1
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Black JD, Affandi T, Black AR, Reyland ME. PKCα and PKCδ: Friends and Rivals. J Biol Chem 2022; 298:102194. [PMID: 35760100 PMCID: PMC9352922 DOI: 10.1016/j.jbc.2022.102194] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 06/13/2022] [Accepted: 06/21/2022] [Indexed: 01/06/2023] Open
Abstract
PKC comprises a large family of serine/threonine kinases that share a requirement for allosteric activation by lipids. While PKC isoforms have significant homology, functional divergence is evident among subfamilies and between individual PKC isoforms within a subfamily. Here, we highlight these differences by comparing the regulation and function of representative PKC isoforms from the conventional (PKCα) and novel (PKCδ) subfamilies. We discuss how unique structural features of PKCα and PKCδ underlie differences in activation and highlight the similar, divergent, and even opposing biological functions of these kinases. We also consider how PKCα and PKCδ can contribute to pathophysiological conditions and discuss challenges to targeting these kinases therapeutically.
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Affiliation(s)
- Jennifer D Black
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE.
| | - Trisiani Affandi
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus
| | - Adrian R Black
- Eppley Institute for Research in Cancer and Allied Diseases, University of Nebraska Medical Center, Omaha, NE
| | - Mary E Reyland
- Department of Craniofacial Biology, School of Dental Medicine, University of Colorado Anschutz Medical Campus.
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2
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Serrano-López EM, López-Martínez D, Gómez-Fernández JC, Egea-Jiménez AL, Corbalán-García S. PKCε controls the fusion of secretory vesicles in mast cells in a phosphatidic acid-dependent mode. Int J Biol Macromol 2021; 185:377-389. [PMID: 34147527 DOI: 10.1016/j.ijbiomac.2021.06.019] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 05/28/2021] [Accepted: 06/02/2021] [Indexed: 11/28/2022]
Abstract
PKCε is highly expressed in mast cells and plays a fundamental role in the antigen-triggered activation of the allergic reaction. Although its regulation by diacylglycerols has been described, its regulation by acidic phospholipids and how this regulation leads to the control of downstream vesicle secretion is barely known. Here, we used structural and evolutionary studies to find the molecular mechanism that explains the selectivity of the C1B domain of PKCε by Phosphatidic Acid (PA). This resided in a collection of Arg residues that form a specific rim on the outer surface of the C1B domain, around the diacylglycerol binding cleft. In RBL-2H3 cells, this basic rim allowed the kinase to respond specifically to phosphatidic acid signals that induced its translocation to the plasma membrane and subsequent activation. Further experiments in cells that overexpress PKCε and a mutant of the PA binding site, showed that PA-dependent PKCε activation increased vesicle degranulation in RBL-2H3 cells, and this correlated with increased SNAP23 phosphorylation. Over-expression of PKCε in these cells also induced an increase in the number of docked vesicles containing SNAP23, when stimulated with PA. This accumulation could be attributed to the stabilizing effect of phosphorylation on the formation of the SNARE complex, which ultimately led to increased release of content in the presence of Ca2+ during the fusion process. Therefore, these findings reinforce the importance of PA signaling in the activation of PKCε, which could be an important target to inhibit the exacerbated responses of these cells in the allergic reaction.
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Affiliation(s)
- Emilio M Serrano-López
- Department of Biochemistry and Molecular Biology A, Veterinary School, Universidad de Murcia, IMIB, CEIR Campus Mare Nostrum (CMN), Campus Espinardo, 30100 Murcia, Spain
| | - David López-Martínez
- Department of Biochemistry and Molecular Biology A, Veterinary School, Universidad de Murcia, IMIB, CEIR Campus Mare Nostrum (CMN), Campus Espinardo, 30100 Murcia, Spain
| | - Juan C Gómez-Fernández
- Department of Biochemistry and Molecular Biology A, Veterinary School, Universidad de Murcia, IMIB, CEIR Campus Mare Nostrum (CMN), Campus Espinardo, 30100 Murcia, Spain.
| | - Antonio Luis Egea-Jiménez
- Centre de Recherche en Cancérologie de Marseille (CRCM), Equipe labellisée LIGUE 2018, Aix-Marseille Université, Marseille F-13284, France; Inserm U1068, Institut Paoli-Calmettes, and CNRS UMR7258, Marseille F-13009, France.
| | - Senena Corbalán-García
- Department of Biochemistry and Molecular Biology A, Veterinary School, Universidad de Murcia, IMIB, CEIR Campus Mare Nostrum (CMN), Campus Espinardo, 30100 Murcia, Spain.
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3
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Bernier SC, Millette MA, Roy S, Cantin L, Coutinho A, Salesse C. Structural information and membrane binding of truncated RGS9-1 Anchor Protein and its C-terminal hydrophobic segment. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2021; 1863:183566. [PMID: 33453187 DOI: 10.1016/j.bbamem.2021.183566] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Subscribe] [Scholar Register] [Received: 09/11/2019] [Revised: 12/22/2020] [Accepted: 01/10/2021] [Indexed: 01/19/2023]
Abstract
Visual phototransduction takes place in photoreceptor cells. Light absorption by rhodopsin leads to the activation of transducin as a result of the exchange of its GDP for GTP. The GTP-bound ⍺-subunit of transducin then activates phosphodiesterase (PDE), which in turn hydrolyzes cGMP leading to photoreceptor hyperpolarization. Photoreceptors return to the dark state upon inactivation of these proteins. In particular, PDE is inactivated by the protein complex R9AP/RGS9-1/Gβ5. R9AP (RGS9-1 anchor protein) is responsible for the membrane anchoring of this protein complex to photoreceptor outer segment disk membranes most likely by the combined involvement of its C-terminal hydrophobic domain as well as other types of interactions. This study thus aimed to gather information on the structure and membrane binding of the C-terminal hydrophobic segment of R9AP as well as of truncated R9AP (without its C-terminal domain, R9AP∆TM). Circular dichroism and infrared spectroscopic measurements revealed that the secondary structure of R9AP∆TM mainly includes ⍺-helical structural elements. Moreover, intrinsic fluorescence measurements of native R9AP∆TM and individual mutants lacking one tryptophan demonstrated that W79 is more buried than W173 but that they are both located in a hydrophobic environment. This method also revealed that membrane binding of R9AP∆TM does not involve regions near its tryptophan residues, while infrared spectroscopy validated its binding to lipid vesicles. Additional fluorescence measurements showed that the C-terminal segment of R9AP is membrane embedded. Maximum insertion pressure and synergy data using Langmuir monolayers suggest that interactions with specific phospholipids could be involved in the membrane binding of R9AP∆TM.
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Affiliation(s)
- Sarah C Bernier
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Marc-Antoine Millette
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Sarah Roy
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Line Cantin
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada
| | - Ana Coutinho
- iBB-Institute for Bioengineering and Biosciences, Department of Bioengineering, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1049-001 Lisboa, Portugal; Department of Chemistry and Biochemistry, Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
| | - Christian Salesse
- CUO-Recherche, Centre de recherche du CHU de Québec and Département d'ophtalmologie, Faculté de Médecine, and Regroupement Stratégique PROTEO, Université Laval, Québec, Québec, Canada.
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König S, Jockenhöfer C, Billich C, Beer M, Machann J, Schmidt-Trucksäss A, Schütz U. Long distance running - Can bioprofiling predict success in endurance athletes? Med Hypotheses 2020; 146:110474. [PMID: 33418424 DOI: 10.1016/j.mehy.2020.110474] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Revised: 12/08/2020] [Accepted: 12/21/2020] [Indexed: 12/22/2022]
Abstract
The TransEuropeFootRace (TEFR) was one of the most extreme multistage competitions worldwide. The ultramarathon took the runners over a distance of 4487 km, from Bari, Italy, to the North Cape, Norway, in 64 days. The participating ultra-long-distance runners had to complete almost two marathons per day (~70 km). The race was accompanied by a research team analysing adaptations of different organ systems of the human body that were exposed to a chronic lack of regeneration time. Here, we analyzed runner's urine using mass spectrometric profiling of thousands of low-molecular weight compounds. The results indicated that pre-race molecular factors can predict finishers and separate them from nonfinishers already before the race. These observations were related to the training volume as finishers ran about twice as many kilometers per week before TEFR than nonfinishers, thus apparently achieving a higher performance level and resistance against overuse. While this hypothesis needs to be validated in future long-distance races, the bioprofiling experiments suggest that the competition readiness of the runners is measurable and might be adjustable.
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Affiliation(s)
- Simone König
- Core Unit Proteomics, Interdisciplinary Center for Clinical Research, University of Münster, Germany.
| | - Charlotte Jockenhöfer
- Core Unit Proteomics, Interdisciplinary Center for Clinical Research, University of Münster, Germany
| | - Christian Billich
- Clinic for Diagnostic and Interventional Radiology, University Hospital Ulm, Germany
| | - Meinrad Beer
- Clinic for Diagnostic and Interventional Radiology, University Hospital Ulm, Germany
| | - Jürgen Machann
- Institute for Diabetes Research and Metabolic Diseases (IDM) of the Helmholtz Center Munich at the University of Tübingen, Germany; German Center for Diabetes Research (DZD), Tübingen, Germany; Section on Experimental Radiology, Department of Diagnostic and Interventional Radiology, University Hospital Tübingen, Germany
| | - Arno Schmidt-Trucksäss
- Department of Sport, Exercise and Health, Division Sports and Exercise Medicine, University of Basel, Switzerland
| | - Uwe Schütz
- Clinic for Diagnostic and Interventional Radiology, University Hospital Ulm, Germany
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5
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Regulation of PI3K by PKC and MARCKS: Single-Molecule Analysis of a Reconstituted Signaling Pathway. Biophys J 2017; 110:1811-1825. [PMID: 27119641 DOI: 10.1016/j.bpj.2016.03.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2015] [Revised: 02/09/2016] [Accepted: 03/07/2016] [Indexed: 12/19/2022] Open
Abstract
In chemotaxing ameboid cells, a complex leading-edge signaling circuit forms on the cytoplasmic leaflet of the plasma membrane and directs both actin and membrane remodeling to propel the leading edge up an attractant gradient. This leading-edge circuit includes a putative amplification module in which Ca(2+)-protein kinase C (Ca(2+)-PKC) is hypothesized to phosphorylate myristoylated alanine-rich C kinase substrate (MARCKS) and release phosphatidylinositol-4,5-bisphosphate (PIP2), thereby stimulating production of the signaling lipid phosphatidylinositol-3,4,5-trisphosphate (PIP3) by the lipid kinase phosphoinositide-3-kinase (PI3K). We investigated this hypothesized Ca(2+)-PKC-MARCKS-PIP2-PI3K-PIP3 amplification module and tested its key predictions using single-molecule fluorescence to measure the surface densities and activities of its protein components. Our findings demonstrate that together Ca(2+)-PKC and the PIP2-binding peptide of MARCKS modulate the level of free PIP2, which serves as both a docking target and substrate lipid for PI3K. In the off state of the amplification module, the MARCKS peptide sequesters PIP2 and thereby inhibits PI3K binding to the membrane. In the on state, Ca(2+)-PKC phosphorylation of the MARCKS peptide reverses the PIP2 sequestration, thereby releasing multiple PIP2 molecules that recruit multiple active PI3K molecules to the membrane surface. These findings 1) show that the Ca(2+)-PKC-MARCKS-PIP2-PI3K-PIP3 system functions as an activation module in vitro, 2) reveal the molecular mechanism of activation, 3) are consistent with available in vivo data, and 4) yield additional predictions that are testable in live cells. More broadly, the Ca(2+)-PKC-stimulated release of free PIP2 may well regulate the membrane association of other PIP2-binding proteins, and the findings illustrate the power of single-molecule analysis to elucidate key dynamic and mechanistic features of multiprotein signaling pathways on membrane surfaces.
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6
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Filter JJ, Williams BC, Eto M, Shalloway D, Goldberg ML. Unfair competition governs the interaction of pCPI-17 with myosin phosphatase (PP1-MYPT1). eLife 2017; 6. [PMID: 28387646 PMCID: PMC5441869 DOI: 10.7554/elife.24665] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Accepted: 03/31/2017] [Indexed: 11/30/2022] Open
Abstract
The small phosphoprotein pCPI-17 inhibits myosin light-chain phosphatase (MLCP). Current models postulate that during muscle relaxation, phosphatases other than MLCP dephosphorylate and inactivate pCPI-17 to restore MLCP activity. We show here that such hypotheses are insufficient to account for the observed rapidity of pCPI-17 inactivation in mammalian smooth muscles. Instead, MLCP itself is the critical enzyme for pCPI-17 dephosphorylation. We call the mutual sequestration mechanism through which pCPI-17 and MLCP interact inhibition by unfair competition: MLCP protects pCPI-17 from other phosphatases, while pCPI-17 blocks other substrates from MLCP’s active site. MLCP dephosphorylates pCPI-17 at a slow rate that is, nonetheless, both sufficient and necessary to explain the speed of pCPI-17 dephosphorylation and the consequent MLCP activation during muscle relaxation. DOI:http://dx.doi.org/10.7554/eLife.24665.001
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Affiliation(s)
- Joshua J Filter
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Byron C Williams
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Masumi Eto
- Department of Molecular Physiology and Biophysics, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, United States
| | - David Shalloway
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
| | - Michael L Goldberg
- Department of Molecular Biology and Genetics, Cornell University, Ithaca, United States
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7
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Swanson CJ, Sommese RF, Petersen KJ, Ritt M, Karslake J, Thomas DD, Sivaramakrishnan S. Calcium Stimulates Self-Assembly of Protein Kinase C α In Vitro. PLoS One 2016; 11:e0162331. [PMID: 27706148 PMCID: PMC5051681 DOI: 10.1371/journal.pone.0162331] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2016] [Accepted: 08/22/2016] [Indexed: 11/18/2022] Open
Abstract
Protein kinase C α (PKCα) is a nodal regulator in several intracellular signaling networks. PKCα is composed of modular domains that interact with each other to dynamically regulate spatial-temporal function. We find that PKCα specifically, rapidly and reversibly self-assembles in the presence of calcium in vitro. This phenomenon is dependent on, and can be modulated by an intramolecular interaction between the C1a and C2 protein domains of PKCα. Next, we monitor self-assembly of PKC—mCitrine fusion proteins using time-resolved and steady-state homoFRET. HomoFRET between full-length PKCα molecules is observed when in solution with both calcium and liposomes containing either diacylglycerol (DAG) or phosphatidylinositol 4,5-bisphosphate (PI(4,5)P2). Surprisingly, the C2 domain is sufficient to cluster on liposomes containing PI(4,5)P2, indicating the C1a domain is not required for self-assembly in this context. We conclude that three distinct clustered states of PKCα can be formed depending on what combination of cofactors are bound, but Ca2+ is minimally required and sufficient for clustering.
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Affiliation(s)
- Carter J. Swanson
- Biophysics Program, University of Michigan, Ann Arbor, 48109, United States of America
| | - Ruth F. Sommese
- Dept. of Genetics, Cell Biology and Development, University of Minnesota, Twin Cities, 55455, United States of America
| | - Karl J. Petersen
- Dept. of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Twin Cities, 55455, United States of America
| | - Michael Ritt
- Dept. of Genetics, Cell Biology and Development, University of Minnesota, Twin Cities, 55455, United States of America
| | - Joshua Karslake
- Biophysics Program, University of Michigan, Ann Arbor, 48109, United States of America
| | - David D. Thomas
- Dept. of Biochemistry, Molecular Biology, and Biophysics, University of Minnesota, Twin Cities, 55455, United States of America
| | - Sivaraj Sivaramakrishnan
- Dept. of Genetics, Cell Biology and Development, University of Minnesota, Twin Cities, 55455, United States of America
- * E-mail:
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Lum MA, Barger CJ, Hsu AH, Leontieva OV, Black AR, Black JD. Protein Kinase Cα (PKCα) Is Resistant to Long Term Desensitization/Down-regulation by Prolonged Diacylglycerol Stimulation. J Biol Chem 2016; 291:6331-46. [PMID: 26769967 DOI: 10.1074/jbc.m115.696211] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2015] [Indexed: 11/06/2022] Open
Abstract
Sustained activation of PKCα is required for long term physiological responses, such as growth arrest and differentiation. However, studies with pharmacological agonists (e.g. phorbol 12-myristate 13-acetate (PMA)) indicate that prolonged stimulation leads to PKCα desensitization via dephosphorylation and/or degradation. The current study analyzed effects of chronic stimulation with the physiological agonist diacylglycerol. Repeated addition of 1,2-dioctanoyl-sn-glycerol (DiC8) resulted in sustained plasma membrane association of PKCα in a pattern comparable with that induced by PMA. However, although PMA potently down-regulated PKCα, prolonged activation by DiC8 failed to engage known desensitization mechanisms, with the enzyme remaining membrane-associated and able to support sustained downstream signaling. DiC8-activated PKCα did not undergo dephosphorylation, ubiquitination, or internalization, early events in PKCα desensitization. Although DiC8 efficiently down-regulated novel PKCs PKCδ and PKCϵ, differences in Ca(2+) sensitivity and diacylglycerol affinity were excluded as mediators of the selective resistance of PKCα. Roles for Hsp/Hsc70 and Hsp90 were also excluded. PMA, but not DiC8, targeted PKCα to detergent-resistant membranes, and disruption of these domains with cholesterol-binding agents demonstrated a role for differential membrane compartmentalization in selective agonist-induced degradation. Chronic DiC8 treatment failed to desensitize PKCα in several cell types and did not affect PKCβI; thus, conventional PKCs appear generally insensitive to desensitization by sustained diacylglycerol stimulation. Consistent with this conclusion, prolonged (several-day) membrane association/activation of PKCα is seen in self-renewing epithelium of the intestine, cervix, and skin. PKCα deficiency affects gene expression, differentiation, and tumorigenesis in these tissues, highlighting the importance of mechanisms that protect PKCα from desensitization in vivo.
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Affiliation(s)
- Michelle A Lum
- From the Eppley Institute for Research in Cancer and Allied Diseases and the Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950 and the Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263
| | - Carter J Barger
- From the Eppley Institute for Research in Cancer and Allied Diseases and the Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950 and
| | - Alice H Hsu
- From the Eppley Institute for Research in Cancer and Allied Diseases and the Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950 and
| | - Olga V Leontieva
- the Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263
| | - Adrian R Black
- From the Eppley Institute for Research in Cancer and Allied Diseases and the Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950 and the Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263
| | - Jennifer D Black
- From the Eppley Institute for Research in Cancer and Allied Diseases and the Fred and Pamela Buffet Cancer Center, University of Nebraska Medical Center, Omaha, Nebraska 68198-5950 and the Department of Pharmacology and Therapeutics, Roswell Park Cancer Institute, Buffalo, New York 14263
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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.
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Affiliation(s)
- Brian P Ziemba
- Department of Chemistry and Biochemistry and Molecular Biophysics Program, University of Colorado , Boulder, Colorado 80309-0596, United States
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10
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Signaling through C2 domains: more than one lipid target. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2014; 1838:1536-47. [PMID: 24440424 DOI: 10.1016/j.bbamem.2014.01.008] [Citation(s) in RCA: 156] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Revised: 12/30/2013] [Accepted: 01/07/2014] [Indexed: 02/05/2023]
Abstract
C2 domains are membrane-binding modules that share a common overall fold: a single compact Greek-key motif organized as an eight-stranded anti-parallel β-sandwich consisting of a pair of four-stranded β-sheets. A myriad of studies have demonstrated that in spite of sharing the common structural β-sandwich core, slight variations in the residues located in the interconnecting loops confer C2 domains with functional abilities to respond to different Ca(2+) concentrations and lipids, and to signal through protein-protein interactions as well. This review summarizes the main structural and functional findings on Ca(2+) and lipid interactions by C2 domains, including the discovery of the phosphoinositide-binding site located in the β3-β4 strands. The wide variety of functions, together with the different Ca(2+) and lipid affinities of these domains, converts this superfamily into a crucial player in many functions in the cell and more to be discovered. This Article is Part of a Special Issue Entitled: Membrane Structure and Function: Relevance in the Cell's Physiology, Pathology and Therapy.
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11
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Vermaas JV, Tajkhorshid E. A microscopic view of phospholipid insertion into biological membranes. J Phys Chem B 2013; 118:1754-64. [PMID: 24313792 DOI: 10.1021/jp409854w] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
Understanding the process of membrane insertion is an essential step in developing a detailed mechanism, for example, for peripheral membrane protein association and membrane fusion. The highly mobile membrane mimetic (HMMM) has been used to accelerate the membrane association and binding of peripheral membrane proteins in simulations by increasing the lateral diffusion of phospholipid headgroups while retaining an atomistic description of the interface. Through a comparative study, we assess the difference in insertion rate of a free phospholipid into an HMMM as well as into a conventional phospholipid bilayer and develop a detailed mechanistic model of free phospholipid insertion into biological membranes. The mechanistic insertion model shows that successful irreversible association of the free phospholipid to the membrane interface, which results in its insertion, is the rate-limiting step. Association is followed by independent, sequential insertion of the acyl tails of the free phospholipid into the membrane, with splayed acyl tail intermediates. Use of the HMMM is found to replicate the same intermediate insertion states as in the full phospholipid bilayer; however, it accelerates overall insertion by approximately a factor of 3, with the probability of successful association of phospholipid to the membrane being significantly enhanced.
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Affiliation(s)
- Josh V Vermaas
- Center for Biophysics and Computational Biology, Department Biochemistry, College of Medicine, and Beckman Institute for Advanced Science and Technology, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States
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12
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Classical protein kinases C are regulated by concerted interaction with lipids: the importance of phosphatidylinositol-4,5-bisphosphate. Biophys Rev 2013; 6:3-14. [PMID: 28509956 DOI: 10.1007/s12551-013-0125-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2013] [Accepted: 10/03/2013] [Indexed: 10/26/2022] Open
Abstract
Classical protein kinase C (PKC) enzymes are known to be important factors in cell physiology both in terms of health and disease. They are activated by triggering signals that induce their translocation to membranes. The consensus view is that several secondary messengers are involved in this activation, such as cytosolic Ca2+ and diacylglycerol. Cytosolic Ca2+ bridges the C2 domain to anionic phospholipids as phosphatidylserine in the membrane, and diacylglycerol binds to the C1 domain. Both diacylglycerol and the increase in Ca2+ concentration are assumed to arise from the extracellular signal that triggers the hydrolysis of phosphatidylinositol-4,5-bisphosphate. However, results obtained during the last decade indicate that this phosphoinositide itself is also responsible for modulating classical PKC activity and its localization in the plasma membrane.
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