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Bartol TM, Ordyan M, Sejnowski TJ, Rangamani P, Kennedy MB. A spatial model of autophosphorylation of Ca 2+ /calmodulin-dependent protein kinase II in a glutamatergic spine reveals dynamics of kinase activation in the first several seconds after a complex synaptic stimulus. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.02.578696. [PMID: 38352446 PMCID: PMC10862815 DOI: 10.1101/2024.02.02.578696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 02/23/2024]
Abstract
Long-term potentiation (LTP) is a biochemical process in excitatory glutamatergic synapses in the Central Nervous System (CNS). It is initiated by a bout of synaptic activation that is strong enough to contribute to production of an action potential in the axon of the postsynaptic neuron, and it results in an increase in the size of postsynaptic depolarization during subsequent activity. The first step leading to LTP is activation and autophosphorylation of an abundant postsynaptic enzyme, Ca 2+ /calmodulin-dependent protein kinase II (CaMKII). We use simulation of activation of CaMKII holoenzymes in a realistic spatial model of a spine synapse, created in MCell4, to test three hypotheses about how the autophosphorylation response of CaMKII is shaped during a repeated high-frequency stimulus. First, the simulation results indicate that autophosphorylation of CaMKII does not constitute a bistable switch under biologically realistic conditions. Instead, prolonged autophosphorylation of CaMKII may contribute to a biochemical "kinetic proof-reading" mechanism that controls induction of synaptic plasticity. Second, concentration of CaMKII near the postsynaptic membrane increases the local concentration of kinase activity. However, neither localization nor "Ca 2+ -calmodulin-trapping (CaM-trapping)" increase the proportion of autophosphorylated subunits in holoenzymes after a complex stimulus, as previously hypothesized. Finally, we show that, as hypothesized, the amplitude of autophosphorylation in the first 30 seconds after a stimulus is extremely sensitive to the level and location of PP1 activity when PP1 is present in biologically accurate amounts. We further show that prolonged steric hindrance of dephosphorylation of CaMKII, caused by CaM-trapping, can increase the amplitude of autophosphorylation after a complex stimulus. These simulation results sharpen our quantitative understanding of the early events leading to LTP at excitatory synapses. Author Summary Neurons in the brain are interconnected in an organized fashion by synapses that transmit neuronal activity from one neuron to another. Most of the billions of neurons in the brain have about 10,000 synapses spread over the neuronal membrane. Information is stored in the brain when the ability of specific synapses to pass along neuronal activity is strengthened resulting in formation of new networks. The increase in strength of a synapse is tightly controlled by the frequency and amplitude of its activity, and by neurohormonal signals, which, in combination, can cause long-lasting biochemical changes at the synapse that underlie learning and memory. Defects in these biochemical pathways cause mental and neurological diseases. To develop treatments, we need to understand the precise choreography of these critical biochemical changes. However, the tiny size of the synaptic compartment makes precise measurements of the biochemical reactions impossible. We have used computer simulation techniques and information gathered from experiments on purified synaptic proteins to simulate, within a single synapse, the choreography of the first biochemical step in synaptic strengthening: activation of the enzyme Ca 2+ / calmodulin-dependent protein kinase II. Our results provide insights that can be used in future studies to develop treatments for neuronal diseases.
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Padi SKR, Vos MR, Godek RJ, Fuller JR, Kruse T, Hein JB, Nilsson J, Kelker MS, Page R, Peti W. Cryo-EM structures of PP2A:B55-FAM122A and PP2A:B55-ARPP19. Nature 2024; 625:195-203. [PMID: 38123684 PMCID: PMC10765524 DOI: 10.1038/s41586-023-06870-3] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2023] [Accepted: 11/15/2023] [Indexed: 12/23/2023]
Abstract
Progression through the cell cycle is controlled by regulated and abrupt changes in phosphorylation1. Mitotic entry is initiated by increased phosphorylation of mitotic proteins, a process driven by kinases2, whereas mitotic exit is achieved by counteracting dephosphorylation, a process driven by phosphatases, especially PP2A:B553. Although the role of kinases in mitotic entry is well established, recent data have shown that mitosis is only successfully initiated when the counterbalancing phosphatases are also inhibited4. Inhibition of PP2A:B55 is achieved by the intrinsically disordered proteins ARPP195,6 and FAM122A7. Despite their critical roles in mitosis, the mechanisms by which they achieve PP2A:B55 inhibition is unknown. Here, we report the single-particle cryo-electron microscopy structures of PP2A:B55 bound to phosphorylated ARPP19 and FAM122A. Consistent with our complementary NMR spectroscopy studies, both intrinsically disordered proteins bind PP2A:B55, but do so in highly distinct manners, leveraging multiple distinct binding sites on B55. Our extensive structural, biophysical and biochemical data explain how substrates and inhibitors are recruited to PP2A:B55 and provide a molecular roadmap for the development of therapeutic interventions for PP2A:B55-related diseases.
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Affiliation(s)
- Sathish K R Padi
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Margaret R Vos
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Rachel J Godek
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | | | - Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jamin B Hein
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | | | - Rebecca Page
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA.
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA.
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3
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Choy MS, Srivastava G, Robinson LC, Tatchell K, Page R, Peti W. The SDS22:PP1:I3 complex: SDS22 binding to PP1 loosens the active site metal to prime metal exchange. J Biol Chem 2024; 300:105515. [PMID: 38042495 PMCID: PMC10776994 DOI: 10.1016/j.jbc.2023.105515] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2023] [Revised: 11/20/2023] [Accepted: 11/22/2023] [Indexed: 12/04/2023] Open
Abstract
SDS22 and Inhibitor-3 (I3) are two ancient regulators of protein phosphatase 1 (PP1) that regulate multiple essential biological processes. Both SDS22 and I3 form stable dimeric complexes with PP1; however, and atypically for PP1 regulators, they also form a triple complex, where both proteins bind to PP1 simultaneously (SPI complex). Here we report the crystal structure of the SPI complex. While both regulators bind PP1 in conformations identical to those observed in their individual PP1 complexes, PP1 adopts the SDS22-bound conformation, which lacks its M1 metal. Unexpectedly, surface plasmon resonance (SPR) revealed that the affinity of I3 for the SDS22:PP1 complex is ∼10-fold lower than PP1 alone. We show that this change in binding affinity is solely due to the interaction of I3 with the PP1 active site, specifically PP1's M2 metal, demonstrating that SDS22 likely allows for PP1 M2 metal exchange and thus PP1 biogenesis.
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Affiliation(s)
- Meng S Choy
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut, USA
| | - Gautam Srivastava
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut, USA
| | - Lucy C Robinson
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
| | - Kelly Tatchell
- Department of Biochemistry and Molecular Biology, Louisiana State University Health Sciences Center, Shreveport, Louisiana, USA
| | - Rebecca Page
- Department of Cell Biology, University of Connecticut Health Center, Farmington, Connecticut, USA.
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, Connecticut, USA.
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4
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Hicks D, Giresh K, Wrischnik LA, Weiser DC. The PPP1R15 Family of eIF2-alpha Phosphatase Targeting Subunits (GADD34 and CReP). Int J Mol Sci 2023; 24:17321. [PMID: 38139150 PMCID: PMC10743859 DOI: 10.3390/ijms242417321] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Revised: 12/01/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023] Open
Abstract
The vertebrate PPP1R15 family consists of the proteins GADD34 (growth arrest and DNA damage-inducible protein 34, the product of the PPP1R15A gene) and CReP (constitutive repressor of eIF2α phosphorylation, the product of the PPP1R15B gene), both of which function as targeting/regulatory subunits for protein phosphatase 1 (PP1) by regulating subcellular localization, modulating substrate specificity and assembling complexes with target proteins. The primary cellular function of these proteins is to facilitate the dephosphorylation of eukaryotic initiation factor 2-alpha (eIF2α) by PP1 during cell stress. In this review, we will provide a comprehensive overview of the cellular function, biochemistry and pharmacology of GADD34 and CReP, starting with a brief introduction of eIF2α phosphorylation via the integrated protein response (ISR). We discuss the roles GADD34 and CReP play as feedback inhibitors of the unfolded protein response (UPR) and highlight the critical function they serve as inhibitors of the PERK-dependent branch, which is particularly important since it can mediate cell survival or cell death, depending on how long the stressful stimuli lasts, and GADD34 and CReP play key roles in fine-tuning this cellular decision. We briefly discuss the roles of GADD34 and CReP homologs in model systems and then focus on what we have learned about their function from knockout mice and human patients, followed by a brief review of several diseases in which GADD34 and CReP have been implicated, including cancer, diabetes and especially neurodegenerative disease. Because of the potential importance of GADD34 and CReP in aspects of human health and disease, we will discuss several pharmacological inhibitors of GADD34 and/or CReP that show promise as treatments and the controversies as to their mechanism of action. This review will finish with a discussion of the biochemical properties of GADD34 and CReP, their regulation and the additional interacting partners that may provide insight into the roles these proteins may play in other cellular pathways. We will conclude with a brief outline of critical areas for future study.
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Affiliation(s)
- Danielle Hicks
- Department of Science, Mathematics and Engineering, Modesto Junior College, Modesto, CA 95350, USA
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
| | - Krithika Giresh
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
| | - Lisa A. Wrischnik
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
| | - Douglas C. Weiser
- Department of Biological Sciences, University of the Pacific, Stockton, CA 95211, USA
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5
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Padi SK, Vos MR, Godek RJ, Fuller JR, Kruse T, Hein JB, Nilsson J, Kelker MS, Page R, Peti W. Cryo-EM structures of PP2A:B55-FAM122A and PP2A:B55-ARPP19. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.08.31.555365. [PMID: 37693408 PMCID: PMC10491220 DOI: 10.1101/2023.08.31.555365] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 09/12/2023]
Abstract
Progression through the cell cycle is controlled by regulated and abrupt changes in phosphorylation.1 Mitotic entry is initiated by increased phosphorylation of mitotic proteins, a process driven by kinases,2 while mitotic exit is achieved by counteracting dephosphorylation, a process driven by phosphatases, especially PP2A:B55.3 While the role of kinases in mitotic entry is well-established, recent data have shown that mitosis is only successfully initiated when the counterbalancing phosphatases are also inhibited.4 For PP2A:B55, inhibition is achieved by the two intrinsically disordered proteins (IDPs), ARPP19 (phosphorylation-dependent)6,7 and FAM122A5 (inhibition is phosphorylation-independent). Despite their critical roles in mitosis, the mechanisms by which they achieve PP2A:B55 inhibition is unknown. Here, we report the cryo-electron microscopy structures of PP2A:B55 bound to phosphorylated ARPP19 and FAM122A. Consistent with our complementary NMR spectroscopy studies both IDPs bind PP2A:B55, but do so in highly distinct manners, unexpectedly leveraging multiple distinct binding sites on B55. Our extensive structural, biophysical and biochemical data explain how substrates and inhibitors are recruited to PP2A:B55 and provides a molecular roadmap for the development of therapeutic interventions for PP2A:B55 related diseases.
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Affiliation(s)
- Sathish K.R. Padi
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, USA
| | - Margaret R. Vos
- Department of Cell Biology, University of Connecticut Health Center, Farmington, USA
| | - Rachel J. Godek
- Department of Cell Biology, University of Connecticut Health Center, Farmington, USA
| | | | - Thomas Kruse
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jamin B. Hein
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | - Jakob Nilsson
- The Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark
| | | | - Rebecca Page
- Department of Cell Biology, University of Connecticut Health Center, Farmington, USA
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, USA
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6
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Srivastava G, Choy MS, Bolik-Coulon N, Page R, Peti W. Inhibitor-3 inhibits Protein Phosphatase 1 via a metal binding dynamic protein-protein interaction. Nat Commun 2023; 14:1798. [PMID: 37002212 PMCID: PMC10066265 DOI: 10.1038/s41467-023-37372-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2022] [Accepted: 02/21/2023] [Indexed: 04/03/2023] Open
Abstract
To achieve substrate specificity, protein phosphate 1 (PP1) forms holoenzymes with hundreds of regulatory and inhibitory proteins. Inhibitor-3 (I3) is an ancient inhibitor of PP1 with putative roles in PP1 maturation and the regulation of PP1 activity. Here, we show that I3 residues 27-68 are necessary and sufficient for PP1 binding and inhibition. In addition to a canonical RVxF motif, which is shared by nearly all PP1 regulators and inhibitors, and a non-canonical SILK motif, I3 also binds PP1 via multiple basic residues that bind directly in the PP1 acidic substrate binding groove, an interaction that provides a blueprint for how substrates bind this groove for dephosphorylation. Unexpectedly, this interaction positions a CCC (cys-cys-cys) motif to bind directly across the PP1 active site. Using biophysical and inhibition assays, we show that the I3 CCC motif binds and inhibits PP1 in an unexpected dynamic, fuzzy manner, via transient engagement of the PP1 active site metals. Together, these data not only provide fundamental insights into the mechanisms by which IDP protein regulators of PP1 achieve inhibition, but also shows that fuzzy interactions between IDPs and their folded binding partners, in addition to enhancing binding affinity, can also directly regulate enzyme activity.
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Affiliation(s)
- Gautam Srivastava
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Meng S Choy
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA
| | - Nicolas Bolik-Coulon
- Department of Chemistry and Biochemistry, University of Arizona, Tucson, AZ, USA
| | - Rebecca Page
- Department of Cell Biology, University of Connecticut Health Center, Farmington, CT, USA
| | - Wolfgang Peti
- Department of Molecular Biology and Biophysics, University of Connecticut Health Center, Farmington, CT, USA.
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7
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Foley K, Ward N, Hou H, Mayer A, McKee C, Xia H. Regulation of PP1 interaction with I-2, neurabin, and F-actin. Mol Cell Neurosci 2023; 124:103796. [PMID: 36442541 PMCID: PMC10038014 DOI: 10.1016/j.mcn.2022.103796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2022] [Revised: 11/16/2022] [Accepted: 11/21/2022] [Indexed: 11/27/2022] Open
Abstract
Reversible phosphorylation is a fundamental regulatory mechanism required for many biological processes and is coordinated by the opposing actions of protein kinases and phosphatases. Protein phosphatase 1 (PP1) is a major protein phosphatase that plays an important role in many fundamental physiological processes including synaptic transmission and memory formation. Here we investigate the regulation of PP1 by prominent signaling proteins and synaptic scaffolds including GSK3β, inhibitor-2 (I-2), neurabin (Nrb), and actin. While GSK3β is known to regulate PP1 via phosphorylation of the PP1-binding protein I-2, we found that GSK3β directly regulates PP1 via inhibitory phosphorylation in neurons. Additionally, using bioluminescence resonance energy transfer (BRET), we found that GSK3β alters PP1-I-2 interaction in living cells. The effect of GSK3β on PP1-I-2 interaction is independent of the PP1 C-terminal tail, contrary to predictions based on previous findings from purified proteins. I-2 has been shown to form a trimeric complex with PP1 and Nrb, a major synaptic scaffold for promoting PP1 localization to the actin cytoskeleton. Utilizing BRET, we found that Nrb promotes PP1-actin interaction, however no BRET was detected between I-2 and F-actin. Finally, we found that stabilizing F-actin promotes Nrb-PP1 binding and may also lead to conformational changes between Nrb-I-2 and Nrb-F-actin complexes. Overall, our findings elaborate the dynamic regulation of PP1 complexes by GSK3β, targeting proteins, and actin polymerization.
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Affiliation(s)
- Karl Foley
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA; Department of Neuroscience, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Nancy Ward
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Hailong Hou
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Abigail Mayer
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA; Department of Neuroscience, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Cody McKee
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA; Department of Neuroscience, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Houhui Xia
- Department of Pharmacology and Physiology, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA; Department of Neuroscience, School of Medicine and Dentistry, University of Rochester Medical Center, Rochester, NY 14642, USA.
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8
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Foley K, Altimimi H, Hou H, Zhang Y, McKee C, Papasergi-Scott MM, Yang H, Mayer A, Ward N, MacLean DM, Nairn AC, Stellwagen D, Xia H. Protein phosphatase-1 inhibitor-2 promotes PP1γ positive regulation of synaptic transmission. Front Synaptic Neurosci 2022; 14:1021832. [PMID: 36276179 PMCID: PMC9582336 DOI: 10.3389/fnsyn.2022.1021832] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 09/09/2022] [Indexed: 11/13/2022] Open
Abstract
Inhibitor-2 (I-2) is a prototypic inhibitor of protein phosphatase-1 (PP1), a major serine-threonine phosphatase that regulates synaptic plasticity and learning and memory. Although I-2 is a potent inhibitor of PP1 in vitro, our previous work has elucidated that, in vivo, I-2 may act as a positive regulator of PP1. Here we show that I-2 and PP1γ, but not PP1α, positively regulate synaptic transmission in hippocampal neurons. Moreover, we demonstrated that I-2 enhanced PP1γ interaction with its major synaptic scaffold, neurabin, by Förster resonance energy transfer (FRET)/Fluorescence lifetime imaging microscopy (FLIM) studies, while having a limited effect on PP1 auto-inhibitory phosphorylation. Furthermore, our study indicates that the effect of I-2 on PP1 activity in vivo is dictated by I-2 threonine-72 phosphorylation. Our work thus demonstrates a molecular mechanism by which I-2 positively regulates PP1 function in synaptic transmission.
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Verdugo-Sivianes EM, Carnero A. SPINOPHILIN: a multiplayer tumor suppressor. Genes Dis 2022; 10:187-198. [PMID: 37013033 PMCID: PMC10066247 DOI: 10.1016/j.gendis.2021.12.021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2021] [Accepted: 12/24/2021] [Indexed: 02/07/2023] Open
Abstract
SPINOPHILIN (SPN, PPP1R9B or NEURABIN-2) is a multifunctional protein that regulates protein-protein interactions in different cell signaling pathways. SPN is also one of the regulatory subunits of protein phosphatase 1 (PP1), implicated in the dephosphorylation of retinoblastoma protein (pRB) during cell cycle. The SPN gene has been described as a tumor suppressor in different human tumor contexts, in which low levels of SPN are correlated with a higher grade and worse prognosis. In addition, mutations of the SPN protein have been reported in human tumors. Recently, an oncogenic mutation of SPN, A566V, was described, which affects both the SPN-PP1 interaction and the phosphatase activity of the holoenzyme, and promotes p53-dependent tumorigenesis by increasing the cancer stem cell (CSC) pool in breast tumors. Thus, the loss or mutation of SPN could be late events that promotes tumor progression by increasing the CSC pool and, eventually, the malignant behavior of the tumor.
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Regulation of Synaptic Transmission and Plasticity by Protein Phosphatase 1. J Neurosci 2021; 41:3040-3050. [PMID: 33827970 DOI: 10.1523/jneurosci.2026-20.2021] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Revised: 02/08/2021] [Accepted: 02/09/2021] [Indexed: 01/22/2023] Open
Abstract
Protein phosphatases, by counteracting protein kinases, regulate the reversible phosphorylation of many substrates involved in synaptic plasticity, a cellular model for learning and memory. A prominent phosphatase regulating synaptic plasticity and neurologic disorders is the serine/threonine protein phosphatase 1 (PP1). PP1 has three isoforms (α, β, and γ, encoded by three different genes), which are regulated by a vast number of interacting subunits that define their enzymatic substrate specificity. In this review, we discuss evidence showing that PP1 regulates synaptic transmission and plasticity, as well as presenting novel models of PP1 regulation suggested by recent experimental evidence. We also outline the required targeting of PP1 by neurabin and spinophilin to achieve substrate specificity at the synapse to regulate AMPAR and NMDAR function. We then highlight the role of inhibitor-2 in regulating PP1 function in plasticity, including its positive regulation of PP1 function in vivo in memory formation. We also discuss the distinct function of the three PP1 isoforms in synaptic plasticity and brain function, as well as briefly discuss the role of inhibitory phosphorylation of PP1, which has received recent emphasis in the regulation of PP1 activity in neurons.
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11
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Protein phosphatase-1: dual activity regulation by Inhibitor-2. Biochem Soc Trans 2020; 48:2229-2240. [DOI: 10.1042/bst20200503] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2020] [Revised: 09/15/2020] [Accepted: 09/16/2020] [Indexed: 01/12/2023]
Abstract
Inhibitor-2 (I2) ranks amongst the most ancient regulators of protein phosphatase-1 (PP1). It is a small, intrinsically disordered protein that was originally discovered as a potent inhibitor of PP1. However, later investigations also characterized I2 as an activator of PP1 as well as a chaperone for PP1 folding. Numerous studies disclosed the importance of I2 for diverse cellular processes but did not describe a unifying molecular principle of PP1 regulation. We have re-analyzed the literature on I2 in the light of current insights of PP1 structure and regulation. Extensive biochemical data, largely ignored in the recent I2 literature, provide substantial indirect evidence for a role of I2 as a loader of active-site metals. In addition, I2 appears to function as a competitive inhibitor of PP1 in higher eukaryotes. The published data also demonstrate that several segments of I2 that remain unstructured in the PP1 : I2 complex are in fact essential for PP1 regulation. Together, the available data identify I2 as a dynamic activity-modulator of PP1.
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Glutamate-responsive translation of dendritic GSK3β mRNA triggers a cycle for amplification of reactivated preexisting GSK3β that is indispensable for tau hyperphosphorylation. Neurochem Int 2020; 139:104808. [DOI: 10.1016/j.neuint.2020.104808] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2020] [Revised: 06/11/2020] [Accepted: 07/07/2020] [Indexed: 01/13/2023]
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13
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Lang I, Virk G, Zheng DC, Young J, Nguyen MJ, Amiri R, Fong M, Arata A, Chadaideh KS, Walsh S, Weiser DC. The Evolution of Duplicated Genes of the Cpi-17/Phi-1 ( ppp1r14) Family of Protein Phosphatase 1 Inhibitors in Teleosts. Int J Mol Sci 2020; 21:ijms21165709. [PMID: 32784920 PMCID: PMC7460850 DOI: 10.3390/ijms21165709] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2020] [Accepted: 08/07/2020] [Indexed: 11/29/2022] Open
Abstract
The Cpi-17 (ppp1r14) gene family is an evolutionarily conserved, vertebrate specific group of protein phosphatase 1 (PP1) inhibitors. When phosphorylated, Cpi-17 is a potent inhibitor of myosin phosphatase (MP), a holoenzyme complex of the regulatory subunit Mypt1 and the catalytic subunit PP1. Myosin phosphatase dephosphorylates the regulatory myosin light chain (Mlc2) and promotes actomyosin relaxation, which in turn, regulates numerous cellular processes including smooth muscle contraction, cytokinesis, cell motility, and tumor cell invasion. We analyzed zebrafish homologs of the Cpi-17 family, to better understand the mechanisms of myosin phosphatase regulation. We found single homologs of both Kepi (ppp1r14c) and Gbpi (ppp1r14d) in silico, but we detected no expression of these genes during early embryonic development. Cpi-17 (ppp1r14a) and Phi-1 (ppp1r14b) each had two duplicate paralogs, (ppp1r14aa and ppp1r14ab) and (ppp1r14ba and ppp1r14bb), which were each expressed during early development. The spatial expression pattern of these genes has diverged, with ppp1r14aa and ppp1r14bb expressed primarily in smooth muscle and skeletal muscle, respectively, while ppp1r14ab and ppp1r14ba are primarily expressed in neural tissue. We observed that, in in vitro and heterologous cellular systems, the Cpi-17 paralogs both acted as potent myosin phosphatase inhibitors, and were indistinguishable from one another. In contrast, the two Phi-1 paralogs displayed weak myosin phosphatase inhibitory activity in vitro, and did not alter myosin phosphorylation in cells. Through deletion and chimeric analysis, we identified that the difference in specificity for myosin phosphatase between Cpi-17 and Phi-1 was encoded by the highly conserved PHIN (phosphatase holoenzyme inhibitory) domain, and not the more divergent N- and C- termini. We also showed that either Cpi-17 paralog can rescue the knockdown phenotype, but neither Phi-1 paralog could do so. Thus, we provide new evidence about the biochemical and developmental distinctions of the zebrafish Cpi-17 protein family.
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Affiliation(s)
- Irene Lang
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Guneet Virk
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Dale C. Zheng
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Jason Young
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Michael J. Nguyen
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Rojin Amiri
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Michelle Fong
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Alisa Arata
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
| | - Katia S. Chadaideh
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
- Department of Human Evolutionary Biology, Harvard University, Cambridge, MA 02138, USA
| | - Susan Walsh
- Life Sciences, Soka University of America, Aliso Viejo, CA 92656, USA;
| | - Douglas C. Weiser
- Department of Biological Sciences, University of the Pacific, Stockton, CA 98211, USA; (I.L.); (G.V.); (D.C.Z.); (J.Y.); (M.J.N.); (R.A.); (M.F.); (A.A.); (K.S.C.)
- Correspondence: ; Tel.: +1-209-946-2955
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14
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Casamayor A, Ariño J. Controlling Ser/Thr protein phosphatase PP1 activity and function through interaction with regulatory subunits. ADVANCES IN PROTEIN CHEMISTRY AND STRUCTURAL BIOLOGY 2020; 122:231-288. [PMID: 32951813 DOI: 10.1016/bs.apcsb.2020.06.004] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protein phosphatase 1 is a major Ser/Thr protein phosphatase activity in eukaryotic cells. It is composed of a catalytic polypeptide (PP1C), with little substrate specificity, that interacts with a large variety of proteins of diverse structure (regulatory subunits). The diversity of holoenzymes that can be formed explain the multiplicity of cellular functions under the control of this phosphatase. In quite a few cases, regulatory subunits have an inhibitory role, downregulating the activity of the phosphatase. In this chapter we shall introduce PP1C and review the most relevant families of PP1C regulatory subunits, with particular emphasis in describing the structural basis for their interaction.
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Affiliation(s)
- Antonio Casamayor
- Institut de Biotecnologia i Biomedicina & Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola, del Vallès, Spain
| | - Joaquín Ariño
- Institut de Biotecnologia i Biomedicina & Departament de Bioquímica i Biologia Molecular, Universitat Autònoma de Barcelona, Cerdanyola, del Vallès, Spain
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15
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Salek AB, Edler MC, McBride JP, Baucum AJ. Spinophilin regulates phosphorylation and interactions of the GluN2B subunit of the N-methyl-d-aspartate receptor. J Neurochem 2019; 151:185-203. [PMID: 31325175 DOI: 10.1111/jnc.14831] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2019] [Revised: 06/21/2019] [Accepted: 07/13/2019] [Indexed: 12/20/2022]
Abstract
N-methyl-d-Aspartate receptors (NMDARs) are abundant postsynaptic proteins that are critical for normal synaptic communication. NMDAR channel function is regulated by multiple properties, including phosphorylation. Inhibition of protein phosphatase 1 (PP1) in hippocampal neurons increases NMDAR activity, an effect abrogated by loss of spinophilin, the major PP1-targeting protein in the postsynaptic density. However, how spinophilin regulates PP1-dependent NMDAR function is unclear. We hypothesize that spinophilin regulates PP1 binding to the NMDAR to alter NMDAR phosphorylation. Our data demonstrate that spinophilin interacts with the GluN2B subunit of the NMDAR. In human embryonic kidney 293 FT cells, activation and/or overexpression of protein kinase A increased the association between spinophilin and the GluN2B subunit of the NMDAR. Functionally, we found that spinophilin overexpression decreased PP1 binding to the GluN2B subunit of the NMDAR and attenuated the PP1-dependent dephosphorylation of GluN2B at Ser-1284. Moreover, in P28 hippocampal lysates isolated from spinophilin KO compared to WT mice, there was increased binding of GluN2B to PP1, decreased phosphorylation of GluN2B at Ser-1284, and altered GluN2B protein interactions with postsynaptic density-enriched proteins. Together, our data demonstrate that spinophilin decreases PP1 binding to GluN2B and concomitantly enhances the phosphorylation of GluN2B at Ser-1284. The putative consequences of these spinophilin-dependent alterations in GluN2B phosphorylation and interactions on synaptic GluN2B localization and function are discussed. Open Science: This manuscript was awarded with the Open Materials Badge For more information see: https://cos.io/our-services/open-science-badges/.
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Affiliation(s)
- Asma B Salek
- Department of Biology, Indiana University-Purdue University, Indianapolis, Indiana, USA
| | - Michael C Edler
- Department of Biology, Indiana University-Purdue University, Indianapolis, Indiana, USA.,Department of Medical and Molecular Genetics, Indiana University School of Medicine, Indianapolis, Indiana, USA
| | - Jonathon P McBride
- Department of Biology, Indiana University-Purdue University, Indianapolis, Indiana, USA
| | - Anthony J Baucum
- Department of Biology, Indiana University-Purdue University, Indianapolis, Indiana, USA.,Stark Neurosciences Research Institute, Indiana University School of Medicine, Indianapolis, Indiana, USA.,Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, Indiana, USA
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16
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Brautigan DL, Shenolikar S. Protein Serine/Threonine Phosphatases: Keys to Unlocking Regulators and Substrates. Annu Rev Biochem 2019; 87:921-964. [PMID: 29925267 DOI: 10.1146/annurev-biochem-062917-012332] [Citation(s) in RCA: 110] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Protein serine/threonine phosphatases (PPPs) are ancient enzymes, with distinct types conserved across eukaryotic evolution. PPPs are segregated into types primarily on the basis of the unique interactions of PPP catalytic subunits with regulatory proteins. The resulting holoenzymes dock substrates distal to the active site to enhance specificity. This review focuses on the subunit and substrate interactions for PPP that depend on short linear motifs. Insights about these motifs from structures of holoenzymes open new opportunities for computational biology approaches to elucidate PPP networks. There is an expanding knowledge base of posttranslational modifications of PPP catalytic and regulatory subunits, as well as of their substrates, including phosphorylation, acetylation, and ubiquitination. Cross talk between these posttranslational modifications creates PPP-based signaling. Knowledge of PPP complexes, signaling clusters, as well as how PPPs communicate with each other in response to cellular signals should unlock the doors to PPP networks and signaling "clouds" that orchestrate and coordinate different aspects of cell physiology.
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Affiliation(s)
- David L Brautigan
- Center for Cell Signaling and Department of Microbiology, Immunology and Cancer Biology, University of Virginia School of Medicine, Charlottesville, Virginia 22908, USA;
| | - Shirish Shenolikar
- Signature Research Programs in Cardiovascular and Metabolic Disorders and Neuroscience and Behavioral Disorders, Duke-NUS Medical School, Singapore 169857
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17
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Moura M, Conde C. Phosphatases in Mitosis: Roles and Regulation. Biomolecules 2019; 9:E55. [PMID: 30736436 PMCID: PMC6406801 DOI: 10.3390/biom9020055] [Citation(s) in RCA: 47] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/17/2018] [Revised: 01/31/2019] [Accepted: 02/01/2019] [Indexed: 02/07/2023] Open
Abstract
Mitosis requires extensive rearrangement of cellular architecture and of subcellular structures so that replicated chromosomes can bind correctly to spindle microtubules and segregate towards opposite poles. This process originates two new daughter nuclei with equal genetic content and relies on highly-dynamic and tightly regulated phosphorylation of numerous cell cycle proteins. A burst in protein phosphorylation orchestrated by several conserved kinases occurs as cells go into and progress through mitosis. The opposing dephosphorylation events are catalyzed by a small set of protein phosphatases, whose importance for the accuracy of mitosis is becoming increasingly appreciated. This review will focus on the established and emerging roles of mitotic phosphatases, describe their structural and biochemical properties, and discuss recent advances in understanding the regulation of phosphatase activity and function.
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Affiliation(s)
- Margarida Moura
- IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde da Universidade do Porto, 4200-135, Porto, Portugal.
- Programa Doutoral em Biologia Molecular e Celular (MCbiology), Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, 4050-313 Porto, Portugal.
| | - Carlos Conde
- IBMC-Instituto de Biologia Molecular e Celular, Universidade do Porto, 4200-135 Porto, Portugal.
- i3S-Instituto de Investigação e Inovação em Saúde da Universidade do Porto, 4200-135, Porto, Portugal.
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18
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Ferreira M, Beullens M, Bollen M, Van Eynde A. Functions and therapeutic potential of protein phosphatase 1: Insights from mouse genetics. BIOCHIMICA ET BIOPHYSICA ACTA. MOLECULAR CELL RESEARCH 2019; 1866:16-30. [PMID: 30056088 PMCID: PMC7114192 DOI: 10.1016/j.bbamcr.2018.07.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/08/2018] [Revised: 07/16/2018] [Accepted: 07/19/2018] [Indexed: 02/07/2023]
Abstract
Protein phosphatase 1 (PP1) catalyzes more than half of all phosphoserine/threonine dephosphorylation reactions in mammalian cells. In vivo PP1 does not exist as a free catalytic subunit but is always associated with at least one regulatory PP1-interacting protein (PIP) to generate a large set of distinct holoenzymes. Each PP1 complex controls the dephosphorylation of only a small subset of PP1 substrates. We screened the literature for genetically engineered mouse models and identified models for all PP1 isoforms and 104 PIPs. PP1 itself and at least 49 PIPs were connected to human disease-associated phenotypes. Additionally, phenotypes related to 17 PIPs were clearly linked to altered PP1 function, while such information was lacking for 32 other PIPs. We propose structural reverse genetics, which combines structural characterization of proteins with mouse genetics, to identify new PP1-related therapeutic targets. The available mouse models confirm the pleiotropic action of PP1 in health and diseases.
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Affiliation(s)
- Mónica Ferreira
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Monique Beullens
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Mathieu Bollen
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium
| | - Aleyde Van Eynde
- Laboratory of Biosignaling & Therapeutics, KU Leuven Department of Cellular and Molecular Medicine, University of Leuven, B-3000 Leuven, Belgium.
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19
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McElroy SL, Winham SJ, Cuellar-Barboza AB, Colby CL, Ho AMC, Sicotte H, Larrabee BR, Crow S, Frye MA, Biernacka JM. Bipolar disorder with binge eating behavior: a genome-wide association study implicates PRR5-ARHGAP8. Transl Psychiatry 2018; 8:40. [PMID: 29391396 PMCID: PMC5804024 DOI: 10.1038/s41398-017-0085-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 09/06/2017] [Accepted: 09/13/2017] [Indexed: 12/30/2022] Open
Abstract
Bipolar disorder (BD) is associated with binge eating behavior (BE), and both conditions are heritable. Previously, using data from the Genetic Association Information Network (GAIN) study of BD, we performed genome-wide association (GWA) analyses of BD with BE comorbidity. Here, utilizing data from the Mayo Clinic BD Biobank (969 BD cases, 777 controls), we performed a GWA analysis of a BD subtype defined by BE, and case-only analysis comparing BD subjects with and without BE. We then performed a meta-analysis of the Mayo and GAIN results. The meta-analysis provided genome-wide significant evidence of association between single nucleotide polymorphisms (SNPs) in PRR5-ARHGAP8 and BE in BD cases (rs726170 OR = 1.91, P = 3.05E-08). In the meta-analysis comparing cases with BD with comorbid BE vs. non-BD controls, a genome-wide significant association was observed at SNP rs111940429 in an intergenic region near PPP1R2P5 (p = 1.21E-08). PRR5-ARHGAP8 is a read-through transcript resulting in a fusion protein of PRR5 and ARHGAP8. PRR5 encodes a subunit of mTORC2, a serine/threonine kinase that participates in food intake regulation, while ARHGAP8 encodes a member of the RhoGAP family of proteins that mediate cross-talk between Rho GTPases and other signaling pathways. Without BE information in controls, it is not possible to determine whether the observed association reflects a risk factor for BE in general, risk for BE in individuals with BD, or risk of a subtype of BD with BE. The effect of PRR5-ARHGAP8 on BE risk thus warrants further investigation.
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Affiliation(s)
- Susan L McElroy
- Lindner Center of HOPE, Mason, OH, USA
- Department of Psychiatry and Behavioral Neuroscience, University of Cincinnati, Cincinnati, OH, USA
| | - Stacey J Winham
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | | | - Colin L Colby
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Ada Man-Choi Ho
- Department of Molecular Pharmacology and Experimental Therapeutics, Mayo Clinic, Rochester, MN, USA
| | - Hugues Sicotte
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Beth R Larrabee
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA
| | - Scott Crow
- University of Minnesota, Minneapolis, MN, USA
| | - Mark A Frye
- Department of Psychiatry and Psychology, Mayo Clinic, Rochester, MN, USA
| | - Joanna M Biernacka
- Department of Health Sciences Research, Mayo Clinic, Rochester, MN, USA.
- Department of Psychiatry and Psychology, Mayo Clinic, Rochester, MN, USA.
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20
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Hiday AC, Edler MC, Salek AB, Morris CW, Thang M, Rentz TJ, Rose KL, Jones LM, Baucum AJ. Mechanisms and Consequences of Dopamine Depletion-Induced Attenuation of the Spinophilin/Neurofilament Medium Interaction. Neural Plast 2017; 2017:4153076. [PMID: 28634551 PMCID: PMC5467389 DOI: 10.1155/2017/4153076] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2017] [Accepted: 02/16/2017] [Indexed: 12/12/2022] Open
Abstract
Signaling changes that occur in the striatum following the loss of dopamine neurons in the Parkinson disease (PD) are poorly understood. While increases in the activity of kinases and decreases in the activity of phosphatases have been observed, the specific consequences of these changes are less well understood. Phosphatases, such as protein phosphatase 1 (PP1), are highly promiscuous and obtain substrate selectivity via targeting proteins. Spinophilin is the major PP1-targeting protein enriched in the postsynaptic density of striatal dendritic spines. Spinophilin association with PP1 is increased concurrent with decreases in PP1 activity in an animal model of PD. Using proteomic-based approaches, we observed dopamine depletion-induced decreases in spinophilin binding to multiple protein classes in the striatum. Specifically, there was a decrease in the association of spinophilin with neurofilament medium (NF-M) in dopamine-depleted striatum. Using a heterologous cell line, we determined that spinophilin binding to NF-M required overexpression of the catalytic subunit of protein kinase A and was decreased by cyclin-dependent protein kinase 5. Functionally, we demonstrate that spinophilin can decrease NF-M phosphorylation. Our data determine mechanisms that regulate, and putative consequences of, pathological changes in the association of spinophilin with NF-M that are observed in animal models of PD.
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Affiliation(s)
- Andrew C. Hiday
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
| | - Michael C. Edler
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
| | - Asma B. Salek
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
| | - Cameron W. Morris
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
- Neuroscience Undergraduate Program, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
| | - Morrent Thang
- Department of Psychology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
| | - Tyler J. Rentz
- Molecular Physiology and Biophysics, Vanderbilt University School of Medicine University, 724 Robinson Research Building, 23rd Ave South at Pierce, Nashville, TN 37232, USA
| | - Kristie L. Rose
- Department of Biochemistry and the Mass Spectrometry Research Center, Vanderbilt University School of Medicine University, 465 21st Ave S. Room 9160, MRB III, Nashville, TN 37232, USA
| | - Lisa M. Jones
- Department of Chemistry and Chemical Biology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
| | - Anthony J. Baucum
- Department of Biology, Indiana University-Purdue University Indianapolis, 723 W. Michigan St., Indianapolis, IN 46202, USA
- Molecular Physiology and Biophysics, Vanderbilt University School of Medicine University, 724 Robinson Research Building, 23rd Ave South at Pierce, Nashville, TN 37232, USA
- Stark Neurosciences Research Institute, Indiana University School of Medicine, Indiana, IN, USA
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21
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Rebelo S, Santos M, Martins F, da Cruz e Silva EF, da Cruz e Silva OA. Protein phosphatase 1 is a key player in nuclear events. Cell Signal 2015; 27:2589-98. [DOI: 10.1016/j.cellsig.2015.08.007] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2015] [Revised: 07/31/2015] [Accepted: 08/10/2015] [Indexed: 12/17/2022]
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22
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Liu R, Correll RN, Davis J, Vagnozzi RJ, York AJ, Sargent MA, Nairn AC, Molkentin JD. Cardiac-specific deletion of protein phosphatase 1β promotes increased myofilament protein phosphorylation and contractile alterations. J Mol Cell Cardiol 2015; 87:204-13. [PMID: 26334248 PMCID: PMC4637224 DOI: 10.1016/j.yjmcc.2015.08.018] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Revised: 08/21/2015] [Accepted: 08/24/2015] [Indexed: 12/27/2022]
Abstract
There are 3 protein phosphatase 1 (PP1) catalytic isoforms (α, β and γ) encoded within the mammalian genome. These 3 gene products share ~90% amino acid homology within their catalytic domains but each has unique N- and C-termini that likely underlie distinctive subcellular localization or functionality. In this study, we assessed the effect associated with the loss of each PP1 isoform in the heart using a conditional Cre-loxP targeting approach in mice. Ppp1ca-loxP, Ppp1cb-loxP and Ppp1cc-loxP alleles were crossed with either an Nkx2.5-Cre knock-in containing allele for early embryonic deletion or a tamoxifen inducible α-myosin heavy chain (αMHC)-MerCreMer transgene for adult and cardiac-specific deletion. We determined that while deletion of Ppp1ca (PP1α) or Ppp1cc (PP1γ) had little effect on the whole heart, deletion of Ppp1cb (PP1β) resulted in concentric remodeling of the heart, interstitial fibrosis and contractile dysregulation, using either the embryonic or adult-specific Cre-expressing alleles. However, myocytes isolated from Ppp1cb deleted hearts surprisingly showed enhanced contractility. Mechanistically we found that deletion of any of the 3 PP1 gene-encoding isoforms had no effect on phosphorylation of phospholamban, nor were Ca(2+) handling dynamics altered in adult myocytes from Ppp1cb deleted hearts. However, the loss of Ppp1cb from the heart, but not Ppp1ca or Ppp1cc, resulted in elevated phosphorylation of myofilament proteins such as myosin light chain 2 and cardiac myosin binding protein C, consistent with an enriched localization profile of this isoform to the sarcomeres. These results suggest a unique functional role for the PP1β isoform in affecting cardiac contractile function.
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Affiliation(s)
- Ruijie Liu
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - Robert N Correll
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - Jennifer Davis
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - Ronald J Vagnozzi
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - Allen J York
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - Michelle A Sargent
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA
| | - Angus C Nairn
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06520 USA
| | - Jeffery D Molkentin
- Department of Pediatrics, University of Cincinnati, Cincinnati Children's Hospital Medical Center, Howard Hughes Medical Institute, Cincinnati, OH 45229, USA.
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23
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Hou H, Sun L, Siddoway BA, Petralia RS, Yang H, Gu H, Nairn AC, Xia H. Synaptic NMDA receptor stimulation activates PP1 by inhibiting its phosphorylation by Cdk5. ACTA ACUST UNITED AC 2013; 203:521-35. [PMID: 24189275 PMCID: PMC3824016 DOI: 10.1083/jcb.201303035] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Synaptic stimulation promotes proteasome-dependent degradation of p35, inactivation of Cdk5, and decreased phosphorylation of PP1, allowing PP1 to act in the induction of long-term depression. The serine/threonine protein phosphatase protein phosphatase 1 (PP1) is known to play an important role in learning and memory by mediating local and downstream aspects of synaptic signaling, but how PP1 activity is controlled in different forms of synaptic plasticity remains unknown. We find that synaptic N-methyl-d-aspartate (NMDA) receptor stimulation in neurons leads to activation of PP1 through a mechanism involving inhibitory phosphorylation at Thr320 by Cdk5. Synaptic stimulation led to proteasome-dependent degradation of the Cdk5 regulator p35, inactivation of Cdk5, and increased auto-dephosphorylation of Thr320 of PP1. We also found that neither inhibitor-1 nor calcineurin were involved in the control of PP1 activity in response to synaptic NMDA receptor stimulation. Rather, the PP1 regulatory protein, inhibitor-2, formed a complex with PP1 that was controlled by synaptic stimulation. Finally, we found that inhibitor-2 was critical for the induction of long-term depression in primary neurons. Our work fills a major gap regarding the regulation of PP1 in synaptic plasticity.
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Affiliation(s)
- Hailong Hou
- Neuroscience Center, LSU Health Science Center, New Orleans, LA 70112
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24
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Abstract
PP1 (protein phosphatase 1) is an essential serine/threonine phosphatase that plays a critical role in a broad range of biological processes, from muscle contraction to memory formation. PP1 achieves its biological specificity by forming holoenzymes with more than 200 known regulatory proteins. Interestingly, most of these regulatory proteins (≥ 70%) belong to the class of IDPs (intrinsically disordered proteins). Thus structural studies highlighting the interaction of these IDP regulatory proteins with PP1 are an attractive model system because it allows general parameters for a group of diverse IDPs that interact with the same binding partner to be identified, while also providing fundamental insights into PP1 biology. The present review provides a brief overview of our current understanding of IDP-PP1 interactions, including the importance of pre-formed secondary and tertiary structures for PP1 binding, as well as changes of IDP dynamics upon interacting with PP1.
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25
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Esteves SLC, Korrodi-Gregório L, Cotrim CZ, van Kleeff PJM, Domingues SC, da Cruz e Silva OAB, Fardilha M, da Cruz e Silva EF. Protein phosphatase 1γ isoforms linked interactions in the brain. J Mol Neurosci 2012; 50:179-97. [PMID: 23080069 DOI: 10.1007/s12031-012-9902-6] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2012] [Accepted: 10/03/2012] [Indexed: 01/03/2023]
Abstract
Posttranslational protein modifications, in particular reversible protein phosphorylation, are important regulatory mechanisms involved in cellular signaling transduction pathways. Thousands of human proteins are phosphorylatable and the tight regulation of phosphorylation states is crucial for cell maintenance and development. Protein phosphorylation occurs primarily on serine, threonine, and tyrosine residues, through the antagonistic actions of protein kinases and phosphatases. The catalytic subunit of protein phosphatase 1 (PP1), a major Ser/Thr-phosphatase, associates with a large variety of regulatory subunits that define substrate specificity and determine specific cellular pathway responses. PP1 has been shown to bind to different proteins in the brain in order to execute key and differential functions. This work reports the identification of proteins expressed in the human brain that interact with PP1γ1 and PP1γ2 isoforms by the yeast two-hybrid method. An extensive search of PP1-binding motifs was performed for the proteins identified, revealing already known PP1 regulators but also novel interactors. Moreover, our results were integrated with the data of PP1γ interacting proteins from several public web databases, permitting the development of physical maps of the novel interactions. The PP1γ interactome thus obtained allowed for the identification of novel PP1 interacting proteins, supporting novel functions of PP1γ isoforms in the human brain.
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Affiliation(s)
- Sara L C Esteves
- Signal Transduction Laboratory, Centre for Cell Biology, Biology Department, University of Aveiro, 3810-193 Aveiro, Portugal
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Selective expression of KCNS3 potassium channel α-subunit in parvalbumin-containing GABA neurons in the human prefrontal cortex. PLoS One 2012; 7:e43904. [PMID: 22937123 PMCID: PMC3427167 DOI: 10.1371/journal.pone.0043904] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/29/2012] [Accepted: 07/27/2012] [Indexed: 11/25/2022] Open
Abstract
The cognitive deficits of schizophrenia appear to be associated with altered cortical GABA neurotransmission in the subsets of inhibitory neurons that express either parvalbumin (PV) or somatostatin (SST). Identification of molecular mechanisms that operate selectively in these neurons is essential for developing targeted therapeutic strategies that do not influence other cell types. Consequently, we sought to identify, in the human cortex, gene products that are expressed selectively by PV and/or SST neurons, and that might contribute to their distinctive functional properties. Based on previously reported expression patterns in the cortex of mice and humans, we selected four genes: KCNS3, LHX6, KCNAB1, and PPP1R2, encoding K+ channel Kv9.3 modulatory α-subunit, LIM homeobox protein 6, K+ channel Kvβ1 subunit, and protein phosphatase 1 regulatory subunit 2, respectively, and examined their colocalization with PV or SST mRNAs in the human prefrontal cortex using dual-label in situ hybridization with 35S- and digoxigenin-labeled antisense riboprobes. KCNS3 mRNA was detected in almost all PV neurons, but not in SST neurons, and PV mRNA was detected in >90% of KCNS3 mRNA-expressing neurons. LHX6 mRNA was detected in almost all PV and >90% of SST neurons, while among all LHX6 mRNA-expressing neurons 50% expressed PV mRNA and >44% expressed SST mRNA. KCNAB1 and PPP1R2 mRNAs were detected in much larger populations of cortical neurons than PV or SST neurons. These findings indicate that KCNS3 is a selective marker of PV neurons, whereas LHX6 is expressed by both PV and SST neurons. KCNS3 and LHX6 might be useful for characterizing cell-type specific molecular alterations of cortical GABA neurotransmission and for the development of novel treatments targeting PV and/or SST neurons in schizophrenia.
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Abstract
This review traces the historical origins and conceptual developments leading to the current state of knowledge of the three superfamilies of protein Ser/Thr phosphatases. 'PR enzyme' was identified as an enzyme that inactivates glycogen phosphorylase, although it took 10 years before this ugly duckling was recognized for its true identity as a protein Ser/Thr phosphatase. Ethanol denaturation for purification in the 1970s yielded a phosphatase that exhibited broad specificity, which was resolved into type-1 and type-2 phosphatases in the 1980s. More recent developments show that regulation and specificity are achieved through assembly of multisubunit holoenzymes, transient phosphorylation and the action of inhibitor proteins. Still not widely appreciated, there are hundreds of discrete protein Ser/Thr phosphatases available to counteract protein kinases, offering potential therapeutic targets. Signalling networks and modelling schemes need to incorporate the full gamut of protein Ser/Thr phosphatases and their interconnections.
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Affiliation(s)
- David L Brautigan
- Department of Microbiology, Immunology and Cancer Biology, Center for Cell Signaling, University of Virginia, School of Medicine, Charlottesville, VA 22908, USA.
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Abstract
The ubiquitous serine/threonine protein phosphatase 1 (PP1) regulates diverse, essential cellular processes such as cell cycle progression, protein synthesis, muscle contraction, carbohydrate metabolism, transcription and neuronal signaling. However, the free catalytic subunit of PP1, while an effective enzyme, lacks substrate specificity. Instead, it depends on a diverse set of regulatory proteins (≥ 200) to confer specificity towards distinct substrates. Here, we discuss recent advances in structural studies of PP1 holoenzyme complexes and summarize the new insights these studies have provided into the molecular basis of PP1 regulation and specificity.
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Affiliation(s)
- Wolfgang Peti
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI 02912, USA.
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Baucum AJ, Strack S, Colbran RJ. Age-dependent targeting of protein phosphatase 1 to Ca2+/calmodulin-dependent protein kinase II by spinophilin in mouse striatum. PLoS One 2012; 7:e31554. [PMID: 22348105 PMCID: PMC3278457 DOI: 10.1371/journal.pone.0031554] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2011] [Accepted: 01/11/2012] [Indexed: 12/02/2022] Open
Abstract
Mechanisms underlying age-dependent changes of dendritic spines on striatal medium spiny neurons are poorly understood. Spinophilin is an F-actin- and protein phosphatase 1 (PP1)-binding protein that targets PP1 to multiple downstream effectors to modulate dendritic spine morphology and function. We found that calcium/calmodulin-dependent protein kinase II (CaMKII) directly and indirectly associates with N- and C-terminal domains of spinophilin, but F-actin can displace CaMKII from the N-terminal domain. Spinophilin co-localizes PP1 with CaMKII on the F-actin cytoskeleton in heterologous cells, and spinophilin co-localizes with synaptic CaMKII in neuronal cultures. Thr286 autophosphorylation enhances the binding of CaMKII to spinophilin in vitro and in vivo. Although there is no change in total levels of Thr286 autophosphorylation, maturation from postnatal day 21 into adulthood robustly enhances the levels of CaMKII that co-immunoprecipitate with spinophilin from mouse striatal extracts. Moreover, N- and C-terminal domain fragments of spinophilin bind more CaMKII from adult vs. postnatal day 21 striatal lysates. Total levels of other proteins that interact with C-terminal domains of spinophilin decrease during maturation, perhaps reducing competition for CaMKII binding to the C-terminal domain. In contrast, total levels of α-internexin and binding of α-internexin to the spinophilin N-terminal domain increases with maturation, perhaps bridging an indirect interaction with CaMKII. Moreover, there is an increase in the levels of myosin Va, α-internexin, spinophilin, and PP1 in striatal CaMKII immune complexes isolated from adult and aged mice compared to those from postnatal day 21. These changes in spinophilin/CaMKII interactomes may contribute to changes in striatal dendritic spine density, morphology, and function during normal postnatal maturation and aging.
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Affiliation(s)
- Anthony J Baucum
- Department of Molecular Physiology and Biophysics, Vanderbilt-Kennedy Center, Center for Molecular Neuroscience, Vanderbilt University School of Medicine, Nashville, Tennessee, United States of America.
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Sami F, Smet-Nocca C, Khan M, Landrieu I, Lippens G, Brautigan DL. Molecular basis for an ancient partnership between prolyl isomerase Pin1 and phosphatase inhibitor-2. Biochemistry 2011; 50:6567-78. [PMID: 21714498 DOI: 10.1021/bi200553e] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Pin1 is a prolyl isomerase that recognizes phosphorylated Ser/Thr-Pro sites, and phosphatase inhibitor-2 (I-2) is phosphorylated during mitosis at a PSpTP site that is expected to be a Pin1 substrate. However, we previously discovered I-2, but not phospho-I-2, bound to Pin1 as an allosteric modifier of Pin1 substrate specificity [Li, M., et al. (2008) Biochemistry 47, 292]. Here, we use binding assays and NMR spectroscopy to map the interactions on Pin1 and I-2 to elucidate the organization of this complex. Despite having sequences that are ∼50% identical, human, Xenopus, and Drosophila I-2 proteins all exhibited identical, saturable binding to GST-Pin1 with K(0.5) values of 0.3 μM. The (1)H-(15)N heteronuclear single-quantum coherence spectra for both the WW domain and isomerase domain of Pin1 showed distinctive shifts upon addition of I-2. Conversely, as shown by NMR spectroscopy, specific regions of I-2 were affected by addition of Pin1. A single-residue I68A substitution in I-2 weakened binding to Pin1 by half and essentially eliminated binding to the isolated WW domain. On the other hand, truncation of I-2 to residue 152 had a minimal effect on binding to the WW domain but eliminated binding to the isomerase domain. Size exclusion chromatography revealed that wild-type I-2 and Pin1 formed a large (>300 kDa) complex and I-2(I68A) formed a complex of half the size that we propose are a heterotetramer and a heterodimer, respectively. Pin1 and I-2 are conserved among eukaryotes from yeast to humans, and we propose they make up an ancient partnership that provides a means for regulating Pin1 specificity and function.
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Affiliation(s)
- Furqan Sami
- Center for Cell Signaling and Department of Microbiology, University of Virginia School of Medicine, Box 800577-MSB7225, Charlottesville, Virginia 22908, United States
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Dancheck B, Ragusa MJ, Allaire M, Nairn AC, Page R, Peti W. Molecular investigations of the structure and function of the protein phosphatase 1-spinophilin-inhibitor 2 heterotrimeric complex. Biochemistry 2011; 50:1238-46. [PMID: 21218781 PMCID: PMC3040262 DOI: 10.1021/bi101774g] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Regulation of the major Ser/Thr phosphatase protein phosphatase 1 (PP1) is controlled by a diverse array of targeting and inhibitor proteins. Though many PP1 regulatory proteins share at least one PP1 binding motif, usually the RVxF motif, it was recently discovered that certain pairs of targeting and inhibitor proteins bind PP1 simultaneously to form PP1 heterotrimeric complexes. To date, structural information for these heterotrimeric complexes and, in turn, how they direct PP1 activity is entirely lacking. Using a combination of NMR spectroscopy, biochemistry, and small-angle X-ray scattering (SAXS), we show that major structural rearrangements in both spinophilin (targeting) and inhibitor 2 (I-2, inhibitor) are essential for the formation of the heterotrimeric PP1-spinophilin-I-2 (PSI) complex. The RVxF motif of I-2 is released from PP1 during the formation of PSI, making the less prevalent SILK motif of I-2 essential for complex stability. The release of the I-2 RVxF motif allows for enhanced flexibility of both I-2 and spinophilin in the heterotrimeric complex. In addition, we used inductively coupled plasma atomic emission spectroscopy to show that PP1 contains two metals in both heterodimeric complexes (PP1-spinophilin and PP1-I-2) and PSI, demonstrating that PSI retains the biochemical characteristics of the PP1-I-2 holoenzyme. Finally, we combined the NMR and biochemical data with SAXS and molecular dynamics simulations to generate a structural model of the full heterotrimeric PSI complex. Collectively, these data reveal the molecular events that enable PP1 heterotrimeric complexes to exploit both the targeting and inhibitory features of the PP1-regulatory proteins to form multifunctional PP1 holoenzymes.
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Affiliation(s)
- Barbara Dancheck
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI, 02912, USA
| | - Michael J. Ragusa
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Marc Allaire
- National Synchrotron Light Source, Brookhaven National Laboratory, Upton, NY, 11973, USA
| | - Angus C. Nairn
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT, 06511, USA
| | - Rebecca Page
- Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University, Providence, RI, 02912, USA
| | - Wolfgang Peti
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI, 02912, USA
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Fardilha M, Esteves SLC, Korrodi-Gregório L, Pelech S, da Cruz E Silva OAB, da Cruz E Silva E. Protein phosphatase 1 complexes modulate sperm motility and present novel targets for male infertility. Mol Hum Reprod 2011; 17:466-77. [PMID: 21257602 DOI: 10.1093/molehr/gar004] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Infertility is a growing concern in modern society, with 30% of cases being due to male factors, namely reduced sperm concentration, decreased motility and abnormal morphology. Sperm cells are highly compartmentalized, almost devoid of transcription and translation consequently processes such as protein phosphorylation provide a key general mechanism for regulating vital cellular functions, more so than for undifferentiated cells. Reversible protein phosphorylation is the principal mechanism regulating most physiological processes in eukaryotic cells. To date, hundreds of protein kinases have been identified, but significantly fewer phosphatases (PPs) are responsible for counteracting their action. This discrepancy can be explained in part by the mechanism used to control phosphatase activity, which is based on regulatory interacting proteins. This is particularly true for PP1, a major serine/threonine-PP, for which >200 interactors (PP1 interacting proteins-PIPs) have been indentified that control its activity, subcellular location and substrate specificity. For PP1, several isoforms have been described, among them PP1γ2, a testis/sperm-enriched PP1 isoform. Recent findings support our hypothesis that PP1γ2 is involved in the regulation of sperm motility. This review summarizes the known sperm-specific PP1-PIPs, involved in the acquisition of mammalian sperm motility. The complexes that PP1 routinely forms with different proteins are addressed and the role of PP1/A-kinase anchoring protein complexes in sperm motility is considered. Furthermore, the potential relevance of targeting PP1-PIPs complexes to infertility diagnostics and therapeutics as well as to male contraception is also discussed.
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Affiliation(s)
- Margarida Fardilha
- Signal Transduction Laboratory, Centre for Cell Biology, Health Sciences Department and Biology Department, University of Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal.
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Cannon JF. Function of protein phosphatase-1, Glc7, in Saccharomyces cerevisiae. ADVANCES IN APPLIED MICROBIOLOGY 2010; 73:27-59. [PMID: 20800758 DOI: 10.1016/s0065-2164(10)73002-1] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Budding yeast, Saccharomyces cerevisiae, and its close relatives are unique among eukaryotes in having a single gene, GLC7, encoding protein phosphatase-1 (PP1). This enzyme with a highly conserved amino acid sequence controls many processes in all eukaryotic cells. Therefore, the study of Glc7 function offers a unique opportunity to gain a comprehensive understanding of this critical regulatory enzyme. This review summarizes our current knowledge of how Glc7 function modulates processes in the cytoplasm and nucleus. Additionally, global Glc7 regulation is described.
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Affiliation(s)
- John F Cannon
- Department of Molecular Microbiology and Immunology, University of Missouri, Columbia, Missouri, USA.
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Bollen M, Peti W, Ragusa MJ, Beullens M. The extended PP1 toolkit: designed to create specificity. Trends Biochem Sci 2010; 35:450-8. [PMID: 20399103 DOI: 10.1016/j.tibs.2010.03.002] [Citation(s) in RCA: 381] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Revised: 03/03/2010] [Accepted: 03/04/2010] [Indexed: 01/03/2023]
Abstract
Protein Ser/Thr phosphatase-1 (PP1) catalyzes the majority of eukaryotic protein dephosphorylation reactions in a highly regulated and selective manner. Recent studies have identified an unusually diversified PP1 interactome with the properties of a regulatory toolkit. PP1-interacting proteins (PIPs) function as targeting subunits, substrates and/or inhibitors. As targeting subunits, PIPs contribute to substrate selection by bringing PP1 into the vicinity of specific substrates and by modulating substrate specificity via additional substrate docking sites or blocking substrate-binding channels. Many of the nearly 200 established mammalian PIPs are predicted to be intrinsically disordered, a property that facilitates their binding to a large surface area of PP1 via multiple docking motifs. These novel insights offer perspectives for the therapeutic targeting of PP1 by interfering with the binding of PIPs or substrates.
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Affiliation(s)
- Mathieu Bollen
- Laboratory of Biosignaling & Therapeutics, Department of Molecular Cell Biology, University of Leuven, B-3000 Leuven, Belgium.
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35
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Baucum AJ, Jalan-Sakrikar N, Jiao Y, Gustin RM, Carmody LC, Tabb DL, Ham AJL, Colbran RJ. Identification and validation of novel spinophilin-associated proteins in rodent striatum using an enhanced ex vivo shotgun proteomics approach. Mol Cell Proteomics 2010; 9:1243-59. [PMID: 20124353 DOI: 10.1074/mcp.m900387-mcp200] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
Spinophilin regulates excitatory postsynaptic function and morphology during development by virtue of its interactions with filamentous actin, protein phosphatase 1, and a plethora of additional signaling proteins. To provide insight into the roles of spinophilin in mature brain, we characterized the spinophilin interactome in subcellular fractions solubilized from adult rodent striatum by using a shotgun proteomics approach to identify proteins in spinophilin immune complexes. Initial analyses of samples generated using a mouse spinophilin antibody detected 23 proteins that were not present in an IgG control sample; however, 12 of these proteins were detected in complexes isolated from spinophilin knock-out tissue. A second screen using two different spinophilin antibodies and either knock-out or IgG controls identified a total of 125 proteins. The probability of each protein being specifically associated with spinophilin in each sample was calculated, and proteins were ranked according to a chi(2) analysis of the probabilities from analyses of multiple samples. Spinophilin and the known associated proteins neurabin and multiple isoforms of protein phosphatase 1 were specifically detected. Multiple, novel, spinophilin-associated proteins (myosin Va, calcium/calmodulin-dependent protein kinase II, neurofilament light polypeptide, postsynaptic density 95, alpha-actinin, and densin) were then shown to interact with GST fusion proteins containing fragments of spinophilin. Additional biochemical and transfected cell imaging studies showed that alpha-actinin and densin directly interact with residues 151-300 and 446-817, respectively, of spinophilin. Taken together, we have developed a multi-antibody, shotgun proteomics approach to characterize protein interactomes in native tissues, delineating the importance of knock-out tissue controls and providing novel insights into the nature and function of the spinophilin interactome in mature striatum.
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Affiliation(s)
- Anthony J Baucum
- Department of Molecular Physiology and Biophysics, Vanderbilt University, Nashville, Tennessee 37232-0615, USA.
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Virshup DM, Shenolikar S. From Promiscuity to Precision: Protein Phosphatases Get a Makeover. Mol Cell 2009; 33:537-45. [DOI: 10.1016/j.molcel.2009.02.015] [Citation(s) in RCA: 431] [Impact Index Per Article: 28.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/21/2008] [Revised: 02/18/2009] [Accepted: 02/20/2009] [Indexed: 10/21/2022]
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Dancheck B, Nairn AC, Peti W. Detailed structural characterization of unbound protein phosphatase 1 inhibitors. Biochemistry 2008; 47:12346-56. [PMID: 18954090 PMCID: PMC2645960 DOI: 10.1021/bi801308y] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Protein phosphatase 1 (PP1) is an essential and ubiquitous serine/threonine protein phosphatase that is regulated by more than 100 known inhibitor and targeting proteins. It is currently unclear how protein inhibitors distinctly and specifically regulate PP1 to enable rapid responses to cellular alterations. We demonstrate that two PP1 inhibitors, I-2 and DARPP-32, belong to the class of intrinsically unstructured proteins (IUPs). We show that both inhibitors have distinct preferences for transient local and long-range structure. These preferences are likely their structural signature for their interaction with PP1. Furthermore, we show that upon phosphorylation of Thr(34) in DARPP-32, which turns DARPP-32 into a potent inhibitor of PP1, neither local nor long-range structure of DARPP-32 is altered. Therefore, our data suggest a role for these transient three-dimensional topologies in binding mechanisms that enable extensive contacts with PP1's invariant surfaces. Together, these interactions enable potent and selective inhibition of PP1.
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Affiliation(s)
- Barbara Dancheck
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI, 02912
| | - Angus C. Nairn
- Department of Psychiatry, Yale University School of Medicine, New Haven, CT 06508
| | - Wolfgang Peti
- Department of Molecular Pharmacology, Physiology and Biotechnology, Brown University, Providence, RI, 02912
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38
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Maternal phosphatase inhibitor-2 is required for proper chromosome segregation and mitotic synchrony during Drosophila embryogenesis. Genetics 2008; 179:1823-33. [PMID: 18689877 DOI: 10.1534/genetics.108.091959] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Protein phosphatase-1 (PP1) is a major Ser/Thr phosphatase conserved among all eukaryotes, present as the essential GLC7 gene in yeast. Inhibitor-2 (I-2) is an ancient PP1 regulator, named GLC8 in yeast, but its in vivo function is unknown. Unlike mammals with multiple I-2 genes, in Drosophila there is a single I-2 gene, and here we describe its maternally derived expression and required function during embryogenesis. During oogenesis, germline expression of I-2 results in the accumulation of RNA and abundant protein in unfertilized eggs; in embryos, the endogenous I-2 protein concentrates around condensed chromosomes during mitosis and also surrounds interphase nuclei. An I-2 loss-of-function genotype is associated with a maternal-effect phenotype that results in drastically reduced progeny viability, as measured by reduced embryonic hatch rates and larval lethality. Embryos derived from I-2 mutant mothers show faulty chromosome segregation and loss of mitotic synchrony in cleavage-stage embryos, patchy loss of nuclei in syncytial blastoderms, and cuticular pattern defects in late-stage embryos. Transgenic expression of wild-type I-2 in mutant mothers gives dose-dependent rescue of the maternal effect on embryo hatch rate. We propose that I-2 is required for proper chromosome segregation during Drosophila embryogenesis through the coordinated regulation of PP1 and Aurora B.
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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] [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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40
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Vessey JP, Karra D. More than just synaptic building blocks: scaffolding proteins of the post-synaptic density regulate dendritic patterning. J Neurochem 2007; 102:324-32. [PMID: 17596209 DOI: 10.1111/j.1471-4159.2007.04662.x] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
The dendritic arbor is responsible for receiving and consolidating neuronal input. Outgrowth and morphogenesis of the arbor are complex stages of development that are poorly understood. However, recent findings have identified synaptic scaffolding proteins as novel regulators of these important events. Scaffolding proteins are enriched in the post-synaptic density where they bind and bring into close proximity neurotransmitter receptors, signaling molecules, and regulators of the actin cytoskeleton. This property is important for dendritic spine morphogenesis and maintenance in the mature neuron. Scaffolding proteins are now being described as key regulators of neurite outgrowth, dendritic development, and pattern formation in immature neurons. These proteins, which include post-synaptic-95, Shank and Densin-180, as well as many of their interacting partners, appear to regulate both the microtubule and actin cytoskeleton to influence dendrite morphology. Through a large array of protein-protein interaction domains, scaffolding proteins are able to form large macromolecular complexes that include cytoskeletal motor proteins as well as microtubule and actin regulatory molecules. Together, the new findings form a persuasive argument that scaffolding proteins deliver critical regulatory elements to sites of dendritic outgrowth and branching to modulate the formation and maintenance of the dendritic arbor.
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Affiliation(s)
- John P Vessey
- Department of Neural Cell Biology, Center for Brain Research, Medical University of Vienna, Vienna, Austria.
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Barbato JC. Estrogen Receptor Activation—Good, Aldosterone Receptor Blockade—Beneficial, Communication Between Receptors…Priceless. Hypertension 2007; 50:297-8. [PMID: 17562976 DOI: 10.1161/hypertensionaha.107.092437] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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Arias-Loza PA, Hu K, Dienesch C, Mehlich AM, König S, Jazbutyte V, Neyses L, Hegele-Hartung C, Heinrich Fritzemeier K, Pelzer T. Both Estrogen Receptor Subtypes, α and β, Attenuate Cardiovascular Remodeling in Aldosterone Salt–Treated Rats. Hypertension 2007; 50:432-8. [PMID: 17562975 DOI: 10.1161/hypertensionaha.106.084798] [Citation(s) in RCA: 58] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Experimental and population-based studies indicate that female gender and estrogens protect the cardiovascular system against aldosterone-induced injury. Understanding the function of estrogens in heart disease requires more precise information on the role of both estrogen receptor (ER) subtypes, ERalpha and ERbeta. Therefore, we determined whether selective activation of ERalpha or of ERbeta would confer redundant, specific, or opposing effects on cardiovascular remodeling in aldosterone salt-treated rats. The ERalpha agonist 16alpha-LE2, the ERbeta agonist 8beta-VE2, and the nonselective estrogen receptor agonist 17beta-estradiol lowered elevated blood pressure, cardiac mass, and cardiac myocyte cross-sectional areas, as well as increased perivascular collagen accumulation and vascular osteopontin expression in ovariectomized rats receiving chronic aldosterone infusion plus a high-salt diet for 8 weeks. Uterus atrophy was prevented by 16alpha-LE2 and 17beta-estradiol but not by 8beta-VE2. Cardiac proteome analyses by 2D gel electrophoresis, mass spectrometry, and peptide sequencing identified specific subsets of proteins involved in cardiac contractility, energy metabolism, cellular stress response and extracellular matrix formation that were regulated in opposite directions by aldosterone salt treatment and by different estrogen receptor agonists. We conclude that activation of either ERalpha or ERbeta protects the cardiovascular system against the detrimental effects of aldosterone salt treatment and confers redundant, as well as specific, effects on cardiac protein expression. Nonfeminizing ERbeta agonists such as 8beta-VE2 have a therapeutic potential in the treatment of hypertensive heart disease.
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Hurley TD, Yang J, Zhang L, Goodwin KD, Zou Q, Cortese M, Dunker AK, DePaoli-Roach AA. Structural basis for regulation of protein phosphatase 1 by inhibitor-2. J Biol Chem 2007; 282:28874-28883. [PMID: 17636256 DOI: 10.1074/jbc.m703472200] [Citation(s) in RCA: 154] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The functional specificity of type 1 protein phosphatases (PP1) depends on the associated regulatory/targeting and inhibitory subunits. To gain insights into the mechanism of PP1 regulation by inhibitor-2, an ancient and intrinsically disordered regulator, we solved the crystal structure of the complex to 2.5A resolution. Our studies show that, when complexed with PP1c, I-2 acquires three regions of order: site 1, residues 12-17, binds adjacent to a region recognized by many PP1 regulators; site 2, amino acids 44-56, interacts along the RVXF binding groove through an unsuspected sequence, KSQKW; and site 3, residues 130-169, forms alpha-helical regions that lie across the substrate-binding cleft. Specifically, residues 148-151 interact at the catalytic center, displacing essential metal ions, accounting for both rapid inhibition and slower inactivation of PP1c. Thus, our structure provides novel insights into the mechanism of PP1 inhibition and subsequent reactivation, has broad implications for the physiological regulation of PP1, and highlights common inhibitory interactions among phosphoprotein phosphatase family members.
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Affiliation(s)
- Thomas D Hurley
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202.
| | - Jie Yang
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Lili Zhang
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Kristie D Goodwin
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Qin Zou
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Marc Cortese
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - A Keith Dunker
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202
| | - Anna A DePaoli-Roach
- Department of Biochemistry and Molecular Biology, Indiana University School of Medicine, Indianapolis, Indiana 46202.
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Bullock SA, Platholi J, Gjyrezi A, Heerdt PM, Tung HL, Hemmings HC. Differential regulation of protein phosphatase-1(I) by neurabin. Biochem Biophys Res Commun 2007; 358:140-4. [PMID: 17467665 PMCID: PMC1989152 DOI: 10.1016/j.bbrc.2007.04.076] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2007] [Accepted: 04/12/2007] [Indexed: 11/29/2022]
Abstract
Neurabin is a brain-specific actin and protein phosphatase-1 (PP-1) binding protein that inhibits the purified catalytic subunit of protein phosphatase-1 (PP-1(C)). However, endogenous PP-1 exists primarily as multimeric complexes of PP-1(C) bound to various regulatory proteins that determine its activity, substrate specificity, subcellular localization and function. The major form of endogenous PP-1 in brain is protein phosphatase-1(I) (PP-1(I)), a Mg(2+)/ATP-dependent form of PP-1 that consists of PP-1(C), the inhibitor-2 regulatory subunit, an activating protein kinase and other unidentified proteins. We have identified four PP-1(I) holoenzyme fractions (PP-1(IA), PP-1(IB), PP-1(IC), and PP-1(ID)) in freshly harvested pig brain separable by poly-L-lysine chromatography. Purified recombinant neurabin (amino acid residues 1-485) inhibited PP-1(IB) (IC(50)=1.1 microM), PP-1(IC) (IC(50)=0.1 microM), and PP-1(ID) (IC(50)=0.2 microM), but activated PP-1(IA) by up to threefold (EC(50)=40 nM). The PP-1(IA) activation domain was localized to neurabin(1-210). Our results indicate a novel mechanism of PP-1 regulation by neurabin as both an inhibitor and an activator of distinct forms of PP-1(I) in brain.
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Affiliation(s)
- S. Andrew Bullock
- Institute for Neuronal Cell Signaling, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021, USA
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Jimcy Platholi
- Institute for Neuronal Cell Signaling, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021, USA
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Ada Gjyrezi
- Institute for Neuronal Cell Signaling, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Paul M. Heerdt
- Institute for Neuronal Cell Signaling, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021, USA
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - H.Y. Lim Tung
- Institute for Neuronal Cell Signaling, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021, USA
| | - Hugh C. Hemmings
- Institute for Neuronal Cell Signaling, Department of Anesthesiology, Weill Medical College of Cornell University, New York, NY 10021, USA
- Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021, USA
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45
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Huang HB, Chen YC, Lee TT, Huang YC, Liu HT, Liu CK, Tsay HJ, Lin TH. Structural and biochemical characterization of inhibitor-1α. Proteins 2007; 68:779-88. [PMID: 17510962 DOI: 10.1002/prot.21438] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Inhibitor-1alpha is one of the isoforms of human protein phosphatase inhibitor-1. It is a product of alternative splicing of inhibitor-1 gene and lacks 51 internal amino acids from residue 84 to 134 of inhibitor-1. Here we have characterized the structural and biochemical properties of inhibitor-1alpha. Structural analysis of recombinant inhibitor-1alpha by NMR spectroscopy revealed that inhibitor-1alpha adopts a predominantly random coil conformation. Excluding the region from residue 84 to 134 of inhibitor-1, the structural features of inhibitor-1 and inhibitor-1alpha are almost the same as each other. The IC(50) value of inhibitor-1alpha in inhibition of Protein phosphatase-1 (PP1) is comparable to that of inhibitor-1, indicating that inhibitor-1alpha is a potent inhibitor of PP1 when Thr-35 is phosphorylated by PKA. For phosphorylation by PKA and dephosphorylation by protein phosphatase-1, -2A, and -2B, the measured kinetic parameters of inhibitor-1alpha are very close to those of inhibitor-1. Taken together, these results suggest that inhibitor-1alpha preserves the structure of inhibitor-1, the PP1 inhibitory activity and the functional specificities toward phosphorylation by PKA and dephosphorylation by protein phosphatase-1, -2A, and -2B.
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Affiliation(s)
- Hsien-Bin Huang
- Institute of Molecular Biology, National Chung Cheng University, Chia-Yi 621, Taiwan, Republic of China
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46
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Hung W, Hwang C, Po MD, Zhen M. Neuronal polarity is regulated by a direct interaction between a scaffolding protein, Neurabin, and a presynaptic SAD-1 kinase in Caenorhabditis elegans. Development 2006; 134:237-49. [PMID: 17151015 DOI: 10.1242/dev.02725] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The establishment of axon-dendrite identity in developing neurites is essential for the development of a functional nervous system. The SAD serine-threonine kinases have been implicated in regulating neuronal polarization and synapse formation. Here, we show that the C. elegans SAD-1 kinase regulates axonal identity and synapse formation through distinct mechanisms. We identified a scaffolding protein, Neurabin (NAB-1), as a physiological binding partner of SAD-1. Both sad-1 and nab-1 loss-of-function mutants display polarity defects in which synaptic vesicles accumulate in both axons and dendrites. We show that sad-1 and nab-1 function in the same genetic pathway to restrict axonal fate. Unlike sad-1, nab-1 mutants display normal morphology of vesicle clusters. Strikingly, although the physical interaction of NAB-1 with SAD-1 is necessary for polarity, it is dispensable for synapse morphology. We propose that Neurabin functions as a scaffold to facilitate SAD-1-mediated phosphorylation for substrates specific for restricting axonal fate during neuronal polarization.
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Affiliation(s)
- Wesley Hung
- Samuel Lunenfeld Research Institute, Mount Sinai Hospital and Department of Microbiology and Medical Genetics, University of Toronto, Ontario, M5G 1X5, Canada
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47
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Mansuy IM, Shenolikar S. Protein serine/threonine phosphatases in neuronal plasticity and disorders of learning and memory. Trends Neurosci 2006; 29:679-86. [PMID: 17084465 DOI: 10.1016/j.tins.2006.10.004] [Citation(s) in RCA: 106] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Revised: 07/28/2006] [Accepted: 10/19/2006] [Indexed: 01/12/2023]
Abstract
Phosphorylation and dephosphorylation of cellular proteins by protein kinases and phosphatases represent important mechanisms for controlling major biological events. In the nervous system, protein phosphatases are contained in highly dynamic complexes localized within specialized subcellular compartments and they ensure timely dephosphorylation of multiple neuronal phosphoproteins. This modulates the responsiveness of individual synapses to neural activity and controls synaptic plasticity. These enzymes in turn play a key role in many forms of learning and memory, and their dysfunction contributes to cognitive deficits associated with aging and dementias or neurodegenerative diseases. Here, we review key modes of regulation of neuronal protein serine/threonine phosphatases and their contribution to disorders of learning and memory.
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Affiliation(s)
- Isabelle M Mansuy
- Brain Research Institute, Medical Faculty of the University Zürich, Winterthurerstrasse 190, CH-8057 Zürich, Switzerland.
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Gallego M, Kang H, Virshup D. Protein phosphatase 1 regulates the stability of the circadian protein PER2. Biochem J 2006; 399:169-75. [PMID: 16813562 PMCID: PMC1570171 DOI: 10.1042/bj20060678] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The circadian clock is regulated by a transcription/translation negative feedback loop. A key negative regulator of circadian rhythm in mammals is the PER2 (mammalian PERIOD 2) protein. Its daily degradation at the end of the night accompanies de-repression of transcription. CKI (casein kinase I ) has been identified as the kinase that phosphorylates PER2, targeting it for ubiquitin-mediated proteasomal degradation. We now report that PER2 degradation is also negatively regulated by PP1 (protein phosphatase 1)-mediated dephosphorylation. In Xenopus egg extract, PP1 inhibition by Inhibitor-2 accelerated mPER2 degradation. Co-immunoprecipitation experiments showed that PER2 bound to PP1c in transfected HEK-293 cells. PP1 immunoprecipitated from HEK-293 cells, mouse liver and mouse brain, dephosphorylated CKI-phosphorylated PER2, showing that PER2 is a substrate for mammalian endogenous PP1. Moreover, over-expression of the dominant negative form of PP1c, the D95N mutant, accelerated ubiquitin and proteasome-mediated degradation of PER2, and shortened the PER2 half-life in HEK-293 cells. Over-expression of the PP1 inhibitors, protein phosphatase 1 holoenzyme inhibitor-1 and Inhibitor-2, confirmed these results. Thus PP1 regulates PER2 stability and is therefore a candidate to regulate mammalian circadian rhythms.
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Affiliation(s)
- Monica Gallego
- *Center for Children, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, U.S.A
| | - Heeseog Kang
- *Center for Children, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, U.S.A
| | - David M. Virshup
- *Center for Children, Huntsman Cancer Institute, University of Utah, Salt Lake City, UT 84112, U.S.A
- †Department of Pediatrics, University of Utah, Salt Lake City, UT 84112, U.S.A
- To whom correspondence should be addressed (email )
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Sarrouilhe D, di Tommaso A, Métayé T, Ladeveze V. Spinophilin: from partners to functions. Biochimie 2006; 88:1099-113. [PMID: 16737766 DOI: 10.1016/j.biochi.2006.04.010] [Citation(s) in RCA: 97] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/10/2005] [Accepted: 04/21/2006] [Indexed: 01/14/2023]
Abstract
Spinophilin/neurabin 2 has been isolated independently by two laboratories as a protein interacting with protein phosphatase 1 (PP1) and F-actin. Gene analysis and biochemical approaches have contributed to define a number of distinct modular domains in spinophilin that govern protein-protein interactions such as two F-actin-, three potential Src homology 3 (SH3)-, a receptor- and a PP1-binding domains, a PSD95/DLG/zo-1 (PDZ) and three coiled-coil domains, and a potential leucine/isoleucine zipper (LIZ) motif. More than 30 partner proteins of spinophilin have been discovered, including cytoskeletal and cell adhesion molecules, enzymes, guanine nucleotide exchange factors (GEF) and regulator of G-protein signalling protein, membrane receptors, ion channels and others proteins like the tumour suppressor ARF. The physiological relevance of some of these interactions remains to be demonstrated. However, spinophilin structure suggests that the protein is a multifunctional protein scaffold that regulates both membrane and cytoskeletal functions. Spinophilin plays important functions in the nervous system where it is implicated in spine morphology and density regulation, synaptic plasticity and neuronal migration. Spinophilin regulates also seven-transmembrane receptor signalling and may provide a link between some of these receptors and intracellular mitogenic signalling events dependent on p70(S6) kinase and Rac G protein-GEF. Strikingly a role for spinophilin in cell growth was demonstrated and this effect was enhanced by its interaction with ARF. Here we review the current knowledge of the protein partners of spinophilin and present the available data that are contributing to the appreciation of spinophilin functions.
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Affiliation(s)
- D Sarrouilhe
- Laboratoire de Physiologie Humaine, Faculté de Médecine et Pharmacie, 34, rue du Jardin-des-Plantes, BP 199, 86005 Poitiers cedex, France.
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50
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Tsukada M, Prokscha A, Eichele G. Neurabin II mediates doublecortin-dephosphorylation on actin filaments. Biochem Biophys Res Commun 2006; 343:839-47. [PMID: 16564023 DOI: 10.1016/j.bbrc.2006.03.045] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2006] [Accepted: 03/07/2006] [Indexed: 11/20/2022]
Abstract
Mutations in the human Doublecortin (DCX) gene cause X-linked lissencephaly, a neuronal migration disorder. DCX binds to microtubules and actin filaments. Association of Dcx with F-actin is regulated by site-specific phosphorylation and by neurabin II, an F-actin binding protein that also binds to Dcx. We show here that neurabin II mediates dephosphorylation of Dcx by protein phosphatase 1 (PP1). Furthermore, overexpression of PP1 reduces Dcx phosphorylation and decreases Dcx binding to F-actin. By contrast, abolishing PP1 binding to neurabin II maintains phosphorylation levels of Dcx, leading to a retention of Dcx at F-actin. We suggest that a dynamic regulation of Dcx mediated by neurabin II regulates the translocation of Dcx from F-actin to microtubules and vice versa.
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Affiliation(s)
- Miki Tsukada
- Max-Planck-Institute for Experimental Endocrinology, Feodor-Lynen-Strasse 7, D-30625 Hannover, Germany.
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