1
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Feng S, Aplin C, Nguyen TTT, Milano SK, Cerione RA. Filament formation drives catalysis by glutaminase enzymes important in cancer progression. Nat Commun 2024; 15:1971. [PMID: 38438397 PMCID: PMC10912226 DOI: 10.1038/s41467-024-46351-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Accepted: 02/22/2024] [Indexed: 03/06/2024] Open
Abstract
The glutaminase enzymes GAC and GLS2 catalyze the hydrolysis of glutamine to glutamate, satisfying the 'glutamine addiction' of cancer cells. They are the targets of anti-cancer drugs; however, their mechanisms of activation and catalytic activity have been unclear. Here we demonstrate that the ability of GAC and GLS2 to form filaments is directly coupled to their catalytic activity and present their cryo-EM structures which provide a view of the conformational states essential for catalysis. Filament formation guides an 'activation loop' to assume a specific conformation that works together with a 'lid' to close over the active site and position glutamine for nucleophilic attack by an essential serine. Our findings highlight how ankyrin repeats on GLS2 regulate enzymatic activity, while allosteric activators stabilize, and clinically relevant inhibitors block, filament formation that enables glutaminases to catalyze glutaminolysis and support cancer progression.
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Affiliation(s)
- Shi Feng
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Thuy-Tien T Nguyen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Shawn K Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY, 14853, USA.
- Department of Molecular Medicine, Cornell University, Ithaca, NY, 14853, USA.
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2
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Aplin C, Zielinski KA, Pabit S, Ogunribido D, Katt WP, Pollack L, Cerione RA, Milano SK. Defining the conformational states that enable transglutaminase 2 to promote cancer cell survival versus cell death. bioRxiv 2024:2024.02.04.578794. [PMID: 38370687 PMCID: PMC10871292 DOI: 10.1101/2024.02.04.578794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/20/2024]
Abstract
Transglutaminase 2 (TG2) is a GTP-binding/protein-crosslinking enzyme that has been investigated as a therapeutic target for Celiac disease, neurological disorders, and aggressive cancers. TG2 has been suggested to adopt two conformational states that regulate its functions: a GTP-bound, closed conformation, and a calcium-bound, crosslinking-active open conformation. TG2 mutants that constitutively adopt an open conformation are cytotoxic to cancer cells. Thus, small molecules that maintain the open conformation of TG2 could offer a new therapeutic strategy. Here, we investigate TG2, using static and time-resolved small-angle X-ray scattering (SAXS) and single-particle cryoelectron microscopy (cryo-EM), to determine the conformational states responsible for conferring its biological effects. We also describe a newly developed TG2 inhibitor, LM11, that potently kills glioblastoma cells and use SAXS to investigate how LM11 affects the conformational states of TG2. Using SAXS and cryo-EM, we show that guanine nucleotide-bound TG2 adopts a monomeric closed conformation while calcium-bound TG2 assumes an open conformational state that can form higher order oligomers. SAXS analysis also suggests how a TG2 mutant that constitutively adopts the open state binds nucleotides through an alternative mechanism to wildtype TG2. Furthermore, we use time-resolved SAXS to show that LM11 increases the ability of calcium to drive TG2 to an open conformation, which is not reversible by guanine nucleotides and is cytotoxic to cancer cells. Taken together, our findings demonstrate that the conformational dynamics of TG2 are more complex than previously suggested and highlight how conformational stabilization of TG2 by LM11 maintains TG2 in a cytotoxic conformational state.
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Affiliation(s)
- Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853
| | - Kara A. Zielinski
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853
| | - Suzette Pabit
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853
| | - Deborah Ogunribido
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
| | - William P. Katt
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853
| | - Lois Pollack
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853
| | - Richard A. Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853
| | - Shawn K. Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853
- Department of Molecular Medicine, Cornell University, Ithaca, NY 14853
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3
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Feng S, Aplin C, Nguyen TTT, Milano SK, Cerione RA. Filament formation drives catalysis by glutaminase enzymes important in cancer progression. bioRxiv 2023:2023.02.16.528860. [PMID: 36824706 PMCID: PMC9949068 DOI: 10.1101/2023.02.16.528860] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/18/2023]
Abstract
The glutaminase enzymes GAC and GLS2 catalyze the hydrolysis of glutamine to glutamate, satisfying the 'glutamine addiction' of cancer cells. They are the targets of anti-cancer drugs; however, their mechanisms of activation and catalytic activity have been unclear. Here we demonstrate that the ability of GAC and GLS2 to form filaments is directly coupled to their catalytic activity and present their cryo-EM structures which provide an unprecedented view of the conformational states essential for catalysis. Filament formation guides an 'activation loop' to assume a specific conformation that works together with a 'lid' to close over the active site and position glutamine for nucleophilic attack by an essential serine. Our findings highlight how ankyrin repeats on GLS2 regulate enzymatic activity, while allosteric activators stabilize, and clinically relevant inhibitors block, filament formation that enables glutaminases to catalyze glutaminolysis and support cancer progression.
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Affiliation(s)
- Shi Feng
- Department of Chemistry and Chemical Biology, Cornell University,
Ithaca, New York, 14853
| | - Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University,
Ithaca, New York, 14853
| | - Thuy-Tien T. Nguyen
- Department of Chemistry and Chemical Biology, Cornell University,
Ithaca, New York, 14853
| | - Shawn K. Milano
- Department of Chemistry and Chemical Biology, Cornell University,
Ithaca, New York, 14853
| | - Richard A. Cerione
- Department of Chemistry and Chemical Biology, Cornell University,
Ithaca, New York, 14853
- Department of Molecular Medicine, Cornell University, Ithaca, New
York, 14853
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4
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Zielinski KA, Katz AM, Calvey GD, Pabit SA, Milano SK, Aplin C, San Emeterio J, Cerione RA, Pollack L. Chaotic advection mixer for capturing transient states of diverse biological macromolecular systems with time-resolved small-angle X-ray scattering. IUCrJ 2023; 10:363-375. [PMID: 37144817 PMCID: PMC10161774 DOI: 10.1107/s2052252523003482] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Accepted: 04/17/2023] [Indexed: 05/06/2023]
Abstract
Advances in time-resolved structural techniques, mainly in macromolecular crystallography and small-angle X-ray scattering (SAXS), allow for a detailed view of the dynamics of biological macromolecules and reactions between binding partners. Of particular promise, are mix-and-inject techniques, which offer a wide range of experimental possibility as microfluidic mixers are used to rapidly combine two species just prior to data collection. Most mix-and-inject approaches rely on diffusive mixers, which have been effectively used within crystallography and SAXS for a variety of systems, but their success is dependent on a specific set of conditions to facilitate fast diffusion for mixing. The use of a new chaotic advection mixer designed for microfluidic applications helps to further broaden the types of systems compatible with time-resolved mixing experiments. The chaotic advection mixer can create ultra-thin, alternating layers of liquid, enabling faster diffusion so that even more slowly diffusing molecules, like proteins or nucleic acids, can achieve fast mixing on timescales relevant to biological reactions. This mixer was first used in UV-vis absorbance and SAXS experiments with systems of a variety of molecular weights, and thus diffusion speeds. Careful effort was also dedicated to making a loop-loading sample-delivery system that consumes as little sample as possible, enabling the study of precious, laboratory-purified samples. The combination of the versatile mixer with low sample consumption opens the door to many new applications for mix-and-inject studies.
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Affiliation(s)
- Kara A. Zielinski
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York USA
| | - Andrea M. Katz
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York USA
| | - George D. Calvey
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York USA
| | - Suzette A. Pabit
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York USA
| | - Shawn K. Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York USA
| | - Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York USA
| | - Josue San Emeterio
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York USA
| | - Richard A. Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York USA
- Department of Molecular Medicine, Cornell University, Ithaca, New York USA
| | - Lois Pollack
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York USA
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5
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Milano SK, Szebenyi MD, Cerione ARA. Serial Room Temperature Crystal Loading, Data Collection, and Data Processing of Human Glutaminase C in Complex with Allosteric Inhibitors. Bio Protoc 2022; 12:e4509. [PMID: 36248609 PMCID: PMC9516223 DOI: 10.21769/bioprotoc.4509] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2022] [Revised: 06/30/2022] [Accepted: 07/27/2022] [Indexed: 12/29/2022] Open
Abstract
Cancer cells often overexpress glutaminase enzymes, in particular glutaminase C (GAC). GAC resides in the mitochondria and catalyzes the hydrolysis of glutamine to glutamate. High levels of GAC have been observed in aggressive cancers and the inhibition of its enzymatic activity has been shown to reduce their growth and survival. Numerous GAC inhibitors have been reported, the most heavily investigated being a class of compounds derived from the small molecule BPTES (bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide). X-ray structure determination under cryo-cooled conditions showed that the binding contacts for the different inhibitors were largely conserved despite their varying potencies. However, using the emerging technique serial room temperature crystallography, we were able to observe clear differences between the binding conformations of inhibitors. Here, we describe a step-by-step protocol for crystal handling, data collection, and data processing of GAC in complex with allosteric inhibitors using serial room temperature crystallography. Graphical abstract: Figure 1. Workflow for serial room temperature crystallography. Diagram showing the processing and scaling routine for crystals analyzed using serial room temperature crystallography.
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Affiliation(s)
- Shawn K. Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
,
*For correspondence:
;
| | - Marian D. Szebenyi
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - And Richard A. Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
,
Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, United States
,
*For correspondence:
;
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Abstract
Structure-based drug design (SBDD) is a prominent method in rational drug development and has traditionally benefitted from the atomic models of protein targets obtained using X-ray crystallography at cryogenic temperatures. In this perspective, we highlight recent advances in the development of structural techniques that are capable of probing dynamic information about protein targets. First, we discuss advances in the field of X-ray crystallography including serial room-temperature crystallography as a method for obtaining high-resolution conformational dynamics of protein-inhibitor complexes. Next, we look at cryogenic electron microscopy (cryoEM), another high-resolution technique that has recently been used to study proteins and protein complexes that are too difficult to crystallize. Finally, we present small-angle X-ray scattering (SAXS) as a potential high-throughput screening tool to identify inhibitors that target protein complexes and protein oligomerization.
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Affiliation(s)
- Cody Aplin
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Shawn K Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Kara A Zielinski
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States
| | - Lois Pollack
- School of Applied and Engineering Physics, Cornell University, Ithaca, New York 14853, United States
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States.,Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, United States
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7
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Milano SK, Huang Q, Nguyen TTT, Ramachandran S, Finke A, Kriksunov I, Schuller D, Szebenyi M, Arenholz E, McDermott LA, Sukumar N, Cerione RA, Katt WP. New insights into the molecular mechanisms of glutaminase C inhibitors in cancer cells using serial room temperature crystallography. J Biol Chem 2021; 298:101535. [PMID: 34954143 PMCID: PMC8784640 DOI: 10.1016/j.jbc.2021.101535] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Revised: 12/19/2021] [Accepted: 12/21/2021] [Indexed: 12/24/2022] Open
Abstract
Cancer cells frequently exhibit uncoupling of the glycolytic pathway from the TCA cycle (i.e. the "Warburg effect"), and as a result, often become dependent on their ability to increase glutamine catabolism. The mitochondrial enzyme Glutaminase C (GAC) helps to satisfy this 'glutamine addiction' of cancer cells by catalyzing the hydrolysis of glutamine to glutamate, which is then converted to the TCA-cycle intermediate α-ketoglutarate. This makes GAC an intriguing drug target, and spurred the molecules derived from bis-2-(5-phenylacetamido-1,3,4-thiadiazol-2-yl)ethyl sulfide (the so-called BPTES-class of allosteric GAC inhibitors), including CB-839, which is currently in clinal trials. However, none of the drugs targeting GAC are yet approved for cancer treatment and their mechanism of action is not well understood. Here, we shed new light on the underlying basis for the differential potencies exhibited by members of the BPTES/CB-839 family of compounds, which could not previously be explained with standard cryo-cooled X-ray crystal structures of GAC bound to CB-839 or its analogs. Using an emerging technique known as serial room temperature crystallography, we were able to observe clear differences between the binding conformations of inhibitors with significantly different potencies. We also developed a computational model to further elucidate the molecular basis of differential inhibitor potency. We then corroborated the results from our modeling efforts using recently established fluorescence assays that directly read out inhibitor binding to GAC. Together, these findings should aid in future design of more potent GAC inhibitors with better clinical outlook.
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Affiliation(s)
- Shawn K Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Qingqiu Huang
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - Thuy-Tien T Nguyen
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Sekar Ramachandran
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States
| | - Aaron Finke
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - Irina Kriksunov
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - David Schuller
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - Marian Szebenyi
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - Elke Arenholz
- Cornell High Energy Synchrotron Source (CHESS), Cornell University, Ithaca, New York 14853, United States
| | - Lee A McDermott
- Department of Pharmaceutical Sciences, Pittsburgh, Pennsylvania 15261, United States; Drug Discovery Institute, University of Pittsburgh, Pittsburgh, Pennsylvania 15261, United States
| | - N Sukumar
- Department of Chemistry and Center for Informatics, Shiv Nadar University, India
| | - Richard A Cerione
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853, United States; Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, United States.
| | - William P Katt
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, United States
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8
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Illava G, Jayne R, Finke AD, Closs D, Zeng W, Milano SK, Huang Q, Kriksunov I, Sidorenko P, Wise FW, Zipfel WR, Apker BA, Thorne RE. Integrated sample-handling and mounting system for fixed-target serial synchrotron crystallography. Acta Crystallogr D Struct Biol 2021; 77:628-644. [PMID: 33950019 PMCID: PMC8098472 DOI: 10.1107/s2059798321001868] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/28/2020] [Accepted: 02/15/2021] [Indexed: 11/15/2022] Open
Abstract
Serial synchrotron crystallography (SSX) is enabling the efficient use of small crystals for structure-function studies of biomolecules and for drug discovery. An integrated SSX system has been developed comprising ultralow background-scatter sample holders suitable for room and cryogenic temperature crystallographic data collection, a sample-loading station and a humid `gloveless' glovebox. The sample holders incorporate thin-film supports with a variety of designs optimized for different crystal-loading challenges. These holders facilitate the dispersion of crystals and the removal of excess liquid, can be cooled at extremely high rates, generate little background scatter, allow data collection over >90° of oscillation without obstruction or the risk of generating saturating Bragg peaks, are compatible with existing infrastructure for high-throughput cryocrystallography and are reusable. The sample-loading station allows sample preparation and loading onto the support film, the application of time-varying suction for optimal removal of excess liquid, crystal repositioning and cryoprotection, and the application of sealing films for room-temperature data collection, all in a controlled-humidity environment. The humid glovebox allows microscope observation of the sample-loading station and crystallization trays while maintaining near-saturating humidities that further minimize the risks of sample dehydration and damage, and maximize working times. This integrated system addresses common problems in obtaining properly dispersed, properly hydrated and isomorphous microcrystals for fixed-orientation and oscillation data collection. Its ease of use, flexibility and optimized performance make it attractive not just for SSX but also for single-crystal and few-crystal data collection. Fundamental concepts that are important in achieving desired crystal distributions on a sample holder via time-varying suction-induced liquid flows are also discussed.
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Affiliation(s)
- Gabrielle Illava
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | | | | | - David Closs
- MiTeGen LLC, PO Box 3867, Ithaca, NY 14850, USA
| | - Wenjie Zeng
- Department of Molecular Biology and Genetics, Weill Institute for Cell and Molecular Biology, Cornell University, Ithaca, NY 14853, USA
| | - Shawn K. Milano
- Department of Chemistry and Chemical Biology, Cornell University, Ithaca, NY 14853, USA
| | | | | | - Pavel Sidorenko
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Frank W. Wise
- School of Applied and Engineering Physics, Cornell University, Ithaca, NY 14853, USA
| | - Warren R. Zipfel
- Meinig School of Biomedical Engineering, Cornell University, Ithaca, NY 14853, USA
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Lee S, Yang YA, Milano SK, Nguyen T, Ahn C, Sim JH, Thompson AJ, Hillpot EC, Yoo G, Paulson JC, Song J. Salmonella Typhoid Toxin PltB Subunit and Its Non-typhoidal Salmonella Ortholog Confer Differential Host Adaptation and Virulence. Cell Host Microbe 2020; 27:937-949.e6. [PMID: 32396840 DOI: 10.1016/j.chom.2020.04.005] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2019] [Revised: 02/18/2020] [Accepted: 04/03/2020] [Indexed: 01/19/2023]
Abstract
Typhoidal and non-typhoidal Salmonelleae (NTS) cause typhoid fever and gastroenteritis, respectively, in humans. Salmonella typhoid toxin contributes to typhoid disease progression and chronic infection, but little is known about the role of its NTS ortholog. We found that typhoid toxin and its NTS ortholog induce different clinical presentations. The PltB subunit of each toxin exhibits different glycan-binding preferences that correlate with glycan expression profiles of host cells targeted by each bacterium at the primary infection or intoxication sites. Through co-crystal structures of PltB subunits bound to specific glycan receptor moieties, we show that they induce markedly different glycan-binding preferences and virulence outcomes. Furthermore, immunization with the NTS S. Javiana or its toxin offers cross-reactive protection against lethal-dose typhoid toxin challenge. Cumulatively, these results offer insights into the evolution of host adaptations in Salmonella AB toxins, their cell and tissue tropisms, and the design for improved typhoid vaccines and therapeutics.
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Affiliation(s)
- Sohyoung Lee
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Yi-An Yang
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Shawn K Milano
- Department of Molecular Medicine, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Tri Nguyen
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Changhwan Ahn
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Ji Hyun Sim
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Andrew J Thompson
- Department of Molecular Medicine, the Scripps Research Institute, La Jolla, CA 92121, USA
| | - Eric C Hillpot
- Department of Molecular Medicine, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - Gyeongshik Yoo
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA
| | - James C Paulson
- Department of Molecular Medicine, the Scripps Research Institute, La Jolla, CA 92121, USA
| | - Jeongmin Song
- Department of Microbiology and Immunology, Cornell University College of Veterinary Medicine, Ithaca, NY 14853, USA.
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10
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Milano SK, Wang C, Erickson JW, Cerione RA, Ramachandran S. Gain-of-function screen of α-transducin identifies an essential phenylalanine residue necessary for full effector activation. J Biol Chem 2018; 293:17941-17952. [PMID: 30266806 DOI: 10.1074/jbc.ra118.003746] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 09/21/2018] [Indexed: 11/06/2022] Open
Abstract
Two regions on the α subunits of heterotrimeric GTP-binding proteins (G-proteins), the Switch II/α2 helix (which changes conformation upon GDP-GTP exchange) and the α3 helix, have been shown to contain the binding sites for their effector proteins. However, how the binding of Gα subunits to their effector proteins is translated into the stimulation of effector activity is still poorly understood. Here, we took advantage of a reconstituted rhodopsin-coupled phototransduction system to address this question and identified a distinct surface and an essential residue on the α subunit of the G-protein transducin (αT) that is necessary to fully activate its effector enzyme, the cGMP phosphodiesterase (PDE). We started with a chimeric G-protein α subunit (αT*) comprising residues mainly from αT and a short stretch of residues from the Gi1 α subunit (αi1), which only weakly stimulates PDE activity. We then reinstated the αT residues by systematically replacing the corresponding αi1 residues within αT* with the aim of fully restoring PDE stimulatory activity. These experiments revealed that the αG/α4 loop and a phenylalanine residue at position 283 are essential for conferring the αT* subunit with full PDE stimulatory capability. We further demonstrated that this same region and amino acid within the α subunit of the Gs protein (αs) are necessary for full adenylyl cyclase activation. These findings highlight the importance of the αG/α4 loop and of an essential phenylalanine residue within this region on Gα subunits αT and αs as being pivotal for their selective and optimal stimulation of effector activity.
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Affiliation(s)
- Shawn K Milano
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301
| | - Chenyue Wang
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301
| | - Jon W Erickson
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301
| | - Richard A Cerione
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301; Department of Molecular Medicine, Cornell University, Ithaca, New York 14853-6401.
| | - Sekar Ramachandran
- From the Department of Chemistry and Chemical Biology, Cornell University, Ithaca, New York 14853-1301
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11
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Milano SK, Kwon W, Pereira R, Antonyak MA, Cerione RA. Characterization of a novel activated Ran GTPase mutant and its ability to induce cellular transformation. J Biol Chem 2012; 287:24955-66. [PMID: 22679017 DOI: 10.1074/jbc.m111.306514] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Ran (Ras-related nuclear) protein, a member of the Ras superfamily of GTPases, is best known for its roles in nucleocytoplasmic transport, mitotic spindle fiber assembly, and nuclear envelope formation. Recently, we have shown that the overexpression of Ran in fibroblasts induces cellular transformation and tumor formation in mice (Ly, T. K., Wang, J., Pereira, R., Rojas, K. S., Peng, X., Feng, Q., Cerione, R. A., and Wilson, K. F. (2010) J. Biol. Chem. 285, 5815-5826). Here, we describe a novel activated Ran mutant, Ran(K152A), which is capable of an increased rate of GDP-GTP exchange and an accelerated GTP binding/GTP hydrolytic cycle compared with wild-type Ran. We show that its expression in NIH-3T3 fibroblasts induces anchorage-independent growth and stimulates cell invasion, as well as activates signaling pathways that lead to extracellular regulated kinase (ERK) activity. Furthermore, Ran(K152A) expression in the human mammary SKBR3 adenocarcinoma cell line gives rise to an enhanced transformed phenotype and causes a robust stimulation of both ERK and the N-terminal c-Jun kinase (JNK). Microarray analysis reveals that the expression of the gene encoding SMOC-2 (secreted modular calcium-binding protein-2), which has been shown to synergize with different growth factors, is increased by at least 50-fold in cells stably expressing Ran(K152A) compared with cells expressing control vector. Knocking down SMOC-2 expression greatly reduces the ability of Ran(K152A) to stimulate anchorage-independent growth in NIH-3T3 cells and in SKBR3 cells and also inhibits cell invasion in fibroblasts. Collectively, our findings highlight a novel connection between the hyper-activation of the small GTPase Ran and the matricellular protein SMOC-2 that has important consequences for oncogenic transformation.
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Affiliation(s)
- Shawn K Milano
- Department of Molecular Medicine, Cornell University, Ithaca, New York 14853, USA
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Abstract
To ensure that extracellular stimuli are translated into intracellular signals of appropriate magnitude and specificity, most signaling cascades are tightly regulated. One of the major mechanisms involved in the regulation of G protein-coupled receptors (GPCRs) involves their endocytic trafficking. GPCR endocytic trafficking entails the targeting of receptors to discrete endocytic sites at the plasma membrane, followed by receptor internalization and intracellular sorting. This regulates the level of cell surface receptors, the sorting of receptors to degradative or recycling pathways, and in some cases the specific signaling pathways. In this chapter we discuss the mechanisms that regulate receptor endocytic trafficking, emphasizing the role of GPCR kinases (GRKs) and arrestins in this process.
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Affiliation(s)
- Catherine A C Moore
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
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13
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Milano SK, Kim YM, Stefano FP, Benovic JL, Brenner C. Nonvisual arrestin oligomerization and cellular localization are regulated by inositol hexakisphosphate binding. J Biol Chem 2006; 281:9812-23. [PMID: 16439357 DOI: 10.1074/jbc.m512703200] [Citation(s) in RCA: 122] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Interactions between arrestins and phosphoinositides have been reported to regulate multiple membrane-associated signaling and trafficking events including clathrin-mediated endocytosis and light adaptation in Drosophila. Arrestins have been proposed to have nuclear and cytosolic functions as well, although the ligand dependence of these functions has not been investigated. Here we characterize the structural, molecular, and cellular interactions between arrestin-2 and inositol hexakisphosphate (inositol 1,2,3,4,5,6-hexakisphosphate (IP(6))). The crystal structure of the arrestin-2.IP(6) complex was solved to 2.9 A with crystal lattice contacts suggesting two sites on a protein monomer mediating IP(6) binding. Mutagenesis coupled to isothermal titration calorimetry and tritiated IP(6) binding assays confirmed two-site binding with a low affinity IP(6)-binding site in the N-domain and a high affinity site in the C-domain. Native gel electrophoresis, gel filtration, and analytical ultracentrifugation demonstrated the ability of IP(6) to promote arrestin-2 oligomerization via the two crystallographically defined ligand-binding locations. In addition, analysis in mammalian cells revealed that arrestin-2 not only undergoes homo-oligomerization, but it can also hetero-oligomerize with arrestin-3 in a manner that depends on IP(6)-binding sites. Mutation of either IP(6)-binding site in arrestin-2 disrupted oligomerization while interactions with known binding partners including clathrin, AP-2, and ERK2 were maintained. Subcellular localization studies showed that arrestin-2 oligomers are primarily cytoplasmic, whereas arrestin-2 monomers displayed increased nuclear localization. Thus, by promoting cytosolic oligomerization, IP(6) binding is proposed to be a negative regulator of interactions of arrestin with plasma membrane and nuclear signaling proteins.
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Affiliation(s)
- Shawn K Milano
- Department of Biochemistry and Molecular Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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14
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Abstract
Arrestin binding to activated, phosphorylated G protein-coupled receptors (GPCRs) represents a critical step in regulation of light- and hormone-dependent signaling. Nonvisual arrestins, such as arrestin-2, interact with multiple proteins for the purpose of propagating and terminating signaling events. Using a combination of X-ray crystallography, molecular modeling, mutagenesis, and binding analysis, we reveal structural features of arrestin-2 that may enable simultaneous binding to phosphorylated receptor, SH3 domains, phosphoinositides, and beta-adaptin. The structure of full-length arrestin-2 thus provides a uniquely oriented scaffold for assembly of multiple, diverse molecules involved in GPCR signal transduction.
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Affiliation(s)
- Shawn K Milano
- Structural Biology and Bioinformatics Program, Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
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15
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Slater SJ, Seiz JL, Stagliano BA, Cook AC, Milano SK, Ho C, Stubbs CD. Low- and high-affinity phorbol ester and diglyceride interactions with protein kinase C: 1-O-alkyl-2-acyl-sn-glycerol enhances phorbol ester- and diacylglycerol-induced activity but alone does not induce activity. Biochemistry 2001; 40:6085-92. [PMID: 11352745 DOI: 10.1021/bi001002z] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Phorbol ester-induced conventional protein kinase C (PKCalpha, -betaIota/IotaIota, and -gamma) isozyme activities are potentiated by 1,2-diacyl-sn-glycerol. This has been attributed to a "cooperative" interaction of the two activators with two discrete sites termed the low- and high-affinity phorbol ester binding sites, respectively [Slater, S. J., Milano, S. K., Stagliano, B. A., Gergich, K. J., Ho, C., Mazurek, A., Taddeo, F. J., Kelly, M. B., Yeager, M. D., and Stubbs, C. D. (1999) Biochemistry 38, 3804-3815]. Here, we report that the 1-O-alkyl ether diglyceride, 1-O-hexadecyl-2-acetyl-sn-glycerol (HAG), like its 1,2-diacyl counterpart, 1-oleoyl-2-acetyl-sn-glycerol (OAG), also potentiated PKCalpha, -betaI/II, and -gamma activities induced by the phorbol ester 4beta-12-O-tetradecanoylphorbol-13-acetate (TPA). Similar to OAG, HAG was found to bind to the low-affinity phorbol ester binding site and to enhance high-affinity phorbol ester binding, and to decrease the level of Ca(2+) required for phorbol ester-induced activity, while being without effect on the Ca(2+) dependence of membrane association. Thus, similar to OAG, HAG may also potentiate phorbol ester-induced activity by interacting with the low-affinity phorbol ester binding site, leading to a reduced level of Ca(2+) required for the activating conformational change. However, HAG was found not to behave like a 1,2-diacyl-sn-glycerol in that alone it did not induce PKC activity, and also in that it enhanced OAG-induced activity. The results reveal HAG to be a member of a new class of "nonactivating" compounds that modulate PKC activity by interacting with the low-affinity phorbol ester binding site.
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Affiliation(s)
- S J Slater
- Department of Pathology, Cell Biology, and Anatomy, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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16
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Slater SJ, Stagliano BA, Seiz JL, Curry JP, Milano SK, Gergich KJ, Stubbs CD. Effects of ethanol on protein kinase C activity induced by filamentous actin. Biochim Biophys Acta 2001; 1544:207-16. [PMID: 11341930 DOI: 10.1016/s0167-4838(00)00222-3] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Protein kinase C (PKC) can be activated by interaction with filamentous actin (F-actin) in the absence of membrane lipids (S.J. Slater, S.K. Milano, B.A. Stagliano, K.J. Gergich, J.P. Curry, F.J. Taddeo and C.D. Stubbs, Biochemistry 39 (2000) 271-280). Here, the effects of ethanol on the F-actin-induced activities of a panel of PKC isoforms consisting of 'conventional' (cPKC) alpha, betaI, gamma, 'novel' (nPKC) delta, epsilon and 'atypical' (aPKC) zeta were investigated using purified PKC and F-actin. Ethanol was found to inhibit the Ca2+- and phorbol ester-dependent activities of cPKCalpha and betaI, and the Ca2+- and phorbol ester-independent activity of cPKCgamma, whereas the activities of nPKCdelta, epsilon and aPKCzeta were unaffected. Although the activities of cPKCalpha and betaI induced by saturating levels of phorbol ester were inhibited by ethanol, the binding of these isozymes to F-actin was unaffected within the same phorbol ester concentration range. Conversely, within submaximal levels of phorbol ester, cPKCalpha and betaI activities were unaffected by ethanol whereas binding to F-actin was inhibited. The potency of the inhibition of F-actin-induced cPKCbetaI activity increased with n-alkanol chain length up to n-hexanol, after which it declined. The results indicate that PKC activities associated with F-actin, and therefore cellular processes involving the actin cytoskeleton, are potential targets for ethanol action. The effects of ethanol on these processes may differ according to the particular regulating PKC isoform, its intracellular localization and the presence of activators and cofactors.
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Affiliation(s)
- S J Slater
- Department of Anatomy, Pathology, and Cell Biology, Room 271 JAH, Thomas Jefferson University, Philadelphia, PA 19107, USA
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17
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Slater SJ, Milano SK, Stagliano BA, Gergich KJ, Curry JP, Taddeo FJ, Stubbs CD. Interaction of protein kinase C with filamentous actin: isozyme specificity resulting from divergent phorbol ester and calcium dependencies. Biochemistry 2000; 39:271-80. [PMID: 10630986 DOI: 10.1021/bi9916527] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The mechanism of activation of protein kinase C isoforms by filamentous actin (F-actin) was investigated with respect to isozyme specificity and phorbol ester and Ca(2+) dependencies. It was found that the "conventional" (cPKC), alpha, betaI, betaII, and gamma, "novel" (nPKC) delta and epsilon, and "atypical" (aPKC) zeta isoforms were each activated by F-actin with varying potencies. The level of activity along with the affinity for binding to F-actin was further potentiated by the phorbol ester 4beta-12-O-tetradecanoylphorbol 13-acetate (TPA), the potency of which again varied for each isoform. By contrast to the other cPKC isoforms, the level of cPKC-gamma activity was unaffected by TPA, as was also the case for aPKC-zeta. It was found that whereas in the absence of F-actin the soluble form of cPKC-betaI contained two phorbol ester binding sites of low and high affinity, respectively, as previously reported for cPKC-alpha [Slater et al. (1998) J. Biol. Chem. 273, 23160-23168], the F-actin-bound form of the isozyme contained only a single site of relatively low affinity. The level of TPA required to induce cPKC-alpha, -betaI, and -betaII activity and the binding of these isozymes to F-actin was reduced in the presence of Ca(2+). By contrast, the activity of cPKC-gamma was unaffected by Ca(2+), as were the activities of nPKC-delta and -epsilon and aPKC-zeta, as expected. Thus, the interaction with F-actin appears to be a general property of each of the seven PKC isozymes tested. However, isoform specificity may, in part, be directed by differences in the phorbol ester and Ca(2+) dependences, which, with the notable exception of cPKC-gamma, appear to resemble those observed for the activation of each isoform by membrane association. The observation that cPKC isoforms may translocate to F-actin as well as the membrane as a response to an elevation of Ca(2+) levels may allow for the functional coupling of fluctuations of intracellular Ca(2+) levels through cPKC to F-actin cytoskeleton-mediated processes.
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Affiliation(s)
- S J Slater
- Department of Pathology, Cell Biology and Anatomy, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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18
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Slater SJ, Milano SK, Stagliano BA, Gergich KJ, Ho C, Mazurek A, Taddeo FJ, Kelly MB, Yeager MD, Stubbs CD. Synergistic activation of protein kinase Calpha, -betaI, and -gamma isoforms induced by diacylglycerol and phorbol ester: roles of membrane association and activating conformational changes. Biochemistry 1999; 38:3804-15. [PMID: 10090770 DOI: 10.1021/bi982778r] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Protein kinase Calpha (PKCalpha) has been shown to contain two discrete activator sites with differing binding affinities for phorbol esters and diacylglycerols. The interaction of diacylglycerol with a low-affinity phorbol ester binding site leads to enhanced high-affinity phorbol ester binding and to a potentiated level of activity [Slater, S. J., Ho, C., Kelly, M. B., Larkin, J. D. , Taddeo, F. J., Yeager, M. D., and Stubbs, C. D. (1996) J. Biol. Chem. 271, 4627-4631]. In this study, the mechanism of this enhancement of activity was examined with respect to the Ca2+ dependences of membrane association and accompanying conformational changes that lead to activation. The association of PKCalpha with membranes containing 12-O-tetradecanoylphorbol 13-acetate (TPA) or 1, 2-dioleoylglycerol (DAG), determined from tryptophan to dansyl-PE resonance energy transfer (RET) measurements, was found to occur at relatively low Ca2+ levels (</=1 microM). However, PKCalpha was found to be inactive even though membrane association was complete at these Ca2+ levels and further titration of Ca2+ to a concentration of approximately 100 microM was required for activation. This increase in Ca2+ concentration also led to a further increase in RET, which was due to a Ca2+-induced activating conformational change, as verified by an accompanying increase in the PKCalpha tryptophan fluorescence anisotropy. Coaddition of DAG and TPA resulted in a reduction in the Ca2+ levels required for both the conformational change and enzyme activation. Also, it was found that incubation of the enzyme with TPA alone resulted in a time-dependent increase in the Ca2+-independent PKCalpha activity, the rate and extent of which was further enhanced upon coaddition with DAG. Tauhe results suggest that the enhanced level of activity induced by coaddition of DAG and TPA involves both Ca2+-dependent and Ca2+-independent activating conformational changes which result in active conformers of PKCalpha distinct from those formed by interaction with either activator separately.
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Affiliation(s)
- S J Slater
- Department of Anatomy, Pathology, and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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Slater SJ, Taddeo FJ, Mazurek A, Stagliano BA, Milano SK, Kelly MB, Ho C, Stubbs CD. Inhibition of membrane lipid-independent protein kinase Calpha activity by phorbol esters, diacylglycerols, and bryostatin-1. J Biol Chem 1998; 273:23160-8. [PMID: 9722545 DOI: 10.1074/jbc.273.36.23160] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The activity of membrane-associated protein kinase C (PKC) has previously been shown to be regulated by two discrete high and low affinity binding regions for diacylglycerols and phorbol esters (Slater, S. J., Ho, C., Kelly, M. B., Larkin, J. D., Taddeo, F. J., Yeager, M. D., and Stubbs, C. D. (1996) J. Biol. Chem. 271, 4627-4631). PKC is also known to interact with both cytoskeletal and nuclear proteins; however, less is known concerning the mode of activation of this non-membrane form of PKC. By using the fluorescent phorbol ester, sapintoxin D (SAPD), PKCalpha, alone, was found to possess both low and high affinity phorbol ester-binding sites, showing that interaction with these sites does not require association with the membrane. Importantly, a fusion protein containing the isolated C1A/C1B (C1) domain of PKCalpha also bound SAPD with low and high affinity, indicating that the sites may be confined to this domain rather than residing elsewhere on the enzyme molecule. Both high and low affinity interactions with native PKCalpha were enhanced by protamine sulfate, which activates the enzyme without requiring Ca2+ or membrane lipids. However, this "non-membrane" PKC activity was inhibited by the phorbol ester 4beta-12-O-tetradecanoylphorbol-13-acetate (TPA) and also by the fluorescent analog, SAPD, opposite to its effect on membrane-associated PKCalpha. Bryostatin-1 and the soluble diacylglycerol, 1-oleoyl-2-acetylglycerol, both potent activators of membrane-associated PKC, also competed for both low and high affinity SAPD binding and inhibited protamine sulfate-induced activity. Furthermore, the inactive phorbol ester analog 4alpha-TPA (4alpha-12-O-tetradecanoylphorbol-13-acetate) also inhibited non-membrane-associated PKC. In keeping with these observations, although TPA could displace high affinity SAPD binding from both forms of the enzyme, 4alpha-TPA was only effective at displacing high affinity SAPD binding from non-membrane-associated PKC. 4alpha-TPA also displaced SAPD from the isolated C1 domain. These results show that although high and low affinity phorbol ester-binding sites are found on non-membrane-associated PKC, the phorbol ester binding properties change significantly upon association with membranes.
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Affiliation(s)
- S J Slater
- Department of Pathology and Cell Biology, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA
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