Protein phosphatase 1 – targeted in many directions

2002 ◽  
Vol 115 (2) ◽  
pp. 241-256 ◽  
Author(s):  
Patricia T. W. Cohen
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Binding Motif ◽  
Cellular Functions ◽  
Regulatory Subunits ◽  
Specific Location ◽  
Hydrophobic Groove ◽  
Intracellular Signals ◽  
Small Hydrophobic ◽  
Rvxf Motif

Protein phosphatase 1 (PP1) is a major eukaryotic protein serine/threonine phosphatase that regulates an enormous variety of cellular functions through the interaction of its catalytic subunit (PP1c) with over fifty different established or putative regulatory subunits. Most of these target PP1c to specific subcellular locations and interact with a small hydrophobic groove on the surface of PP1c through a short conserved binding motif – the RVxF motif – which is often preceded by further basic residues. Weaker interactions may subsequently enhance binding and modulate PP1 activity/specificity in a variety of ways. Several putative targeting subunits do not possess an RVxF motif but nevertheless interact with the same region of PP1c. In addition, several ‘modulator’ proteins bind to PP1c but do not possess a domain targeting them to a specific location. Most are potent inhibitors of PP1c and possess at least two sites for interaction with PP1c, one of which is identical or similar to the RVxF motif.Regulation of PP1c in response to extracellular and intracellular signals occurs mostly through changes in the levels, conformation or phosphorylation status of targeting subunits. Understanding of the mode of action of PP1c complexes may facilitate development of drugs that target particular PP1c complexes and thereby modulate the phosphorylation state of a very limited subset of proteins.

scholarly journals Importance of a Surface Hydrophobic Pocket on Protein Phosphatase-1 Catalytic Subunit in Recognizing Cellular Regulators

2005 ◽  
Vol 280 (16) ◽  
pp. 15903-15911 ◽  
Author(s):  
Jennifer A. Gibbons ◽  
Douglas C. Weiser ◽  
Shirish Shenolikar
Keyword(s):  
Protein Phosphatase ◽  
Binding Pocket ◽  
Catalytic Subunit ◽  
Protein Phosphatase 1 ◽  
Regulatory Subunit ◽  
Cellular Functions ◽  
Hydrophobic Pocket ◽  
Regulatory Subunits ◽  
Physiological Regulation ◽  
Endogenous Protein

Cellular functions of protein phosphatase-1 (PP1), a major eukaryotic serine/threonine phosphatase, are defined by the association of PP1 catalytic subunits with endogenous protein inhibitors and regulatory subunits. Many PP1 regulators share a consensus RVXF motif, which docks within a hydrophobic pocket on the surface of the PP1 catalytic subunit. Although these regulatory proteins also possess additional PP1-binding sites, mutations of the RVXF sequence established a key role of this PP1-binding sequence in the function of PP1 regulators. WT PP1α, the C-terminal truncated PP1α-(1–306), a chimeric PP1α containing C-terminal sequences from PP2A, another phosphatase, PP1α-(1–306) with the RVXF-binding pocket substitutions L289R, M290K, and C291R, and PP2A were analyzed for their regulation by several mammalian proteins. These studies established that modifications of the RVXF-binding pocket had modest effects on the catalytic activity of PP1, as judged by recognition of substrates and sensitivity to toxins. However, the selected modifications impaired the sensitivity of PP1 to the inhibitor proteins, inhibitor-1 and inhibitor-2. In addition, they impaired the ability of PP1 to bind neurabin-I, the neuronal regulatory subunit, and GM, the skeletal muscle glycogen-targeting subunit. These data suggested that differences in RVXF interactions with the hydrophobic pocket dictate the affinity of PP1 for cellular regulators. Substitution of a distinct RVXF sequence in inhibitor-1 that enhanced its binding and potency as a PP1 inhibitor emphasized the importance of the RVXF sequence in defining the function of this and other PP1 regulators. Our studies suggest that the diversity of RVXF sequences provides for dynamic physiological regulation of PP1 functions in eukaryotic cells.

scholarly journals Interaction with Protein Phosphatase 1 Is Essential for bifocal Function during the Morphogenesis of theDrosophila Compound Eye

2001 ◽  
Vol 21 (6) ◽  
pp. 2154-2164 ◽  
Author(s):  
Nicholas R. Helps ◽  
Patricia T. W. Cohen ◽  
Sami M. Bahri ◽  
William Chia ◽  
Kavita Babu
Keyword(s):  
Actin Cytoskeleton ◽  
Protein Phosphatase ◽  
Compound Eye ◽  
Subcellular Location ◽  
Photoreceptor Cells ◽  
Protein Phosphatase 1 ◽  
Binding Motif ◽  
Membrane Structures ◽  
Regulatory Subunits ◽  
Major Function

ABSTRACT The gene bifocal (bif), required for photoreceptor morphogenesis in the Drosophila compound eye, encodes a protein that is shown to interact with protein phosphatase 1 (PP1) using the yeast two-hybrid system. Complex formation between Bif and PP1 is supported by coprecipitation of the two proteins. Residues 992 to 995 (RVQF) in the carboxy-terminal region of Bif, which conform to the consensus PP1-binding motif, are shown to be essential for the interaction of Bif with PP1. The interaction of PP1 with bacterially expressed and endogenous Bif can be disrupted by a synthetic peptide known to block interaction of other regulatory subunits with PP1. Nullbif mutants exhibit a rough eye phenotype, disorganized rhabdomeres (light-gathering rhodopsin-rich microvillar membrane structures in the photoreceptor cells) and alterations in the actin cytoskeleton. Expression of wild-type bif transgenes resulted in significant rescue of these abnormalities. In contrast, expression of transgenes encoding the Bif F995A mutant, which disrupts binding to PP1, was unable to rescue any aspect of the bifphenotype. The results indicate that the PP1-Bif interaction is critical for the rescue and that a major function of Bif is to target PP1c to a specific subcellular location. The role of the PP1-Bif complex in modulating the organization of the actin cytoskeleton underlying the rhabdomeres is discussed.

scholarly journals SARP, a new alternatively spliced protein phosphatase 1 and DNA interacting protein

2007 ◽  
Vol 402 (1) ◽  
pp. 187-196 ◽  
Author(s):  
Gareth J. Browne ◽  
Margarida Fardilha ◽  
Senga K. Oxenham ◽  
Wenjuan Wu ◽  
Nicholas R. Helps ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Mammalian Cells ◽  
Leucine Zipper ◽  
Transforming Growth Factor ◽  
Binding Protein ◽  
Transforming Growth Factor Β ◽  
Ankyrin Repeat ◽  
Protein Phosphatase 1 ◽  
Binding Motif ◽  
Alternative Mrna Splicing

PP1 (protein phosphatase 1) is a ubiquitously expressed serine/threonine-specific protein phosphatase whose activity towards different substrates appears to be mediated via binding to specific proteins that play critical regulatory and targeting roles. In the present paper we report the cloning and characterization of a new protein, termed SARP (several ankyrin repeat protein), which is shown to interact with all isoforms of PP1 by a variety of techniques. A region encompassing a consensus PP1-binding motif in SARP (K354VHF357) modulates endogenous SARP–PP1 activity in mammalian cells. This SARP–PP1 interaction motif lies partially within the first ankyrin repeat in contrast with other proteins [53BP2 (p53 binding protein 2), MYPT1/M110/MBS (myosin binding protein of PP1) and TIMAP (transforming growth factor β inhibited, membrane-associated protein)], where a PP1-binding motif precedes the ankyrin repeats. Alternative mRNA splicing produces several isoforms of SARP from a single human gene at locus 11q14. SARP1 and/or SARP2 (92–95 kDa) are ubiquitously expressed in all tissues with high levels in testis and sperm, where they are shown to interact with both PP1γ1 and PP1γ2. SARP3 (65 kDa) is most abundant in brain where SARP isoforms interact with both PP1α and PP1γ1. SARP is highly abundant in the nucleus of mammalian cells, consistent with the putative nuclear localization signal at the N-terminus. The presence of a leucine zipper near the C-terminus of SARP1 and SARP2, and the binding of mammalian DNA to SARP2, suggests that SARP1 and SARP2 may be transcription factors or DNA-associated proteins that modulate gene expression.

Protein Phosphatase-1 Complex Disassembly by p97 is Initiated through Multivalent Recognition of Catalytic and Regulatory Subunits by the p97 SEP-domain Adapters

2020 ◽  
Vol 432 (23) ◽  
pp. 6061-6074
Author(s):  
Matthias Kracht ◽  
Johannes van den Boom ◽  
Jonas Seiler ◽  
Alexander Kröning ◽  
Farnusch Kaschani ◽  
...  
Keyword(s):  
Protein Phosphatase ◽  
Protein Phosphatase 1 ◽  
Regulatory Subunits

scholarly journals An eIF2α-binding motif in protein phosphatase 1 subunit GADD34 and its viral orthologs is required to promote dephosphorylation of eIF2α

2015 ◽  
Vol 112 (27) ◽  
pp. E3466-E3475 ◽  
Author(s):  
Margarito Rojas ◽  
Gabriel Vasconcelos ◽  
Thomas E. Dever
Keyword(s):  
Protein Phosphatase ◽  
African Swine Fever Virus ◽  
Consensus Sequence ◽  
Point Mutations ◽  
Translation Initiation Factor ◽  
Protein Phosphatase 1 ◽  
Initiation Factor ◽  
Protective Mechanism ◽  
Binding Motif ◽  
Α Subunit

Transient protein synthesis inhibition, mediated by phosphorylation of the α subunit of eukaryotic translation initiation factor 2 (eIF2α), is an important protective mechanism cells use during stress conditions. Following relief of the stress, the growth arrest and DNA damage-inducible protein GADD34 associates with the broadly acting serine/threonine protein phosphatase 1 (PP1) to dephosphorylate eIF2α. Whereas the PP1-binding motif on GADD34 has been defined, it remains to be determined how GADD34 directs PP1 to specifically dephosphorylate eIF2α. In this report, we map a novel eIF2α-binding motif to the C terminus of GADD34 in a region distinct from where PP1 binds to GADD34. This motif is characterized by the consensus sequence Rx[Gnl]x1–2Wxxx[Arlv]x[Dn][Rg]xRFxx[Rlvk][Ivc], where capital letters are preferred and x is any residue. Point mutations altering the eIF2α-binding motif impair the ability of GADD34 to interact with eIF2α, promote eIF2α dephosphorylation, and suppress PKR toxicity in yeast. Interestingly, this eIF2α-docking motif is conserved among viral orthologs of GADD34, and is necessary for the proteins produced by African swine fever virus, Canarypox virus, and Herpes simplex virus to promote eIF2α dephosphorylation. Taken together, these data indicate that GADD34 and its viral orthologs direct specific dephosphorylation of eIF2α by interacting with both PP1 and eIF2α through independent binding motifs.

Regulation of Platelet Survival by Protein Phosphatase 1 Gamma

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2026-2026
Author(s):  
Masahiro Yanagisawa ◽  
Han Hyojeong ◽  
Francisca C. Gushiken ◽  
K. Vinod Vijayan
Keyword(s):  
Cell Survival ◽  
Protein Phosphatase ◽  
Conflicts Of Interest ◽  
Serine Phosphorylation ◽  
Protein Phosphatase 1 ◽  
Binding Motif ◽  
Caspase 9 ◽  
Platelet Apoptosis ◽  
Platelet Survival ◽  
Apoptotic Protein

Abstract Abstract 2026 Platelets are key players in hemostasis and their senescence is intrinsically associated with the activation of apoptotic pathways that shows similarities to the apoptosis of nucleated cells. Anti-apoptotic protein Bcl-xl restrains the pro-apoptotic Bak activity and maintains platelet survival in circulation. In nucleated cells, serine phosphorylation of a pro-apoptotic protein Bad can also promote cell survival. Serine phosphorylation of Bad is regulated by the action of serine/threonine (Ser/Thr) protein kinases and Ser/Thr protein phosphatases. Although alterations in the activities of either enzyme can change the rate of apoptosis, whether Ser/Thr phosphatases participate in regulating platelet apoptosis is unknown. In this study, we report that the mice lacking the catalytic subunit of protein phosphatase 1 gamma (PP1cγ) exhibit a moderate but significant increase in the number of circulating platelets [596 × 103/μL ± 17.9 in WT compared with 694 × 103/μL ± 19.8 in PP1cγ–/– mice; P = .0003]. Examination of the bone marrow from the PP1cγ–/– mice revealed a non-significant increase in the number of morphologically matured megakaryocytes. A trend towards decreased plasma thrombopoietin levels were also noticed in PP1cγ–/– mice. These observations suggest that an increased megakaryopoiesis/thrombopoiesis may not fully account for the increased platelet numbers in PP1cγ–/– mice. In vivo platelet survival studies revealed that the loss of PP1cγ modestly increased platelet half life in circulation (t1/2 ∼69 hours in WT compared to ∼78 hours in PP1cγ–/– mice). PP1cγ–/– platelets had decreased mean platelet volume, suggesting the PP1cγ–/– mice may harbor a greater proportion of older circulating platelets. These studies are consistent with the delayed clearance of platelets from PP1cγ–/– mice. Pro-apoptotic Bad possess PP1c binding motif and mechanistically, PP1cγ interacts with Bad protein in platelets. Phosphorylation of Bad Ser112, which promotes cell survival, was enhanced ∼50% in PP1cγ–/– platelets. Consistent with the increased BAD phosphorylation, co-immunoprecipitation studies revealed increased BAD-14-3-3 protein complexes from the PP1cγ–/– platelets. It is reported that in the phosphorylated state, BAD can interact with 14-3-3 and is sequestered in the cytoplasm, thereby preventing the binding of Bad with the mitochondrial anti-apoptotic Bcl-xl. Interaction of Bad with Bcl-xl has the potential to displace the pro-apoptotic Bak from the Bcl-xl-Bak protein complex to trigger apoptosis. Finally, immunoblotting with anti-caspase 9 antibody revealed decreased caspase 9 cleavage product (∼37 kDa) in the PP1cγ–/– platelets, suggesting decreased activation of caspase 9 dependent apoptotic pathway. These data indicate that the increased platelet counts in PP1cγ–/– mice could be in part due to delayed platelet apoptosis. Loss of PP1cγ leads to the hyperphosphorylation of BAD, which via an interaction with 14-3-3, delays caspase mediated apoptosis to prolong the life span of platelets. Disclosures: No relevant conflicts of interest to declare.

Transcriptional control by chromosome-associated protein phosphatase-1

2005 ◽  
Vol 33 (6) ◽  
pp. 1444-1446 ◽  
Author(s):  
D. Bennett
Keyword(s):  
Gene Expression ◽  
Protein Phosphatase ◽  
Transcriptional Control ◽  
Regulation Of Gene Expression ◽  
Polytene Chromosomes ◽  
Protein Phosphatase 1 ◽  
Environmental Cues ◽  
Spatial And Temporal Patterns ◽  
Regulatory Subunits ◽  
Chromosomal Loci

Tight regulation of gene expression is critical for cells to respond normally to physiological and environmental cues and to allow cell specialization. Reversible phosphorylation of key structural and regulatory proteins, from histones to the transcriptional machinery, is acknowledged to be an important mechanism of regulating spatial and temporal patterns of gene expression. PP1 (protein phosphatase-1), a major class of serine/threonine protein phosphatase, is found at many sites on Drosophila polytene chromosomes where it is involved in controlling gene expression and chromatin structure. PP1 is targeted to different chromosomal loci through interaction with a variety of different regulatory subunits, which modify PP1's activity towards specific substrates. This mini-review gives an overview of known chromosome-associated PP1 complexes, their role in transcriptional control and the prospects for future analysis.

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