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Abstract
Active nucleo-cytoplasmic transport is mediated by dynamic signal-mediated pathways. We investigated the effects of transcription inhibitors or fluorescent lectins on nuclear import mediated by nuclear localization signals (NLSs). Therefore, a novel experimental approach that allows the controlled sequential introduction of fluorescent substances into living cells was established. A microinjection system equipped with an UV-source enabled us to identify fluorescent-labeled cells for the subsequent introduction of additional fluorescent compounds, in order to study their interactions in vivo. Cells were initially labeled either by expression of autofluorescent proteins or by microinjection of fluorescent substances. Transcription inhibitors did not affect nuclear transport mediated by classical NLSs but inhibited import mediated by the M9-domain of hnRNPA1. Comparison of a mono- and bipartite NLS revealed that the bipartite signal was more active in import. Sequential injection of differentially labeled nuclear import and export substrates allowed monitoring of import and export simultaneously in the same living cell. The introduced experimental approach will also be useful to analyze a variety of biological processes in living mammalian cells.
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Affiliation(s)
- R H Stauber
- Institute for Clinical and Molecular Virology, University of Erlangen-Nürnberg, Schlossgarten 4, D-91054 Erlangen, Germany.
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2
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Abstract
Members of the Rab family of small GTPases play important roles in membrane trafficking along the exocytic and endocytic pathways. The Rab11 subfamily consists of two highly conserved members, Rab11a and Rab11b. Rab11a has been localized both to the pericentriolar recycling endosome and to the trans-Golgi network and functions in recycling of transferrin. However, the localization and function of Rab11b are completely unknown. In this study green fluorescent protein (GFP)-tagged Rab11b was used to determine its subcellular localization. GFP-Rab11b colocalized with internalized transferrin, and using different mutants of Rab11b, the role of this protein in transferrin uptake and recycling was examined. Two of these mutants, Rab11b-Q/L (constitutively active) and Rab11b-S/N (constitutively inactive), strongly inhibited the recycling of transferrin. Interestingly, both of them had no effect on transferrin uptake. In contrast, the C-terminally altered mutant Rab11b-DeltaC, which cannot be prenylated and therefore cannot interact with membranes, did not interfere with wild-type Rab11b function. From these data we concluded that functional Rab11b is essential for the transport of internalized transferrin from the recycling compartment to the plasma membrane.
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Affiliation(s)
- B Schlierf
- Chair of Genetics, Staudtstrasse 5, Erlangen, D-91058, USA
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3
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Kruse M, Rosorius O, Krätzer F, Stelz G, Kuhnt C, Schuler G, Hauber J, Steinkasserer A. Mature dendritic cells infected with herpes simplex virus type 1 exhibit inhibited T-cell stimulatory capacity. J Virol 2000; 74:7127-36. [PMID: 10888653 PMCID: PMC112231 DOI: 10.1128/jvi.74.15.7127-7136.2000] [Citation(s) in RCA: 213] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/1999] [Accepted: 04/26/2000] [Indexed: 11/20/2022] Open
Abstract
Mature dendritic cells (DC) are the most potent antigen-presenting cells within the entire immune system. Interference with the function of these cells therefore constitutes a very powerful mechanism for viruses to escape immune responses. Several members of the Herpesviridae family have provided examples of such escape strategies, including interference with antigen presentation and production of homologous cytokines. In this study we investigated the infection of mature DC with herpes simplex virus type 1 (HSV-1) and the way in which infection alters the phenotype and function of mature DC. Interestingly, the T-cell-stimulatory capacity of these DC was strongly impaired. Furthermore, we demonstrated that HSV-1 leads to the specific degradation of CD83, a cell surface molecule which is specifically upregulated during DC maturation. These data indicate that HSV-1 has developed yet another novel mechanism to escape immune responses.
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Affiliation(s)
- M Kruse
- Department of Dermatology, University of Erlangen-Nürnberg, Erlangen, Germany.
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4
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Rosorius O, Fries B, Stauber RH, Hirschmann N, Bevec D, Hauber J. Human ribosomal protein L5 contains defined nuclear localization and export signals. J Biol Chem 2000; 275:12061-8. [PMID: 10766838 DOI: 10.1074/jbc.275.16.12061] [Citation(s) in RCA: 55] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Ribosomal protein L5 is part of the 60 S ribosomal subunit and localizes in both the cytoplasm and the nucleus of eukaryotic cells, accumulating particularly in the nucleoli. L5 is known to bind specifically to 5 S rRNA and is involved in nucleocytoplasmic transport of this rRNA. Here, we report a detailed analysis of the domain organization of the human ribosomal protein L5. We show that a signal that mediates nuclear import and nucleolar localization maps to amino acids 21-37 within the 297-amino acid L5 protein. Furthermore, carboxyl-terminal residues at positions 255-297 serve as an additional nuclear/nucleolar targeting signal. Domains involved in 5 S rRNA binding are located at both the amino terminus and the carboxyl terminus of L5. Microinjection studies in somatic cells demonstrate that a nuclear export signal (NES) that maps to amino acids 101-111 resides in the central region of L5. This NES is characterized by a pronounced clustering of critical leucine residues, which creates a peptide motif not previously observed in other leucine-rich NESs. Finally, we present a refined model of the multidomain structure of human ribosomal protein L5.
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Affiliation(s)
- O Rosorius
- Institute for Clinical and Molecular Virology, University Erlangen-Nürnberg, Schlossgarten 4, D-91054 Erlangen, Germany
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5
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Krätzer F, Rosorius O, Heger P, Hirschmann N, Dobner T, Hauber J, Stauber RH. The adenovirus type 5 E1B-55K oncoprotein is a highly active shuttle protein and shuttling is independent of E4orf6, p53 and Mdm2. Oncogene 2000; 19:850-7. [PMID: 10702793 DOI: 10.1038/sj.onc.1203395] [Citation(s) in RCA: 83] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/1999] [Revised: 12/06/1999] [Accepted: 12/08/1999] [Indexed: 11/09/2022]
Abstract
The E1B-55K and E4orf6 oncoproteins of adenovirus type 5 are involved in the export of viral mRNAs. Previously, it was suggested that a complex composed of E1B-55K and E4orf6 serves as a nucleocytoplasmic transporter for viral mRNAs in which the E4orf6 protein directs both nuclear import and export. We now demonstrate that the E1B-55K protein itself shuttles efficiently in the absence of E4orf6. In addition, E1B-55K trafficking was independent of the defined shuttle proteins Mdm2 or p53, which interacts with E1B-55K. The identified N-terminal E1B-55K leucine-rich nuclear-export signal (NES) conferred rapid nuclear export even in a heterologous system in contrast to the postulated E4orf6NES. Interestingly, although shuttling was blocked by inhibitors of the CRM1 mediated export pathway, E1B-55K inhibited neither the activity nor the trafficking of the retroviral shuttle proteins HIV-1 Rev and HTLV-1 Rex. In contrast, Rev or Rex blocked the nuclear export of E1B-55K, most likely by competing for essential export factors. Our results provide new insights into the regulation of the adenovirus mRNA export system and the processes of adenovirus mediated transformation. Oncogene (2000) 19, 850 - 857.
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Affiliation(s)
- F Krätzer
- Institute for Clinical and Molecular Virology, University of Erlangen-Nürnberg, Schlossgarten 4, D-91054 Erlangen, Germany
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6
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Rosorius O, Heger P, Stelz G, Hirschmann N, Hauber J, Stauber RH. Direct observation of nucleocytoplasmic transport by microinjection of GFP-tagged proteins in living cells. Biotechniques 1999; 27:350-5. [PMID: 10457843 DOI: 10.2144/99272rr02] [Citation(s) in RCA: 45] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
We established a straightforward experimental system to investigate directly the requirements for nucleocytoplasmic transport in live cells. For this purpose, substrates were created containing nuclear localization signals (NLS) or nuclear export signals (NES) linked to a chimeric protein composed of the glutathione S-transferase (GST) fused to the green fluorescent protein (GFP). The combination of GST/GFP-tagging allowed us to control protein expression in bacteria and to monitor protein purification during chromatography. Following microinjection into somatic cells, nuclear export/import of the highly fluorescent substrates could be observed directly by fluorescence microscopy. This system sets the stage to quantitate, in real time, the kinetics of nuclear import/export in living cells and to evaluate qualitative differences in various NLS/NES signals and pathways.
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Affiliation(s)
- O Rosorius
- University of Erlangen-Nürnberg, Germany
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7
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Heger P, Rosorius O, Hauber J, Stauber RH. Titration of cellular export factors, but not heteromultimerization, is the molecular mechanism of trans-dominant HTLV-1 rex mutants. Oncogene 1999; 18:4080-90. [PMID: 10435589 DOI: 10.1038/sj.onc.1202762] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
The HTLV-1 Rex protein is an essential shuttle protein required for nuclear export of unspliced and incompletely-spliced viral RNAs. Several trans-dominant (TD) mutant Rex proteins have been reported, however, the mechanism of trans-dominance is not known. We compared TD Rex mutants and found that a natural occurring Rex mutant, Rexp21, lacking the RNA binding domain, was highly TD and inhibited also HIV-1 Rev function. Using fusions to the green fluorescent protein (GFP) we observed that Rexp21-GFP displayed a cytoplasmic localization but was actively shuttling between the nucleus and the cytoplasm in live human cells. The presence of Rexp21-GFP inhibited the nuclear export of Rex and HIV-1 Rev as assayed by cotransfection and microinjection experiments. However, Rex-GFP or Rexp21-GFP did not form heteromultimers with nuclear Rex mutants in vivo. In contrast, shuttling was essential for trans-dominance. Thus, we propose that TD Rex mutants do not function by retaining WT Rex in the nucleus by protein-protein interactions, as demonstrated for Rev, but to titrate factors essential for Rex/Rev export. Our findings demonstrate differences between the regulatory proteins Rex and Rev and implicate a novel strategy to generate highly TD Rex mutants also applicable to other proteins.
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Affiliation(s)
- P Heger
- Institute for Medical and Clinical Virology, University of Erlangen-Nürnberg, Erlangen, Germany
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8
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Rosorius O, Reichart B, Krätzer F, Heger P, Dabauvalle MC, Hauber J. Nuclear pore localization and nucleocytoplasmic transport of eIF-5A: evidence for direct interaction with the export receptor CRM1. J Cell Sci 1999; 112 ( Pt 14):2369-80. [PMID: 10381392 DOI: 10.1242/jcs.112.14.2369] [Citation(s) in RCA: 106] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Eukaryotic initiation factor 5A (eIF-5A) is the only cellular protein known to contain the unusual amino acid hypusine. The exact in vivo function of eIF-5A, however, is to date unknown. The finding that eIF-5A is an essential cofactor of the human immunodeficiency virus type 1 (HIV-1) Rev RNA transport factor suggested that eIF-5A is part of a specific nuclear export pathway. In this study we used indirect immunofluorescence and immunogold electron microscopy to demonstrate that eIF-5A accumulates at nuclear pore-associated intranuclear filaments in mammalian cells and Xenopus oocytes. We are able to show that eIF-5A interacts with the general nuclear export receptor, CRM1. Furthermore, microinjection studies in somatic cells revealed that eIF-5A is transported from the nucleus to the cytoplasm, and that this nuclear export is blocked by leptomycin B. Our data demonstrate that eIF-5A is a nucleocytoplasmic shuttle protein.
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Affiliation(s)
- O Rosorius
- Institute for Clinical and Molecular Virology, University Erlangen-Nürnberg, Schlossgarten 4, D-91054 Erlangen, Germany
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9
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Elfgang C, Rosorius O, Hofer L, Jaksche H, Hauber J, Bevec D. Evidence for specific nucleocytoplasmic transport pathways used by leucine-rich nuclear export signals. Proc Natl Acad Sci U S A 1999; 96:6229-34. [PMID: 10339570 PMCID: PMC26864 DOI: 10.1073/pnas.96.11.6229] [Citation(s) in RCA: 77] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/1999] [Indexed: 11/18/2022] Open
Abstract
Various proteins with different biological activities have been observed to be translocated from the nucleus to the cytoplasm in an energy- and signal-dependent manner in eukaryotic cells. This nuclear export is directed by nuclear export signals (NESs), typically characterized by hydrophobic, primarily leucine, amino acid residues. Moreover, it has been shown that CRM1/exportin 1 is an export receptor for leucine-rich NESs. However, additional NES-interacting proteins have been described. In particular, eukaryotic initiation factor 5A (eIF-5A) has been shown to be a critical cellular cofactor for the nuclear export of the HIV type 1 (HIV-1) Rev trans-activator protein. In this study we compared the nuclear export activity of NESs of different origin. Microinjection of export substrates into the nucleus of somatic cells in combination with specific inhibitors indicated that specific nuclear export pathways exist for different NES-containing proteins. In particular, inhibition of eIF-5A blocked the nuclear export of NESs derived from the HIV-1 Rev and human T cell leukemia virus type I Rex trans-activators, whereas nucleocytoplasmic translocation of the protein kinase inhibitor-NES was unaffected. In contrast, however, inhibition of CRM1/exportin 1 blocked the nuclear export of all NES-containing proteins investigated. Our data confirm that CRM1/exportin 1 is a general export receptor for leucine-rich NESs and suggest that eIF-5A acts either upstream of CRM1/exportin 1 or forms a complex with the NES and CRM1/exportin 1 in the nucleocytoplasmic translocation of the HIV-1 Rev and human T cell leukemia virus type I Rex RNA export factors.
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Affiliation(s)
- C Elfgang
- Novartis Research Institute, Department of Immunology, Brunner Strasse 59, A-1235 Vienna, Austria
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10
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Heger P, Rosorius O, Koch C, Casari G, Grassmann R, Hauber J. Multimer formation is not essential for nuclear export of human T-cell leukemia virus type 1 Rex trans-activator protein. J Virol 1998; 72:8659-68. [PMID: 9765406 PMCID: PMC110278 DOI: 10.1128/jvi.72.11.8659-8668.1998] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The Rex trans-regulatory protein of human T-cell leukemia virus type 1 (HTLV-1) is required for the nuclear export of incompletely spliced and unspliced viral mRNAs and is therefore essential for virus replication. Rex is a nuclear phosphoprotein that directly binds to its cis-acting Rex response element RNA target sequence and constantly shuttles between the nucleus and cytoplasm. Moreover, Rex induces nuclear accumulation of unspliced viral RNA. Three protein domains which mediate nuclear import-RNA binding, nuclear export, and Rex oligomerization have been mapped within the 189-amino-acid Rex polypeptide. Here we identified a different region in the carboxy-terminal half of Rex which is also required for biological activity. In inactive mutants with mutations that map within this region, as well as in mutants that are deficient in Rex-specific multimerization, Rex trans activation could be reconstituted by fusion to a heterologous leucine zipper dimerization interface. The intracellular trafficking capabilities of wild-type and mutant Rex proteins reveal that biologically inactive and multimerization-deficient Rex mutants are still efficiently translocated from the nucleus to the cytoplasm. This observation indicates that multimerization is essential for Rex function but is not required for nuclear export. Finally, we are able to provide an improved model of the HTLV-1 Rex domain structure.
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Affiliation(s)
- P Heger
- Institute for Clinical and Molecular Virology, University Erlangen-Nürnberg, D-91054 Erlangen, Germany
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11
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Schatz O, Oft M, Dascher C, Schebesta M, Rosorius O, Jaksche H, Dobrovnik M, Bevec D, Hauber J. Interaction of the HIV-1 rev cofactor eukaryotic initiation factor 5A with ribosomal protein L5. Proc Natl Acad Sci U S A 1998; 95:1607-12. [PMID: 9465063 PMCID: PMC19115 DOI: 10.1073/pnas.95.4.1607] [Citation(s) in RCA: 64] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/1997] [Indexed: 02/06/2023] Open
Abstract
It has previously been shown that interaction of eukaryotic initiation factor 5A (eIF-5A) with the Rev trans-activator protein of HIV-1 mediates the transport of unspliced or incompletely spliced viral mRNAs across the nuclear envelope. Consequently, mutants of eIF-5A block Rev function and thereby replication of HIV-1 in trans, indicating that eIF-5A is a crucial protein that connects the viral Rev regulator with cellular RNA transport systems. Here we show that the ribosomal protein L5, which is the central protein component of the 5S rRNA export system, is a cellular interaction partner of eIF-5A. Functional studies demonstrate that overexpression of L5 protein significantly enhances Rev activity. Furthermore, Rev nuclear export activity is inhibited in human somatic cells by antibodies that recognize eIF-5A or L5. Our data suggest that the Rev export pathway shares components of a cellular transport system involved in the intracellular trafficking of polymerase III (5S rRNA) transcripts.
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Affiliation(s)
- O Schatz
- Medical Policlinic, Pettenkoferstr. 8a, D-80336 Munich, Germany
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12
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Rosorius O, Issinger OG, Braulke T. Brain-specific interaction of a 91-kDa membrane-bound protein with the cytoplasmic tail of the 300-kDa mannose 6-phosphate receptor. Biochem Biophys Res Commun 1996; 221:525-30. [PMID: 8629995 DOI: 10.1006/bbrc.1996.0630] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The cytoplasmic tail of the 300 kDa mannose 6-phosphate receptor (MPR 300-CT) is thought to play an important role in sorting and targeting of lysosomal enzymes and the insulin-like growth factor II along the biosynthetic and endocytic pathway. In this study a brain specific 91 kDa protein and a 35 kDa protein salt-washed from membranes (referred as TIP 91-M and TIP 35-M) were found to interact with the cytoplasmic receptor tail as assayed by cross-linkage with recombinant [32P] labeled MPR 300-CT. Subcellular fractionation revealed a distinct pattern of distribution of TIP 35-M and TIP 91-M in microsomal and synaptosomal fractions. Furthermore, the formation of cross-link complexes with membrane proteins appeared to be developmentally and regionally regulated in the brain and inhibited upon ATP hydrolysis. The data suggest the requirement of specific protein interactions for MPR 300 functions in neuronal cells.
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Affiliation(s)
- O Rosorius
- Institute for Biochemistry II, University of Göttingen, Germany
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13
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Körner C, Herzog A, Weber B, Rosorius O, Hemer F, Schmidt B, Braulke T. In vitro phosphorylation of the 46-kDa mannose 6-phosphate receptor by casein kinase II. Structural requirements for efficient phosphorylation. J Biol Chem 1994; 269:16529-32. [PMID: 8206966] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Some steps in the receptor-mediated transport of newly synthesized mannose 6-phosphate-containing lysosomal enzymes are assumed to be accompanied by changes in the phosphorylation state of receptors. In vitro, the metabolically phosphorylated 46-kDa mannose 6-phosphate receptor (MPR 46) was dephosphorylated by protein phosphatase 2A. The synthetic cytoplasmic domain of MPR 46 was phosphorylated in vitro by casein kinase II. Tryptic phosphopeptide mapping showed that casein kinase II phosphorylates MPR 46 in vitro at the same site that is phosphorylated in vivo. Inhibition studies using synthetic peptides corresponding to different amino acid sequences of the cytoplasmic tail of MPR 46 revealed that the sequence 26-32 (ADGCDFV) contribute to efficient phosphorylation of serine 56. Baby hamster kidney cells were transfected with wild type human MPR 46 cDNA or cDNAs containing mutations in the cytoplasmic tail and assayed for their phosphorylation state in vivo. The phosphorylation of mutant receptors with deleted residues 23-28 (NLVADG) was strongly reduced. These data indicate that residues on the N-terminal side of the phosphorylatable serine 56 may influence the efficiency with which a casein-kinase II-like kinase phosphorylates MPR 46.
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Affiliation(s)
- C Körner
- Institute of Biochemistry II, University of Göttingen, Federal Republic of Germany
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14
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Körner C, Herzog A, Weber B, Rosorius O, Hemer F, Schmidt B, Braulke T. In vitro phosphorylation of the 46-kDa mannose 6-phosphate receptor by casein kinase II. Structural requirements for efficient phosphorylation. J Biol Chem 1994. [DOI: 10.1016/s0021-9258(19)89419-x] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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15
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Abstract
ARBP (attachment region binding protein) is an abundant nuclear protein that specifically binds to matrix/scaffold attachment regions (MARs/SARs). Here we show by gel filtration and gradient sedimentation that ARBP has an elongated shape. The sedimentation coefficient was determined as only 2.1 S. Furthermore, limited proteolysis of ARBP in situ (in isolated nuclei) with several proteases generated limiting resistant peptides from 14.5 to 18 kDa, that retained the ability to bind MARs specifically. This indicates that these peptides encompass the DNA binding domain of ARBP.
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Affiliation(s)
- J P von Kries
- Institut für Physiologische Chemie, Universitäts-Krankenhaus Eppendorf, Hamburg, Germany
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16
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Rosorius O, Issinger OG, Braulke T. Phosphorylation of the cytoplasmic tail of the 300-kDa mannose 6-phosphate receptor is required for the interaction with a cytosolic protein. J Biol Chem 1993; 268:21470-3. [PMID: 8407994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The cytoplasmic tail of the human 300-kDa mannose 6-phosphate receptor (MPR 300-CT) is an excellent substrate for casein kinase II in vitro. The phosphorylated MPR 300-CT was cross-linked by means of bis(sulfosuccinimidyl)suberate mainly to a cytosolic protein of 35 kDa (referred to as TIP 35) and to 35- and 91-kDa proteins salt-washed from bovine brain membranes. Gel filtration suggested that TIP 35 is part of a higher molecular mass complex of approximately 130-150 kDa. Inhibition studies, using non-phosphorylated and phosphorylated MPR 300-CT and cross-linking, indicate that the interaction with TIP 35 is phosphorylation-specific. Furthermore, TIP 35 was only cross-linked to the MPR 300-CT phosphorylated by casein kinase II whereas the MPR 300-CT phosphorylated by protein kinase A failed to cross-link to TIP 35. These results indicate that the cytoplasmic tail of the MPR 300 interacts with a cytosolic protein depending on the phosphorylation by a casein kinase II-like kinase. The cross-linking with salt-washed membrane proteins, however, is inhibited by non-phosphorylated MPR 300-CT, suggesting that different structural determinants in the MPR 300-CT interact with cytosol- and membrane-derived proteins.
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Affiliation(s)
- O Rosorius
- Institute for Biochemistry II, University of Göttingen, Federal Republic of Germany
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17
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Rosorius O, Issinger O, Braulke T. Phosphorylation of the cytoplasmic tail of the 300-kDa mannose 6-phosphate receptor is required for the interaction with a cytosolic protein. J Biol Chem 1993. [DOI: 10.1016/s0021-9258(20)80560-2] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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18
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Rosorius O, Mieskes G, Issinger OG, Körner C, Schmidt B, von Figura K, Braulke T. Characterization of phosphorylation sites in the cytoplasmic domain of the 300 kDa mannose-6-phosphate receptor. Biochem J 1993; 292 ( Pt 3):833-8. [PMID: 8318012 PMCID: PMC1134189 DOI: 10.1042/bj2920833] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The human 300 kDa mannose-6-phosphate receptor (MPR 300) is phosphorylated in vivo at serine residues of its cytoplasmic domain. Two-dimensional separation can resolve tryptic phosphopeptides into four major species. To identify the kinases involved in MPR 300 phosphorylation and the phosphorylation sites the entire coding sequence of the cytoplasmic tail was expressed in Escherichia coli. The isolated cytoplasmic domain was used as a substrate for four purified serine/threonine kinases [casein kinase II (CK II), protein kinase A (PKA), protein kinase C and Ca2+/calmodulin kinase]. All kinases phosphorylate the cytoplasmic tail exclusively on serine residues. Inhibition studies using synthetic peptides, partial sequencing of isolated tryptic phosphopeptides and co-migration with tryptic phosphopeptides from MPR 300 labelled in vivo showed that (i) PKA phosphorylates the cytoplasmic MPR 300 domain at Ser20 and at a non-identified site, neither of which are phosphorylated in vivo, and that (ii) the two sites phosphorylated by CK II in vivo and in vitro are Ser82 and Ser157. The results indicate that the human MPR 300 is a physiological substrate of either CK II or a related kinase which may play a role in the transport function of MPR 300 and/or interaction with other proteins.
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Affiliation(s)
- O Rosorius
- Institute of Biochemistry II, University of Göttingen, Germany
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