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Cisterna BA, Skruber K, Jane ML, Camesi CI, Nguyen ID, Liu TM, Warp PV, Black JB, Butler MT, Bear JE, Mor DE, Read TA, Vitriol EA. Prolonged depletion of profilin 1 or F-actin causes an adaptive response in microtubules. J Cell Biol 2024; 223:e202309097. [PMID: 38722279 PMCID: PMC11082369 DOI: 10.1083/jcb.202309097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Revised: 03/06/2024] [Accepted: 04/05/2024] [Indexed: 05/12/2024] Open
Abstract
In addition to its well-established role in actin assembly, profilin 1 (PFN1) has been shown to bind to tubulin and alter microtubule growth. However, whether PFN1's predominant control over microtubules in cells occurs through direct regulation of tubulin or indirectly through the polymerization of actin has yet to be determined. Here, we manipulated PFN1 expression, actin filament assembly, and actomyosin contractility and showed that reducing any of these parameters for extended periods of time caused an adaptive response in the microtubule cytoskeleton, with the effect being significantly more pronounced in neuronal processes. All the observed changes to microtubules were reversible if actomyosin was restored, arguing that PFN1's regulation of microtubules occurs principally through actin. Moreover, the cytoskeletal modifications resulting from PFN1 depletion in neuronal processes affected microtubule-based transport and mimicked phenotypes that are linked to neurodegenerative disease. This demonstrates how defects in actin can cause compensatory responses in other cytoskeleton components, which in turn significantly alter cellular function.
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Affiliation(s)
- Bruno A. Cisterna
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Kristen Skruber
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA
| | - Makenzie L. Jane
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Caleb I. Camesi
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Ivan D. Nguyen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Tatiana M. Liu
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Peyton V. Warp
- University of Miami Miller School of Medicine, Miami, FL, USA
| | - Joseph B. Black
- Division of Urologic Surgery, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Mitchell T. Butler
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - James E. Bear
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Danielle E. Mor
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Tracy-Ann Read
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Eric A. Vitriol
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
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2
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Cisterna BA, Skruber K, Jane ML, Camesi CI, Nguyen ID, Warp PV, Black JB, Butler MT, Bear JE, Tracy-Ann R, Vitriol EA. Cytoskeletal adaptation following long-term dysregulation of actomyosin in neuronal processes. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.25.554891. [PMID: 37662186 PMCID: PMC10473725 DOI: 10.1101/2023.08.25.554891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/05/2023]
Abstract
Microtubules, intermediate filaments, and actin are cytoskeletal polymer networks found within the cell. While each has unique functions, all the cytoskeletal elements must work together for cellular mechanics to be fully operative. This is achieved through crosstalk mechanisms whereby the different networks influence each other through signaling pathways and direct interactions. Because crosstalk can be complex, it is possible for perturbations in one cytoskeletal element to affect the others in ways that are difficult to predict. Here we investigated how long-term changes to the actin cytoskeleton affect microtubules and intermediate filaments. Reducing F-actin or actomyosin contractility increased acetylated microtubules and intermediate filament expression, with the effect being significantly more pronounced in neuronal processes. Changes to microtubules were completely reversible if F-actin and myosin activity is restored. Moreover, the altered microtubules in neuronal processes resulting from F-actin depletion caused significant changes to microtubule-based transport, mimicking phenotypes that are linked to neurodegenerative disease. Thus, defects in actin dynamics cause a compensatory response in other cytoskeleton components which profoundly alters cellular function.
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Affiliation(s)
- Bruno A. Cisterna
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Kristen Skruber
- Department of Cellular and Molecular Pharmacology, University of California San Francisco, San Francisco, CA, USA
| | - Makenzie L. Jane
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Caleb I. Camesi
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Ivan D. Nguyen
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Peyton V. Warp
- University of Miami Miller School of Medicine, Miami, FL, USA
| | - Joseph B. Black
- Division of Urologic Surgery, Beth Israel Deaconess Medical Center, Boston, MA, USA
| | - Mitchell T. Butler
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - James E. Bear
- Department of Cell Biology and Physiology, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina at Chapel Hill School of Medicine, Chapel Hill, NC, USA
| | - Read Tracy-Ann
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
| | - Eric A. Vitriol
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia at Augusta University, Augusta, GA, USA
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3
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Ivanova A, Atakpa-Adaji P. Phosphatidylinositol 4,5-bisphosphate and calcium at ER-PM junctions - Complex interplay of simple messengers. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2023; 1870:119475. [PMID: 37098393 DOI: 10.1016/j.bbamcr.2023.119475] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/15/2023] [Revised: 03/05/2023] [Accepted: 04/03/2023] [Indexed: 04/27/2023]
Abstract
Endoplasmic reticulum-plasma membrane contact sites (ER-PM MCS) are a specialised domain involved in the control of Ca2+ dynamics and various Ca2+-dependent cellular processes. Intracellular Ca2+ signals are broadly supported by Ca2+ release from intracellular Ca2+ channels such as inositol 1,4,5-trisphosphate receptors (IP3Rs) and subsequent store-operated Ca2+ entry (SOCE) across the PM to replenish store content. IP3Rs sit in close proximity to the PM where they can easily access newly synthesised IP3, interact with binding partners such as actin, and localise adjacent to ER-PM MCS populated by the SOCE machinery, STIM1-2 and Orai1-3, to possibly form a locally regulated unit of Ca2+ influx. PtdIns(4,5)P2 is a multiplex regulator of Ca2+ signalling at the ER-PM MCS interacting with multiple proteins at these junctions such as actin and STIM1, whilst also being consumed as a substrate for phospholipase C to produce IP3 in response to extracellular stimuli. In this review, we consider the mechanisms regulating the synthesis and turnover of PtdIns(4,5)P2 via the phosphoinositide cycle and its significance for sustained signalling at the ER-PM MCS. Furthermore, we highlight recent insights into the role of PtdIns(4,5)P2 in the spatiotemporal organization of signalling at ER-PM junctions and raise outstanding questions on how this multi-faceted regulation occurs.
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Affiliation(s)
- Adelina Ivanova
- Department of Pharmacology, Tennis Court Road, Cambridge CB2 1PD, UK.
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4
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Zhu C, Iwase M, Li Z, Wang F, Quinet A, Vindigni A, Shao J. Profilin-1 regulates DNA replication forks in a context-dependent fashion by interacting with SNF2H and BOD1L. Nat Commun 2022; 13:6531. [PMID: 36319634 PMCID: PMC9626489 DOI: 10.1038/s41467-022-34310-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Accepted: 10/21/2022] [Indexed: 12/04/2022] Open
Abstract
DNA replication forks are tightly controlled by a large protein network consisting of well-known core regulators and many accessory factors which remain functionally undefined. In this study, we report previously unknown nuclear functions of the actin-binding factor profilin-1 (PFN1) in DNA replication, which occur in a context-dependent fashion and require its binding to poly-L-proline (PLP)-containing proteins instead of actin. In unperturbed cells, PFN1 increases DNA replication initiation and accelerates fork progression by binding and stimulating the PLP-containing nucleosome remodeler SNF2H. Under replication stress, PFN1/SNF2H increases fork stalling and functionally collaborates with fork reversal enzymes to enable the over-resection of unprotected forks. In addition, PFN1 binds and functionally attenuates the PLP-containing fork protector BODL1 to increase the resection of a subset of stressed forks. Accordingly, raising nuclear PFN1 level decreases genome stability and cell survival during replication stress. Thus, PFN1 is a multi-functional regulator of DNA replication with exploitable anticancer potential.
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Affiliation(s)
- Cuige Zhu
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Mari Iwase
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Ziqian Li
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- Department of Microbial and Biochemical Pharmacy, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, China
| | - Faliang Wang
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
| | - Annabel Quinet
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- UMR Genetic Stability Stem Cells and Radiation, University of Paris and University of Paris-Saclay, INSERM, iRCM/IBFJ CEA, Fontenay-aux-Roses, France
| | - Alessandro Vindigni
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, 63110, USA
| | - Jieya Shao
- Divison of Oncology, Department of Medicine, Washington University School of Medicine, St. Louis, MO, USA.
- Siteman Cancer Center, Washington University School of Medicine, St. Louis, MO, 63110, USA.
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5
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Wang Y, Lu Y, Wan R, Wang Y, Zhang C, Li M, Deng P, Cao L, Hu C. Profilin 1 Induces Tumor Metastasis by Promoting Microvesicle Secretion Through the ROCK 1/p-MLC Pathway in Non-Small Cell Lung Cancer. Front Pharmacol 2022; 13:890891. [PMID: 35586060 PMCID: PMC9108340 DOI: 10.3389/fphar.2022.890891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2022] [Accepted: 04/12/2022] [Indexed: 11/13/2022] Open
Abstract
Profilin 1 (PFN1), an actin-binding protein, plays contrasting roles in the metastasis of several cancers; however, its role in non-small cell lung cancer (NSCLC) metastasis remains unclear. Here, PFN1 expression was upregulated in metastatic NSCLC tissues. PFN1 overexpression significantly promotes NSCLC metastasis in vitro and in vivo. Proteomics analysis revealed PFN1 involvment in microvesicles (MVs) secretion. In vitro experiments confirmed that PFN1 overexpression increased secretion of MVs. MVs are important mediators of metastasis. Here, we show an increased abundance of MVs in the sera of patients with metastatic NSCLC compared to that in the sera of patients with non-metastatic NSCLC. Both in vitro and in vivo experiments revealed that PFN1 could increase MV secretion, and MVs derived from PFN1-overexpressing cells markedly promoted NSCLC metastasis. We then elucidated the mechanisms underlying PFN1-mediated regulation of MVs and found that PFN1 could interact with ROCK1 and enhance its kinase activity to promote myosin light chain (MLC) phosphorylation for MV secretion. Inhibition of ROCK1 decreased MV secretion and partially reversed the PFN1-induced promotion of NSCLC metastasis. Collectively, these findings show that PFN1 regulates MV secretion to promote NSCLC metastasis. PFN1 and MVs represent potential predictors or therapeutic targets for NSCLC metastasis.
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Affiliation(s)
- Ya Wang
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Yichen Lu
- Department of Oncology, Hunan Provincial People’s Hospital/The First Affiliated Hospital of Hunan Normal University, Changsha, China
| | - Rongjun Wan
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Yang Wang
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Chunfang Zhang
- Department of Thoracic Surgery, Xiangya Hospital, Central South University, Changsha, China
| | - Min Li
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Pengbo Deng
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Liming Cao
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
| | - Chengping Hu
- Department of Respiratory Medicine, Xiangya Hospital, Central South University, Changsha, China
- *Correspondence: Chengping Hu,
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6
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Lohraseb I, McCarthy P, Secker G, Marchant C, Wu J, Ali N, Kumar S, Daly RJ, Harvey NL, Kawabe H, Kleifeld O, Wiszniak S, Schwarz Q. Global ubiquitinome profiling identifies NEDD4 as a regulator of Profilin 1 and actin remodelling in neural crest cells. Nat Commun 2022; 13:2018. [PMID: 35440627 PMCID: PMC9018756 DOI: 10.1038/s41467-022-29660-3] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 03/24/2022] [Indexed: 01/02/2023] Open
Abstract
The ubiquitin ligase NEDD4 promotes neural crest cell (NCC) survival and stem-cell like properties to regulate craniofacial and peripheral nervous system development. However, how ubiquitination and NEDD4 control NCC development remains unknown. Here we combine quantitative analysis of the proteome, transcriptome and ubiquitinome to identify key developmental signalling pathways that are regulated by NEDD4. We report 276 NEDD4 targets in NCCs and show that loss of NEDD4 leads to a pronounced global reduction in specific ubiquitin lysine linkages. We further show that NEDD4 contributes to the regulation of the NCC actin cytoskeleton by controlling ubiquitination and turnover of Profilin 1 to modulate filamentous actin polymerization. Taken together, our data provide insights into how NEDD4-mediated ubiquitination coordinates key regulatory processes during NCC development. Here the authors combine multi-omics approaches to uncover a role for ubiquitination and the ubiquitin ligase NEDD4 in targeting the actin binding protein Profilin 1 to regulate actin polymerisation in neural crest cells.
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Affiliation(s)
- Iman Lohraseb
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Peter McCarthy
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Genevieve Secker
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Ceilidh Marchant
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Jianmin Wu
- Kinghorn Cancer Centre & Cancer Division, Garvan Institute of Medical Research, Sydney, NSW, 2010, Australia.,St Vincent's Clinical School, University of New South Wales, Sydney, NSW, 2010, Australia
| | - Naveid Ali
- Bone Therapeutics Group, Bone Biology Division, Garvan Institute of Medical Research, Sydney, 2010, Australia
| | - Sharad Kumar
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Roger J Daly
- Department of Biochemistry and Molecular Biology, School of Biomedical Sciences, Monash University, Victoria, 3800, Australia
| | - Natasha L Harvey
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Hiroshi Kawabe
- Department of Molecular Neurobiology, Max Planck Institute for Experimental Medicine, Goettingen, 37075, Germany.,Department of Pharmacology, Gunma University Graduate School of Medicine, Showa-machi, Maebashi, Gunma, 371-8511, Japan
| | - Oded Kleifeld
- Faculty of Biology, Technion-Israel Institute of Technology, Technion City, Haifa, 3200003, Israel
| | - Sophie Wiszniak
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia
| | - Quenten Schwarz
- Centre for Cancer Biology, University of South Australia and SA Pathology, GPO Box 2471, Adelaide, 5000, Australia.
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7
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Murk K, Ornaghi M, Schiweck J. Profilin Isoforms in Health and Disease - All the Same but Different. Front Cell Dev Biol 2021; 9:681122. [PMID: 34458253 PMCID: PMC8387879 DOI: 10.3389/fcell.2021.681122] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Accepted: 07/12/2021] [Indexed: 12/11/2022] Open
Abstract
Profilins are small actin binding proteins, which are structurally conserved throughout evolution. They are probably best known to promote and direct actin polymerization. However, they also participate in numerous cell biological processes beyond the roles typically ascribed to the actin cytoskeleton. Moreover, most complex organisms express several profilin isoforms. Their cellular functions are far from being understood, whereas a growing number of publications indicate that profilin isoforms are involved in the pathogenesis of various diseases. In this review, we will provide an overview of the profilin family and "typical" profilin properties including the control of actin dynamics. We will then discuss the profilin isoforms of higher animals in detail. In terms of cellular functions, we will focus on the role of Profilin 1 (PFN1) and Profilin 2a (PFN2a), which are co-expressed in the central nervous system. Finally, we will discuss recent findings that link PFN1 and PFN2a to neurological diseases, such as amyotrophic lateral sclerosis (ALS), Fragile X syndrome (FXS), Huntington's disease and spinal muscular atrophy (SMA).
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Affiliation(s)
- Kai Murk
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Marta Ornaghi
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
| | - Juliane Schiweck
- Institute of Biochemistry, Charité Universitätsmedizin Berlin, Berlin, Germany
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8
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Abstract
Dynamic remodeling of the actin cytoskeleton is an essential feature for virtually all actin-dependent cellular processes, including cell migration, cell cycle progression, chromatin remodeling and gene expression, and even the DNA damage response. An altered actin cytoskeleton is a structural hallmark associated with numerous pathologies ranging from cardiovascular diseases to immune disorders, neurological diseases and cancer. The actin cytoskeleton in cells is regulated through the orchestrated actions of a myriad of actin-binding proteins. In this Review, we provide a brief overview of the structure and functions of the actin-monomer-binding protein profilin-1 (Pfn1) and then discuss how dysregulated expression of Pfn1 contributes to diseases associated with the cardiovascular system.
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Affiliation(s)
| | - David Gau
- Bioengineering, University of Pittsburgh
| | - Partha Roy
- Bioengineering, University of Pittsburgh.,Pathology, University of Pittsburgh, 306 Center for Bioengineering, University of Pittsburgh, 300 Technology Drive, Pittsburgh, PA 15219, USA
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9
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Iyer DN, Faruq O, Zhang L, Rastgoo N, Liu A, Chang H. Pathophysiological roles of myristoylated alanine-rich C-kinase substrate (MARCKS) in hematological malignancies. Biomark Res 2021; 9:34. [PMID: 33958003 PMCID: PMC8101130 DOI: 10.1186/s40364-021-00286-9] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2021] [Accepted: 04/16/2021] [Indexed: 12/17/2022] Open
Abstract
The myristoylated alanine-rich C-kinase substrate (MARCKS) protein has been at the crossroads of multiple signaling pathways that govern several critical operations in normal and malignant cellular physiology. Functioning as a target of protein kinase C, MARCKS shuttles between the phosphorylated cytosolic form and the unphosphorylated plasma membrane-bound states whilst regulating several molecular partners including, but not limited to calmodulin, actin, phosphatidylinositol-4,5-bisphosphate, and phosphoinositide-3-kinase. As a result of these interactions, MARCKS directly or indirectly modulates a host of cellular functions, primarily including cytoskeletal reorganization, membrane trafficking, cell secretion, inflammatory response, cell migration, and mitosis. Recent evidence indicates that dysregulated expression of MARCKS is associated with the development and progression of hematological cancers. While it is understood that MARCKS impacts the overall carcinogenesis as well as plays a part in determining the disease outcome in blood cancers, we are still at an early stage of interpreting the pathophysiological roles of MARCKS in neoplastic disease. The situation is further complicated by contradictory reports regarding the role of phosphorylated versus an unphosphorylated form of MARCKS as an oncogene versus tumor suppressor in blood cancers. In this review, we will investigate the current body of knowledge and evolving concepts of the physical properties, molecular network, functional attributes, and the likely pathogenic roles of MARCKS in hematological malignancies. Key emphasis will also be laid upon understanding the novel mechanisms by which MARCKS determines the overall disease prognosis by playing a vital role in the induction of therapeutic resistance. Additionally, we will highlight the importance of MARCKS as a valuable therapeutic target in blood cancers and will discuss the potential of existing strategies available to tackle MARCKS-driven blood cancers.
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Affiliation(s)
- Deepak Narayanan Iyer
- Laboratory medicine program, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada
| | - Omar Faruq
- Laboratory medicine program, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada
| | - Lun Zhang
- Laboratory medicine program, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada
| | - Nasrin Rastgoo
- Laboratory medicine program, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada
| | - Aijun Liu
- Department of Hematology, Beijing Chaoyang Hospital, Capital University, Beijing, China.
| | - Hong Chang
- Laboratory medicine program, Toronto General Hospital, University Health Network, University of Toronto, Toronto, Canada.
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10
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Pimm ML, Hotaling J, Henty-Ridilla JL. Profilin choreographs actin and microtubules in cells and cancer. INTERNATIONAL REVIEW OF CELL AND MOLECULAR BIOLOGY 2020; 355:155-204. [PMID: 32859370 PMCID: PMC7461721 DOI: 10.1016/bs.ircmb.2020.05.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Actin and microtubules play essential roles in aberrant cell processes that define and converge in cancer including: signaling, morphology, motility, and division. Actin and microtubules do not directly interact, however shared regulators coordinate these polymers. While many of the individual proteins important for regulating and choreographing actin and microtubule behaviors have been identified, the way these molecules collaborate or fail in normal or disease contexts is not fully understood. Decades of research focus on Profilin as a signaling molecule, lipid-binding protein, and canonical regulator of actin assembly. Recent reports demonstrate that Profilin also regulates microtubule dynamics and polymerization. Thus, Profilin can coordinate both actin and microtubule polymer systems. Here we reconsider the biochemical and cellular roles for Profilin with a focus on the essential cytoskeletal-based cell processes that go awry in cancer. We also explore how the use of model organisms has helped to elucidate mechanisms that underlie the regulatory essence of Profilin in vivo and in the context of disease.
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Affiliation(s)
- Morgan L Pimm
- Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY, United States
| | - Jessica Hotaling
- Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY, United States
| | - Jessica L Henty-Ridilla
- Department of Cell and Developmental Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY, United States; Department of Biochemistry and Molecular Biology, State University of New York (SUNY) Upstate Medical University, Syracuse, NY, United States.
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11
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Kłopocka W, Korczyński J, Pomorski P. Cytoskeleton and Nucleotide Signaling in Glioma C6 Cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2020; 1202:109-128. [PMID: 32034711 DOI: 10.1007/978-3-030-30651-9_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
This chapter describes signaling pathways, stimulated by the P2Y2 nucleotide receptor (P2Y2R), that regulate cellular processes dependent on actin cytoskeleton dynamics in glioma C6 cells. P2Y2R coupled with G-proteins, in response to ATP or UTP, regulates the level of iphosphatidylinositol-4,5-bisphosphate (PIP2) which modulates a variety of actin binding proteins and is involved in calcium response and activates Rac1 and RhoA proteins. The RhoA/ROCK signaling pathway plays an important role in contractile force generation needed for the assembly of stress fibers, focal adhesions and for tail retraction during cell migration. Blocking of this pathway by a specific Rho-kinase inhibitor induces changes in F-actin organization and cell shape and decreases the level of phosphorylated myosin II and cofilin. In glioma C6 cells these changes are reversed after UTP stimulation of P2Y2R. Signaling pathways responsible for this compensation are calcium signaling which regulates MLC kinase activation via calmodulin, and the Rac1/PAK/LIMK cascade. Stimulation of the Rac1 mediated pathway via Go proteins needs additional interaction between αvβ5 integrins and P2Y2Rs. Calcium free medium, or growing of the cells in suspension, prevents Gαo activation by P2Y2 receptors. Rac1 activation is necessary for cofilin phosphorylation as well as integrin activation needed for focal complexes formation and stabilization of lamellipodium. Inhibition of positive Rac1 regulation prevents glioma C6 cells from recovery of control cell like morphology.
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Affiliation(s)
- Wanda Kłopocka
- Faculty of Biology and Environmental Sciences, Cardinal Stefan Wyszynski University, Warsaw, Poland.
| | - Jarosław Korczyński
- M. Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
| | - Paweł Pomorski
- M. Nencki Institute of Experimental Biology of Polish Academy of Sciences, Warsaw, Poland
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12
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Walter LM, Franz P, Lindner R, Tsiavaliaris G, Hensel N, Claus P. Profilin2a-phosphorylation as a regulatory mechanism for actin dynamics. FASEB J 2019; 34:2147-2160. [PMID: 31908005 DOI: 10.1096/fj.201901883r] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2019] [Revised: 09/16/2019] [Accepted: 11/14/2019] [Indexed: 12/25/2022]
Abstract
Profilin is a major regulator of actin dynamics in multiple specific processes localized in different cellular compartments. This specificity is not only meditated by its binding to actin but also its interaction with phospholipids such as phosphatidylinositol (4,5)-bisphosphate (PIP2 ) at the membrane and a plethora of proteins containing poly-L-proline (PLP) stretches. These interactions are fine-tuned by posttranslational modifications such as phosphorylation. Several phospho-sites have already been identified for profilin1, the ubiquitously expressed isoform. However, little is known about the phosphorylation of profilin2a. Profilin2a is a neuronal isoform important for synapse function. Here, we identified several putative profilin2a phospho-sites in silico and tested recombinant phospho-mimetics with regard to their actin-, PLP-, and PIP2 -binding properties. Moreover, we assessed their impact on actin dynamics employing a pyrene-actin polymerization assay. Results indicate that distinct phospho-sites modulate specific profilin2a functions. We could identify a molecular switch site at serine residue 71 which completely abrogated actin binding-as well as other sites important for fine-tuning of different functions, for example, tyrosine 29 for PLP binding. Our findings suggest that differential profilin2a phosphorylation is a sensitive mechanism for regulating its neuronal functions. Moreover, the dysregulation of profilin2a phosphorylation may contribute to neurodegeneration.
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Affiliation(s)
- Lisa Marie Walter
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,Center of Systems Neuroscience, Hannover, Germany
| | - Peter Franz
- Institute of Cellular Biophysics, Hannover Medical School, Hannover, Germany
| | - Robert Lindner
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany
| | | | - Niko Hensel
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,Center of Systems Neuroscience, Hannover, Germany
| | - Peter Claus
- Institute of Neuroanatomy and Cell Biology, Hannover Medical School, Hannover, Germany.,Center of Systems Neuroscience, Hannover, Germany
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Janmey PA, Bucki R, Radhakrishnan R. Regulation of actin assembly by PI(4,5)P2 and other inositol phospholipids: An update on possible mechanisms. Biochem Biophys Res Commun 2018; 506:307-314. [PMID: 30139519 DOI: 10.1016/j.bbrc.2018.07.155] [Citation(s) in RCA: 72] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2018] [Revised: 06/21/2018] [Accepted: 07/31/2018] [Indexed: 01/15/2023]
Abstract
Actin cytoskeleton dynamics depend on a tight regulation of actin filament formation from an intracellular pool of monomers, followed by their linkage to each other or to cell membranes, followed by their depolymerization into a fresh pool of actin monomers. The ubiquitous requirement for continuous actin remodeling that is necessary for many cellular functions is orchestrated in large part by actin binding proteins whose affinity for actin is altered by inositol phospholipids, most prominently PI(4,5)P2 (phosphatidylinositol 4,5-bisphosphate). The kinetics of PI(4,5)P2 synthesis and hydrolysis, its lateral distribution within the lipid bilayer, and coincident detection of PI(4,5)P2 and another signal, all play a role in determining when and where a particular PI(4,5)P2-regulated protein is inactivated or activated to exert its effect on the actin cytoskeleton. This review summarizes a range of models that have been developed to explain how PI(4,5)P2 might function in the complex chemical and structural environment of the cell based on a combination of experiment and computational studies.
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Affiliation(s)
- Paul A Janmey
- Department of Physiology, University of Pennsylvania, Philadelphia, PA, USA; Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA.
| | - Robert Bucki
- Institute for Medicine and Engineering, University of Pennsylvania, Philadelphia, PA, USA; Department of Microbiological and Nanobiomedical Engineering, Medical University of Bialystok, Bialystok, Poland
| | - Ravi Radhakrishnan
- Department of Bioengineering, University of Pennsylvania, Philadelphia, PA, USA
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14
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Xu W, Liu W, Ye R, Mazarei M, Huang D, Zhang X, Stewart CN. A profilin gene promoter from switchgrass (Panicum virgatum L.) directs strong and specific transgene expression to vascular bundles in rice. PLANT CELL REPORTS 2018; 37:587-597. [PMID: 29340787 DOI: 10.1007/s00299-018-2253-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Accepted: 01/05/2018] [Indexed: 05/25/2023]
Abstract
A switchgrass vascular tissue-specific promoter (PvPfn2) and its 5'-end serial deletions drive high levels of vascular bundle transgene expression in transgenic rice. Constitutive promoters are widely used for crop genetic engineering, which can result in multiple off-target effects, including suboptimal growth and epigenetic gene silencing. These problems can be potentially avoided using tissue-specific promoters for targeted transgene expression. One particularly urgent need for targeted cell wall modification in bioenergy crops, such as switchgrass (Panicum virgatum L.), is the development of vasculature-active promoters to express cell wall-affective genes only in the specific tissues, i.e., xylem and phloem. From a switchgrass expression atlas we identified promoter sequence upstream of a vasculature-specific switchgrass profilin gene (PvPfn2), especially in roots, nodes and inflorescences. When the putative full-length (1715 bp) and 5'-end serial deletions of the PvPfn2 promoter (shortest was 413 bp) were used to drive the GUS reporter expression in stably transformed rice (Oryza sativa L.), strong vasculature-specificity was observed in various tissues including leaves, leaf sheaths, stems, and flowers. The promoters were active in both phloem and xylem. It is interesting to note that the promoter was active in many more tissues in the heterologous rice system than in switchgrass. Surprisingly, all four 5'-end promoter deletions, including the shortest fragment, had the same expression patterns as the full-length promoter and with no attenuation in GUS expression in rice. These results indicated that the PvPfn2 promoter variants are new tools to direct transgene expression specifically to vascular tissues in monocots. Of special interest is the very compact version of the promoter, which could be of use for vasculature-specific genetic engineering in monocots.
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Affiliation(s)
- Wenzhi Xu
- Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA
- Department of Grassland Science, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - Wusheng Liu
- Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA
- Department of Horticultural Science, North Carolina State University, Raleigh, NC, USA
| | - Rongjian Ye
- Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA
| | - Mitra Mazarei
- Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA
| | - Debao Huang
- Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA
| | - Xinquan Zhang
- Department of Grassland Science, Sichuan Agricultural University, Chengdu, Sichuan, China
| | - C Neal Stewart
- Department of Plant Sciences, University of Tennessee, Knoxville, TN, USA.
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15
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Wang J, Vanga SK, Raghavan V. Effect of pre-harvest and post-harvest conditions on the fruit allergenicity: A review. Crit Rev Food Sci Nutr 2017; 59:1027-1043. [DOI: 10.1080/10408398.2017.1389691] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Affiliation(s)
- Jin Wang
- Department of Bioresource Engineering, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, Quebec H9 X 3V9, Canada
| | - Sai Kranthi Vanga
- Department of Bioresource Engineering, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, Quebec H9 X 3V9, Canada
| | - Vijaya Raghavan
- Department of Bioresource Engineering, Faculty of Agricultural and Environmental Sciences, McGill University, Sainte-Anne-de-Bellevue, Quebec H9 X 3V9, Canada
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Ziemba BP, Swisher GH, Masson G, Burke JE, Williams RL, Falke JJ. Regulation of a Coupled MARCKS-PI3K Lipid Kinase Circuit by Calmodulin: Single-Molecule Analysis of a Membrane-Bound Signaling Module. Biochemistry 2016; 55:6395-6405. [PMID: 27933776 DOI: 10.1021/acs.biochem.6b00908] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Amoeboid cells that employ chemotaxis to travel up an attractant gradient possess a signaling network assembled on the leading edge of the plasma membrane that senses the gradient and remodels the actin mesh and cell membrane to drive movement in the appropriate direction. In leukocytes such as macrophages and neutrophils, and perhaps in other amoeboid cells as well, the leading edge network includes a positive feedback loop in which the signaling of multiple pathway components is cooperatively coupled. Cytoplasmic Ca2+ is a recently recognized component of the feedback loop at the leading edge where it stimulates phosphoinositide-3-kinase (PI3K) and the production of its product signaling lipid phosphatidylinositol 3,4,5-trisphosphate (PIP3). A previous study implicated Ca2+-activated protein kinase C (PKC) and the phosphatidylinositol 4,5-bisphosphate (PIP2) binding protein MARCKS as two important players in this signaling, because PKC phosphorylation of MARCKS releases free PIP2 that serves as the membrane binding target and substrate for PI3K. This study asks whether calmodulin (CaM), which is known to directly bind MARCKS, also stimulates PIP3 production by releasing free PIP2. Single-molecule fluorescence microscopy is used to quantify the surface density and enzyme activity of key protein components of the hypothesized Ca2+-CaM-MARCKS-PIP2-PI3K-PIP3 circuit. The findings show that CaM does stimulate PI3K lipid kinase activity by binding MARCKS and displacing it from PIP2 headgroups, thereby releasing free PIP2 that recruits active PI3K to the membrane and serves as the substrate for the generation of PIP3. The resulting CaM-triggered activation of PI3K is complete in seconds and is much faster than PKC-triggered activation, which takes minutes. Overall, the available evidence implicates both PKC and CaM in the coupling of Ca2+ and PIP3 signals and suggests these two different pathways have slow and fast activation kinetics, respectively.
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Affiliation(s)
- Brian P Ziemba
- Molecular Biophysics Program and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States
| | - G Hayden Swisher
- Molecular Biophysics Program and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States
| | - Glenn Masson
- Laboratory of Molecular Biology, Medical Research Council , Cambridge CB2 0QH, U.K
| | - John E Burke
- Laboratory of Molecular Biology, Medical Research Council , Cambridge CB2 0QH, U.K
| | - Roger L Williams
- Laboratory of Molecular Biology, Medical Research Council , Cambridge CB2 0QH, U.K
| | - Joseph J Falke
- Molecular Biophysics Program and Department of Chemistry and Biochemistry, University of Colorado , Boulder, Colorado 80309-0215, United States
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17
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Tariq N, Basharat Z, Butt S, Baig DN. Distribution analysis of profilin isoforms at transcript resolution with mRNA-seq and secondary structure in various organs of Rattus norvegicus. Gene 2016; 589:49-55. [PMID: 27185630 DOI: 10.1016/j.gene.2016.05.023] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2016] [Revised: 05/11/2016] [Accepted: 05/12/2016] [Indexed: 11/15/2022]
Abstract
Profilin (Pfn) is an actin binding protein, ubiquitously found in mammals and is essential for the actin polymerization in cells. In brain, it plays a pivotal role in neurogenesis and synapse formation by interacting with various proteins. Four Pfn isoforms have been identified in mammals. This study presents the identification and transcriptional expression of various Pfn isoforms (Pfn1, Pfn2, Pfn3 and Pfn4) in brain, heart, kidney, liver, and muscle and testis of Rattus norvegicus. Organs have been classified into groups based on some similarities. Group I includes brain and testis, Group II includes skeletal muscle and heart, while Group III includes kidney and liver. Pfn1 has been identified in all groups, Pfn2 and Pfn3 have been identified in group I, group III and in one organ (skeletal muscle) of group II. To the best of the authors knowledge, no report of Pfn1 and Pfn2 presence in testis, Pfn3 in brain, liver and skeletal muscle, Pfn4 in kidney and skeletal muscle exists to date. Transcriptional expression showed variations among expression level of different Pfn isoforms in various organs with respect to the control gene GADPH. We hypothesize that this could be attributed to profilin isoform specific mRNA structure and corresponding motifs, which generally contribute to similar or varied decay rates, cellular localization, post transcriptional regulation pattern and ligand binding.
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Affiliation(s)
- Naila Tariq
- Department of Biological sciences, Forman Christian College (A Chartered University), 54600 Lahore, Pakistan
| | - Zarrin Basharat
- Department of Environmental Sciences, Fatima Jinnah Women University, 46000 Rawalpindi, Pakistan
| | - Saba Butt
- Department of Biological sciences, Forman Christian College (A Chartered University), 54600 Lahore, Pakistan
| | - Deeba Noreen Baig
- Department of Biological sciences, Forman Christian College (A Chartered University), 54600 Lahore, Pakistan
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18
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Bhargav SP, Vahokoski J, Kallio JP, Torda AE, Kursula P, Kursula I. Two independently folding units of Plasmodium profilin suggest evolution via gene fusion. Cell Mol Life Sci 2015; 72:4193-203. [PMID: 26012696 PMCID: PMC11113795 DOI: 10.1007/s00018-015-1932-0] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2015] [Revised: 05/13/2015] [Accepted: 05/18/2015] [Indexed: 10/23/2022]
Abstract
Gene fusion is a common mechanism of protein evolution that has mainly been discussed in the context of multidomain or symmetric proteins. Less is known about fusion of ancestral genes to produce small single-domain proteins. Here, we show with a domain-swapped mutant Plasmodium profilin that this small, globular, apparently single-domain protein consists of two foldons. The separation of binding sites for different protein ligands in the two halves suggests evolution via an ancient gene fusion event, analogous to the formation of multidomain proteins. Finally, the two fragments can be assembled together after expression as two separate gene products. The possibility to engineer both domain-swapped dimers and half-profilins that can be assembled back to a full profilin provides perspectives for engineering of novel protein folds, e.g., with different scaffolding functions.
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Affiliation(s)
| | - Juha Vahokoski
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5400, 90014, Oulu, Finland
| | - Juha Pekka Kallio
- Helmholtz Centre for Infection Research, Notkestrasse 85, 22607, Hamburg, Germany
- German Electron Synchrotron (DESY), Notkestrasse 85, 22607, Hamburg, Germany
| | - Andrew E Torda
- Centre for Bioinformatics, University of Hamburg, Bundesstrasse 43, 20146, Hamburg, Germany
| | - Petri Kursula
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5400, 90014, Oulu, Finland
- Biocenter Oulu, University of Oulu, P.O. Box 5000, 90014, Oulu, Finland
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway
| | - Inari Kursula
- Faculty of Biochemistry and Molecular Medicine, University of Oulu, P.O. Box 5400, 90014, Oulu, Finland.
- Helmholtz Centre for Infection Research, Notkestrasse 85, 22607, Hamburg, Germany.
- German Electron Synchrotron (DESY), Notkestrasse 85, 22607, Hamburg, Germany.
- Department of Biomedicine, University of Bergen, Jonas Lies vei 91, 5009, Bergen, Norway.
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Pečar Fonović U, Kos J. Cathepsin X Cleaves Profilin 1 C-Terminal Tyr139 and Influences Clathrin-Mediated Endocytosis. PLoS One 2015; 10:e0137217. [PMID: 26325675 PMCID: PMC4567178 DOI: 10.1371/journal.pone.0137217] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2015] [Accepted: 07/18/2015] [Indexed: 11/19/2022] Open
Abstract
Cathepsin X, a cysteine carboxypeptidase, is upregulated in several types of cancer. Its molecular target in tumor cells is profilin 1, a known tumor suppressor and regulator of actin cytoskeleton dynamics. Cathepsin X cleaves off the C-terminal Tyr139 of profilin 1, affecting binding of poly-L-proline ligands and, consequently, tumor cell migration and invasion. Profilin 1 with mutations at the C-terminus, transiently expressed in prostate cancer cells PC-3, showed that Tyr139 is important for proper function of profilin 1 as a tumor suppressor. Cleaving off Tyr139 prevents the binding of clathrin, a poly-L-proline ligand involved in endocytosis. More profilin 1—clathrin complexes were present in PC-3 cells when cathepsin X was inhibited by its specific inhibitor AMS36 or silenced by siRNA. As a consequence, the endocytosis of FITC-labeled dextran and transferrin conjugate was significantly increased. These results constitute the first report of the regulation of clathrin-mediated endocytosis in tumor cells through proteolytic processing of profilin 1.
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Affiliation(s)
| | - Janko Kos
- Faculty of Pharmacy, University of Ljubljana, Ljubljana, Slovenia
- Department of Biotechnology, Jožef Stefan Institute, Ljubljana, Slovenia
- * E-mail:
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20
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The Folding process of Human Profilin-1, a novel protein associated with familial amyotrophic lateral sclerosis. Sci Rep 2015; 5:12332. [PMID: 26227615 PMCID: PMC4521207 DOI: 10.1038/srep12332] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2015] [Accepted: 06/17/2015] [Indexed: 12/11/2022] Open
Abstract
Human profilin-1 is a novel protein associated with a recently discovered form of familial amyotrophic lateral sclerosis. This urges the characterization of possible conformational states, different from the fully folded state, potentially able to initiate self-assembly. Under native conditions, profilin-1 is monomeric and possesses a well-defined secondary and tertiary structure. When incubated at low pH or with high urea concentrations, profilin-1 remains monomeric but populates unfolded states exhibiting larger hydrodynamic radius and disordered structure, as assessed by dynamic light scattering, far-UV circular dichroism and intrinsic fluorescence. Refolding from the urea-unfolded state was studied at equilibrium and in real-time using a stopped-flow apparatus. The results obtained with intrinsic fluorescence and circular dichroism indicate a single phase without significant changes of the corresponding signals before the major refolding transition. However, such a transition is preceded by a burst phase with an observed increase of ANS fluorescence, which indicates the conversion into a transiently populated collapsed state possessing solvent-exposed hydrophobic clusters. Kinetic analysis reveals that such state has a conformational stability comparable to that of the fully unfolded state. To our knowledge, profilin-1 is the first example of an amyloid-related protein where folding occurs in the absence of thermodynamically stable partially folded states.
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21
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Boopathy S, Silvas TV, Tischbein M, Jansen S, Shandilya SM, Zitzewitz JA, Landers JE, Goode BL, Schiffer CA, Bosco DA. Structural basis for mutation-induced destabilization of profilin 1 in ALS. Proc Natl Acad Sci U S A 2015; 112:7984-9. [PMID: 26056300 PMCID: PMC4491777 DOI: 10.1073/pnas.1424108112] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Mutations in profilin 1 (PFN1) are associated with amyotrophic lateral sclerosis (ALS); however, the pathological mechanism of PFN1 in this fatal disease is unknown. We demonstrate that ALS-linked mutations severely destabilize the native conformation of PFN1 in vitro and cause accelerated turnover of the PFN1 protein in cells. This mutation-induced destabilization can account for the high propensity of ALS-linked variants to aggregate and also provides rationale for their reported loss-of-function phenotypes in cell-based assays. The source of this destabilization is illuminated by the X-ray crystal structures of several PFN1 proteins, revealing an expanded cavity near the protein core of the destabilized M114T variant. In contrast, the E117G mutation only modestly perturbs the structure and stability of PFN1, an observation that reconciles the occurrence of this mutation in the control population. These findings suggest that a destabilized form of PFN1 underlies PFN1-mediated ALS pathogenesis.
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Affiliation(s)
- Sivakumar Boopathy
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Tania V Silvas
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Maeve Tischbein
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Silvia Jansen
- Department of Biology, Brandeis University, Waltham, MA 02453
| | - Shivender M Shandilya
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Jill A Zitzewitz
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - John E Landers
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Bruce L Goode
- Department of Biology, Brandeis University, Waltham, MA 02453
| | - Celia A Schiffer
- Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605
| | - Daryl A Bosco
- Department of Neurology, University of Massachusetts Medical School, Worcester, MA 01605; Department of Biochemistry and Molecular Pharmacology, University of Massachusetts Medical School, Worcester, MA 01605;
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Cytoskeleton and nucleotide signaling in glioma C6 cells. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2013; 986:103-19. [PMID: 22879066 DOI: 10.1007/978-94-007-4719-7_6] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
This chapter describes signaling pathways stimulated by the P2Y(2) nucleotide receptor (P2Y(2)R), that regulate cellular processes dependent on actin cytoskeleton dynamics in glioma C6 cells. P2Y(2)R coupled with G-proteins, in response to ATP or UTP, regulates the level of phosphatidylinositol-4,5-bisphosphate (PIP(2)) which modulates a variety of actin binding proteins and is involved in calcium response and activates Rac1 and RhoA proteins. The RhoA/ROCK signaling pathway plays an important role in contractile force generation needed for the assembly of stress fibers, focal adhesions and for tail retraction during cell migration. Blocking of this pathway by a specific Rho-kinase inhibitor induces changes in F-actin organization and cell shape and decreases the level of phosphorylated myosin II and cofilin. In glioma C6 cells these changes are reversed after UTP stimulation of P2Y(2)R. Signaling pathways responsible for this compensation are connected with calcium signaling. Stimulation of the Rac1 mediated pathway via G(o) proteins needs additional interaction between α(v)β(5) integrins and P2Y(2)Rs. Rac1 activation is necessary for cofilin phosphorylation as well as integrin activation needed for focal complexes formation and stabilization of lamellipodium. Inhibition of positive Rac1 regulation prevents glioma C6 cells from recovery of control cell like morphology.
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23
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Ding Z, Bae YH, Roy P. Molecular insights on context-specific role of profilin-1 in cell migration. Cell Adh Migr 2012; 6:442-9. [PMID: 23076048 DOI: 10.4161/cam.21832] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Profilin-1 (Pfn1) is a ubiquitously expressed actin-monomer binding protein that has been linked to many cellular activities ranging from control of actin polymerization to gene transcription. Traditionally, Pfn1 has been considered to be an essential control element for actin polymerization and cell migration. Seemingly contrasting this view, a few recent studies have shown evidence of an inhibitory action of Pfn1 on motility of certain types of carcinoma cells. In this review, we summarize biochemistry and functional aspects of Pfn1 in normal cells and bring in newly emerged action of Pfn1 in cancer cells that may explain its context-specific role in cell migration.
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Affiliation(s)
- Zhijie Ding
- Department of Bioengineering, University of Pittsburgh, Pittsburgh, PA, USA
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24
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Huyck L, Van Troys M, Ampe C. Phosphosite conservation in single domain orthologs versus paralogs: a way to combine differential regulation with redundant core functions. FEBS Lett 2012; 586:296-302. [PMID: 22265693 DOI: 10.1016/j.febslet.2012.01.018] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 01/04/2012] [Accepted: 01/09/2012] [Indexed: 11/19/2022]
Abstract
Evolutionary conservation for structure function relations is commonly accepted. Here we hypothesize that closely related single domain paralogous proteins, having similar expression profiles and redundant biochemical core functions, additionally evolved to allow and maintain isoform specific differential regulation by single conserved amino acid substitutions. To substantiate this, we considered two families of closely related actin binding proteins combined with data mining of phosphorylated residues in human and mouse proteins. We show that such residues are identical in other orthologs whereas paralogs have a different, but also conserved, non-phosphorylatable residue at the equivalent positions.
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Affiliation(s)
- Lynn Huyck
- Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
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25
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Profilin1 regulates PI(3,4)P2 and lamellipodin accumulation at the leading edge thus influencing motility of MDA-MB-231 cells. Proc Natl Acad Sci U S A 2010; 107:21547-52. [PMID: 21115820 DOI: 10.1073/pnas.1002309107] [Citation(s) in RCA: 79] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Profilin1, a ubiquitously expressed actin-binding protein, plays a critical role in cell migration through actin cytoskeletal regulation. Given the traditional view of profilin1 as a promigratory molecule, it is difficult to reconcile observations that profilin1 is down-regulated in various invasive adenocarcinomas and that reduced profilin1 expression actually confers increased motility to certain adenocarcinoma cells. In this study, we show that profilin1 negatively regulates lamellipodin targeting to the leading edge in MDA-MB-231 breast cancer cells and normal cells; profilin1 depletion increases lamellipodin concentration at the lamellipodial tip (where it binds Ena/VASP), and this mediates the hypermotility. We report that the molecular mechanism underlying profilin1's modulation of lamellipodin localization relates to phosphoinositide control. Specifically, we show that phosphoinositide binding of profilin1 inhibits the motility of MDA-MB-231 cells by negatively regulating PI(3,4)P(2) at the membrane and thereby limiting recruitment of lamellipodin [a PI(3,4)P(2)-binding protein] and Ena/VASP to the leading edge. In summary, this study uncovers a unique biological consequence of profilin1-phosphoinositide interaction, thus providing direct evidence of profilin1's regulation of cell migration independent of its actin-related activity.
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26
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Pontrello CG, Ethell IM. Accelerators, Brakes, and Gears of Actin Dynamics in Dendritic Spines. ACTA ACUST UNITED AC 2009; 3:67-86. [PMID: 20463852 DOI: 10.2174/1874082000903020067] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Dendritic spines are actin-rich structures that accommodate the postsynaptic sites of most excitatory synapses in the brain. Although dendritic spines form and mature as synaptic connections develop, they remain plastic even in the adult brain, where they can rapidly grow, change, or collapse in response to normal physiological changes in synaptic activity that underlie learning and memory. Pathological stimuli can adversely affect dendritic spine shape and number, and this is seen in neurodegenerative disorders and some forms of mental retardation and autism as well. Many of the molecular signals that control these changes in dendritic spines act through the regulation of filamentous actin (F-actin), some through direct interaction with actin, and others via downstream effectors. For example, cortactin, cofilin, and gelsolin are actin-binding proteins that directly regulate actin dynamics in dendritic spines. Activities of these proteins are precisely regulated by intracellular signaling events that control their phosphorylation state and localization. In this review, we discuss how actin-regulating proteins maintain the balance between F-actin assembly and disassembly that is needed to stabilize mature dendritic spines, and how changes in their activities may lead to rapid remodeling of dendritic spines.
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Affiliation(s)
- Crystal G Pontrello
- Biomedical Sciences Division and Neuroscience program, University of California Riverside, USA
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Richer SM, Stewart NK, Webb SA, Tomaszewski JW, Oakley MG. High affinity binding to profilin by a covalently constrained, soluble mimic of phosphatidylinositol-4,5-bisphosphate micelles. ACS Chem Biol 2009; 4:733-9. [PMID: 19639958 DOI: 10.1021/cb900121r] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Phosphoinositide (PI) lipids are essential regulators of a wide variety of cellular functions. We present here the preparation of a multivalent analogue of a phosphatidylinositol-4,5-bisphosphate (PIP(2)) micelle containing only the polar headgroup portion of this lipid. We show that this dendrimer binds to the cytoskeletal protein profilin with an affinity indistinguishable from that of PIP(2), despite the fact that profilin discriminates between PIP(2) and its monomeric hydrolysis product inositol-1,4,5-triphosphate (IP(3)) under physiological conditions. These data demonstrate that the diacylglycerol (DAG) moiety of PIP(2) is not required for high-affinity binding and suggest that profilin uses multivalency as a key means to distinguish between the intact lipid and IP(3). The class of soluble membrane analogues described here is likely to have broad applicability in the study of protein.PI interactions.
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Affiliation(s)
- Sarah M. Richer
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - Nichole K. Stewart
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - Sarah A. Webb
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - John W. Tomaszewski
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
| | - Martha G. Oakley
- Department of Chemistry, Indiana University, 212 South Hawthorne Drive, Bloomington, Indiana 47405
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Krishnan K, Moens PDJ. Structure and functions of profilins. Biophys Rev 2009; 1:71-81. [PMID: 28509986 PMCID: PMC5425664 DOI: 10.1007/s12551-009-0010-y] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2009] [Revised: 05/07/2009] [Accepted: 05/13/2009] [Indexed: 10/20/2022] Open
Abstract
Profilins are small actin-binding proteins found in eukaryotes and certain viruses that are involved in cell development, cytokinesis, membrane trafficking, and cell motility. Originally identified as an actin sequestering/binding protein, profilin has been involved in actin polymerization dynamics. It catalyzes the exchange of ADP/ATP in actin and increases the rate of polymerization. Profilins also interact with polyphosphoinositides (PPI) and proline-rich domains containing proteins. Through its interaction with PPIs, profilin has been linked to signaling pathways between the cell membrane and the cytoskeleton, while its role in membrane trafficking has been associated with its interaction with proline-rich domain-containing proteins. Depending on the organism, profilin is present in a various number of isoforms. Four isoforms of profilin have been reported in higher organisms, while only one or two isoforms are expressed in single-cell organisms. The affinity of these isoforms for their ligands varies between isoforms and should therefore modulate their functions. However, the significance and the functions of the different isoforms are not yet fully understood. The structures of many profilin isoforms have been solved both in the presence and the absence of actin and poly-L-proline. These structural studies will greatly improve our understanding of the differences and similarities between the different profilins. Structural stability studies of different profilins are also shedding some light on our understanding of the profilin/ligand interactions. Profilin is a multifaceted protein for which a dramatic increase in potential functions has been found in recent years; as such, it has been implicated in a variety of physiological and pathological processes.
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Affiliation(s)
- Kannan Krishnan
- Centre for Bioactive Discovery in Health and Ageing, School of Science and Technology, University of New England, McClymont Bldg, Armidale, NSW, 2351, Australia
| | - Pierre D J Moens
- Centre for Bioactive Discovery in Health and Ageing, School of Science and Technology, University of New England, McClymont Bldg, Armidale, NSW, 2351, Australia.
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Key role of a PtdIns-4,5P2 micro domain in ionic regulation of the mammalian heart Na+/Ca2+ exchanger. Cell Calcium 2009; 45:546-53. [PMID: 19394081 DOI: 10.1016/j.ceca.2009.03.010] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2009] [Revised: 03/13/2009] [Accepted: 03/17/2009] [Indexed: 11/22/2022]
Abstract
Phosphatidylinositol biphosphate (PtdIns-4,5P(2)) plays a key role in the regulation of the mammalian heart Na(+)/Ca(2+) exchanger (NCX1) by protecting the intracellular Ca(2+) regulatory site against H(+)(i) and (H(+)(i)+Na(+)(i)) synergic inhibition. MgATP and MgATP-gamma-S up-regulation of NCX1 takes place via the production of this phosphoinositide. In microsomes containing PtdIns-4,5P(2) incubated in the absence of MgATP and at normal [Na(+)](i), alkalinization increases the affinity for Ca(2+)(i) to the values seen in the presence of the nucleotide at normal pH; under this condition, addition of MgATP does not increase the affinity for Ca(2+)(i) any further. On the other hand, prevention of Na(+)(i) inhibition by alkalinization in the absence of MgATP does not take place when the microsomes are depleted of PtdIns-4,5P(2). Experiments on NCX1-PtdIns-4,5P(2) cross-coimmunoprecipitation show that the relevant PtdIns-4,5P(2) is not the overall membrane component but specifically that tightly attached to NCX1. Consequently, the highest affinity of the Ca(2+)(i) regulatory site is seen in the deprotonated and PtdIns-4,5P(2)-bound NCX1. Confirming these results, a PtdIns-5-kinase also cross-coimmunoprecipitates with NCX1 without losing its functional competence. These observations indicate, for the first time, the existence of a PtdIns-5-kinase in the NCX1 microdomain.
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Kasina S, Rizwani W, Radhika KVN, Singh SS. Nitration of profilin effects its interaction with poly (L-proline) and actin. J Biochem 2009; 138:687-95. [PMID: 16428297 DOI: 10.1093/jb/mvi163] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Profilin from bovine spleen was nitrated with peroxynitrite; immunoblotting and spectrophotometric quantitation of nitrotyrosine residues suggested nitration of a single tyrosine residue in profilin with a stoichiometry of 0.6 mol of nitrotyrosine/mole of profilin. A decrease in the nitrotyrosine immunoreactivity of nitroprofilin during digestion with carboxypeptidase Y indicated that nitrotyrosine is located at the C-terminus of profilin. Nitroprofilin interaction with ligands such as phosphatidylinositol 4,5-bisphosphate, actin and poly (l-proline) was analyzed by monitoring the tryptophan fluorescence. Scatchard plot and binding isotherm data obtained revealed no significant difference in affinity of nitroprofilin to phosphatidylinositol 4,5-bisphosphate (K(d) of 4.8 +/- 0.5 muM for profilin, and K(d) of 5.7 +/- 0.6 muM for nitroprofilin), while poly (l-proline) binding studies revealed a twenty-fold increase in the affinity of profilin to poly (l-proline) upon nitration (K(d) of 21.8 +/- 1.7 muM for profilin, and K(d) of 1.1 +/- 0.1 muM for nitroprofilin). Actin polymerization studies involving pyrene-labeled actin indicated that profilin nitration inhibits the actin sequestering property of profilin. The critical actin monomer concentration (C(c)) was 150 and 250 nM in the presence of nitroprofilin and profilin, respectively. Thus, nitric oxide and free radicals produced under different conditions could alter the functions of profilin through nitration, such as its interaction with actin and poly (l-proline).
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Affiliation(s)
- S Kasina
- Hansen's Life Sciences Research Building, Department of Biological Sciences, Purdue University, West Lafayette, Indiana 47906, USA
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Kursula I, Kursula P, Ganter M, Panjikar S, Matuschewski K, Schüler H. Structural basis for parasite-specific functions of the divergent profilin of Plasmodium falciparum. Structure 2009; 16:1638-48. [PMID: 19000816 DOI: 10.1016/j.str.2008.09.008] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2008] [Revised: 09/05/2008] [Accepted: 09/05/2008] [Indexed: 11/30/2022]
Abstract
Profilins are key regulators of actin dynamics. They sequester actin monomers, forming a pool for rapid polymer formation stimulated by proteins such as formins. Apicomplexan parasites utilize a highly specialized microfilament system for motility and host cell invasion. Their genomes encode only a small number of divergent actin regulators. We present the first crystal structure of an apicomplexan profilin, that of the malaria parasite Plasmodium falciparum, alone and in complex with a polyproline ligand peptide. The most striking feature of Plasmodium profilin is a unique minidomain consisting of a large beta-hairpin extension common to all apicomplexan parasites, and an acidic loop specific for Plasmodium species. Reverse genetics in the rodent malaria model, Plasmodium berghei, suggests that profilin is essential for the invasive blood stages of the parasite. Together, our data establish the structural basis for understanding the functions of profilin in the malaria parasite.
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Affiliation(s)
- Inari Kursula
- Department of Biochemistry, University of Oulu, 90570 Oulu, Finland.
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Richer SM, Stewart NK, Tomaszewski JW, Stone MJ, Oakley MG. NMR Investigation of the Binding between Human Profilin I and Inositol 1,4,5-Triphosphate, the Soluble Headgroup of Phosphatidylinositol 4,5-Bisphosphate. Biochemistry 2008; 47:13455-62. [DOI: 10.1021/bi801535f] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Sarah M. Richer
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Nichole K. Stewart
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - John W. Tomaszewski
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Martin J. Stone
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
| | - Martha G. Oakley
- Department of Chemistry, Indiana University, 800 East Kirkwood Avenue, Bloomington, Indiana 47405, and Department of Biochemistry and Molecular Biology, Monash University, Wellington Road, Clayton, Victoria 3800, Australia
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Butler-Cole C, Wagner MJ, Da Silva M, Brown GD, Burke RD, Upton C. An ectromelia virus profilin homolog interacts with cellular tropomyosin and viral A-type inclusion protein. Virol J 2007; 4:76. [PMID: 17650322 PMCID: PMC1964790 DOI: 10.1186/1743-422x-4-76] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2007] [Accepted: 07/24/2007] [Indexed: 11/10/2022] Open
Abstract
Background Profilins are critical to cytoskeletal dynamics in eukaryotes; however, little is known about their viral counterparts. In this study, a poxviral profilin homolog, ectromelia virus strain Moscow gene 141 (ECTV-PH), was investigated by a variety of experimental and bioinformatics techniques to characterize its interactions with cellular and viral proteins. Results Profilin-like proteins are encoded by all orthopoxviruses sequenced to date, and share over 90% amino acid (aa) identity. Sequence comparisons show highest similarity to mammalian type 1 profilins; however, a conserved 3 aa deletion in mammalian type 3 and poxviral profilins suggests that these homologs may be more closely related. Structural analysis shows that ECTV-PH can be successfully modelled onto both the profilin 1 crystal structure and profilin 3 homology model, though few of the surface residues thought to be required for binding actin, poly(L-proline), and PIP2 are conserved. Immunoprecipitation and mass spectrometry identified two proteins that interact with ECTV-PH within infected cells: alpha-tropomyosin, a 38 kDa cellular actin-binding protein, and the 84 kDa product of vaccinia virus strain Western Reserve (VACV-WR) 148, which is the truncated VACV counterpart of the orthopoxvirus A-type inclusion (ATI) protein. Western and far-western blots demonstrated that the interaction with alpha-tropomyosin is direct, and immunofluorescence experiments suggest that ECTV-PH and alpha-tropomyosin may colocalize to structures that resemble actin tails and cellular protrusions. Sequence comparisons of the poxviral ATI proteins show that although full-length orthologs are only present in cowpox and ectromelia viruses, an ~ 700 aa truncated ATI protein is conserved in over 90% of sequenced orthopoxviruses. Immunofluorescence studies indicate that ECTV-PH localizes to cytoplasmic inclusion bodies formed by both truncated and full-length versions of the viral ATI protein. Furthermore, colocalization of ECTV-PH and truncated ATI protein to protrusions from the cell surface was observed. Conclusion These results suggest a role for ECTV-PH in intracellular transport of viral proteins or intercellular spread of the virus. Broader implications include better understanding of the virus-host relationship and mechanisms by which cells organize and control the actin cytoskeleton.
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Affiliation(s)
- Christine Butler-Cole
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Mary J Wagner
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Melissa Da Silva
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Gordon D Brown
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Robert D Burke
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
| | - Chris Upton
- Department of Biochemistry and Microbiology, University of Victoria, Victoria, BC V8W 3P6, Canada
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Mazzatti DJ, Pawelec G, Longdin R, Powell JR, Forsey RJ. SELDI-TOF-MS ProteinChip array profiling of T-cell clones propagated in long-term culture identifies human profilin-1 as a potential bio-marker of immunosenescence. Proteome Sci 2007; 5:7. [PMID: 17550585 PMCID: PMC1892543 DOI: 10.1186/1477-5956-5-7] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2007] [Accepted: 06/05/2007] [Indexed: 11/23/2022] Open
Abstract
Background The adaptive immune response requires waves of T-cell clonal expansion on contact with pathogen and elimination after clearance of the source of antigen. However, lifelong persistent infections with common viruses cause chronic antigenic stimulation which takes its toll on adaptive immunity in late life. Chronic antigenic stress results in deregulation of the T-cell response and accumulation of anergic cells. Longitudinal studies of the elderly show that this impacts on survival. Identifying the nature of the defects in chronically-stimulated T-cells and protein bio-markers of these dysfunctional cells would help to understand age-associated compromised T-cell function (immunosenescence) and facilitate the development of targeted intervention strategies. The purpose of this work was to use surface-enhanced laser desorption/ionization time-of-flight mass spectrometry (SELDI-TOF-MS) to analyse proteins associated with T-cell senescence in order to identify potential bio-markers. Clonal populations of T-cells isolated from elderly octogenarian and centenarian donors were grown in vitro until senescence, and early passage and late passage (pre-senescent) cells were analysed using SELDI-TOF-MS ProteinChip arrays. Results Discriminant analysis identified several protein or peptide peaks in the region of 14.5–16.5 kDa that were associated with T-cell clone senescence. Human profilin-1, a ubiquitous protein associated with actin remodelling and cellular motility was unambiguously identified. Altered expression of profilin-1 in senescent T-cell clones was confirmed by Western blot analysis. Conclusion Due to the proposed roles of profilin-1 in cellular survival, cytoskeleton remodelling, motility, and proliferation, it is hypothesised that differential expression of profilin-1 in ageing may contribute directly to immunosenescence.
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Affiliation(s)
| | - Graham Pawelec
- Zentrum für Medizinische Forschung, Universitätsklinikum Tübingen, Tübingen, Germany
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Abstract
Phosphoinositide phosphates (PIPs) correspond to phosphorylated derivatives of phosphatidylinositol (PI). Despite their relatively low abundance in the plasma membrane, PIPs play a crucial role as precursors of second messengers and are themselves important signaling and targeting molecules. Indeed, modulation of levels of PIPs affects, for example, cortical actin organization, membrane dynamics, and cell migration. The focus of this review is on selected interesting targets of PIPs. Those proteins that bind PIPs and are involved in regulation of actin assembly, actin membrane linkage, and actin contractility are discussed, as well as those that are involved in signaling, such as small GTPases, protein kinases, and phosphatases, or in regulation of membrane dynamics.
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Affiliation(s)
- Verena Niggli
- Department of Pathology, University of Bern, CH-3010 Bern, Switzerland.
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Peterman TK, Ohol YM, McReynolds LJ, Luna EJ. Patellin1, a novel Sec14-like protein, localizes to the cell plate and binds phosphoinositides. PLANT PHYSIOLOGY 2004; 136:3080-94; discussion 3001-2. [PMID: 15466235 PMCID: PMC523369 DOI: 10.1104/pp.104.045369] [Citation(s) in RCA: 100] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/29/2004] [Revised: 07/23/2004] [Accepted: 07/23/2004] [Indexed: 05/19/2023]
Abstract
Membrane trafficking is central to construction of the cell plate during plant cytokinesis. Consequently, a detailed understanding of the process depends on the characterization of molecules that function in the formation, transport, targeting, and fusion of membrane vesicles to the developing plate, as well as those that participate in its consolidation and maturation into a fully functional partition. Here we report the initial biochemical and functional characterization of patellin1 (PATL1), a novel cell-plate-associated protein that is related in sequence to proteins involved in membrane trafficking in other eukaryotes. Analysis of the Arabidopsis genome indicated that PATL1 is one of a small family of Arabidopsis proteins, characterized by a variable N-terminal domain followed by two domains found in other membrane-trafficking proteins (Sec14 and Golgi dynamics domains). Results from immunolocalization and biochemical fractionation studies suggested that PATL1 is recruited from the cytoplasm to the expanding and maturing cell plate. In vesicle-binding assays, PATL1 bound to specific phosphoinositides, important regulators of membrane trafficking, with a preference for phosphatidylinositol(5)P, phosphatidylinositol(4,5)P(2), and phosphatidylinositol(3)P. Taken together, these findings suggest a role for PATL1 in membrane-trafficking events associated with cell-plate expansion or maturation and point to the involvement of phosphoinositides in cell-plate biogenesis.
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Affiliation(s)
- T Kaye Peterman
- Department of Biological Sciences, Wellesley College, Wellesley, Massachusetts 02481, USA.
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Drøbak BK, Franklin-Tong VE, Staiger CJ. The role of the actin cytoskeleton in plant cell signaling. THE NEW PHYTOLOGIST 2004; 163:13-30. [PMID: 33873778 DOI: 10.1111/j.1469-8137.2004.01076.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
The plant actin cytoskeleton provides a dynamic cellular component which is involved in the maintenance of cell shape and structure. It has been demonstrated recently that the actin cytoskeleton and its associated elements provide a key target in many signaling events. In addition to acting as a target, the actin cytoskeleton can also act as a transducer of signal information. In this review we describe some newly discovered aspects of the roles of the actin cytoskeleton in plant cell signaling. In addition to a summary of the roles played by actin-binding proteins, we also briefly review the progress made in understanding how the actin cytoskeleton participates in the self-incompatibility response in pollen tubes. Finally, the emerging importance of the actin cytoskeleton in the perception and responses to stimuli such as gravity, touch and cold stress exposure are discussed. Contents I. Introduction - the actin cytoskeleton 13 II. Actin-binding proteins 14 III. The actin cytoskeleton as a target and mediator of plant cell signaling 20 IV. Summary and conclusion 25 References 25 Acknowledgements 25.
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Affiliation(s)
- B K Drøbak
- Cell Signaling Group, Department of Disease and Stress Biology, John Innes Centre, Norwich Research Park, Colney Lane, Norwich NR4 7UH, UK
| | - V E Franklin-Tong
- School of Biosciences, The University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
| | - C J Staiger
- Purdue Motility Group, Department of Biological Sciences, Purdue University, 333 Hansen Life Sciences Building, 201 S. University Street, West Lafayette, IN 47907-2064, USA
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Wittenmayer N, Jandrig B, Rothkegel M, Schlüter K, Arnold W, Haensch W, Scherneck S, Jockusch BM. Tumor suppressor activity of profilin requires a functional actin binding site. Mol Biol Cell 2004; 15:1600-8. [PMID: 14767055 PMCID: PMC379259 DOI: 10.1091/mbc.e03-12-0873] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Profilin 1 (PFN1) is a regulator of the microfilament system and is involved in various signaling pathways. It interacts with many cytoplasmic and nuclear ligands. The importance of PFN1 for human tissue differentiation has been demonstrated by the findings that human cancer cells, expressing conspicuously low PFN1 levels, adopt a nontumorigenic phenotype upon raising their PFN1 level. In the present study, we characterize the ligand binding site crucial for profilin's tumor suppressor activity. Starting with CAL51, a human breast cancer cell line highly tumorigenic in nude mice, we established stable clones that express PFN1 mutants differentially defective in ligand binding. Clones expressing PFN1 mutants with reduced binding to either poly-proline-stretch ligands or phosphatidyl-inositol-4,5-bisphosphate, but with a functional actin binding site, were normal in growth, adhesion, and anchorage dependence, with only a weak tendency to elicit tumors in nude mice, similar to controls expressing wild-type PFN1. In contrast, clones expressing a mutant with severely reduced capacity to bind actin still behaved like the parental CAL51 and were highly tumorigenic. We conclude that the actin binding site on profilin is instrumental for normal differentiation of human epithelia and the tumor suppressor function of PFN1.
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Affiliation(s)
- Nina Wittenmayer
- Cell Biology, Zoological Institute, Technical University of Braunschweig, D-38092 Braunschweig, Germany
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Casamayor A, Snyder M. Molecular dissection of a yeast septin: distinct domains are required for septin interaction, localization, and function. Mol Cell Biol 2003; 23:2762-77. [PMID: 12665577 PMCID: PMC152559 DOI: 10.1128/mcb.23.8.2762-2777.2003] [Citation(s) in RCA: 143] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The septins are a family of cytoskeletal proteins present in animal and fungal cells. They were first identified for their essential role in cytokinesis, but more recently, they have been found to play an important role in many cellular processes, including bud site selection, chitin deposition, cell compartmentalization, and exocytosis. Septin proteins self-associate into filamentous structures that, in yeast cells, form a cortical ring at the mother bud neck. Members of the septin family share common structural domains: a GTPase domain in the central region of the protein, a stretch of basic residues at the amino terminus, and a predicted coiled-coil domain at the carboxy terminus. We have studied the role of each domain in the Saccharomyces cerevisiae septin Cdc11 and found that the three domains are responsible for distinct and sometimes overlapping functions. All three domains are important for proper localization and function in cytokinesis and morphogenesis. The basic region was found to bind the phosphoinositides phosphatidylinositol 4-phosphate and phosphatidylinositol 5-phosphate. The coiled-coil domain is important for interaction with Cdc3 and Bem4. The GTPase domain is involved in Cdc11-septin interaction and targeting to the mother bud neck. Surprisingly, GTP binding appears to be dispensable for Cdc11 function, localization, and lipid binding. Thus, we find that septins are multifunctional proteins with specific domains involved in distinct molecular interactions required for assembly, localization, and function within the cell.
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Affiliation(s)
- Antonio Casamayor
- Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA
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40
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Skare P, Karlsson R. Evidence for two interaction regions for phosphatidylinositol(4,5)-bisphosphate on mammalian profilin I. FEBS Lett 2002; 522:119-24. [PMID: 12095630 DOI: 10.1016/s0014-5793(02)02913-7] [Citation(s) in RCA: 54] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The binding of phosphatidylinositol(4,5)-bisphosphate (PI(4,5)P(2)) to profilin at a region distinct from the actin interaction surface is demonstrated by experiments with covalently cross-linked profilin:beta-actin. The result is in agreement with observations made with several mutant profilins and provides strong evidence for two regions on mammalian profilin mediating electrostatic interaction with phosphatidylinositol lipids; one close to the binding site for poly(L-proline), and one partially overlapping with the actin-binding surface. Congruent with this, two plant profilins, which have a reduced number of positive amino acids in one of these regions, displayed a dramatically lower binding to PI(4,5)P(2) compared to human profilin I.
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Affiliation(s)
- Petra Skare
- Department of Cell Biology, Wenner Gren Institute, Stockholm University, Sweden
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Lambrechts A, Jonckheere V, Dewitte D, Vandekerckhove J, Ampe C. Mutational analysis of human profilin I reveals a second PI(4,5)-P2 binding site neighbouring the poly(L-proline) binding site. BMC BIOCHEMISTRY 2002; 3:12. [PMID: 12052260 PMCID: PMC116585 DOI: 10.1186/1471-2091-3-12] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/13/2002] [Accepted: 05/28/2002] [Indexed: 11/10/2022]
Abstract
BACKGROUND Profilin is a small cytoskeletal protein which interacts with actin, proline-rich proteins and phosphatidylinositol 4,5-bisphosphate (PI(4,5)-P2). Crystallography, NMR and mutagenesis of vertebrate profilins have revealed the amino acid residues that are responsible for the interactions with actin and poly(L-proline) peptides. Although Arg88 of human profilin I was shown to be involved in PI(4,5)-P2-binding, it was suggested that carboxy terminal basic residues may be involved as well. RESULTS Using site directed mutagenesis we have refined the PI(4,5)-P2 binding site of human profilin I. For each mutant we assessed the stability and studied the interactions with actin, a proline-rich peptide and PI(4,5)-P2 micelles. We identified at least two PI(4,5)-P2-binding regions in human profilin I. As expected, one region comprises Arg88 and overlaps with the actin binding site. The second region involves Arg136 in the carboxy terminal helix and neighbours the poly(L-proline) binding site. In addition, we show that adding a small protein tag to the carboxy terminus of profilin strongly reduces binding to poly(L-proline), suggesting local conformational changes of the carboxy terminal alpha-helix may have dramatic effects on ligand binding. CONCLUSIONS The involvement of the two terminal alpha-helices of profilin in ligand binding imposes important structural constraints upon the functions of this region. Our data suggest a model in which the competitive interactions between PI(4,5)-P2 and actin and PI(4,5)-P2 and poly(L-proline) regulate profilin functions.
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Affiliation(s)
- Anja Lambrechts
- Department of Medical Protein Research (VIB09), Flanders Interuniversity Institute of Biotechnology and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Veronique Jonckheere
- Department of Medical Protein Research (VIB09), Flanders Interuniversity Institute of Biotechnology and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Daisy Dewitte
- Department of Medical Protein Research (VIB09), Flanders Interuniversity Institute of Biotechnology and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Joel Vandekerckhove
- Department of Medical Protein Research (VIB09), Flanders Interuniversity Institute of Biotechnology and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
| | - Christophe Ampe
- Department of Medical Protein Research (VIB09), Flanders Interuniversity Institute of Biotechnology and Department of Biochemistry, Faculty of Medicine and Health Sciences, Ghent University, Ghent, Belgium
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Patterson CE, Lum H. Update on pulmonary edema: the role and regulation of endothelial barrier function. ENDOTHELIUM : JOURNAL OF ENDOTHELIAL CELL RESEARCH 2002; 8:75-105. [PMID: 11572478 DOI: 10.3109/10623320109165319] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Discovery of the pathophysiologic mechanisms leading to pulmonary edema and identification of effective strategies for prevention remain significant clinical concerns. Endothelial barrier function is a key component for maintenance of the integrity of the vascular boundary in the lung, particularly since the gas exchange surface area of the alveolar-capillary membrane is large. This review is focused on new insights in the pulmonary endothelial response to injury and recovery, reversible activation by edemagenic agents, and the biochemical/structural basis for regulation of endothelial barrier function. This information is discussed in the context of fundamental concepts of lung fluid balance and pulmonary function.
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Affiliation(s)
- C E Patterson
- Department of Medicine, Indiana University School of Medicine & Roudebush VA Med. Center, Indianapolis 46202, USA
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Kovar DR, Yang P, Sale WS, Drobak BK, Staiger CJ. Chlamydomonas reinhardtiiproduces a profilin with unusual biochemical properties. J Cell Sci 2001; 114:4293-305. [PMID: 11739661 DOI: 10.1242/jcs.114.23.4293] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
We report the characterization of a profilin orthologue from Chlamydomonas reinhardtii. CrPRF, probably the only profilin isoform, is present in both the cell body and flagella. Examination of vegetative and gametic cells by immunofluorescence microscopy using multiple fixation procedures also revealed enrichment of CrPRF at the anterior of the cell near the base of flagella and near the base of the fertilization tubule in mating type plus gametes. Purified, recombinant CrPRF binds to actin with a Kd value ∼10–7 and displaces nuclei in a live cell ‘nuclear displacement’ assay, consistent with profilin’s ability to bind G-actin in vivo. However, when compared with other profilin isoforms, CrPRF has a relatively low affinity for poly-L-proline and for phosphatidylinositol (4,5) bisphosphate micelles. Furthermore, and surprisingly, CrPRF inhibits exchange of adenine nucleotide on G-actin in a manner similar to human ADF or DNase I. Thus, we postulate that a primary role for CrPRF is to sequester actin in Chlamydomonas. The unusual biochemical properties of CrPRF offer a new opportunity to distinguish specific functions for profilin isoforms.
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Affiliation(s)
- D R Kovar
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907-1392, USA
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Ching TT, Lin HP, Yang CC, Oliveira M, Lu PJ, Chen CS. Specific binding of the C-terminal Src homology 2 domain of the p85alpha subunit of phosphoinositide 3-kinase to phosphatidylinositol 3,4,5-trisphosphate. Localization and engineering of the phosphoinositide-binding motif. J Biol Chem 2001; 276:43932-8. [PMID: 11555646 DOI: 10.1074/jbc.m105159200] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Phosphoinositide second messengers, generated from the action of phosphoinositide 3-kinase (PI3K), mediate an array of signaling pathways through the membrane recruitment and activation of downstream effector proteins. Although pleckstrin domains of many target proteins have been shown to bind phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) and/or phosphatidylinositol 3,4-bisphosphate (PI(3,4)P(2)) with high affinity, published data concerning the phosphoinositide binding specificity of Src homology 2 (SH2) domains remain conflicting. Using three independent assays, we demonstrated that the C-terminal (CT-)SH2 domain, but not the N-terminal SH2 domain, on the PI3K p85alpha subunit displayed discriminative affinity for PIP(3). However, the binding affinity diminished precipitously when the acyl chain of PIP(3) was shortened. In addition, evidence suggests that the charge density on the phosphoinositol ring represents a key factor in determining the phosphoinositide binding specificity of the CT-SH2 domain. In light of the largely shared structural features between PIP(3) and PI(4,5)P(2), we hypothesized that the PIP(3)-binding site on the CT-SH2 domain encompassed a sequence that recognized PI(4,5)P(2). Based on a consensus PI(4,5)P(2)-binding sequence (KXXXXXKXKK; K denotes Arg, Lys, and His), we proposed the sequence (18)RNKAENLLRGKR(29) as the PIP(3)-binding site. This binding motif was verified by using a synthetic peptide and site-directed mutagenesis. More importantly, neutral substitution of flanking Arg(18) and Arg(29) resulted in a switch of ligand specificity of the CT-SH2 domain to PI(4,5)P(2) and PI(3,4)P(2), respectively. Together with computer modeling, these mutagenesis data suggest a pseudosymmetrical relationship in the recognition of the phosphoinositol head group at the binding motif.
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Affiliation(s)
- T T Ching
- Division of Pharmaceutical Sciences, College of Pharmacy, University of Kentucky, Lexington, Kentucky 40536, USA
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Kovar DR, Drøbak BK, Collings DA, Staiger CJ. The characterization of ligand-specific maize (Zea mays) profilin mutants. Biochem J 2001; 358:49-57. [PMID: 11485551 PMCID: PMC1222031 DOI: 10.1042/0264-6021:3580049] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Profilins are low-molecular-mass (12-15 kDa) cytosolic proteins that are major regulators of actin assembly in all eukaryotic cells. In general, profilins from evolutionarily diverse organisms share the ability to bind to G-actin, poly-(L-proline) (PLP) and proline-rich proteins, and polyphosphoinositides. However, the functional importance of each of these interactions remains unclear and might differ between organisms. We investigated the importance of profilin's interaction with its various ligands in plant cells by characterizing four maize (Zea mays) profilin 5 (ZmPRO5) mutants that had single amino acid substitutions in the presumed sites of ligand interaction. Comparisons in vitro with wild-type ZmPRO5 showed that these mutations altered ligand association specifically. ZmPRO5-Y6F had a 3-fold increased affinity for PLP, ZmPRO5-Y6Q had a 5-fold decreased affinity for PLP, ZmPRO5-D8A had a 2-fold increased affinity for PtdIns(4,5)P(2) and ZmPRO5-K86A had a 35-fold decreased affinity for G-actin. When the profilins were microinjected into Tradescantia stamen hair cells, ZmPRO5-Y6F increased the rate of nuclear displacement in stamen hairs, whereas ZmPRO5-K86A decreased the rate. Mutants with a decreased affinity for PLP (ZmPRO5-Y6Q) or an enhanced affinity for PtdIns(4,5)P(2) (ZmPRO5-D8A) were not significantly different from wild-type ZmPRO5 in affecting nuclear position. These results indicate that plant profilin's association with G-actin is extremely important and further substantiate the simple model that profilin acts primarily as a G-actin-sequestering protein in plant cells. Furthermore, interaction with proline-rich binding partners might also contribute to regulating profilin's effect on actin assembly in plant cells.
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Affiliation(s)
- D R Kovar
- Department of Biological Sciences, Purdue University, West Lafayette, IN 47907, USA
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Gonzalez LC, Weis WI, Scheller RH. A novel snare N-terminal domain revealed by the crystal structure of Sec22b. J Biol Chem 2001; 276:24203-11. [PMID: 11309394 DOI: 10.1074/jbc.m101584200] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Intra-cellular membrane fusion is facilitated by the association of SNAREs from opposite membranes into stable alpha-helical bundles. Many SNAREs, in addition to their alpha-helical regions, contain N-terminal domains that likely have essential regulatory functions. To better understand this regulation, we have determined the 2.4-A crystal structure of the 130-amino acid N-terminal domain of mouse Sec22b (mSec22b), a SNARE involved in endoplasmic reticulum/Golgi membrane trafficking. The domain consists of a mixed alpha-helical/beta-sheet fold that resembles a circular permutation of the actin/poly-proline binding protein, profilin, and the GAF/PAS family of regulatory modules. The structure is distinct from the previously characterized N-terminal domain of syntaxin 1A, and, unlike syntaxin 1A, the N-terminal domain of mSec22b has no effect on the rate of SNARE assembly in vitro. An analysis of surface conserved residues reveals a potential protein interaction site. Key residues in this site are distinct in two mammalian Sec22 variants that lack SNARE domains. Finally, sequence analysis indicates that a similar domain is likely present in the endosomal/lysosomal SNARE VAMP7.
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Affiliation(s)
- L C Gonzalez
- Department of Molecular and Cellular Physiology, Howard Hughes Medical Institute and the Department of Structural Biology, Stanford University School of Medicine, Stanford, California 94305, USA
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Abstract
Reactive oxygen species (ROS) are generated at sites of inflammation and injury, and at low levels, ROS can function as signaling molecules participating as signaling intermediates in regulation of fundamental cell activities such as cell growth and cell adaptation responses, whereas at higher concentrations, ROS can cause cellular injury and death. The vascular endothelium, which regulates the passage of macromolecules and circulating cells from blood to tissues, is a major target of oxidant stress, playing a critical role in the pathophysiology of several vascular diseases and disorders. Specifically, oxidant stress increases vascular endothelial permeability and promotes leukocyte adhesion, which are coupled with alterations in endothelial signal transduction and redox-regulated transcription factors such as activator protein-1 and nuclear factor-kappaB. This review discusses recent findings on the cellular and molecular mechanisms by which ROS signal events leading to impairment of endothelial barrier function and promotion of leukocyte adhesion. Particular emphasis is placed on the regulation of cell-cell and cell-surface adhesion molecules, the actin cytoskeleton, key protein kinases, and signal transduction events.
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Affiliation(s)
- H Lum
- Department of Pharmacology, Rush Presbyterian St. Luke's Medical Center, 2242 W. Harrison St., Suite 260, Chicago, IL 60612, USA.
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Kim YS, Furman S, Sink H, VanBerkum MF. Calmodulin and profilin coregulate axon outgrowth in Drosophila. JOURNAL OF NEUROBIOLOGY 2001; 47:26-38. [PMID: 11257611 DOI: 10.1002/neu.1013] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Coordinated regulation of actin cytoskeletal dynamics is critical to growth cone movement. The intracellular molecules calmodulin and profilin actively regulate actin-based motility and participate in the signaling pathways used to steer growth cones. Here we show that in the developing Drosophila embryo, calmodulin and profilin convey complimentary information that is necessary for appropriate growth cone advance. Reducing calmodulin activity by expression of a dominant inhibitor (KA) stalls axon extension of pioneer neurons within the CNS, while a partial loss of profilin function decreases extension of motor axons in the periphery. Yet, surprisingly, when calmodulin and profilin are simultaneously reduced, the ability of both CNS pioneer axons and motor axons to extend beyond the choice points is restored. In the CNS, at the time when growth cones must decide whether to cross or not to cross the midline, a reduction in calmodulin and/or roundabout signaling causes axons to cross the midline inappropriately. These inappropriate crossings are suppressed when profilin activity is simultaneously reduced. Interestingly, the mutual suppression of calmodulin and profilin activity requires a minimal level of profilin. In KA combinations with profilin null alleles, defects in axon extension and midline guidance are synergistically enhanced rather than suppressed. Together, our data indicate that the growth cone must coordinate the activity of both calmodulin and profilin in order to advance past selected choice points, including those dictating midline crossovers.
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Affiliation(s)
- Y S Kim
- Department of Biological Sciences, Wayne State University, Detroit, MI 48202, USA
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Lu J, Pollard TD. Profilin binding to poly-L-proline and actin monomers along with ability to catalyze actin nucleotide exchange is required for viability of fission yeast. Mol Biol Cell 2001; 12:1161-75. [PMID: 11294914 PMCID: PMC32294 DOI: 10.1091/mbc.12.4.1161] [Citation(s) in RCA: 123] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
We tested the ability of 87 profilin point mutations to complement temperature-sensitive and null mutations of the single profilin gene of the fission yeast Schizosaccharomyces pombe. We compared the biochemical properties of 13 stable noncomplementing profilins with an equal number of complementing profilin mutants. A large quantitative database revealed the following: 1) in a profilin null background fission yeast grow normally with profilin mutations having >10% of wild-type affinity for actin or poly-L-proline, but lower affinity for either ligand is incompatible with life; 2) in the cdc3-124 profilin ts background, fission yeast function with profilin having only 2-5% wild-type affinity for actin or poly-L-proline; and 3) special mutations show that the ability of profilin to catalyze nucleotide exchange by actin is an essential function. Thus, poly-L-proline binding, actin binding, and actin nucleotide exchange are each independent requirements for profilin function in fission yeast.
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Affiliation(s)
- J Lu
- Graduate Program in Cellular and Molecular Medicine, Johns Hopkins Medical School, Baltimore, Maryland 21205, USA
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