1
|
Papadopoulos S, Tinschert R, Papadopoulos I, Gerloff X, Schmitz F. Analytical Post-Embedding Immunogold-Electron Microscopy with Direct Gold-Labelled Monoclonal Primary Antibodies against RIBEYE A- and B-Domain Suggests a Refined Model of Synaptic Ribbon Assembly. Int J Mol Sci 2024; 25:7443. [PMID: 39000549 PMCID: PMC11242772 DOI: 10.3390/ijms25137443] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2024] [Revised: 07/02/2024] [Accepted: 07/04/2024] [Indexed: 07/16/2024] Open
Abstract
Synaptic ribbons are the eponymous specializations of continuously active ribbon synapses. They are primarily composed of the RIBEYE protein that consists of a unique amino-terminal A-domain and carboxy-terminal B-domain that is largely identical to the ubiquitously expressed transcriptional regulator protein CtBP2. Both RIBEYE A-domain and RIBEYE B-domain are essential for the assembly of the synaptic ribbon, as shown by previous analyses of RIBEYE knockout and knockin mice and related investigations. How exactly the synaptic ribbon is assembled from RIBEYE subunits is not yet clear. To achieve further insights into the architecture of the synaptic ribbon, we performed analytical post-embedding immunogold-electron microscopy with direct gold-labelled primary antibodies against RIBEYE A-domain and RIBEYE B-domain for improved ultrastructural resolution. With direct gold-labelled monoclonal antibodies against RIBEYE A-domain and RIBEYE B-domain, we found that both domains show a very similar localization within the synaptic ribbon of mouse photoreceptor synapses, with no obvious differential gradient between the centre and surface of the synaptic ribbon. These data favour a model of the architecture of the synaptic ribbon in which the RIBEYE A-domain and RIBEYE B-domain are located similar distances from the midline of the synaptic ribbon.
Collapse
Affiliation(s)
- Stella Papadopoulos
- Institute of Anatomy, Department of Neuroanatomy, Medical School, Saarland University, 66421 Homburg, Germany
| | - René Tinschert
- Institute of Anatomy, Department of Neuroanatomy, Medical School, Saarland University, 66421 Homburg, Germany
| | | | - Xenia Gerloff
- Mathematical Institute, University of Bonn, 53115 Bonn, Germany
| | - Frank Schmitz
- Institute of Anatomy, Department of Neuroanatomy, Medical School, Saarland University, 66421 Homburg, Germany
| |
Collapse
|
2
|
Goradia N, Werner S, Mullapudi E, Greimeier S, Bergmann L, Lang A, Mertens H, Węglarz A, Sander S, Chojnowski G, Wikman H, Ohlenschläger O, von Amsberg G, Pantel K, Wilmanns M. Master corepressor inactivation through multivalent SLiM-induced polymerization mediated by the oncogene suppressor RAI2. Nat Commun 2024; 15:5241. [PMID: 38898011 PMCID: PMC11187106 DOI: 10.1038/s41467-024-49488-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2023] [Accepted: 06/05/2024] [Indexed: 06/21/2024] Open
Abstract
While the elucidation of regulatory mechanisms of folded proteins is facilitated due to their amenability to high-resolution structural characterization, investigation of these mechanisms in disordered proteins is more challenging due to their structural heterogeneity, which can be captured by a variety of biophysical approaches. Here, we used the transcriptional master corepressor CtBP, which binds the putative metastasis suppressor RAI2 through repetitive SLiMs, as a model system. Using cryo-electron microscopy embedded in an integrative structural biology approach, we show that RAI2 unexpectedly induces CtBP polymerization through filaments of stacked tetrameric CtBP layers. These filaments lead to RAI2-mediated CtBP nuclear foci and relieve its corepressor function in RAI2-expressing cancer cells. The impact of RAI2-mediated CtBP loss-of-function is illustrated by the analysis of a diverse cohort of prostate cancer patients, which reveals a substantial decrease in RAI2 in advanced treatment-resistant cancer subtypes. As RAI2-like SLiM motifs are found in a wide range of organisms, including pathogenic viruses, our findings serve as a paradigm for diverse functional effects through multivalent interaction-mediated polymerization by disordered proteins in healthy and diseased conditions.
Collapse
Affiliation(s)
- Nishit Goradia
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, 22607, Hamburg, Germany
| | - Stefan Werner
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany
- University Medical Center Hamburg-Eppendorf, Mildred Scheel Cancer Career Center HaTriCS4, Martinistrasse 52, 20246, Hamburg, Germany
| | - Edukondalu Mullapudi
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, 22607, Hamburg, Germany
| | - Sarah Greimeier
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany
| | - Lina Bergmann
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany
| | - Andras Lang
- Leibniz Institute on Aging, Fritz-Lipmann-Institute, Beutenbergstraße 11, 07745, Jena, Germany
| | - Haydyn Mertens
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, 22607, Hamburg, Germany
| | - Aleksandra Węglarz
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany
| | - Simon Sander
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany
| | - Grzegorz Chojnowski
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, 22607, Hamburg, Germany
| | - Harriet Wikman
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany
| | - Oliver Ohlenschläger
- Leibniz Institute on Aging, Fritz-Lipmann-Institute, Beutenbergstraße 11, 07745, Jena, Germany
| | - Gunhild von Amsberg
- Martini Clinic, Martinistrasse 52, 20246, Hamburg, Germany
- Department of Hematology and Oncology, University Medical Center Hamburg-Eppendorf, Hamburg, Germany
| | - Klaus Pantel
- University Medical Center Hamburg-Eppendorf, Department of Tumor Biology, University Cancer Center Hamburg, Martinistrasse 52, 20246, Hamburg, Germany.
| | - Matthias Wilmanns
- European Molecular Biology Laboratory, Hamburg Unit, Notkestrasse 85, 22607, Hamburg, Germany.
- University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246, Hamburg, Germany.
| |
Collapse
|
3
|
Huang M, Li Y, Li Y, Liu S. C-Terminal Binding Protein: Regulator between Viral Infection and Tumorigenesis. Viruses 2024; 16:988. [PMID: 38932279 PMCID: PMC11209466 DOI: 10.3390/v16060988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2024] [Revised: 06/16/2024] [Accepted: 06/18/2024] [Indexed: 06/28/2024] Open
Abstract
C-terminal binding protein (CtBP), a transcriptional co-repressor, significantly influences cellular signaling, impacting various biological processes including cell proliferation, differentiation, apoptosis, and immune responses. The CtBP family comprises two highly conserved proteins, CtBP1 and CtBP2, which have been shown to play critical roles in both tumorigenesis and the regulation of viral infections. Elevated CtBP expression is noted in various tumor tissues, promoting tumorigenesis, invasiveness, and metastasis through multiple pathways. Additionally, CtBP's role in viral infections varies, exhibiting differing or even opposing effects depending on the virus. This review synthesizes the advances in CtBP's function research in viral infections and virus-associated tumorigenesis, offering new insights into potential antiviral and anticancer strategies.
Collapse
Affiliation(s)
- Meihui Huang
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (M.H.); (Y.L.); (Y.L.)
| | - Yucong Li
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (M.H.); (Y.L.); (Y.L.)
| | - Yuxiao Li
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (M.H.); (Y.L.); (Y.L.)
| | - Shuiping Liu
- Xiangya School of Medicine, Central South University, Changsha 410013, China; (M.H.); (Y.L.); (Y.L.)
- Department of Microbiology, School of Basic Medical Science, Central South University, Changsha 410013, China
| |
Collapse
|
4
|
Raicu AM, Kadiyala D, Niblock M, Jain A, Yang Y, Bird KM, Bertholf K, Seenivasan A, Siddiq M, Arnosti DN. The Cynosure of CtBP: Evolution of a Bilaterian Transcriptional Corepressor. Mol Biol Evol 2023; 40:msad003. [PMID: 36625090 PMCID: PMC9907507 DOI: 10.1093/molbev/msad003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2022] [Revised: 12/16/2022] [Accepted: 01/03/2023] [Indexed: 01/11/2023] Open
Abstract
Evolution of sequence-specific transcription factors clearly drives lineage-specific innovations, but less is known about how changes in the central transcriptional machinery may contribute to evolutionary transformations. In particular, transcriptional regulators are rich in intrinsically disordered regions that appear to be magnets for evolutionary innovation. The C-terminal Binding Protein (CtBP) is a transcriptional corepressor derived from an ancestral lineage of alpha hydroxyacid dehydrogenases; it is found in mammals and invertebrates, and features a core NAD-binding domain as well as an unstructured C-terminus (CTD) of unknown function. CtBP can act on promoters and enhancers to repress transcription through chromatin-linked mechanisms. Our comparative phylogenetic study shows that CtBP is a bilaterian innovation whose CTD of about 100 residues is present in almost all orthologs. CtBP CTDs contain conserved blocks of residues and retain a predicted disordered property, despite having variations in the primary sequence. Interestingly, the structure of the C-terminus has undergone radical transformation independently in certain lineages including flatworms and nematodes. Also contributing to CTD diversity is the production of myriad alternative RNA splicing products, including the production of "short" tailless forms of CtBP in Drosophila. Additional diversity stems from multiple gene duplications in vertebrates, where up to five CtBP orthologs have been observed. Vertebrate lineages show fewer major modifications in the unstructured CTD, possibly because gene regulatory constraints of the vertebrate body plan place specific constraints on this domain. Our study highlights the rich regulatory potential of this previously unstudied domain of a central transcriptional regulator.
Collapse
Affiliation(s)
- Ana-Maria Raicu
- Cell and Molecular Biology Program, Michigan State University, East Lansing, Michigan
| | - Dhruva Kadiyala
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | - Madeline Niblock
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | | | - Yahui Yang
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | - Kalynn M Bird
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | - Kayla Bertholf
- Biochemistry and Molecular Biology Program, College of Wooster
| | - Akshay Seenivasan
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| | - Mohammad Siddiq
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, Michigan
| | - David N Arnosti
- Cell and Molecular Biology Program, Michigan State University, East Lansing, Michigan
- Department of Biochemistry and Molecular Biology, Michigan State University, East Lansing, Michigan
| |
Collapse
|