1
|
Stress vulnerability shapes disruption of motor cortical neuroplasticity. Transl Psychiatry 2022; 12:91. [PMID: 35246507 PMCID: PMC8897461 DOI: 10.1038/s41398-022-01855-8] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/15/2021] [Revised: 02/06/2022] [Accepted: 02/08/2022] [Indexed: 02/06/2023] Open
Abstract
Chronic stress is a major cause of neuropsychiatric conditions such as depression. Stress vulnerability varies individually in mice and humans, measured by behavioral changes. In contrast to affective symptoms, motor retardation as a consequence of stress is not well understood. We repeatedly imaged dendritic spines of the motor cortex in Thy1-GFP M mice before and after chronic social defeat stress. Susceptible and resilient phenotypes were discriminated by symptom load and their motor learning abilities were assessed by a gross and fine motor task. Stress phenotypes presented individual short- and long-term changes in the hypothalamic-pituitary-adrenal axis as well as distinct patterns of altered motor learning. Importantly, stress was generally accompanied by a marked reduction of spine density in the motor cortex and spine dynamics depended on the stress phenotype. We found astrogliosis and altered microglia morphology along with increased microglia-neuron interaction in the motor cortex of susceptible mice. In cerebrospinal fluid, proteomic fingerprints link the behavioral changes and structural alterations in the brain to neurodegenerative disorders and dysregulated synaptic homeostasis. Our work emphasizes the importance of synaptic integrity and the risk of neurodegeneration within depression as a threat to brain health.
Collapse
|
2
|
Li D, McIntosh CS, Mastaglia FL, Wilton SD, Aung-Htut MT. Neurodegenerative diseases: a hotbed for splicing defects and the potential therapies. Transl Neurodegener 2021; 10:16. [PMID: 34016162 PMCID: PMC8136212 DOI: 10.1186/s40035-021-00240-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Accepted: 04/23/2021] [Indexed: 12/14/2022] Open
Abstract
Precursor messenger RNA (pre-mRNA) splicing is a fundamental step in eukaryotic gene expression that systematically removes non-coding regions (introns) and ligates coding regions (exons) into a continuous message (mature mRNA). This process is highly regulated and can be highly flexible through a process known as alternative splicing, which allows for several transcripts to arise from a single gene, thereby greatly increasing genetic plasticity and the diversity of proteome. Alternative splicing is particularly prevalent in neuronal cells, where the splicing patterns are continuously changing to maintain cellular homeostasis and promote neurogenesis, migration and synaptic function. The continuous changes in splicing patterns and a high demand on many cis- and trans-splicing factors contribute to the susceptibility of neuronal tissues to splicing defects. The resultant neurodegenerative diseases are a large group of disorders defined by a gradual loss of neurons and a progressive impairment in neuronal function. Several of the most common neurodegenerative diseases involve some form of splicing defect(s), such as Alzheimer's disease, Parkinson's disease and spinal muscular atrophy. Our growing understanding of RNA splicing has led to the explosion of research in the field of splice-switching antisense oligonucleotide therapeutics. Here we review our current understanding of the effects alternative splicing has on neuronal differentiation, neuronal migration, synaptic maturation and regulation, as well as the impact on neurodegenerative diseases. We will also review the current landscape of splice-switching antisense oligonucleotides as a therapeutic strategy for a number of common neurodegenerative disorders.
Collapse
Affiliation(s)
- Dunhui Li
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, Western Australia, Australia.,Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, The University of Western Australia, Perth, Western Australia, Australia
| | - Craig Stewart McIntosh
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, Western Australia, Australia.,Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, The University of Western Australia, Perth, Western Australia, Australia
| | - Frank Louis Mastaglia
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, Western Australia, Australia.,Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, The University of Western Australia, Perth, Western Australia, Australia
| | - Steve Donald Wilton
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, Western Australia, Australia.,Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, The University of Western Australia, Perth, Western Australia, Australia
| | - May Thandar Aung-Htut
- Centre for Molecular Medicine and Innovative Therapeutics, Health Futures Institute, Murdoch University, Perth, Western Australia, Australia. .,Perron Institute for Neurological and Translational Science, Centre for Neuromuscular and Neurological Disorders, The University of Western Australia, Perth, Western Australia, Australia.
| |
Collapse
|
3
|
Hsu CP, Moghadaszadeh B, Hartwig JH, Beggs AH. Sarcomeric and nonmuscle α-actinin isoforms exhibit differential dynamics at skeletal muscle Z-lines. Cytoskeleton (Hoboken) 2018; 75:213-228. [PMID: 29518289 PMCID: PMC5943145 DOI: 10.1002/cm.21442] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2017] [Revised: 03/02/2018] [Accepted: 03/05/2018] [Indexed: 01/12/2023]
Abstract
The α-actinin proteins are a highly conserved family of actin crosslinkers that mediate interactions between several cytoskeletal and sarcomeric proteins. Nonsarcomeric α-actinin-1 and α-actinin-4 crosslink actin filaments in the cytoskeleton, while sarcomeric α-actinin-2 and α-actinin-3 serve a crucial role in anchoring actin filaments to the muscle Z-line. To assess the difference in turnover dynamics and structure/function properties between the α-actinin isoforms at the sarcomeric Z-line, we used Fluorescence Recovery After Photobleaching (FRAP) in primary myofiber cultures. We found that the recovery kinetics of these proteins followed three distinct patterns: α-actinin-2/α-actinin-3 had the slowest turn over, α-actinin-1 recovered to an intermediate degree, and α-actinin-4 had the fastest recovery. Interestingly, the isoforms' patterns of recovery were reversed at adhesion plaques in fibroblasts. This disparity suggests that the different α-actinin isoforms have unique association kinetics in myofibers and that nonmuscle isoform interactions are more dynamic at the sarcomeric Z-line. Protein domain-specific investigations using α-actinin-2/4 chimeric proteins showed that differential dynamics between sarcomeric and nonmuscle isoforms are regulated by cooperative interactions between the N-terminal actin-binding domain, the spectrin-like linker region and the C-terminal calmodulin-like EF hand domain. Together, these findings demonstrate that α-actinin isoforms are unique in binding dynamics at the Z-line and suggest differentially evolved interactive and Z-line association capabilities of each functional domain.
Collapse
Affiliation(s)
- Cynthia P Hsu
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - Behzad Moghadaszadeh
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| | - John H Hartwig
- Translational Medicine Division, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA 02115, USA
| | - Alan H Beggs
- Division of Genetics and Genomics, The Manton Center for Orphan Disease Research, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02115, USA
| |
Collapse
|
4
|
Karlsson G, Persson C, Mayzel M, Hedenström M, Backman L. Solution structure of the calmodulin-like C-terminal domain of Entamoeba α-actinin2. Proteins 2016; 84:461-6. [PMID: 26800385 DOI: 10.1002/prot.24992] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2015] [Revised: 01/11/2016] [Accepted: 01/12/2016] [Indexed: 11/12/2022]
Abstract
Cell motility is dependent on a dynamic meshwork of actin filaments that is remodelled continuously. A large number of associated proteins that are severs, cross-links, or caps the filament ends have been identified and the actin cross-linker α-actinin has been implied in several important cellular processes. In Entamoeba histolytica, the etiological agent of human amoebiasis, α-actinin is believed to be required for infection. To better understand the role of α-actinin in the infectious process we have determined the solution structure of the C-terminal calmodulin-like domain using NMR. The final structure ensemble of the apo form shows two lobes, that both resemble other pairs of calcium-binding EF-hand motifs, connected with a mobile linker.
Collapse
Affiliation(s)
- Göran Karlsson
- Swedish NMR Centre at the University of Gothenburg, PO Box 465, Gothenburg, SE-40530, Sweden
| | - Cecilia Persson
- Swedish NMR Centre at the University of Gothenburg, PO Box 465, Gothenburg, SE-40530, Sweden
| | - Maxim Mayzel
- Swedish NMR Centre at the University of Gothenburg, PO Box 465, Gothenburg, SE-40530, Sweden
| | | | - Lars Backman
- Department of Chemistry, Umeå University, Umeå, SE-901 87, Sweden
| |
Collapse
|
5
|
Distinct brain transcriptome profiles in C9orf72-associated and sporadic ALS. Nat Neurosci 2015; 18:1175-82. [PMID: 26192745 PMCID: PMC4830686 DOI: 10.1038/nn.4065] [Citation(s) in RCA: 275] [Impact Index Per Article: 30.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 06/19/2015] [Indexed: 01/14/2023]
Abstract
Increasing evidence suggests that defective RNA processing contributes to the development of amyotrophic lateral sclerosis (ALS). This may be especially true for ALS caused by a repeat expansion in C9orf72 (c9ALS), in which the accumulation of RNA foci and dipeptide-repeat proteins are expected to modify RNA metabolism. We report extensive alternative splicing (AS) and alternative polyadenylation (APA) defects in the cerebellum of c9ALS cases (8,224 AS, 1,437 APA), including changes in ALS-associated genes (e.g. ATXN2 and FUS), and cases of sporadic ALS (sALS; 2,229 AS, 716 APA). Furthermore, hnRNPH and other RNA-binding proteins are predicted as potential regulators of cassette exon AS events for both c9ALS and sALS. Co-expression and gene-association network analyses of gene expression and AS data revealed divergent pathways associated with c9ALS and sALS.
Collapse
|
6
|
Maccani JZJ, Koestler DC, Lester B, Houseman EA, Armstrong DA, Kelsey KT, Marsit CJ. Placental DNA Methylation Related to Both Infant Toenail Mercury and Adverse Neurobehavioral Outcomes. ENVIRONMENTAL HEALTH PERSPECTIVES 2015; 123:723-9. [PMID: 25748564 PMCID: PMC4492267 DOI: 10.1289/ehp.1408561] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/15/2014] [Accepted: 03/04/2015] [Indexed: 05/19/2023]
Abstract
BACKGROUND Prenatal mercury (Hg) exposure is associated with adverse child neurobehavioral outcomes. Because Hg can interfere with placental functioning and cross the placenta to target the fetal brain, prenatal Hg exposure can inhibit fetal growth and development directly and indirectly. OBJECTIVES We examined potential associations between prenatal Hg exposure assessed through infant toenail Hg, placental DNA methylation changes, and newborn neurobehavioral outcomes. METHODS The methylation status of > 485,000 CpG loci was interrogated in 192 placental samples using Illumina's Infinium HumanMethylation450 BeadArray. Hg concentrations were analyzed in toenail clippings from a subset of 41 infants; neurobehavior was assessed using the NICU Network Neurobehavioral Scales (NNNS) in an independent subset of 151 infants. RESULTS We identified 339 loci with an average methylation difference > 0.125 between any two toenail Hg tertiles. Variation among these loci was subsequently found to be associated with a high-risk neurodevelopmental profile (omnibus p-value = 0.007) characterized by the NNNS. Ten loci had p < 0.01 for the association between methylation and the high-risk NNNS profile. Six of 10 loci reside in the EMID2 gene and were hypomethylated in the 16 high-risk profile infants' placentas. Methylation at these loci was moderately correlated (correlation coefficients range, -0.33 to -0.45) with EMID2 expression. CONCLUSIONS EMID2 hypomethylation may represent a novel mechanism linking in utero Hg exposure and adverse infant neurobehavioral outcomes.
Collapse
Affiliation(s)
- Jennifer Z J Maccani
- Penn State Tobacco Center of Regulatory Science, Department of Public Health Sciences, College of Medicine, Penn State University, Hershey, Pennsylvania, USA
| | | | | | | | | | | | | |
Collapse
|
7
|
Abstract
Due to alternative splicing, the human ACTN1 gene codes for three different transcripts of α-actinin; one isoform that is expressed only in the brain and two with a more general expression pattern. The sequence difference is located to the C-terminal domains and the EF-hand motifs. Therefore, any functional or structural distinction should involve this part of the protein. To investigate this further, the calcium affinities of these three isoforms of α-actinin 1 have been determined by isothermal calorimetry.
Collapse
Affiliation(s)
- Lars Backman
- Department of Chemistry, Umeå University , Umeå , Sweden
| |
Collapse
|
8
|
Abstract
α-Actinins are a major class of actin filament cross-linking proteins expressed in virtually all cells. In muscle, actinins cross-link thin filaments from adjacent sarcomeres. In non-muscle cells, different actinin isoforms play analogous roles in cross-linking actin filaments and anchoring them to structures such as cell-cell and cell-matrix junctions. Although actinins have long been known to play roles in cytokinesis, cell adhesion and cell migration, recent studies have provided further mechanistic insights into these functions. Roles for actinins in synaptic plasticity and membrane trafficking events have emerged more recently, as has a 'non-canonical' function for actinins in transcriptional regulation in the nucleus. In the present paper we review recent advances in our understanding of these diverse cell biological functions of actinins in non-muscle cells, as well as their roles in cancer and in genetic disorders affecting platelet and kidney physiology. We also make two proposals with regard to the actinin nomenclature. First, we argue that naming actinin isoforms according to their expression patterns is problematic and we suggest a more precise nomenclature system. Secondly, we suggest that the α in α-actinin is superfluous and can be omitted.
Collapse
|
9
|
Oehl-Jaschkowitz B, Vanakker OM, De Paepe A, Menten B, Martin T, Weber G, Christmann A, Krier R, Scheid S, McNerlan SE, McKee S, Tzschach A. Deletions in 14q24.1q24.3 are associated with congenital heart defects, brachydactyly, and mild intellectual disability. Am J Med Genet A 2013; 164A:620-6. [PMID: 24357125 DOI: 10.1002/ajmg.a.36321] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 09/14/2013] [Indexed: 01/01/2023]
Abstract
Interstitial deletions of chromosome band 14q24.1q24.3 are apparently very rare. We report on three unrelated patients with overlapping de novo deletions of sizes 5.4, 2.8, and 2.3 Mb in this region. While some clinical problems such as intestinal malrotation, cryptorchidism, and ectopic kidney were only observed in single patients, all three patients had mild intellectual disability, congenital heart defects (truncus arteriosus, pulmonary atresia, atrial septal defect, and/or ventricular septal defect), brachydactyly, hypertelorism, broad nasal bridge, and thin upper lips. Likely haploinsufficiency of one or several of the 19 genes in the common deleted interval (ACTN1, DCAF5, EXD2, GALNTL1, ERH, SLC39A9, PLEKHD1, CCDC177, KIAA0247, LOC100289511, SRSF5, SLC10A1, SMOC1, SLC8A3, ADAM21P1, COX16, SYNJ2BP, SYNJ2BP-COX16, ADAM21) was responsible for these manifestations, but apart from SMOC1, mutations in which cause autosomal recessive Waardenburg anophthalmia syndrome, and ACTN1, mutations in which are associated with congenital macrothrombocytopenia, no disease associations have so far been reported for the other genes. Functional studies and a systematic search for mutations or chromosome aberrations in this region will elucidate the role of individual genes in the clinical manifestations and will provide insight into the underlying biological mechanisms.
Collapse
|
10
|
An analysis of splicing, actin-binding properties, heterodimerization and molecular interactions of the non-muscle α-actinins. Biochem J 2013; 452:477-88. [PMID: 23557398 DOI: 10.1042/bj20121824] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The non-muscle α-actinin isoforms (actinin-1 and -4) are closely related dimeric actin filament cross-linking proteins. Despite high sequence similarity, unique properties have been ascribed to actinin-4 in particular. For example, actinin-4, but not actinin-1, is essential for normal glomerular function in the kidney, is overexpressed in several cancers and can translocate to the nucleus to regulate transcription. To understand the molecular basis for such isoform-specific functions we have, for the first time, comprehensively compared these proteins in terms of alternative splicing, actin-binding properties, heterodimer formation and molecular interactions. We find that the Ca2+-insensitive variant of actinin-4 is expressed only in the nervous system and thus cannot be regarded as a smooth muscle isoform, as is the case for the Ca2+-insensitive variant of actinin-1. The actin-binding properties of actinin-1 and -4 are similar and are unlikely to explain isoform-specific functions. Surprisingly, we reveal that actinin-1/-4 heterodimers, rather than homodimers, are the most abundant form of actinin in many cell lines. Finally, we use a proteomics approach to identify potential isoform-specific interactions. The results of the present study indicate that actinin-1 and -4 can readily form heterodimers composed of monomers that may have different properties and interacting proteins. This significantly alters our view of non-muscle actinin function.
Collapse
|
11
|
Calaway JD, Domínguez JI, Hanson ME, Cambranis EC, Pardo-Manuel de Villena F, de la Casa-Esperon E. Intronic parent-of-origin dependent differential methylation at the Actn1 gene is conserved in rodents but is not associated with imprinted expression. PLoS One 2012; 7:e48936. [PMID: 23145029 PMCID: PMC3493592 DOI: 10.1371/journal.pone.0048936] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2012] [Accepted: 10/01/2012] [Indexed: 12/20/2022] Open
Abstract
Parent-of-origin differential DNA methylation has been associated with regulation of the preferential expression of paternal or maternal alleles of imprinted genes. Based on this association, recent studies have searched for parent-of-origin dependent differentially methylated regions in order to identify new imprinted genes in their vicinity. In a previous genome-wide analysis of mouse brain DNA methylation, we found a novel differentially methylated region in a CpG island located in the last intron of the alpha 1 Actinin (Actn1) gene. In this region, preferential methylation of the maternal allele was observed; however, there were no reports of imprinted expression of Actn1. Therefore, we have tested if differential methylation of this region is common to other tissues and species and affects the expression of Actn1. We have found that Actn1 differential methylation occurs in diverse mouse tissues. Moreover, it is also present in other murine rodents (rat), but not in the orthologous human region. In contrast, we have found no indication of an imprinted effect on gene expression of Actn1 in mice: expression is always biallelic regardless of sex, tissue type, developmental stage or isoform. Therefore, we have identified a novel parent-of-origin dependent differentially methylated region that has no apparent association with imprinted expression of the closest genes. Our findings sound a cautionary note to genome-wide searches on the use of differentially methylated regions for the identification of imprinted genes and suggest that parent-of-origin dependent differential methylation might be conserved for functions other that the control of imprinted expression.
Collapse
Affiliation(s)
- John D Calaway
- Curriculum in Genetics and Molecular Biology, Department of Genetics, Lineberger Comprehensive Cancer Center and Carolina Center for Genome Sciences of the University of North Carolina (UNC), Chapel Hill, NC, USA
| | | | | | | | | | | |
Collapse
|
12
|
Licatalosi DD, Yano M, Fak JJ, Mele A, Grabinski SE, Zhang C, Darnell RB. Ptbp2 represses adult-specific splicing to regulate the generation of neuronal precursors in the embryonic brain. Genes Dev 2012; 26:1626-42. [PMID: 22802532 DOI: 10.1101/gad.191338.112] [Citation(s) in RCA: 149] [Impact Index Per Article: 12.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/28/2022]
Abstract
Two polypyrimidine tract RNA-binding proteins (PTBs), one near-ubiquitously expressed (Ptbp1) and another highly tissue-restricted (Ptbp2), regulate RNA in interrelated but incompletely understood ways. Ptbp1, a splicing regulator, is replaced in the brain and differentiated neuronal cell lines by Ptbp2. To define the roles of Ptbp2 in the nervous system, we generated two independent Ptbp2-null strains, unexpectedly revealing that Ptbp2 is expressed in neuronal progenitors and is essential for postnatal survival. A HITS-CLIP (high-throughput sequencing cross-linking immunoprecipitation)-generated map of reproducible Ptbp2-RNA interactions in the developing mouse neocortex, combined with results from splicing-sensitive microarrays, demonstrated that the major action of Ptbp2 is to inhibit adult-specific alternative exons by binding pyrimidine-rich sequences upstream of and/or within them. These regulated exons are present in mRNAs encoding proteins associated with control of cell fate, proliferation, and the actin cytoskeleton, suggesting a role for Ptbp2 in neurogenesis. Indeed, neuronal progenitors in the Ptbp2-null brain exhibited an aberrant polarity and were associated with regions of premature neurogenesis and reduced progenitor pools. Thus, Ptbp2 inhibition of a discrete set of adult neuronal exons underlies early brain development prior to neuronal differentiation and is essential for postnatal survival.
Collapse
Affiliation(s)
- Donny D Licatalosi
- Laboratory of Molecular Neuro-Oncology, The Rockefeller University, New York, New York 10065, USA
| | | | | | | | | | | | | |
Collapse
|
13
|
Collin GB, Marshall JD, King BL, Milan G, Maffei P, Jagger DJ, Naggert JK. The Alström syndrome protein, ALMS1, interacts with α-actinin and components of the endosome recycling pathway. PLoS One 2012; 7:e37925. [PMID: 22693585 PMCID: PMC3365098 DOI: 10.1371/journal.pone.0037925] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2011] [Accepted: 04/30/2012] [Indexed: 01/26/2023] Open
Abstract
Alström syndrome (ALMS) is a progressive multi-systemic disorder characterized by cone-rod dystrophy, sensorineural hearing loss, childhood obesity, insulin resistance and cardiac, renal, and hepatic dysfunction. The gene responsible for Alström syndrome, ALMS1, is ubiquitously expressed and has multiple splice variants. The protein encoded by this gene has been implicated in ciliary function, cell cycle control, and intracellular transport. To gain better insight into the pathways through which ALMS1 functions, we carried out a yeast two hybrid (Y2H) screen in several mouse tissue libraries to identify ALMS1 interacting partners. The majority of proteins found to interact with the murine carboxy-terminal end (19/32) of ALMS1 were α-actinin isoforms. Interestingly, several of the identified ALMS1 interacting partners (α-actinin 1, α-actinin 4, myosin Vb, rad50 interacting 1 and huntingtin associated protein1A) have been previously associated with endosome recycling and/or centrosome function. We examined dermal fibroblasts from human subjects bearing a disruption in ALMS1 for defects in the endocytic pathway. Fibroblasts from these patients had a lower uptake of transferrin and reduced clearance of transferrin compared to controls. Antibodies directed against ALMS1 N- and C-terminal epitopes label centrosomes and endosomal structures at the cleavage furrow of dividing MDCK cells, respectively, suggesting isoform-specific cellular functions. Our results suggest a role for ALMS1 variants in the recycling endosome pathway and give us new insights into the pathogenesis of a subset of clinical phenotypes associated with ALMS.
Collapse
Affiliation(s)
- Gayle B. Collin
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Jan D. Marshall
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
| | - Benjamin L. King
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
- Mount Desert Island Biological Laboratory, Salisbury Cove, Maine, United States of America
| | - Gabriella Milan
- Department of Medical and Surgical Sciences, University of Padua, Padua, Italy
| | - Pietro Maffei
- Department of Medical and Surgical Sciences, University of Padua, Padua, Italy
| | - Daniel J. Jagger
- UCL Ear Institute, University College London, London, United Kingdom
| | - Jürgen K. Naggert
- The Jackson Laboratory, Bar Harbor, Maine, United States of America
- * E-mail:
| |
Collapse
|
14
|
Gupta V, Discenza M, Guyon JR, Kunkel LM, Beggs AH. α-Actinin-2 deficiency results in sarcomeric defects in zebrafish that cannot be rescued by α-actinin-3 revealing functional differences between sarcomeric isoforms. FASEB J 2012; 26:1892-908. [PMID: 22253474 DOI: 10.1096/fj.11-194548] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
α-Actinins are actin-binding proteins that can be broadly divided into Ca(2+)-sensitive cytoskeletal and Ca(2+)-insensitive sarcomeric isoforms. To date, little is known about functional differences between the isoforms due to their indistinguishable activities in most in vitro assays. To identify functional differences in vivo between sarcomeric isoforms, we employed computational and molecular approaches to characterize the zebrafish (Danio rerio) genome, which contains orthologoues of each human α-actinin gene, including duplicated copies of actn3. Each isoform exhibits a distinct and unique pattern of gene expression as assessed by mRNA in situ hybridization, largely sharing similar expression profiles as seen in humans. The spatial conservation of expression of these genes from lower invertebrates to humans suggests that regulation and subsequent functions of these genes are conserved during evolution. Morpholino-based knockdown of the sarcomeric isoform, actn2, leads to skeletal muscle, cardiac, and ocular defects evident over the first week of development. Remarkably, despite the high degree of sequence conservation between actn2 and actn3, the phenotypes of α-actinin-2 deficient zebrafish can be rescued by overexpression of α-actinin-2 but not by α-actinin-3 mRNAs from zebrafish or human. These data provide functional evidence that the primary sequences of α-actinin-2 and α-actinin-3 evolved differences to optimize their functions.
Collapse
Affiliation(s)
- Vandana Gupta
- Division of Genetics, Children's Hospital Boston, 300 Longwood Ave., Boston, MA 02115, USA
| | | | | | | | | |
Collapse
|
15
|
Bush WS, McCauley JL, DeJager PL, Dudek SM, Hafler DA, Gibson RA, Matthews PM, Kappos L, Naegelin Y, Polman CH, Hauser SL, Oksenberg J, Haines JL, Ritchie MD. A knowledge-driven interaction analysis reveals potential neurodegenerative mechanism of multiple sclerosis susceptibility. Genes Immun 2011; 12:335-40. [PMID: 21346779 PMCID: PMC3136581 DOI: 10.1038/gene.2011.3] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2010] [Revised: 11/03/2010] [Accepted: 11/11/2010] [Indexed: 02/05/2023]
Abstract
Gene-gene interactions are proposed as an important component of the genetic architecture of complex diseases, and are just beginning to be evaluated in the context of genome-wide association studies (GWAS). In addition to detecting epistasis, a benefit to interaction analysis is that it also increases power to detect weak main effects. We conducted a knowledge-driven interaction analysis of a GWAS of 931 multiple sclerosis (MS) trios to discover gene-gene interactions within established biological contexts. We identify heterogeneous signals, including a gene-gene interaction between CHRM3 (muscarinic cholinergic receptor 3) and MYLK (myosin light-chain kinase) (joint P=0.0002), an interaction between two phospholipase C-β isoforms, PLCβ1 and PLCβ4 (joint P=0.0098), and a modest interaction between ACTN1 (actinin alpha 1) and MYH9 (myosin heavy chain 9) (joint P=0.0326), all localized to calcium-signaled cytoskeletal regulation. Furthermore, we discover a main effect (joint P=5.2E-5) previously unidentified by single-locus analysis within another related gene, SCIN (scinderin), a calcium-binding cytoskeleton regulatory protein. This work illustrates that knowledge-driven interaction analysis of GWAS data is a feasible approach to identify new genetic effects. The results of this study are among the first gene-gene interactions and non-immune susceptibility loci for MS. Further, the implicated genes cluster within inter-related biological mechanisms that suggest a neurodegenerative component to MS.
Collapse
Affiliation(s)
- William S. Bush
- Center for Human Genetics Research, Dept of Molecular Physiology and Biophysics, Vanderbilt University, 519 Light Hall, Nashville, TN 37232
| | - Jacob L. McCauley
- Miami Institute for Human Genomics, University of Miami, Miller School of Medicine, 1501 NW 10 Ave, Miami, FL 33136
| | - Philip L. DeJager
- Division of Molecular Immunology, Center for Neurologic Diseases, Dept of Neurology, Brigham & Women’s Hospital and Harvard Medical School, 77 Ave Louis Pasteur, Boston, MA 02115
| | - Scott M. Dudek
- Center for Human Genetics Research, Dept of Molecular Physiology and Biophysics, Vanderbilt University, 519 Light Hall, Nashville, TN 37232
| | - David A. Hafler
- Division of Molecular Immunology, Center for Neurologic Diseases, Dept of Neurology, Brigham & Women’s Hospital and Harvard Medical School, 77 Ave Louis Pasteur, Boston, MA 02115
| | - Rachel A. Gibson
- GlaxoSmithKline, Research & Development, 980 Great West Rd., Brentford, Middlesex, UK TW8 9GS
| | - Paul M. Matthews
- GlaxoSmithKline, Research & Development, 980 Great West Rd., Brentford, Middlesex, UK TW8 9GS
| | - Ludwig Kappos
- Dept of Neurology, University Hospital Basel, Spitalstrasse21/Petersgraben 4, 4031 Basel, Switzerland
| | - Yvonne Naegelin
- Dept of Neurology, University Hospital Basel, Spitalstrasse21/Petersgraben 4, 4031 Basel, Switzerland
| | - Chris H. Polman
- Dept of Neurology, Vrije Universiteit Medical Centre, De Boelelaan 1105, 1081 HV Amsterdam, The Netherlands
| | | | - Stephen L. Hauser
- Dept of Neurology, School of Medicine, University of California, San Francisco, M798, Box 0114, San Francisco, CA 34143
| | - Jorge Oksenberg
- Dept of Neurology, School of Medicine, University of California, San Francisco, M798, Box 0114, San Francisco, CA 34143
| | - Jonathan L. Haines
- Center for Human Genetics Research, Dept of Molecular Physiology and Biophysics, Vanderbilt University, 519 Light Hall, Nashville, TN 37232
| | - Marylyn D. Ritchie
- Center for Human Genetics Research, Dept of Molecular Physiology and Biophysics, Vanderbilt University, 519 Light Hall, Nashville, TN 37232
| |
Collapse
|
16
|
Retinoic acid treatment and cell aggregation independently regulate alternative splicing in P19 cells during neural differentiation. Cell Biol Int 2010; 34:631-43. [PMID: 20230377 DOI: 10.1042/cbi20090332] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
To induce neural differentiation of P19 cells, two different treatments, RA (retinoic acid) and cell aggregation, are required. However, there has been no report that RA treatment alone or cell aggregation alone could control alternative splicing regulation in P19 cells. Therefore, we focused on alternative splicing effects by neural induction (RA treatment and/or cell aggregation) in P19 cells. We analysed the splicing patterns of several genes, including 5-HT3R-A (5-hydroxytryptamine receptor), Actn1 (actinin alpha1), CUGBP2 (CUG-binding protein) and PTB (polypyrimidine track-binding protein), which showed different responses during the early neural induction of P19 cells. We show here that RA treatment alone changes the alternative splice mechanism of 5-HT3R-A. Cell aggregation alone controls alternative splicing regulation of Actn1. Both treatments (RA and cell aggregation) compensate and regulate the alternative splicing mechanism of CUGBP2. However, PTB is independent of RA and cell aggregation. Taken together, our results suggest that RA treatment and cell aggregation independently regulate the alternative splicing mechanism in the early stage of P19 cells during neural differentiation.
Collapse
|
17
|
Matlin AJ, Southby J, Gooding C, Smith CWJ. Repression of alpha-actinin SM exon splicing by assisted binding of PTB to the polypyrimidine tract. RNA (NEW YORK, N.Y.) 2007; 13:1214-23. [PMID: 17592047 PMCID: PMC1924891 DOI: 10.1261/rna.219607] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/12/2006] [Accepted: 05/17/2007] [Indexed: 05/08/2023]
Abstract
Polypyrimidine tract binding protein (PTB) acts as a regulatory repressor of a large number of alternatively spliced exons, often requiring multiple binding sites in order to repress splicing. In one case, cooperative binding of PTB has been shown to accompany repression. The SM exon of the alpha-actinin pre-mRNA is also repressed by PTB, leading to inclusion of the alternative upstream NM exon. The SM exon has a distant branch point located 386 nt upstream of the exon with an adjacent 26 nucleotide pyrimidine tract. Here we have analyzed PTB binding to the NM and SM exon region of the alpha-actinin pre-mRNA. We find that three regions of the intron bind PTB, including the 3' end of the polypyrimidine tract (PPT) and two additional regions between the PPT and the SM exon. The downstream PTB binding sites are essential for full repression and promote binding of PTB to the PPT with a consequent reduction in U2AF(65) binding. Our results are consistent with a repressive mechanism in which cooperative binding of PTB to the PPT competes with binding of U2AF(65), thereby specifically blocking splicing of the SM exon.
Collapse
|
18
|
Cabello N, Remelli R, Canela L, Soriguera A, Mallol J, Canela EI, Robbins MJ, Lluis C, Franco R, McIlhinney RAJ, Ciruela F. Actin-binding protein alpha-actinin-1 interacts with the metabotropic glutamate receptor type 5b and modulates the cell surface expression and function of the receptor. J Biol Chem 2007; 282:12143-53. [PMID: 17311919 DOI: 10.1074/jbc.m608880200] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Receptors for neurotransmitters require scaffolding proteins for membrane microdomain targeting and for regulating receptor function. Using a yeast two-hybrid screen, alpha-actinin-1, a major F-actin cross-linking protein, was identified as a binding partner for the C-terminal domain of metabotropic glutamate receptor type 5b (mGlu(5b) receptor). Co-expression, co-immunoprecipitation, and pull-down experiments showed a close and specific interaction between mGlu(5b) receptor and alpha-actinin-1 in both transfected HEK-293 cells and rat striatum. The interaction of alpha-actinin-1 with mGlu(5b) receptor modulated the cell surface expression of the receptor. This was dependent on the binding of alpha-actinin-1 to the actin cytoskeleton. In addition, the alpha-actinin-1/mGlu(5b) receptor interaction regulated receptor-mediated activation of the mitogen-activated protein kinase pathway. Together, these findings indicate that there is an alpha-actinin-1-dependent mGlu(5b) receptor association with the actin cytoskeleton modulating receptor cell surface expression and functioning.
Collapse
Affiliation(s)
- Nuria Cabello
- Institut d'Investigacions Biomèdiques August Pi i Sunyer and Department of Biochemistry and Molecular Biology, University of Barcelona, Facultat de Biologia, Avda. Diagonal 645, Barcelona 08028, Spain
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
19
|
Sakagami H, Honma T, Sukegawa J, Owada Y, Yanagisawa T, Kondo H. Somatodendritic localization of EFA6A, a guanine nucleotide exchange factor for ADP-ribosylation factor 6, and its possible interaction with α-actinin in dendritic spines. Eur J Neurosci 2007; 25:618-28. [PMID: 17298598 DOI: 10.1111/j.1460-9568.2007.05345.x] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
EFA6A is a member of the guanine nucleotide exchange factors that can specifically activate ADP ribosylation factor 6 (ARF6). In this study, we identified alpha-actinin-1 as a possible interacting protein with EFA6A by the yeast two-hybrid screening with its C-terminal region as bait. The central region of alpha-actinin-1 containing a part of spectrin repeat 1 and spectrin repeats 2-3 is responsible for this interaction. In the hippocampal formation, EFA6A immunoreactivity occurred at a high level as numerous fine puncta in the strata oriens, radiatum, lacunosum-moleculare of the hippocampal CA1-3 subfields and the dentate molecular layer, whereas the immunoreactivity was faint in the neuronal cell layers and the stratum lucidum, the mossy fiber-recipient layer of the CA3 subfield. Double-immunofluorescent analyses revealed a partial overlapping of EFA6A and alpha-actinin at the dendritic spines of in vivo and cultured hippocampal neurons. Our present findings suggest that EFA6A may form a protein complex with alpha-actinin and activate ARF6 in close proximity of the actin cytoskeleton and membrane proteins in the dendritic spines.
Collapse
Affiliation(s)
- Hiroyuki Sakagami
- Division of Histology, Department of Cell Biology, Tohoku University Graduate School of Medicine, 2-1 Seiryo-machi, Sendai 980-8575, Japan.
| | | | | | | | | | | |
Collapse
|
20
|
Nuriya M, Oh S, Huganir RL. Phosphorylation-dependent interactions of α-Actinin-1/IQGAP1 with the AMPA receptor subunit GluR4. J Neurochem 2005; 95:544-52. [PMID: 16190873 DOI: 10.1111/j.1471-4159.2005.03410.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
AMPA (alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid) receptors play key roles in excitatory synaptic transmission and synaptic plasticity in the CNS. Although a variety of proteins has been characterized to interact with AMPA receptors and regulate their function, little is known about the regulation of the AMPA receptor subunit GluR4. To understand the molecular mechanisms of GluR4 functional regulation, the yeast two-hybrid system was used to identify GluR4-interacting molecules. alpha-Actinin-1 and IQGAP1 were identified to be GluR4-specific binding partners. Both proteins interact specifically with GluR4 and co-cluster with GluR4 individually in neurons. Mapping experiments revealed that alpha-Actinin-1 and IQGAP1 bind to the same region within the C-terminus of GluR4 that contains a previously identified PKA phosphorylation site, Ser842, phosphorylation of which is regulated by synaptic activity. Interestingly, the phosphorylation of Ser842 differentially regulates interactions of GluR4 with alpha-Actinin-1 and IQGAP1; phosphorylation strongly inhibits interaction of GluR4 with alpha-Actinin-1 but has little effect on its interaction with IQGAP1. These results suggest that alpha-Actinin-1 and IQGAP1 regulate GluR4 functions via their specific associations with GluR4. In addition, our data indicate that activity-dependent phosphorylation of GluR4 may regulate its synaptic targeting through phosphorylation-dependent interactions with alpha-Actinin-1 and IQGAP1.
Collapse
Affiliation(s)
- Mutsuo Nuriya
- Department of Neuroscience, Howard Hughes Medical Institute, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA
| | | | | |
Collapse
|
21
|
Okumura M, Kondo S, Ogata M, Kanemoto S, Murakami T, Yanagida K, Saito A, Imaizumi K. Candidates for tumor-specific alternative splicing. Biochem Biophys Res Commun 2005; 334:23-9. [PMID: 16018876 DOI: 10.1016/j.bbrc.2005.06.057] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2005] [Accepted: 06/09/2005] [Indexed: 11/23/2022]
Abstract
Gene expression can be regulated not only by transcription and post-transcriptional modifications, but also by splicing regulation. Recent genome-wide analyses have indicated that up to 70% of human genes may have alternatively spliced forms, suggesting that splicing regulation affects a wide range of gene expression. Tumor tissues show significantly altered protein expressions, and this is also thought to be affected by alternative splicing. Although some alternative splicing events have been reported to be cancer specific and others have been predicted from database analyses, the process of alternative splicing and its regulatory machinery are hardly understood. We searched for and detected alternative splicing events that alter protein splicing in all or a subset of tumor tissues. The results revealed tissue-specific alterations of splicing regulation by tumorigenesis, and regulatory cis-element analyses further suggested that multiple splicing regulatory machineries were affected by this process.
Collapse
Affiliation(s)
- Masayo Okumura
- Division of Structural Cellular Biology, The Graduate School of Biological Sciences, Nara Institute of Science and Technology (NAIST), 8916-5 Takayama, Ikoma, Nara 630-0101, Japan.
| | | | | | | | | | | | | | | |
Collapse
|
22
|
Zhang J, Mruk DD, Cheng CY. Myotubularin phosphoinositide phosphatases, protein phosphatases, and kinases: their roles in junction dynamics and spermatogenesis. J Cell Physiol 2005; 204:470-83. [PMID: 15690393 DOI: 10.1002/jcp.20303] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Spermatogenesis in the seminiferous epithelium of the mammalian testis is a dynamic cellular event. It involves extensive restructuring at the Sertoli-germ cell interface, permitting germ cells to traverse the epithelium from basal to adluminal compartment. As such, Sertoli-germ cell actin-based adherens junctions (AJ), such as ectoplasmic specializations (ES), must disassemble and reassemble to facilitate this event. Recent studies have shown that AJ dynamics are regulated by intricate interactions between AJ integral membrane proteins (e.g., cadherins, alpha6beta1 integrins and nectins), phosphatases, kinases, adaptors, and the underlying cytoskeleton network. For instance, the myotubularin (MTM) phosphoinositide (PI) phosphatases, such as MTM related protein 2 (MTMR2), can form a functional complex with c-Src (a non-receptor protein tyrosine kinase). In turn, this phosphatase/kinase complex associates with beta-catenin, a constituent of the N-cadherin/beta-catenin functional unit at the AJ site. This MTMR2-c-Src-beta-catenin complex apparently regulates the phosphorylation status of beta-catenin, which determines cell adhesive function conferred by the cadherin-catenin protein complex in the seminiferous epithelium. In this review, we discuss the current status of research on selected phosphatases and kinases, and how these proteins potentially interact with adaptors at AJ in the seminiferous epithelium to regulate cell adhesion in the testis. Specific research areas that are open for further investigation are also highlighted.
Collapse
Affiliation(s)
- Jiayi Zhang
- Population Council, Center for Biomedical Research, New York, New York, USA
| | | | | |
Collapse
|
23
|
Spellman R, Rideau A, Matlin A, Gooding C, Robinson F, McGlincy N, Grellscheid SN, Southby J, Wollerton M, Smith CWJ. Regulation of alternative splicing by PTB and associated factors. Biochem Soc Trans 2005; 33:457-60. [PMID: 15916540 DOI: 10.1042/bst0330457] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
PTB (polypyrimidine tract-binding protein) is a repressive regulator of alternative splicing. We have investigated the role of PTB in three model alternative splicing systems. In the alpha-actinin gene, PTB represses the SM (smooth muscle) exon by binding to key sites in the polypyrimidine tract. Repressive binding to these sites is assisted by co-operative binding to additional downstream sites. SM exon splicing can be activated by CELF proteins, which also bind co-operatively to interspersed sites and displace PTB from the pyrimidine tract. Exon 11 of PTB pre-mRNA is repressed by PTB in an autoregulatory feedback loop. Exon 11-skipped RNA gets degraded through nonsense-mediated decay. Less than 1% of steady-state PTB mRNA is represented by this isoform, but inhibition of nonsense-mediated decay by RNA interference against Upf1 shows that at least 20% of PTB RNA is consumed by this pathway. This represents a widespread but under-appreciated role of alternative splicing in the quantitative regulation of gene expression, an important addition to its role as a generator of protein isoform diversity. Repression of alpha-tropomyosin exon 3 is an exceptional example of PTB regulation, because repression only occurs at high levels in SM cells, despite the fact that PTB is widely expressed. In this case, a PTB-interacting cofactor, raver1, appears to play an important role. By the use of 'tethering' assays, we have identified discrete domains within both PTB and raver1 that mediate their repressive activities on this splicing event.
Collapse
Affiliation(s)
- R Spellman
- Department of Biochemistry, University of Cambridge, 80, Tennis Court Road, Cambridge CB2 1GA, UK
| | | | | | | | | | | | | | | | | | | |
Collapse
|
24
|
Kremerskothen J, Plaas C, Kindler S, Frotscher M, Barnekow A. Synaptopodin, a molecule involved in the formation of the dendritic spine apparatus, is a dual actin/alpha-actinin binding protein. J Neurochem 2005; 92:597-606. [PMID: 15659229 DOI: 10.1111/j.1471-4159.2004.02888.x] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Synaptopodin (SYNPO) is a cytoskeletal protein that is preferentially located in mature dendritic spines, where it accumulates in the spine neck and closely associates with the spine apparatus. Formation of the spine apparatus critically depends on SYNPO. To further determine its molecular action, we screened for cellular binding partners. Using the yeast two-hybrid system and biochemical assays, SYNPO was found to associate with both F-actin and alpha-actinin. Ectopic expression of SYNPO in neuronal and non-neuronal cells induced actin aggregates, thus confirming a cytoplasmic interaction with the actin cytoskeleton. Whereas F-actin association is mediated by a central SYNPO motif, binding to alpha-actinin requires the C-terminal domain. Notably, the alpha-actinin binding domain is also essential for dendritic targeting and postsynaptic accumulation of SYNPO in primary neurons. Taken together, our data suggest that dendritic spine accumulation of SYNPO critically depends on its interaction with postsynaptic alpha-actinin and that SYNPO may regulate spine morphology, motility and function via its distinct modes of association with the actin cytoskeleton.
Collapse
Affiliation(s)
- Joachim Kremerskothen
- Department for Experimental Tumorbiology, University of Muenster, Badestrasse 9, D-48149 Muenster, Germany.
| | | | | | | | | |
Collapse
|
25
|
Abstract
The alpha-actinins are an ancient family of actin-binding proteins that play structural and regulatory roles in cytoskeletal organisation and muscle contraction. alpha-actinin-3 is the most-highly specialised of the four mammalian alpha-actinins, with its expression restricted largely to fast glycolytic fibres in skeletal muscle. Intriguingly, a significant proportion ( approximately 18%) of the human population is totally deficient in alpha-actinin-3 due to homozygosity for a premature stop codon polymorphism (R577X) in the ACTN3 gene. Recent work in our laboratory has revealed a strong association between R577X genotype and performance in a variety of athletic endeavours. We are currently exploring the function and evolutionary history of the ACTN3 gene and other alpha-actinin family members. The alpha-actinin family provides a fascinating case study in molecular evolution, illustrating phenomena such as functional redundancy in duplicate genes, the evolution of protein function, and the action of natural selection during recent human evolution.
Collapse
|
26
|
Gromak N, Matlin AJ, Cooper TA, Smith CWJ. Antagonistic regulation of alpha-actinin alternative splicing by CELF proteins and polypyrimidine tract binding protein. RNA (NEW YORK, N.Y.) 2003; 9:443-56. [PMID: 12649496 PMCID: PMC1370411 DOI: 10.1261/rna.2191903] [Citation(s) in RCA: 81] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2002] [Accepted: 01/14/2003] [Indexed: 05/21/2023]
Abstract
The alpha-actinin gene has a pair of alternatively spliced exons. The smooth muscle (SM) exon is repressed in most cell types by polypyrimidine tract binding protein (PTB). CELF (CUG-BP and ETR3-like factors) family proteins, splicing regulators whose activities are altered in myotonic dystrophy, were found to coordinately regulate selection of the two alpha-actinin exons. CUG-BP and ETR3 activated the SM exon, and along with CELF4 they were also able to repress splicing of the NM (nonmuscle) exon both in vivo and in vitro. Activation of SM exon splicing was associated with displacement of PTB from the polypyrimidine tract by binding of CUG-BP at adjacent sites. Our data provides direct evidence for the activity of CELF proteins as both activators and repressors of splicing within a single-model system of alternative splicing, and suggests a model whereby alpha-actinin alternative splicing is regulated by synergistic and antagonistic interactions between members of the CELF and PTB families.
Collapse
Affiliation(s)
- Natalia Gromak
- Department of Biochemistry, University of Cambridge, Cambridge CB2 1GA, UK
| | | | | | | |
Collapse
|