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Williquett J, Allamargot C, Sun H. AMPK-SP1-Guided Dynein Expression Represents a New Energy-Responsive Mechanism and Therapeutic Target for Diabetic Nephropathy. KIDNEY360 2024; 5:538-549. [PMID: 38467599 PMCID: PMC11093544 DOI: 10.34067/kid.0000000000000392] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/11/2023] [Accepted: 02/05/2024] [Indexed: 03/13/2024]
Abstract
Key Points AMP kinase senses diabetic stresses in podocytes, subsequently upregulates specificity protein 1–mediated dynein expression and promotes podocyte injury. Pharmaceutical restoration of dynein expression by targeting specificity protein 1 represents an innovative therapeutic strategy for diabetic nephropathy. Background Diabetic nephropathy (DN) is a major complication of diabetes. Injury to podocytes, epithelial cells that form the molecular sieve of a kidney, is a preclinical feature of DN. Protein trafficking mediated by dynein, a motor protein complex, is a newly recognized pathophysiology of diabetic podocytopathy and is believed to be derived from the hyperglycemia-induced expression of subunits crucial for the transportation activity of the dynein complex. However, the mechanism underlying this transcriptional signature remains unknown. Methods Through promoter analysis, we identified binding sites for transcription factor specificity protein 1 (SP1) as the most shared motif among hyperglycemia-responsive dynein genes. We demonstrated the essential role of AMP-activated protein kinase (AMPK)–regulated SP1 in the transcription of dynein subunits and dynein-mediated trafficking in diabetic podocytopathy using chromatin immunoprecipitation quantitative PCR and live cell imaging. SP1-dependent dynein-driven pathogenesis of diabetic podocytopathy was demonstrated by pharmaceutical intervention with SP1 in a mouse model of streptozotocin-induced diabetes. Results Hyperglycemic conditions enhance SP1 binding to dynein promoters, promoted dynein expression, and enhanced dynein-mediated mistrafficking in cultured podocytes. These changes can be rescued by chemical inhibition or genetic silencing of SP1. The direct repression of AMPK, an energy sensor, replicates hyperglycemia-induced dynein expression by activating SP1. Mithramycin inhibition of SP1-directed dynein expression in streptozotocin-induced diabetic mice protected them from developing podocytopathy and prevented DN progression. Conclusions Our work implicates AMPK-SP1–regulated dynein expression as an early mechanism that translates energy disturbances in diabetes into podocyte dysfunction. Pharmaceutical restoration of dynein expression by targeting SP1 offers a new therapeutic strategy to prevent DN.
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Affiliation(s)
- Jillian Williquett
- Division of Nephrology, Stead Family Department of Pediatrics, The University of Iowa, Iowa City, Iowa
- Carver College of Medicine, The University of Iowa, Iowa City, Iowa
| | - Chantal Allamargot
- Central Microscopy Research Facility, The University of Iowa, Iowa City, Iowa
| | - Hua Sun
- Division of Nephrology, Stead Family Department of Pediatrics, The University of Iowa, Iowa City, Iowa
- Carver College of Medicine, The University of Iowa, Iowa City, Iowa
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Wang Y, Liao G, Wu Y, Wang R, Tang DD. The intermediate filament protein nestin serves as a molecular hub for smooth muscle cytoskeletal signaling. Respir Res 2023; 24:157. [PMID: 37316833 DOI: 10.1186/s12931-023-02473-8] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2023] [Accepted: 06/08/2023] [Indexed: 06/16/2023] Open
Abstract
BACKGROUND The recruitment of the actin-regulatory proteins cortactin and profilin-1 (Pfn-1) to the membrane is important for the regulation of actin cytoskeletal reorganization and smooth muscle contraction. Polo-like kinase 1 (Plk1) and the type III intermediate filament protein vimentin are involved in smooth muscle contraction. Regulation of complex cytoskeletal signaling is not entirely elucidated. The aim of this study was to evaluate the role of nestin (a type VI intermediate filament protein) in cytoskeletal signaling in airway smooth muscle. METHODS Nestin expression in human airway smooth muscle (HASM) was knocked down by specific shRNA or siRNA. The effects of nestin knockdown (KD) on the recruitment of cortactin and Pfn-1, actin polymerization, myosin light chain (MLC) phosphorylation, and contraction were evaluated by cellular and physiological approaches. Moreover, we assessed the effects of non-phosphorylatable nestin mutant on these biological processes. RESULTS Nestin KD reduced the recruitment of cortactin and Pfn-1, actin polymerization, and HASM contraction without affecting MLC phosphorylation. Moreover, contractile stimulation enhanced nestin phosphorylation at Thr-315 and the interaction of nestin with Plk1. Nestin KD also diminished phosphorylation of Plk1 and vimentin. The expression of T315A nestin mutant (alanine substitution at Thr-315) reduced the recruitment of cortactin and Pfn-1, actin polymerization, and HASM contraction without affecting MLC phosphorylation. Furthermore, Plk1 KD diminished nestin phosphorylation at this residue. CONCLUSIONS Nestin is an essential macromolecule that regulates actin cytoskeletal signaling via Plk1 in smooth muscle. Plk1 and nestin form an activation loop during contractile stimulation.
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Affiliation(s)
- Yinna Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA
| | - Guoning Liao
- Department of Molecular and Cellular Physiology, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA
| | - Yidi Wu
- Department of Molecular and Cellular Physiology, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA
| | - Ruping Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA
| | - Dale D Tang
- Department of Molecular and Cellular Physiology, Albany Medical College, 47 New Scotland Avenue, MC-8, Albany, NY, 12208, USA.
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Wang R, Khan S, Liao G, Wu Y, Tang DD. Nestin Modulates Airway Smooth Muscle Cell Migration by Affecting Spatial Rearrangement of Vimentin Network and Focal Adhesion Assembly. Cells 2022; 11:cells11193047. [PMID: 36231009 PMCID: PMC9562664 DOI: 10.3390/cells11193047] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2022] [Revised: 09/26/2022] [Accepted: 09/27/2022] [Indexed: 11/16/2022] Open
Abstract
Airway smooth muscle cell migration plays a role in the progression of airway remodeling, a hallmark of allergic asthma. However, the mechanisms that regulate cell migration are not yet entirely understood. Nestin is a class VI intermediate filament protein that is involved in the proliferation/regeneration of neurons, cancer cells, and skeletal muscle. Its role in cell migration is not fully understood. Here, nestin knockdown (KD) inhibited the migration of human airway smooth muscle cells. Using confocal microscopy and the Imaris software, we found that nestin KD attenuated focal adhesion sizes during cell spreading. Moreover, polo-like kinase 1 (Plk1) and vimentin phosphorylation at Ser-56 have been previously shown to affect focal adhesion assembly. Here, nestin KD reduced Plk1 phosphorylation at Thr-210 (an indication of Plk1 activation), vimentin phosphorylation at Ser-56, the contacts of vimentin filaments to paxillin, and the morphology of focal adhesions. Moreover, the expression of vimentin phosphorylation-mimic mutant S56D (aspartic acid substitution at Ser-56) rescued the migration, vimentin reorganization, and focal adhesion size of nestin KD cells. Together, our results suggest that nestin promotes smooth muscle cell migration. Mechanistically, nestin regulates Plk1 phosphorylation, which mediates vimenitn phosphorylation, the connection of vimentin filaments with paxillin, and focal adhesion assembly.
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Affiliation(s)
| | | | | | | | - Dale D. Tang
- Correspondence: ; Tel.: +1-(518)-262-6416; Fax: +1-(518)-262-8101
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Current Understanding of Asthma Pathogenesis and Biomarkers. Cells 2022; 11:cells11172764. [PMID: 36078171 PMCID: PMC9454904 DOI: 10.3390/cells11172764] [Citation(s) in RCA: 62] [Impact Index Per Article: 31.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2022] [Revised: 08/24/2022] [Accepted: 09/01/2022] [Indexed: 11/17/2022] Open
Abstract
Asthma is a heterogeneous lung disease with variable phenotypes (clinical presentations) and distinctive endotypes (mechanisms). Over the last decade, considerable efforts have been made to dissect the cellular and molecular mechanisms of asthma. Aberrant T helper type 2 (Th2) inflammation is the most important pathological process for asthma, which is mediated by Th2 cytokines, such as interleukin (IL)-5, IL-4, and IL-13. Approximately 50% of mild-to-moderate asthma and a large portion of severe asthma is induced by Th2-dependent inflammation. Th2-low asthma can be mediated by non-Th2 cytokines, including IL-17 and tumor necrosis factor-α. There is emerging evidence to demonstrate that inflammation-independent processes also contribute to asthma pathogenesis. Protein kinases, adapter protein, microRNAs, ORMDL3, and gasdermin B are newly identified molecules that drive asthma progression, independent of inflammation. Eosinophils, IgE, fractional exhaled nitric oxide, and periostin are practical biomarkers for Th2-high asthma. Sputum neutrophils are easily used to diagnose Th2-low asthma. Despite progress, more studies are needed to delineate complex endotypes of asthma and to identify new and practical biomarkers for better diagnosis, classification, and treatment.
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Wang R, Wang Y, Liao G, Chen B, Panettieri RA, Penn RB, Tang DD. Abi1 mediates airway smooth muscle cell proliferation and airway remodeling via Jak2/STAT3 signaling. iScience 2022; 25:103833. [PMID: 35198891 PMCID: PMC8851273 DOI: 10.1016/j.isci.2022.103833] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2021] [Revised: 12/10/2021] [Accepted: 01/21/2022] [Indexed: 11/05/2022] Open
Abstract
Asthma is a complex pulmonary disorder with multiple pathological mechanisms. A key pathological feature of chronic asthma is airway remodeling, which is largely attributed to airway smooth muscle (ASM) hyperplasia that contributes to thickening of the airway wall and further drives asthma pathology. The cellular processes that mediate ASM cell proliferation are not completely elucidated. Using multiple approaches, we demonstrate that the adapter protein Abi1 (Abelson interactor 1) is upregulated in ∼50% of ASM cell cultures derived from patients with asthma. Loss-of-function studies demonstrate that Abi1 regulates the activation of Jak2 (Janus kinase 2) and STAT3 (signal transducers and activators of transcription 3) as well as the proliferation of both nonasthmatic and asthmatic human ASM cell cultures. These findings identify Abi1 as a molecular switch that activates Jak2 kinase and STAT3 in ASM cells and demonstrate that a dysfunctional Abi1-associated pathway contributes to the progression of asthma.
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Affiliation(s)
- Ruping Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY 12208, USA
| | - Yinna Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY 12208, USA
| | - Guoning Liao
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY 12208, USA
| | - Bohao Chen
- Department of Medicine, University of Chicago, Chicago, IL 60637, USA
| | - Reynold A. Panettieri
- Department of Medicine, Rutgers Institute for Translational Medicine and Science, Robert Wood Johnson School of Medicine, New Brunswick, NJ 08901, USA
| | - Raymond B. Penn
- Department of Medicine, Center for Translational Medicine, Thomas Jefferson University, Philadelphia, PA 19107, USA
| | - Dale D. Tang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, NY 12208, USA
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Liao G, Wang R, Tang DD. Plk1 Regulates Caspase-9 Phosphorylation at Ser-196 and Apoptosis of Human Airway Smooth Muscle Cells. Am J Respir Cell Mol Biol 2022; 66:223-234. [PMID: 34705620 PMCID: PMC8845127 DOI: 10.1165/rcmb.2021-0192oc] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2021] [Accepted: 10/21/2021] [Indexed: 11/24/2022] Open
Abstract
Airway smooth muscle thickening, a key characteristic of chronic asthma, is largely attributed to increased smooth muscle cell proliferation and reduced smooth muscle apoptosis. Polo-like kinase 1 (Plk1) is a serine/threonine protein kinase that participates in the pathogenesis of airway smooth muscle remodeling. Although the role of Plk1 in cell proliferation and migration is recognized, its function in smooth muscle apoptosis has not been previously investigated. Caspase-9 (Casp9) is a key enzyme that participates in the execution of apoptosis. Casp9 phosphorylation at Ser-196 and Thr-125 is implicated in regulating its activity in cancer cells and epithelial cells. Here, exposure of human airway smooth muscle (HASM) cells to platelet-derived growth factorfor 24 hours enhanced the expression of Plk1 and Casp9 phosphorylation at Ser-196, but not Thr-125. Overexpression of Plk1 in HASM cells increased Casp9 phosphorylation at Ser-196. Moreover, the expression of Plk1 increased the levels of pro-Casp9 and pro-Casp3 and inhibited apoptosis, demonstrating a role of Plk1 in inhibiting apoptosis. Knockdown of Plk1 reduced Casp9 phosphorylation at Ser-196, reduced pro-Casp9/3 expression, and increased apoptosis. Furthermore, Casp9 phosphorylation at Ser-196 was upregulated in asthmatic HASM cells, which was associated with increased Plk1 expression. Knockdown of Plk1 in asthmatic HASM cells decreased Casp9 phosphorylation at Ser-196 and enhanced apoptosis. Together, these studies disclose a previously unknown mechanism that the Plk1-Casp9/3 pathway participates in the controlling of smooth muscle apoptosis.
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Affiliation(s)
- Guoning Liao
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
| | - Ruping Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
| | - Dale D Tang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
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Wang F, Hou W, Chitsike L, Xu Y, Bettler C, Perera A, Bank T, Cotler SJ, Dhanarajan A, Denning MF, Ding X, Breslin P, Qiang W, Li J, Koleske AJ, Qiu W. ABL1, Overexpressed in Hepatocellular Carcinomas, Regulates Expression of NOTCH1 and Promotes Development of Liver Tumors in Mice. Gastroenterology 2020; 159:289-305.e16. [PMID: 32171747 PMCID: PMC7387191 DOI: 10.1053/j.gastro.2020.03.013] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 01/31/2020] [Accepted: 03/04/2020] [Indexed: 02/08/2023]
Abstract
BACKGROUND & AIMS We investigated whether ABL proto-oncogene 1, non-receptor tyrosine kinase (ABL1) is involved in development of hepatocellular carcinoma (HCC). METHODS We analyzed clinical and gene expression data from The Cancer Genome Atlas. Albumin-Cre (HepWT) mice and mice with hepatocyte-specific disruption of Abl1 (HepAbl-/- mice) were given hydrodynamic injections of plasmids encoding the Sleeping Beauty transposase and transposons with the MET gene and a catenin β1 gene with an N-terminal truncation, which induces development of liver tumors. Some mice were then gavaged with the ABL1 inhibitor nilotinib or vehicle (control) daily for 4 weeks. We knocked down ABL1 with short hairpin RNAs in Hep3B and Huh7 HCC cells and analyzed their proliferation and growth as xenograft tumors in mice. We performed RNA sequencing and gene set enrichment analysis of tumors. We knocked down or overexpressed NOTCH1 and MYC in HCC cells and analyzed proliferation. We measured levels of phosphorylated ABL1, MYC, and NOTCH1 by immunohistochemical analysis of an HCC tissue microarray. RESULTS HCC tissues had higher levels of ABL1 than non-tumor liver tissues, which correlated with shorter survival times of patients. HepWT mice with the MET and catenin β1 transposons developed liver tumors and survived a median 64 days; HepAbl-/- mice with these transposons developed tumors that were 50% smaller and survived a median 81 days. Knockdown of ABL1 in human HCC cells reduced proliferation, growth as xenograft tumors in mice, and expression of MYC, which reduced expression of NOTCH1. Knockdown of NOTCH1 or MYC in HCC cells significantly reduced cell growth. NOTCH1 or MYC overexpression in human HCC cells promoted proliferation and rescued the phenotype caused by ABL1 knockdown. The level of phosphorylated (activated) ABL1 correlated with levels of MYC and NOTCH1 in human HCC specimens. Nilotinib decreased expression of MYC and NOTCH1 in HCC cell lines, reduced the growth of xenograft tumors in mice, and slowed growth of liver tumors in mice with MET and catenin β1 transposons, reducing tumor levels of MYC and NOTCH1. CONCLUSIONS HCC samples have increased levels of ABL1 compared with nontumor liver tissues, and increased levels of ABL1 correlate with shorter survival times of patients. Loss or inhibition of ABL1 reduces proliferation of HCC cells and slows growth of liver tumors in mice. Inhibitors of ABL1 might be used for treatment of HCC.
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Affiliation(s)
- Fang Wang
- Departments of Surgery and Cancer Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Wei Hou
- Departments of Surgery and Cancer Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Lennox Chitsike
- Departments of Surgery and Cancer Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Yingchen Xu
- Department of General Surgery, Beijing Tongren Hospital, Capital Medical University
| | - Carlee Bettler
- Departments of Surgery and Cancer Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Aldeb Perera
- Departments of Surgery and Cancer Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Thomas Bank
- Departments of Surgery and Cancer Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Scott J. Cotler
- Department of Medicine, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Asha Dhanarajan
- Department of Pathology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Mitchell F. Denning
- Department of Pathology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Xianzhong Ding
- Department of Pathology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Peter Breslin
- Departments of Molecular/Cellular Physiology and Oncology Institute, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA,Department of Biology, Loyola University Chicago Stritch School of Medicine, 2160 South 1st Avenue., Maywood, IL 60153, USA
| | - Wenan Qiang
- Department of Obstetrics and Gynecology and Pathology, Northwestern University
| | - Jun Li
- Department of Applied and Computational Mathematics and Statistics, University of Notre Dame
| | | | - Wei Qiu
- Department of Surgery, Loyola University Chicago Stritch School of Medicine, Chicago, Illinois; Department of Cancer Biology, Loyola University Chicago Stritch School of Medicine, Chicago, Illinois.
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Distinctive roles of Abi1 in regulating actin-associated proteins during human smooth muscle cell migration. Sci Rep 2020; 10:10667. [PMID: 32606387 PMCID: PMC7326921 DOI: 10.1038/s41598-020-67781-1] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2020] [Accepted: 06/12/2020] [Indexed: 12/13/2022] Open
Abstract
Smooth muscle cell migration is essential for many diverse biological processes such as pulmonary/cardiovascular development and homeostasis. Abi1 (Abelson interactor 1) is an adapter protein that has been implicated in nonmuscle cell migration. However, the role and mechanism of Abi1 in smooth muscle migration are largely unknown. Here, Abi1 knockdown by shRNA reduced human airway smooth muscle cell migration, which was restored by Abi1 rescue. Abi1 localized at the tip of lamellipodia and its protrusion coordinated with F-actin at the leading cell edge of live cells. In addition, we identified profilin-1 (Pfn-1), a G-actin transporter, as a new partner for Abi1. Abi1 knockdown reduced the recruitment of Pfn-1 to the leading cell edge. Moreover, Abi1 knockdown reduced the localization of the actin-regulatory proteins c-Abl (Abelson tyrosine kinase) and N-WASP (neuronal Wiskott–Aldrich Syndrome Protein) at the cell edge without affecting other migration-related proteins including pVASP (phosphorylated vasodilator stimulated phosphoprotein), cortactin and vinculin. Furthermore, we found that c-Abl and integrin β1 regulated the positioning of Abi1 at the leading edge. Taken together, the results suggest that Abi1 regulates cell migration by affecting Pfn-1 and N-WASP, but not pVASP, cortactin and focal adhesions. Integrin β1 and c-Abl are important for the recruitment of Abi1 to the leading edge.
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Wang Y, Wang R, Tang DD. Ste20-like Kinase-mediated Control of Actin Polymerization Is a New Mechanism for Thin Filament-associated Regulation of Airway Smooth Muscle Contraction. Am J Respir Cell Mol Biol 2020; 62:645-656. [PMID: 31913659 PMCID: PMC7193783 DOI: 10.1165/rcmb.2019-0310oc] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2019] [Accepted: 01/07/2020] [Indexed: 12/26/2022] Open
Abstract
It has been reported that actin polymerization is regulated by protein tyrosine phosphorylation in smooth muscle on contractile stimulation. The role of protein serine/threonine phosphorylation in modulating actin dynamics is underinvestigated. SLK (Ste20-like kinase) is a serine/threonine protein kinase that plays a role in apoptosis, cell cycle, proliferation, and migration. The function of SLK in smooth muscle is mostly unknown. Here, SLK knockdown (KD) inhibited acetylcholine (ACh)-induced actin polymerization and contraction without affecting myosin light chain phosphorylation at Ser-19 in human airway smooth muscle. Stimulation with ACh induced paxillin phosphorylation at Ser-272, which was reduced in SLK KD cells. However, SLK did not catalyze paxillin Ser-272 phosphorylation in vitro. But, SLK KD attenuated Plk1 (polo-like kinase 1) phosphorylation at Thr-210. Plk1 mediated paxillin phosphorylation at Ser-272 in vitro. Expression of the nonphosphorylatable paxillin mutant S272A (substitution of alanine at Ser-272) attenuated the agonist-enhanced F-actin/G-actin ratios without affecting myosin light chain phosphorylation. Because N-WASP (neuronal Wiskott-Aldrich Syndrome Protein) phosphorylation at Tyr-256 (an indication of its activation) promotes actin polymerization, we also assessed the role of paxillin phosphorylation in N-WASP activation. S272A paxillin inhibited the ACh-enhanced N-WASP phosphorylation at Tyr-256. Together, these results suggest that SLK regulates paxillin phosphorylation at Ser-272 via Plk1, which modulates N-WASP activation and actin polymerization in smooth muscle. SLK-mediated actin cytoskeletal reorganization may facilitate force transmission between the contractile units and the extracellular matrix.
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Affiliation(s)
- Yinna Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
| | - Ruping Wang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
| | - Dale D Tang
- Department of Molecular and Cellular Physiology, Albany Medical College, Albany, New York
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