein, which is highly and frequently expressed in carcinomas and (cancer-)stem cells, and which plays an important role in the regulation of stem cell pluripotency. We show here that murine EpCAM (mEpCAM) is subject to regulated intramembrane proteolysis in various cells including embryonic stem cells and teratocarcinomas. As shown with ectopically expressed EpCAM variants, cleavages occur at α-, β-, γ-, and ε-sites to generate soluble ectodomains, soluble Aβ-like-, and intracellular fragments termed mEpEX, mEp-β, and mEpICD, respectively. Proteolytic sites in the extracellular part of mEpCAM were mapped using mass spectrometry and represent cleavages at the α- and β-sites by metalloproteases and the b-secretase BACE1, respectively. Resulting C-terminal fragments (CTF) are further processed to soluble Aβ-like fragments mEp-β and cytoplasmic mEpICD variants by the g-secretase complex. Noteworthy, cytoplasmic mEpICD fragments were subject to efficient degradation in a proteasome-dependent manner. In addition the γ-secretase complex dependent cleavage of EpCAM CTF liberates different EpICDs with different stabilities towards proteasomal degradation. Generation of CTF and EpICD fragments and the degradation of hEpICD via the proteasome were similarly demonstrated for the human EpCAM ortholog. Additional EpCAM orthologs have been unequivocally identified in silico in 52 species. Sequence comparisons across species disclosed highest homology of BACE1 cleavage sites and in presenilin-dependent γ-cleavage sites, whereas strongest heterogeneity was observed in metalloprotease cleavage sites. In summary, EpCAM is a highly conserved protein present in fishes, amphibians, reptiles, birds, marsupials, and placental mammals, and is subject to shedding, γ-secretase-dependent regulated intramembrane proteolysis, and proteasome-mediated degradation.
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Affiliation(s)
- Matthias Hachmeister
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Karolina D. Bobowski
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Sebastian Hogl
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Bastian Dislich
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Technische Universität München, Munich, Germany
| | - Akio Fukumori
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
| | - Carola Eggert
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Brigitte Mack
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Heidi Kremling
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Sannia Sarrach
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Fabian Coscia
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
| | - Wolfgang Zimmermann
- Tumor Immunology Laboratory, LIFE Center, Klinikum Grosshadern, Ludwig-Maximilians-University, Munich, Germany
| | - Harald Steiner
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Adolf Butenandt Institute, Biochemistry, Ludwig Maximilians University, Munich, Germany
| | - Stefan F. Lichtenthaler
- German Center for Neurodegenerative Diseases (DZNE), Munich, Germany
- Technische Universität München, Munich, Germany
- Munich Center for Systems Neurology (SyNergy), Munich, Germany
| | - Olivier Gires
- Department of Otorhinolaryngology, Head and Neck Surgery, Ludwig-Maximilians-University, Munich, Germany
- * E-mail:
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57
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Raikwar NS, Liu KZ, Thomas CP. Protein kinase C regulates FLT1 abundance and stimulates its cleavage in vascular endothelial cells with the release of a soluble PlGF/VEGF antagonist. Exp Cell Res 2013; 319:2578-87. [PMID: 23911939 DOI: 10.1016/j.yexcr.2013.07.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2013] [Revised: 06/25/2013] [Accepted: 07/09/2013] [Indexed: 01/18/2023]
Abstract
FLT1 and its soluble form (sFLT1) arise as alternate transcripts from the same gene and sFLT1 can antagonize the effect of vascular endothelial growth factor (VEGF) on its cognate receptors. We investigated the effect of VEGF and protein kinase C (PKC) activation on sFLT1 abundance. We demonstrated that VEGF stimulates sFLT1 and FLT1 mRNA and protein levels in vascular endothelial cells via VEGFR2 and PKC. Using an FLT1 expression vector with N and C-terminal epitope tags, we show that PKC activation increases the cleavage of FLT1 into an N-terminal extracellular fragment and a C-terminal intracellular fragment with the cleavage occurring adjacent to the transmembrane domain. The trafficking and glycosylation inhibitors brefeldin, monensin and tunicamycin substantially reduced cleavage and release of the N-terminal ectodomain of FLT1 and inhibited secretion of the isoforms of sFLT1. The shed FLT1 ectodomain can bind VEGF and PlGF and inhibit VEGF-induced vascular tube formation thus confirming that it is functionally equivalent to the alternately spliced and secreted sFLT1 isoforms.
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Affiliation(s)
- Nandita S Raikwar
- Department of Internal Medicine, University of Iowa College of Medicine, Iowa City, IA, USA
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Sulindac modulates secreted protein expression from LIM1215 colon carcinoma cells prior to apoptosis. BIOCHIMICA ET BIOPHYSICA ACTA-PROTEINS AND PROTEOMICS 2013; 1834:2293-307. [PMID: 23899461 DOI: 10.1016/j.bbapap.2013.07.007] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/18/2012] [Revised: 07/03/2013] [Accepted: 07/18/2013] [Indexed: 11/21/2022]
Abstract
Colorectal cancer (CRC) is a major cause of mortality in Western populations. Growing evidence from human and rodent studies indicate that nonsteroidal anti-inflammatory drugs (NSAIDs) cause regression of existing colon tumors and act as effective chemopreventive agents in sporadic colon tumor formation. Although much is known about the action of the NSAID sulindac, especially its role in inducing apoptosis, mechanisms underlying these effects is poorly understood. In previous secretome-based proteomic studies using 2D-DIGE/MS and cytokine arrays we identified over 150 proteins released from the CRC cell line LIM1215 whose expression levels were dysregulated by treatment with 1mM sulindac over 16h; many of these proteins are implicated in molecular and cellular functions such as cell proliferation, differentiation, adhesion, angiogenesis and apoptosis (Ji et al., Proteomics Clin. Appl. 2009, 3, 433-451). We have extended these studies and describe here an improved protein/peptide separation strategy that facilitated the identification of 987 proteins and peptides released from LIM1215 cells following 1mM sulindac treatment for 8h preceding the onset of apoptosis. This peptidome separation strategy involved fractional centrifugal ultrafiltration of concentrated cell culture media (CM) using nominal molecular weight membrane filters (NMWL 30K, 3K and 1K). Proteins isolated in the >30K and 3-30K fractions were electrophoretically separated by SDS-PAGE and endogenous peptides in the 1-3K membrane filter were fractioned by RP-HPLC; isolated proteins and peptides were identified by nanoLC-MS-MS. Collectively, our data show that LIM1215 cells treated with 1mM sulindac for 8h secrete decreased levels of proteins associated with extracellular matrix remodeling (e.g., collagens, perlecan, syndecans, filamins, dyneins, metalloproteinases and endopeptidases), cell adhesion (e.g., cadherins, integrins, laminins) and mucosal maintenance (e.g., glycoprotein 340 and mucins 5AC, 6, and 13). A salient finding of this study was the increased proteolysis of cell surface proteins following treatment with sulindac for 8h (40% higher than from untreated LIM1215 cells); several of these endogenous peptides contained C-terminal amino acids from transmembrane domains indicative of regulated intramembrane proteolysis (RIP). Taken together these results indicate that during the early-stage onset of sulindac-induced apoptosis (evidenced by increased annexin V binding, dephosphorylation of focal adhesion kinase (FAK), and cleavage of caspase-3), 1mM sulindac treatment of LIM1215 cells results in decreased expression of secreted proteins implicated in ECM remodeling, mucosal maintenance and cell-cell-adhesion. This article is part of a Special Issue entitled: An Updated Secretome.
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Dual cleavage of neuregulin 1 type III by BACE1 and ADAM17 liberates its EGF-like domain and allows paracrine signaling. J Neurosci 2013; 33:7856-69. [PMID: 23637177 DOI: 10.1523/jneurosci.3372-12.2013] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Proteolytic shedding of cell surface proteins generates paracrine signals involved in numerous signaling pathways. Neuregulin 1 (NRG1) type III is involved in myelination of the peripheral nervous system, for which it requires proteolytic activation by proteases of the ADAM family and BACE1. These proteases are major therapeutic targets for the prevention of Alzheimer's disease because they are also involved in the proteolytic generation of the neurotoxic amyloid β-peptide. Identification and functional investigation of their physiological substrates is therefore of greatest importance in preventing unwanted side effects. Here we investigated proteolytic processing of NRG1 type III and demonstrate that the ectodomain can be cleaved by three different sheddases, namely ADAM10, ADAM17, and BACE1. Surprisingly, we not only found cleavage by ADAM10, ADAM17, and BACE1 C-terminal to the epidermal growth factor (EGF)-like domain, which is believed to play a pivotal role in signaling, but also additional cleavage sites for ADAM17 and BACE1 N-terminal to that domain. Proteolytic processing at N- and C-terminal sites of the EGF-like domain results in the secretion of this domain from NRG1 type III. The soluble EGF-like domain is functionally active and stimulates ErbB3 signaling in tissue culture assays. Moreover, the soluble EGF-like domain is capable of rescuing hypomyelination in a zebrafish mutant lacking BACE1. Our data suggest that NRG1 type III-dependent myelination is not only controlled by membrane-retained NRG1 type III, but also in a paracrine manner via proteolytic liberation of the EGF-like domain.
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60
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The activity of σV, an extracytoplasmic function σ factor of Bacillus subtilis, is controlled by regulated proteolysis of the anti-σ factor RsiV. J Bacteriol 2013; 195:3135-44. [PMID: 23687273 DOI: 10.1128/jb.00292-13] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
During growth in the environment, bacteria encounter stresses which can delay or inhibit their growth. To defend against these stresses, bacteria induce both resistance and repair mechanisms. Many bacteria regulate these resistance mechanisms using a group of alternative σ factors called extracytoplasmic function (ECF) σ factors. ECF σ factors represent the largest and most diverse family of σ factors. Here, we demonstrate that the activation of a member of the ECF30 subfamily of ECF σ factors, σ(V) in Bacillus subtilis, is controlled by the proteolytic destruction of the anti-σ factor RsiV. We will demonstrate that the degradation of RsiV and, thus, the activation of σ(V) requires multiple proteolytic steps. Upon exposure to the inducer lysozyme, the extracellular domain of RsiV is removed by an unknown protease, which cleaves at site 1. This cleavage is independent of PrsW, the B. subtilis site 1 protease, which cleaves the anti-σ factor RsiW. Following cleavage by the unknown protease, the N-terminal portion of RsiV requires further processing, which requires the site 2 intramembrane protease RasP. Our data indicate that the N-terminal portion of RsiV from amino acid 1 to 60, which lacks the extracellular domain, is constitutively degraded unless RasP is absent, indicating that RasP cleavage is constitutive. This suggests that the regulatory step in RsiV degradation and, thus, σ(V) activation are controlled at the level of the site 1 cleavage. Finally, we provide evidence that increased resistance to lysozyme decreases σ(V) activation. Collectively, these data provide evidence that the mechanism for σ(V) activation in B. subtilis is controlled by regulated intramembrane proteolysis (RIP) and requires the site 2 protease RasP.
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61
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Hayakawa E, Landuyt B, Baggerman G, Cuyvers R, Lavigne R, Luyten W, Schoofs L. Peptidomic analysis of human reflex tear fluid. Peptides 2013; 42:63-9. [PMID: 23228955 DOI: 10.1016/j.peptides.2012.11.018] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/18/2012] [Revised: 11/20/2012] [Accepted: 11/20/2012] [Indexed: 12/19/2022]
Abstract
Tear fluid is a complex mixture of biological compounds, including carbohydrates, lipids, electrolytes, proteins, and peptides. Despite the physiological importance of tear fluid, little is known about the identity of its endogenous peptides. In this study, we analyzed and identified naturally occurring peptide molecules in human reflex tear fluid by means of LC-MALDI-TOF-TOF. Tandem MS analyses revealed 30 peptides, most of which have not been identified before. Twenty-six peptides are derived from the proline-rich protein 4 and 4 peptides are derived from the polymeric immunoglobulin receptor. Based on their structural characteristics, we suggest that the identified tear fluid peptides contribute to the protective environment of the ocular surface.
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Affiliation(s)
- Eisuke Hayakawa
- Research Group of Functional Genomics and Proteomics, KU Leuven, B-3000 Leuven, Belgium.
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62
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Tveten K, Str M TB, Berge KE, Leren TP. PCSK9-mediated degradation of the LDL receptor generates a 17 kDa C-terminal LDL receptor fragment. J Lipid Res 2013; 54:1560-1566. [PMID: 23509406 DOI: 10.1194/jlr.m034371] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Proprotein convertase subtilisin/kexin type 9 (PCSK9) binds to the LDL receptor (LDLR) at the cell surface and reroutes the internalized LDLR to intracellular degradation. In this study, we have shown that PCSK9-mediated degradation of the full-length 160 kDa LDLR generates a 17 kDa C-terminal LDLR fragment. This fragment was not generated from mutant LDLRs resistant to PCSK9-mediated degradation or when degradation was prevented by chemicals such as ammonium chloride or the cysteine cathepsin inhibitor E64d. The observation that the 17 kDa fragment was only detected when the cells were cultured in the presence of the γ-secretase inhibitor DAPT indicates that this 17 kDa fragment undergoes γ-secretase cleavage within the transmembrane domain. The failure to detect the complementary 143 kDa ectodomain fragment is likely to be due to its rapid degradation in the endosomal lumen. The 17 kDa C-terminal LDLR fragment was also generated from a Class 5 mutant LDLR undergoing intracellular degradation. Thus, one may speculate that an LDLR with bound PCSK9 and a Class 5 LDLR with bound LDL are degraded by a similar mechanism that could involve ectodomain cleavage in the endosome.
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Affiliation(s)
- Kristian Tveten
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Thea Bismo Str M
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Knut Erik Berge
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway
| | - Trond P Leren
- Department of Medical Genetics, Oslo University Hospital Rikshospitalet, Oslo, Norway.
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63
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Castelli M, Piobbico D, Bartoli D, Pieroni S, Brunacci C, Bellet MM, Chiacchiaretta M, Della Fazia MA, Servillo G. Different functions of HOPS isoforms in the cell: HOPS shuttling isoform is determined by RIP cleavage system. Cell Cycle 2013; 13:293-302. [PMID: 24240191 DOI: 10.4161/cc.27054] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
Hepatocyte odd protein shuttling (HOPS) moves between nucleus and cytoplasm. HOPS overexpression leads to cell cycle arrest in G 0/G 1, and HOPS knockdown causes centrosome alterations, with subsequent abnormal cell division. Recently, we demonstrated that HOPS acts as a functional bridge in NPM-p19(Arf) interactions. Here we show that HOPS is present in 3 different isoforms that play distinct intracellular functions. Although HOPS is a transmembrane ubiquitin, an isoform with intermediate molecular weight is cleaved from the membrane and released into the cytosol, to act as the shuttling protein. We identified a signal peptide peptidase structure in N-terminal membrane-bound HOPS that allows the regulated intramembrane proteolysis (RIP) system to control the relative amounts of the released, shuttling isoform capable of binding NPM. These results argue for distinct, isoform-specific functions of HOPS in the nucleolus, nucleus, and cytoplasm and provide insight into the dynamics of HOPS association with NPM, whose mutation and subsequent delocalization is found in 30% of acute myeloid leukemia patients.
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Affiliation(s)
- Marilena Castelli
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
| | - Danilo Piobbico
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
| | - Daniela Bartoli
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
| | - Stefania Pieroni
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
| | - Cinzia Brunacci
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
| | - Marina Maria Bellet
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
| | | | | | - Giuseppe Servillo
- Department of Clinical and Experimental Medicine; University of Perugia; Perugia, Italy
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Biogenesis of the Saccharomyces cerevisiae pheromone a-factor, from yeast mating to human disease. Microbiol Mol Biol Rev 2013; 76:626-51. [PMID: 22933563 DOI: 10.1128/mmbr.00010-12] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
The mating pheromone a-factor secreted by Saccharomyces cerevisiae is a farnesylated and carboxylmethylated peptide and is unusually hydrophobic compared to other extracellular signaling molecules. Mature a-factor is derived from a precursor with a C-terminal CAAX motif that directs a series of posttranslational reactions, including prenylation, endoproteolysis, and carboxylmethylation. Historically, a-factor has served as a valuable model for the discovery and functional analysis of CAAX-processing enzymes. In this review, we discuss the three modules comprising the a-factor biogenesis pathway: (i) the C-terminal CAAX-processing steps carried out by Ram1/Ram2, Ste24 or Rce1, and Ste14; (ii) two sequential N-terminal cleavage steps, mediated by Ste24 and Axl1; and (iii) export by a nonclassical mechanism, mediated by the ATP binding cassette (ABC) transporter Ste6. The small size and hydrophobicity of a-factor present both challenges and advantages for biochemical analysis, as discussed here. The enzymes involved in a-factor biogenesis are conserved from yeasts to mammals. Notably, studies of the zinc metalloprotease Ste24 in S. cerevisiae led to the discovery of its mammalian homolog ZMPSTE24, which cleaves the prenylated C-terminal tail of the nuclear scaffold protein lamin A. Mutations that alter ZMPSTE24 processing of lamin A in humans cause the premature-aging disease progeria and related progeroid disorders. Intriguingly, recent evidence suggests that the entire a-factor pathway, including all three biogenesis modules, may be used to produce a prenylated, secreted signaling molecule involved in germ cell migration in Drosophila. Thus, additional prenylated signaling molecules resembling a-factor, with as-yet-unknown roles in metazoan biology, may await discovery.
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65
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Abstract
A new mechanism involving cleavage of a transcription factor called CREB3L1 has been proposed to explain the anti-tumour effects of doxorubicin.
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Affiliation(s)
- Anand G Patel
- is in the Department of Molecular Pharmacology and Experimental Therapeutics , Mayo Clinic , Rochester , United States
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66
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Stoyanova T, Goldstein AS, Cai H, Drake JM, Huang J, Witte ON. Regulated proteolysis of Trop2 drives epithelial hyperplasia and stem cell self-renewal via β-catenin signaling. Genes Dev 2012; 26:2271-85. [PMID: 23070813 DOI: 10.1101/gad.196451.112] [Citation(s) in RCA: 108] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The cell surface protein Trop2 is expressed on immature stem/progenitor-like cells and is overexpressed in many epithelial cancers. However the biological function of Trop2 in tissue maintenance and tumorigenesis remains unclear. In this study, we demonstrate that Trop2 is a regulator of self-renewal, proliferation, and transformation. Trop2 controls these processes through a mechanism of regulated intramembrane proteolysis that leads to cleavage of Trop2, creating two products: the extracellular domain and the intracellular domain. The intracellular domain of Trop2 is released from the membrane and accumulates in the nucleus. Heightened expression of the Trop2 intracellular domain promotes stem/progenitor self-renewal through signaling via β-catenin and is sufficient to initiate precursor lesions to prostate cancer in vivo. Importantly, we demonstrate that loss of β-catenin or Trop2 loss-of-function cleavage mutants abrogates Trop2-driven self-renewal and hyperplasia in the prostate. These findings suggest that heightened expression of Trop2 is selected for in epithelial cancers to enhance the stem-like properties of self-renewal and proliferation. Defining the mechanism of Trop2 function in self-renewal and transformation is essential to identify new therapeutic strategies to block Trop2 activation in cancer.
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Affiliation(s)
- Tanya Stoyanova
- Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, California 90095, USA
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67
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Knopf RR, Feder A, Mayer K, Lin A, Rozenberg M, Schaller A, Adam Z. Rhomboid proteins in the chloroplast envelope affect the level of allene oxide synthase in Arabidopsis thaliana. THE PLANT JOURNAL : FOR CELL AND MOLECULAR BIOLOGY 2012; 72:559-71. [PMID: 22738221 DOI: 10.1111/j.1365-313x.2012.05090.x] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Rhomboids are intra-membrane serine proteases whose sequences are found in nearly all organisms. They are involved in a variety of biological functions in both eukaryotes and prokaryotes. Localization assays revealed that two Arabidopsis thaliana rhomboid-like proteases (AtRBL), AtRBL8 and AtRBL9, are targeted to the chloroplast. Using transgenic plants expressing epitope-tagged AtRBL9, we localized AtRBL9 to the chloroplast inner envelope membrane, with both its N- and C-termini facing the stroma. Mass spectrometry analyses confirmed this localization, and suggested that this is also the case for AtRBL8. Both are proteins of very low abundance. The results of size-exclusion chromatography implied that AtRBL9 forms homo-oligomers. In search of a putative function, a comparative proteomic analysis was performed on wild-type and double-knockout plants, lacking both AtRBL8 and AtRBL9, using the iTRAQ method. Of 180 envelope proteins, the level of only a few was either increased or decreased in the mutant line. One of the latter, allene oxide synthase, is involved in jasmonic acid biosynthesis. This observation provides an explanation for the recently reported aberration in flower morphology that is associated with the loss of AtRBL8.
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Affiliation(s)
- Ronit Rimon Knopf
- Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, Hebrew University of Jerusalem, Rehovot 76100, Israel
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68
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Identification and characterization of five intramembrane metalloproteases in Anabaena variabilis. J Bacteriol 2012; 194:6105-15. [PMID: 22961855 DOI: 10.1128/jb.01366-12] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Regulated intramembrane proteolysis (RIP) involves cleavage of a transmembrane segment of a protein, releasing the active form of a membrane-anchored transcription factor (MTF) or a membrane-tethered signaling protein in response to an extracellular or intracellular signal. RIP is conserved from bacteria to humans and governs many important signaling pathways in both prokaryotes and eukaryotes. Proteases that carry out these cleavages are named intramembrane cleaving proteases (I-CLips). To date, little is known about I-CLips in cyanobacteria. In this study, five putative site-2 type I-Clips (Ava_1070, Ava_1730, Ava_1797, Ava_3438, and Ava_4785) were identified through a genome-wide survey in Anabaena variabilis. Biochemical analysis demonstrated that these five putative A. variabilis site-2 proteases (S2Ps(Av)) have authentic protease activities toward an artificial substrate pro-σ(K), a Bacillus subtilis MTF, in our reconstituted Escherichia coli system. The enzymatic activities of processing pro-σ(K) differ among these five S2Ps(Av). Substitution of glutamic acid (E) by glutamine (Q) in the conserved HEXXH zinc-coordinated motif caused the loss of protease activities in these five S2Ps(Av), suggesting that they belonged to the metalloprotease family. Further mapping of the cleaved peptides of pro-σ(K) by Ava_4785 and Ava_1797 revealed that Ava_4785 and Ava_1797 recognized the same cleavage site in pro-σ(K) as SpoIVFB, a cognate S2P of pro-σ(K) from B. subtilis. Taking these results together, we report here for the first time the identification of five metallo-intramembrane cleaving proteases in Anabaena variabilis. The experimental system described herein should be applicable to studies of other RIP events and amenable to developing in vitro assays for I-CLips.
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69
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Brown MS, Goldstein JL. Scientific side trips: six excursions from the beaten path. J Biol Chem 2012; 287:22418-35. [PMID: 22584575 DOI: 10.1074/jbc.x112.381681] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Affiliation(s)
- Michael S Brown
- Department of Molecular Genetics, University of Texas Southwestern Medical Center, Dallas, Texas 75390, USA.
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70
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Abstract
Rhomboids are ubiquitous intramembrane serine proteases the sequences of which are found in nearly all sequenced genomes, including those of plants. They were molecularly characterized in a number of organisms, and were found to play a role in a variety of biological functions including signaling, development, apoptosis, mitochondrial integrity, parasite invasion and more. Although rhomboid sequences are found in plants, very little is known about their function. Here, we present the current knowledge in the rhomboids field in general, and in plant rhomboids in particular. In addition, we discuss possible physiological roles of different plant rhomboids.
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Affiliation(s)
- Ronit Rimon Knopf
- The Robert H. Smith Institute of Plant Sciences and Genetics in Agriculture, The Hebrew University of Jerusalem, Rehovot 76100, Israel
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71
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Pioli PD, Saleh AMZ, El Fiky A, Nastiuk KL, Krolewski JJ. Sequential proteolytic processing of an interferon-alpha receptor subunit by TNF-alpha converting enzyme and presenilins. J Interferon Cytokine Res 2012; 32:312-25. [PMID: 22458690 DOI: 10.1089/jir.2011.0116] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
It is well established that interferons trigger tyrosine-kinase-dependent signaling via JAK kinases and STAT transcription factors. However, we have observed both IFNaR2 receptor cleavage and functional activity of the liberated intracellular domain (ICD), suggesting that interferon-alpha (IFN-alpha) can also signal via regulated intramembrane proteolysis (RIP), an evolutionarily conserved mechanism of receptor-mediated signaling. Sequential cleavage of the receptor ectodomain and transmembrane domain is a hallmark of the most common class of RIP. To investigate the mechanisms of IFNaR2 RIP signaling, we examined IFNaR2 cleavage by TNF-alpha converting enzyme (TACE) and presenilin proteases. We tracked the fate of epitope-tagged and fusion variants of IFNaR2 in cells expressing wild-type, mutant, or null versions of TACE and presenilins 1 and 2. Cleavage and subcellular location were determined by immunoblot, fluoresence microscopy, and reporter assays. We found that both TACE and presenilin 1/2 cleave IFNaR2, in a sequential manner that allows the ICD to move to the nucleus. TACE cleavage was induced by IFN-alpha but was not consistently required for the anti-proliferative effects of IFN-alpha. In conclusion, IFNaR2 is cleaved by TACE and Presenilin 1/2, suggesting that interferons signal by both kinase and RIP-mediated pathways.
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Affiliation(s)
- Peter D Pioli
- Department of Pathology and Laboratory Medicine, University of California, IRVINE, Irvine, CA 92697, USA
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72
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Merrick D, Chapin H, Baggs JE, Yu Z, Somlo S, Sun Z, Hogenesch JB, Caplan MJ. The γ-secretase cleavage product of polycystin-1 regulates TCF and CHOP-mediated transcriptional activation through a p300-dependent mechanism. Dev Cell 2011; 22:197-210. [PMID: 22178500 DOI: 10.1016/j.devcel.2011.10.028] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2010] [Revised: 08/01/2011] [Accepted: 10/26/2011] [Indexed: 12/28/2022]
Abstract
Mutations in Pkd1, encoding polycystin-1 (PC1), cause autosomal-dominant polycystic kidney disease (ADPKD). We show that the carboxy-terminal tail (CTT) of PC1 is released by γ-secretase-mediated cleavage and regulates the Wnt and CHOP pathways by binding the transcription factors TCF and CHOP, disrupting their interaction with the common transcriptional coactivator p300. Loss of PC1 causes increased proliferation and apoptosis, while reintroducing PC1-CTT into cultured Pkd1 null cells reestablishes normal growth rate, suppresses apoptosis, and prevents cyst formation. Inhibition of γ-secretase activity impairs the ability of PC1 to suppress growth and apoptosis and leads to cyst formation in cultured renal epithelial cells. Expression of the PC1-CTT is sufficient to rescue the dorsal body curvature phenotype in zebrafish embryos resulting from either γ-secretase inhibition or suppression of Pkd1 expression. Thus, γ-secretase-dependent release of the PC1-CTT creates a protein fragment whose expression is sufficient to suppress ADPKD-related phenotypes in vitro and in vivo.
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Affiliation(s)
- David Merrick
- Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510, USA
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73
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Bondar AN, White SH. Hydrogen bond dynamics in membrane protein function. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2011; 1818:942-50. [PMID: 22178866 DOI: 10.1016/j.bbamem.2011.11.035] [Citation(s) in RCA: 63] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Revised: 11/22/2011] [Accepted: 11/30/2011] [Indexed: 11/30/2022]
Abstract
Changes in inter-helical hydrogen bonding are associated with the conformational dynamics of membrane proteins. The function of the protein depends on the surrounding lipid membrane. Here we review through specific examples how dynamical hydrogen bonds can ensure an elegant and efficient mechanism of long-distance intra-protein and protein-lipid coupling, contributing to the stability of discrete protein conformational substates and to rapid propagation of structural perturbations. This article is part of a Special Issue entitled: Protein Folding in Membranes.
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Affiliation(s)
- Ana-Nicoleta Bondar
- Theoretical Molecular Biophysics, Freie Universität Berlin, Department of Physics, Arnimallee 14, 14195 Berlin, Germany.
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74
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Degnin CR, Laederich MB, Horton WA. Ligand activation leads to regulated intramembrane proteolysis of fibroblast growth factor receptor 3. Mol Biol Cell 2011; 22:3861-73. [PMID: 21865593 PMCID: PMC3192865 DOI: 10.1091/mbc.e11-01-0080] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
FGFR3 is implicated in several human diseases. Following activation and endocytosis, FGFR3 undergoes sequential ectodomain and intramembrane cleavages to generate a soluble cytoplasmic fragment that can translocate to the nucleus. Fibroblast growth factor receptor 3 (FGFR3) is a major negative regulator of bone growth that inhibits the proliferation and differentiation of growth plate chondrocytes. Activating mutations of its c isoform cause dwarfism in humans; somatic mutations can drive oncogenic transformation in multiple myeloma and bladder cancer. How these distinct activities arise is not clear. FGFR3 was previously shown to undergo proteolytic cleavage in the bovine rib growth plate, but this was not explored further. Here, we show that FGF1 induces regulated intramembrane proteolysis (RIP) of FGFR3. The ectodomain is proteolytically cleaved (S1) in response to ligand-induced receptor activation, but unlike most RIP target proteins, it requires endocytosis and does not involve a metalloproteinase. S1 cleavage generates a C-terminal domain fragment that initially remains anchored in the membrane, is phosphorylated, and is spatially distinct from the intact receptor. Ectodomain cleavage is followed by intramembrane cleavage (S2) to generate a soluble intracellular domain that is released into the cytosol and can translocate to the nucleus. We identify the S1 cleavage site and show that γ-secretase mediates the S2 cleavage event. In this way we demonstrate a mechanism for the nuclear localization of FGFR3 in response to ligand activation, which may occur in both development and disease.
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Affiliation(s)
- Catherine R Degnin
- Research Center, Shriners Hospital for Children, Portland, OR 97239, USA
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