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Becker R, Vergarajauregui S, Billing F, Sharkova M, Lippolis E, Mamchaoui K, Ferrazzi F, Engel FB. Myogenin controls via AKAP6 non-centrosomal microtubule-organizing center formation at the nuclear envelope. eLife 2021; 10:65672. [PMID: 34605406 PMCID: PMC8523159 DOI: 10.7554/elife.65672] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Accepted: 10/01/2021] [Indexed: 12/22/2022] Open
Abstract
Non-centrosomal microtubule-organizing centers (MTOCs) are pivotal for the function of multiple cell types, but the processes initiating their formation are unknown. Here, we find that the transcription factor myogenin is required in murine myoblasts for the localization of MTOC proteins to the nuclear envelope. Moreover, myogenin is sufficient in fibroblasts for nuclear envelope MTOC (NE-MTOC) formation and centrosome attenuation. Bioinformatics combined with loss- and gain-of-function experiments identified induction of AKAP6 expression as one central mechanism for myogenin-mediated NE-MTOC formation. Promoter studies indicate that myogenin preferentially induces the transcription of muscle- and NE-MTOC-specific isoforms of Akap6 and Syne1, which encodes nesprin-1α, the NE-MTOC anchor protein in muscle cells. Overexpression of AKAP6β and nesprin-1α was sufficient to recruit endogenous MTOC proteins to the nuclear envelope of myoblasts in the absence of myogenin. Taken together, our results illuminate how mammals transcriptionally control the switch from a centrosomal MTOC to an NE-MTOC and identify AKAP6 as a novel NE-MTOC component in muscle cells.
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Affiliation(s)
- Robert Becker
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Florian Billing
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Maria Sharkova
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Eleonora Lippolis
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Kamel Mamchaoui
- Sorbonne Universités UPMC Université Paris 06, INSERM U974, CNRS FRE3617, Center for Research in Myology, GH Pitié Salpêtrière, 47 Boulevard de l'Hôpital, Paris, France
| | - Fulvia Ferrazzi
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.,Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
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2
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Steinfeldt J, Becker R, Vergarajauregui S, Engel FB. Alternative Splicing of Pericentrin Contributes to Cell Cycle Control in Cardiomyocytes. J Cardiovasc Dev Dis 2021; 8:jcdd8080087. [PMID: 34436229 PMCID: PMC8397033 DOI: 10.3390/jcdd8080087] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 07/09/2021] [Accepted: 07/21/2021] [Indexed: 11/16/2022] Open
Abstract
Induction of cardiomyocyte proliferation is a promising option to regenerate the heart. Thus, it is important to elucidate mechanisms that contribute to the cell cycle arrest of mammalian cardiomyocytes. Here, we assessed the contribution of the pericentrin (Pcnt) S isoform to cell cycle arrest in postnatal cardiomyocytes. Immunofluorescence staining of Pcnt isoforms combined with SiRNA-mediated depletion indicates that Pcnt S preferentially localizes to the nuclear envelope, while the Pcnt B isoform is enriched at centrosomes. This is further supported by the localization of ectopically expressed FLAG-tagged Pcnt S and Pcnt B in postnatal cardiomyocytes. Analysis of centriole configuration upon Pcnt depletion revealed that Pcnt B but not Pcnt S is required for centriole cohesion. Importantly, ectopic expression of Pcnt S induced centriole splitting in a heterologous system, ARPE-19 cells, and was sufficient to impair DNA synthesis in C2C12 myoblasts. Moreover, Pcnt S depletion enhanced serum-induced cell cycle re-entry in postnatal cardiomyocytes. Analysis of mitosis, binucleation rate, and cell number suggests that Pcnt S depletion enhances serum-induced progression of postnatal cardiomyocytes through the cell cycle resulting in cell division. Collectively, our data indicate that alternative splicing of Pcnt contributes to the establishment of cardiomyocyte cell cycle arrest shortly after birth.
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Affiliation(s)
- Jakob Steinfeldt
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schwabachanlage 12, 91054 Erlangen, Germany; (J.S.); (R.B.); (S.V.)
| | - Robert Becker
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schwabachanlage 12, 91054 Erlangen, Germany; (J.S.); (R.B.); (S.V.)
| | - Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schwabachanlage 12, 91054 Erlangen, Germany; (J.S.); (R.B.); (S.V.)
| | - Felix B. Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Schwabachanlage 12, 91054 Erlangen, Germany; (J.S.); (R.B.); (S.V.)
- Muscle Research Center Erlangen (MURCE), 91054 Erlangen, Germany
- Correspondence: ; Tel.: +49-(0)9131-85-25699
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3
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Leone M, Cazorla-Vázquez S, Ferrazzi F, Wiederstein JL, Gründl M, Weinstock G, Vergarajauregui S, Eckstein M, Krüger M, Gaubatz S, Engel FB. IQGAP3, a YAP Target, Is Required for Proper Cell-Cycle Progression and Genome Stability. Mol Cancer Res 2021; 19:1712-1726. [PMID: 34183451 DOI: 10.1158/1541-7786.mcr-20-0639] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2020] [Revised: 04/08/2021] [Accepted: 06/17/2021] [Indexed: 11/16/2022]
Abstract
Controlling cell proliferation is critical for organism development, tissue homeostasis, disease, and regeneration. IQGAP3 has been shown to be required for proper cell proliferation and migration, and is associated to a number of cancers. Moreover, its expression is inversely correlated with the overall survival rate in the majority of cancers. Here, we show that IQGAP3 expression is elevated in cervical cancer and that in these cancers IQGAP3 high expression is correlated with an increased lethality. Furthermore, we demonstrate that IQGAP3 is a target of YAP, a regulator of cell cycle gene expression. IQGAP3 knockdown resulted in an increased percentage of HeLa cells in S phase, delayed progression through mitosis, and caused multipolar spindle formation and consequentially aneuploidy. Protein-protein interaction studies revealed that IQGAP3 interacts with MMS19, which is known in Drosophila to permit, by competitive binding to Xpd, Cdk7 to be fully active as a Cdk-activating kinase (CAK). Notably, IQGAP3 knockdown caused decreased MMS19 protein levels and XPD knockdown partially rescued the reduced proliferation rate upon IQGAP3 knockdown. This suggests that IQGAP3 modulates the cell cycle via the MMS19/XPD/CAK axis. Thus, in addition to governing proliferation and migration, IQGAP3 is a critical regulator of mitotic progression and genome stability. IMPLICATIONS: Our data indicate that, while IQGAP3 inhibition might be initially effective in decreasing cancer cell proliferation, this approach harbors the risk to promote aneuploidy and, therefore, the formation of more aggressive cancers.
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Affiliation(s)
- Marina Leone
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.
| | - Salvador Cazorla-Vázquez
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Fulvia Ferrazzi
- Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
| | - Janica L Wiederstein
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Marco Gründl
- Theodor Boveri Institute and Comprehensive Cancer Center Mainfranken, Biocenter, University of Wuerzburg, Wuerzburg, Germany
| | - Grit Weinstock
- Theodor Boveri Institute and Comprehensive Cancer Center Mainfranken, Biocenter, University of Wuerzburg, Wuerzburg, Germany
| | - Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Markus Eckstein
- Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Marcus Krüger
- Institute for Genetics, Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases (CECAD), University of Cologne, Cologne, Germany
| | - Stefan Gaubatz
- Theodor Boveri Institute and Comprehensive Cancer Center Mainfranken, Biocenter, University of Wuerzburg, Wuerzburg, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany. .,Muscle Research Center Erlangen (MURCE), Erlangen, Germany.,Comprehensive Cancer Center Erlangen-EMN (CCC ER-EMN), Erlangen, Germany
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4
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Vergarajauregui S, Becker R, Steffen U, Sharkova M, Esser T, Petzold J, Billing F, Kapiloff MS, Schett G, Thievessen I, Engel FB. AKAP6 orchestrates the nuclear envelope microtubule-organizing center by linking golgi and nucleus via AKAP9. eLife 2020; 9:61669. [PMID: 33295871 PMCID: PMC7725499 DOI: 10.7554/elife.61669] [Citation(s) in RCA: 23] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Accepted: 12/03/2020] [Indexed: 12/31/2022] Open
Abstract
The switch from centrosomal microtubule-organizing centers (MTOCs) to non-centrosomal MTOCs during differentiation is poorly understood. Here, we identify AKAP6 as key component of the nuclear envelope MTOC. In rat cardiomyocytes, AKAP6 anchors centrosomal proteins to the nuclear envelope through its spectrin repeats, acting as an adaptor between nesprin-1α and Pcnt or AKAP9. In addition, AKAP6 and AKAP9 form a protein platform tethering the Golgi to the nucleus. Both Golgi and nuclear envelope exhibit MTOC activity utilizing either AKAP9, or Pcnt-AKAP9, respectively. AKAP6 is also required for formation and activity of the nuclear envelope MTOC in human osteoclasts. Moreover, ectopic expression of AKAP6 in epithelial cells is sufficient to recruit endogenous centrosomal proteins. Finally, AKAP6 is required for cardiomyocyte hypertrophy and osteoclast bone resorption activity. Collectively, we decipher the MTOC at the nuclear envelope as a bi-layered structure generating two pools of microtubules with AKAP6 as a key organizer.
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Affiliation(s)
- Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Robert Becker
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Ulrike Steffen
- Department of Internal Medicine 3 - Rheumatology and Immunology, Friedrich-Alexander-University Erlangen-Nürnberg (FAU) and Universitätsklinikum Erlangen, Erlangen, Germany
| | - Maria Sharkova
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Tilman Esser
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Jana Petzold
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Florian Billing
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany
| | - Michael S Kapiloff
- Departments of Ophthalmology and Medicine, Stanford Cardiovascular Institute, Stanford University, Palo Alto, United States
| | - George Schett
- Department of Internal Medicine 3 - Rheumatology and Immunology, Friedrich-Alexander-University Erlangen-Nürnberg (FAU) and Universitätsklinikum Erlangen, Erlangen, Germany
| | - Ingo Thievessen
- Department of Physics, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU), Erlangen, Germany.,Muscle Research Center Erlangen (MURCE), Erlangen, Germany
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5
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Vasileiou G, Vergarajauregui S, Endele S, Popp B, Büttner C, Ekici AB, Gerard M, Bramswig NC, Albrecht B, Clayton-Smith J, Morton J, Tomkins S, Low K, Weber A, Wenzel M, Altmüller J, Li Y, Wollnik B, Hoganson G, Plona MR, Cho MT, Thiel CT, Lüdecke HJ, Strom TM, Calpena E, Wilkie AOM, Wieczorek D, Engel FB, Reis A. Mutations in the BAF-Complex Subunit DPF2 Are Associated with Coffin-Siris Syndrome. Am J Hum Genet 2018; 102:468-479. [PMID: 29429572 DOI: 10.1016/j.ajhg.2018.01.014] [Citation(s) in RCA: 58] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/04/2017] [Accepted: 01/17/2018] [Indexed: 12/31/2022] Open
Abstract
Variants affecting the function of different subunits of the BAF chromatin-remodelling complex lead to various neurodevelopmental syndromes, including Coffin-Siris syndrome. Furthermore, variants in proteins containing PHD fingers, motifs recognizing specific histone tail modifications, have been associated with several neurological and developmental-delay disorders. Here, we report eight heterozygous de novo variants (one frameshift, two splice site, and five missense) in the gene encoding the BAF complex subunit double plant homeodomain finger 2 (DPF2). Affected individuals share common clinical features described in individuals with Coffin-Siris syndrome, including coarse facial features, global developmental delay, intellectual disability, speech impairment, and hypoplasia of fingernails and toenails. All variants occur within the highly conserved PHD1 and PHD2 motifs. Moreover, missense variants are situated close to zinc binding sites and are predicted to disrupt these sites. Pull-down assays of recombinant proteins and histone peptides revealed that a subset of the identified missense variants abolish or impaire DPF2 binding to unmodified and modified H3 histone tails. These results suggest an impairment of PHD finger structural integrity and cohesion and most likely an aberrant recognition of histone modifications. Furthermore, the overexpression of these variants in HEK293 and COS7 cell lines was associated with the formation of nuclear aggregates and the recruitment of both wild-type DPF2 and BRG1 to these aggregates. Expression analysis of truncating variants found in the affected individuals indicated that the aberrant transcripts escape nonsense-mediated decay. Altogether, we provide compelling evidence that de novo variants in DPF2 cause Coffin-Siris syndrome and propose a dominant-negative mechanism of pathogenicity.
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Affiliation(s)
- Georgia Vasileiou
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Institute of Pathology, Department of Nephropathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Sabine Endele
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Bernt Popp
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Christian Büttner
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Arif B Ekici
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Marion Gerard
- Génétique Clinique, Centre Hospitalier Universitaire de Caen, Caen 14000, France
| | - Nuria C Bramswig
- Institut für Humangenetik, Universitätsklinikum Essen, Universität Duisburg-Essen, 45122 Essen, Germany
| | - Beate Albrecht
- Institut für Humangenetik, Universitätsklinikum Essen, Universität Duisburg-Essen, 45122 Essen, Germany
| | - Jill Clayton-Smith
- Manchester Centre for Genomic Medicine, Central Manchester University Hospitals NHS Foundation Trust, Manchester Academic Health Science Centre, Manchester M13 9WL, UK
| | - Jenny Morton
- West Midlands Regional Clinical Genetics Service and Birmingham Health Partners, Birmingham Women's Hospital NHS Foundation Trust, Birmingham B15 2TG, UK
| | - Susan Tomkins
- Clinical Genetics Service, University Hospitals of Bristol NHS Foundation Trust, Bristol BS2 8HW, UK
| | - Karen Low
- Clinical Genetics Service, University Hospitals of Bristol NHS Foundation Trust, Bristol BS2 8HW, UK
| | - Astrid Weber
- Merseyside and Cheshire Clinical Genetics Service, Liverpool Women's NHS Foundation Hospital Trust, Liverpool L8 7SS, UK
| | | | - Janine Altmüller
- Cologne Center for Genomics, University of Cologne, 50931 Cologne, Germany
| | - Yun Li
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - Bernd Wollnik
- Institute of Human Genetics, University Medical Center Göttingen, 37073 Göttingen, Germany
| | - George Hoganson
- Pediatric Genetics, University of Illinois Hospital, Chicago, IL 60612, USA
| | - Maria-Renée Plona
- Pediatric Genetics, University of Illinois Hospital, Chicago, IL 60612, USA
| | | | - Christian T Thiel
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - Hermann-Josef Lüdecke
- Institut für Humangenetik, Universitätsklinikum Essen, Universität Duisburg-Essen, 45122 Essen, Germany; Institut für Humangenetik, Universitätsklinikum Düsseldorf, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Tim M Strom
- Institute of Human Genetics, Helmholtz Zentrum München, Neuherberg 85764, Germany
| | - Eduardo Calpena
- Clinical Genetics Group, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Andrew O M Wilkie
- Clinical Genetics Group, MRC Weatherall Institute of Molecular Medicine, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DS, UK
| | - Dagmar Wieczorek
- Institut für Humangenetik, Universitätsklinikum Essen, Universität Duisburg-Essen, 45122 Essen, Germany; Institut für Humangenetik, Universitätsklinikum Düsseldorf, Heinrich-Heine-Universität, 40225 Düsseldorf, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Institute of Pathology, Department of Nephropathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany
| | - André Reis
- Institute of Human Genetics, Friedrich-Alexander-Universität Erlangen-Nürnberg, 91054 Erlangen, Germany.
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6
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Sun L, Hua Y, Vergarajauregui S, Diab HI, Puertollano R. Novel Role of TRPML2 in the Regulation of the Innate Immune Response. J Immunol 2015; 195:4922-32. [PMID: 26432893 DOI: 10.4049/jimmunol.1500163] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2015] [Accepted: 09/10/2015] [Indexed: 11/19/2022]
Abstract
TRPMLs (or mucolipins) constitute a family of endosomal cation channels with homology to the transient receptor potential superfamily. In mammals, the TRPML family includes three members: TRPML1-3. Although TRPML1 and TRPML3 have been well characterized, the cellular function of TRPML2 has remained elusive. To address TRPML2 function in a physiologically relevant cell type, we first analyzed TRPML2 expression in different mouse tissues and organs and found that it was predominantly expressed in lymphoid organs and kidney. Quantitative RT-PCR revealed tight regulation of TRPML2 at the transcriptional level. Although TRPML2 expression was negligible in resting macrophages, TRPML2 mRNA and protein levels dramatically increased in response to TLR activation both in vitro and in vivo. Conversely, TRPML1 and TRPML3 levels did not change upon TLR activation. Immunofluorescence analysis demonstrated that endogenous TRPML2 primarily localized to recycling endosomes both in culture and primary cells, in contrast with TRPML1 and TRPML3, which distribute to the late and early endosomal pathway, respectively. To better understand the in vivo function of TRPML2, we generated a TRPML2-knockout mouse. We found that the production of several chemokines, in particular CCL2, was severely reduced in TRPML2-knockout mice. Furthermore, TRPML2-knockout mice displayed impaired recruitment of peripheral macrophages in response to i.p. injections of LPS or live bacteria, suggesting a potential defect in the immune response. Overall, our study reveals interesting differences in the regulation and distribution of the members of the TRPML family and identifies a novel role for TRPML2 in the innate immune response.
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Affiliation(s)
- Lu Sun
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Yinan Hua
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Silvia Vergarajauregui
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Heba I Diab
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
| | - Rosa Puertollano
- Cell Biology and Physiology Center, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892
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7
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Zebrowski DC, Vergarajauregui S, Wu CC, Piatkowski T, Becker R, Leone M, Hirth S, Ricciardi F, Falk N, Giessl A, Just S, Braun T, Weidinger G, Engel FB. Developmental alterations in centrosome integrity contribute to the post-mitotic state of mammalian cardiomyocytes. eLife 2015; 4. [PMID: 26247711 PMCID: PMC4541494 DOI: 10.7554/elife.05563] [Citation(s) in RCA: 97] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Accepted: 07/30/2015] [Indexed: 12/23/2022] Open
Abstract
Mammalian cardiomyocytes become post-mitotic shortly after birth. Understanding how this occurs is highly relevant to cardiac regenerative therapy. Yet, how cardiomyocytes achieve and maintain a post-mitotic state is unknown. Here, we show that cardiomyocyte centrosome integrity is lost shortly after birth. This is coupled with relocalization of various centrosome proteins to the nuclear envelope. Consequently, postnatal cardiomyocytes are unable to undergo ciliogenesis and the nuclear envelope adopts the function as cellular microtubule organizing center. Loss of centrosome integrity is associated with, and can promote, cardiomyocyte G0/G1 cell cycle arrest suggesting that centrosome disassembly is developmentally utilized to achieve the post-mitotic state in mammalian cardiomyocytes. Adult cardiomyocytes of zebrafish and newt, which are able to proliferate, maintain centrosome integrity. Collectively, our data provide a novel mechanism underlying the post-mitotic state of mammalian cardiomyocytes as well as a potential explanation for why zebrafish and newts, but not mammals, can regenerate their heart. DOI:http://dx.doi.org/10.7554/eLife.05563.001 Muscle cells in the heart contract in regular rhythms to pump blood around the body. In humans, rats and other mammals, the vast majority of heart muscle cells lose the ability to divide shortly after birth. Therefore, the heart is unable to replace cells that are lost over the life of the individual, for example, during a heart attack. If too many of these cells are lost, the heart will be unable to pump effectively, which can lead to heart failure. Currently, the only treatment option in humans with heart failure is to perform a heart transplant. Some animals, such as newts and zebrafish, are able to replace lost heart muscle cells throughout their lifetimes. Thus, these species are able to fully regenerate their hearts even after 20% has been removed. This suggests that it might be possible to manipulate human heart muscle cells to make them divide and regenerate the heart. Recent research has suggested that structures called centrosomes, known to be required to separate copies of the DNA during cell division, are used as a hub to integrate the initial signals that determine whether a cell should divide or not. Here, Zebrowski et al. studied the centrosomes of heart muscle cells in rats, newts and zebrafish. The experiments show that the centrosomes in rat heart muscle cells are dissembled shortly after birth. Centrosomes are made of several proteins and, in the rat cells, these proteins moved to the membrane that surrounded the nucleus. On the other hand, the centrosomes in the heart muscle cells of the adult newts and zebrafish remained intact. Further experiments found that that breaking apart the centrosomes of heart muscle cells taken from newborn rats stops these cells from dividing. Zebrowski et al.'s findings suggest that the loss of centrosomes after birth is a possible reason why the hearts of adult humans and other mammals are unable to regenerate after injury. In the future, these findings may aid the development of methods to regenerate human heart muscle and new treatments that may limit division of cancer cells. DOI:http://dx.doi.org/10.7554/eLife.05563.002
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Affiliation(s)
- David C Zebrowski
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Silvia Vergarajauregui
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Chi-Chung Wu
- Institute for Biochemistry and Molecular Biology, University of Ulm, Ulm, Germany
| | - Tanja Piatkowski
- Department of Cardiac Development and Remodeling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Robert Becker
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Marina Leone
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Sofia Hirth
- Department of Medicine II, University of Ulm, Ulm, Germany
| | - Filomena Ricciardi
- Department of Developmental Genetics, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Nathalie Falk
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Andreas Giessl
- Department of Biology, Animal Physiology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
| | - Steffen Just
- Department of Medicine II, University of Ulm, Ulm, Germany
| | - Thomas Braun
- Department of Cardiac Development and Remodeling, Max Planck Institute for Heart and Lung Research, Bad Nauheim, Germany
| | - Gilbert Weidinger
- Institute for Biochemistry and Molecular Biology, University of Ulm, Ulm, Germany
| | - Felix B Engel
- Experimental Renal and Cardiovascular Research, Department of Nephropathology, Institute of Pathology, Friedrich-Alexander-Universität Erlangen-Nürnberg, Erlangen, Germany
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8
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Bañón-Rodríguez I, Gálvez-Santisteban M, Vergarajauregui S, Bosch M, Borreguero-Pascual A, Martín-Belmonte F. EGFR controls IQGAP basolateral membrane localization and mitotic spindle orientation during epithelial morphogenesis. EMBO J 2014; 33:129-45. [PMID: 24421325 DOI: 10.1002/embj.201385946] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022] Open
Abstract
Establishing the correct orientation of the mitotic spindle is an essential step in epithelial cell division in order to ensure that epithelial tubules form correctly during organ development and regeneration. While recent findings have identified some of the molecular mechanisms that underlie spindle orientation, many aspects of this process remain poorly understood. Here, we have used the 3D-MDCK model system to demonstrate a key role for a newly identified protein complex formed by IQGAP1 and the epithelial growth factor receptor (EGFR) in controlling the orientation of the mitotic spindle. IQGAP1 is a scaffolding protein that regulates many cellular pathways, from cell-cell adhesion to microtubule organization, and its localization in the basolateral membrane ensures correct spindle orientation. Through its IQ motifs, IQGAP1 binds to EGFR, which is responsible for maintaining IQGAP1 in the basolateral membrane domain. Silencing IQGAP1, or disrupting the basolateral localization of either IQGAP1 or EGFR, results in a non-polarized distribution of NuMA, mitotic spindle misorientation and defects in single lumen formation.
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Affiliation(s)
- Inmaculada Bañón-Rodríguez
- Centro de Biología Molecular Severo Ochoa Consejo Superior de Investigaciones Científicas (CSIC), Madrid, Spain
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9
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Lalioti VS, Vergarajauregui S, Villasante A, Pulido D, Sandoval IV. C6orf89 encodes three distinct HDAC enhancers that function in the nucleolus, the golgi and the midbody. J Cell Physiol 2013; 228:1907-21. [PMID: 23460338 DOI: 10.1002/jcp.24355] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2012] [Accepted: 02/12/2013] [Indexed: 11/06/2022]
Abstract
We report here that C6orf89, which encodes a protein that interacts with bombesin receptor subtype-3 and accelerates cell cycle progression and wound repair in human bronchial epithelial cells (Liu et al., 2011, PLoS ONE 6: e23072), encodes one soluble and two type II membrane proteins that function as histone deacetylases (HDAC) enhancers. Soluble 34/64sp is selectively targeted to the nucleolus and is retained in nucleolar organiser regions (NORs) in mitotic cells. Nucleolar 34/64sp is integrated into the ribosomal gene transcription machinery, colocalises and coimmunoprecipitates with the Pol I transcription factor UBF, and undergoes a dramatic relocalisation to the nucleolus upon the arrest of rDNA transcription, protein synthesis and PI3K/mTORC2 signalling. Membrane 42/116mp localises to the Golgi and the midbody, and its controlled ectopic expression provokes the disruption of the Golgi cisternae and hinders the separation of daughter cells and the completion of mitosis. The latter effect is also produced by the microinjection of an affinity-purified amfion antibody. The identification of C60rf89 as a gene that encodes three distinct proteins with the capacity to enhance the activity of histone deacetylases (HDACs) in the nucleolus, the Golgi and the midbody provides new information regarding the components of the acetylome and their capacity to interact with different functional groups in the cell.
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Affiliation(s)
- Vasiliki S Lalioti
- Centro de Biología Molecular Severo Ochoa, CSIC, Universidad Autónoma de Madrid, Departamento Biología Celular e Inmunología, Cantoblanco, Madrid, Spain.
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10
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Gálvez-Santisteban M, Rodriguez-Fraticelli AE, Bryant DM, Vergarajauregui S, Yasuda T, Bañón-Rodríguez I, Bernascone I, Datta A, Spivak N, Young K, Slim CL, Brakeman PR, Fukuda M, Mostov KE, Martín-Belmonte F. Synaptotagmin-like proteins control the formation of a single apical membrane domain in epithelial cells. Nat Cell Biol 2012; 14:838-49. [PMID: 22820376 PMCID: PMC3433678 DOI: 10.1038/ncb2541] [Citation(s) in RCA: 106] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2011] [Accepted: 06/14/2012] [Indexed: 12/16/2022]
Abstract
The formation of epithelial tissues requires both the generation of apical-basal polarity and the coordination of this polarity between neighbouring cells to form a central lumen. During de novo lumen formation, vectorial membrane transport contributes to the formation of a singular apical membrane, resulting in the contribution of each cell to only a single lumen. Here, from a functional screen for genes required for three-dimensional epithelial architecture, we identify key roles for synaptotagmin-like proteins 2-a and 4-a (Slp2-a/4-a) in the generation of a single apical surface per cell. Slp2-a localizes to the luminal membrane in a PtdIns(4,5)P(2)-dependent manner, where it targets Rab27-loaded vesicles to initiate a single lumen. Vesicle tethering and fusion is controlled by Slp4-a, in conjunction with Rab27/Rab3/Rab8 and the SNARE syntaxin-3. Together, Slp2-a/4-a coordinate the spatiotemporal organization of vectorial apical transport to ensure that only a single apical surface, and thus the formation of a single lumen, occurs per cell.
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Affiliation(s)
- Manuel Gálvez-Santisteban
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, C/Nicolás Cabrera 1, Madrid 28049, Spain
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11
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Vergarajauregui S, Martina JA, Puertollano R. LAPTMs regulate lysosomal function and interact with mucolipin 1: new clues for understanding mucolipidosis type IV. J Cell Sci 2011; 124:459-68. [PMID: 21224396 PMCID: PMC3022000 DOI: 10.1242/jcs.076240] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 10/08/2010] [Indexed: 11/20/2022] Open
Abstract
Loss-of-function mutations in mucolipin 1 (MCOLN1) result in mucolipidosis type IV (MLIV), a lysosomal storage disorder characterized by severe mental and psychomotor retardation. MCOLN1 is a lysosomal ion channel that belongs to the transient receptor potential (TRP) superfamily. To better understand the cellular function of MCOLN1, a split-ubiquitin yeast two-hybrid screen was performed with the purpose of revealing new MCOLN1 interaction partners. The screen identified two members of the lysosome-associated protein transmembrane (LAPTM) family as novel interaction partners of MCOLN1. The binding between MCOLN1 and LAPTM members (LAPTMs) was confirmed by co-immunoprecipitation and yeast two-hybrid assays. In addition, MCOLN1 and LAPTMs extensively colocalize at late endosomes and lysosomes. Overexpression of LAPTM4b caused enlargement of lysosomes and defective lysosomal degradation, indicating that LAPTMs are important for proper lysosomal function. Interestingly, lysosomal swelling induced by LAPTM4b was rescued by expression of MCOLN1, suggesting a functional connection between the two proteins. Finally, depletion of endogenous LAPTMs by siRNA induced accumulation of concentric multi-lamellar structures and electron-dense inclusions that closely resemble the structures found in MLIV cells. Overall, our data provide new insight into the molecular mechanisms of MCOLN1 function and suggest a potential role for LAPTMs in MLIV pathogenesis.
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Affiliation(s)
- Silvia Vergarajauregui
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Jose A. Martina
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Rosa Puertollano
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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12
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Rodriguez-Fraticelli AE, Vergarajauregui S, Eastburn DJ, Datta A, Alonso MA, Mostov K, Martín-Belmonte F. The Cdc42 GEF Intersectin 2 controls mitotic spindle orientation to form the lumen during epithelial morphogenesis. ACTA ACUST UNITED AC 2010; 189:725-38. [PMID: 20479469 PMCID: PMC2872911 DOI: 10.1083/jcb.201002047] [Citation(s) in RCA: 110] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Epithelial organs are made of tubes and cavities lined by a monolayer of polarized cells that enclose the central lumen. Lumen formation is a crucial step in the formation of epithelial organs. The Rho guanosine triphosphatase (GTPase) Cdc42, which is a master regulator of cell polarity, regulates the formation of the central lumen in epithelial morphogenesis. However, how Cdc42 is regulated during this process is still poorly understood. Guanine nucleotide exchange factors (GEFs) control the activation of small GTPases. Using the three-dimensional Madin-Darby canine kidney model, we have identified a Cdc42-specific GEF, Intersectin 2 (ITSN2), which localizes to the centrosomes and regulates Cdc42 activation during epithelial morphogenesis. Silencing of either Cdc42 or ITSN2 disrupts the correct orientation of the mitotic spindle and normal lumen formation, suggesting a direct relationship between these processes. Furthermore, we demonstrated this direct relationship using LGN, a component of the machinery for mitotic spindle positioning, whose disruption also results in lumen formation defects.
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13
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Vergarajauregui S, Martina JA, Puertollano R. Identification of the penta-EF-hand protein ALG-2 as a Ca2+-dependent interactor of mucolipin-1. J Biol Chem 2009; 284:36357-36366. [PMID: 19864416 DOI: 10.1074/jbc.m109.047241] [Citation(s) in RCA: 71] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Loss of function mutations in mucolipin-1 (MCOLN1) have been linked to mucolipidosis type IV (MLIV), a recessive lysosomal storage disease characterized by severe neurological and ophthalmological abnormalities. MCOLN1 is an ion channel that regulates membrane transport along the endolysosomal pathway. It has been suggested that MCOLN1 participates in several Ca(2+)-dependent processes, including fusion of lysosomes with the plasma membrane, fusion of late endosomes and autophagosomes with lysosomes, and lysosomal biogenesis. Here, we searched for proteins that interact with MCOLN1 in a Ca(2+)-dependent manner. We found that the penta-EF-hand protein ALG-2 binds to the NH-terminal cytosolic tail of MCOLN1. The interaction is direct, strictly dependent on Ca(2+), and mediated by a patch of charged and hydrophobic residues located between MCOLN1 residues 37 and 49. We further show that MCOLN1 and ALG-2 co-localize to enlarged endosomes induced by overexpression of an ATPase-defective dominant-negative form of Vps4B (Vps4B(E235Q)). In agreement with the proposed role of MCOLN1 in the regulation of fusion/fission events, we found that overexpression of MCOLN1 caused accumulation of enlarged, aberrant endosomes that contain both early and late endosome markers. Interestingly, aggregation of abnormal endosomes was greatly reduced when the ALG-2-binding domain in MCOLN1 was mutated, suggesting that ALG-2 regulates MCOLN1 function. Overall, our data provide new insight into the molecular mechanisms that regulate MCOLN1 activity. We propose that ALG-2 acts as a Ca(2+) sensor that modulates the function of MCOLN1 along the late endosomal-lysosomal pathway.
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Affiliation(s)
- Silvia Vergarajauregui
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Jose A Martina
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892
| | - Rosa Puertollano
- Laboratory of Cell Biology, NHLBI, National Institutes of Health, Bethesda, Maryland 20892.
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14
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Lalioti VS, Vergarajauregui S, Tsuchiya Y, Hernandez-Tiedra S, Sandoval IV. Daxx functions as a scaffold of a protein assembly constituted by GLUT4, JNK1 and KIF5B. J Cell Physiol 2009; 218:416-26. [DOI: 10.1002/jcp.21614] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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15
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Vergarajauregui S, Connelly PS, Daniels MP, Puertollano R. Autophagic dysfunction in mucolipidosis type IV patients. Hum Mol Genet 2008; 17:2723-37. [PMID: 18550655 PMCID: PMC2515373 DOI: 10.1093/hmg/ddn174] [Citation(s) in RCA: 138] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2008] [Revised: 05/20/2008] [Accepted: 06/10/2008] [Indexed: 12/18/2022] Open
Abstract
Mutations in Mucolipin 1 (MCOLN1) have been linked to mucolipidosis type IV (MLIV), a lysosomal storage disease characterized by several neurological and ophthalmological abnormalities. It has been proposed that MCOLN1 might regulate transport of membrane components in the late endosomal-lysosomal pathway; however, the mechanisms by which defects of MCOLN1 function result in mental and psychomotor retardation remain largely unknown. In this study, we show constitutive activation of autophagy in fibroblasts obtained from MLIV patients. Accumulation of autophagosomes in MLIV cells was due to the increased de novo autophagosome formation and to delayed fusion of autophagosomes with late endosomes/lysosomes. Impairment of the autophagic pathway led to increased levels and aggregation of p62, suggesting that abnormal accumulation of ubiquitin proteins may contribute to the neurodegeneration observed in MLIV patients. In addition, we found that delivery of platelet-derived growth factor receptor to lysosomes is delayed in MCOLN1-deficient cells, suggesting that MCOLN1 is necessary for efficient fusion of both autophagosomes and late endosomes with lysosomes. Our data are in agreement with recent evidence showing that autophagic defects may be a common characteristic of many neurodegenerative disorders.
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Affiliation(s)
| | - Patricia S. Connelly
- Electron Microscopy Core Facility, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
| | - Mathew P. Daniels
- Electron Microscopy Core Facility, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA
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16
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Abstract
Mucolipidosis IV (MLIV) is a lysosomal storage disorder characterized by severe neurological and ophthalmologic abnormalities. In contrast with most lysosomal storage disorders, which are attributed to the absence of specific lysosomal hydrolases, accumulation of material in MLIV results from defects in membrane transport along the late endocytic pathway. Mutations in MCOLN1 are the cause of MLIV; however, how the lack of MCOLN1 function ultimately leads to neurodegeneration remains largely unknown. We found that MCOLN1 is required for efficient fusion of both late endosomes and autophagosomes with lysosomes. Impaired autophagosome degradation results in accumulation of autophagosomes in MLIV fibroblasts. In addition, we found increased levels and aggregation of p62, suggesting that abnormal accumulation of ubiquitinated protein inclusions may contribute to the neurodegenerative phenotype observed in MLIV patients. These findings corroborate recent evidence indicating that defects in autophagy may be a common feature of many neurodegenerative disorders.
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Affiliation(s)
- Silvia Vergarajauregui
- Laboratory of Cell Biology, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, Maryland 20892, USA
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17
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Abstract
Endocytic trafficking plays an important role in the regulation of the epidermal growth factor receptor (EGFR). To address if cellular kinases regulate EGFR internalization, we used anisomycin, a potent activator of kinase cascades in mammalian cells, especially the stress-activated mitogen-activated protein (MAP) kinase subtypes. Here, we report that activation of p38 MAP kinase by anisomycin is sufficient to induce internalization of EGFR. Anisomycin and EGF employ different mechanisms to promote EGFR endocytosis as anisomycin-induced internalization does not require tyrosine kinase activity or ubiquitination of the receptor. In addition, anisomycin treatment did not result in delivery and degradation of EGFR at lysosomes. Incubation with a specific inhibitor of p38, or depletion of endogenous p38 by small interfering RNAs, abolished anisomycin-induced internalization of EGFR while having no effect on transferrin endocytosis, indicating that the effect of p38 activation on EGFR endocytosis is specific. Interestingly, inhibition of p38 activation also abolished endocytosis of EGFR induced by UV radiation. Our results reveal a novel role for p38 in the regulation of EGFR endocytosis and suggest that stimulation of EGFR internalization by p38 might represent a general mechanism to prevent generation of proliferative or anti-apoptotic signals under stress conditions.
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18
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Abstract
Mutations in the mucolipin-1 gene have been linked to mucolipidosis type IV, a lysosomal storage disorder characterized by severe neurological and ophthalmologic abnormalities. Mucolipin-1 is a membrane protein containing six putative transmembrane domains with both its N- and C-termini localized facing the cytosol. To gain information on the sorting motifs that mediate the trafficking of this protein to lysosomes, we have generated chimeras in which the N- and C- terminal tail portions of mucolipin-1 were fused to a reporter gene. In this article, we report the identification of two separate di-leucine-type motifs that co-operate to regulate the transport of mucolipin-1 to lysosomes. One di-leucine motif is positioned at the N-terminal cytosolic tail and mediates direct transport to lysosomes, whereas the other di-leucine motif is found at the C-terminal tail and functions as an adaptor protein 2-dependent internalization motif. We have also found that the C-terminal tail of mucolipin-1 is palmitoylated and that this modification might regulate the efficiency of endocytosis. Finally, the mutagenesis of both di-leucine motifs abrogated lysosomal accumulation and resulted in cell-surface redistribution of mucolipin-1. Taken together, these results reveal novel information regarding the motifs that regulate mucolipin-1 trafficking and suggest a role for palmitoylation in protein sorting.
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19
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Lalioti VS, Vergarajauregui S, Pulido D, Sandoval IV. The insulin-sensitive glucose transporter, GLUT4, interacts physically with Daxx. Two proteins with capacity to bind Ubc9 and conjugated to SUMO1. J Biol Chem 2002; 277:19783-91. [PMID: 11842083 DOI: 10.1074/jbc.m110294200] [Citation(s) in RCA: 62] [Impact Index Per Article: 2.8] [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: 11/06/2022] Open
Abstract
In this study we have used the yeast two-hybrid system to identify proteins that interact with the carboxyl-cytoplasmic domain (residues 464-509) of the insulin-sensitive glucose transporter GLUT4 (C-GLUT4). Using as bait C-GLUT4, we have isolated the carboxyl domain of Daxx (C-Daxx), the adaptor protein associated with the Fas and the type II TGF-beta (TbetaRII) receptors (1,2 ). The two-hybrid interaction between C-GLUT4 and C-Daxx is validated by the ability of in vitro translated C-GLUT4 to interact with in vitro translated full-length Daxx and C-Daxx. C-Daxx does not interact with the C-cytoplasmic domain of GLUT1, the ubiquitous glucose transporter homologous to GLUT4. Replacement of alanine and serine for the dileucine pair (Leu(489)-Leu(490)) critical for targeting GLUT4 from the trans-Golgi network to the perinuclear intracellular store as well as for its surface internalization by endocytosis inhibits 2-fold the interaction of C-GLUT4 with Daxx. Daxx is pulled down with GLUT4 immunoprecipitated from lysates of 3T3-L1 fibroblasts stably transfected with GLUT4 and 3T3-L1 adipocytes expressing physiological levels of the two proteins. Similarly, GLUT4 is recovered with anti-Daxx immunoprecipitates. Using an established cell fractionation procedure we present evidence for the existence of two distinct intracellular Daxx pools in the nucleus and low density microsomes. Confocal immunofluorescence microscopy studies localize Daxx to promyelocytic leukemia nuclear bodies and punctate cytoplasmic structures, often organized in strings and underneath the plasma membrane. Daxx and GLUT4 are SUMOlated as shown by their reaction with an anti-SUMO1 antibody and by the ability of this antibody to pull down Daxx and GLUT4.
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Affiliation(s)
- Vassiliki S Lalioti
- Centro de Biologia Molecular Severo Ochoa, Consejo Superior de Investigaciones Cientificas, Universidad Autónoma de Madrid, Madrid 28049, Spain
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20
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Abstract
The trafficking of the insulin-sensitive glucose transporter, GLUT4, is the paradigm of how cells control the movement of membrane proteins through intricate pathways of transport in response to external stimuli, and how, by doing so, regulate their function. The GLUT4 intracellularly sequestered in resting adipocytes and muscle cells becomes exposed on their surface in response to an increase in insulin levels and muscle contraction, where it facilitates glucose uptake. Ceasing of the stimuli is followed by endocytosis of the GLUT4 molecules exposed on the plasma membrane and their recycling to the original stores, where they are retained. This review discusses current understanding of the organelles that host GLUT4 and the motifs that mediate its trafficking.
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Affiliation(s)
- V Lalioti
- Centro de Biología Molecular Severo Ochoa, Consejo Superior de Investigaciones Científicas, Universidad Autónoma de Madrid, Cantoblanco, Spain
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