1
|
Pihlström S, Richardt S, Määttä K, Pekkinen M, Olkkonen VM, Mäkitie O, Mäkitie RE. SGMS2 in primary osteoporosis with facial nerve palsy. Front Endocrinol (Lausanne) 2023; 14:1224318. [PMID: 37886644 PMCID: PMC10598846 DOI: 10.3389/fendo.2023.1224318] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/25/2023] [Accepted: 09/18/2023] [Indexed: 10/28/2023] Open
Abstract
Pathogenic heterozygous variants in SGMS2 cause a rare monogenic form of osteoporosis known as calvarial doughnut lesions with bone fragility (CDL). The clinical presentations of SGMS2-related bone pathology range from childhood-onset osteoporosis with low bone mineral density and sclerotic doughnut-shaped lesions in the skull to a severe spondylometaphyseal dysplasia with neonatal fractures, long-bone deformities, and short stature. In addition, neurological manifestations occur in some patients. SGMS2 encodes sphingomyelin synthase 2 (SMS2), an enzyme involved in the production of sphingomyelin (SM). This review describes the biochemical structure of SM, SM metabolism, and their molecular actions in skeletal and neural tissue. We postulate how disrupted SM gradient can influence bone formation and how animal models may facilitate a better understanding of SGMS2-related osteoporosis.
Collapse
Affiliation(s)
- Sandra Pihlström
- Folkhälsan Institute of Genetics, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Sampo Richardt
- Folkhälsan Institute of Genetics, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Kirsi Määttä
- Folkhälsan Institute of Genetics, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Minna Pekkinen
- Folkhälsan Institute of Genetics, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Children´s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
| | - Vesa M. Olkkonen
- Minerva Foundation Institute for Medical Research, Helsinki, Finland
- Department of Anatomy, Faculty of Medicine, University of Helsinki, Helsinki, Finland
| | - Outi Mäkitie
- Folkhälsan Institute of Genetics, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Children´s Hospital, University of Helsinki and Helsinki University Hospital, Helsinki, Finland
- Department of Molecular Medicine and Surgery and Center for Molecular Medicine, Karolinska Institutet, Stockholm, Sweden
| | - Riikka E. Mäkitie
- Folkhälsan Institute of Genetics, Helsinki, Finland
- Research Program for Clinical and Molecular Metabolism, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Department of Otorhinolaryngology – Head and Neck Surgery, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
| |
Collapse
|
2
|
Wang D, Zhao Z, Long Y, Fan R. Protein Kinase C Is Involved in Vegetative Development, Stress Response and Pathogenicity in Verticillium dahliae. Int J Mol Sci 2023; 24:14266. [PMID: 37762573 PMCID: PMC10531995 DOI: 10.3390/ijms241814266] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Revised: 08/30/2023] [Accepted: 09/04/2023] [Indexed: 09/29/2023] Open
Abstract
Potato Verticillium wilt, caused by Verticillium dahliae, is a serious soil-borne vascular disease, which restricts the sustainable development of the potato industry, and the pathogenic mechanism of the fungus is complex. Therefore, it is of great significance to explore the important pathogenic factors of V. dahliae to expand the understanding of its pathology. Protein kinase C (PKC) gene is located in the Ca2+ signaling pathway, which is highly conserved in filamentous fungi and involved in the regulation of a variety of biological processes. In the current study, the PKC gene in V. dahliae (VdPKC) was characterized, and its effects on the fungal pathogenicity and tolerance to fungicide stress were further studied. The results showed that the VdPKC positively regulated the growth and development, conidial germination, and production of V. dahliae, which was necessary for the fungus to achieve pathogenicity. It also affected the formation of melanin and microsclerotia and changed the adaptability of V. dahliae to different environmental stresses. In addition, VdPKC altered the tolerance of V. dahliae to different fungicides, which may be a potential target for polyoxin. Therefore, our results strongly suggest that VdPKC gene is necessary for the vegetative growth, stress response, and pathogenicity of V. dahliae.
Collapse
Affiliation(s)
| | | | | | - Rong Fan
- College of Agriculture, Guizhou University, Guiyang 550025, China; (D.W.); (Z.Z.); (Y.L.)
| |
Collapse
|
3
|
Insertion Depth Modulates Protein Kinase C-δ-C1b Domain Interactions with Membrane Cholesterol as Revealed by MD Simulations. Int J Mol Sci 2023; 24:ijms24054598. [PMID: 36902029 PMCID: PMC10002858 DOI: 10.3390/ijms24054598] [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: 01/12/2023] [Revised: 02/22/2023] [Accepted: 02/23/2023] [Indexed: 03/02/2023] Open
Abstract
Protein kinase C delta (PKC-δ) is an important signaling molecule in human cells that has both proapoptotic as well as antiapoptotic functions. These conflicting activities can be modulated by two classes of ligands, phorbol esters and bryostatins. Phorbol esters are known tumor promoters, while bryostatins have anti-cancer properties. This is despite both ligands binding to the C1b domain of PKC-δ (δC1b) with a similar affinity. The molecular mechanism behind this discrepancy in cellular effects remains unknown. Here, we have used molecular dynamics simulations to investigate the structure and intermolecular interactions of these ligands bound to δC1b with heterogeneous membranes. We observed clear interactions between the δC1b-phorbol complex and membrane cholesterol, primarily through the backbone amide of L250 and through the K256 side-chain amine. In contrast, the δC1b-bryostatin complex did not exhibit interactions with cholesterol. Topological maps of the membrane insertion depth of the δC1b-ligand complexes suggest that insertion depth can modulate δC1b interactions with cholesterol. The lack of cholesterol interactions suggests that bryostatin-bound δC1b may not readily translocate to cholesterol-rich domains within the plasma membrane, which could significantly alter the substrate specificity of PKC-δ compared to δC1b-phorbol complexes.
Collapse
|
4
|
Protein kinase C showcases allosteric control: activation of LRRK1. Biochem J 2023; 480:219-223. [PMID: 36762701 PMCID: PMC9987930 DOI: 10.1042/bcj20220507] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2022] [Revised: 01/05/2023] [Accepted: 01/05/2023] [Indexed: 02/11/2023]
Abstract
Allosteric regulation of multi-domain protein kinases provides a common mechanism to acutely control kinase activity. Protein kinase C serves as a paradigm for multi-domain proteins whose activity is exquisitely tuned by interdomain conformational changes that keep the enzyme off in the absence of appropriate stimuli, but unleash activity in response to second messenger binding. Allosteric regulation of protein kinase C signaling has been optimized not just for itself: Alessi and colleagues discover that protein kinase C phosphorylates LRRK1, a kinase with even more domains, at sites on its CORB GTPase domain to allosterically activate LRRK1.
Collapse
|
5
|
Barneda D, Janardan V, Niewczas I, Collins DM, Cosulich S, Clark J, Stephens LR, Hawkins PT. Acyl chain selection couples the consumption and synthesis of phosphoinositides. EMBO J 2022; 41:e110038. [PMID: 35771169 PMCID: PMC9475507 DOI: 10.15252/embj.2021110038] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2022] [Revised: 05/11/2022] [Accepted: 05/12/2022] [Indexed: 12/12/2022] Open
Abstract
Phosphoinositides (PIPn) in mammalian tissues are enriched in the stearoyl/arachidonoyl acyl chain species ("C38:4"), but its functional significance is unclear. We have used metabolic tracers (isotopologues of inositol, glucose and water) to study PIPn synthesis in cell lines in which this enrichment is preserved to differing relative extents. We show that PIs synthesised from glucose are initially enriched in shorter/more saturated acyl chains, but then rapidly remodelled towards the C38:4 species. PIs are also synthesised by a distinct 're-cycling pathway', which utilises existing precursors and exhibits substantial selectivity for the synthesis of C38:4-PA and -PI. This re-cycling pathway is rapidly stimulated during receptor activation of phospholipase-C, both allowing the retention of the C38:4 backbone and the close coupling of PIPn consumption to its resynthesis, thus maintaining pool sizes. These results suggest that one property of the specific acyl chain composition of PIPn is that of a molecular code, to facilitate 'metabolic channelling' from PIP2 to PI via pools of intermediates (DG, PA and CDP-DG) common to other lipid metabolic pathways.
Collapse
Affiliation(s)
- David Barneda
- Signalling Programme, Babraham Institute, Cambridge, UK.,Projects, Oncology R&D, AstraZeneca, Cambridge, UK
| | - Vishnu Janardan
- Cellular Organization and Signalling, National Centre for Biological Sciences, Bangalore, India
| | | | | | | | | | | | | |
Collapse
|
6
|
Yanagita RC, Otani M, Hatanaka S, Nishi H, Miyake S, Hanaki Y, Sato M, Kawanami Y, Irie K. Analysis of binding mode of vibsanin A with protein kinase C C1 domains: An experimental and molecular dynamics simulation study. J Mol Struct 2022. [DOI: 10.1016/j.molstruc.2022.132866] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
|
7
|
LPIN1 Induces Gefitinib Resistance in EGFR Inhibitor-Resistant Non-Small Cell Lung Cancer Cells. Cancers (Basel) 2022; 14:cancers14092222. [PMID: 35565351 PMCID: PMC9102170 DOI: 10.3390/cancers14092222] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/29/2022] [Revised: 04/24/2022] [Accepted: 04/27/2022] [Indexed: 12/04/2022] Open
Abstract
Drug resistance limits the efficacy of targeted therapies, including tyrosine kinase inhibitors (TKIs); however, a substantial portion of the drug resistance mechanisms remains unexplained. In this study, we identified LPIN1 as a key factor that regulates gefitinib resistance in epidermal growth factor receptor (EGFR)-mutant non-small cell lung cancer (NSCLC) cells. Unlike TKI-sensitive HCC827 cells, gefitinib treatment induced LPIN1 expression and increased diacylglycerol concentration in TKI-resistant H1650 cells, followed by the activation of protein kinase C delta and nuclear factor kappa B (NF-κB) in an LPIN1-dependent manner, resulting in cancer cell survival. Additionally, LPIN1 increased the production of lipid droplets, which play an important role in TKI drug resistance. All results were recapitulated in a patient-derived EGFR-mutant NSCLC cell line. In in vivo tumorigenesis assay, we identified that both shRNA-mediated depletion and pharmaceutical inhibition of LPIN1 clearly reduced tumor growth and confirmed that gefitinib treatment induced LPIN1 expression and LPIN1-dependent NF-κB activation (an increase in p-IκBα level) in tumor tissues. These results suggest an effective strategy of co-treating TKIs and LPIN1 inhibitors to prevent TKI resistance in NSCLC patients.
Collapse
|
8
|
OUP accepted manuscript. Hum Mol Genet 2022; 31:2236-2261. [DOI: 10.1093/hmg/ddac029] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2021] [Revised: 01/22/2022] [Accepted: 01/24/2022] [Indexed: 11/12/2022] Open
|
9
|
Renkhold L, Kollmann R, Inderwiedenstraße L, Kienitz MC. PKC-isoform specific regulation of receptor desensitization and KCNQ1/KCNE1 K + channel activity by mutant α 1B-adrenergic receptors. Cell Signal 2021; 91:110228. [PMID: 34958868 DOI: 10.1016/j.cellsig.2021.110228] [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: 10/25/2021] [Revised: 12/20/2021] [Accepted: 12/21/2021] [Indexed: 11/25/2022]
Abstract
Activation of a specific protein kinase C (PKC) isoform during stimulation of Gq protein-coupled receptors (GqPCRs) is determined by homologous receptor desensitization that controls the spatiotemporal formation of downstream Gq signalling molecules. Furthermore, GqPCR-activated PKC isoforms specifically regulate receptor activity via a negative feedback mechanism. In the present study, we investigated the contribution of several phosphorylation sites in the α1B-adrenergic receptor (α1B-AR) for PKC and G protein coupled receptor kinase 2 (GRK2) to homologous receptor desensitization and effector modulation. We analyzed signalling events downstream to human wildtype α1B-ARs and α1B-ARs lacking PKC or GRK2 phosphorylation sites (Δ391-401, α1B-ΔPKC-AR and Δ402-520, α1B-ΔGRK-AR) by means of FRET-based biosensors in HEK293 that served as online-assays of receptor activity. K+ currents through KCNQ1/KCNE1 channels (IKs), which are regulated by both phosphatidylinositol 4,5-bisphosphate (PIP2)-depletion and/or phosphorylation by PKC, were measured as a functional readout of wildtype and mutant α1B-AR receptor activity. As a novel finding, we provide evidence that deletion of PKC and GRK2 phosphorylation sites in α1B-ARs abrogates the contribution of PKCα to homologous receptor desensitization. Instead, the time course of mutant receptor activity was specifically modulated by PKCβ. Mutant α1B-ARs displayed pronounced homologous receptor desensitization that was abolished by PKCβ-specific pharmacological inhibitors. IKs modulation during stimulation of wildtype and mutant α1B-ARs displayed transient inhibition and current facilitation after agonist withdrawal with reduced capability of mutant α1B-ARs to induce IKs inhibition. Pharmacological inhibition of the PKCβ isoform did not augment IKs reduction by mutant α1B-ARs, but shifted IKs modulation towards current facilitation. Coexpression of an inactive (dominant-negative) PKCδ isoform (DN-PKCδ) abolished IKs facilitation in α1B-ΔGRK-AR-expressing cells, but not in α1B-ΔPKC-AR-expressing cells. The data indicate that the differential modulation of IKs activity by α1B-ΔGRK- and α1B-ΔPKC-receptors is attributed to the activation of entirely distinct novel PKC isoforms. To summarize, specific phosphorylation sites within the wildtype and mutant α1B-adrenergic receptors are targeted by different PKC isoforms, resulting in differential regulation of receptor desensitization and effector function.
Collapse
Affiliation(s)
- Lina Renkhold
- Klinik für Hautkrankheiten, Universitätsklinikum Münster, Von-Esmarch-Str. 58, D-48149 Münster, Deutschland, Germany
| | - Rike Kollmann
- Department of Cellular Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
| | - Leonie Inderwiedenstraße
- Department of Cellular Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany
| | - Marie-Cecile Kienitz
- Department of Cellular Physiology, Institute of Physiology, Ruhr University Bochum, Universitätsstrasse 150, D-44801 Bochum, Germany.
| |
Collapse
|
10
|
Stress granules safeguard against MAPK signaling hyperactivation by sequestering PKC/Pck2: new findings and perspectives. Curr Genet 2021; 67:857-863. [PMID: 34100129 DOI: 10.1007/s00294-021-01192-1] [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: 02/19/2021] [Revised: 05/08/2021] [Accepted: 05/15/2021] [Indexed: 01/28/2023]
Abstract
Stress granule (SG) assembly is a conserved cellular strategy that copes with stress-related damage and promotes cell survival. SGs form through a process of liquid-liquid phase separation. Cellular signaling also appears to employ SG assembly as a mechanism for controlling cell survival and cell death by spatial compartmentalization of signal-transducing factors. While several lines of evidence highlight the importance of SGs as signaling hubs, where protein components of signaling pathways can be temporarily sequestered, shielded from the cytoplasm, the regulation and physiological significance of SGs in this aspect remain largely obscure. A recent study of the heat-shock response in the fission yeast Schizosaaccharomyces pombe provides an unexpected answer to this question. Recently, we demonstrated that the PKC orthologue Pck2 in fission yeast translocates into SGs through phase separation in a PKC kinase activity-dependent manner upon high-heat stress (HHS). Importantly, the downstream MAPK Pmk1 promotes Pck2 recruitment into SGs, which intercepts MAPK hyperactivation and cell death, thus posing SGs as a negative feedback circuit in controlling MAPK signaling. Intriguingly, HHS, but not modest-heat stress targets Pck2 to SGs, independent of canonical SG machinery. Finally, cells fail to activate MAPK signaling when Pck2 is sequestrated into SGs. In this review, we will discuss how SGs have a role as signaling hubs beyond serving as a repository for non-translated mRNAs during acute stress.
Collapse
|
11
|
Protein kinase C-mediated calcium signaling as the basis for cardiomyocyte plasticity. Arch Biochem Biophys 2021; 701:108817. [PMID: 33626379 DOI: 10.1016/j.abb.2021.108817] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 02/03/2021] [Accepted: 02/14/2021] [Indexed: 01/08/2023]
Abstract
Protein kinase C is the superfamily of intracellular effector molecules which control crucial cellular functions. Here, we for the first time did the percentage estimation of all known PKC and PKC-related isozymes at the individual cadiomyocyte level. Broad spectrum of PKC transcripts is expressed in the left ventricular myocytes. In addition to the well-known 'heart-specific' PKCα, cardiomyocytes have the high expression levels of PKCN1, PKCδ, PKCD2, PKCε. In general, we detected all PKC isoforms excluding PKCη. In cardiomyocytes PKC activity tonically regulates voltage-gated Ca2+-currents, intracellular Ca2+ level and nitric oxide (NO) production. Imidazoline receptor of the first type (I1R)-mediated induction of the PKC activity positively modulates Ca2+ release through ryanodine receptor (RyR), increasing the Ca2+ leakage in the cytosol. In cardiomyocytes with the Ca2+-overloaded regions of > 9-10 μm size, the local PKC-induced Ca2+ signaling is transformed to global accompanied by spontaneous Ca2+ waves propagation across the entire cell perimeter. Such switching of Ca2+ signaling in cardiac cells can be important for the development of several cardiovascular pathologies and/or myocardial plasticity at the cardiomyocyte level.
Collapse
|
12
|
Katti S, Igumenova TI. Structural insights into C1-ligand interactions: Filling the gaps by in silico methods. Adv Biol Regul 2021; 79:100784. [PMID: 33526356 DOI: 10.1016/j.jbior.2020.100784] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2020] [Revised: 12/24/2020] [Accepted: 12/28/2020] [Indexed: 02/05/2023]
Abstract
Protein Kinase C isoenzymes (PKCs) are the key mediators of the phosphoinositide signaling pathway, which involves regulated hydrolysis of phosphatidylinositol (4,5)-bisphosphate to diacylglycerol (DAG) and inositol-1,4,5-trisphosphate. Dysregulation of PKCs is implicated in many human diseases making this class of enzymes an important therapeutic target. Specifically, the DAG-sensing cysteine-rich conserved homology-1 (C1) domains of PKCs have emerged as promising targets for pharmaceutical modulation. Despite significant progress, the rational design of the C1 modulators remains challenging due to difficulties associated with structure determination of the C1-ligand complexes. Given the dearth of experimental structural data, computationally derived models have been instrumental in providing atomistic insight into the interactions of the C1 domains with PKC agonists. In this review, we provide an overview of the in silico approaches for seven classes of C1 modulators and outline promising future directions.
Collapse
Affiliation(s)
- Sachin Katti
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, TX, 77843, United States
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University, 300 Olsen Boulevard, College Station, TX, 77843, United States.
| |
Collapse
|
13
|
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.
Collapse
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
| |
Collapse
|
14
|
Katsuno-Kambe H, Parton RG, Yap AS, Teo JL. Caveolin-1 influences epithelial collective cell migration via FMNL2 formin. Biol Cell 2020; 113:107-117. [PMID: 33169848 DOI: 10.1111/boc.202000116] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2020] [Accepted: 11/03/2020] [Indexed: 02/02/2023]
Abstract
BACKGROUND INFORMATION Epithelial collective cell migration requires the intrinsic locomotor activity of cells to be coordinated across populations. This coordination is governed by the presence of cell-cell adhesions as well as the cooperative behaviour of cells within the monolayer. RESULTS Here, we report a role for Caveolin-1 (CAV1) in epithelial collective cell migration. CAV1 depletion reduced the migratory behaviour of AML12 liver epithelial cells when grown as monolayers, but not as individual cells. This suggested that CAV1 is a component of the process by which multicellular collectivity regulates epithelial motility. The correlation length for migration velocity was increased by CAV1 RNAi, a possible sign of epithelial jamming. However, CAV1 RNAi reduced migration, even when monolayers were allowed to migrate into unconfined spaces. The migratory defect was ameliorated by simultaneous depletion of the FMNL2 formin, whose cortical recruitment is increased in CAV1 RNAi cells. CONCLUSIONS We therefore suggest that CAV1 modulates intraepithelial motility by controlling the cortical availability of FMNL2. SIGNIFICANCE Although epithelial collective cell migration has been observed in multiple contexts both in vivo and in vitro, the inherent coupling and coordination of activity between cells within the monolayer remain incompletely understood. Our study highlights a role for CAV1 in regulating intraepithelial motility, an effect that involves the formin FMNL2.
Collapse
Affiliation(s)
- Hiroko Katsuno-Kambe
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, 4072, Australia
| | - Robert G Parton
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, 4072, Australia.,Centre for Microscopy and Microanalysis, The University of Queensland, St. Lucia, 4072, Australia
| | - Alpha S Yap
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, 4072, Australia
| | - Jessica L Teo
- Division of Cell and Developmental Biology, Institute for Molecular Bioscience, The University of Queensland, St. Lucia, 4072, Australia
| |
Collapse
|
15
|
Schmitz-Peiffer C. Deconstructing the Role of PKC Epsilon in Glucose Homeostasis. Trends Endocrinol Metab 2020; 31:344-356. [PMID: 32305097 DOI: 10.1016/j.tem.2020.01.016] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/24/2019] [Revised: 01/22/2020] [Accepted: 01/24/2020] [Indexed: 02/06/2023]
Abstract
The failure of insulin to suppress glucose production by the liver is a key aspect of the insulin resistance seen in type 2 diabetes. Lipid-activated protein kinase C epsilon has long been identified as an important mediator of diet-induced glucose intolerance and hepatic insulin resistance and the current view emphasizes a mechanism involving phosphorylation of the insulin receptor by the kinase to inhibit downstream insulin action. However, the significance of this direct effect in the liver has now been challenged by tissue-specific deletion of PKCε, which demonstrated a more prominent role for the kinase in adipose tissue to promote glucose intolerance. New insights regarding the role of PKCε therefore contribute to the understanding of indirect effects on hepatic glucose metabolism.
Collapse
Affiliation(s)
- Carsten Schmitz-Peiffer
- Garvan Institute of Medical Research, Darlinghurst Sydney, NSW 2010, Australia; St Vincent's Clinical School, University of New South Wales, Sydney, NSW 2010, Australia.
| |
Collapse
|
16
|
How is the acyl chain composition of phosphoinositides created and does it matter? Biochem Soc Trans 2020; 47:1291-1305. [PMID: 31657437 PMCID: PMC6824679 DOI: 10.1042/bst20190205] [Citation(s) in RCA: 33] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2019] [Revised: 09/27/2019] [Accepted: 10/01/2019] [Indexed: 12/11/2022]
Abstract
The phosphoinositide (PIPn) family of signalling phospholipids are central regulators in membrane cell biology. Their varied functions are based on the phosphorylation pattern of their inositol ring, which can be recognized by selective binding domains in their effector proteins and be modified by a series of specific PIPn kinases and phosphatases, which control their interconversion in a spatial and temporal manner. Yet, a unique feature of PIPns remains largely unexplored: their unusually uniform acyl chain composition. Indeed, while most phospholipids present a range of molecular species comprising acyl chains of diverse length and saturation, PIPns in several organisms and tissues show the predominance of a single hydrophobic backbone, which in mammals is composed of arachidonoyl and stearoyl chains. Despite evolution having favoured this specific PIPn configuration, little is known regarding the mechanisms and functions behind it. In this review, we explore the metabolic pathways that could control the acyl chain composition of PIPns as well as the potential roles of this selective enrichment. While our understanding of this phenomenon has been constrained largely by the technical limitations in the methods traditionally employed in the PIPn field, we believe that the latest developments in PIPn analysis should shed light onto this old question.
Collapse
|
17
|
Pemberton JG, Kim YJ, Balla T. Integrated regulation of the phosphatidylinositol cycle and phosphoinositide-driven lipid transport at ER-PM contact sites. Traffic 2019; 21:200-219. [PMID: 31650663 DOI: 10.1111/tra.12709] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2019] [Revised: 10/02/2019] [Accepted: 10/16/2019] [Indexed: 12/20/2022]
Abstract
Among the structural phospholipids that form the bulk of eukaryotic cell membranes, phosphatidylinositol (PtdIns) is unique in that it also serves as the common precursor for low-abundance regulatory lipids, collectively referred to as polyphosphoinositides (PPIn). The metabolic turnover of PPIn species has received immense attention because of the essential functions of these lipids as universal regulators of membrane biology and their dysregulation in numerous human pathologies. The diverse functions of PPIn lipids occur, in part, by orchestrating the spatial organization and conformational dynamics of peripheral or integral membrane proteins within defined subcellular compartments. The emerging role of stable contact sites between adjacent membranes as specialized platforms for the coordinate control of ion exchange, cytoskeletal dynamics, and lipid transport has also revealed important new roles for PPIn species. In this review, we highlight the importance of membrane contact sites formed between the endoplasmic reticulum (ER) and plasma membrane (PM) for the integrated regulation of PPIn metabolism within the PM. Special emphasis will be placed on non-vesicular lipid transport during control of the PtdIns biosynthetic cycle as well as toward balancing the turnover of the signaling PPIn species that define PM identity.
Collapse
Affiliation(s)
- Joshua G Pemberton
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, Maryland
| | - Yeun Ju Kim
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, Maryland
| | - Tamas Balla
- Section on Molecular Signal Transduction, Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), National Institutes of Health, Bethesda, Maryland
| |
Collapse
|
18
|
Niemeyer A, Rinne A, Kienitz MC. Receptor-specific regulation of atrial GIRK channel activity by different Ca2+-dependent PKC isoforms. Cell Signal 2019; 64:109418. [DOI: 10.1016/j.cellsig.2019.109418] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2019] [Revised: 09/11/2019] [Accepted: 09/11/2019] [Indexed: 12/23/2022]
|
19
|
A real-time, click chemistry imaging approach reveals stimulus-specific subcellular locations of phospholipase D activity. Proc Natl Acad Sci U S A 2019; 116:15453-15462. [PMID: 31311871 DOI: 10.1073/pnas.1903949116] [Citation(s) in RCA: 42] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The fidelity of signal transduction requires spatiotemporal control of the production of signaling agents. Phosphatidic acid (PA) is a pleiotropic lipid second messenger whose modes of action differ based on upstream stimulus, biosynthetic source, and site of production. How cells regulate the local production of PA to effect diverse signaling outcomes remains elusive. Unlike other second messengers, sites of PA biosynthesis cannot be accurately visualized with subcellular precision. Here, we describe a rapid, chemoenzymatic approach for imaging physiological PA production by phospholipase D (PLD) enzymes. Our method capitalizes on the remarkable discovery that bulky, hydrophilic trans-cyclooctene-containing primary alcohols can supplant water as the nucleophile in the PLD active site in a transphosphatidylation reaction of PLD's lipid substrate, phosphatidylcholine. The resultant trans-cyclooctene-containing lipids are tagged with a fluorogenic tetrazine reagent via a no-rinse, inverse electron-demand Diels-Alder (IEDDA) reaction, enabling their immediate visualization by confocal microscopy in real time. Strikingly, the fluorescent reporter lipids initially produced at the plasma membrane (PM) induced by phorbol ester stimulation of PLD were rapidly internalized via apparent nonvesicular pathways rather than endocytosis, suggesting applications of this activity-based imaging toolset for probing mechanisms of intracellular phospholipid transport. By instead focusing on the initial 10 s of the IEDDA reaction, we precisely pinpointed the subcellular locations of endogenous PLD activity as elicited by physiological agonists of G protein-coupled receptor and receptor tyrosine kinase signaling. These tools hold promise to shed light on both lipid trafficking pathways and physiological and pathological effects of localized PLD signaling.
Collapse
|
20
|
Herranz G, Aguilera P, Dávila S, Sánchez A, Stancu B, Gómez J, Fernández-Moreno D, de Martín R, Quintanilla M, Fernández T, Rodríguez-Silvestre P, Márquez-Expósito L, Bello-Gamboa A, Fraile-Ramos A, Calvo V, Izquierdo M. Protein Kinase C δ Regulates the Depletion of Actin at the Immunological Synapse Required for Polarized Exosome Secretion by T Cells. Front Immunol 2019; 10:851. [PMID: 31105694 PMCID: PMC6499072 DOI: 10.3389/fimmu.2019.00851] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2018] [Accepted: 04/02/2019] [Indexed: 12/02/2022] Open
Abstract
Multivesicular bodies (MVB) are endocytic compartments that enclose intraluminal vesicles (ILVs) formed by inward budding from the limiting membrane of endosomes. In T lymphocytes, ILVs are secreted as Fas ligand-bearing, pro-apoptotic exosomes following T cell receptor (TCR)-induced fusion of MVB with the plasma membrane at the immune synapse (IS). In this study we show that protein kinase C δ (PKCδ), a novel PKC isotype activated by diacylglycerol (DAG), regulates TCR-controlled MVB polarization toward the IS and exosome secretion. Concomitantly, we demonstrate that PKCδ-interfered T lymphocytes are defective in activation-induced cell death. Using a DAG sensor based on the C1 DAG-binding domain of PKCδ and a GFP-PKCδ chimera, we reveal that T lymphocyte activation enhances DAG levels at the MVB endomembranes which mediates the association of PKCδ to MVB. Spatiotemporal reorganization of F-actin at the IS is inhibited in PKCδ-interfered T lymphocytes. Therefore, we propose PKCδ as a DAG effector that regulates the actin reorganization necessary for MVB traffic and exosome secretion.
Collapse
Affiliation(s)
- Gonzalo Herranz
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Pablo Aguilera
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Sergio Dávila
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Alicia Sánchez
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Bianca Stancu
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Jesús Gómez
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - David Fernández-Moreno
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Raúl de Martín
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Mario Quintanilla
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Teresa Fernández
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Pablo Rodríguez-Silvestre
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Laura Márquez-Expósito
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Ana Bello-Gamboa
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Alberto Fraile-Ramos
- Departamento de Biología Celular, Facultad de Medicina, Universidad Complutense de Madrid, Madrid, Spain
| | - Víctor Calvo
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| | - Manuel Izquierdo
- Departamento de Bioquímica, Instituto de Investigaciones Biomédicas Alberto Sols CSIC-UAM, Madrid, Spain
| |
Collapse
|
21
|
Jama A, Huang D, Alshudukhi AA, Chrast R, Ren H. Lipin1 is required for skeletal muscle development by regulating MEF2c and MyoD expression. J Physiol 2018; 597:889-901. [PMID: 30511745 DOI: 10.1113/jp276919] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 12/03/2018] [Indexed: 12/19/2022] Open
Abstract
KEY POINTS Lipin1 is critical for skeletal muscle development. Lipin1 regulates MyoD and myocyte-specific enhancer factor 2C (MEF2c) expression via the protein kinase C (PKC)/histone deacetylase 5-mediated pathway. Inhibition of PKCμ activity suppresses myoblast differentiation by inhibiting MyoD and MEF2c expression. ABSTRACT Our previous characterization of global lipin1-deficient (fld) mice demonstrated that lipin1 played a novel role in skeletal muscle (SM) regeneration. The present study using cell type-specific Myf5-cre;Lipin1fl/fl conditional knockout mice (Lipin1Myf5cKO ) shows that lipin1 is a major determinant of SM development. Lipin1 deficiency induced reduced muscle mass and myopathy. Our results from lipin1-deficient myoblasts suggested that lipin1 regulates myoblast differentiation via the protein kinase Cμ (PKCμ)/histone deacetylase 5 (HDAC5)/myocyte-specific enhancer factor 2C (MEF2c):MyoD-mediated pathway. Lipin1 deficiency leads to the suppression of PKC isoform activities, as well as inhibition of the downstream target of PKCμ, class II deacetylase HDAC5 nuclear export, and, consequently, inhibition of MEF2c and MyoD expression in the SM of lipin1Myf5cKO mice. Restoration of diacylglycerol-mediated signalling in lipin1 deficient myoblasts by phorbol 12-myristate 13-acetate transiently activated PKC and HDAC5, and upregulated MEF2c expression. Our findings provide insights into the signalling circuitry that regulates SM development, and have important implications for developing intervention aimed at treating muscular dystrophy.
Collapse
Affiliation(s)
- Abdulrahman Jama
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, OH, USA
| | - Dengtong Huang
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, OH, USA
| | - Abdullah A Alshudukhi
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, OH, USA
| | - Roman Chrast
- Department of Neuroscience and Department of Clinical Neuroscience, Karolinska Institutet, Stockholm, Sweden
| | - Hongmei Ren
- Department of Biochemistry and Molecular Biology, Wright State University, Dayton, OH, USA
| |
Collapse
|
22
|
Jackson-Hayes L, Atiq Z, Betton B, Freyaldenhoven WT, Myers L, Olsen E, Hill TW. Aspergillus nidulans protein kinase C forms a complex with the formin SepA that is involved in apical growth and septation. Fungal Genet Biol 2018; 122:21-30. [PMID: 30391723 DOI: 10.1016/j.fgb.2018.10.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/16/2017] [Revised: 10/22/2018] [Accepted: 10/23/2018] [Indexed: 10/27/2022]
Abstract
The Aspergillus nidulans orthologue of Protein kinase C (PkcA) and the A. nidulans formin SepA participate in polarized growth. PkcA localizes to growing hyphal apices and septation sites, and amino acid sequences within PkcA that are required for PkcA to localize to these sites of cell wall synthesis have been identified. SepA is associated with the contractile actomyosin ring (CAR), and it localizes at hyphal tips in association with the Spitzenkörper (SPK) and as an apical dome. A mutation in the sepA gene (sepA1) renders A. nidulans aseptate at elevated temperature. Progress towards understanding the spatiotemporal relationship between PkcA and SepA during polarized growth is presented here. Fluorescent chimeras of PkcA and SepA strongly overlapped in some hyphal tips in a dome pattern, while other tips displayed SepA SPK and PkcA dome localization within the same tip. At septation sites PkcA and SepA consistently colocalized through late stages of CAR constriction. Bimolecular fluorescence complementation experimental results provide evidence that SepA and PkcA are both present in complexes at both hyphal tip domes and at cortical rings. A Gal4-based yeast two-hybrid analysis confirmed the physical interaction between SepA and PkcA, and indicted that the FH2 domain of SepA is involved in its physical interaction with PkcA. A functional interaction between PkcA and SepA was shown through complementation of the pkcA calC2 mutant's hypersensitivity to cell wall perturbing agents by overexpressed sepA and by the ability of the sepA1 mutation to block PkcA's ability to form cortical rings. Taken together these results suggest that a PkcA/SepA complex is involved in polarized growth. Through experiments using the actin disrupter latrunculin B, evidence is presented suggesting that actin plays a role in the PkcA/SepA complex.
Collapse
Affiliation(s)
- Loretta Jackson-Hayes
- Department of Chemistry, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA; Biochemistry and Molecular Biology Program, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA.
| | - Zainab Atiq
- Biochemistry and Molecular Biology Program, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA
| | - Brianna Betton
- Biochemistry and Molecular Biology Program, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA
| | - W Toler Freyaldenhoven
- Biochemistry and Molecular Biology Program, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA
| | - Lance Myers
- Biochemistry and Molecular Biology Program, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA
| | - Elisabet Olsen
- Department of Chemistry, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA
| | - Terry W Hill
- Biochemistry and Molecular Biology Program, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA; Department of Biology, Rhodes College, 2000 N. Parkway, Memphis, TN 38112, USA
| |
Collapse
|
23
|
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.
Collapse
|
24
|
Cummins TJ, Kedei N, Czikora A, Lewin NE, Kirk S, Petersen ME, McGowan KM, Chen JQ, Luo X, Johnson RC, Ravichandran S, Blumberg PM, Keck GE. Synthesis and Biological Evaluation of Fluorescent Bryostatin Analogues. Chembiochem 2018; 19:877-889. [PMID: 29424951 DOI: 10.1002/cbic.201700655] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Indexed: 11/10/2022]
Abstract
To investigate the cellular distribution of tumor-promoting vs. non-tumor-promoting bryostatin analogues, we synthesized fluorescently labeled variants of two bryostatin derivatives that have previously shown either phorbol ester-like or bryostatin-like biological activity in U937 leukemia cells. These new fluorescent analogues both displayed high affinity for protein kinase C (PKC) binding and retained the basic properties of the parent unlabeled compounds in U937 assays. The fluorescent compounds showed similar patterns of intracellular distribution in cells, however; this argues against an existing hypothesis that various patterns of intracellular distribution are responsible for differences in biological activity. Upon further characterization, the fluorescent compounds revealed a slow rate of cellular uptake; correspondingly, they showed reduced activity for cellular responses that were only transient upon treatment with phorbol ester or bryostatin 1.
Collapse
Affiliation(s)
- Thomas J Cummins
- University of Utah, Department of Chemistry, 315 South 1400 East, Room 2020, Salt Lake City, UT, 84112, USA
| | - Noemi Kedei
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Room 4048, Bethesda, MD, 20892, USA
| | - Agnes Czikora
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Room 4048, Bethesda, MD, 20892, USA
| | - Nancy E Lewin
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Room 4048, Bethesda, MD, 20892, USA
| | - Sharon Kirk
- University of Utah, Department of Chemistry, 315 South 1400 East, Room 2020, Salt Lake City, UT, 84112, USA
| | - Mark E Petersen
- University of Utah, Department of Chemistry, 315 South 1400 East, Room 2020, Salt Lake City, UT, 84112, USA
| | - Kevin M McGowan
- University of Utah, Department of Chemistry, 315 South 1400 East, Room 2020, Salt Lake City, UT, 84112, USA
| | - Jin-Qiu Chen
- Collaborative Protein Technology Resource, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Room 1044, Bethesda, MD, 20892, USA
| | - Xiaoling Luo
- Collaborative Protein Technology Resource, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Room 1044, Bethesda, MD, 20892, USA
| | - Randall C Johnson
- Advanced Biomedical and Computational Sciences Biomedical Informatics, and Data Science (BIDS), Directorate Frederick National Laboratory for Cancer Research (FNLCR), Leidos Biomedical Research, Inc., Building 430, Miller Drive, Fort Detrick, Frederick, MD, 21702, USA
| | - Sarangan Ravichandran
- Advanced Biomedical and Computational Sciences Biomedical Informatics, and Data Science (BIDS), Directorate Frederick National Laboratory for Cancer Research (FNLCR), Leidos Biomedical Research, Inc., Building 430, Miller Drive, Fort Detrick, Frederick, MD, 21702, USA
| | - Peter M Blumberg
- Laboratory of Cancer Biology and Genetics, Center for Cancer Research, National Cancer Institute, 37 Convent Drive, Room 4048, Bethesda, MD, 20892, USA
| | - Gary E Keck
- University of Utah, Department of Chemistry, 315 South 1400 East, Room 2020, Salt Lake City, UT, 84112, USA
| |
Collapse
|
25
|
Spassieva S, Bieberich E. Lysosphingolipids and sphingolipidoses: Psychosine in Krabbe's disease. J Neurosci Res 2017; 94:974-81. [PMID: 27638582 DOI: 10.1002/jnr.23888] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2016] [Revised: 07/24/2016] [Accepted: 07/25/2016] [Indexed: 12/14/2022]
Abstract
Until recently, lipids were considered inert building blocks of cellular membranes. This changed three decades ago when lipids were found to regulate cell polarity and vesicle transport, and the "lipid raft" concept took shape. The lipid-driven membrane anisotropy in form of "rafts" that associate with proteins led to the view that organized complexes of lipids and proteins regulate various cell functions. Disturbance of this organization can lead to cellular, tissue, and organ malfunction. Sphingolipidoses, lysosomal storage diseases that are caused by enzyme deficiencies in the sphingolipid degradation pathway, were found to be particularly detrimental to the brain. These enzyme deficiencies result in accumulation of sphingolipid metabolites in lysosomes, although it is not yet clear how this accumulation affects the organization of lipids in cellular membranes. Krabbe's disease (KD), or globoid cell leukodystrophy, was one of the first sphingolipidosis for which the raft concept offered a potential mechanism. KD is caused by mutations in the enzyme β-galactocerebrosidase; however, elevation of its substrate, galactosylceramide, is not observed or considered detrimental. Instead, it was found that a byproduct of galactosylceramide metabolism, the lysosphingolipid psychosine, is accumulated. The "psychosine hypothesis" has been refined by showing that psychosine disrupts lipid rafts and vesicular transport critical for the function of glia and neurons. The role of psychosine in KD is an example of how the disruption of sphingolipid metabolism can lead to elevation of a toxic lysosphingolipid, resulting in disruption of cellular membrane organization and neurotoxicity. © 2016 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Stefka Spassieva
- Department of Molecular and Cellular Medicine, Texas A&M Health Science Center, College Station, Texas
| | - Erhard Bieberich
- Department of Neuroscience and Regenerative Medicine, Medical College of Georgia, Augusta University, Augusta, Geogia.
| |
Collapse
|
26
|
Stewart MD, Igumenova TI. Toggling of Diacylglycerol Affinity Correlates with Conformational Plasticity in C1 Domains. Biochemistry 2017; 56:2637-2640. [PMID: 28505428 DOI: 10.1021/acs.biochem.7b00228] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Conserved homology-1 (C1) domains are peripheral membrane domains that target their host proteins to diacylglycerol (DAG)-containing membranes. It has been previously shown that a conservative aromatic mutation of a single residue in the C1 domain has a profound effect on DAG affinity. We report that the "DAG-toggling" mutation changes the conformational dynamics of the loop region that forms the binding site for the C1 activators. Moreover, there is a correlation among the residue identity at the mutation site, DAG affinity, and loop dynamics in four C1 variants. We propose that "toggling" of DAG affinity may occur through modulation of both protein-membrane interactions and the geometry of the activator-binding cleft, with the loop dynamics being responsible for the latter.
Collapse
Affiliation(s)
- Mikaela D Stewart
- Department of Biochemistry and Biophysics, Texas A&M University , College Station, Texas 77843, United States
| | - Tatyana I Igumenova
- Department of Biochemistry and Biophysics, Texas A&M University , College Station, Texas 77843, United States
| |
Collapse
|
27
|
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.
Collapse
|
28
|
Alwarawrah M, Wereszczynski J. Investigation of the Effect of Bilayer Composition on PKCα-C2 Domain Docking Using Molecular Dynamics Simulations. J Phys Chem B 2016; 121:78-88. [PMID: 27997184 DOI: 10.1021/acs.jpcb.6b10188] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The protein kinase Cα (PKCα) enzyme is a member of a broad family of serine/threonine kinases, which are involved in varied cellular signaling pathways. The initial step of PKCα activation involves the C2 subunit docking with the cell membrane, which is followed by interactions of the C1 domains with diacylglycerol (DAG) in the membrane. Notably, the molecular mechanisms of these interactions remain poorly understood, especially what effects, if any, DAG may have on the initial C2 docking. To further understand this process, we have performed a series of conventional molecular dynamics simulations to systematically investigate the interaction between PKCα-C2 domains and lipid bilayers with different compositions to examine the effects of POPS, PIP2, and 1-palmitoyl-2-oleoyl-sn-glycerol (POG) on domain docking. Our results show that the PKCα-C2 domain does not interact with the bilayer surface in the absence of POPS and PIP2. In contrast, the inclusion of POPS and PIP2 to the bilayer resulted in strong domain docking in both perpendicular and parallel orientations, whereas the further inclusion of POG resulted in only parallel domain docking. In addition, lysine residues in the C2 domain formed hydrogen bonds with PIP2 molecule bilayers containing POG. These effects were further explored with umbrella sampling calculations to estimate the free energy of domain docking to the lipid bilayer in the presence of one or two PIP2 molecules. The results show that the binding of one or two PIP2 molecules is thermodynamically favorable, although stronger in bilayers lacking POG. However, in POG-containing bilayers, the binding mode of the C2 domain appears to be more flexible, which may have implications for activation of full-length PKCα. Together, our results shed new insights into the process of C2 bilayer binding and suggest new mechanisms for the roles of different phospholipids in the activation process of PKCα.
Collapse
Affiliation(s)
- Mohammad Alwarawrah
- Department of Physics and Center for Molecular Study of Condensed Soft Matter, Illinois Institute of Technology , Chicago 60616, Illinois, United States
| | - Jeff Wereszczynski
- Department of Physics and Center for Molecular Study of Condensed Soft Matter, Illinois Institute of Technology , Chicago 60616, Illinois, United States
| |
Collapse
|
29
|
Khodorova A, Nicol GD, Strichartz G. The TrkA receptor mediates experimental thermal hyperalgesia produced by nerve growth factor: Modulation by the p75 neurotrophin receptor. Neuroscience 2016; 340:384-397. [PMID: 27826102 DOI: 10.1016/j.neuroscience.2016.10.064] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2016] [Revised: 10/24/2016] [Accepted: 10/30/2016] [Indexed: 10/20/2022]
Abstract
The p75 neurotrophin receptor (p75NTR) and its activation of the sphingomyelin signaling cascade are essential for mechanical hypersensitivity resulting from locally injected nerve growth factor (NGF). Here the roles of the same effectors, and of the tropomyosin receptor kinase A (TrkA) receptor, are evaluated for thermal hyperalgesia from NGF. Sensitivity of rat hind paw plantar skin to thermal stimulation after local sub-cutaneous injection of NGF (500ng) was measured by the latency for paw withdrawal (PWL) from a radiant heat source. PWL was reduced from baseline values at 0.5-22h by ∼40% from that in naïve or vehicle-injected rats, and recovered to pre-injection levels by 48h. Local pre-injection with a p75NTR blocking antibody did not affect the acute thermal hyperalgesia (0.5-3.5h) but hastened its recovery so that it had reversed to baseline by 22h. In addition, GW4869 (2mM), an inhibitor of the neutral sphingomyelinase (nSMase) that is an enzyme in the p75NTR pathway, also failed to prevent thermal hyperalgesia. However, C2-ceramide, an analog of the ceramide produced by sphingomyelinase, did cause thermal hyperalgesia. Injection of an anti-TrkA antibody known to promote dimerization and activation of that receptor, independent of NGF, also caused thermal hyperalgesia, and prevented the further reduction of PWL from subsequently injected NGF. A non-specific inhibitor of tropomyosin receptor kinases, K252a, prevented thermal hyperalgesia from NGF, but not that from the anti-TrkA antibody. These findings suggest that the TrkA receptor has a predominant role in thermal hypersensitivity induced by NGF, while p75NTR and its pathway intermediates serve a modulatory role.
Collapse
Affiliation(s)
- Alla Khodorova
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, USA
| | - Grant D Nicol
- Department of Pharmacology and Toxicology, Indiana University School of Medicine, Indianapolis, IN 46202, USA
| | - Gary Strichartz
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, USA.
| |
Collapse
|
30
|
Abstract
Second messengers are small molecules and ions that relay signals received by cell-surface receptors to effector proteins. They include a wide variety of chemical species and have diverse properties that allow them to signal within membranes (e.g., hydrophobic molecules such as lipids and lipid derivatives), within the cytosol (e.g., polar molecules such as nucleotides and ions), or between the two (e.g., gases and free radicals). Second messengers are typically present at low concentrations in resting cells and can be rapidly produced or released when cells are stimulated. The levels of second messengers are exquisitely controlled temporally and spatially, and, during signaling, enzymatic reactions or opening of ion channels ensure that they are highly amplified. These messengers then diffuse rapidly from the source and bind to target proteins to alter their properties (activity, localization, stability, etc.) to propagate signaling.
Collapse
Affiliation(s)
- Alexandra C Newton
- Department of Pharmacology, University of California at San Diego, La Jolla, California 92093
| | - Martin D Bootman
- Department of Life, Health and Chemical Sciences, The Open University, Walton Hall, Milton Keynes MK7 6AA, United Kingdom
| | - John D Scott
- Department of Pharmacology, Howard Hughes Medical Institute, University of Washington School of Medicine, Seattle, Washington 98195
| |
Collapse
|
31
|
Svobodova B, Groschner K. Reprint of "Mechanisms of lipid regulation and lipid gating in TRPC channels". Cell Calcium 2016; 60:133-41. [PMID: 27431463 DOI: 10.1016/j.ceca.2016.06.010] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/24/2016] [Accepted: 03/25/2016] [Indexed: 01/04/2023]
Abstract
TRPC proteins form cation channels that integrate and relay cellular signals by mechanisms involving lipid recognition and lipid-dependent gating. The lipohilic/amphiphilic molecules that function as cellular activators or modulators of TRPC proteins span a wide range of chemical structures. In this context, cellular redox balance is likely linked to the lipid recognition/gating features of TRPC channels. Both classical ligand-protein interactions as well as indirect and promiscuous sensory mechanisms have been proposed. Some of the recognition processes are suggested to involve ancillary lipid-binding scaffolds or regulators as well as dynamic protein-protein interactions determined by bilayer architecture. A complex interplay of protein-protein and protein-lipid interactions is likely to govern the gating and/or plasma membrane recruitment of TRPC channels, thereby providing a distinguished platform for signal integration and coincident signal detection. Both the primary molecular event(s) of lipid recognition by TRPC channels as well as the transformation of these events into distinct gating movements is poorly understood at the molecular level, and it remains elusive whether lipid sensing in TRPCs is conferred to a distinct sensor domain. Recent structural information on the molecular action of lipophilic activators in distantly related members of the TRP superfamily encourages speculations on TRPC gating mechanisms involved in lipid recognition/gating. This review aims to provide an update on the current understanding of the lipid-dependent control of TRPC channels with focus on the TRPC lipid sensing, signal-integration hub and a short discussion of potential links to redox signaling.
Collapse
Affiliation(s)
- Barbora Svobodova
- Institute of Biophysics, Medical University of Graz, A-8010 Graz, Austria
| | - Klaus Groschner
- Institute of Biophysics, Medical University of Graz, A-8010 Graz, Austria.
| |
Collapse
|
32
|
Mechanisms of lipid regulation and lipid gating in TRPC channels. Cell Calcium 2016; 59:271-9. [PMID: 27125985 DOI: 10.1016/j.ceca.2016.03.012] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2016] [Revised: 03/24/2016] [Accepted: 03/25/2016] [Indexed: 12/15/2022]
Abstract
TRPC proteins form cation channels that integrate and relay cellular signals by mechanisms involving lipid recognition and lipid-dependent gating. The lipohilic/amphiphilic molecules that function as cellular activators or modulators of TRPC proteins span a wide range of chemical structures. In this context, cellular redox balance is likely linked to the lipid recognition/gating features of TRPC channels. Both classical ligand-protein interactions as well as indirect and promiscuous sensory mechanisms have been proposed. Some of the recognition processes are suggested to involve ancillary lipid-binding scaffolds or regulators as well as dynamic protein-protein interactions determined by bilayer architecture. A complex interplay of protein-protein and protein-lipid interactions is likely to govern the gating and/or plasma membrane recruitment of TRPC channels, thereby providing a distinguished platform for signal integration and coincident signal detection. Both the primary molecular event(s) of lipid recognition by TRPC channels as well as the transformation of these events into distinct gating movements is poorly understood at the molecular level, and it remains elusive whether lipid sensing in TRPCs is conferred to a distinct sensor domain. Recent structural information on the molecular action of lipophilic activators in distantly related members of the TRP superfamily encourages speculations on TRPC gating mechanisms involved in lipid recognition/gating. This review aims to provide an update on the current understanding of the lipid-dependent control of TRPC channels with focus on the TRPC lipid sensing, signal-integration hub and a short discussion of potential links to redox signaling.
Collapse
|
33
|
Staveness D, Abdelnabi R, Schrier AJ, Loy B, Verma VA, DeChristopher BA, Near KE, Neyts J, Delang L, Leyssen P, Wender PA. Simplified Bryostatin Analogues Protect Cells from Chikungunya Virus-Induced Cell Death. JOURNAL OF NATURAL PRODUCTS 2016; 79:675-9. [PMID: 26900625 PMCID: PMC4928627 DOI: 10.1021/acs.jnatprod.5b01016] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Indexed: 05/21/2023]
Abstract
Chikungunya virus (CHIKV) is a mosquito-borne alphavirus showing a recent resurgence and rapid spread worldwide. While vaccines are under development, there are currently no therapies to treat this disease, except for over-the-counter (OTC) analgesics, which alleviate the devastating arthritic and arthralgic symptoms. To identify novel inhibitors of the virus, analogues of the natural product bryostatin 1, a clinical lead for the treatment of cancer, Alzheimer's disease, and HIV eradication, were investigated for in vitro antiviral activity and were found to be among the most potent inhibitors of CHIKV replication reported to date. Bryostatin-based therapeutic efforts and even recent anti-CHIKV strategies have centered on modulation of protein kinase C (PKC). Intriguingly, while the C ring of bryostatin primarily drives interactions with PKC, A- and B-ring functionality in these analogues has a significant effect on the observed cell-protective activity. Significantly, bryostatin 1 itself, a potent pan-PKC modulator, is inactive in these assays. These new findings indicate that the observed anti-CHIKV activity is not solely mediated by PKC modulation, suggesting possible as yet unidentified targets for CHIKV therapeutic intervention. The high potency and low toxicity of these bryologs make them promising new leads for the development of a CHIKV treatment.
Collapse
Affiliation(s)
- Daryl Staveness
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
| | - Rana Abdelnabi
- Department of Microbiology and Immunology, Rega Institute for Medical
Research, Laboratory of Virology and Chemotherapy, KU Leuven−University of Leuven, B-3000 Leuven, Belgium
| | - Adam J. Schrier
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
| | - Brian
A. Loy
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
| | - Vishal A. Verma
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
| | - Brian A. DeChristopher
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
| | - Katherine E. Near
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
| | - Johan Neyts
- Department of Microbiology and Immunology, Rega Institute for Medical
Research, Laboratory of Virology and Chemotherapy, KU Leuven−University of Leuven, B-3000 Leuven, Belgium
- E-mail:
| | - Leen Delang
- Department of Microbiology and Immunology, Rega Institute for Medical
Research, Laboratory of Virology and Chemotherapy, KU Leuven−University of Leuven, B-3000 Leuven, Belgium
| | - Pieter Leyssen
- Department of Microbiology and Immunology, Rega Institute for Medical
Research, Laboratory of Virology and Chemotherapy, KU Leuven−University of Leuven, B-3000 Leuven, Belgium
| | - Paul A. Wender
- Departments of Chemistry and Chemical and
Systems Biology, Stanford University, Stanford, California 94305, United States
- E-mail:
| |
Collapse
|
34
|
Naik E, Dixit VM. Usp9X Is Required for Lymphocyte Activation and Homeostasis through Its Control of ZAP70 Ubiquitination and PKCβ Kinase Activity. THE JOURNAL OF IMMUNOLOGY 2016; 196:3438-51. [PMID: 26936881 DOI: 10.4049/jimmunol.1403165] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/19/2014] [Accepted: 02/09/2016] [Indexed: 11/19/2022]
Abstract
To achieve a durable adaptive immune response, lymphocytes must undergo clonal expansion and induce a survival program that enables the persistence of Ag-experienced cells and the development of memory. During the priming phase of this response, CD4(+)T lymphocytes either remain tolerized or undergo clonal expansion. In this article, we show that Usp9X functions as a positive regulatory switch during T lymphocyte priming through removal of inhibitory monoubiquitination from ZAP70. In the absence of Usp9X, an increased amount of ZAP70 localized to early endosomes consistent with the role of monoubiquitin in endocytic sorting. Usp9X becomes competent to deubiquitinate ZAP70 through TCR-dependent phosphorylation and enhancement of its catalytic activity and association with the LAT signalosome. In B lymphocytes, Usp9X is required for the induction of PKCβ kinase activity after BCR-dependent activation. Accordingly, inUsp9Xknockout B cells, there was a significant reduction in phospho-CARMA1 levels that resulted in reduced CARMA1/Bcl-10/MALT-1 complex formation and NF-κB-dependent cell survival. The pleiotropic effect of Usp9X during Ag-receptor signaling highlights its importance for the development of an effective and durable adaptive immune response.
Collapse
Affiliation(s)
- Edwina Naik
- Department of Physiological Chemistry, Genentech, Inc., South San Francisco, CA 94080
| | - Vishva M Dixit
- Department of Physiological Chemistry, Genentech, Inc., South San Francisco, CA 94080
| |
Collapse
|
35
|
Kamerbeek CB, Mateos MV, Vallés AS, Pediconi MF, Barrantes FJ, Borroni V. Diacylglycerol levels modulate the cellular distribution of the nicotinic acetylcholine receptor. Int J Biochem Cell Biol 2016; 74:1-11. [PMID: 26898898 DOI: 10.1016/j.biocel.2016.02.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2015] [Revised: 02/03/2016] [Accepted: 02/15/2016] [Indexed: 10/22/2022]
Abstract
Diacylglycerol (DAG), a second messenger involved in different cell signaling cascades, activates protein kinase C (PKC) and D (PKD), among other kinases. The present work analyzes the effects resulting from the alteration of DAG levels on neuronal and muscle nicotinic acetylcholine receptor (AChR) distribution. We employ CHO-K1/A5 cells, expressing adult muscle-type AChR in a stable manner, and hippocampal neurons, which endogenously express various subtypes of neuronal AChR. CHO-K1/A5 cells treated with dioctanoylglycerol (DOG) for different periods showed augmented AChR cell surface levels at short incubation times (30min-4h) whereas at longer times (18h) the AChR was shifted to intracellular compartments. Similarly, in cultured hippocampal neurons surface AChR levels increased as a result of DOG incubation for 4h. Inhibition of endogenous DAG catabolism produced changes in AChR distribution similar to those induced by DOG treatment. Specific enzyme inhibitors and Western blot assays revealed that DAGs exert their effect on AChR distribution through the modulation of the activity of classical PKC (cPKC), novel PKC (nPKC) and PKD activity.
Collapse
Affiliation(s)
- Constanza B Kamerbeek
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Melina V Mateos
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Ana S Vallés
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - María F Pediconi
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina
| | - Francisco J Barrantes
- Laboratory of Molecular Neurobiology, Institute for Biomedical Research UCA-CONICET, Faculty of Medical Sciences, Av. Alicia Moreau de Justo 1600, C1107AFF Buenos Aires, Argentina
| | - Virginia Borroni
- Instituto de Investigaciones Bioquímicas de Bahía Blanca, Camino La Carrindanga km 7, 8000 Bahía Blanca, Argentina.
| |
Collapse
|
36
|
Novel Features of DAG-Activated PKC Isozymes Reveal a Conserved 3-D Architecture. J Mol Biol 2016; 428:121-141. [DOI: 10.1016/j.jmb.2015.11.001] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2015] [Accepted: 11/01/2015] [Indexed: 01/17/2023]
|
37
|
Shende P, Xu L, Morandi C, Pentassuglia L, Heim P, Lebboukh S, Berthonneche C, Pedrazzini T, Kaufmann BA, Hall MN, Rüegg MA, Brink M. Cardiac mTOR complex 2 preserves ventricular function in pressure-overload hypertrophy. Cardiovasc Res 2015; 109:103-14. [DOI: 10.1093/cvr/cvv252] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/08/2015] [Accepted: 11/06/2015] [Indexed: 11/12/2022] Open
|
38
|
Abstract
Protein kinase C (PKC) is a family of Ser/Thr kinases that regulate a multitude of cellular processes through participation in the phosphoinositide signaling pathway. Significant research efforts have been directed at understanding the structure, function, and regulatory modes of the enzyme since its discovery and identification as the first receptor for tumor-promoting phorbol esters. The activation of PKC involves a transition from the cytosolic autoinhibited latent form to the membrane-associated active form. The membrane recruitment step is accompanied by the conformational rearrangement of the enzyme, which relieves autoinhibitory interactions and thereby allows PKC to phosphorylate its targets. The multidomain structure and intrinsic flexibility of PKC present remarkable challenges and opportunities for the biophysical and structural biology studies of this class of enzymes and their interactions with membranes, the major focus of this Current Topic. I will highlight the recent advances in the field, outline the current challenges, and identify areas where biophysics and structural biology approaches can provide insight into the isoenzyme-specific regulation of PKC activity.
Collapse
|
39
|
Differential targeting of cPKC and nPKC decodes and regulates Ca2+ and lipid signalling. Biochem Soc Trans 2014; 42:1538-42. [DOI: 10.1042/bst20140239] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Protein kinases C (PKCs) are ubiquitously expressed and play critical roles in a plethora of physiological and pathophysiological processes. Owing to PKCs’ highly conserved phosphorylation consensus sequence, it has been difficult to distinguish the role of individual PKC isoforms. Recently, the identification of novel membrane targeting via subcellularly targeted diacylglycerol production found for novel PKCs (nPKCs), together with a characterization of their putative functions, has shed new light on the specific roles of individual PKCs in cellular processes.
Collapse
|
40
|
Stewart MD, Cole TR, Igumenova TI. Interfacial partitioning of a loop hinge residue contributes to diacylglycerol affinity of conserved region 1 domains. J Biol Chem 2014; 289:27653-64. [PMID: 25124034 DOI: 10.1074/jbc.m114.585570] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Conventional and novel isoenzymes of PKC are activated by the membrane-embedded second messenger diacylglycerol (DAG) through its interactions with the C1 regulatory domain. The affinity of C1 domains to DAG varies considerably among PKCs. To gain insight into the origin of differential DAG affinities, we conducted high-resolution NMR studies of C1B domain from PKCδ (C1Bδ) and its W252Y variant. The W252Y mutation was previously shown to render C1Bδ less responsive to DAG (Dries, D. R., Gallegos, L. L., and Newton, A. C. (2007) A single residue in the C1 domain sensitizes novel protein kinase C isoforms to cellular diacylglycerol production. J. Biol. Chem. 282, 826-830) and thereby emulate the behavior of C1B domains from conventional PKCs that have a conserved Tyr at the equivalent position. Our data revealed that W252Y mutation did not perturb the conformation of C1Bδ in solution but significantly reduced its propensity to partition into a membrane-mimicking environment in the absence of DAG. Using detergent micelles doped with a paramagnetic lipid, we determined that both the residue identity at position 252 and complexation with diacylglycerol influence the geometry of C1Bδ-micelle interactions. In addition, we identified the C-terminal helix α1 of C1Bδ as an interaction site with the head groups of phosphatidylserine, a known activator of PKCδ. Taken together, our studies (i) reveal the identities of C1Bδ residues involved in interactions with membrane-mimicking environment, DAG, and phosphatidylserine, as well as the affinities associated with each event and (ii) suggest that the initial ligand-independent membrane recruitment of C1B domains, which is greatly facilitated by the interfacial partitioning of Trp-252, is responsible, at least in part, for the differential DAG affinities.
Collapse
Affiliation(s)
- Mikaela D Stewart
- From the Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843
| | - Taylor R Cole
- From the Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843
| | - Tatyana I Igumenova
- From the Department of Biochemistry and Biophysics, Texas A&M University, College Station, Texas 77843
| |
Collapse
|
41
|
Egea-Jiménez AL, Corbalán-García S, Gómez-Fernández JC. The C1B domains of novel PKCε and PKCη have a higher membrane binding affinity than those of the also novel PKCδ and PKCθ. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1898-909. [DOI: 10.1016/j.bbamem.2014.04.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Revised: 03/28/2014] [Accepted: 04/02/2014] [Indexed: 10/25/2022]
|
42
|
Wender PA, Donnelly AC, Loy BA, Near KE, Staveness D. Rethinking the Role of Natural Products: Function-Oriented Synthesis, Bryostatin, and Bryologs. METHODS AND PRINCIPLES IN MEDICINAL CHEMISTRY 2014. [DOI: 10.1002/9783527676545.ch14] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
|
43
|
Ziemba BP, Li J, Landgraf KE, Knight JD, Voth GA, Falke JJ. Single-molecule studies reveal a hidden key step in the activation mechanism of membrane-bound protein kinase C-α. Biochemistry 2014; 53:1697-713. [PMID: 24559055 PMCID: PMC3971957 DOI: 10.1021/bi4016082] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
![]()
Protein
kinase C-α (PKCα) is a member of the conventional
family of protein kinase C isoforms (cPKCs) that regulate diverse
cellular signaling pathways, share a common activation mechanism,
and are linked to multiple pathologies. The cPKC domain structure
is modular, consisting of an N-terminal pseudosubstrate peptide, two
inhibitory domains (C1A and C1B), a targeting domain (C2), and a kinase
domain. Mature, cytoplasmic cPKCs are inactive until they are switched
on by a multistep activation reaction that occurs largely on the plasma
membrane surface. Often, this activation begins with a cytoplasmic
Ca2+ signal that triggers C2 domain targeting to the plasma
membrane where it binds phosphatidylserine (PS) and phosphatidylinositol
4,5-bisphosphate (PIP2). Subsequently, the appearance of
the signaling lipid diacylglycerol (DAG) activates the membrane-bound
enzyme by recruiting the inhibitory pseudosubstrate and one or both
C1 domains away from the kinase domain. To further investigate this
mechanism, this study has utilized single-molecule total internal
reflection fluorescence microscopy (TIRFM) to quantitate the binding
and lateral diffusion of full-length PKCα and fragments missing
specific domain(s) on supported lipid bilayers. Lipid binding events,
and events during which additional protein is inserted into the bilayer,
were detected by their effects on the equilibrium bound particle density
and the two-dimensional diffusion rate. In addition to the previously
proposed activation steps, the findings reveal a major, undescribed,
kinase-inactive intermediate. On bilayers containing PS or PS and
PIP2, full-length PKCα first docks to the membrane
via its C2 domain, and then its C1A domain embeds itself in the bilayer
even before DAG appears. The resulting pre-DAG intermediate with membrane-bound
C1A and C2 domains is the predominant state of PKCα while it
awaits the DAG signal. The newly detected, membrane-embedded C1A domain
of this pre-DAG intermediate confers multiple useful features, including
enhanced membrane affinity and longer bound state lifetime. The findings
also identify the key molecular step in kinase activation: because
C1A is already membrane-embedded in the kinase off state, recruitment
of C1B to the bilayer by DAG or phorbol ester is the key regulatory
event that stabilizes the kinase on state. More broadly, this study
illustrates the power of single-molecule methods in elucidating the
activation mechanisms and hidden regulatory states of membrane-bound
signaling proteins.
Collapse
Affiliation(s)
- Brian P Ziemba
- Department of Chemistry and Biochemistry and Molecular Biophysics Program, University of Colorado , Boulder, Colorado 80309-0596, United States
| | | | | | | | | | | |
Collapse
|
44
|
Khodorova A, Nicol GD, Strichartz G. The p75NTR signaling cascade mediates mechanical hyperalgesia induced by nerve growth factor injected into the rat hind paw. Neuroscience 2013; 254:312-23. [PMID: 24095693 DOI: 10.1016/j.neuroscience.2013.09.046] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2013] [Revised: 09/13/2013] [Accepted: 09/24/2013] [Indexed: 01/25/2023]
Abstract
Nerve growth factor (NGF) augments the excitability of isolated rat sensory neurons through activation of the p75 neurotrophin receptor (p75(NTR)) and its downstream sphingomyelin signaling cascade, wherein neutral sphingomyelinase(s) (nSMase), ceramide, and the atypical protein-kinase C (aPKC), protein-kinase M zeta (PKMζ), are key mediators. Here we examined these same receptor-pathways in vivo for their role in mechanical hyperalgesia from exogenous NGF. Mechanical sensitivity was tested by the number of paw withdrawals in response to 10 stimuli (PWF=n/10) by a 4-g von Frey hair (VFH, testing "allodynia") and by 10 and 15g VFHs (testing "hyperalgesia"). NGF (500ng/10μL) injected into the male rat's plantar hind paw induced long-lasting ipsilateral mechanical hypersensitivity. Mechano-hypersensitivity, relative to baseline responses and to those of the contralateral paw, developed by 0.5-1.5h and remained elevated at least for 21-24h, Acute intraplantar pre-treatment with nSMase inhibitors, glutathione (GSH) or GW4869, prevented the acute hyperalgesia from NGF (at 1.5h) but not that at 24h. A single injection of N-acetyl sphingosine (C2-ceramide), simulating the ceramide produced by nSMase activity, induced ipsilateral allodynia that persisted for 24h, and transient hyperalgesia that resolved by 2h. Intraplantar injection of hydrolysis-resistant mPro-NGF, selective for the p75(NTR) over the tyrosine kinase (TrkA) receptor, gave very similar results to NGF and was susceptible to the same inhibitors. Hyperalgesia from both NGF and mPro-NGF was prevented by paw pre-injection with blocking antibodies to rat p75(NTR) receptor. Finally, intraplantar (1day before NGF) injection of mPSI, the myristolated pseudosubstrate inhibitor of PKCζ/PKMζ, decreased the hyperalgesia resulting from NGF or C2-ceramide, although scrambled mPSI was ineffective. The findings indicate that mechano-hypersensitivity from peripheral NGF involves the sphingomyelin signaling cascade activated via p75(NTR), and that a peripheral aPKC is essential for this sensitization.
Collapse
Affiliation(s)
- A Khodorova
- Pain Research Center, Department of Anesthesiology, Perioperative and Pain Medicine, Brigham & Women's Hospital, Harvard Medical School, Boston, MA, USA
| | | | | |
Collapse
|
45
|
Antal CE, Newton AC. Spatiotemporal dynamics of phosphorylation in lipid second messenger signaling. Mol Cell Proteomics 2013; 12:3498-508. [PMID: 23788531 DOI: 10.1074/mcp.r113.029819] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
The plasma membrane serves as a dynamic interface that relays information received at the cell surface into the cell. Lipid second messengers coordinate signaling on this platform by recruiting and activating kinases and phosphatases. Specifically, diacylglycerol and phosphatidylinositol 3,4,5-trisphosphate activate protein kinase C and Akt, respectively, which then phosphorylate target proteins to transduce downstream signaling. This review addresses how the spatiotemporal dynamics of protein kinase C and Akt signaling can be monitored using genetically encoded reporters and provides information on how the coordination of signaling at protein scaffolds or membrane microdomains affords fidelity and specificity in phosphorylation events.
Collapse
Affiliation(s)
- Corina E Antal
- Department of Pharmacology, University of California at San Diego, La Jolla, California 92093-0721
| | | |
Collapse
|
46
|
Abstract
PKC (protein kinase C) has been in the limelight since the discovery three decades ago that it acts as a major receptor for the tumour-promoting phorbol esters. Phorbol esters, with their potent ability to activate two of the three classes of PKC isoenzymes, have remained the best pharmacological tool for directly modulating PKC activity. However, with the discovery of other phorbol ester-responsive proteins, the advent of various small-molecule and peptide modulators, and the need to distinguish isoenzyme-specific activity, the pharmacology of PKC has become increasingly complex. Not surprisingly, many of the compounds originally touted as direct modulators of PKC have subsequently been shown to hit many other cellular targets and, in some cases, not even directly modulate PKC. The complexities and reversals in PKC pharmacology have led to widespread confusion about the current status of the pharmacological tools available to control PKC activity. In the present review, we aim to clarify the cacophony in the literature regarding the current state of bona fide and discredited cellular PKC modulators, including activators, small-molecule inhibitors and peptides, and also address the use of genetically encoded reporters and of PKC mutants to measure the effects of these drugs on the spatiotemporal dynamics of signalling by specific isoenzymes.
Collapse
Affiliation(s)
- Alyssa X. Wu-Zhang
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093-0721, (858) 534-4527, Fax: (858) 822-5888
| | - Alexandra C. Newton
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093-0721, (858) 534-4527, Fax: (858) 822-5888
| |
Collapse
|
47
|
Scott AM, Antal CE, Newton AC. Electrostatic and hydrophobic interactions differentially tune membrane binding kinetics of the C2 domain of protein kinase Cα. J Biol Chem 2013; 288:16905-16915. [PMID: 23589289 DOI: 10.1074/jbc.m113.467456] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The cellular activation of conventional protein kinase C (PKC) isozymes is initiated by the binding of their C2 domains to membranes in response to elevations in intracellular Ca(2+). Following this C2 domain-mediated membrane recruitment, the C1 domain binds its membrane-embedded ligand diacylglycerol, resulting in activation of PKC. Here we explore the molecular mechanisms by which the C2 domain controls the initial step in the activation of PKC. Using stopped-flow fluorescence spectroscopy to measure association and dissociation rate constants, we show that hydrophobic interactions are the major driving force in the binding of the C2 domain to anionic membranes, whereas electrostatic interactions dominate in membrane retention. Specifically, mutation of select hydrophobic or select basic residues in the Ca(2+)-binding loops reduces membrane affinity by distinct mechanisms; mutation of hydrophobic residues primarily alters association rate constants, whereas mutation of charged residues affects dissociation rate constants. Live cell imaging reveals that introduction of these mutations into full-length PKCα not only reduces the Ca(2+)-dependent translocation to plasma membrane but, by impairing the plasma membrane-sensing role of the C2 domain, causes phorbol ester-triggered redistribution of PKCα to other membranes, such as the Golgi. These data underscore the key role of the C2 domain in driving conventional PKC isozymes to the plasma membrane and reveal that not only the amplitude but also the subcellular location of conventional PKC signaling can be tuned by altering the affinity of this module for membranes.
Collapse
Affiliation(s)
- Angela M Scott
- Department of Pharmacology, La Jolla, California 92093-0721; Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California 92093-0721
| | - Corina E Antal
- Department of Pharmacology, La Jolla, California 92093-0721; Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, California 92093-0721
| | | |
Collapse
|
48
|
Roles of Protein Kinase C and Protein Kinase M in Aplysia Learning. ACTA ACUST UNITED AC 2013. [DOI: 10.1016/b978-0-12-415823-8.00018-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
|
49
|
Gharbi SI, Avila-Flores A, Soutar D, Orive A, Koretzky GA, Albar JP, Mérida I. Transient PKCα shuttling to the immunological synapse is governed by (DGK)ζ and regulates L-selectin shedding. J Cell Sci 2013; 126:2176-86. [DOI: 10.1242/jcs.118513] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Considerable evidence indicates that diacylglycerol (DAG) generation at the immunological synapse (IS) determines T cell functions by regulating the duration and amplitude of Ras/ERK signals. The exact mechanism by which DAG regulates Ras/ERK activation downstream of the T cell receptor (TCR) nonetheless remains poorly understood. Here we characterize PKCα as a previously unrecognized component of the machinery that translates cell receptor occupancy into Ras/ERK-propagated signals. We show transient translocation of PKCα to the IS, mediated by DAG generation at the contact area. Diacylglycerol kinase (DGK)ζ negatively regulated PKCα translocation kinetics, whereas PKCα activity limited its own persistence at the IS. Coordinated activation of DGKζ and PKCα in response to antigen recognition regulated the amplitude and duration of Ras/ERK activation; this in turn mediated early processes of T cell surface proteolysis such as L-selectin shedding. Analysis of DGKζ-deficient mice further showed that increased DAG signaling is translated to downstream elements of this pathway, as reflected by enhanced PKCα-dependent L-selectin shedding. We propose that early activation of a DAG/PKCα axis contributes to the mechanisms by which antigen affinity translates into TCR biological responses.
Collapse
|
50
|
Farah CA, Sossin WS. The role of C2 domains in PKC signaling. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2012; 740:663-83. [PMID: 22453964 DOI: 10.1007/978-94-007-2888-2_29] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
More than two decades ago, the discovery of the first C2 domain in conventional Protein Kinase Cs (cPKCs) and of its role as a calcium-binding motif began to shed light on the activation mechanism of this family of Serine/Threonine kinases which are involved in several critical signal transduction pathways. In this chapter, we review the current knowledge of the structure and the function of the different C2 domains in PKCs. The C2 domain of cPKCs is a calcium sensor and its calcium-dependent binding to phospholipids is crucial for kinase activation. While the functional role of the cPKC C2 domain is better understood, phylogenetic analysis revealed that the novel C2 domain is more ancient and related to the C2 domain in the fungal PKC family, while the cPKC C2 domain is first associated with PKC in metazoans. The C2 domain of novel PKCs (nPKCs) does not contain a calcium-binding motif but still plays a critical role in nPKCs activation by regulating C1-C2 domain interactions and consequently C2 domain-mediated inhibition in both the nPKCs of the epsilon family and the nPKCs of the delta family. Moreover, the C2 domain of the nPKCs of the delta family was shown to recognize phosphotyrosines in a novel mode different from the ones observed for the Src Homology 2 (SH2) and the phosphotyrosine binding domains (PTB). By binding to phosphotyrosines, the C2 domain regulates the activation of this subclass of PKCs. The C2 domain was also shown to be involved in protein-protein interactions and binding to the receptor for activated C-kinase (RACKs) thus contributing to the subcellular localization of PKCs. In summary, the C2 domain is a critical player that can sense the activated signaling pathway in response to external stimuli to specifically regulate the different conventional and novel PKC isoforms.
Collapse
Affiliation(s)
- Carole A Farah
- Department of Neurology and Neurosurgery, Montreal Neurological Institute, McGill University, BT 105, 3801 University Street, Montreal, QC H3A 2B4, Canada.
| | | |
Collapse
|