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Kirkbride JA, Nilsson GY, Kim JI, Takeya K, Tanaka Y, Tokumitsu H, Suizu F, Eto M. PHI-1, an Endogenous Inhibitor Protein for Protein Phosphatase-1 and a Pan-Cancer Marker, Regulates Raf-1 Proteostasis. Biomolecules 2023; 13:1741. [PMID: 38136612 PMCID: PMC10741526 DOI: 10.3390/biom13121741] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 11/30/2023] [Accepted: 11/30/2023] [Indexed: 12/24/2023] Open
Abstract
Raf-1, a multifunctional kinase, regulates various cellular processes, including cell proliferation, apoptosis, and migration, by phosphorylating MAPK/ERK kinase and interacting with specific kinases. Cellular Raf-1 activity is intricately regulated through pathways involving the binding of regulatory proteins, direct phosphorylation, and the ubiquitin-proteasome axis. In this study, we demonstrate that PHI-1, an endogenous inhibitor of protein phosphatase-1 (PP1), plays a pivotal role in modulating Raf-1 proteostasis within cells. Knocking down endogenous PHI-1 in HEK293 cells using siRNA resulted in increased cell proliferation and reduced apoptosis. This heightened cell proliferation was accompanied by a 15-fold increase in ERK1/2 phosphorylation. Importantly, the observed ERK1/2 hyperphosphorylation was attributable to an upregulation of Raf-1 expression, rather than an increase in Ras levels, Raf-1 Ser338 phosphorylation, or B-Raf levels. The elevated Raf-1 expression, stemming from PHI-1 knockdown, enhanced EGF-induced ERK1/2 phosphorylation through MEK. Moreover, PHI-1 knockdown significantly contributed to Raf-1 protein stability without affecting Raf-1 mRNA levels. Conversely, ectopic PHI-1 expression suppressed Raf-1 protein levels in a manner that correlated with PHI-1's inhibitory potency. Inhibiting PP1 to mimic PHI-1's function using tautomycin led to a reduction in Raf-1 expression. In summary, our findings highlight that the PHI-1-PP1 signaling axis selectively governs Raf-1 proteostasis and cell survival signals.
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Affiliation(s)
- Jason A. Kirkbride
- Department of Molecular Physiology and Biophysics, and Kimmel Cancer Center, Jefferson Medical College, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Garbo Young Nilsson
- Department of Molecular Physiology and Biophysics, and Kimmel Cancer Center, Jefferson Medical College, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
| | - Jee In Kim
- Department of Molecular Physiology and Biophysics, and Kimmel Cancer Center, Jefferson Medical College, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
- Department of Molecular Medicine, Keimyung University School of Medicine, Daegu 42601, Republic of Korea
| | - Kosuke Takeya
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, Okayama University of Science, Imabari 794-8555, Ehime, Japan (Y.T.)
| | - Yoshinori Tanaka
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, Okayama University of Science, Imabari 794-8555, Ehime, Japan (Y.T.)
| | - Hiroshi Tokumitsu
- Applied Cell Biology, Graduate School of Interdisciplinary Science & Engineering in Health Systems, Okayama University, Okayama 700-8530, Okayama, Japan
| | - Futoshi Suizu
- Oncology Pathology, Department of Pathology and Host-Defense, Faculty of Medicine, Kagawa University, Kita-gun 761-0793, Kagawa, Japan;
| | - Masumi Eto
- Department of Molecular Physiology and Biophysics, and Kimmel Cancer Center, Jefferson Medical College, Thomas Jefferson University, 1020 Locust Street, Philadelphia, PA 19107, USA
- Department of Veterinary Medicine, Faculty of Veterinary Medicine, Okayama University of Science, Imabari 794-8555, Ehime, Japan (Y.T.)
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Kirkbride JA, Statuta S. Cotton Mouth In A Cross Country Runner. Med Sci Sports Exerc 2018. [DOI: 10.1249/01.mss.0000535986.81678.02] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Kirkbride JA, Statuta S. Cotton Mouth In A Cross Country Runner. Med Sci Sports Exerc 2018. [DOI: 10.1249/01.mss.0000536701.89161.1c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Eto M, Kirkbride JA, Chugh R, Karikari NK, Kim JI. Nuclear localization of CPI-17, a protein phosphatase-1 inhibitor protein, affects histone H3 phosphorylation and corresponds to proliferation of cancer and smooth muscle cells. Biochem Biophys Res Commun 2013; 434:137-42. [PMID: 23541585 DOI: 10.1016/j.bbrc.2013.03.055] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Accepted: 03/17/2013] [Indexed: 01/23/2023]
Abstract
CPI-17 (C-kinase-activated protein phosphatase-1 (PP1) inhibitor, 17kDa) is a cytoplasmic protein predominantly expressed in mature smooth muscle (SM) that regulates the myosin-associated PP1 holoenzyme (MLCP). Here, we show CPI-17 expression in proliferating cells, such as pancreatic cancer and hyperplastic SM cells. Immunofluorescence showed that CPI-17 was concentrated in nuclei of human pancreatic cancer (Panc1) cells. Nuclear accumulation of CPI-17 was also detected in the proliferating vascular SM cell culture and cells at neointima of rat vascular injury model. The N-terminal 21-residue tail domain of CPI-17 was necessary for the nuclear localization. Phospho-mimetic Asp-substitution of CPI-17 at Ser12 attenuated the nuclear import. CPI-17 phosphorylated at Ser12 was not localized at nuclei, suggesting a suppressive role of Ser12 phosphorylation in the nuclear import. Activated CPI-17 bound to all three isoforms of PP1 catalytic subunit in Panc1 nuclear extracts. CPI-17 knockdown in Panc1 resulted in dephosphorylation of histone H3 at Thr3, Ser10 and Thr11, whereas it had no effects on the phosphorylation of myosin light chain and merlin, the known targets of MLCP. In parallel, CPI-17 knockdown suppressed Panc1 proliferation. We propose that CPI-17 accumulated in the nucleus through the N-terminal tail targets multiple PP1 signaling pathways regulating cell proliferation.
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Affiliation(s)
- Masumi Eto
- Department of Molecular Physiology and Biophysics, and Kimmel Cancer Center, Thomas Jefferson University, 1020 Locust Street, PA 19107, USA.
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Freitas MR, Eto M, Kirkbride JA, Schott C, Sassard J, Stoclet JC. Y27632, a Rho-activated kinase inhibitor, normalizes dysregulation in alpha1-adrenergic receptor-induced contraction of Lyon hypertensive rat artery smooth muscle. Fundam Clin Pharmacol 2009; 23:169-78. [PMID: 19298234 DOI: 10.1111/j.1472-8206.2008.00658.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
RhoA-activated kinase (ROK) is involved in the disorders of smooth muscle contraction found in hypertension model animals and patients. We examined whether the alpha1-adrenergic receptor agonist-induced ROK signal is perturbed in resistance small mesentery artery (SMA) of Lyon genetically hypertensive (LH) rats, using a ROK antagonist, Y27632. Smooth muscle strips of SMA and aorta were isolated from LH and Lyon normotensive (LN) rats. After Ca(2+)-depletion and pre-treatment with phenylephrine (PE), smooth muscle contraction was induced by serial additions of CaCl(2). In LH SMA Ca(2+) permeated cells to a lesser extent as compared with LN SMA, while CaCl(2)-induced contraction of LH SMA was greater than that of LN SMA, indicating a higher ratio of force to Ca(2+) in LH SMA contraction (Ca(2+) sensitization). No hyper-contraction was observed in LH aorta tissues. Treatment of LH SMA with Y27632 restored both Ca(2+) permeability and Ca(2+)-force relationship to levels seen for LN SMA. In response to PE stimulation, phosphorylation of CPI-17, a phosphorylation-dependent myosin phosphatase inhibitor protein, and MYPT1 at Thr853, the inhibitory phosphorylation site of the myosin phosphatase regulatory subunit, was increased in LN SMA, but remained unchanged in LH SMA. These results suggest that the disorder in ROK-dependent Ca(2+) permeability and Ca(2+)-force relationship is responsible for LH SMA hyper-contraction. Unlike other hypertensive models, the ROK-induced hyper-contractility of LH SMA is independent of MYPT1 and CPI-17 phosphorylation, which suggests that ROK-mediated inhibition of myosin phosphatase does not affect SMA hyper-contractility in LH SMA cells.
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Affiliation(s)
- Maria Regina Freitas
- Pharmacologie et Physico-chimie des Interactions Cellulaires et Moléculaires, UMR CNRS 7034, Université Louis Pasteur de Strasbourg, Faculté de Pharmacie, Illkirch-Cedex, France
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Eto M, Kirkbride JA, Brautigan DL. Assembly of MYPT1 with protein phosphatase-1 in fibroblasts redirects localization and reorganizes the actin cytoskeleton. ACTA ACUST UNITED AC 2008; 62:100-9. [PMID: 16106448 DOI: 10.1002/cm.20088] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Dephosphorylation of actin-binding proteins by a specialized form of protein Ser/Thr phosphatase type-1 (PP1) regulates smooth muscle contraction and morphology and motility of nonmuscle cells. This myosin and ezrin/radixin/moesin (ERM)-targeted phosphatase comprises the delta isoform PP1 catalytic subunit plus a primary regulatory subunit called myosin phosphatase targeting (MYPT1). We reconstructed myosin/ERM phosphatase in living rat embryo fibroblasts (REF52 cells) by transient expression of epitope-tagged MYPT1 (myc-MYPT1) plus HA-tagged PP1. Unexpectedly, wild-type myc-MYPT1 expressed alone accumulated predominantly in the nucleus, as visualized by immunofluorescent microscopy, whereas if coexpressed with HA-PP1, it was localized in the cytosol and deposited on cytoskeleton myofilaments. The F38A mutation of MYPT1 that eliminates PP1 binding gave nuclear localization of myc-MYPT1, even when coexpressed with HA-PP1. Thus, expression of both subunits was necessary to form myosin/ERM phosphatase in situ and mediate myofilament localization. The results indicate there is little endogenous PP1 available for interaction or interchange with ectopic regulatory subunits in living cells. We concluded that myosin binding by the C-terminal domain of MYPT1 is not sufficient to override nuclear import in fibroblasts, but the binding of PP1 to myc-MYPT1 neutralizes nuclear import. Full-length myc-MYPT1 plus HA-PP1 induced only subtle changes in organization of the actin cytoskeleton, however coexpression of myc-MYPT1(1-300) with HA-PP1 dispersed stress fibers without major alteration in morphology and myc-MYPT1(1-498) disrupted the cytoskeleton and produced radically extended cells that appeared like neurons. Based on these responses, we conclude that the MYPT1 C-terminus functions as an auto-inhibitory domain, and a central domain in MYPT1 can mediate extensive reorganization of the actin cytoskeleton.
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Affiliation(s)
- Masumi Eto
- Department of Molecular Physiology and Biological Physics, Center for Cell Signaling, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA
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Eto M, Kitazawa T, Matsuzawa F, Aikawa SI, Kirkbride JA, Isozumi N, Nishimura Y, Brautigan DL, Ohki SY. Phosphorylation-induced conformational switching of CPI-17 produces a potent myosin phosphatase inhibitor. Structure 2007; 15:1591-602. [PMID: 18073109 PMCID: PMC2217667 DOI: 10.1016/j.str.2007.10.014] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2007] [Revised: 10/02/2007] [Accepted: 10/03/2007] [Indexed: 11/17/2022]
Abstract
Phosphorylation of endogenous inhibitor proteins for type-1 Ser/Thr phosphatase (PP1) provides a mechanism for reciprocal coordination of kinase and phosphatase activities. A myosin phosphatase inhibitor protein CPI-17 is phosphorylated at Thr38 through G-protein-mediated signals, resulting in a >1000-fold increase in inhibitory potency. We show here the solution NMR structure of phospho-T38-CPI-17 with rmsd of 0.36 +/- 0.06 A for the backbone secondary structure, which reveals how phosphorylation triggers a conformational change and exposes an inhibitory surface. This active conformation is stabilized by the formation of a hydrophobic core of intercalated side chains, which is not formed in a phospho-mimetic D38 form of CPI-17. Thus, the profound increase in potency of CPI-17 arises from phosphorylation, conformational change, and hydrophobic stabilization of a rigid structure that poses the phosphorylated residue on the protein surface and restricts its hydrolysis by myosin phosphatase. Our results provide structural insights into transduction of kinase signals by PP1 inhibitor proteins.
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Affiliation(s)
- Masumi Eto
- Department of Molecular Physiology and Biophysics, Thomas Jefferson University, 1020 Locust Street, Philadelphia, Pennsylvania 19107, USA
| | - Toshio Kitazawa
- Boston Biomedical Research Institute, 64 Grove Street, Watertown, Massachusetts, USA
| | - Fumiko Matsuzawa
- Dept Clinical Genetics, Tokyo Metropolitan Institute of Medical Science, Honkomagome 3-18-22, Bunkyo-ku, Tokyo 113-8613, Japan
| | - Sei-ichi Aikawa
- Dept Clinical Genetics, Tokyo Metropolitan Institute of Medical Science, Honkomagome 3-18-22, Bunkyo-ku, Tokyo 113-8613, Japan
| | - Jason A. Kirkbride
- Department of Molecular Physiology and Biophysics, Thomas Jefferson University, 1020 Locust Street, Philadelphia, Pennsylvania 19107, USA
| | - Noriyoshi Isozumi
- Center for Nano Materials and Technology (CNMT), Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Tatsunokuchi, Ishikawa, 923-1292, Japan
| | - Yumi Nishimura
- Center for Nano Materials and Technology (CNMT), Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Tatsunokuchi, Ishikawa, 923-1292, Japan
| | - David L. Brautigan
- Center for Cell Signaling, University of Virginia School of Medicine, 1400 Jefferson Park Avenue, Charlottesville, Virginia 22908, USA
| | - Shin-ya Ohki
- Center for Nano Materials and Technology (CNMT), Japan Advanced Institute of Science and Technology (JAIST), 1-1 Asahidai, Tatsunokuchi, Ishikawa, 923-1292, Japan
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Eto M, Kitazawa T, Matsuzawa F, Aikawa S, Kirkbride JA, Isozumi N, Nishimura Y, Brautigan DL, Ohki S. Structural insight into regulation of myosin phosphatase by CPI‐17. FASEB J 2007. [DOI: 10.1096/fasebj.21.5.a520] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Masumi Eto
- Thomas Jefferson Univ1020 Locust StPhiladelphiaPA19107
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