1
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Hodapp SJ, Gravel N, Kannan N, Newton AC. Cancer-associated mutations in protein kinase C theta are loss-of-function. Biochem J 2024; 481:759-775. [PMID: 38752473 DOI: 10.1042/bcj20240148] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2024] [Revised: 05/14/2024] [Accepted: 05/16/2024] [Indexed: 06/11/2024]
Abstract
The Ca2+-independent, but diacylglycerol-regulated, novel protein kinase C (PKC) theta (θ) is highly expressed in hematopoietic cells where it participates in immune signaling and platelet function. Mounting evidence suggests that PKCθ may be involved in cancer, particularly blood cancers, breast cancer, and gastrointestinal stromal tumors, yet how to target this kinase (as an oncogene or as a tumor suppressor) has not been established. Here, we examine the effect of four cancer-associated mutations, R145H/C in the autoinhibitory pseudosubstrate, E161K in the regulatory C1A domain, and R635W in the regulatory C-terminal tail, on the cellular activity and stability of PKCθ. Live-cell imaging studies using the genetically-encoded fluorescence resonance energy transfer-based reporter for PKC activity, C kinase activity reporter 2 (CKAR2), revealed that the pseudosubstrate and C1A domain mutations impaired autoinhibition to increase basal signaling. This impaired autoinhibition resulted in decreased stability of the protein, consistent with the well-characterized behavior of Ca2+-regulated PKC isozymes wherein mutations that impair autoinhibition are paradoxically loss-of-function because the mutant protein is degraded. In marked contrast, the C-terminal tail mutation resulted in enhanced autoinhibition and enhanced stability. Thus, the examined mutations were loss-of-function by different mechanisms: mutations that impaired autoinhibition promoted the degradation of PKC, and those that enhanced autoinhibition stabilized an inactive PKC. Supporting a general loss-of-function of PKCθ in cancer, bioinformatics analysis revealed that protein levels of PKCθ are reduced in diverse cancers, including lung, renal, head and neck, and pancreatic. Our results reveal that PKCθ function is lost in cancer.
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Affiliation(s)
- Stefanie J Hodapp
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, U.S.A
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, U.S.A
| | - Nathan Gravel
- Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA 30602, U.S.A
| | - Natarajan Kannan
- Department of Biochemistry and Molecular Biology and Institute of Bioinformatics, University of Georgia, Athens, GA 30602, U.S.A
| | - Alexandra C Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, U.S.A
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2
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Chen XR, Dixit K, Yang Y, McDermott MI, Imam HT, Bankaitis VA, Igumenova TI. A novel bivalent interaction mode underlies a non-catalytic mechanism for Pin1-mediated protein kinase C regulation. eLife 2024; 13:e92884. [PMID: 38687676 PMCID: PMC11060717 DOI: 10.7554/elife.92884] [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: 09/19/2023] [Accepted: 04/08/2024] [Indexed: 05/02/2024] Open
Abstract
Regulated hydrolysis of the phosphoinositide phosphatidylinositol(4,5)-bis-phosphate to diacylglycerol and inositol-1,4,5-P3 defines a major eukaryotic pathway for translation of extracellular cues to intracellular signaling circuits. Members of the lipid-activated protein kinase C isoenzyme family (PKCs) play central roles in this signaling circuit. One of the regulatory mechanisms employed to downregulate stimulated PKC activity is via a proteasome-dependent degradation pathway that is potentiated by peptidyl-prolyl isomerase Pin1. Here, we show that contrary to prevailing models, Pin1 does not regulate conventional PKC isoforms α and βII via a canonical cis-trans isomerization of the peptidyl-prolyl bond. Rather, Pin1 acts as a PKC binding partner that controls PKC activity via sequestration of the C-terminal tail of the kinase. The high-resolution structure of full-length Pin1 complexed to the C-terminal tail of PKCβII reveals that a novel bivalent interaction mode underlies the non-catalytic mode of Pin1 action. Specifically, Pin1 adopts a conformation in which it uses the WW and PPIase domains to engage two conserved phosphorylated PKC motifs, the turn motif and hydrophobic motif, respectively. Hydrophobic motif is a non-canonical Pin1-interacting element. The structural information combined with the results of extensive binding studies and experiments in cultured cells suggest that non-catalytic mechanisms represent unappreciated modes of Pin1-mediated regulation of AGC kinases and other key enzymes/substrates.
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Affiliation(s)
- Xiao-Ru Chen
- Department of Biochemistry & Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Karuna Dixit
- Department of Biochemistry & Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Yuan Yang
- Department of Biochemistry & Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Mark I McDermott
- Department of Cell Biology & Genetics, Texas A&M UniversityCollege StationUnited States
| | - Hasan Tanvir Imam
- Department of Biochemistry & Biophysics, Texas A&M UniversityCollege StationUnited States
| | - Vytas A Bankaitis
- Department of Cell Biology & Genetics, Texas A&M UniversityCollege StationUnited States
| | - Tatyana I Igumenova
- Department of Biochemistry & Biophysics, Texas A&M UniversityCollege StationUnited States
- Department of Cell Biology & Genetics, Texas A&M UniversityCollege StationUnited States
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3
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Yu J, Boehr DD. Regulatory mechanisms triggered by enzyme interactions with lipid membrane surfaces. Front Mol Biosci 2023; 10:1306483. [PMID: 38099197 PMCID: PMC10720463 DOI: 10.3389/fmolb.2023.1306483] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2023] [Accepted: 11/17/2023] [Indexed: 12/17/2023] Open
Abstract
Recruitment of enzymes to intracellular membranes often modulates their catalytic activity, which can be important in cell signaling and membrane trafficking. Thus, re-localization is not only important for these enzymes to gain access to their substrates, but membrane interactions often allosterically regulate enzyme function by inducing conformational changes across different time and amplitude scales. Recent structural, biophysical and computational studies have revealed how key enzymes interact with lipid membrane surfaces, and how this membrane binding regulates protein structure and function. This review summarizes the recent progress in understanding regulatory mechanisms involved in enzyme-membrane interactions.
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Affiliation(s)
| | - David D. Boehr
- Department of Chemistry, The Pennsylvania State University, University Park, PA, United States
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4
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Chen XR, Dixit K, Yang Y, McDermott MI, Imam HT, Bankaitis VA, Igumenova TI. A novel bivalent interaction mode underlies a non-catalytic mechanism for Pin1-mediated Protein Kinase C regulation. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.18.558341. [PMID: 37781616 PMCID: PMC10541119 DOI: 10.1101/2023.09.18.558341] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/03/2023]
Abstract
Regulated hydrolysis of the phosphoinositide phosphatidylinositol(4,5)-bis-phosphate to diacylglycerol and inositol-1,4,5-P3 defines a major eukaryotic pathway for translation of extracellular cues to intracellular signaling circuits. Members of the lipid-activated protein kinase C isoenzyme family (PKCs) play central roles in this signaling circuit. One of the regulatory mechanisms employed to downregulate stimulated PKC activity is via a proteasome-dependent degradation pathway that is potentiated by peptidyl-prolyl isomerase Pin1. Here, we show that contrary to prevailing models, Pin1 does not regulate conventional PKC isoforms α and βII via a canonical cis-trans isomerization of the peptidyl-prolyl bond. Rather, Pin1 acts as a PKC binding partner that controls PKC activity via sequestration of the C-terminal tail of the kinase. The high-resolution structure of Pin1 complexed to the C-terminal tail of PKCβII reveals that a novel bivalent interaction mode underlies the non-catalytic mode of Pin1 action. Specifically, Pin1 adopts a compact conformation in which it engages two conserved phosphorylated PKC motifs, the turn motif and hydrophobic motif, the latter being a non-canonical Pin1-interacting element. The structural information, combined with the results of extensive binding studies and in vivo experiments suggest that non-catalytic mechanisms represent unappreciated modes of Pin1-mediated regulation of AGC kinases and other key enzymes/substrates.
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5
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Boland AW, Gas-Pascual E, van der Wel H, Kim HW, West CM. Synergy between a cytoplasmic vWFA/VIT protein and a WD40-repeat F-box protein controls development in Dictyostelium. Front Cell Dev Biol 2023; 11:1259844. [PMID: 37779900 PMCID: PMC10539598 DOI: 10.3389/fcell.2023.1259844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2023] [Accepted: 08/24/2023] [Indexed: 10/03/2023] Open
Abstract
Like most eukaryotes, the pre-metazoan social amoeba Dictyostelium depends on the SCF (Skp1/cullin-1/F-box protein) family of E3 ubiquitin ligases to regulate its proteome. In Dictyostelium, starvation induces a transition from unicellular feeding to a multicellular slug that responds to external signals to culminate into a fruiting body containing terminally differentiated stalk and spore cells. These transitions are subject to regulation by F-box proteins and O2-dependent posttranslational modifications of Skp1. Here we examine in greater depth the essential role of FbxwD and Vwa1, an intracellular vault protein inter-alpha-trypsin (VIT) and von Willebrand factor-A (vWFA) domain containing protein that was found in the FbxwD interactome by co-immunoprecipitation. Reciprocal co-IPs using gene-tagged strains confirmed the interaction and similar changes in protein levels during multicellular development suggested co-functioning. FbxwD overexpression and proteasome inhibitors did not affect Vwa1 levels suggesting a non-substrate relationship. Forced FbxwD overexpression in slug tip cells where it is normally enriched interfered with terminal cell differentiation by a mechanism that depended on its F-box and RING domains, and on Vwa1 expression itself. Whereas vwa1-disruption alone did not affect development, overexpression of either of its three conserved domains arrested development but the effect depended on Vwa1 expression. Based on structure predictions, we propose that the Vwa1 domains exert their negative effect by artificially activating Vwa1 from an autoinhibited state, which in turn imbalances its synergistic function with FbxwD. Autoinhibition or homodimerization might be relevant to the poorly understood tumor suppressor role of the evolutionarily related VWA5A/BCSC-1 in humans.
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Affiliation(s)
- Andrew W. Boland
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, United States
| | - Elisabet Gas-Pascual
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, United States
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, United States
| | - Hanke van der Wel
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Hyun W. Kim
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
| | - Christopher M. West
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA, United States
- Complex Carbohydrate Research Center, University of Georgia, Athens, GA, United States
- Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, United States
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6
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Jones AC, Kornev AP, Weng JH, Manning G, Taylor SS, Newton AC. Single-residue mutation in protein kinase C toggles between cancer and neurodegeneration. Biochem J 2023; 480:1299-1316. [PMID: 37551632 PMCID: PMC10586763 DOI: 10.1042/bcj20220397] [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: 03/16/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 08/09/2023]
Abstract
Conventional protein kinase C (cPKC) isozymes tune the signaling output of cells, with loss-of-function somatic mutations associated with cancer and gain-of-function germline mutations identified in neurodegeneration. PKC with impaired autoinhibition is removed from the cell by quality-control mechanisms to prevent the accumulation of aberrantly active enzyme. Here, we examine how a highly conserved residue in the C1A domain of cPKC isozymes permits quality-control degradation when mutated to histidine in cancer (PKCβ-R42H) and blocks down-regulation when mutated to proline in the neurodegenerative disease spinocerebellar ataxia (PKCγ-R41P). Using FRET-based biosensors, we determined that mutation of R42 to any residue, including lysine, resulted in reduced autoinhibition as indicated by higher basal activity and faster agonist-induced plasma membrane translocation. R42 is predicted to form a stabilizing salt bridge with E655 in the C-tail and mutation of E655, but not neighboring E657, also reduced autoinhibition. Western blot analysis revealed that whereas R42H had reduced stability, the R42P mutant was stable and insensitive to activator-induced ubiquitination and down-regulation, an effect previously observed by deletion of the entire C1A domain. Molecular dynamics (MD) simulations and analysis of stable regions of the domain using local spatial pattern (LSP) alignment suggested that P42 interacts with Q66 to impair mobility and conformation of one of the ligand-binding loops. Additional mutation of Q66 to the smaller asparagine (R42P/Q66N), to remove conformational constraints, restored degradation sensitivity. Our results unveil how disease-associated mutations of the same residue in the C1A domain can toggle between gain- or loss-of-function of PKC.
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Affiliation(s)
- Alexander C. Jones
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
- Biomedical Sciences Graduate Program, University of California, La Jolla, CA 92093, U.S.A
| | - Alexandr P. Kornev
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
| | - Jui-Hung Weng
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
| | | | - Susan S. Taylor
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
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7
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Abid F, Khan K, Badshah Y, Ashraf NM, Shabbir M, Hamid A, Afsar T, Almajwal A, Razak S. Non-synonymous SNPs variants of PRKCG and its association with oncogenes predispose to hepatocellular carcinoma. Cancer Cell Int 2023; 23:123. [PMID: 37344815 PMCID: PMC10286404 DOI: 10.1186/s12935-023-02965-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2023] [Accepted: 06/07/2023] [Indexed: 06/23/2023] Open
Abstract
BACKGROUND PRKCG encodes PKC γ, which is categorized under the classical protein kinase C family. No studies have specifically established the relationship between PRKCG nsSNPs with structural and functional variations in PKC γ in the context of hepatocellular carcinoma (HCC). The present study aims to uncover this link through in-silico and experimental studies. METHODS The 3D structure of PKC γ was predicted. Molecular Dynamic (MD) Simulations were run and estimates were made for interactions, stability, conservation and post-translational alterations between wild and mutant structures. The association of PRKCG levels with HCC survival rate was determined. Genotyping analyses were conducted to investigate the deleterious PRKCG nsSNP association with HCC. mRNA expression of PKC γ, HIF-1 alpha, AKT, SOCS3 and VEGF in the blood of controls and HCC patients was analyzed and a genetic cascade was constructed depicting these interactions. RESULTS The expression level of studied oncogenes was compared to tumour suppressor genes. Through Alphafold, the 3D structure of PKC γ was explored. Fifteen SNPs were narrowed down for in-silico analyses that were identified in exons 5, 10 and 18 and the regulatory and kinase domain of PKC γ. Root mean square deviation and fluctuation along with the radius of gyration unveiled potential changes between the wild and mutated variant structures. Mutant genotype AA (homozygous) corresponding to nsSNP, rs386134171 had more frequency in patients with OR (2.446), RR (1.564) and P-values (< 0.0029) that highlights its significant association with HCC compared to controls in which the wild genotype GG was found more prevalent. CONCLUSION nsSNP rs386134171 can be a genetic marker for HCC diagnosis and therapeutic studies. This study has laid down a road map for future studies to be conducted on HCC.
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Affiliation(s)
- Fizzah Abid
- Department of Healthcare Biotechnology, Atta-Ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, 44010, Pakistan
| | - Khushbukhat Khan
- Department of Healthcare Biotechnology, Atta-Ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, 44010, Pakistan
| | - Yasmin Badshah
- Department of Healthcare Biotechnology, Atta-Ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, 44010, Pakistan
| | - Naeem Mahmood Ashraf
- School of Biochemistry and Biotechnology, University of the Punjab, Lahore, 54590, Pakistan
| | - Maria Shabbir
- Department of Healthcare Biotechnology, Atta-Ur-Rahman School of Applied Biosciences, National University of Sciences and Technology, Islamabad, 44010, Pakistan.
| | - Arslan Hamid
- LIMES Institute (AG-Netea), University of Bonn, Carl-Troll-Str. 31, 53115, Bonn, Germany
| | - Tayyaba Afsar
- Department of Community Health Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Ali Almajwal
- Department of Community Health Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia
| | - Suhail Razak
- Department of Community Health Sciences, College of Applied Medical Sciences, King Saud University, Riyadh, Saudi Arabia.
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8
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Jones AC, Kornev AP, Weng JH, Manning G, Taylor SS, Newton AC. Single-residue mutation in protein kinase C toggles between cancer and neurodegeneration. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.03.16.532226. [PMID: 36993163 PMCID: PMC10055082 DOI: 10.1101/2023.03.16.532226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Conventional protein kinase C (PKC) isozymes tune the signaling output of cells, with loss-of-function somatic mutations associated with cancer and gain-of-function germline mutations identified in neurodegeneration. PKC with impaired autoinhibition is removed from the cell by quality-control mechanisms to prevent accumulation of aberrantly active enzyme. Here, we examine how a single residue in the C1A domain of PKCβ, arginine 42 (R42), permits quality-control degradation when mutated to histidine in cancer (R42H) and blocks downregulation when mutated to proline in the neurodegenerative disease spinocerebellar ataxia (R42P). Using FRET-based biosensors, we determined that mutation of R42 to any residue, including lysine, resulted in reduced autoinhibition as indicated by higher basal activity and faster agonist-induced plasma membrane translocation. R42 is predicted to form a stabilizing salt bridge with E655 in the C-tail and mutation of E655, but not neighboring E657, also reduced autoinhibition. Western blot analysis revealed that whereas R42H had reduced stability, the R42P mutant was stable and insensitive to activator-induced ubiquitination and downregulation, an effect previously observed by deletion of the entire C1A domain. Molecular dynamics (MD) simulations and analysis of stable regions of the domain using local spatial pattern (LSP) alignment suggested that P42 interacts with Q66 to impair mobility and conformation of one of the ligand-binding loops. Additional mutation of Q66 to the smaller asparagine (R42P/Q66N), to remove conformational constraints, restored degradation sensitivity to that of WT. Our results unveil how disease-associated mutations of the same residue in the C1A domain can toggle between gain- or loss-of-function of PKC.
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9
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Pilo CA, Newton AC. Two Sides of the Same Coin: Protein Kinase C γ in Cancer and Neurodegeneration. Front Cell Dev Biol 2022; 10:929510. [PMID: 35800893 PMCID: PMC9253466 DOI: 10.3389/fcell.2022.929510] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 05/23/2022] [Indexed: 12/23/2022] Open
Abstract
Protein kinase C (PKC) isozymes transduce myriad signals within the cell in response to the generation of second messengers from membrane phospholipids. The conventional isozyme PKCγ reversibly binds Ca2+ and diacylglycerol, which leads to an open, active conformation. PKCγ expression is typically restricted to neurons, but evidence for its expression in certain cancers has emerged. PKC isozymes have been labeled as oncogenes since the discovery that they bind tumor-promoting phorbol esters, however, studies of cancer-associated PKC mutations and clinical trial data showing that PKC inhibitors have worsened patient survival have reframed PKC as a tumor suppressor. Aberrant expression of PKCγ in certain cancers suggests a role outside the brain, although whether PKCγ also acts as a tumor suppressor remains to be established. On the other hand, PKCγ variants associated with spinocerebellar ataxia type 14 (SCA14), a neurodegenerative disorder characterized by Purkinje cell degeneration, enhance basal activity while preventing phorbol ester-mediated degradation. Although the basis for SCA14 Purkinje cell degeneration remains unknown, studies have revealed how altered PKCγ activity rewires cerebellar signaling to drive SCA14. Importantly, enhanced basal activity of SCA14-associated mutants inversely correlates with age of onset, supporting that enhanced PKCγ activity drives SCA14. Thus, PKCγ activity should likely be inhibited in SCA14, whereas restoring PKC activity should be the goal in cancer therapies. This review describes how PKCγ activity can be lost or gained in disease and the overarching need for a PKC structure as a powerful tool to predict the effect of PKCγ mutations in disease.
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Affiliation(s)
- Caila A. Pilo
- Department of Pharmacology, University of California, San Diego, San Diego, CA, United States
- Biomedical Sciences Graduate Program, University of California, San Diego, San Diego, CA, United States
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, San Diego, San Diego, CA, United States
- *Correspondence: Alexandra C. Newton,
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10
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Novarina D, Guerra P, Milias-Argeitis A. Vacuolar Localization via the N-terminal Domain of Sch9 is Required for TORC1-dependent Phosphorylation and Downstream Signal Transduction. J Mol Biol 2021; 433:167326. [PMID: 34695378 DOI: 10.1016/j.jmb.2021.167326] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2021] [Revised: 10/12/2021] [Accepted: 10/18/2021] [Indexed: 10/20/2022]
Abstract
The budding yeast Sch9 kinase (functional orthologue of the mammalian S6 kinase) is a major effector of the Target of Rapamycin Complex 1 (TORC1) complex in the regulation of cell growth in response to nutrient availability and stress. Sch9 is partially localized at the vacuolar surface, where it is phosphorylated by TORC1. The recruitment of Sch9 on the vacuole is mediated by direct interaction between phospholipids of the vacuolar membrane and the region of Sch9 encompassing amino acid residues 1-390, which contains a C2 domain. Since many C2 domains mediate phospholipid binding, it had been suggested that the C2 domain of Sch9 mediates its vacuolar recruitment. However, the in vivo requirement of the C2 domain for Sch9 localization had not been demonstrated, and the phenotypic consequences of Sch9 delocalization remained unknown. Here, by examining cellular localization, phosphorylation state and growth phenotypes of Sch9 truncation mutants, we show that deletion of the N-terminal domain of Sch9 (aa 1-182), but not the C2 domain (aa 183-399), impairs vacuolar localization and TORC1-dependent phosphorylation of Sch9, while causing growth defects similar to those observed in Sch9Δ cells. These defects can be reversed either via artificial tethering of the protein to the vacuole, or by introducing phosphomimetic mutations at the TORC1 target sites, suggesting that Sch9 localization on the vacuole is needed for the TORC1-dependent activation of the kinase. Our study uncovers a key role for the N-terminal domain of Sch9 and provides new mechanistic insight into the regulation of a major TORC1 signaling branch.
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Affiliation(s)
- Daniele Novarina
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Paolo Guerra
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands
| | - Andreas Milias-Argeitis
- Molecular Systems Biology, Groningen Biomolecular Sciences and Biotechnology Institute, University of Groningen, Nijenborgh 4, 9747 AG Groningen, the Netherlands.
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11
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PHLPPing the balance: restoration of protein kinase C in cancer. Biochem J 2021; 478:341-355. [PMID: 33502516 DOI: 10.1042/bcj20190765] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2020] [Revised: 12/22/2020] [Accepted: 01/04/2021] [Indexed: 12/28/2022]
Abstract
Protein kinase signalling, which transduces external messages to mediate cellular growth and metabolism, is frequently deregulated in human disease, and specifically in cancer. As such, there are 77 kinase inhibitors currently approved for the treatment of human disease by the FDA. Due to their historical association as the receptors for the tumour-promoting phorbol esters, PKC isozymes were initially targeted as oncogenes in cancer. However, a meta-analysis of clinical trials with PKC inhibitors in combination with chemotherapy revealed that these treatments were not advantageous, and instead resulted in poorer outcomes and greater adverse effects. More recent studies suggest that instead of inhibiting PKC, therapies should aim to restore PKC function in cancer: cancer-associated PKC mutations are generally loss-of-function and high PKC protein is protective in many cancers, including most notably KRAS-driven cancers. These recent findings have reframed PKC as having a tumour suppressive function. This review focusses on a potential new mechanism of restoring PKC function in cancer - through targeting of its negative regulator, the Ser/Thr protein phosphatase PHLPP. This phosphatase regulates PKC steady-state levels by regulating the phosphorylation of a key site, the hydrophobic motif, whose phosphorylation is necessary for the stability of the enzyme. We also consider whether the phosphorylation of the potent oncogene KRAS provides a mechanism by which high PKC expression may be protective in KRAS-driven human cancers.
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12
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Baffi TR, Lordén G, Wozniak JM, Feichtner A, Yeung W, Kornev AP, King CC, Del Rio JC, Limaye AJ, Bogomolovas J, Gould CM, Chen J, Kennedy EJ, Kannan N, Gonzalez DJ, Stefan E, Taylor SS, Newton AC. mTORC2 controls the activity of PKC and Akt by phosphorylating a conserved TOR interaction motif. Sci Signal 2021; 14:eabe4509. [PMID: 33850054 PMCID: PMC8208635 DOI: 10.1126/scisignal.abe4509] [Citation(s) in RCA: 53] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The complex mTORC2 is accepted to be the kinase that controls the phosphorylation of the hydrophobic motif, a key regulatory switch for AGC kinases, although whether mTOR directly phosphorylates this motif remains controversial. Here, we identified an mTOR-mediated phosphorylation site that we termed the TOR interaction motif (TIM; F-x3-F-pT), which controls the phosphorylation of the hydrophobic motif of PKC and Akt and the activity of these kinases. The TIM is invariant in mTORC2-dependent AGC kinases, is evolutionarily conserved, and coevolved with mTORC2 components. Mutation of this motif in Akt1 and PKCβII abolished cellular kinase activity by impairing activation loop and hydrophobic motif phosphorylation. mTORC2 directly phosphorylated the PKC TIM in vitro, and this phosphorylation event was detected in mouse brain. Overexpression of PDK1 in mTORC2-deficient cells rescued hydrophobic motif phosphorylation of PKC and Akt by a mechanism dependent on their intrinsic catalytic activity, revealing that mTORC2 facilitates the PDK1 phosphorylation step, which, in turn, enables autophosphorylation. Structural analysis revealed that PKC homodimerization is driven by a TIM-containing helix, and biophysical proximity assays showed that newly synthesized, unphosphorylated PKC dimerizes in cells. Furthermore, disruption of the dimer interface by stapled peptides promoted hydrophobic motif phosphorylation. Our data support a model in which mTORC2 relieves nascent PKC dimerization through TIM phosphorylation, recruiting PDK1 to phosphorylate the activation loop and triggering intramolecular hydrophobic motif autophosphorylation. Identification of TIM phosphorylation and its role in the regulation of PKC provides the basis for AGC kinase regulation by mTORC2.
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Affiliation(s)
- Timothy R Baffi
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093, USA
| | - Gema Lordén
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
| | - Jacob M Wozniak
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, CA 92093, USA
| | - Andreas Feichtner
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck A-6020, Austria
| | - Wayland Yeung
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Alexandr P Kornev
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
| | - Charles C King
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
| | - Jason C Del Rio
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093, USA
| | - Ameya J Limaye
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602, USA
| | - Julius Bogomolovas
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Christine M Gould
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
- Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093, USA
| | - Ju Chen
- Department of Medicine, University of California at San Diego, La Jolla, CA 92093, USA
| | - Eileen J Kennedy
- Department of Pharmaceutical and Biomedical Sciences, College of Pharmacy, University of Georgia, Athens, GA 30602, USA
| | - Natarajan Kannan
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - David J Gonzalez
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California at San Diego, La Jolla, CA 92093, USA
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences, University of Innsbruck, Innsbruck A-6020, Austria
| | - Susan S Taylor
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA
- Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA 92093, USA
| | - Alexandra C Newton
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA.
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13
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Lemos Duarte M, Trimbake NA, Gupta A, Tumanut C, Fan X, Woods C, Ram A, Gomes I, Bobeck EN, Schechtman D, Devi LA. High-throughput screening and validation of antibodies against synaptic proteins to explore opioid signaling dynamics. Commun Biol 2021; 4:238. [PMID: 33619305 PMCID: PMC7900253 DOI: 10.1038/s42003-021-01744-8] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2019] [Accepted: 11/13/2020] [Indexed: 12/12/2022] Open
Abstract
Antibodies represent powerful tools to examine signal transduction pathways. Here, we present a strategy integrating multiple state-of-the-art methods to produce, validate, and utilize antibodies. Focusing on understudied synaptic proteins, we generated 137 recombinant antibodies. We used yeast display antibody libraries from the B cells of immunized rabbits, followed by FACS sorting under stringent conditions to identify high affinity antibodies. The antibodies were validated by high-throughput functional screening, and genome editing. Next, we explored the temporal dynamics of signaling in single cells. A subset of antibodies targeting opioid receptors were used to examine the effect of treatment with opiates that have played central roles in the worsening of the 'opioid epidemic.' We show that morphine and fentanyl exhibit differential temporal dynamics of receptor phosphorylation. In summary, high-throughput approaches can lead to the identification of antibody-based tools required for an in-depth understanding of the temporal dynamics of opioid signaling.
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Affiliation(s)
- Mariana Lemos Duarte
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
| | - Nikita A Trimbake
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
- Regeneron Pharmaceutical, 777 Old Saw Mill River Rd, Tarrytown, NY, 10591, USA
| | - Achla Gupta
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
| | | | - Xiaomin Fan
- AvantGen Inc., 6162 Nancy Ridge Dr #150, San Diego, CA, 92121, USA
| | - Catherine Woods
- AvantGen Inc., 6162 Nancy Ridge Dr #150, San Diego, CA, 92121, USA
| | - Akila Ram
- Department of Biology, Utah State University, Logan, UT, 84322, USA
| | - Ivone Gomes
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA
| | - Erin N Bobeck
- Department of Biology, Utah State University, Logan, UT, 84322, USA
| | - Deborah Schechtman
- Department of Biochemistry, University of São Paulo, 748 Av Prof Lineu Prestes, room 1208 Cidade Universitaria, São Paulo, SP, 05508000, Brazil
| | - Lakshmi A Devi
- Department of Pharmacological Sciences, Icahn School of Medicine at Mount Sinai, One Gustave L. Levy Place, Box 1603, New York City, NY, 10029, USA.
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14
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Sun Y, Zhao JY, Li YT, Zhang PG, Wang SP, Guo J, Chen J, Zhou YB, Chen M, Ma YZ, Fang ZW, Xu ZS. Genome-Wide Analysis of the C2 Domain Family in Soybean and Identification of a Putative Abiotic Stress Response Gene GmC2-148. FRONTIERS IN PLANT SCIENCE 2021; 12:620544. [PMID: 33692816 PMCID: PMC7939022 DOI: 10.3389/fpls.2021.620544] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/23/2020] [Accepted: 01/05/2021] [Indexed: 05/24/2023]
Abstract
Plant C2 domain proteins play essential biological functions in numerous plants. In this study, 180 soybean C2 domain genes were identified by screening. Phylogenetic relationship analysis revealed that C2 domain genes fell into three distinct groups with diverged gene structure and conserved functional domain. Chromosomal location analysis indicated that C2 domain genes mapped to 20 chromosomes. The transcript profiles based on RNA-seq data showed that GmC2-58, GmC2-88, and GmC2-148 had higher levels of expression under salt, drought, and abscisic acid (ABA) treatments. GmC2-148, encoding a cell membrane-localized protein, had the highest level of response to various treatments according to real-time quantitative polymerase chain reaction (RT-qPCR) analysis. Under salt and drought stresses, the soybean plants with GmC2-148 transgenic hairy roots showed delayed leaf rolling, a higher content of proline (Pro), and lower contents of H2O2, O2- and malondialdehyde (MDA) compared to those of the empty vector (EV) plants. The results of transgenic Arabidopsis in salt and drought treatments were consistent with those in soybean treatments. In addition, the soybean plants with GmC2-148 transgenic hairy roots increased transcript levels of several abiotic stress-related marker genes, including COR47, NCDE3, NAC11, WRKY13, DREB2A, MYB84, bZIP44, and KIN1 which resulted in enhanced abiotic stress tolerance in soybean. These results indicate that C2 domain genes are involved in response to salt and drought stresses, and this study provides a genome-wide analysis of the C2 domain family in soybean.
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Affiliation(s)
- Yue Sun
- College of Agriculture, Yangtze University, Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, Jingzhou, China
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - Juan-Ying Zhao
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - Yi-Tong Li
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - Pei-Gen Zhang
- College of Agriculture, Yangtze University, Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, Jingzhou, China
| | - Shu-Ping Wang
- College of Agriculture, Yangtze University, Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, Jingzhou, China
| | - Jun Guo
- State Key Laboratory of Crop Stress Biology for Arid Areas, College of Plant Protection, Northwest A&F University, Shaanxi, China
| | - Jun Chen
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - Yong-Bin Zhou
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - Ming Chen
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - You-Zhi Ma
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
| | - Zheng-Wu Fang
- College of Agriculture, Yangtze University, Hubei Collaborative Innovation Center for Grain Industry, Engineering Research Center of Ecology and Agricultural Use of Wetland, Ministry of Education, Jingzhou, China
| | - Zhao-Shi Xu
- Institute of Crop Science, Chinese Academy of Agricultural Sciences (CAAS), National Key Facility for Crop Gene Resources and Genetic Improvement, Key Laboratory of Biology and Genetic Improvement of Triticeae Crops, Ministry of Agriculture, Beijing, China
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15
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Lippert LG, Ma N, Ritt M, Jain A, Vaidehi N, Sivaramakrishnan S. Kinase inhibitors allosterically disrupt a regulatory interaction to enhance PKCα membrane translocation. J Biol Chem 2021; 296:100339. [PMID: 33508318 PMCID: PMC7949123 DOI: 10.1016/j.jbc.2021.100339] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2020] [Revised: 01/14/2021] [Accepted: 01/22/2021] [Indexed: 10/28/2022] Open
Abstract
The eukaryotic kinase domain has multiple intrinsically disordered regions whose conformation dictates kinase activity. Small molecule kinase inhibitors (SMKIs) rely on disrupting the active conformations of these disordered regions to inactivate the kinase. While SMKIs are selected for their ability to cause this disruption, the allosteric effects of conformational changes in disordered regions is limited by a lack of dynamic information provided by traditional structural techniques. In this study, we integrated multiscale molecular dynamics simulations with FRET sensors to characterize a novel allosteric mechanism that is selectively triggered by SMKI binding to the protein kinase Cα domain. The indole maleimide inhibitors BimI and sotrastaurin were found to displace the Gly-rich loop (G-loop) that normally shields the ATP-binding site. Displacement of the G-loop interferes with a newly identified, structurally conserved binding pocket for the C1a domain on the N lobe of the kinase domain. This binding pocket, in conjunction with the N-terminal regulatory sequence, masks a diacylglycerol (DAG) binding site on the C1a domain. SMKI-mediated displacement of the G-loop released C1a and exposed the DAG binding site, enhancing protein kinase Cα translocation both to synthetic lipid bilayers and to live cell membranes in the presence of DAG. Inhibitor chemotype determined the extent of the observed allosteric effects on the kinase domain and correlated with the extent of membrane recruitment. Our findings demonstrate the allosteric effects of SMKIs beyond the confines of kinase catalytic conformation and provide an integrated computational-experimental paradigm to investigate parallel mechanisms in other kinases.
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Affiliation(s)
- Lisa G Lippert
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, USA
| | - Ning Ma
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA
| | - Michael Ritt
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, USA
| | - Abhinandan Jain
- The Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California, USA
| | - Nagarajan Vaidehi
- Department of Computational and Quantitative Medicine, Beckman Research Institute of the City of Hope, Duarte, California, USA.
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota, USA.
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16
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Parker PJ, Brown SJ, Calleja V, Chakravarty P, Cobbaut M, Linch M, Marshall JJT, Martini S, McDonald NQ, Soliman T, Watson L. Equivocal, explicit and emergent actions of PKC isoforms in cancer. Nat Rev Cancer 2021; 21:51-63. [PMID: 33177705 DOI: 10.1038/s41568-020-00310-4] [Citation(s) in RCA: 32] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Accepted: 10/02/2020] [Indexed: 01/02/2023]
Abstract
The maturing mutational landscape of cancer genomes, the development and application of clinical interventions and evolving insights into tumour-associated functions reveal unexpected features of the protein kinase C (PKC) family of serine/threonine protein kinases. These advances include recent work showing gain or loss-of-function mutations relating to driver or bystander roles, how conformational constraints and plasticity impact this class of proteins and how emergent cancer-associated properties may offer opportunities for intervention. The profound impact of the tumour microenvironment, reflected in the efficacy of immune checkpoint interventions, further prompts to incorporate PKC family actions and interventions in this ecosystem, informed by insights into the control of stromal and immune cell functions. Drugging PKC isoforms has offered much promise, but when and how is not obvious.
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Affiliation(s)
- Peter J Parker
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK.
- School of Cancer and Pharmaceutical Sciences, King's College London, Guy's Campus, London, UK.
| | - Sophie J Brown
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
| | - Veronique Calleja
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
| | | | - Mathias Cobbaut
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
| | - Mark Linch
- UCL Cancer Institute, University College London, London, UK
| | | | - Silvia Martini
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
| | - Neil Q McDonald
- Signalling and Structural Biology Laboratory, Francis Crick Institute, London, UK
- Institute of Structural and Molecular Biology, Department of Biological Sciences, Birkbeck College, London, UK
| | - Tanya Soliman
- Centre for Cancer Genomics and Computational Biology, Bart's Cancer Institute, London, UK
| | - Lisa Watson
- Protein Phosphorylation Laboratory, Francis Crick Institute, London, UK
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17
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Gupte TM, Ritt M, Sivaramakrishnan S. ER/K-link-Leveraging a native protein linker to probe dynamic cellular interactions. Methods Enzymol 2020; 647:173-208. [PMID: 33482988 PMCID: PMC8009693 DOI: 10.1016/bs.mie.2020.10.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
ER/K α-helices are a subset of single alpha helical domains, which exhibit unusual stability as isolated protein secondary structures. They adopt an elongated structural conformation, while regulating the frequency of interactions between proteins or polypeptides fused to their ends. Here we review recent advances on the structure, stability and function of ER/K α-helices as linkers (ER/K linkers) in native proteins. We describe methodological considerations in the molecular cloning, protein expression and measurement of interaction strengths, using sensors incorporating ER/K linkers. We highlight biological insights obtained over the last decade by leveraging distinct biophysical features of ER/K-linked sensors. We conclude with the outlook for the use of ER/K linkers in the selective modulation of dynamic cellular interactions.
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Affiliation(s)
- Tejas M Gupte
- Department of Genetics, Cell Biology, and Development, College of Biological Sciences, University of Minnesota, Minneapolis, MN, United States
| | - Michael Ritt
- Department of Genetics, Cell Biology, and Development, College of Biological Sciences, University of Minnesota, Minneapolis, MN, United States
| | - Sivaraj Sivaramakrishnan
- Department of Genetics, Cell Biology, and Development, College of Biological Sciences, University of Minnesota, Minneapolis, MN, United States.
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18
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Jones AC, Taylor SS, Newton AC, Kornev AP. Hypothesis: Unifying model of domain architecture for conventional and novel protein kinase C isozymes. IUBMB Life 2020; 72:2584-2590. [PMID: 33166426 DOI: 10.1002/iub.2401] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Revised: 10/17/2020] [Accepted: 10/17/2020] [Indexed: 12/26/2022]
Abstract
Protein kinase C (PKC) family members are multi-domain proteins whose function is exquisitely tuned by interdomain interactions that control the spatiotemporal dynamics of their signaling. Despite extensive mechanistic studies on this family of enzymes, no structure of a full-length enzyme that includes all domains has been solved. Here, we take into account the biochemical mechanisms that control autoinhibition, the properties of each individual domain, and previous structural studies to propose a unifying model for the general architecture of PKC family members. This model shows how the C2 domains of conventional and novel PKC isozymes, which have different topologies and different positions in the primary structure, can occupy the same position in the tertiary structure of the kinase. This common architecture of conventional and novel PKC isozymes provides a framework for understanding how disease-associated mutations impair PKC function.
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Affiliation(s)
- Alexander C Jones
- Department of Pharmacology, University of California, San Diego, La Jolla, California, USA.,Biomedical Sciences Graduate Program, University of California, La Jolla, California, USA
| | - Susan S Taylor
- Department of Pharmacology, University of California, San Diego, La Jolla, California, USA
| | - Alexandra C Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, California, USA
| | - Alexandr P Kornev
- Department of Pharmacology, University of California, San Diego, La Jolla, California, USA
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19
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Enzler F, Tschaikner P, Schneider R, Stefan E. KinCon: Cell-based recording of full-length kinase conformations. IUBMB Life 2020; 72:1168-1174. [PMID: 32027084 PMCID: PMC7318358 DOI: 10.1002/iub.2241] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2019] [Accepted: 01/16/2020] [Indexed: 01/26/2023]
Abstract
The spectrum of kinase alterations displays distinct functional characteristics and requires kinase mutation-oriented strategies for therapeutic interference. Besides phosphotransferase activity, protein abundance, and intermolecular interactions, particular patient-mutations promote pathological kinase conformations. Despite major advances in identifying lead molecules targeting clinically relevant oncokinase functions, still many kinases are neglected and not part of drug discovery efforts. One explanation is attributed to challenges in tracking kinase activities. Chemical probes are needed to functionally annotate kinase functions, whose activities may not always depend on catalyzing phospho-transfer. Such non-catalytic kinase functions are related to transitions of full-length kinase conformations. Recent findings underline that cell-based reporter systems can be adapted to record conformation changes of kinases. Here, we discuss the possible applications of an extendable kinase conformation (KinCon) reporter toolbox for live-cell recording of kinase states. KinCon is a genetically encoded bioluminescence-based biosensor platform, which can be subjected for measurements of conformation dynamics of mutated kinases upon small molecule inhibitor exposure. We hypothesize that such biosensors can be utilized to delineate the molecular modus operandi for kinase and pseudokinase regulation. This should pave the path for full-length kinase-targeted drug discovery efforts aiming to identify single and combinatory kinase inhibitor therapies with increased specificity and efficacy.
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Affiliation(s)
- Florian Enzler
- Institute of Biochemistry and Center for Molecular Biosciences, University of InnsbruckInnsbruckAustria
| | - Philipp Tschaikner
- Institute of Biochemistry and Center for Molecular Biosciences, University of InnsbruckInnsbruckAustria
| | - Rainer Schneider
- Institute of Biochemistry and Center for Molecular Biosciences, University of InnsbruckInnsbruckAustria
| | - Eduard Stefan
- Institute of Biochemistry and Center for Molecular Biosciences, University of InnsbruckInnsbruckAustria
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20
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Zhang X, Min X, Zhu A, Kim KM. A novel molecular mechanism involved in the crosstalks between homologous and PKC-mediated heterologous regulatory pathway of dopamine D2 receptor. Biochem Pharmacol 2020; 174:113791. [DOI: 10.1016/j.bcp.2020.113791] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2019] [Accepted: 01/02/2020] [Indexed: 11/15/2022]
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21
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Lipid-targeting pleckstrin homology domain turns its autoinhibitory face toward the TEC kinases. Proc Natl Acad Sci U S A 2019; 116:21539-21544. [PMID: 31591208 PMCID: PMC6815127 DOI: 10.1073/pnas.1907566116] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Bruton’s tyrosine kinase (BTK) is targeted in treatment of immune cancers. As patients experience drug resistance, there is a need for alternative approaches to inhibit BTK. Other recently published findings clarify the role of the BTK pleckstrin homology (PH) domain in mediating activation via dimerization and sensing of ligand concentration at the membrane. Work presented here provides insight into the autoinhibitory BTK structure that has so far been elusive via crystallographic methods. In the resting state, the BTK PH domain binds to the activation loop face of the kinase domain and allosterically alters key sites within the kinase domain. The findings define a new regulatory site, the PH/kinase interface, that can be exploited in drug discovery efforts. The pleckstrin homology (PH) domain is well known for its phospholipid targeting function. The PH-TEC homology (PHTH) domain within the TEC family of tyrosine kinases is also a crucial component of the autoinhibitory apparatus. The autoinhibitory surface on the PHTH domain has been previously defined, and biochemical investigations have shown that PHTH-mediated inhibition is mutually exclusive with phosphatidylinositol binding. Here we use hydrogen/deuterium exchange mass spectrometry, nuclear magnetic resonance (NMR), and evolutionary sequence comparisons to map where and how the PHTH domain affects the Bruton’s tyrosine kinase (BTK) domain. The data map a PHTH-binding site on the activation loop face of the kinase C lobe, suggesting that the PHTH domain masks the activation loop and the substrate-docking site. Moreover, localized NMR spectral changes are observed for non–surface-exposed residues in the active site and on the distal side of the kinase domain. These data suggest that the association of PHTH induces allosteric conformational shifts in regions of the kinase domain that are critical for catalysis. Through statistical comparisons of diverse tyrosine kinase sequences, we identify residues unique to BTK that coincide with the experimentally determined PHTH-binding surface on the kinase domain. Our data provide a more complete picture of the autoinhibitory conformation adopted by full-length TEC kinases, creating opportunities to target the regulatory domains to control the function of these kinases in a biological setting.
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22
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Sun XD, Wang A, Ma P, Gong S, Tao J, Yu XM, Jiang X. Regulation of the firing activity by PKA-PKC-Src family kinases in cultured neurons of hypothalamic arcuate nucleus. J Neurosci Res 2019; 98:384-403. [PMID: 31407399 PMCID: PMC6916362 DOI: 10.1002/jnr.24516] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2018] [Revised: 07/18/2019] [Accepted: 07/30/2019] [Indexed: 12/19/2022]
Abstract
The cAMP‐dependent protein kinase A family (PKAs), protein kinase C family (PKCs), and Src family kinases (SFKs) are found to play important roles in pain hypersensitivity. However, more detailed investigations are still needed in order to understand the mechanisms underlying the actions of PKAs, PKCs, and SFKs. Neurons in the hypothalamic arcuate nucleus (ARC) are found to be involved in the regulation of pain hypersensitivity. Here we report that the action potential (AP) firing activity of ARC neurons in culture was up‐regulated by application of the adenylate cyclase activator forskolin or the PKC activator PMA, and that the forskolin or PMA application‐induced up‐regulation of AP firing activity could be blocked by pre‐application of the SFK inhibitor PP2. SFK activation also up‐regulated the AP firing activity and this effect could be prevented by pre‐application of the inhibitors of PKCs, but not of PKAs. Furthermore, we identified that forskolin or PMA application caused increases in the phosphorylation not only in PKAs at T197 or PKCs at S660 and PKCα/βII at T638/641, but also in SFKs at Y416. The forskolin or PMA application‐induced increase in the phosphorylation of PKAs or PKCs was not affected by pre‐treatment with PP2. The regulations of the SFK and AP firing activities by PKCs were independent upon the translocation of either PKCα or PKCβII. Thus, it is demonstrated that PKAs may act as an upstream factor(s) to enhance SFKs while PKCs and SFKs interact reciprocally, and thereby up‐regulate the AP firing activity in hypothalamic ARC neurons.
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Affiliation(s)
- Xiao-Dong Sun
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
| | - Anqi Wang
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
| | - Peng Ma
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
| | - Shan Gong
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
| | - Jin Tao
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
| | - Xian-Min Yu
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
| | - Xinghong Jiang
- Key Laboratory of Pain Basic Research and Clinical Therapy, Department of Physiology and Neurobiology, Medical College of Soochow University, Suzhou, China
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23
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Taylor SS, Meharena HS, Kornev AP. Evolution of a dynamic molecular switch. IUBMB Life 2019; 71:672-684. [PMID: 31059206 DOI: 10.1002/iub.2059] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2019] [Accepted: 04/18/2019] [Indexed: 12/20/2022]
Abstract
Eukaryotic protein kinases (EPKs) regulate almost every biological process and have evolved to be dynamic molecular switches; this is in stark contrast to metabolic enzymes, which have evolved to be efficient catalysts. In particular, the highly conserved active site of every EPK is dynamically and transiently assembled by a process that is highly regulated and unique for every protein kinase. We review here the essential features of the kinase core, focusing on the conserved motifs and residues that are embedded in every kinase. We explore, in particular, how the hydrophobic core architecture specifically drives the dynamic assembly of the regulatory spine and consequently the organization of the active site where the γ-phosphate of ATP is positioned by a convergence of conserved motifs including a conserved regulatory triad for transfer to a protein substrate. In conclusion, we show how the flanking N- and C-terminal tails often classified as intrinsically disordered regions, as well as flanking domains, contribute in a highly kinase-specific manner to the regulation of the conserved kinase core. Understanding this process as well as how one kinase activates another remains as two of the big challenges for the kinase signaling community. © 2019 IUBMB Life, 71(6):672-684, 2019.
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Affiliation(s)
- Susan S Taylor
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA.,Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, CA, USA
| | - Hiruy S Meharena
- Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA, USA
| | - Alexandr P Kornev
- Department of Pharmacology, University of California, San Diego, La Jolla, CA, USA
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24
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Gleason CE, Oses-Prieto JA, Li KH, Saha B, Situ G, Burlingame AL, Pearce D. Phosphorylation at distinct subcellular locations underlies specificity in mTORC2-mediated activation of SGK1 and Akt. J Cell Sci 2019; 132:jcs.224931. [PMID: 30837283 DOI: 10.1242/jcs.224931] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Accepted: 02/21/2019] [Indexed: 02/04/2023] Open
Abstract
mTORC2 lies at the intersection of signaling pathways that control metabolism and ion transport through phosphorylation of the AGC-family kinases, the Akt and SGK1 proteins. How mTORC2 targets these functionally distinct downstream effectors in a context-specific manner is not known. Here, we show that the salt- and blood pressure-regulatory hormone, angiotensin II (AngII) stimulates selective mTORC2-dependent phosphorylation of SGK1 (S422) but not Akt (S473 and equivalent sites). Conventional PKC (cPKC), a critical mediator of the angiotensin type I receptor (AT1R, also known as AGTR1) signaling, regulates the subcellular localization of SIN1 (also known as MAPKAP1) and SGK1. Inhibition of cPKC catalytic activity disturbs SIN1 and SGK1 subcellular localization, re-localizing them from the nucleus and a perinuclear compartment to the plasma membrane in advance of hormonal stimulation. Surprisingly, pre-targeting of SIN1 and SGK1 to the plasma membrane prevents SGK1 S422 but not Akt S473 phosphorylation. Additionally, we identify three sites on SIN1 (S128, S315 and S356) that are phosphorylated in response to cPKC activation. Collectively, these data demonstrate that SGK1 activation occurs at a distinct subcellular compartment from that of Akt and suggests a mechanism for the selective activation of these functionally distinct mTORC2 targets through subcellular partitioning of mTORC2 activity.
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Affiliation(s)
- Catherine E Gleason
- Department of Medicine, Division of Nephrology, UCSF, San Francisco, CA 94143, USA
| | - Juan A Oses-Prieto
- Departments of Chemistry and Pharmaceutical Chemistry, UCSF, San Francisco, CA 94143, USA
| | - Kathy H Li
- Departments of Chemistry and Pharmaceutical Chemistry, UCSF, San Francisco, CA 94143, USA
| | - Bidisha Saha
- Department of Medicine, Division of Nephrology, UCSF, San Francisco, CA 94143, USA
| | - Gavin Situ
- Department of Medicine, Division of Nephrology, UCSF, San Francisco, CA 94143, USA
| | - Alma L Burlingame
- Departments of Chemistry and Pharmaceutical Chemistry, UCSF, San Francisco, CA 94143, USA
| | - David Pearce
- Department of Medicine, Division of Nephrology, UCSF, San Francisco, CA 94143, USA
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25
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Yang Y, Shu C, Li P, Igumenova TI. Structural Basis of Protein Kinase Cα Regulation by the C-Terminal Tail. Biophys J 2019; 114:1590-1603. [PMID: 29642029 DOI: 10.1016/j.bpj.2017.12.030] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2017] [Revised: 12/07/2017] [Accepted: 12/21/2017] [Indexed: 10/17/2022] Open
Abstract
Protein kinase C (PKC) isoenzymes are multi-modular proteins activated at the membrane surface to regulate signal transduction processes. When activated by second messengers, PKC undergoes a drastic conformational and spatial transition from the inactive cytosolic state to the activated membrane-bound state. The complete structure of either state of PKC remains elusive. We demonstrate, using NMR spectroscopy, that the isolated Ca2+-sensing membrane-binding C2 domain of the conventional PKCα interacts with a conserved hydrophobic motif of the kinase C-terminal region, and we report a structural model of the complex. Our data suggest that the C-terminal region plays a dual role in regulating the PKC activity: activating, through sensitization of PKC to intracellular Ca2+ oscillations; and auto-inhibitory, through its interaction with a conserved positively charged region of the C2 domain.
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Affiliation(s)
- Yuan Yang
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas
| | - Chang Shu
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas
| | - Pingwei Li
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas.
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26
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Baffi TR, Van AAN, Zhao W, Mills GB, Newton AC. Protein Kinase C Quality Control by Phosphatase PHLPP1 Unveils Loss-of-Function Mechanism in Cancer. Mol Cell 2019; 74:378-392.e5. [PMID: 30904392 DOI: 10.1016/j.molcel.2019.02.018] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2018] [Revised: 12/26/2018] [Accepted: 02/12/2019] [Indexed: 02/02/2023]
Abstract
Protein kinase C (PKC) isozymes function as tumor suppressors in increasing contexts. In contrast to oncogenic kinases, whose function is acutely regulated by transient phosphorylation, PKC is constitutively phosphorylated following biosynthesis to yield a stable, autoinhibited enzyme that is reversibly activated by second messengers. Here, we report that the phosphatase PHLPP1 opposes PKC phosphorylation during maturation, leading to the degradation of aberrantly active species that do not become autoinhibited. Cancer-associated hotspot mutations in the pseudosubstrate of PKCβ that impair autoinhibition result in dephosphorylated and unstable enzymes. Protein-level analysis reveals that PKCα is fully phosphorylated at the PHLPP site in over 5,000 patient tumors, with higher PKC levels correlating (1) inversely with PHLPP1 levels and (2) positively with improved survival in pancreatic adenocarcinoma. Thus, PHLPP1 provides a proofreading step that maintains the fidelity of PKC autoinhibition and reveals a prominent loss-of-function mechanism in cancer by suppressing the steady-state levels of PKC.
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Affiliation(s)
- Timothy R Baffi
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA; Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093, USA
| | - An-Angela N Van
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA; Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, CA 92093, USA
| | - Wei Zhao
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Gordon B Mills
- Department of Systems Biology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA
| | - Alexandra C Newton
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92093, USA.
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27
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Abstract
Protein kinase C (PKC) isozymes belong to a family of Ser/Thr kinases whose activity is governed by reversible release of an autoinhibitory pseudosubstrate. For conventional and novel isozymes, this is effected by binding the lipid second messenger, diacylglycerol, but for atypical PKC isozymes, this is effected by binding protein scaffolds. PKC shot into the limelight following the discovery in the 1980s that the diacylglycerol-sensitive isozymes are "receptors" for the potent tumor-promoting phorbol esters. This set in place a concept that PKC isozymes are oncoproteins. Yet three decades of cancer clinical trials targeting PKC with inhibitors failed and, in some cases, worsened patient outcome. Emerging evidence from cancer-associated mutations and protein expression levels provide a reason: PKC isozymes generally function as tumor suppressors and their activity should be restored, not inhibited, in cancer therapies. And whereas not enough activity is associated with cancer, variants with enhanced activity are associated with degenerative diseases such as Alzheimer's disease. This review describes the tightly controlled mechanisms that ensure PKC activity is perfectly balanced and what happens when these controls are deregulated. PKC isozymes serve as a paradigm for the wisdom of Confucius: "to go beyond is as wrong as to fall short."
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Affiliation(s)
- Alexandra C Newton
- a Department of Pharmacology , University of California at San Diego , La Jolla , CA , USA
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28
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Brunger AT, Leitz J, Zhou Q, Choi UB, Lai Y. Ca 2+-Triggered Synaptic Vesicle Fusion Initiated by Release of Inhibition. Trends Cell Biol 2018; 28:631-645. [PMID: 29706534 PMCID: PMC6056330 DOI: 10.1016/j.tcb.2018.03.004] [Citation(s) in RCA: 37] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/09/2018] [Revised: 03/17/2018] [Accepted: 03/26/2018] [Indexed: 12/20/2022]
Abstract
Recent structural and functional studies of the synaptic vesicle fusion machinery suggest an inhibited tripartite complex consisting of neuronal soluble N-ethylmaleimide sensitive factor attachment protein receptors (SNAREs), synaptotagmin, and complexin prior to Ca2+-triggered synaptic vesicle fusion. We speculate that Ca2+-triggered fusion commences with the release of inhibition by Ca2+ binding to synaptotagmin C2 domains. Subsequently, fusion is assisted by SNARE complex zippering and by active membrane remodeling properties of synaptotagmin. This additional, inhibitory role of synaptotagmin may be a general principle since other recent studies suggest that Ca2+ binding to extended synaptotagmin C2 domains enables lipid transport by releasing an inhibited state of the system, and that Munc13 may nominally be in an inhibited state, which is released upon Ca2+ binding to one of its C2 domains.
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Affiliation(s)
- Axel T Brunger
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA.
| | - Jeremy Leitz
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Qiangjun Zhou
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Ucheor B Choi
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
| | - Ying Lai
- Department of Molecular and Cellular Physiology, Stanford University, Stanford, CA, USA; Department of Neurology and Neurological Sciences, Stanford University, Stanford, CA, USA; Department of Structural Biology, Stanford University, Stanford, CA, USA; Department of Photon Science, Stanford University, Stanford, CA, USA; Howard Hughes Medical Institute, Stanford University, Stanford, CA, USA
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29
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Protein kinase Cα gain-of-function variant in Alzheimer's disease displays enhanced catalysis by a mechanism that evades down-regulation. Proc Natl Acad Sci U S A 2018; 115:E5497-E5505. [PMID: 29844158 DOI: 10.1073/pnas.1805046115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Conventional protein kinase C (PKC) family members are reversibly activated by binding to the second messengers Ca2+ and diacylglycerol, events that break autoinhibitory constraints to allow the enzyme to adopt an active, but degradation-sensitive, conformation. Perturbing these autoinhibitory constraints, resulting in protein destabilization, is one of many mechanisms by which PKC function is lost in cancer. Here, we address how a gain-of-function germline mutation in PKCα in Alzheimer's disease (AD) enhances signaling without increasing vulnerability to down-regulation. Biochemical analyses of purified protein demonstrate that this mutation results in an ∼30% increase in the catalytic rate of the activated enzyme, with no changes in the concentrations of Ca2+ or lipid required for half-maximal activation. Molecular dynamics simulations reveal that this mutation has both localized and allosteric effects, most notably decreasing the dynamics of the C-helix, a key determinant in the catalytic turnover of kinases. Consistent with this mutation not altering autoinhibitory constraints, live-cell imaging studies reveal that the basal signaling output of PKCα-M489V is unchanged. However, the mutant enzyme in cells displays increased sensitivity to an inhibitor that is ineffective toward scaffolded PKC, suggesting the altered dynamics of the kinase domain may influence protein interactions. Finally, we show that phosphorylation of a key PKC substrate, myristoylated alanine-rich C-kinase substrate, is increased in brains of CRISPR-Cas9 genome-edited mice containing the PKCα-M489V mutation. Our results unveil how an AD-associated mutation in PKCα permits enhanced agonist-dependent signaling via a mechanism that evades the cell's homeostatic down-regulation of constitutively active PKCα.
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30
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Berlow RB. A Dual Regulatory Role for the Disordered C-Terminus of Protein Kinase Cα. Biophys J 2018; 114:1513-1514. [PMID: 29642021 DOI: 10.1016/j.bpj.2018.02.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2018] [Accepted: 02/20/2018] [Indexed: 10/17/2022] Open
Affiliation(s)
- Rebecca B Berlow
- Department of Integrative Structural and Computational Biology, The Scripps Research Institute, La Jolla, California.
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31
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Bian X, Saheki Y, De Camilli P. Ca 2+ releases E-Syt1 autoinhibition to couple ER-plasma membrane tethering with lipid transport. EMBO J 2017; 37:219-234. [PMID: 29222176 DOI: 10.15252/embj.201797359] [Citation(s) in RCA: 88] [Impact Index Per Article: 12.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 11/08/2017] [Accepted: 11/10/2017] [Indexed: 11/09/2022] Open
Abstract
The extended synaptotagmins (E-Syts) are endoplasmic reticulum (ER) proteins that bind the plasma membrane (PM) via C2 domains and transport lipids between them via SMP domains. E-Syt1 tethers and transports lipids in a Ca2+-dependent manner, but the role of Ca2+ in this regulation is unclear. Of the five C2 domains of E-Syt1, only C2A and C2C contain Ca2+-binding sites. Using liposome-based assays, we show that Ca2+ binding to C2C promotes E-Syt1-mediated membrane tethering by releasing an inhibition that prevents C2E from interacting with PI(4,5)P2-rich membranes, as previously suggested by studies in semi-permeabilized cells. Importantly, Ca2+ binding to C2A enables lipid transport by releasing a charge-based autoinhibitory interaction between this domain and the SMP domain. Supporting these results, E-Syt1 constructs defective in Ca2+ binding in either C2A or C2C failed to rescue two defects in PM lipid homeostasis observed in E-Syts KO cells, delayed diacylglycerol clearance from the PM and impaired Ca2+-triggered phosphatidylserine scrambling. Thus, a main effect of Ca2+ on E-Syt1 is to reverse an autoinhibited state and to couple membrane tethering with lipid transport.
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Affiliation(s)
- Xin Bian
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA.,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA
| | - Yasunori Saheki
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA .,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA.,Lee Kong Chian School of Medicine, Nanyang Technological University, Singapore, Singapore
| | - Pietro De Camilli
- Department of Neuroscience, Yale University School of Medicine, New Haven, CT, USA .,Department of Cell Biology, Yale University School of Medicine, New Haven, CT, USA.,Howard Hughes Medical Institute, Yale University School of Medicine, New Haven, CT, USA.,Program in Cellular Neuroscience, Neurodegeneration, and Repair, Yale University School of Medicine, New Haven, CT, USA.,Kavli Institute for Neuroscience, Yale University School of Medicine, New Haven, CT, USA
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32
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Heinisch JJ, Rodicio R. Protein kinase C in fungi—more than just cell wall integrity. FEMS Microbiol Rev 2017; 42:4562651. [DOI: 10.1093/femsre/fux051] [Citation(s) in RCA: 52] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/19/2017] [Indexed: 11/13/2022] Open
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33
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Cleavage Alters the Molecular Determinants of Protein Kinase C-δ Catalytic Activity. Mol Cell Biol 2017; 37:MCB.00324-17. [PMID: 28784722 DOI: 10.1128/mcb.00324-17] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2017] [Accepted: 07/18/2017] [Indexed: 01/19/2023] Open
Abstract
Protein kinase C-δ (PKCδ) is an allosterically activated enzyme that acts much like other PKC isoforms to transduce growth factor-dependent signaling responses. However, PKCδ is unique in that activation loop (Thr507) phosphorylation is not required for catalytic activity. Since PKCδ can be proteolytically cleaved by caspase-3 during apoptosis, the prevailing assumption has been that the kinase domain fragment (δKD) freed from autoinhibitory constraints imposed by the regulatory domain is catalytically competent and that Thr507 phosphorylation is not required for δKD activity. This study provides a counternarrative showing that δKD activity is regulated through Thr507 phosphorylation. We show that Thr507-phosphorylated δKD is catalytically active and not phosphorylated at Ser359 in its ATP-positioning G-loop. In contrast, a δKD fragment that is not phosphorylated at Thr507 (which accumulates in doxorubicin-treated cardiomyocytes) displays decreased C-terminal tail priming-site phosphorylation, increased G-loop Ser359 phosphorylation, and defective kinase activity. δKD is not a substrate for Src, but Src phosphorylates δKD-T507A at Tyr334 (in the newly exposed δKD N terminus), and this (or an S359A substitution) rescues δKD-T507A catalytic activity. These results expose a unique role for δKD-Thr507 phosphorylation (that does not apply to full-length PKCδ) in structurally organizing diverse elements within the enzyme that critically regulate catalytic activity.
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34
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Protein kinase C mechanisms that contribute to cardiac remodelling. Clin Sci (Lond) 2017; 130:1499-510. [PMID: 27433023 DOI: 10.1042/cs20160036] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/14/2016] [Accepted: 05/18/2016] [Indexed: 12/12/2022]
Abstract
Protein phosphorylation is a highly-regulated and reversible process that is precisely controlled by the actions of protein kinases and protein phosphatases. Factors that tip the balance of protein phosphorylation lead to changes in a wide range of cellular responses, including cell proliferation, differentiation and survival. The protein kinase C (PKC) family of serine/threonine kinases sits at nodal points in many signal transduction pathways; PKC enzymes have been the focus of considerable attention since they contribute to both normal physiological responses as well as maladaptive pathological responses that drive a wide range of clinical disorders. This review provides a background on the mechanisms that regulate individual PKC isoenzymes followed by a discussion of recent insights into their role in the pathogenesis of diseases such as cancer. We then provide an overview on the role of individual PKC isoenzymes in the regulation of cardiac contractility and pathophysiological growth responses, with a focus on the PKC-dependent mechanisms that regulate pump function and/or contribute to the pathogenesis of heart failure.
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35
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Leroux AE, Schulze JO, Biondi RM. AGC kinases, mechanisms of regulation and innovative drug development. Semin Cancer Biol 2017; 48:1-17. [PMID: 28591657 DOI: 10.1016/j.semcancer.2017.05.011] [Citation(s) in RCA: 92] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/14/2017] [Revised: 05/16/2017] [Accepted: 05/31/2017] [Indexed: 12/22/2022]
Abstract
The group of AGC kinases consists of 63 evolutionarily related serine/threonine protein kinases comprising PDK1, PKB/Akt, SGK, PKC, PRK/PKN, MSK, RSK, S6K, PKA, PKG, DMPK, MRCK, ROCK, NDR, LATS, CRIK, MAST, GRK, Sgk494, and YANK, while two other families, Aurora and PLK, are the most closely related to the group. Eight of these families are physiologically activated downstream of growth factor signalling, while other AGC kinases are downstream effectors of a wide range of signals. The different AGC kinase families share aspects of their mechanisms of inhibition and activation. In the present review, we update the knowledge of the mechanisms of regulation of different AGC kinases. The conformation of the catalytic domain of many AGC kinases is regulated allosterically through the modulation of the conformation of a regulatory site on the small lobe of the kinase domain, the PIF-pocket. The PIF-pocket acts like an ON-OFF switch in AGC kinases with different modes of regulation, i.e. PDK1, PKB/Akt, LATS and Aurora kinases. In this review, we make emphasis on how the knowledge of the molecular mechanisms of regulation can guide the discovery and development of small allosteric modulators. Molecular probes stabilizing the PIF-pocket in the active conformation are activators, while compounds stabilizing the disrupted site are allosteric inhibitors. One challenge for the rational development of allosteric modulators is the lack of complete structural information of the inhibited forms of full-length AGC kinases. On the other hand, we suggest that the available information derived from molecular biology and biochemical studies can already guide screening strategies for the identification of innovative mode of action molecular probes and the development of selective allosteric drugs for the treatment of human diseases.
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Affiliation(s)
- Alejandro E Leroux
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina.
| | - Jörg O Schulze
- Research Group PhosphoSites, Medizinische Klinik 1, Universitätsklinikum Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany.
| | - Ricardo M Biondi
- Instituto de Investigación en Biomedicina de Buenos Aires (IBioBA) - CONICET - Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina; Research Group PhosphoSites, Medizinische Klinik 1, Universitätsklinikum Frankfurt, Theodor-Stern-Kai 7, 60590 Frankfurt am Main, Germany; German Cancer Consortium (DKTK), Heidelberg, Germany, German Cancer Research Center (DKFZ), Heidelberg, Germany.
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36
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Protein kinase C as a tumor suppressor. Semin Cancer Biol 2017; 48:18-26. [PMID: 28476658 DOI: 10.1016/j.semcancer.2017.04.017] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 03/31/2017] [Accepted: 04/28/2017] [Indexed: 01/01/2023]
Abstract
Protein kinase C (PKC) has historically been considered an oncoprotein. This stems in large part from the discovery in the early 1980s that PKC is directly activated by tumor-promoting phorbol esters. Yet three decades of clinical trials using PKC inhibitors in cancer therapies not only failed, but in some cases worsened patient outcome. Why has targeting PKC in cancer eluded successful therapies? Recent studies looking at the disease for insight provide an explanation: cancer-associated mutations in PKC are generally loss-of-function (LOF), supporting an unexpected function as tumor suppressors. And, contrasting with LOF mutations in cancer, germline mutations that enhance the activity of some PKC isozymes are associated with degenerative diseases such as Alzheimer's disease. This review provides a background on the diverse mechanisms that ensure PKC is only active when, where, and for the appropriate duration needed and summarizes recent findings converging on a paradigm reversal: PKC family members generally function by suppressing, rather than promoting, survival signaling.
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37
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Newton AC, Brognard J. Reversing the Paradigm: Protein Kinase C as a Tumor Suppressor. Trends Pharmacol Sci 2017; 38:438-447. [PMID: 28283201 PMCID: PMC5403564 DOI: 10.1016/j.tips.2017.02.002] [Citation(s) in RCA: 72] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2016] [Revised: 02/02/2017] [Accepted: 02/03/2017] [Indexed: 12/20/2022]
Abstract
The discovery in the 1980s that protein kinase C (PKC) is a receptor for the tumor-promoting phorbol esters fueled the dogma that PKC is an oncoprotein. Yet 30+ years of clinical trials for cancer using PKC inhibitors not only failed, but in some instances worsened patient outcome. The recent analysis of cancer-associated mutations, from diverse cancers and throughout the PKC family, revealed that PKC isozymes are generally inactivated in cancer, supporting a tumor suppressive function. In keeping with a bona fide tumor suppressive role, germline causal loss-of-function (LOF) mutations in one isozyme have recently been identified in lymphoproliferative disorders. Thus, strategies in cancer treatment should focus on restoring rather than inhibiting PKC.
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Affiliation(s)
- Alexandra C Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0721, USA.
| | - John Brognard
- Laboratory of Cell and Developmental Signaling, National Cancer Institute at Frederick, Frederick, MD 21702, USA; Cancer Research UK Manchester Institute, Manchester, UK.
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38
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Callender J, Newton A. Conventional protein kinase C in the brain: 40 years later. Neuronal Signal 2017; 1:NS20160005. [PMID: 32714576 PMCID: PMC7373245 DOI: 10.1042/ns20160005] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2016] [Revised: 03/02/2017] [Accepted: 03/07/2017] [Indexed: 12/16/2022] Open
Abstract
Protein kinase C (PKC) is a family of enzymes whose members transduce a large variety of cellular signals instigated by the receptor-mediated hydrolysis of membrane phospholipids. While PKC has been widely implicated in the pathology of diseases affecting all areas of physiology including cancer, diabetes, and heart disease-it was discovered, and initially characterized, in the brain. PKC plays a key role in controlling the balance between cell survival and cell death. Its loss of function is generally associated with cancer, whereas its enhanced activity is associated with neurodegeneration. This review presents an overview of signaling by diacylglycerol (DG)-dependent PKC isozymes in the brain, and focuses on the role of the Ca2+-sensitive conventional PKC isozymes in neurodegeneration.
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Affiliation(s)
- Julia A. Callender
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0721, U.S.A
- Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093-0721, U.S.A
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093-0721, U.S.A
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39
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PKCα diffusion and translocation are independent of an intact cytoskeleton. Sci Rep 2017; 7:475. [PMID: 28352102 PMCID: PMC5428563 DOI: 10.1038/s41598-017-00560-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2016] [Accepted: 03/03/2017] [Indexed: 01/04/2023] Open
Abstract
Translocation of cytosolic cPKC to the plasma membrane is a key event in their activation process but its exact nature is still unclear with particular dispute whether sole diffusion or additional active transport along the cell’s cytoskeleton contributes to cPKC’s dynamics. This was addressed by analyzing the recruitment behavior of PKCα while manipulating the cytoskeleton. Photolytic Ca2+ uncaging allowed us to quantify the kinetics of PKCα redistribution to the plasma membrane when fused to monomeric, dimeric and tetrameric fluorescence proteins. Results indicated that translocation kinetics were modulated by the state of oligomerization as expected for varying Stokes’ radii of the participating proteins. Following depolymerization of the microtubules and the actin filaments we found that Ca2+ induced membrane accumulation of PKCα was independent of the filamentous state of the cytoskeleton. Fusion of PKCα to the photo-convertible fluorescent protein Dendra2 enabled the investigation of PKCα-cytoskeleton interactions under resting conditions. Redistribution following spatially restricted photoconversion showed that the mobility of the fusion protein was independent of the state of the cytoskeleton. Our data demonstrated that in living cells neither actin filaments nor microtubules contribute to PKCα’s cytosolic mobility or Ca2+-induced translocation to the plasma membrane. Instead translocation is a solely diffusion-driven process.
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Sommese RF, Ritt M, Swanson CJ, Sivaramakrishnan S. The Role of Regulatory Domains in Maintaining Autoinhibition in the Multidomain Kinase PKCα. J Biol Chem 2017; 292:2873-2880. [PMID: 28049730 DOI: 10.1074/jbc.m116.768457] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2016] [Revised: 12/30/2016] [Indexed: 11/06/2022] Open
Abstract
Resolving the conformational dynamics of large multidomain proteins has proven to be a significant challenge. Here we use a variety of techniques to dissect the roles of individual protein kinase Cα (PKCα) regulatory domains in maintaining catalytic autoinhibition. We find that whereas the pseudosubstrate domain is necessary for autoinhibition it is not sufficient. Instead, each regulatory domain (C1a, C1b, and C2) appears to strengthen the pseudosubstrate-catalytic domain interaction in a nucleotide-dependent manner. The pseudosubstrate and C1a domains, however, are minimally essential for maintaining the inactivated state. Furthermore, disrupting known interactions between the C1a and other regulatory domains releases the autoinhibited interaction and increases basal activity. Modulating this interaction between the catalytic and regulatory domains reveals a direct correlation between autoinhibition and membrane translocation following PKC activation.
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Affiliation(s)
- Ruth F Sommese
- From the Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455 and
| | - Michael Ritt
- From the Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455 and
| | - Carter J Swanson
- the Biophysics Program, University of Michigan, Ann Arbor, Michigan 48109
| | - Sivaraj Sivaramakrishnan
- From the Department of Genetics, Cell Biology, and Development, University of Minnesota, Minneapolis, Minnesota 55455 and
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Molecular determinants of KA1 domain-mediated autoinhibition and phospholipid activation of MARK1 kinase. Biochem J 2016; 474:385-398. [PMID: 27879374 DOI: 10.1042/bcj20160792] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Revised: 10/11/2016] [Accepted: 11/22/2016] [Indexed: 11/17/2022]
Abstract
Protein kinases are frequently regulated by intramolecular autoinhibitory interactions between protein modules that are reversed when these modules bind other 'activating' protein or membrane-bound targets. One group of kinases, the MAP/microtubule affinity-regulating kinases (MARKs) contain a poorly understood regulatory module, the KA1 (kinase associated-1) domain, at their C-terminus. KA1 domains from MARK1 and several related kinases from yeast to humans have been shown to bind membranes containing anionic phospholipids, and peptide ligands have also been reported. Deleting or mutating the C-terminal KA1 domain has been reported to activate the kinase in which it is found - also suggesting an intramolecular autoinhibitory role. Here, we show that the KA1 domain of human MARK1 interacts with, and inhibits, the MARK1 kinase domain. Using site-directed mutagenesis, we identify residues in the KA1 domain required for this autoinhibitory activity, and find that residues involved in autoinhibition and in anionic phospholipid binding are the same. We also demonstrate that a 'mini' MARK1 becomes activated upon association with vesicles containing anionic phospholipids, but only if the protein is targeted to these vesicles by a second signal. These studies provide a mechanistic basis for understanding how MARK1 and its relatives may require more than one signal at the membrane surface to control their activation at the correct location and time. MARK family kinases have been implicated in a plethora of disease states including Alzheimer's, cancer, and autism, so advancing our understanding of their regulatory mechanisms may ultimately have therapeutic value.
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Alfonso SI, Callender JA, Hooli B, Antal CE, Mullin K, Sherman MA, Lesné SE, Leitges M, Newton AC, Tanzi RE, Malinow R. Gain-of-function mutations in protein kinase Cα (PKCα) may promote synaptic defects in Alzheimer's disease. Sci Signal 2016; 9:ra47. [PMID: 27165780 PMCID: PMC5154619 DOI: 10.1126/scisignal.aaf6209] [Citation(s) in RCA: 72] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Alzheimer's disease (AD) is a progressive dementia disorder characterized by synaptic degeneration and amyloid-β (Aβ) accumulation in the brain. Through whole-genome sequencing of 1345 individuals from 410 families with late-onset AD (LOAD), we identified three highly penetrant variants in PRKCA, the gene that encodes protein kinase Cα (PKCα), in five of the families. All three variants linked with LOAD displayed increased catalytic activity relative to wild-type PKCα as assessed in live-cell imaging experiments using a genetically encoded PKC activity reporter. Deleting PRKCA in mice or adding PKC antagonists to mouse hippocampal slices infected with a virus expressing the Aβ precursor CT100 revealed that PKCα was required for the reduced synaptic activity caused by Aβ. In PRKCA(-/-) neurons expressing CT100, introduction of PKCα, but not PKCα lacking a PDZ interaction moiety, rescued synaptic depression, suggesting that a scaffolding interaction bringing PKCα to the synapse is required for its mediation of the effects of Aβ. Thus, enhanced PKCα activity may contribute to AD, possibly by mediating the actions of Aβ on synapses. In contrast, reduced PKCα activity is implicated in cancer. Hence, these findings reinforce the importance of maintaining a careful balance in the activity of this enzyme.
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Affiliation(s)
- Stephanie I Alfonso
- Department of Neurosciences and Division of Biology, Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA
| | - Julia A Callender
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA. Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Basavaraj Hooli
- Genetics and Aging Research Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Corina E Antal
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA. Biomedical Sciences Graduate Program, University of California, San Diego, La Jolla, CA 92093, USA
| | - Kristina Mullin
- Genetics and Aging Research Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA
| | - Mathew A Sherman
- Department of Neuroscience, N. Bud Grossman Center for Memory Research and Care, and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN 55414, USA
| | - Sylvain E Lesné
- Department of Neuroscience, N. Bud Grossman Center for Memory Research and Care, and Institute for Translational Neuroscience, University of Minnesota, Minneapolis, MN 55414, USA
| | - Michael Leitges
- Biotechnology Centre of Oslo, University of Oslo, Oslo 0317, Norway
| | - Alexandra C Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92093, USA.
| | - Rudolph E Tanzi
- Genetics and Aging Research Unit, Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Charlestown, MA 02129, USA.
| | - Roberto Malinow
- Department of Neurosciences and Division of Biology, Section of Neurobiology, University of California, San Diego, La Jolla, CA 92093, USA.
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43
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Rational design and validation of an anti-protein kinase C active-state specific antibody based on conformational changes. Sci Rep 2016; 6:22114. [PMID: 26911897 PMCID: PMC4766434 DOI: 10.1038/srep22114] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/13/2015] [Accepted: 02/08/2016] [Indexed: 12/15/2022] Open
Abstract
Protein kinase C (PKC) plays a regulatory role in key pathways in cancer. However, since phosphorylation is a step for classical PKC (cPKC) maturation and does not correlate with activation, there is a lack of tools to detect active PKC in tissue samples. Here, a structure-based rational approach was used to select a peptide to generate an antibody that distinguishes active from inactive cPKC. A peptide conserved in all cPKCs, C2Cat, was chosen since modeling studies based on a crystal structure of PKCβ showed that it is localized at the interface between the C2 and catalytic domains of cPKCs in an inactive kinase. Anti-C2Cat recognizes active cPKCs at least two-fold better than inactive kinase in ELISA and immunoprecipitation assays, and detects the temporal dynamics of cPKC activation upon receptor or phorbol stimulation. Furthermore, the antibody is able to detect active PKC in human tissue. Higher levels of active cPKC were observed in the more aggressive triple negative breast cancer tumors as compared to the less aggressive estrogen receptor positive tumors. Thus, this antibody represents a reliable, hitherto unavailable and a valuable tool to study PKC activation in cells and tissues. Similar structure-based rational design strategies can be broadly applied to obtain active-state specific antibodies for other signal transduction molecules.
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Kornev AP, Taylor SS. Dynamics-Driven Allostery in Protein Kinases. Trends Biochem Sci 2015; 40:628-647. [PMID: 26481499 DOI: 10.1016/j.tibs.2015.09.002] [Citation(s) in RCA: 187] [Impact Index Per Article: 20.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Revised: 08/27/2015] [Accepted: 09/01/2015] [Indexed: 01/05/2023]
Abstract
Protein kinases have very dynamic structures and their functionality strongly depends on their dynamic state. Active kinases reveal a dynamic pattern with residues clustering into semirigid communities that move in μs-ms timescale. Previously detected hydrophobic spines serve as connectors between communities. Communities do not follow the traditional subdomain structure of the kinase core or its secondary structure elements. Instead they are organized around main functional units. Integration of the communities depends on the assembly of the hydrophobic spine and phosphorylation of the activation loop. Single mutations can significantly disrupt the dynamic infrastructure and thereby interfere with long-distance allosteric signaling that propagates throughout the whole molecule. Dynamics is proposed to be the underlying mechanism for allosteric regulation in protein kinases.
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Affiliation(s)
- Alexandr P Kornev
- Department of Pharmacology, University of California at San Diego, La Jolla, CA, 92093, USA.
| | - Susan S Taylor
- Department of Pharmacology, University of California at San Diego, La Jolla, CA, 92093, USA; Department of Chemistry and Biochemistry, University of California at San Diego, La Jolla, CA, 92093, USA.
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Tsai LCL, Xie L, Dore K, Xie L, Del Rio JC, King CC, Martinez-Ariza G, Hulme C, Malinow R, Bourne PE, Newton AC. Zeta Inhibitory Peptide Disrupts Electrostatic Interactions That Maintain Atypical Protein Kinase C in Its Active Conformation on the Scaffold p62. J Biol Chem 2015; 290:21845-56. [PMID: 26187466 PMCID: PMC4571940 DOI: 10.1074/jbc.m115.676221] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2015] [Revised: 07/17/2015] [Indexed: 11/06/2022] Open
Abstract
Atypical protein kinase C (aPKC) enzymes signal on protein scaffolds, yet how they are maintained in an active conformation on scaffolds is unclear. A myristoylated peptide based on the autoinhibitory pseudosubstrate fragment of the atypical PKCζ, zeta inhibitory peptide (ZIP), has been extensively used to inhibit aPKC activity; however, we have previously shown that ZIP does not inhibit the catalytic activity of aPKC isozymes in cells (Wu-Zhang, A. X., Schramm, C. L., Nabavi, S., Malinow, R., and Newton, A. C. (2012) J. Biol. Chem. 287, 12879-12885). Here we sought to identify a bona fide target of ZIP and, in so doing, unveiled a novel mechanism by which aPKCs are maintained in an active conformation on a protein scaffold. Specifically, we used protein-protein interaction network analysis, structural modeling, and protein-protein docking to predict that ZIP binds an acidic surface on the Phox and Bem1 (PB1) domain of p62, an interaction validated by peptide array analysis. Using a genetically encoded reporter for PKC activity fused to the p62 scaffold, we show that ZIP inhibits the activity of wild-type aPKC, but not a construct lacking the pseudosubstrate. These data support a model in which the pseudosubstrate of aPKCs is tethered to the acidic surface on p62, locking aPKC in an open, signaling-competent conformation. ZIP competes for binding to the acidic surface, resulting in displacement of the pseudosubstrate of aPKC and re-engagement in the substrate-binding cavity. This study not only identifies a cellular target for ZIP, but also unveils a novel mechanism by which scaffolded aPKC is maintained in an active conformation.
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Affiliation(s)
| | - Lei Xie
- the Department of Computer Science, Hunter College, the City University of New York, New York, New York 10065
| | | | - Li Xie
- Skaggs School of Pharmacy, and
| | | | - Charles C King
- Pediatric Diabetes Research Center, University of California San Diego, La Jolla, California 92093
| | - Guillermo Martinez-Ariza
- the Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, and
| | - Christopher Hulme
- the Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, Tucson, Arizona 85721, and
| | | | - Philip E Bourne
- the Office of the Director, the National Institutes of Health, Bethesda, Maryland 20892
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