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Bircher JE, Corcoran EE, Lam TT, Trnka MJ, Koleske AJ. Autoinhibition of the GEF activity of cytoskeletal regulatory protein Trio is disrupted in neurodevelopmental disorder-related genetic variants. J Biol Chem 2022; 298:102361. [PMID: 35963430 PMCID: PMC9467883 DOI: 10.1016/j.jbc.2022.102361] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Revised: 08/04/2022] [Accepted: 08/05/2022] [Indexed: 11/29/2022] Open
Abstract
TRIO encodes a cytoskeletal regulatory protein with three catalytic domains-two guanine exchange factor (GEF) domains, GEF1 and GEF2, and a kinase domain-as well as several accessory domains that have not been extensively studied. Function-damaging variants in the TRIO gene are known to be enriched in individuals with neurodevelopmental disorders (NDDs). Disease variants in the GEF1 domain or the nine adjacent spectrin repeats (SRs) are enriched in NDDs, suggesting that dysregulated GEF1 activity is linked to these disorders. We provide evidence here that the Trio SRs interact intramolecularly with the GEF1 domain to inhibit its enzymatic activity. We demonstrate that SRs 6-9 decrease GEF1 catalytic activity both in vitro and in cells and show that NDD-associated variants in the SR8 and GEF1 domains relieve this autoinhibitory constraint. Our results from chemical cross-linking and bio-layer interferometry indicate that the SRs primarily contact the pleckstrin homology region of the GEF1 domain, reducing GEF1 binding to the small GTPase Rac1. Together, our findings reveal a key regulatory mechanism that is commonly disrupted in multiple NDDs and may offer a new target for therapeutic intervention for TRIO-associated NDDs.
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Affiliation(s)
- Josie E. Bircher
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - Ellen E. Corcoran
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA
| | - TuKiet T. Lam
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA,Keck MS & Proteomics Resource, Yale University, New Haven, Connecticut, USA
| | - Michael J. Trnka
- Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California, USA
| | - Anthony J. Koleske
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut, USA,Department of Neuroscience, Yale University, New Haven, Connecticut, USA,For correspondence: Anthony J. Koleske
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2
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Miller MB, Yan Y, Machida K, Kiraly DD, Levy AD, Wu YI, Lam TT, Abbott T, Koleske AJ, Eipper BA, Mains RE. Brain Region and Isoform-Specific Phosphorylation Alters Kalirin SH2 Domain Interaction Sites and Calpain Sensitivity. ACS Chem Neurosci 2017; 8:1554-1569. [PMID: 28418645 DOI: 10.1021/acschemneuro.7b00076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
Kalirin7 (Kal7), a postsynaptic Rho GDP/GTP exchange factor (RhoGEF), plays a crucial role in long-term potentiation and in the effects of cocaine on behavior and spine morphology. The KALRN gene has been linked to schizophrenia and other disorders of synaptic function. Mass spectrometry was used to quantify phosphorylation at 26 sites in Kal7 from individual adult rat nucleus accumbens and prefrontal cortex before and after exposure to acute or chronic cocaine. Region- and isoform-specific phosphorylation was observed along with region-specific effects of cocaine on Kal7 phosphorylation. Evaluation of the functional significance of multisite phosphorylation in a complex protein like Kalirin is difficult. With the identification of five tyrosine phosphorylation (pY) sites, a panel of 71 SH2 domains was screened, identifying subsets that interacted with multiple pY sites in Kal7. In addition to this type of reversible interaction, endoproteolytic cleavage by calpain plays an essential role in long-term potentiation. Calpain cleaved Kal7 at two sites, separating the N-terminal domain, which affects spine length, and the PDZ binding motif from the GEF domain. Mutations preventing phosphorylation did not affect calpain sensitivity or GEF activity; phosphomimetic mutations at specific sites altered protein stability, increased calpain sensitivity, and reduced GEF activity.
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Affiliation(s)
| | | | | | - Drew D. Kiraly
- Department
of Psychiatry, Icahn School of Medicine at Mount Sinai, New York, New York 10029, United States
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3
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Sarangdhar MA, Chaubey D, Bhatt A, Km M, Kumar M, Ranjan S, Pillai B. A Novel Long Non-coding RNA, durga Modulates Dendrite Density and Expression of kalirin in Zebrafish. Front Mol Neurosci 2017; 10:95. [PMID: 28442991 PMCID: PMC5385350 DOI: 10.3389/fnmol.2017.00095] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2016] [Accepted: 03/21/2017] [Indexed: 01/06/2023] Open
Abstract
Kalirin, a key player in axonal development, nerve growth and synaptic re-modeling, is implicated in many pathological conditions like schizophrenia and autism-spectrum disorders. Alternative promoters and splicing lead to functionally distinct isoforms, but the post-transcriptional regulation of Kalirin has not been studied. Here, we report a novel non-coding RNA, which we name durga, arising from the first exon of kalirin a (kalrna) in the antisense orientation in zebrafish. The kalrna and durga transcripts are barely detectable during early development, but steadily increase by 24 hours post-fertilization (hpf) as the brain develops. Over-expression of durga in the zebrafish embryo led to an increase in kalrna expression. The morphology of the neurons cultured from durga injected embryos had significantly fewer and shorter dendrites. Although durga has no apparent sequence homolog in mammals, based on gene synteny, we found a non-coding RNA arising from the 5′ end of the human Kalrn gene and expressed in the human neuronal cell line, SH-SY5Y. We propose that the zebrafish lncRNA durga maintains dendritic length and density through regulation of kalrna expression and this may have further implications in mammalian systems.
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Affiliation(s)
- Mayuresh A Sarangdhar
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India.,Academy of Scientific and Innovative Research (AcSIR)New Delhi, India
| | - Divya Chaubey
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India
| | - Abhishek Bhatt
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India
| | - Monisha Km
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India
| | - Manish Kumar
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India
| | - Shashi Ranjan
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India
| | - Beena Pillai
- Functional Genomics, Council of Scientific and Industrial Research (CSIR), Institute of Genomics and Integrative Biology (IGIB)New Delhi, India.,Academy of Scientific and Innovative Research (AcSIR)New Delhi, India
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4
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Makrythanasis P, Guipponi M, Santoni FA, Zaki M, Issa MY, Ansar M, Hamamy H, Antonarakis SE. Exome sequencing discloses KALRN homozygous variant as likely cause of intellectual disability and short stature in a consanguineous pedigree. Hum Genomics 2016; 10:26. [PMID: 27421267 PMCID: PMC4947303 DOI: 10.1186/s40246-016-0082-2] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2016] [Accepted: 07/05/2016] [Indexed: 02/06/2023] Open
Abstract
BACKGROUND The recent availability of whole-exome sequencing has opened new possibilities for the evaluation of individuals with genetically undiagnosed intellectual disability. RESULTS We report two affected siblings, offspring of first-cousin parents, with intellectual disability, hypotonia, short stature, growth hormone deficiency, and delayed bone age. All members of the nuclear family were genotyped, and exome sequencing was performed in one of the affected individuals. We used an in-house algorithm (CATCH v1.1) that combines homozygosity mapping with exome sequencing results and provides a list of candidate variants. One identified novel homozygous missense variant in KALRN (NM_003947.4:c.3644C>A: p.(Thr1215Lys)) was predicted to be pathogenic by all pathogenicity prediction software used (SIFT, PolyPhen, Mutation Taster). KALRN encodes the protein kalirin, which is a GTP-exchange factor protein with a reported role in cytoskeletal remodeling and dendritic spine formation in neurons. It is known that mice with ablation of Kalrn exhibit age-dependent functional deficits and behavioral phenotypes. CONCLUSION Exome sequencing provided initial evidence linking KALRN to monogenic intellectual disability in man, and we propose that KALRN is the causative gene for the autosomal recessive phenotype in this family.
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Affiliation(s)
- Periklis Makrythanasis
- Department of Genetic Medicine and Development, University of Geneva, 1 Rue Michel-Servet, 1211, Geneva, Switzerland.,Service of Genetic Medicine, University Hospitals of Geneva, Geneva, Switzerland
| | - Michel Guipponi
- Service of Genetic Medicine, University Hospitals of Geneva, Geneva, Switzerland
| | - Federico A Santoni
- Department of Genetic Medicine and Development, University of Geneva, 1 Rue Michel-Servet, 1211, Geneva, Switzerland
| | - Maha Zaki
- Department of Clinical Genetics, National Research Centre, Cairo, Egypt
| | - Mahmoud Y Issa
- Department of Clinical Genetics, National Research Centre, Cairo, Egypt
| | - Muhammad Ansar
- Department of Genetic Medicine and Development, University of Geneva, 1 Rue Michel-Servet, 1211, Geneva, Switzerland
| | - Hanan Hamamy
- Department of Genetic Medicine and Development, University of Geneva, 1 Rue Michel-Servet, 1211, Geneva, Switzerland.
| | - Stylianos E Antonarakis
- Department of Genetic Medicine and Development, University of Geneva, 1 Rue Michel-Servet, 1211, Geneva, Switzerland. .,Service of Genetic Medicine, University Hospitals of Geneva, Geneva, Switzerland. .,iGE3, Institute of Genetics and Genomics of Geneva, Geneva, Switzerland.
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5
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Miller MB, Vishwanatha KS, Mains RE, Eipper BA. An N-terminal Amphipathic Helix Binds Phosphoinositides and Enhances Kalirin Sec14 Domain-mediated Membrane Interactions. J Biol Chem 2015; 290:13541-55. [PMID: 25861993 DOI: 10.1074/jbc.m115.636746] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2015] [Indexed: 11/06/2022] Open
Abstract
Previous studies revealed an essential role for the lipid-binding Sec14 domain of kalirin (KalSec14), but its mechanism of action is not well understood. Because alternative promoter usage appends unique N-terminal peptides to the KalSec14 domain, we used biophysical, biochemical, and cell biological approaches to examine the two major products, bKalSec14 and cKalSec14. Promoter B encodes a charged, unstructured peptide, whereas promoter C encodes an amphipathic helix (Kal-C-helix). Both bKalSec14 and cKalSec14 interacted with lipids in PIP strip and liposome flotation assays, with significantly greater binding by cKalSec14 in both assays. Disruption of the hydrophobic face of the Kal-C-helix in cKalSec14KKED eliminated its increased liposome binding. Although cKalSec14 showed significantly reduced binding to liposomes lacking phosphatidylinositol phosphates or cholesterol, liposome binding by bKalSec14 and cKalSec14KKED was not affected. When expressed in AtT-20 cells, bKalSec14-GFP was diffusely localized, whereas cKalSec14-GFP localized to the trans-Golgi network and secretory granules. The amphipathic C-helix was sufficient for this localization. When AtT-20 cells were treated with a cell-permeant derivative of the Kal-C-helix (Kal-C-helix-Arg9), we observed increased secretion of a product stored in mature secretory granules, with no effect on basal secretion; a cell-permeant control peptide (Kal-C-helixKKED-Arg9) did not have this effect. Through its ability to control expression of a novel, phosphoinositide-binding amphipathic helix, Kalrn promoter usage is expected to affect function.
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Affiliation(s)
| | | | | | - Betty A Eipper
- From the Departments of Neuroscience and Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut 06030
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Son K, Smith TC, Luna EJ. Supervillin binds the Rac/Rho-GEF Trio and increases Trio-mediated Rac1 activation. Cytoskeleton (Hoboken) 2015; 72:47-64. [PMID: 25655724 DOI: 10.1002/cm.21210] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2014] [Accepted: 01/21/2015] [Indexed: 01/06/2023]
Abstract
We investigated cross-talk between the membrane-associated, myosin II-regulatory protein supervillin and the actin-regulatory small GTPases Rac1, RhoA, and Cdc42. Supervillin knockdown reduced Rac1-GTP loading, but not the GTP loading of RhoA or Cdc42, in HeLa cells with normal levels of the Rac1-activating protein Trio. No reduction in Rac1-GTP loading was observed when supervillin levels were reduced in Trio-depleted cells. Conversely, overexpression of supervillin isoform 1 (SV1) or, especially, isoform 4 (SV4) increased Rac1 activation. Inhibition of the Trio-mediated Rac1 guanine nucleotide exchange activity with ITX3 partially blocked the SV4-mediated increase in Rac1-GTP. Both SV4 and SV1 co-localized with Trio at or near the plasma membrane in ruffles and cell surface projections. Two sequences within supervillin bound directly to Trio spectrin repeats 4-7: SV1-171, which contains N-terminal residues found in both SV1 and SV4 and the SV4-specific differentially spliced coding exons 3, 4, and 5 within SV4 (SV4-E345; SV4 amino acids 276-669). In addition, SV4-E345 interacted with the homologous sequence in rat kalirin (repeats 4-7, amino acids 531-1101). Overexpressed SV1-174 and SV4-E345 affected Rac1-GTP loading, but only in cells with endogenous levels of Trio. Trio residues 771-1057, which contain both supervillin-interaction sites, exerted a dominant-negative effect on cell spreading. Supervillin and Trio knockdowns, separately or together, inhibited cell spreading, suggesting that supervillin regulates the Rac1 guanine nucleotide exchange activity of Trio, and potentially also kalirin, during cell spreading and lamellipodia extension.
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Affiliation(s)
- Kyonghee Son
- Department of Cell and Developmental Biology, Program in Cell & Developmental Dynamics, University of Massachusetts Medical School, Worcester, Massachusetts
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7
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Ma XM, Miller MB, Vishwanatha KS, Gross MJ, Wang Y, Abbott T, Lam TT, Mains RE, Eipper BA. Nonenzymatic domains of Kalirin7 contribute to spine morphogenesis through interactions with phosphoinositides and Abl. Mol Biol Cell 2014; 25:1458-71. [PMID: 24600045 PMCID: PMC4004595 DOI: 10.1091/mbc.e13-04-0215] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
Like several Rho GDP/GTP exchange factors (GEFs), Kalirin7 (Kal7) contains an N-terminal Sec14 domain and multiple spectrin repeats. A natural splice variant of Kalrn lacking the Sec14 domain and four spectrin repeats is unable to increase spine formation; our goal was to understand the function of the Sec14 and spectrin repeat domains. Kal7 lacking its Sec14 domain still increased spine formation, but the spines were short. Strikingly, Kal7 truncation mutants containing only the Sec14 domain and several spectrin repeats increased spine formation. The Sec14 domain bound phosphoinositides, a minor but crucial component of cellular membranes, and binding was increased by a phosphomimetic mutation. Expression of KalSec14-GFP in nonneuronal cells impaired receptor-mediated endocytosis, linking Kal7 to membrane trafficking. Consistent with genetic studies placing Abl, a non-receptor tyrosine kinase, and the Drosophila orthologue of Kalrn into the same signaling pathway, Abl1 phosphorylated two sites in the fourth spectrin repeat of Kalirin, increasing its sensitivity to calpain-mediated degradation. Treating cortical neurons of the wild-type mouse, but not the Kal7(KO) mouse, with an Abl inhibitor caused an increase in linear spine density. Phosphorylation of multiple sites in the N-terminal Sec14/spectrin region of Kal7 may allow coordination of the many signaling pathways contributing to spine morphogenesis.
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Affiliation(s)
- Xin-Ming Ma
- Department of Neuroscience, University of Connecticut Health Center, Farmington, CT 06030 WM Keck Foundation Biotechnology Resource Laboratory, Yale/NIDA Neuroproteomics Center, Yale University, New Haven, CT 06511
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8
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Cholesterol favors the anchorage of human dystrophin repeats 16 to 21 in membrane at physiological surface pressure. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1266-73. [PMID: 24440661 DOI: 10.1016/j.bbamem.2014.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2013] [Revised: 01/07/2014] [Accepted: 01/10/2014] [Indexed: 12/28/2022]
Abstract
Dystrophin (DYS) is a filamentous protein that connects the cytoskeleton and the extracellular matrix via the sarcolemma, conferring resistance to muscular cells. In this study, interactions between the DYS R16-21 fragment and lipids were examined using Langmuir films made of anionic and zwitterionic lipids. The film fluidity was modified by the addition of 15% cholesterol. Whatever the lipid mixture examined, at low surface pressure (20 mN/m) few differences appeared on the protein insertion and the presence of cholesterol did not affect the protein/lipid interactions. At high surface pressure (30 mN/m), the protein insertion was very low and occurred only in zwitterionic films in the liquid-expanded phase. In anionic films, electrostatic interactions prevented the protein insertion outright, and caused accumulation of the protein on the hydrophilic part of the monolayer. Addition of cholesterol to both lipid mixtures drastically modified the protein-lipid interactions: the DYS R16-21 insertion increased and its organization in the monolayer appeared to be more homogeneous. The presence of accessible cholesterol recognition amino-acid consensus sequences in this fragment may enhance the protein/membrane binding at physiological lateral pressure. These results suggest that the anchorage of dystrophin to the membrane in vivo may be stabilized by cholesterol-rich nano-domains in the inner leaflet of sarcolemma.
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Autore F, Pfuhl M, Quan X, Williams A, Roberts RG, Shanahan CM, Fraternali F. Large-scale modelling of the divergent spectrin repeats in nesprins: giant modular proteins. PLoS One 2013; 8:e63633. [PMID: 23671687 PMCID: PMC3646009 DOI: 10.1371/journal.pone.0063633] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2012] [Accepted: 04/09/2013] [Indexed: 11/29/2022] Open
Abstract
Nesprin-1 and nesprin-2 are nuclear envelope (NE) proteins characterized by a common structure of an SR (spectrin repeat) rod domain and a C-terminal transmembrane KASH [Klarsicht-ANC-Syne-homology] domain and display N-terminal actin-binding CH (calponin homology) domains. Mutations in these proteins have been described in Emery-Dreifuss muscular dystrophy and attributed to disruptions of interactions at the NE with nesprins binding partners, lamin A/C and emerin. Evolutionary analysis of the rod domains of the nesprins has shown that they are almost entirely composed of unbroken SR-like structures. We present a bioinformatical approach to accurate definition of the boundaries of each SR by comparison with canonical SR structures, allowing for a large-scale homology modelling of the 74 nesprin-1 and 56 nesprin-2 SRs. The exposed and evolutionary conserved residues identify important pbs for protein-protein interactions that can guide tailored binding experiments. Most importantly, the bioinformatics analyses and the 3D models have been central to the design of selected constructs for protein expression. 1D NMR and CD spectra have been performed of the expressed SRs, showing a folded, stable, high content α-helical structure, typical of SRs. Molecular Dynamics simulations have been performed to study the structural and elastic properties of consecutive SRs, revealing insights in the mechanical properties adopted by these modules in the cell.
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Affiliation(s)
- Flavia Autore
- Randall Division of Cell and Molecular Biophysics, School of Physical Sciences and Engineering, King's College London, London, United Kingdom
- Division of Cardiovascular Medicine, BHF Centre of Research Excellence, King's College London, London, United Kingdom
| | - Mark Pfuhl
- Randall Division of Cell and Molecular Biophysics, School of Physical Sciences and Engineering, King's College London, London, United Kingdom
| | - Xueping Quan
- Randall Division of Cell and Molecular Biophysics, School of Physical Sciences and Engineering, King's College London, London, United Kingdom
| | - Aisling Williams
- Randall Division of Cell and Molecular Biophysics, School of Physical Sciences and Engineering, King's College London, London, United Kingdom
- Division of Cardiovascular Medicine, BHF Centre of Research Excellence, King's College London, London, United Kingdom
| | - Roland G. Roberts
- Division of Medical and Molecular Genetics, Kings College London, Guy's Hospital, London, United Kingdom
| | - Catherine M. Shanahan
- Division of Cardiovascular Medicine, BHF Centre of Research Excellence, King's College London, London, United Kingdom
| | - Franca Fraternali
- Randall Division of Cell and Molecular Biophysics, School of Physical Sciences and Engineering, King's College London, London, United Kingdom
- The Thomas Young Centre for Theory and Simulation of Materials, London, United Kingdom
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Wu JH, Fanaroff AC, Sharma KC, Smith LS, Brian L, Eipper BA, Mains RE, Freedman NJ, Zhang L. Kalirin promotes neointimal hyperplasia by activating Rac in smooth muscle cells. Arterioscler Thromb Vasc Biol 2013; 33:702-8. [PMID: 23288169 DOI: 10.1161/atvbaha.112.300234] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
OBJECTIVE Kalirin is a multifunctional protein that contains 2 guanine nucleotide exchange factor domains for the GTPases Rac1 and RhoA. Variants of KALRN have been associated with atherosclerosis in humans, but Kalirin's activity has been characterized almost exclusively in the central nervous system. We therefore tested the hypothesis that Kalirin functions as a Rho-guanine nucleotide exchange factor in arterial smooth muscle cells (SMCs). APPROACH AND RESULTS Kalirin-9 protein is expressed abundantly in aorta and bone marrow, as well as in cultured SMCs, endothelial cells, and macrophages. Moreover, arterial Kalirin was upregulated during early atherogenesis in apolipoprotein E-deficient mice. In cultured SMCs, signaling was affected similarly in 3 models of Kalirin loss-of-function: heterozygous Kalrn deletion, Kalirin RNAi, and treatment with the Kalirin Rho-guanine nucleotide exchange factor -1 inhibitor 1-(3-nitrophenyl)-1H-pyrrole-2,5-dione. With reduced Kalirin function, SMCs showed normal RhoA activation but diminished Rac1 activation, assessed as reduced Rac-GTP levels, p21-activated kinase autophosphorylation, and SMC migration. Kalrn(-/+) SMCs proliferated 30% less rapidly than wild-type SMCs. Neointimal hyperplasia engendered by carotid endothelial denudation was ≈60% less in Kalrn(-/+) and SMC-specific Kalrn(-/+) mice than in control mice. CONCLUSIONS Kalirin functions as a guanine nucleotide exchange factor for Rac1 in SMCs, and promotes SMC migration and proliferation both in vitro and in vivo.
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Affiliation(s)
- Jiao-Hui Wu
- Department of Medicine, Duke University Medical Center, Durham, NC 27710, USA
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