1
|
Sazdova I, Hadzi-Petrushev N, Keremidarska-Markova M, Stojchevski R, Sopi R, Shileiko S, Mitrokhin V, Gagov H, Avtanski D, Lubomirov LT, Mladenov M. SIRT-associated attenuation of cellular senescence in vascular wall. Mech Ageing Dev 2024; 220:111943. [PMID: 38762036 DOI: 10.1016/j.mad.2024.111943] [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: 04/13/2024] [Revised: 05/13/2024] [Accepted: 05/14/2024] [Indexed: 05/20/2024]
Abstract
This review focuses on the vital function that SIRT1 and other sirtuins play in promoting cellular senescence in vascular smooth muscle cells, which is a key element in the pathogenesis of vascular aging and associated cardiovascular diseases. Vascular aging is a gradual process caused by the accumulation of senescent cells, which results in increased vascular remodeling, stiffness, and diminished angiogenic ability. Such physiological alterations are characterized by a complex interplay of environmental and genetic variables, including oxidative stress and telomere attrition, which affect gene expression patterns and trigger cell growth arrest. SIRT1 has been highlighted for its potential to reduce cellular senescence through modulation of multiple signaling cascades, particularly the endothelial nitric oxide (eNOS)/NO signaling pathway. It also modulates cell cycle through p53 inactivation and suppresses NF-κB mediated expression of adhesive molecules at the vascular level. The study also examines the therapeutic potential of sirtuin modulation in vascular health, identifying SIRT1 and its sirtuin counterparts as potential targets for reducing vascular aging. This study sheds light on the molecular basis of vascular aging and the beneficial effects of sirtuins, paving the way for the development of tailored therapies aimed at enhancing vascular health and prolonging life.
Collapse
Affiliation(s)
- Iliyana Sazdova
- Department of Animal and Human Physiology, Faculty of Biology, Sofia University 'St. Kliment Ohridski', Sofia 1504, Bulgaria
| | - Nikola Hadzi-Petrushev
- Institute of Biology, Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University, Skopje 1000, North Macedonia
| | - Milena Keremidarska-Markova
- Department of Animal and Human Physiology, Faculty of Biology, Sofia University 'St. Kliment Ohridski', Sofia 1504, Bulgaria
| | - Radoslav Stojchevski
- Friedman Diabetes Institute, Lenox Hill Hospital, Northwell Health, 110 E 59th Street, New York, NY 10022, USA
| | - Ramadan Sopi
- Faculty of Medicine, University of Prishtina, Prishtina 10 000, Kosovo
| | - Stanislav Shileiko
- Department of Fundamental and Applied Physiology, Russian States Medical University, Moscow 117997, Russia
| | - Vadim Mitrokhin
- Department of Fundamental and Applied Physiology, Russian States Medical University, Moscow 117997, Russia
| | - Hristo Gagov
- Department of Animal and Human Physiology, Faculty of Biology, Sofia University 'St. Kliment Ohridski', Sofia 1504, Bulgaria
| | - Dimitar Avtanski
- Friedman Diabetes Institute, Lenox Hill Hospital, Northwell Health, 110 E 59th Street, New York, NY 10022, USA
| | - Lubomir T Lubomirov
- Vascular Biology Research Group (RenEVA), Research Institute, Medical University-Varna, Varna, Bulgaria; Institute of Physiology and Pathophysiology, Faculty of Health - School of Medicine, Biomedical Center for Education and Research (ZBAF), Witten/Herdecke University, Witten, Germany
| | - Mitko Mladenov
- Institute of Biology, Faculty of Natural Sciences and Mathematics, Ss. Cyril and Methodius University, Skopje 1000, North Macedonia; Department of Fundamental and Applied Physiology, Russian States Medical University, Moscow 117997, Russia.
| |
Collapse
|
2
|
Oh SB, Cho S, Kim HJ, Kim SJ. Differential expression of the enzymes regulating myosin light chain phosphorylation are responsible for the slower relaxation of pulmonary artery than mesenteric artery in rats. THE KOREAN JOURNAL OF PHYSIOLOGY & PHARMACOLOGY : OFFICIAL JOURNAL OF THE KOREAN PHYSIOLOGICAL SOCIETY AND THE KOREAN SOCIETY OF PHARMACOLOGY 2024; 28:49-57. [PMID: 38154964 PMCID: PMC10762492 DOI: 10.4196/kjpp.2024.28.1.49] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 11/06/2023] [Accepted: 11/13/2023] [Indexed: 12/30/2023]
Abstract
While arterial tone is generally determined by the phosphorylation of Ser19 in myosin light chain (p-MLC2), Thr18/Ser19 diphosphorylation of MLC2 (pp-MLC2) has been suggested to hinder the relaxation of smooth muscle. In a dual-wire myography of rodent pulmonary artery (PA) and mesenteric artery (MA), we noticed significantly slower relaxation in PA than in MA after 80 mM KCl-induced condition (80K-contraction). Thus, we investigated the MLC2 phosphorylation and the expression levels of its regulatory enzymes; soluble guanylate cyclase (sGC), Rho-A dependent kinase (ROCK) and myosin light chain phosphatase target regulatory subunit (MYPT1). Immunoblotting showed higher sGC-α and ROCK2 in PA than MA, while sGC-β and MYPT1 levels were higher in MA than in PA. Interestingly, the level of pp-MLC2 was higher in PA than in MA without stimulation. In the 80K-contraction state, the levels of p-MLC2 and pp-MLC2 were commonly increased. Treatment with the ROCK inhibitor (Y27632, 10 μM) reversed the higher pp-MLC2 in PA. In the myography study, pharmacological inhibition of sGC (ODQ, 10 μM) slowed relaxation during washout, which was more pronounced in PA than in MA. The simultaneous treatment of Y27632 and ODQ reversed the impaired relaxation in PA and MA. Although treatment of PA with Y27632 alone could increase the rate of relaxation, it was still slower than that of MA without Y27632 treatment. Taken together, we suggest that the higher ROCK and lower MYPT in PA would have induced the higher level of MLC2 phosphorylation, which is responsible for the characteristic slow relaxation in PA.
Collapse
Affiliation(s)
- Seung Beom Oh
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea
| | - Suhan Cho
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea
- Department of Biochemistry and Molecular Biology, University of Maryland School of Medicine, Baltimore, MD 21201, USA
| | - Hyun Jong Kim
- Department of Physiology, Dongguk University College of Medicine, Gyeongju 38066, Korea
- Channelopathy Research Center (CRC), Dongguk University College of Medicine, Goyang 10326, Korea
| | - Sung Joon Kim
- Department of Biomedical Sciences, Seoul National University College of Medicine, Seoul 03080, Korea
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul 03080, Korea
| |
Collapse
|
3
|
Cho S, Oh SB, Kim HJ, Kim SJ. T18/S19 diphosphorylation of myosin regulatory light chain impairs pulmonary artery relaxation in monocrotaline-induced pulmonary hypertensive rats. Pflugers Arch 2023; 475:1097-1112. [PMID: 37422604 DOI: 10.1007/s00424-023-02836-6] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2023] [Revised: 04/29/2023] [Accepted: 06/26/2023] [Indexed: 07/10/2023]
Abstract
Phosphorylation of Ser19 (S19-p) on the myosin regulatory light chain (MLC2) is critical for arterial contraction. It has been shown that elevated RhoA-dependent kinase (ROCK) activity or decreased MLC phosphatase (MLCP) activity leads to further phosphorylation of Thr18 (T18/S19-pp), which has been linked to vasospastic diseases. However, this phenomenon has not yet been studied in the context of pulmonary arterial hypertension (PAH). In the monocrotaline-induced PAH (PAH-MCT) rat model, we observed a significant delay in pulmonary artery (PA) relaxation following high potassium-induced contraction, which persisted even with the use of an L-type calcium channel blocker or in a calcium-free solution. Immunoblot analysis showed increased levels of both S19-p and T18/S19-pp in unstimulated PAs from PAH-MCT rats. Proteomics analysis revealed a reduction in soluble guanylate cyclase (sGC) and protein kinase G (PKG) levels, and immunoblotting confirmed decreased levels of MYPT1 (a component of MLCP) and increased ROCK in PAH-MCT. In the control PAs, the pharmacological inhibition of sGC with ODQ resulted in a prominent delay of relaxation and increased T18/S19-pp as in PAH-MCT. The delayed relaxation and the T18/S19-pp in PAH-MCT were reversed by ROCK inhibitor, Y27632, while not by membrane permeable 8-Br-cGMP. The delayed relaxation and T18/S19-diP in the ODQ-treated control PA were also reversed by Y27632. Taken together, the decreased sGC and MLCP, and increased ROCK increased T18/S19-pp, which leads to the decreased ability of PA to relax in PAH-MCT rats. PA specific inhibition of ROCK or activation of MLCP are expected to serve as potential drugs in the treatment of PAH.
Collapse
Affiliation(s)
- Suhan Cho
- Department of Physiology, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Seung Beom Oh
- Department of Physiology, Seoul National University College of Medicine, Seoul, 03080, South Korea
| | - Hae Jin Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, 03080, South Korea
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea
- Department of Medical Pharmacology and Physiology, University of Missouri School of Medicine, MO, Columbia, USA
| | - Sung Joon Kim
- Department of Physiology, Seoul National University College of Medicine, Seoul, 03080, South Korea.
- Ischemic/Hypoxic Disease Institute, Seoul National University College of Medicine, Seoul, 03080, South Korea.
| |
Collapse
|
4
|
González-Herrera F, Clayton NS, Guzmán-Rivera D, Carrillo I, Castillo C, Catalán M, Anfossi R, Quintero-Pertuz H, Quilaqueo ME, Olea-Azar C, Rivera-Meza M, Kemmerling U, Ridley AJ, Vivar R, Maya JD. Statins change the cytokine profile in Trypanosoma cruzi-infected U937 macrophages and murine cardiac tissue through Rho-associated kinases inhibition. Front Immunol 2023; 13:1035589. [PMID: 36713380 PMCID: PMC9874148 DOI: 10.3389/fimmu.2022.1035589] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2022] [Accepted: 12/16/2022] [Indexed: 01/12/2023] Open
Abstract
Introduction Chronic Chagasic cardiomyopathy (CCC), caused by the protozoan Trypanosoma cruzi, is the most severe manifestation of Chagas disease.CCC is characterized by cardiac inflammation and fibrosis caused by a persistent inflammatory response. Following infection, macrophages secrete inflammatory mediators such as IL-1β, IL-6, and TNF-α to control parasitemia. Although this response contains parasite infection, it causes damage to the heart tissue. Thus, the use of immunomodulators is a rational alternative to CCC. Rho-associated kinase (ROCK) 1 and 2 are RhoA-activated serine/threonine kinases that regulate the actomyosin cytoskeleton. Both ROCKs have been implicated in the polarization of macrophages towards an M1 (pro-inflammatory) phenotype. Statins are FDA-approved lipid-lowering drugs that reduce RhoA signaling by inhibiting geranylgeranyl pyrophosphate (GGPP) synthesis. This work aims to identify the effect of statins on U937 macrophage polarization and cardiac tissue inflammation and its relationship with ROCK activity during T. cruzi infection. Methods PMA-induced, wild-type, GFP-, CA-ROCK1- and CA-ROCK2-expressing U937 macrophages were incubated with atorvastatin, or the inhibitors Y-27632, JSH-23, TAK-242, or C3 exoenzyme incubated with or without T. cruzi trypomastigotes for 30 min to evaluate the activity of ROCK and the M1 and M2 cytokine expression and secretion profiling. Also, ROCK activity was determined in T. cruzi-infected, BALB/c mice hearts. Results In this study, we demonstrate for the first time in macrophages that incubation with T. cruzi leads to ROCK activation via the TLR4 pathway, which triggers NF-κB activation. Inhibition of ROCKs by Y-27632 prevents NF-κB activation and the expression and secretion of M1 markers, as does treatment with atorvastatin. Furthermore, we show that the effect of atorvastatin on the NF-kB pathway and cytokine secretion is mediated by ROCK. Finally, statin treatment decreased ROCK activation and expression, and the pro-inflammatory cytokine production, promoting anti-inflammatory cytokine expression in chronic chagasic mice hearts. Conclusion These results suggest that the statin modulation of the inflammatory response due to ROCK inhibition is a potential pharmacological strategy to prevent cardiac inflammation in CCC.
Collapse
Affiliation(s)
- Fabiola González-Herrera
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Natasha S. Clayton
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Daniela Guzmán-Rivera
- Escuela de Farmacia, Facultad de Medicina, Universidad Andrés Bello, Santiago, Chile
| | - Ileana Carrillo
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Christian Castillo
- Núcleo de Investigación Aplicada en Ciencias Veterinarias y Agronómicas, Facultad de Medicina Veterinaria y Agronomía, Universidad de Las Américas, Santiago, Chile
| | - Mabel Catalán
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Renatto Anfossi
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Helena Quintero-Pertuz
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile
| | - María Elena Quilaqueo
- Department of Chemical Pharmacology and Toxicology, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, Santiago, Chile
| | - Claudio Olea-Azar
- Department of Inorganic and Analytical Chemistry, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, Santiago, Chile
| | - Mario Rivera-Meza
- Department of Chemical Pharmacology and Toxicology, Faculty of Chemical and Pharmaceutical Sciences, University of Chile, Santiago, Chile
| | - Ulrike Kemmerling
- Integrative Biology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile
| | - Anne J. Ridley
- School of Cellular and Molecular Medicine, Faculty of Life Sciences, University of Bristol, Bristol, United Kingdom
| | - Raúl Vivar
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile,*Correspondence: Juan Diego Maya, ; Raúl Vivar,
| | - Juan Diego Maya
- Molecular and Clinical Pharmacology Program, Instituto de Ciencias Biomédicas, Faculty of Medicine, University of Chile, Santiago, Chile,*Correspondence: Juan Diego Maya, ; Raúl Vivar,
| |
Collapse
|
5
|
MYPT1-PP1β phosphatase negatively regulates both chromatin landscape and co-activator recruitment for beige adipogenesis. Nat Commun 2022; 13:5715. [PMID: 36175407 PMCID: PMC9523048 DOI: 10.1038/s41467-022-33363-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2022] [Accepted: 09/14/2022] [Indexed: 12/05/2022] Open
Abstract
Protein kinase A promotes beige adipogenesis downstream from β-adrenergic receptor signaling by phosphorylating proteins, including histone H3 lysine 9 (H3K9) demethylase JMJD1A. To ensure homeostasis, this process needs to be reversible however, this step is not well understood. We show that myosin phosphatase target subunit 1- protein phosphatase 1β (MYPT1-PP1β) phosphatase activity is inhibited via PKA-dependent phosphorylation, which increases phosphorylated JMJD1A and beige adipogenesis. Mechanistically, MYPT1-PP1β depletion results in JMJD1A-mediated H3K9 demethylation and activation of the Ucp1 enhancer/promoter regions. Interestingly, MYPT1-PP1β also dephosphorylates myosin light chain which regulates actomyosin tension-mediated activation of YAP/TAZ which directly stimulates Ucp1 gene expression. Pre-adipocyte specific Mypt1 deficiency increases cold tolerance with higher Ucp1 levels in subcutaneous white adipose tissues compared to control mice, confirming this regulatory mechanism in vivo. Thus, we have uncovered regulatory cross-talk involved in beige adipogenesis that coordinates epigenetic regulation with direct activation of the mechano-sensitive YAP/TAZ transcriptional co-activators. How β-AR signaling coordinates epigenetic and transcriptional pathways is unknown. Here the authors show that cold-induced β-AR signaling negatively regulates MYPT1-PP1β phosphatase activity to orchestrate both pathways for beige adipogenesis.
Collapse
|
6
|
Kaneda T, Ifadotunnikmah F, Nugroho AE, Koshikawa S, Tadahiro S, Hirasawa Y, Morita H. Calofolic Acid-A from Calophyllum scriblitifolium Bark Has Vasorelaxant Activity via Indirect PKA Activation Caused by PI-3 Kinase Inhibition in Rat Vascular Smooth Muscle Cells. JOURNAL OF NATURAL PRODUCTS 2022; 85:2192-2198. [PMID: 35983865 DOI: 10.1021/acs.jnatprod.2c00502] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Previously, we isolated 2R,3S,15R-calofolic acids (CAs) from Calophyllum scriblitifolium bark, which showed vasorelaxant activity on phenylephrine (PE)-precontracted rat aortic rings. Although the effect was suggested to be induced via an extracellular Ca2+-independent manner and mainly acts on vascular smooth muscle, the exact mechanism of action of CAs remained unclear. Thus, this study investigated the detailed mechanism of calofolic acid-A (CA-A) induced vasorelaxation in an aortic ring specimen using rat vascular smooth muscle cells (VSMCs). The levels of PE-induced phosphorylation on MLC Ser19 decreased in VSMCs pretreated with CA-A. CA-A also decreased the phosphorylation of MYPT1 Thr696 and MYPT1 Thr853. On the other hand, CA-A increased the PE-induced phosphorylation of MYPT1 Ser695 and MYPT1 Ser668, which are reported to be phosphorylated by a cAMP-dependent protein kinase (PKA). CA-A slightly increased PKA substrate phosphorylation in a concentration-dependent manner. Furthermore, CA-A enhanced isoproterenol (ISO)-induced cAMP accumulation and PKA substrate phosphorylation. Treatment with PI-3 kinase (PI3K) inhibitor, LY294002, enhanced ISO-induced cAMP accumulation and PKA substrate phosphorylation in the same manner as CA-A treatment. Furthermore, CA-A was found to directly inhibit PI3K enzyme activity in a dose-dependent manner. Taken together, the present study indicated that CA-A induces vasorelaxation through an indirectly activated PKA-MYPT1 pathway caused by inhibition of PI3K activity.
Collapse
Affiliation(s)
- Toshio Kaneda
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Farida Ifadotunnikmah
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Alfarius Eko Nugroho
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Sae Koshikawa
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Sasaki Tadahiro
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Yusuke Hirasawa
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| | - Hiroshi Morita
- Faculty of Pharmaceutical Sciences, Hoshi University, Ebara 2-4-41, Shinagawa-ku, Tokyo 142-8501, Japan
| |
Collapse
|
7
|
Regulation of myosin light-chain phosphorylation and its roles in cardiovascular physiology and pathophysiology. Hypertens Res 2022; 45:40-52. [PMID: 34616031 DOI: 10.1038/s41440-021-00733-y] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2021] [Revised: 06/19/2021] [Accepted: 07/08/2021] [Indexed: 01/22/2023]
Abstract
The regulation of muscle contraction is a critical function in the cardiovascular system, and abnormalities may be life-threatening or cause illness. The common basic mechanism in muscle contraction is the interaction between the protein filaments myosin and actin. Although this interaction is primarily regulated by intracellular Ca2+, the primary targets and intracellular signaling pathways differ in vascular smooth muscle and cardiac muscle. Phosphorylation of the myosin regulatory light chain (RLC) is a primary molecular switch for smooth muscle contraction. The equilibrium between phosphorylated and unphosphorylated RLC is dynamically achieved through two enzymes, myosin light chain kinase, a Ca2+-dependent enzyme, and myosin phosphatase, which modifies the Ca2+ sensitivity of contractions. In cardiac muscle, the primary target protein for Ca2+ is troponin C on thin filaments; however, RLC phosphorylation also plays a modulatory role in contraction. This review summarizes recent advances in our understanding of the regulation, physiological function, and pathophysiological involvement of RLC phosphorylation in smooth and cardiac muscles.
Collapse
|
8
|
Morales MM, Pedowitz NJ, Pratt MR. O-GlcNAc modification of MYPT1 modulates lysophosphatidic acid-induced cell contraction in fibroblasts. J Biol Chem 2021; 296:100800. [PMID: 34019870 PMCID: PMC8191289 DOI: 10.1016/j.jbc.2021.100800] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2021] [Revised: 05/12/2021] [Accepted: 05/17/2021] [Indexed: 12/18/2022] Open
Abstract
Thousands of proteins have been found to be modified by O-GlcNAc, a common glycosylation modification of serine and threonine residues throughout the cytosol and nucleus. O-GlcNAc is enzymatically added and removed from proteins, making it a potential dynamic regulator of cell signaling. However, compared with other posttranslational modifications like phosphorylation, relatively few O-GlcNAc-regulated pathways have been discovered and biochemically characterized. We previously discovered one such pathway, where O-GlcNAc controls the contraction of fibroblasts initiated by the signaling lipid sphingosine-1-phosphate. Specifically, we found that O-GlcNAc modification of the phosphatase MYPT1 maintains its activity, resulting in dephosphorylation and deactivation of the myosin light chain of the actinomyosin complex. Another signaling lipid that leads to contraction of fibroblasts is lysophosphatidic acid, and this signaling pathway also converges on MYPT1 and actinomyosin. We therefore rationalized that O-GlcNAc would also control this pathway. Here, we used a combination of small molecule inhibitors, 2D and 3D cell cultures, and biochemistry to confirm our hypothesis. Specifically, we found that O-GlcNAc levels control the sensitivity of mouse and primary human dermal fibroblasts to lysophosphatidic acid–induced contraction in culture and the phosphorylation of MLC and that MYPT1 O-GlcNAc modification is responsible. These findings further solidify the importance of O-GlcNAc in regulating the biology of fibroblasts in response to procontractile stimuli.
Collapse
Affiliation(s)
- Murielle M Morales
- Department of Biological Sciences, University of Southern California, Los Angeles, California, USA
| | - Nichole J Pedowitz
- Department of Chemistry, University of Southern California, Los Angeles, California, USA
| | - Matthew R Pratt
- Department of Chemistry, University of Southern California, Los Angeles, California, USA; Department of Biological Sciences, University of Southern California, Los Angeles, California, USA.
| |
Collapse
|
9
|
MYPT1 O-GlcNAc modification regulates sphingosine-1-phosphate mediated contraction. Nat Chem Biol 2020; 17:169-177. [PMID: 32929277 PMCID: PMC7855082 DOI: 10.1038/s41589-020-0640-8] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Revised: 07/24/2020] [Accepted: 08/06/2020] [Indexed: 12/12/2022]
Abstract
Many intracellular proteins are modified by N-acetylglucosamine, a posttranslational modification termed O-GlcNAc. This modification is found on serine and threonine side-chains and has the potential to regulate signaling pathways through interplay with phosphorylation. Here, we discover and characterize one such example. We find that O-GlcNAc levels control the sensitivity of fibroblasts to actin contraction induced by the signaling lipid sphingosine-1-phosphate (S1P), culminating in the phosphorylation of myosin light chain (MLC) and cellular contraction. Specifically, O-GlcNAc modification of the phosphatase subunit MYPT1 inhibits this pathway by blocking MYPT1 phosphorylation, maintaining its activity and causing the dephosphorylation of MLC. Finally, we demonstrate that O-GlcNAc levels alter the sensitivity of primary human dermal fibroblasts in a collagen-matrix model of wound healing. Our findings have important implications for the role of O-GlcNAc in fibroblast motility and differentiation, particularly in diabetic wound healing.
Collapse
|
10
|
Deng JT, Bhaidani S, Sutherland C, MacDonald JA, Walsh MP. Rho-associated kinase and zipper-interacting protein kinase, but not myosin light chain kinase, are involved in the regulation of myosin phosphorylation in serum-stimulated human arterial smooth muscle cells. PLoS One 2019; 14:e0226406. [PMID: 31834925 PMCID: PMC6910671 DOI: 10.1371/journal.pone.0226406] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2019] [Accepted: 11/26/2019] [Indexed: 01/09/2023] Open
Abstract
Myosin regulatory light chain (LC20) phosphorylation plays an important role in vascular smooth muscle contraction and cell migration. Ca2+/calmodulin-dependent myosin light chain kinase (MLCK) phosphorylates LC20 (its only known substrate) exclusively at S19. Rho-associated kinase (ROCK) and zipper-interacting protein kinase (ZIPK) have been implicated in the regulation of LC20 phosphorylation via direct phosphorylation of LC20 at T18 and S19 and indirectly via phosphorylation of MYPT1 (the myosin targeting subunit of myosin light chain phosphatase, MLCP) and Par-4 (prostate-apoptosis response-4). Phosphorylation of MYPT1 at T696 and T853 inhibits MLCP activity whereas phosphorylation of Par-4 at T163 disrupts its interaction with MYPT1, exposing the sites of phosphorylation in MYPT1 and leading to MLCP inhibition. To evaluate the roles of MLCK, ROCK and ZIPK in these phosphorylation events, we investigated the time courses of phosphorylation of LC20, MYPT1 and Par-4 in serum-stimulated human vascular smooth muscle cells (from coronary and umbilical arteries), and examined the effects of siRNA-mediated MLCK, ROCK and ZIPK knockdown and pharmacological inhibition on these phosphorylation events. Serum stimulation induced rapid phosphorylation of LC20 at T18 and S19, MYPT1 at T696 and T853, and Par-4 at T163, peaking within 30–120 s. MLCK knockdown or inhibition, or Ca2+ chelation with EGTA, had no effect on serum-induced LC20 phosphorylation. ROCK knockdown decreased the levels of phosphorylation of LC20 at T18 and S19, of MYPT1 at T696 and T853, and of Par-4 at T163, whereas ZIPK knockdown decreased LC20 diphosphorylation, but increased phosphorylation of MYPT1 at T696 and T853 and of Par-4 at T163. ROCK inhibition with GSK429286A reduced serum-induced phosphorylation of LC20 at T18 and S19, MYPT1 at T853 and Par-4 at T163, while ZIPK inhibition by HS38 reduced only LC20 diphosphorylation. We also demonstrated that serum stimulation induced phosphorylation (activation) of ZIPK, which was inhibited by ROCK and ZIPK down-regulation and inhibition. Finally, basal phosphorylation of LC20 in the absence of serum stimulation was unaffected by MLCK, ROCK or ZIPK knockdown or inhibition. We conclude that: (i) serum stimulation of cultured human arterial smooth muscle cells results in rapid phosphorylation of LC20, MYPT1, Par-4 and ZIPK, in contrast to the slower phosphorylation of kinases and other proteins involved in other signaling pathways (Akt, ERK1/2, p38 MAPK and HSP27), (ii) ROCK and ZIPK, but not MLCK, are involved in serum-induced phosphorylation of LC20, (iii) ROCK, but not ZIPK, directly phosphorylates MYPT1 at T853 and Par-4 at T163 in response to serum stimulation, (iv) ZIPK phosphorylation is enhanced by serum stimulation and involves phosphorylation by ROCK and autophosphorylation, and (v) basal phosphorylation of LC20 under serum-free conditions is not attributable to MLCK, ROCK or ZIPK.
Collapse
Affiliation(s)
- Jing-Ti Deng
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Sabreena Bhaidani
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Cindy Sutherland
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Justin A. MacDonald
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Michael P. Walsh
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
- * E-mail:
| |
Collapse
|
11
|
Lubomirov LT, Gagov H, Schroeter MM, Wiesner RJ, Franko A. Augmented contractility of murine femoral arteries in a streptozotocin diabetes model is related to increased phosphorylation of MYPT1. Physiol Rep 2019; 7:e13975. [PMID: 30740930 PMCID: PMC6369311 DOI: 10.14814/phy2.13975] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2018] [Accepted: 12/13/2018] [Indexed: 12/19/2022] Open
Abstract
Diabetes mellitus (DM) is a metabolic disorder with high prevalence, and a major risk factor for macro- and microvascular abnormalities. This study was undertaken to explore the mechanisms of hypercontractility of murine femoral arteries (FA) obtained from mice with streptozotocin (STZ)-induced diabetes and its relation to the phosphorylation profile of the myosin phosphatase target subunit 1, MYPT1. The immunoreactivity of MYPT1 toward phospho-MYPT1-T696, MYPT1-T853, or MYPT1-S695, used as a read out for MYPT1 phosphorylation, has been studied by Western Blotting. Contractile activity of FA from control and STZ mice has been studied by wire myography. At basal conditions (no treatment), the immunoreactivity of MYPT1-T696/T853 was ~2-fold higher in the STZ arteries compared with controls. No changes in MYPT1-T696/853 phosphorylation were observed after stimulation with the Thromboxan-A2 analog, U46619. Neither basal nor U46619-stimulated phosphorylation of MYPT1 at S695 was affected by STZ treatment. Mechanical distensibility and basal tone of FA obtained from STZ animals were similar to controls. Maximal force after treatment of FA with the contractile agonists phenylephrine (10 μmol/L) or U46619 (1 μmol/L) was augmented in the arteries of STZ mice by ~2- and ~1.5-fold, respectively. In summary, our study suggests that development of a hypercontractile phenotype in murine FA in STZ diabetes is at least partially related to an increase in phosphorylation of MLCP at MYPT1-T696/853. Interestingly, the phosphorylation at S695 site was not altered in STZ-induced diabetes, supporting the view that S695 may serve as a sensor for mechanical activity which is not directly involved in tone regulation.
Collapse
Affiliation(s)
| | - Hristo Gagov
- Faculty of BiologySofia University St. Kliment OhridskiSofiaBulgaria
| | | | - Rudolf J. Wiesner
- Institute of Vegetative PhysiologyUniversity of CologneKölnGermany
- Cologne Excellence Cluster on Cellular Stress Responses in Aging‐Associated Diseases (CECAD)KölnGermany
| | - Andras Franko
- Institute of Vegetative PhysiologyUniversity of CologneKölnGermany
- German Center for Diabetes Research (DZD e.V.)NeuherbergGermany
- Division of EndocrinologyDepartment of Internal Medicine IVDiabetology, Angiology, Nephrology and Clinical ChemistryUniversity of TübingenTübingenGermany
| |
Collapse
|
12
|
Bátori R, Kumar S, Bordán Z, Cherian-Shaw M, Kovács-Kása A, MacDonald JA, Fulton DJR, Erdődi F, Verin AD. Differential mechanisms of adenosine- and ATPγS-induced microvascular endothelial barrier strengthening. J Cell Physiol 2018; 234:5863-5879. [PMID: 29271489 DOI: 10.1002/jcp.26419] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2017] [Revised: 10/18/2017] [Indexed: 12/11/2022]
Abstract
Maintenance of the endothelial cell (EC) barrier is critical to vascular homeostasis and a loss of barrier integrity results in increased vascular permeability. While the mechanisms that govern increased EC permeability have been under intense investigation over the past several decades, the processes regulating the preservation/restoration of the EC barrier remain poorly understood. Herein we show that the extracellular purines, adenosine (Ado) and adenosine 5'-[γ-thio]-triphosphate (ATPγS) can strengthen the barrier function of human lung microvascular EC (HLMVEC). This ability involves protein kinase A (PKA) activation and decreases in myosin light chain 20 (MLC20) phosphorylation secondary to the involvement of MLC phosphatase (MLCP). In contrast to Ado, ATPγS-induced PKA activation is accompanied by a modest, but significant decrease in cyclic adenosine monophosphate (cAMP) levels supporting the existence of an unconventional cAMP-independent pathway of PKA activation. Furthermore, ATPγS-induced EC barrier strengthening does not involve the Rap guanine nucleotide exchange factor 3 (EPAC1) which is directly activated by cAMP but is instead dependent upon PKA-anchor protein 2 (AKAP2) expression. We also found that AKAP2 can directly interact with the myosin phosphatase-targeting protein MYPT1 and that depletion of AKAP2 abolished ATPγS-induced increases in transendothelial electrical resistance. Ado-induced strengthening of the HLMVEC barrier required the coordinated activation of PKA and EPAC1 in a cAMP-dependent manner. In summary, ATPγS-induced enhancement of the EC barrier is EPAC1-independent and is instead mediated by activation of PKA which is then guided by AKAP2, in a cAMP-independent mechanism, to activate MLCP which dephosphorylates MLC20 resulting in reduced EC contraction and preservation.
Collapse
Affiliation(s)
- Róbert Bátori
- Vascular Biology Center, Augusta University, Augusta, Georgia
| | - Sanjiv Kumar
- Vascular Biology Center, Augusta University, Augusta, Georgia
| | | | | | | | - Justin A MacDonald
- Department of Biochemistry & Molecular Biology, Smooth Muscle Research Group, University of Calgary, Calgary, Alberta, Canada
| | - David J R Fulton
- Vascular Biology Center, Augusta University, Augusta, Georgia.,Department of Pharmacology, Augusta University, Augusta, Georgia
| | - Ferenc Erdődi
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.,MTA-DE Cell Biology and Signalling Research Group, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Alexander D Verin
- Vascular Biology Center, Augusta University, Augusta, Georgia.,Department of Medicine, Augusta University, Augusta, Georgia
| |
Collapse
|
13
|
Carlson DA, Singer MR, Sutherland C, Redondo C, Alexander LT, Hughes PF, Knapp S, Gurley SB, Sparks MA, MacDonald JA, Haystead TAJ. Targeting Pim Kinases and DAPK3 to Control Hypertension. Cell Chem Biol 2018; 25:1195-1207.e32. [PMID: 30033129 PMCID: PMC6863095 DOI: 10.1016/j.chembiol.2018.06.006] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 03/16/2018] [Accepted: 06/20/2018] [Indexed: 01/19/2023]
Abstract
Sustained vascular smooth muscle hypercontractility promotes hypertension and cardiovascular disease. The etiology of hypercontractility is not completely understood. New therapeutic targets remain vitally important for drug discovery. Here we report that Pim kinases, in combination with DAPK3, regulate contractility and control hypertension. Using a co-crystal structure of lead molecule (HS38) in complex with DAPK3, a dual Pim/DAPK3 inhibitor (HS56) and selective DAPK3 inhibitors (HS94 and HS148) were developed to provide mechanistic insight into the polypharmacology of hypertension. In vitro and ex vivo studies indicated that Pim kinases directly phosphorylate smooth muscle targets and that Pim/DAPK3 inhibition, unlike selective DAPK3 inhibition, significantly reduces contractility. In vivo, HS56 decreased blood pressure in spontaneously hypertensive mice in a dose-dependent manner without affecting heart rate. These findings suggest including Pim kinase inhibition within a multi-target engagement strategy for hypertension management. HS56 represents a significant step in the development of molecularly targeted antihypertensive medications.
Collapse
Affiliation(s)
- David A Carlson
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Miriam R Singer
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Cindy Sutherland
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N 4Z6, Canada
| | - Clara Redondo
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Leila T Alexander
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK
| | - Philip F Hughes
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA
| | - Stefan Knapp
- Structural Genomics Consortium, University of Oxford, Oxford OX3 7DQ, UK; Institute for Pharmaceutical Chemistry, Johann Wolfgang Goethe-University, Max-von-Laue-Strasse 9, 60438 Frankfurt am Main, Germany
| | - Susan B Gurley
- Division of Nephrology, Department of Medicine, Duke University and Durham VA Medical Centers, Durham, NC 27710, USA
| | - Matthew A Sparks
- Division of Nephrology, Department of Medicine, Duke University and Durham VA Medical Centers, Durham, NC 27710, USA
| | - Justin A MacDonald
- Department of Biochemistry & Molecular Biology, Cumming School of Medicine, University of Calgary, 3280 Hospital Drive NW, Calgary, AB T2N 4Z6, Canada
| | - Timothy A J Haystead
- Department of Pharmacology and Cancer Biology, Duke University Medical Center, Durham, NC 27710, USA.
| |
Collapse
|
14
|
Lubomirov LT, Papadopoulos S, Filipova D, Baransi S, Todorović D, Lake P, Metzler D, Hilsdorf S, Schubert R, Schroeter MM, Pfitzer G. The involvement of phosphorylation of myosin phosphatase targeting subunit 1 (MYPT1) and MYPT1 isoform expression in NO/cGMP mediated differential vasoregulation of cerebral arteries compared to systemic arteries. Acta Physiol (Oxf) 2018; 224:e13079. [PMID: 29694711 DOI: 10.1111/apha.13079] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2017] [Revised: 03/30/2018] [Accepted: 04/17/2018] [Indexed: 12/23/2022]
Abstract
AIM Constitutive release of NO blunts intrinsic and stimulated contractile activity in cerebral arteries (CA). Here, we explored whether phosphorylation and expression levels of the PKG-sensitive, leucine zipper positive (LZ+ ) splice variants of the regulatory subunit of myosin phosphatase (MYPT1) are involved and whether its expression is associated with higher cGMP sensitivity. METHODS Vascular contractility was investigated by wire myography. Phosphorylation of MYPT1 was determined by Western blotting. RESULTS Constitutive phosphorylation of MYPT1-T696 and T853 was lower and that of S695 and S668 was higher in cerebral arteries from the circulus arteriosus (CA-w) than in femoral arteries (FA), while total MYPT1 expression was not different. In CA-w but not in FA, L-NAME lowered phosphorylation of S695/S668 and increased phosphorylation of T696/T853 and of MLC20 -S19, plus basal tone. The increase in basal tone was attenuated in CA-w and basilar arteries (BA) from heterozygous MYPT1-T696A/+ mice. Compared to FA, expression of the LZ+ -isoform was ~2-fold higher in CA-w coincident with a higher sensitivity to DEA-NONOate, cinaciguat and Y27632 in BA and 8-Br-cGMP (1 μmol/L) in pre-constricted (pCa 6.1) α-toxin permeabilized CAs. In contrast, 6-Bnz-cAMP (10 μmol/L) relaxed BA and FA similarly by ~80%. CONCLUSION Our results indicate that (i) regulation of the intrinsic contractile activity in CA involves phosphorylation of MYPT1 at T696 and S695/S668, (ii) the higher NO/cGMP/PKG sensitivity of CAs can be ascribed to the higher expression level of the LZ+ -MYPT1 isoform and (iii) relaxation by cAMP/PKA pathway is less dependent on the expression level of the LZ+ splice variants of MYPT1.
Collapse
Affiliation(s)
- L. T. Lubomirov
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - S. Papadopoulos
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - D. Filipova
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - S. Baransi
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - D. Todorović
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - P. Lake
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - D. Metzler
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - S. Hilsdorf
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - R. Schubert
- Research Division Cardiovascular Physiology; Centre for Biomedicine and Medical Technology Mannheim (CBTM); Ruprecht-Karls-University Heidelberg; Heidelberg Germany
| | - M. M. Schroeter
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| | - G. Pfitzer
- Institute of Vegetative Physiology; University of Cologne; Cologne Germany
| |
Collapse
|
15
|
Basu S, Barbur I, Calderon A, Banerjee S, Proweller A. Notch signaling regulates arterial vasoreactivity through opposing functions of Jagged1 and Dll4 in the vessel wall. Am J Physiol Heart Circ Physiol 2018; 315:H1835-H1850. [PMID: 30168730 DOI: 10.1152/ajpheart.00293.2018] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Functional interactions between endothelial cells (ECs) and smooth muscle cells (SMCs) in the arterial wall are necessary for controlling vasoreactivity that underlies vascular resistance and tone. Key signaling pathways converge on the phosphorylation of myosin light chain (p-MLC), the molecular signature of force production in SMCs, through coordinating the relative activities of myosin light chain kinase (MLCK) and myosin phosphatase (MP). Notch signaling in the vessel wall serves critical roles in arterial formation and maturation and has been implicated in arterial vasoregulation. In this report, we hypothesized that Notch signaling through ligands Jagged1 (in SMCs) and delta-like protein-4 (Dll4; in ECs) regulates vasoreactivity via homotypic (SMC-SMC) and heterotypic (EC-SMC) cell interactions. Using ligand induction assays, we demonstrated that Jagged1 selectively induced smooth muscle MLCK gene expression and p-MLC content while inhibiting MP function (i.e., increased Ca2+ sensitization) in a Rho kinase II-dependent manner. Likewise, selective deficiency of smooth muscle Jagged1 in mice resulted in MLCK and p-MLC loss, reduced Ca2+ sensitization, and impaired arterial force generation measured by myography. In contrast, smooth muscle Notch signaling triggered by Dll4 increased expression of MP-targeting subunit 1 (MYPT1; the MP regulatory subunit), whereas arteries from endothelial Dll4-deficient mice featured reduced MYPT1 levels, enhanced force production, and impaired relaxation independent of endothelium-derived nitric oxide signaling. Taken together, this study identifies novel opposing vasoregulatory functions for ligand-specific Notch signaling in the vessel wall, underscoring instructional signaling between ECs and SMCs and suggesting that Notch signals might behave as a "rheostat" in arterial tone control. NEW & NOTEWORTHY The present study unveils novel roles for ligand-specific Notch signaling in arterial function. Smooth muscle Jagged1 and endothelial cell delta-like protein-4 ligands exhibit selective regulation of myosin light chain kinase and myosin phosphatase-targeting subunit 1/myosin phosphatase, respectively, providing a mechanistic link through which Notch signals modulate contractile activities in vascular smooth muscle. These findings may inform vascular derangements observed in human syndromes of Notch signaling deficiency while offering fundamental molecular insights into arterial physiological function.
Collapse
Affiliation(s)
- Sanchita Basu
- Department of Medicine, Case Cardiovascular Research Institute and University Hospitals Harrington Heart and Vascular Institute, Case Western Reserve University , Cleveland, Ohio
| | - Iulia Barbur
- Department of Medicine, Case Cardiovascular Research Institute and University Hospitals Harrington Heart and Vascular Institute, Case Western Reserve University , Cleveland, Ohio
| | - Alexander Calderon
- Department of Medicine, Case Cardiovascular Research Institute and University Hospitals Harrington Heart and Vascular Institute, Case Western Reserve University , Cleveland, Ohio
| | - Suhanti Banerjee
- Department of Medicine, Case Cardiovascular Research Institute and University Hospitals Harrington Heart and Vascular Institute, Case Western Reserve University , Cleveland, Ohio
| | - Aaron Proweller
- Department of Medicine, Case Cardiovascular Research Institute and University Hospitals Harrington Heart and Vascular Institute, Case Western Reserve University , Cleveland, Ohio
| |
Collapse
|
16
|
Kiss A, Erdődi F, Lontay B. Myosin phosphatase: Unexpected functions of a long-known enzyme. BIOCHIMICA ET BIOPHYSICA ACTA-MOLECULAR CELL RESEARCH 2018; 1866:2-15. [PMID: 30076859 DOI: 10.1016/j.bbamcr.2018.07.023] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/13/2018] [Revised: 07/09/2018] [Accepted: 07/26/2018] [Indexed: 01/08/2023]
Abstract
Myosin phosphatase (MP) holoenzyme is a Ser/Thr specific enzyme, which is the member of protein phosphatase type 1 (PP1) family and composed of a PP1 catalytic subunit (PP1c/PPP1CB) and a myosin phosphatase targeting subunit (MYPT1/PPP1R12A). PP1c is required for the catalytic activity of the holoenzyme, while MYPT1 regulates MP through targeting the holoenzyme to its substrates. Above the well-characterized function of MP, as the major regulator of smooth muscle contractility mediating the dephosphorylation of 20 kDa myosin light chain, accumulating data support its role in other, non-contractile functions. In this review, we summarize the scaffold function of MP holoenzyme and its roles in processes such as cell cycle, development, gene expression regulation and neurotransmitter release. In particular, we highlight novel interacting proteins of MYPT1 and pathophysiological functions of MP relevant to tumorigenesis, insulin resistance and neurodegenerative disorders. This article is part of a Special Issue entitled: Protein Phosphatases as Critical Regulators for Cellular Homeostasis edited by Prof. Peter Ruvolo and Dr. Veerle Janssens.
Collapse
Affiliation(s)
- Andrea Kiss
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Ferenc Erdődi
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary; MTA-DE Cell Biology and Signaling Research Group, Faculty of Medicine, University of Debrecen, Debrecen, Hungary
| | - Beáta Lontay
- Department of Medical Chemistry, Faculty of Medicine, University of Debrecen, Debrecen, Hungary.
| |
Collapse
|
17
|
Yang Q, Fujii W, Kaji N, Kakuta S, Kada K, Kuwahara M, Tsubone H, Ozaki H, Hori M. The essential role of phospho‐T38 CPI‐17 in the maintenance of physiological blood pressure using genetically modified mice. FASEB J 2018; 32:2095-2109. [DOI: 10.1096/fj.201700794r] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/30/2023]
Affiliation(s)
- Qunhui Yang
- Department of Veterinary Pharmacology, Laboratory of Applied Genetics, Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Wataru Fujii
- Laboratory of Applied Genetics, Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Noriyuki Kaji
- Department of Veterinary Pharmacology, Laboratory of Applied Genetics, Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Shigeru Kakuta
- Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Kodai Kada
- Department of Veterinary Pharmacology, Laboratory of Applied Genetics, Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Masayoshi Kuwahara
- Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Hirokazu Tsubone
- Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Hiroshi Ozaki
- Department of Veterinary Pharmacology, Laboratory of Applied Genetics, Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| | - Masatoshi Hori
- Department of Veterinary Pharmacology, Laboratory of Applied Genetics, Department of Biomedical Science, Department of Veterinary Pathophysiology and Animal Health, and Research Center for Food SafetyGraduate School of Agriculture and Life Sciences, The University of TokyoTokyoJapan
| |
Collapse
|
18
|
Behringer EJ. Calcium and electrical signaling in arterial endothelial tubes: New insights into cellular physiology and cardiovascular function. Microcirculation 2018; 24. [PMID: 27801542 DOI: 10.1111/micc.12328] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2016] [Accepted: 10/25/2016] [Indexed: 12/23/2022]
Abstract
The integral role of the endothelium during the coordination of blood flow throughout vascular resistance networks has been recognized for several decades now. Early examination of the distinct anatomy and physiology of the endothelium as a signaling conduit along the vascular wall has prompted development and application of an intact endothelial "tube" study model isolated from rodent skeletal muscle resistance arteries. Vasodilatory signals such as increased endothelial cell (EC) Ca2+ ([Ca2+ ]i ) and hyperpolarization take place in single ECs while shared between electrically coupled ECs through gap junctions up to distances of millimeters (≥2 mm). The small- and intermediate-conductance Ca2+ activated K+ (SKCa /IKCa or KCa 2.3/KCa 3.1) channels function at the interface of Ca2+ signaling and hyperpolarization; a bidirectional relationship whereby increases in [Ca2+ ]i activate SKCa /IKCa channels to produce hyperpolarization and vice versa. Further, the spatial domain of hyperpolarization among electrically coupled ECs can be finely tuned via incremental modulation of SKCa /IKCa channels to balance the strength of local and conducted electrical signals underlying vasomotor activity. Multifunctional properties of the voltage-insensitive SKCa /IKCa channels of resistance artery endothelium may be employed for therapy during the aging process and development of vascular disease.
Collapse
Affiliation(s)
- Erik J Behringer
- Department of Basic Sciences, Loma Linda University, Loma Linda, CA, USA
| |
Collapse
|
19
|
Eto M, Kitazawa T. Diversity and plasticity in signaling pathways that regulate smooth muscle responsiveness: Paradigms and paradoxes for the myosin phosphatase, the master regulator of smooth muscle contraction. J Smooth Muscle Res 2018; 53:1-19. [PMID: 28260704 PMCID: PMC5364378 DOI: 10.1540/jsmr.53.1] [Citation(s) in RCA: 26] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
A hallmark of smooth muscle cells is their ability to adapt their functions to meet temporal and chronic fluctuations in their demands. These functions include force development and growth. Understanding the mechanisms underlying the functional plasticity of smooth muscles, the major constituent of organ walls, is fundamental to elucidating pathophysiological rationales of failures of organ functions. Also, the knowledge is expected to facilitate devising innovative strategies that more precisely monitor and normalize organ functions by targeting individual smooth muscles. Evidence has established a current paradigm that the myosin light chain phosphatase (MLCP) is a master regulator of smooth muscle responsiveness to stimuli. Cellular MLCP activity is negatively and positively regulated in response to G-protein activation and cAMP/cGMP production, respectively, through the MYPT1 regulatory subunit and an endogenous inhibitor protein named CPI-17. In this article we review the outcomes from two decade of research on the CPI-17 signaling and discuss emerging paradoxes in the view of signaling pathways regulating smooth muscle functions through MLCP.
Collapse
Affiliation(s)
- Masumi Eto
- Department of Molecular Physiology and Biophysics, Sidney Kimmel Medical College at Thomas Jefferson University and Sidney Kimmel Cancer Center, 1020 Locust Street, Philadelphia, PA19107, USA
| | | |
Collapse
|
20
|
Yang G, Bibi S, Du M, Suzuki T, Zhu MJ. Regulation of the intestinal tight junction by natural polyphenols: A mechanistic perspective. Crit Rev Food Sci Nutr 2018; 57:3830-3839. [PMID: 27008212 DOI: 10.1080/10408398.2016.1152230] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
Impairment of the epithelial barrier function is closely linked to the pathogenesis of various gastrointestinal diseases, food allergies, type I diabetes, and other systematic diseases. Plant-derived polyphenols are natural secondary metabolites and exert various physiological benefits, including anti-inflammatory, anti-oxidative, anti-carcinogenic, and anti-aging effects. Recent studies also show the role of plant polyphenols in regulation of the intestinal barrier and prevention of intestinal inflammatory diseases. Here we summarize the regulatory pathways and mediators linking polyphenols to their beneficial effects on tight junction and gut epithelial barrier functions, and provide useful information about using polyphenols as nutraceuticals for intestinal diseases.
Collapse
Affiliation(s)
- Guan Yang
- a School of Food Science , Washington State University , Pullman , Washington , USA
| | - Shima Bibi
- a School of Food Science , Washington State University , Pullman , Washington , USA
| | - Min Du
- b Department of Animal Science , Washington State University , Pullman , Washington , USA
| | - Takuya Suzuki
- c Department of Biofunctional Science and Technology , Hiroshima University , Higashi-Hiroshima , Japan
| | - Mei-Jun Zhu
- a School of Food Science , Washington State University , Pullman , Washington , USA
| |
Collapse
|
21
|
Boratkó A, Csortos C. TIMAP, the versatile protein phosphatase 1 regulator in endothelial cells. IUBMB Life 2017; 69:918-928. [DOI: 10.1002/iub.1695] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2017] [Accepted: 10/26/2017] [Indexed: 01/28/2023]
Affiliation(s)
- Anita Boratkó
- Department of Medical Chemistry; Faculty of Medicine, University of Debrecen, Egyetem tér 1; Debrecen Hungary
| | - Csilla Csortos
- Department of Medical Chemistry; Faculty of Medicine, University of Debrecen, Egyetem tér 1; Debrecen Hungary
| |
Collapse
|
22
|
Lin S, Brozovich FV. MYPT1 isoforms expressed in HEK293T cells are differentially phosphorylated after GTPγS treatment. J Smooth Muscle Res 2017; 52:66-77. [PMID: 27725371 PMCID: PMC5321854 DOI: 10.1540/jsmr.52.66] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Agonist stimulation of smooth muscle is known to activate RhoA/Rho kinase signaling, and
Rho kinase phosphorylates the myosin targeting subunit (MYPT1) of myosin light chain (MLC)
phosphatase at Thr696 and Thr853, which inhibits the activity of MLC phosphatase to
produce a Ca2+ independent increase in MLC phosphorylation and force (Ca2+ sensitization).
Alternative mRNA splicing produces four MYPT1 isoforms, which differ by the presence or
absence of a central insert (CI) and leucine zipper (LZ). This study was designed to
determine if Rho kinase differentially phosphorylates MYPT1 isoforms. In HEK293T cells
expressing each of the four MYPT1 isoforms, we could not detect a change in Thr853 MYPT1
phosphorylation following GTPγS treatment. However, there is differential phosphorylation
of MYPT1 isoforms at Thr696; GTPγS treatment increases MYPT1 phosphorylation for the
CI+LZ- and CI-LZ- MYPT1 isoforms, but not the CI+LZ+ or CI-LZ+ MYPT1 isoforms. These data
could suggest that in smooth muscle Rho kinase differentially phosphorylates MYPT1
isoforms.
Collapse
Affiliation(s)
- Simon Lin
- Mayo Medical School, Department of Cardiovascular Disease, Rochester, MN 55905, USA
| | | |
Collapse
|
23
|
Protein phosphatases 1 and 2A and their naturally occurring inhibitors: current topics in smooth muscle physiology and chemical biology. J Physiol Sci 2017; 68:1-17. [PMID: 28681362 PMCID: PMC5754374 DOI: 10.1007/s12576-017-0556-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2017] [Accepted: 06/27/2017] [Indexed: 12/26/2022]
Abstract
Protein phosphatases 1 and 2A (PP1 and PP2A) are the most ubiquitous and abundant serine/threonine phosphatases in eukaryotic cells. They play fundamental roles in the regulation of various cellular functions. This review focuses on recent advances in the functional studies of these enzymes in the field of smooth muscle physiology. Many naturally occurring protein phosphatase inhibitors with different relative PP1/PP2A affinities have been discovered and are widely used as powerful research tools. Current topics in the chemical biology of PP1/PP2A inhibitors are introduced and discussed, highlighting the identification of the gene cluster responsible for the biosynthesis of calyculin A in a symbiont microorganism of a marine sponge.
Collapse
|
24
|
Filter JJ, Williams BC, Eto M, Shalloway D, Goldberg ML. Unfair competition governs the interaction of pCPI-17 with myosin phosphatase (PP1-MYPT1). eLife 2017; 6. [PMID: 28387646 PMCID: PMC5441869 DOI: 10.7554/elife.24665] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 03/31/2017] [Indexed: 11/30/2022] Open
Abstract
The small phosphoprotein pCPI-17 inhibits myosin light-chain phosphatase (MLCP). Current models postulate that during muscle relaxation, phosphatases other than MLCP dephosphorylate and inactivate pCPI-17 to restore MLCP activity. We show here that such hypotheses are insufficient to account for the observed rapidity of pCPI-17 inactivation in mammalian smooth muscles. Instead, MLCP itself is the critical enzyme for pCPI-17 dephosphorylation. We call the mutual sequestration mechanism through which pCPI-17 and MLCP interact inhibition by unfair competition: MLCP protects pCPI-17 from other phosphatases, while pCPI-17 blocks other substrates from MLCP’s active site. MLCP dephosphorylates pCPI-17 at a slow rate that is, nonetheless, both sufficient and necessary to explain the speed of pCPI-17 dephosphorylation and the consequent MLCP activation during muscle relaxation. DOI:http://dx.doi.org/10.7554/eLife.24665.001
Collapse
Affiliation(s)
- Joshua J Filter
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Byron C Williams
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Masumi Eto
- Department of Molecular Physiology and Biophysics, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States
| | - David Shalloway
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Michael L Goldberg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| |
Collapse
|
25
|
Smooth Muscle Phenotypic Diversity: Effect on Vascular Function and Drug Responses. ADVANCES IN PHARMACOLOGY 2017. [PMID: 28212802 DOI: 10.1016/bs.apha.2016.07.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/15/2023]
Abstract
At its simplest resistance to blood flow is regulated by changes in the state of contraction of the vascular smooth muscle (VSM), a function of the competing activities of the myosin kinase and phosphatase determining the phosphorylation and activity of the myosin ATPase motor protein. In contrast, the vascular system of humans and other mammals is incredibly complex and highly regulated. Much of this complexity derives from phenotypic diversity within the smooth muscle, reflected in very differing power outputs and responses to signaling pathways that regulate vessel tone, presumably having evolved over the millennia to optimize vascular function and its control. The highly regulated nature of VSM tone, described as pharmacomechanical coupling, likely underlies the many classes of drugs in clinical use to alter vascular tone through activation or inhibition of these signaling pathways. This review will first describe the phenotypic diversity within VSM, followed by presentation of specific examples of how molecular diversity in signaling, myofilament, and calcium cycling proteins impacts arterial smooth muscle function and drug responses.
Collapse
|
26
|
Barabutis N, Verin A, Catravas JD. Regulation of pulmonary endothelial barrier function by kinases. Am J Physiol Lung Cell Mol Physiol 2016; 311:L832-L845. [PMID: 27663990 DOI: 10.1152/ajplung.00233.2016] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2016] [Accepted: 09/15/2016] [Indexed: 12/15/2022] Open
Abstract
The pulmonary endothelium is the target of continuous physiological and pathological stimuli that affect its crucial barrier function. The regulation, defense, and repair of endothelial barrier function require complex biochemical processes. This review examines the role of endothelial phosphorylating enzymes, kinases, a class with profound, interdigitating influences on endothelial permeability and lung function.
Collapse
Affiliation(s)
- Nektarios Barabutis
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, Virginia
| | - Alexander Verin
- Vascular Biology Center, Augusta University, Augusta, Georgia; and
| | - John D Catravas
- Frank Reidy Research Center for Bioelectrics, Old Dominion University, Norfolk, Virginia, .,School of Medical Diagnostic and Translational Sciences, College of Health Sciences, Old Dominion University, Norfolk, Virginia
| |
Collapse
|
27
|
Al-Ghabkari A, Deng JT, McDonald PC, Dedhar S, Alshehri M, Walsh MP, MacDonald JA. A novel inhibitory effect of oxazol-5-one compounds on ROCKII signaling in human coronary artery vascular smooth muscle cells. Sci Rep 2016; 6:32118. [PMID: 27573465 PMCID: PMC5004178 DOI: 10.1038/srep32118] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2016] [Accepted: 08/02/2016] [Indexed: 12/27/2022] Open
Abstract
The selectivity of (4Z)-2-(4-chloro-3-nitrophenyl)-4-(pyridin-3-ylmethylidene)-1,3-oxazol-5-one (DI) for zipper-interacting protein kinase (ZIPK) was previously described by in silico computational modeling, screening a large panel of kinases, and determining the inhibition efficacy. Our assessment of DI revealed another target, the Rho-associated coiled-coil-containing protein kinase 2 (ROCKII). In vitro studies showed DI to be a competitive inhibitor of ROCKII (Ki, 132 nM with respect to ATP). This finding was supported by in silico molecular surface docking of DI with the ROCKII ATP-binding pocket. Time course analysis of myosin regulatory light chain (LC20) phosphorylation catalyzed by ROCKII in vitro revealed a significant decrease upon treatment with DI. ROCKII signaling was investigated in situ in human coronary artery vascular smooth muscle cells (CASMCs). ROCKII down-regulation using siRNA revealed several potential substrates involved in smooth muscle contraction (e.g., LC20, Par-4, MYPT1) and actin cytoskeletal dynamics (cofilin). The application of DI to CASMCs attenuated LC20, Par-4, LIMK, and cofilin phosphorylations. Notably, cofilin phosphorylation was not significantly decreased with a novel ZIPK selective inhibitor (HS-38). In addition, CASMCs treated with DI underwent cytoskeletal changes that were associated with diminution of cofilin phosphorylation. We conclude that DI is not selective for ZIPK and is a potent inhibitor of ROCKII.
Collapse
Affiliation(s)
- Abdulhameed Al-Ghabkari
- Department of Biochemistry &Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| | - Jing-Ti Deng
- Department of Biochemistry &Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| | - Paul C McDonald
- Department of Integrative Oncology, BC Cancer Research Centre, 675 West 10th Ave, Vancouver, BC, V5Z 1L3, Canada
| | - Shoukat Dedhar
- Department of Integrative Oncology, BC Cancer Research Centre, 675 West 10th Ave, Vancouver, BC, V5Z 1L3, Canada
| | - Mana Alshehri
- Department of Biochemistry &Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| | - Michael P Walsh
- Department of Biochemistry &Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| | - Justin A MacDonald
- Department of Biochemistry &Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, T2N 4Z6, Canada
| |
Collapse
|
28
|
Reho JJ, Kenchegowda D, Asico LD, Fisher SA. A splice variant of the myosin phosphatase regulatory subunit tunes arterial reactivity and suppresses response to salt loading. Am J Physiol Heart Circ Physiol 2016; 310:H1715-24. [PMID: 27084390 DOI: 10.1152/ajpheart.00869.2015] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/06/2015] [Accepted: 04/12/2016] [Indexed: 12/21/2022]
Abstract
The cGMP activated kinase cGK1α is targeted to its substrates via leucine zipper (LZ)-mediated heterodimerization and thereby mediates vascular smooth muscle (VSM) relaxation. One target is myosin phosphatase (MP), which when activated by cGK1α results in VSM relaxation even in the presence of activating calcium. Variants of MP regulatory subunit Mypt1 are generated by alternative splicing of the 31 nt exon 24 (E24), which, by changing the reading frame, codes for isoforms that contain or lack the COOH-terminal LZ motif (E24+/LZ-; E24-/LZ+). Expression of these isoforms is vessel specific and developmentally regulated, modulates in disease, and is proposed to confer sensitivity to nitric oxide (NO)/cGMP-mediated vasorelaxation. To test this, mice underwent Tamoxifen-inducible and smooth muscle-specific knockout of E24 (E24 cKO) after weaning. Deletion of a single allele of E24 (shift to Mypt1 LZ+) enhanced vasorelaxation of first-order mesenteric arteries (MA1) to diethylamine-NONOate (DEA/NO) and to cGMP in permeabilized and calcium-clamped arteries and lowered blood pressure. There was no further effect of deletion of both E24 alleles, indicating high sensitivity to shift of Mypt1 isoforms. However, a unique property of MA1s from homozygous E24 cKOs was significantly reduced force generation to α-adrenergic activation. Furthermore 2 wk of high-salt (4% NaCl) diet increased MA1 force generation to phenylephrine in control mice, a response that was markedly suppressed in the E24 cKO homozygotes. Thus Mypt1 E24 splice variants tune arterial reactivity and could be worthy targets for lowering vascular resistance in disease states.
Collapse
Affiliation(s)
- John J Reho
- Department of Medicine, Divisions of Cardiovascular Medicine and Nephrology, University of Maryland-Baltimore, Baltimore, Maryland
| | - Doreswamy Kenchegowda
- Department of Medicine, Divisions of Cardiovascular Medicine and Nephrology, University of Maryland-Baltimore, Baltimore, Maryland
| | - Laureano D Asico
- Department of Medicine, Divisions of Cardiovascular Medicine and Nephrology, University of Maryland-Baltimore, Baltimore, Maryland
| | - Steven A Fisher
- Department of Medicine, Divisions of Cardiovascular Medicine and Nephrology, University of Maryland-Baltimore, Baltimore, Maryland
| |
Collapse
|
29
|
MacDonald JA. A tale of two threonines: myosin phosphatase inhibition and calcium sensitization of smooth muscle. J Physiol 2016; 593:487-8. [PMID: 25774393 DOI: 10.1113/jphysiol.2014.270019] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
|
30
|
Sutherland C, MacDonald JA, Walsh MP. Analysis of phosphorylation of the myosin-targeting subunit of myosin light chain phosphatase by Phos-tag SDS-PAGE. Am J Physiol Cell Physiol 2016; 310:C681-91. [PMID: 26864694 DOI: 10.1152/ajpcell.00327.2015] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2015] [Accepted: 02/08/2016] [Indexed: 01/28/2023]
Abstract
Phosphorylation of the myosin-targeting subunit 1 of myosin light chain phosphatase (MYPT1) plays an important role in the regulation of smooth muscle contraction, and several sites of phosphorylation by different protein Ser/Thr kinases have been identified. Furthermore, in some instances, phosphorylation at specific sites affects phosphorylation at neighboring sites, with functional consequences. Characterization of the complex phosphorylation of MYPT1 in tissue samples at rest and in response to contractile and relaxant stimuli is, therefore, challenging. We have exploited Phos-tag SDS-PAGE in combination with Western blotting using antibodies to MYPT1, including phosphospecific antibodies, to separate multiple phosphorylated MYPT1 species and quantify MYPT1 phosphorylation stoichiometry using purified, full-length recombinant MYPT1 phosphorylated by Rho-associated coiled-coil kinase (ROCK) and cAMP-dependent protein kinase (PKA). This approach confirmed that phosphorylation of MYPT1 by ROCK occurs at Thr(697)and Thr(855), PKA phosphorylates these two sites and the neighboring Ser(696)and Ser(854), and prior phosphorylation at Thr(697)and Thr(855)by ROCK precludes phosphorylation at Ser(696)and Ser(854)by PKA. Furthermore, phosphorylation at Thr(697)and Thr(855)by ROCK exposes two other sites of phosphorylation by PKA. Treatment of Triton-skinned rat caudal arterial smooth muscle strips with the membrane-impermeant phosphatase inhibitor microcystin or treatment of intact tissue with the membrane-permeant phosphatase inhibitor calyculin A induced slow, sustained contractions that correlated with phosphorylation of MYPT1 at 7 to ≥10 sites. Phos-tag SDS-PAGE thus provides a suitable and convenient method for analysis of the complex, multisite MYPT1 phosphorylation events involved in the regulation of myosin light chain phosphatase activity and smooth muscle contraction.
Collapse
Affiliation(s)
- Cindy Sutherland
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Justin A MacDonald
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| | - Michael P Walsh
- Department of Biochemistry and Molecular Biology, Cumming School of Medicine, University of Calgary, Calgary, Alberta, Canada
| |
Collapse
|
31
|
MacDonald JA, Sutherland C, Carlson DA, Bhaidani S, Al-Ghabkari A, Swärd K, Haystead TAJ, Walsh MP. A Small Molecule Pyrazolo[3,4-d]Pyrimidinone Inhibitor of Zipper-Interacting Protein Kinase Suppresses Calcium Sensitization of Vascular Smooth Muscle. Mol Pharmacol 2015; 89:105-17. [DOI: 10.1124/mol.115.100529] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2015] [Accepted: 10/09/2015] [Indexed: 11/22/2022] Open
|
32
|
Hayashi M, Kajioka S, Itsumi M, Takahashi R, Shahab N, Ishigami T, Takeda M, Masuda N, Yamaguchi A, Naito S. Actions of cAMP on calcium sensitization in human detrusor smooth muscle contraction. BJU Int 2015; 117:179-91. [PMID: 25981809 DOI: 10.1111/bju.13180] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
OBJECTIVES To clarify the effect of cAMP on the Ca(2+) -sensitized smooth muscle contraction in human detrusor, as well as the role of novel exchange protein directly activated by cAMP (Epac) in cAMP-mediated relaxation. MATERIALS AND METHODS All experimental protocols to record isometric tension force were performed using α-toxin-permeabilized human detrusor smooth muscle strips. The mechanisms of cAMP-mediated suppression of Ca(2+) sensitization activated by 10 μm carbachol (CCh) and 100 μm GTP were studied using a selective rho kinase (ROK) inhibitor, Y-27632, and a selective protein kinase C (PKC) inhibitor, GF-109203X. The relaxation mechanisms were further probed using a selective protein kinase A (PKA) activator, 6-Bnz-cAMP and a selective Epac activator, 8-pCPT-2'-O-Me-cAMP. RESULTS We observed that CCh-induced Ca(2+) sensitization was inhibited by cAMP in a concentration-dependent manner. GF-109203X (10 μm) but not Y-27632 (10 μm) significantly enhanced the relaxation effect induced by cAMP (100 μm). 6-Bnz-cAMP (100 μm) predominantly decreased the tension force in comparison with 8-pCPT-2'-O-Me-cAMP (100 μm). CONCLUSIONS We showed that cAMP predominantly inhibited the ROK pathway but not the PKC pathway. The PKA-dependent pathway is dominant, while Epac plays a minor role in human detrusor smooth muscle Ca(2+) sensitization.
Collapse
Affiliation(s)
- Maya Hayashi
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Japan
| | - Shunichi Kajioka
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Japan
| | - Momoe Itsumi
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Japan
| | - Ryosuke Takahashi
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Japan
| | - Nouval Shahab
- Department of Urology, Faculty of Medicine and Health Sciences, Syarif Hidayaullah Jakarta State Islamic University, Jakarta, Indonesia
| | - Takao Ishigami
- Urology Research Unit, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Japan
| | - Masahiro Takeda
- Urology Research Unit, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Japan
| | - Noriyuki Masuda
- Innovation and Research Portfolio Planning, Drug Discovery Research, Astellas Pharma Inc., Tsukuba, Japan
| | | | - Seiji Naito
- Department of Urology, Graduate School of Medical Sciences, Kyushu University, Fukuoka City, Japan
| |
Collapse
|
33
|
Zhao Z, Manser E. Myotonic dystrophy kinase-related Cdc42-binding kinases (MRCK), the ROCK-like effectors of Cdc42 and Rac1. Small GTPases 2015; 6:81-8. [PMID: 26090570 DOI: 10.1080/21541248.2014.1000699] [Citation(s) in RCA: 52] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022] Open
Abstract
Cdc42 is a member of the Rho GTPase protein family that plays key roles in local F-actin organization through a number of kinase and non-kinase effector proteins. The myotonic dystrophy kinase-related Cdc42-binding kinases (MRCKs), and the RhoA binding coiled-coil containing kinases (ROCKs) are widely expressed members of the Dystrophia myotonica protein kinase (DMPK) family. The MRCK proteins are ∼190 kDa multi-domain proteins expressed in all cells and coordinate certain acto-myosin networks. Notably MRCK is a key regulator of myosin18A and myosin IIA/B, and through phosphorylation of their common regulatory light chains (MYL9 or MLC2) to promote actin stress fiber contractility. The MRCK kinases are regulated by Cdc42, which is required for cell polarity and directional migration; MRCK links to the acto-myosin complex through interaction with a coiled-coil containing adaptor proteins LRAP35a/b. The biological activities of MRCK in model organisms such as worms and flies confirm it as a myosin II activator. In mammalian cell culture MRCK can be critical for cancer cell migration and neurite outgrowth. We review the current literatures regarding MRCK and highlight the similarities and differences between MRCK and ROCK kinases.
Collapse
Affiliation(s)
- Zhuoshen Zhao
- a sGSK Group; Institute of Molecular and Cell Biology (IMCB) ; Singapore
| | | |
Collapse
|
34
|
Yuen SL, Ogut O, Brozovich FV. Differential phosphorylation of LZ+/LZ- MYPT1 isoforms regulates MLC phosphatase activity. Arch Biochem Biophys 2014; 562:37-42. [PMID: 25168281 DOI: 10.1016/j.abb.2014.08.011] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2014] [Revised: 08/12/2014] [Accepted: 08/17/2014] [Indexed: 02/05/2023]
Abstract
The vascular response to NO is due, in part, to a Ca(2+) independent activation of myosin light chain (MLC) phosphatase, a trimeric enzyme of 20kDa, 38kDa catalytic and 110-130kDa myosin targeting (MYPT1) subunits. Alternative mRNA splicing produces MYPT1 isoforms that differ by the presence or absence of a central insert (CI) and a leucine zipper (LZ), and the presence of a LZ+ MYPT1 isoform is important for protein kinase G (PKG) mediated activation of MLC phosphatase. This study was designed to determine the molecular basis for the differential sensitivity of the vasculature to NO. Our results demonstrate that the presence of the MYPT1 LZ domain is required for PKG to both phosphorylate MYPT1 at S668 and activate MLC phosphatase. Further for LZ+ MYPT1 isoforms, an S668A MYPT1 mutation prevents the PKG mediated, Ca(2+) independent activation of MLC phosphatase. These data demonstrate that differential PKG mediated S668 phosphorylation of LZ+/LZ- MYPT1 isoforms could be important for determining the diversity in the sensitivity of the vasculature to NO mediated vasodilatation. Thus, the relative expression of LZ+/LZ- MYPT1 isoforms, in part, defines the vascular response to NO and NO based vasodilators, and therefore, plays a role in the regulation of vascular tone in both health and disease.
Collapse
Affiliation(s)
- Samantha L Yuen
- Division of Cardiovascular Diseases, Mayo Medical School, Rochester, MN 55905, USA
| | - Ozgur Ogut
- Division of Cardiovascular Diseases, Mayo Medical School, Rochester, MN 55905, USA
| | - Frank V Brozovich
- Division of Cardiovascular Diseases, Mayo Medical School, Rochester, MN 55905, USA.
| |
Collapse
|
35
|
Qiao YN, He WQ, Chen CP, Zhang CH, Zhao W, Wang P, Zhang L, Wu YZ, Yang X, Peng YJ, Gao JM, Kamm KE, Stull JT, Zhu MS. Myosin phosphatase target subunit 1 (MYPT1) regulates the contraction and relaxation of vascular smooth muscle and maintains blood pressure. J Biol Chem 2014; 289:22512-23. [PMID: 24951589 DOI: 10.1074/jbc.m113.525444] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Myosin light chain phosphatase with its regulatory subunit, myosin phosphatase target subunit 1 (MYPT1) modulates Ca(2+)-dependent phosphorylation of myosin light chain by myosin light chain kinase, which is essential for smooth muscle contraction. The role of MYPT1 in vascular smooth muscle was investigated in adult MYPT1 smooth muscle specific knock-out mice. MYPT1 deletion enhanced phosphorylation of myosin regulatory light chain and contractile force in isolated mesenteric arteries treated with KCl and various vascular agonists. The contractile responses of arteries from knock-out mice to norepinephrine were inhibited by Rho-associated kinase (ROCK) and protein kinase C inhibitors and were associated with inhibition of phosphorylation of the myosin light chain phosphatase inhibitor CPI-17. Additionally, stimulation of the NO/cGMP/protein kinase G (PKG) signaling pathway still resulted in relaxation of MYPT1-deficient mesenteric arteries, indicating phosphorylation of MYPT1 by PKG is not a major contributor to the relaxation response. Thus, MYPT1 enhances myosin light chain phosphatase activity sufficient for blood pressure maintenance. Rho-associated kinase phosphorylation of CPI-17 plays a significant role in enhancing vascular contractile responses, whereas phosphorylation of MYPT1 in the NO/cGMP/PKG signaling module is not necessary for relaxation.
Collapse
Affiliation(s)
- Yan-Ning Qiao
- From the Key Laboratory of MOE for Modern Teaching Technology, Shaanxi Normal University, Xi'an 710062, China, Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Wei-Qi He
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Cai-Ping Chen
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Cheng-Hai Zhang
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Wei Zhao
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Pei Wang
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Lin Zhang
- Zhejiang Provincial Key Laboratory for Technology and Application of Model Organisms, School of Life Sciences, Wenzhou Medical College, Wenzhou 325035, China
| | - Yan-Ze Wu
- From the Key Laboratory of MOE for Modern Teaching Technology, Shaanxi Normal University, Xi'an 710062, China
| | - Xiao Yang
- State Key Laboratory of Proteomics, Genetic Laboratory of Development and Disease, Institute of Biotechnology, Beijing 100071, China, and
| | - Ya-Jing Peng
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China
| | - Ji-Min Gao
- Zhejiang Provincial Key Laboratory for Technology and Application of Model Organisms, School of Life Sciences, Wenzhou Medical College, Wenzhou 325035, China
| | - Kristine E Kamm
- the Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9040
| | - James T Stull
- the Department of Physiology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas 75390-9040
| | - Min-Sheng Zhu
- Model Animal Research Center and MOE Key Laboratory of Animal Models of Disease, Nanjing University, Nanjing 210061, China, Zhejiang Provincial Key Laboratory for Technology and Application of Model Organisms, School of Life Sciences, Wenzhou Medical College, Wenzhou 325035, China,
| |
Collapse
|
36
|
Khasnis M, Nakatomi A, Gumpper K, Eto M. Reconstituted human myosin light chain phosphatase reveals distinct roles of two inhibitory phosphorylation sites of the regulatory subunit, MYPT1. Biochemistry 2014; 53:2701-9. [PMID: 24712327 PMCID: PMC4010256 DOI: 10.1021/bi5001728] [Citation(s) in RCA: 55] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
![]()
The myosin light chain phosphatase
(MLCP) is a cytoskeleton-associated
protein phosphatase-1 (PP1) holoenzyme and a RhoA/ROCK effector, regulating
cytoskeletal reorganization. ROCK-induced phosphorylation of the MLCP
regulatory subunit (MYPT1) at two sites, Thr696 and Thr853, suppresses
the activity, although little is known about the difference in the
role. Here, we developed a new method for the preparation of the recombinant
human MLCP complex and determined the molecular and cellular basis
of inhibitory phosphorylation. The recombinant MLCP partially purified
from mammalian cell lysates retained characteristics of the native
enzyme, such that it was fully active without Mn2+ and
sensitive to PP1 inhibitor compounds. Selective thio-phosphorylation
of MYPT1 at Thr696 with ROCK inhibited the MLCP activity 30%, whereas
the Thr853 thio-phosphorylation did not alter the phosphatase activity.
Interference with the docking of phospho-Thr696 at the active site
weakened the inhibition, suggesting selective autoinhibition induced
by phospho-Thr696. Both Thr696 and Thr853 sites underwent autodephosphorylation.
Compared with that of Thr853, phosphorylation of Thr696 was more stable,
and it facilitated Thr853 phosphorylation. Endogenous MYPT1 at Thr696
was spontaneously phosphorylated in quiescent human leiomyosarcoma
cells. Serum stimulation of the cells resulted in dissociation of
MYPT1 from myosin and PP1C in parallel with an increase in the level
of Thr853 phosphorylation. The C-terminal domain of human MYPT1(495–1030)
was responsible for the binding to the N-terminal portion of myosin
light meromyosin. The spontaneous phosphorylation at Thr696 may adjust
the basal activity of cellular MLCP and affect the temporal phosphorylation
at Thr853 that is synchronized with myosin targeting.
Collapse
Affiliation(s)
- Mukta Khasnis
- Department of Molecular Physiology and Biophysics, Thomas Jefferson University Jefferson Medical School , and Kimmel Cancer Center , 1020 Locust Street, Philadelphia, Pennsylvania 19107, United States
| | | | | | | |
Collapse
|
37
|
Turner SR, MacDonald JA. Novel Contributions of the Smoothelin-like 1 Protein in Vascular Smooth Muscle Contraction and its Potential Involvement in Myogenic Tone. Microcirculation 2014; 21:249-58. [DOI: 10.1111/micc.12108] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2013] [Accepted: 11/04/2013] [Indexed: 12/19/2022]
Affiliation(s)
- Sara R. Turner
- The Smooth Muscle Research Group at the Libin Cardiovascular Institute of Alberta; Department of Biochemistry & Molecular Biology; University of Calgary; Calgary Alberta Canada
| | - Justin A. MacDonald
- The Smooth Muscle Research Group at the Libin Cardiovascular Institute of Alberta; Department of Biochemistry & Molecular Biology; University of Calgary; Calgary Alberta Canada
| |
Collapse
|
38
|
Butler T, Paul J, Europe-Finner N, Smith R, Chan EC. Role of serine-threonine phosphoprotein phosphatases in smooth muscle contractility. Am J Physiol Cell Physiol 2013; 304:C485-504. [PMID: 23325405 DOI: 10.1152/ajpcell.00161.2012] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The degree of phosphorylation of myosin light chain 20 (MLC20) is a major determinant of force generation in smooth muscle. Myosin phosphatases (MPs) contain protein phosphatase (PP) 1 as catalytic subunits and are the major enzymes that dephosphorylate MLC20. MP regulatory targeting subunit 1 (MYPT1), the main regulatory subunit of MP in all smooth muscles, is a key convergence point of contractile and relaxatory pathways. Combinations of regulatory mechanisms, including isoform splicing, multiple phosphorylation sites, and scaffolding proteins, modulate MYPT1 activity with tissue and agonist specificities to affect contraction and relaxation. Other members of the PP1 family that do not target myosin, as well as PP2A and PP2B, dephosphorylate a range of proteins that affect smooth muscle contraction. This review discusses the role of phosphatases in smooth muscle contractility with a focus on MYPT1 in uterine smooth muscle. Myometrium shares characteristics of vascular and other visceral smooth muscles yet, during healthy pregnancy, undergoes hypertrophy, hyperplasia, quiescence, and labor as physiological processes. Myometrium presents an accessible model for the study of normal and pathological smooth muscle function, and a better understanding of myometrial physiology may allow the development of novel therapeutics for the many disorders of myometrial physiology from preterm labor to dysmenorrhea.
Collapse
Affiliation(s)
- Trent Butler
- Mothers and Babies Research Centre, Faculty of Health, University of Newcastle, Callaghan, NSW 2308, Australia
| | | | | | | | | |
Collapse
|
39
|
MacDonald JA, Moffat LD, Al-Ghabkari A, Sutherland C, Walsh MP. Prostate-apoptosis response-4 phosphorylation in vascular smooth muscle. Arch Biochem Biophys 2012; 535:84-90. [PMID: 23219599 DOI: 10.1016/j.abb.2012.11.009] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 11/15/2012] [Accepted: 11/21/2012] [Indexed: 12/12/2022]
Abstract
The protein prostate-apoptosis response (Par)-4 has been implicated in the regulation of smooth muscle contraction, based largely on studies with the A7r5 cell line. A mechanism has been proposed whereby Par-4 binding to MYPT1 (the myosin-targeting subunit of myosin light chain phosphatase, MLCP) blocks access of zipper-interacting protein kinase (ZIPK) to Thr697 and Thr855 of MYPT1, whose phosphorylation is associated with MLCP inhibition. Phosphorylation of Par-4 at Thr155 disrupts its interaction with MYPT1, exposing the sites of phosphorylation in MYPT1 and leading to MLCP inhibition and contraction. We tested this "padlock" hypothesis in a well-characterized vascular smooth muscle system, the rat caudal artery. Par-4 was retained in Triton-skinned tissue, suggesting a tight association with the contractile machinery, and indeed Par-4 co-immunoprecipitated with MYPT1. Treatment of Triton-skinned tissue with the phosphatase inhibitor microcystin (MC) evoked phosphorylation of Par-4 at Thr155, but did not induce its dissociation from the contractile machinery. Furthermore, analysis of the time courses of MC-induced phosphorylation of MYPT1 and Par-4 revealed that MYPT1 phosphorylation at Thr697 or Thr855 preceded Par-4 phosphorylation. Par-4 phosphorylation was inhibited by the non-selective kinase inhibitor staurosporine, but not by inhibitors of ZIPK, Rho-associated kinase or protein kinase C. In addition, Par-4 phosphorylation did not occur upon addition of constitutively-active ZIPK to skinned tissue. We conclude that phosphorylation of Par-4 does not regulate contraction of this vascular smooth muscle tissue by inducing dissociation of Par-4 from MYPT1 to allow phosphorylation of MYPT1 and inhibition of MLCP.
Collapse
Affiliation(s)
- Justin A MacDonald
- Smooth Muscle Research Group and Department of Biochemistry & Molecular Biology, University of Calgary, 3280 Hospital Drive NW, Calgary, AB, Canada T2N 4Z6.
| | | | | | | | | |
Collapse
|