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Skruzny M. The endocytic protein machinery as an actin-driven membrane-remodeling machine. Eur J Cell Biol 2022; 101:151267. [PMID: 35970066 DOI: 10.1016/j.ejcb.2022.151267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2022] [Revised: 08/02/2022] [Accepted: 08/02/2022] [Indexed: 12/14/2022] Open
Abstract
In clathrin-mediated endocytosis, a principal membrane trafficking route of all eukaryotic cells, forces are applied to invaginate the plasma membrane and form endocytic vesicles. These forces are provided by specific endocytic proteins and the polymerizing actin cytoskeleton. One of the best-studied endocytic systems is endocytosis in yeast, known for its simplicity, experimental amenability, and overall similarity to human endocytosis. Importantly, the yeast endocytic protein machinery generates and transmits tremendous force to bend the plasma membrane, making this system beneficial for mechanistic studies of cellular force-driven membrane reshaping. This review summarizes important protein players, molecular functions, applied forces, and open questions and perspectives of this robust, actin-powered membrane-remodeling protein machine.
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Affiliation(s)
- Michal Skruzny
- Cell Biology and Biophysics Unit, European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, 69117 Heidelberg, Germany.
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2
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Yeast as a Model to Understand Actin-Mediated Cellular Functions in Mammals-Illustrated with Four Actin Cytoskeleton Proteins. Cells 2020; 9:cells9030672. [PMID: 32164332 PMCID: PMC7140605 DOI: 10.3390/cells9030672] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 03/05/2020] [Accepted: 03/05/2020] [Indexed: 12/31/2022] Open
Abstract
The budding yeast Saccharomyces cerevisiae has an actin cytoskeleton that comprises a set of protein components analogous to those found in the actin cytoskeletons of higher eukaryotes. Furthermore, the actin cytoskeletons of S. cerevisiae and of higher eukaryotes have some similar physiological roles. The genetic tractability of budding yeast and the availability of a stable haploid cell type facilitates the application of molecular genetic approaches to assign functions to the various actin cytoskeleton components. This has provided information that is in general complementary to that provided by studies of the equivalent proteins of higher eukaryotes and hence has enabled a more complete view of the role of these proteins. Several human functional homologues of yeast actin effectors are implicated in diseases. A better understanding of the molecular mechanisms underpinning the functions of these proteins is critical to develop improved therapeutic strategies. In this article we chose as examples four evolutionarily conserved proteins that associate with the actin cytoskeleton: (1) yeast Hof1p/mammalian PSTPIP1, (2) yeast Rvs167p/mammalian BIN1, (3) yeast eEF1A/eEF1A1 and eEF1A2 and (4) yeast Yih1p/mammalian IMPACT. We compare the knowledge on the functions of these actin cytoskeleton-associated proteins that has arisen from studies of their homologues in yeast with information that has been obtained from in vivo studies using live animals or in vitro studies using cultured animal cell lines.
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Barger SR, James ML, Pellenz CD, Krendel M, Sirotkin V. Human myosin 1e tail but not motor domain replaces fission yeast Myo1 domains to support myosin-I function during endocytosis. Exp Cell Res 2019; 384:111625. [PMID: 31542284 DOI: 10.1016/j.yexcr.2019.111625] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2019] [Revised: 09/13/2019] [Accepted: 09/15/2019] [Indexed: 10/26/2022]
Abstract
In both unicellular and multicellular organisms, long-tailed class I myosins function in clathrin-mediated endocytosis. Myosin 1e (Myo1e) in vertebrates and Myo1 in fission yeast have similar domain organization, yet whether these proteins or their individual protein domains are functionally interchangeable remains unknown. In an effort to assess functional conservation of class I myosins, we tested whether human Myo1e could replace Myo1 in fission yeast Schizosaccharomyces pombe and found that it was unable to substitute for yeast Myo1. To determine if any individual protein domain is responsible for the inability of Myo1e to function in yeast, we created human-yeast myosin-I chimeras. By functionally testing these chimeric myosins in vivo, we concluded that the Myo1e motor domain is unable to function in yeast, even when combined with the yeast Myo1 tail and a full complement of yeast regulatory light chains. Conversely, the Myo1e tail, when attached to the yeast Myo1 motor domain, supports localization to endocytic actin patches and partially rescues the endocytosis defect in myo1Δ cells. Further dissection showed that both the TH1 and TH2-SH3 domains in the human Myo1e tail are required for localization and function of chimeric myosin-I at endocytic sites. Overall, this study provides insights into the role of individual myosin-I domains, expands the utility of fission yeast as a simple model system to study the effects of disease-associated MYO1E mutations, and supports a model of co-evolution between a myosin motor and its actin track.
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Affiliation(s)
- Sarah R Barger
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA
| | - Michael L James
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA
| | - Christopher D Pellenz
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA
| | - Mira Krendel
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA.
| | - Vladimir Sirotkin
- Department of Cell and Developmental Biology, State University of New York Upstate Medical University, Syracuse, NY, 13210, USA.
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4
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Molecular difference between WASP and N-WASP critical for chemotaxis of T-cells towards SDF-1α. Sci Rep 2015; 5:15031. [PMID: 26463123 PMCID: PMC4604493 DOI: 10.1038/srep15031] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/07/2015] [Accepted: 08/26/2015] [Indexed: 11/13/2022] Open
Abstract
Wiskott-Aldrich Syndrome protein (WASP) integrates cell signaling pathways to the actin cytoskeleton, which play a critical role in T-cell activation and migration. Hematopoietic cells express both WASP and neural-WASP (N-WASP) which share similar domain structure, yet WASP deficiency causes Wiskott-Aldrich syndrome, suggesting that N-WASP present in the cells is not able to carry out all the functions of WASP. We have identified a unique internal thirty amino acid region (I30) in WASP, which regulates its function in chemotaxis of Jurkat T-cells. Deletion of the I30 region altered the WASP’s closed conformation and impaired its ability to rescue the chemotactic defect of WASP-deficient (JurkatWKD) T-cells. Expression of N-WASP in JurkatWKD T-cells using WASP promoter restored the migration velocity without correcting the chemotactic defect. However, insertion of I30 region in N-WASP (N-WASP-I30) enabled N-WASP to rescue the chemotactic defect of JurkatWKD T-cells. N-WASP-I30-EGFP displayed a punctate localization in contrast to the predominant nuclear localization of N-WASP-EGFP. Thus, our study has demonstrated that the I30 region of WASP is critical for localization and chemotaxis. This suggests that N-WASP’s failure to compensate for WASP in rescuing chemotaxis could be due to the absence of this I30 region.
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Abstract
Pathogenic bacteria produce virulence factors called effectors, which are important components of the infection process. Effectors aid in pathogenesis by facilitating bacterial attachment, pathogen entry into or exit from the host cell, immunoevasion, and immunosuppression. Effectors also have the ability to subvert host cellular processes, such as hijacking cytoskeletal machinery or blocking protein translation. However, host cells possess an evolutionarily conserved innate immune response that can sense the pathogen through the activity of its effectors and mount a robust immune response. This “effector triggered immunity” (ETI) was first discovered in plants but recent evidence suggest that the process is also well conserved in metazoans. We will discuss salient points of the mechanism of ETI in metazoans from recent studies done in mammalian cells and invertebrate model hosts.
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Affiliation(s)
- Rajmohan Rajamuthiah
- a Division of Infectious Diseases; Rhode Island Hospital; Alpert Medical School of Brown University; Providence, RI USA
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6
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Jain N, Tan JH, Feng S, George B, Thanabalu T. X-linked thrombocytopenia causing mutations in WASP (L46P and A47D) impair T cell chemotaxis. J Biomed Sci 2014; 21:91. [PMID: 25200405 PMCID: PMC4266975 DOI: 10.1186/s12929-014-0091-1] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2013] [Accepted: 09/02/2014] [Indexed: 11/28/2022] Open
Abstract
Background Mutation in the Wiskott-Aldrich syndrome Protein (WASP) causes Wiskott-Aldrich syndrome (WAS), X-linked thrombocytopenia (XLT) and X-linked congenital neutropenia (XLN). The majority of missense mutations causing WAS and XLT are found in the WH1 (WASP Homology) domain of WASP, known to mediate interaction with WIP (WASP Interacting Protein) and CIB1 (Calcium and Integrin Binding). Results We analyzed two WASP missense mutants (L46P and A47D) causing XLT for their effects on T cell chemotaxis. Both mutants, WASPRL46P and WASPRA47D (S1-WASP shRNA resistant) expressed well in JurkatWASP-KD T cells (WASP knockdown), however expression of these two mutants did not rescue the chemotaxis defect of JurkatWASP-KD T cells towards SDF-1α. In addition JurkatWASP-KD T cells expressing these two WASP mutants were found to be defective in T cell polarization when stimulated with SDF-1α. WASP exists in a closed conformation in the presence of WIP, however both the mutants (WASPRL46P and WASPRA47D) were found to be in an open conformation as determined in the bi-molecular complementation assay. WASP protein undergoes proteolysis upon phosphorylation and this turnover of WASP is critical for T cell migration. Both the WASP mutants were found to be stable and have reduced tyrosine phosphorylation after stimulation with SDF-1α. Conclusion Thus our data suggest that missense mutations WASPRL46P or WASPRA47D affect the activity of WASP in T cell chemotaxis probably by affecting the turnover of the protein. Electronic supplementary material The online version of this article (doi:10.1186/s12929-014-0091-1) contains supplementary material, which is available to authorized users.
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Affiliation(s)
| | | | | | | | - Thirumaran Thanabalu
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Singapore.
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Wiskott-Aldrich Syndrome causing mutation, Pro373Ser restricts conformational changes essential for WASP activity in T-cells. Biochim Biophys Acta Mol Basis Dis 2014; 1842:623-34. [PMID: 24440360 DOI: 10.1016/j.bbadis.2014.01.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2013] [Revised: 01/04/2014] [Accepted: 01/08/2014] [Indexed: 11/22/2022]
Abstract
Wiskott-Aldrich Syndrome (WAS) is caused by mutations in Wiskott-Aldrich Syndrome Protein (WASP) and majority of the mutations are found in the WASP Homology 1 (WH1) domain which mediates interaction with WIP (WASP Interacting Protein), a WASP chaperone. Two point mutations together in the proline rich region (PRR) domain of WASP (S339Y/P373S) have been reported to cause WAS however the molecular defect has not been characterized. Expression of these mutants separately (WASPR(S339Y), WASPR(P373S)) or together (WASPR(SP/YS)) did not rescue the chemotaxis defect or membrane projection defect of Jurkat(WKD) T-cells (WASP knockdown). This is not due to the inability of WASP-PRR mutants to form functional WASP-WIP complex in growth rescue experiments in las17Δ yeast strain. Expression of WASPR(S339Y) but not WASPR(P373S) or WASPR(SP/YS) rescued the IL-2 expression defect of Jurkat(WKD) T-cells, suggesting that Pro373Ser mutation alone is sufficient to inhibit WASP functions in T-cell activation. The diffused localization of WASP-PRR mutants in activated Jurkat T-cells suggests that Ser339 and Pro373 are critical for WASP localization. WASP-PRR mutations either together or individually did not abolish interaction of WASP with sixteen WASP binding proteins including Hck, however they caused reduction in Hck mediated tyrosine phosphorylation of WASP which is critical for WASP activity. The auto-inhibitory conformation of WASP(P373S) mutant was not relieved by the binding of Toca-1 or Nck1. Thus, our results suggest that Pro373Ser mutation reduces Tyr291 phosphorylation and prevents conformational changes required for WASP activity in chemotaxis and T-cell activation. Thus Pro3373Ser is probably responsible for all the defects associated with WAS in the patients.
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Kaminska J, Spiess M, Stawiecka-Mirota M, Monkaityte R, Haguenauer-Tsapis R, Urban-Grimal D, Winsor B, Zoladek T. Yeast Rsp5 ubiquitin ligase affects the actin cytoskeleton in vivo and in vitro. Eur J Cell Biol 2011; 90:1016-28. [DOI: 10.1016/j.ejcb.2011.08.002] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2010] [Revised: 08/11/2011] [Accepted: 08/17/2011] [Indexed: 10/16/2022] Open
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Wong MH, Meng L, Rajmohan R, Yu S, Thanabalu T. Vrp1p-Las17p interaction is critical for actin patch polarization but is not essential for growth or fluid phase endocytosis in S. cerevisiae. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2010; 1803:1332-46. [PMID: 20816901 DOI: 10.1016/j.bbamcr.2010.08.013] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/06/2010] [Revised: 08/26/2010] [Accepted: 08/26/2010] [Indexed: 11/24/2022]
Abstract
Vrp1p (yeast WIP) forms a protein complex with Las17p (yeast WASP), however the physiological significance of the interaction has not been fully characterized. Vrp1p residues, (788)MPKPR(792) are essential for Vrp1p-Las17p interaction. While C-Vrp1p(364-817) complements all the defects of the vrp1Δ strain, C-Vrp1p(364-817)(5A) ((788)AAAAA(792)) does not complement any of the defects, due to its inability to localize to cortical patches. Targeting C-Vrp1p(364-817)(5A) to membranes using CAAX motif (C-Vrp1p(364-817)(5A)-CAAX) rescued the growth and endocytosis defect but not the actin patch polarization defect of vrp1Δ. Vrp1p can localize to cortical patches, either by binding to Las17p through LBD (Las17 Binding Domain, Vrp1p(760-817)) or independent of Las17p through residues in N-Vrp1p(1-364). Unlike Vrp1p, Vrp1p(5A) localizes poorly to cortical patches and complements all the defects of vrp1Δ strain except actin patch polarization at elevated temperature. N-Vrp1p(1-364) complements all the defects of vrp1Δ strain except the actin patch polarization defect while N-Vrp1p(1-364)-LBD fusion protein complements all the defects. Thus our results show that while both Vrp1p and Las17p are essential for many cellular processes, the two proteins do not necessarily have to bind to each other to carry out these cellular functions. However, Las17p-Vrp1p interaction is essential for actin patch polarization at elevated temperature.
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Affiliation(s)
- Ming Hwa Wong
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Republic of Singapore
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10
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Misra A, Rajmohan R, Lim RPZ, Bhattacharyya S, Thanabalu T. The mammalian verprolin, WIRE induces filopodia independent of N-WASP through IRSp53. Exp Cell Res 2010; 316:2810-24. [PMID: 20678498 DOI: 10.1016/j.yexcr.2010.07.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Revised: 07/23/2010] [Accepted: 07/24/2010] [Indexed: 10/19/2022]
Abstract
The mammalian verprolin family of proteins, WIP (WASP Interacting Protein), CR16 (Corticoid Regulated) and WIRE (WIp-RElated) regulate the actin cytoskeleton through WASP/N-WASP (Wiskott Aldrich Syndrome Protein and Neural-WASP). In order to characterize the WASP/N-WASP-independent function of WIRE, we screened and identified IRSp53 (Insulin Receptor Substrate) as a WIRE interacting protein. Expression of IRSp53 with WIRE in N-WASP(-/-) mouse fibroblast cells induced filopodia while co-expression of IRSp53 with WIP did not. The induction of filopodia is dependent on WIRE-IRSp53 interaction as mutation in the SH3 domain of IRSp53 abolished WIRE-IRSp53 interaction as well as the ability to induce filopodia. Similarly, the Verprolin (V)-domain of WIRE is critical for IRSp53-WIRE interaction and for filopodia formation. The interaction between WIRE and IRSp53 is regulated by Cdc42 as mutations which abolish Cdc42-IRSp53 interaction lead to loss of IRSp53-WIRE interaction as shown by pull down assay. The plasma membrane localization of IRSp53 is dependent on Cdc42 and WIRE. Expression of Cdc42(G12V) (active mutant) with WIRE-IRSp53 caused significant increase in the number of filopodia per cell. Thus our results show that Cdc42 regulates the activity of IRSp53 by regulating the IRSp53-WIRE interaction as well as localization of the complex to plasma membrane to generate filopodia.
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Affiliation(s)
- Ashish Misra
- School of Biological Sciences, Nanyang Technological University, Singapore, Republic of Singapore
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Rajmohan R, Wong MH, Meng L, Munn AL, Thanabalu T. Las17p-Vrp1p but not Las17p-Arp2/3 interaction is important for actin patch polarization in yeast. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2009; 1793:825-35. [PMID: 19272406 DOI: 10.1016/j.bbamcr.2009.02.012] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/08/2008] [Revised: 02/25/2009] [Accepted: 02/26/2009] [Indexed: 11/18/2022]
Abstract
The actin cytoskeleton plays a central role in many important cellular processes such as cell polarization, cell division and endocytosis. The dynamic changes to the actin cytoskeleton that accompany these processes are regulated by actin-associated proteins Wiskott-Aldrich Syndrome Protein (WASP) (known as Las17p in yeast) and WASP-Interacting Protein (WIP) (known as Vrp1p in yeast). Both yeast and human WASP bind to and stimulate the Arp2/3 complex which in turn nucleates assembly of actin monomers into filaments at polarized sites at the cortex. WASP-WIP interaction in yeast and humans are important for Arp2/3 complex stimulation in vitro. It has been proposed that these interactions are also important for polarized actin assembly in vivo. However, the redundancy of actin-associated proteins has made it difficult to test this hypothesis. We have identified two point mutations (L80T and H94L) in yeast WASP that in combination abolish WASP-WIP interaction in yeast. We also identify an N-terminal fragment of Las17p (N-Las17p1-368) able to interact with Vrp1p but not Arp2/3. Using these mutant and truncated forms of yeast WASP we provide novel evidence that WASP interaction with WIP is more important than interaction with Arp2/3 for polarized actin assembly and endocytosis in yeast.
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Affiliation(s)
- Rajamuthiah Rajmohan
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
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12
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Misra A, Lim RPZ, Wu Z, Thanabalu T. N-WASP plays a critical role in fibroblast adhesion and spreading. Biochem Biophys Res Commun 2007; 364:908-12. [PMID: 17963692 DOI: 10.1016/j.bbrc.2007.10.086] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2007] [Accepted: 10/17/2007] [Indexed: 11/16/2022]
Abstract
N-WASP (Neural Wiskott Aldrich Syndrome Protein) regulates actin polymerization by activating the Arp2/3 complex and promotes the formation of actin-rich structures such as filopodia. Such actin-rich structures play critical roles in cell adhesion and cell motility. Analysis of the adhesion properties of N-WASP+/+ and N-WASP-/- mouse embryonic fibroblasts to extracellular matrix proteins revealed that N-WASP is critical for cell adhesion to fibronectin. There was no significant difference in the localization of paxillin in the two cell lines, however the vinculin patches in WASP+/+ cells were thicker and more prominent than those in N-WASP-/- cells. The beta1 integrins in N-WASP+/+ cells were found in large clusters, while beta1 integrins were more dispersed in N-WASP-/- cells. The N-WASP-/- cells migrated more rapidly than N-WASP+/+ cells in a scratch migration assay. Thus, our data suggest that N-WASP deficiency leads to reduced adhesion to fibronectin and increased cell motility.
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Affiliation(s)
- Ashish Misra
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
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WASP-interacting protein (WIP): working in polymerisation and much more. Trends Cell Biol 2007; 17:555-62. [PMID: 17949983 DOI: 10.1016/j.tcb.2007.08.005] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2007] [Revised: 08/19/2007] [Accepted: 08/20/2007] [Indexed: 11/22/2022]
Abstract
The migration of cells and the movement of some intracellular pathogens, such as Shigella and Vaccinia, are dependent on the actin-based cytoskeleton. Many proteins are involved in regulating the dynamics of the actin-based microfilaments within cells and, among them, WASP and N-WASP have a significant role in the regulation of actin polymerisation. The activity and stability of WASP is regulated by its cellular partner WASP-interacting protein (WIP) during the formation of actin-rich structures, including the immune synapse, filopodia, lamellipodia, stress fibres and podosomes. Here, we review the role of WIP in regulating WASP function by stabilising WASP and shuttling WASP to areas of actin assembly in addition to reviewing the WASP-independent functions of WIP.
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Lim RPZ, Misra A, Wu Z, Thanabalu T. Analysis of conformational changes in WASP using a split YFP. Biochem Biophys Res Commun 2007; 362:1085-9. [PMID: 17825255 DOI: 10.1016/j.bbrc.2007.08.124] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2007] [Accepted: 08/21/2007] [Indexed: 11/21/2022]
Abstract
WASP (Wiskott-Aldrich syndrome protein) has been proposed to adopt a closed conformation (autoinhibited conformation) due to interaction between the carboxy terminal and the GTPase binding domain. Various WASP-interacting proteins have been suggested to relieve this autoinhibition. We have used the split YFP (Yellow Fluorescent Protein) to analyze the conformation of WASP. Saccharomyces cerevisiae cells expressing YFP1-154-WASP-YFP155-238 were found to exhibit YFP fluorescence while cells expressing of YFP1-154-WASP and WASP-YFP155-238 did not suggesting an intramolecular complementation of the YFP molecule. The fluorescence signal of YFP1-154-WASP-YFP155-238 was enhanced in the presence of WIP (WASP-interacting protein) however this is not due to the increased stability of YFP1-154-WASP-YFP155-238. Expression of Toca-1 and Nck1 reduced the YFP fluorescence from YFP1-154-WASP-YFP155-238 even in the presence of WIP suggesting that binding of Toca-1 or Nck1 altered the conformation of YFP1-154-WASP-YFP155-238. Thus both Nck1 and Toca-1 can relieve the autoinhibition of the WASP molecule.
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Affiliation(s)
- Rina Pei Zhi Lim
- School of Biological Sciences, Nanyang Technological University, 60 Nanyang Drive, Singapore 637551, Republic of Singapore
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15
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Dong X, Patino-Lopez G, Candotti F, Shaw S. Structure-function analysis of the WIP role in T cell receptor-stimulated NFAT activation: evidence that WIP-WASP dissociation is not required and that the WIP NH2 terminus is inhibitory. J Biol Chem 2007; 282:30303-10. [PMID: 17711847 PMCID: PMC2094122 DOI: 10.1074/jbc.m704972200] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
WASP and its binding partner WIP play important roles in T cells both in actin polymerization and in interleukin-2 transcription. Aberrations thereof contribute to the pathology of Wiskott-Aldrich syndrome (WAS). To directly evaluate the cooperativity of WIP and WASP in interleukin-2 transcription, we investigated how the WIP-WASP complex regulates NF-AT-mediated gene transcription. We developed an improved model system for analysis, using WIP and WASP cotransfection into Jurkat cells, in which strong induction of NFAT reporter activation is observed with anti-T cell receptor (TCR) antibody without the phorbol 12-myristate 13-acetate usually used previously. Using this system, our findings contradict a prevailing conceptual model of TCR-induced WIP-WASP dissociation by showing in three ways that the WIP-WASP complex mediates TCR-induced NFAT activation without dissociation. First, phosphorylation of WIP Ser(488) does not cause dissociation of the WIP-WASP complex. Second, WIP-WASP complexes do not dissociate demonstrably after TCR stimulation. Third, a fusion protein of WIP to WASP efficiently mediates NFAT activation. Next, our studies clarify that WIP stabilization of WASP explains otherwise unexpected results in TCR-induced NFAT activation. Finally, we find that the NH(2) terminus of WIP is a highly inhibitory region for TCR-mediated transcriptional activation in which at least two elements contribute: the NH(2)-terminal polyproline and the NH(2)-terminal actin-binding WH2 domain. This suggests that WIP, like WASP, is subject to autoinhibition. Our data indicate that the WIP-WASP complex plays an important role in WASP stabilization and NFAT activation.
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Affiliation(s)
- Xiaoyun Dong
- Experimental Immunology Branch, National Cancer Institute, Bethesda, MD, USA
| | - Genaro Patino-Lopez
- Experimental Immunology Branch, National Cancer Institute, Bethesda, MD, USA
| | - Fabio Candotti
- Genetics and Molecular Biology Branch, National Human Genome Research Institute, Bethesda, MD 20892
| | - Stephen Shaw
- Experimental Immunology Branch, National Cancer Institute, Bethesda, MD, USA
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Abstract
This review summarizes what is known about the biochemical and biophysical mechanisms that initiate the assembly of actin filaments in cells. Assembly and disassembly of these filaments contribute to many types of cellular movements. Numerous proteins regulate actin assembly, but Arp2/3 complex and formins are the focus of this review because more is known about them than other proteins that stimulate the formation of new filaments. Arp2/3 complex is active at the leading edge of motile cells, where it produces branches on the sides of existing filaments. Growth of these filaments produces force to protrude the membrane. Crystal structures, reconstructions from electron micrographs, and biophysical experiments have started to map out the steps through which proteins called nucleation-promoting factors stimulate the formation of branches. Formins nucleate and support the elongation of unbranched actin filaments for cytokinesis and various types of actin filament bundles. Formins associate processively with the fast-growing ends of filaments and protect them from capping.
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Affiliation(s)
- Thomas D Pollard
- Department of Molecular, Cellular, and Developmental Biology, Yale University, New Haven, Connecticut 06520-8103, USA.
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17
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Thanabalu T, Rajmohan R, Meng L, Ren G, Vajjhala PR, Munn AL. Verprolin function in endocytosis and actin organization. FEBS J 2007; 274:4103-25. [PMID: 17635585 DOI: 10.1111/j.1742-4658.2007.05936.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Vrp1p (verprolin, End5p) is the yeast ortholog of human Wiskott-Aldrich syndrome protein (WASP)-interacting protein (WIP). Vrp1p localizes to the cortical actin cytoskeleton, is necessary for its polarization to sites of growth and is also essential for endocytosis. At elevated temperature, Vrp1p becomes essential for growth. A C-terminal Vrp1p fragment (C-Vrp1p) retains the ability to localize to the cortical actin cytoskeleton and function in actin-cytoskeleton polarization, endocytosis and growth. Here, we demonstrate that two submodules in C-Vrp1p are required for actin-cytoskeleton polarization: a novel C-terminal actin-binding submodule (CABS) that contains a novel G-actin-binding domain, which we call a verprolin homology 2 C-terminal (VH2-C) domain; and a second submodule comprising the Las17p-binding domain (LBD) that binds Las17p (yeast WASP). The LBD localizes C-Vrp1p to membranes and the cortical actin cytoskeleton. Intriguingly, the LBD is sufficient to restore endocytosis and growth at elevated temperature to Vrp1p-deficient cells. The CABS also restores these functions, but only if modified by a lipid anchor to provide membrane association. Our findings highlight the role of Las17p binding for Vrp1p membrane association, suggest general membrane association may be more important than specific targeting to the cortical actin cytoskeleton for Vrp1p function in endocytosis and cell growth, and suggest that Vrp1p binding to individual effectors may alter their physiological activity.
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Affiliation(s)
- Thirumaran Thanabalu
- Institute of Molecular and Cell Biology, A*STAR Biomedical Science Institutes, Singapore
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Meng L, Rajmohan R, Yu S, Thanabalu T. Actin binding and proline rich motifs of CR16 play redundant role in growth of vrp1Delta cells. Biochem Biophys Res Commun 2007; 357:289-94. [PMID: 17418095 DOI: 10.1016/j.bbrc.2007.03.144] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2007] [Accepted: 03/22/2007] [Indexed: 11/20/2022]
Abstract
CR16, (Glucocorticoid-regulated) belongs to the verprolin family of proteins which are characterized by the presence of a V domain (verprolin) at the N-terminal. Expression of CR16 suppressed the growth and endocytosis defect of vrp1Delta strain without correcting the actin patch polarization defect. The V domain of CR16 is critical for suppression of the growth defect of vrp1Delta strain but not for localisation to cortical actin patches. Mutations in the actin binding motif alone did not abolish the activity of CR16 but the mutations in combination with deletion of N-terminal proline rich motif abolished the ability of CR16 to suppress the growth defect. This suggests that the V domain of CR16 has two functionally redundant motifs and either one of these motifs is sufficient for suppressing the growth defect of vrp1Delta strain. This is in contrast to the observation that both WIP and WIRE require the actin binding motif for their activity.
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Affiliation(s)
- Lei Meng
- School of Biological Sciences, Nanyang Technological University, Singapore 637551, Republic of Singapore
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Current awareness on yeast. Yeast 2006. [DOI: 10.1002/yea.1318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
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