1
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Su Q, Zhang J, Lin W, Zhang JF, Newton AC, Mehta S, Yang J, Zhang J. Sensitive Fluorescent Biosensor Reveals Differential Subcellular Regulation of PKC. bioRxiv 2024:2024.03.29.587373. [PMID: 38586003 PMCID: PMC10996667 DOI: 10.1101/2024.03.29.587373] [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: 04/09/2024]
Abstract
The protein kinase C (PKC) family of serine/threonine kinases, which consist of three distinctly regulated subfamilies, have long been established as critical for a variety of cellular functions. However, how PKC enzymes are regulated at different subcellular locations, particularly at emerging signaling hubs such as the ER, lysosome, and Par signaling complexes, is unclear. Here, we present a sensitive Excitation Ratiometric (ExRai) C Kinase Activity Reporter (ExRai-CKAR2) that enables the detection of minute changes in subcellular PKC activity. Using ExRai-CKAR2 in conjunction with an enhanced diacylglycerol (DAG) biosensor capable of detecting intracellular DAG dynamics, we uncover the differential regulation of PKC isoforms at distinct subcellular locations. We find that G-protein coupled receptor (GPCR) stimulation triggers sustained PKC activity at the ER and lysosomes, primarily mediated by Ca2+ sensitive conventional PKC (cPKC) and novel PKC (nPKC), respectively, with nPKC showing high basal activity due to elevated basal DAG levels on lysosome membranes. The high sensitivity of ExRai-CKAR2, targeted to either the cytosol or Par-complexes, further enabled us to detect previously inaccessible endogenous atypical PKC (aPKC) activity in 3D organoids. Taken together, ExRai-CKAR2 is a powerful tool for interrogating PKC regulation in response to physiological stimuli.
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Affiliation(s)
- Qi Su
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Jing Zhang
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
- Moores Cancer Center, University of California San Diego, La Jolla, CA, USA
| | - Wei Lin
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Jin-Fan Zhang
- Shu Chien-Gene Lay Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
| | - Alexandra C Newton
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
- Moores Cancer Center, University of California San Diego, La Jolla, CA, USA
| | - Sohum Mehta
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Jing Yang
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
- Moores Cancer Center, University of California San Diego, La Jolla, CA, USA
- Department of Pediatrics, School of Medicine, University of California San Diego, La Jolla, CA, USA
| | - Jin Zhang
- Department of Pharmacology, School of Medicine, University of California San Diego, La Jolla, CA, USA
- Moores Cancer Center, University of California San Diego, La Jolla, CA, USA
- Shu Chien-Gene Lay Department of Bioengineering, University of California San Diego, La Jolla, CA, USA
- Department of Chemistry and Biochemistry, University of California San Diego, La Jolla, CA, USA
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2
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Holguin-Cruz JA, Bui JM, Jha A, Na D, Gsponer J. Widespread alteration of protein autoinhibition in human cancers. Cell Syst 2024; 15:246-263.e7. [PMID: 38366601 DOI: 10.1016/j.cels.2024.01.009] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Revised: 06/20/2023] [Accepted: 01/26/2024] [Indexed: 02/18/2024]
Abstract
Autoinhibition is a prevalent allosteric regulatory mechanism in signaling proteins. Reduced autoinhibition underlies the tumorigenic effect of some known cancer drivers, but whether autoinhibition is altered generally in cancer remains elusive. Here, we demonstrate that cancer-associated missense mutations, in-frame insertions/deletions, and fusion breakpoints are enriched within inhibitory allosteric switches (IASs) across all cancer types. Selection for IASs that are recurrently mutated in cancers identifies established and unknown cancer drivers. Recurrent missense mutations in IASs of these drivers are associated with distinct, cancer-specific changes in molecular signaling. For the specific case of PPP3CA, the catalytic subunit of calcineurin, we provide insights into the molecular mechanisms of altered autoinhibition by cancer mutations using biomolecular simulations, and demonstrate that such mutations are associated with transcriptome changes consistent with increased calcineurin signaling. Our integrative study shows that autoinhibition-modulating genetic alterations are positively selected for by cancer cells.
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Affiliation(s)
- Jorge A Holguin-Cruz
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Jennifer M Bui
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Ashwani Jha
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Dokyun Na
- School of Integrative Engineering, Chung-Ang University, 84 Heukseok-ro, Dongjak-gu, Seoul 156-756, Republic of Korea
| | - Jörg Gsponer
- Michael Smith Laboratories, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; Department of Biochemistry and Molecular Biology, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
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3
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Xu Y, Wang J, He Z, Rao Z, Zhang Z, Zhou J, Zhou T, Wang H. A review on the effect of COX-2-mediated mechanisms on development and progression of gastric cancer induced by nicotine. Biochem Pharmacol 2024; 220:115980. [PMID: 38081368 DOI: 10.1016/j.bcp.2023.115980] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2023] [Revised: 12/07/2023] [Accepted: 12/08/2023] [Indexed: 12/24/2023]
Abstract
Smoking is a documented risk factor for cancer, e.g., gastric cancer. Nicotine, the principal tobacco alkaloid, would exert its role of contribution to gastric cancer development and progression through nicotinic acetylcholine receptors (nAChRs) and β-adrenergic receptors (β-ARs), which then promote cancer cell proliferation, migration and invasion. As a key isoenzyme in conversion of arachidonic acid to prostaglandins, cyclooxygenase-2 (COX-2) has been demonstrated to have a wide range of effects in carcinogenesis and tumor development. At present, many studies have reported the effect of nicotine on gastric cancer by binding to nAChR, as well as indirectly stimulating β-AR to mediate COX-2-related pathways. This review summarizes these studies, and also proposes more potential COX-2-mediated mechanisms. These events might contribute to the growth and progression of gastric cancer exposed to nicotine through tobacco smoke or cigarette substitutes. Also, this review article has therefore the potential not only to make a significant contribution to the treatment and prognosis of gastric cancer for smokers but also to the clinical application of COX-2 antagonists. In addition, this work also discusses the considerable challenges of this field with special reference to the future perspective of COX-2-mediated mechanisms in development and progression of gastric cancer induced by nicotine.
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Affiliation(s)
- Yuqin Xu
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China
| | - Juan Wang
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China
| | - Zihan He
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China
| | - Zihan Rao
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China
| | - Zhongwei Zhang
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China
| | - Jianming Zhou
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China
| | - Tong Zhou
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China
| | - Huai Wang
- School of Public Health, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Jiangxi Provincial Key Laboratory of Preventive Medicine, Jiangxi Medical College, Nanchang University, No. 461 Ba Yi Avenue, Nanchang, Jiangxi 330006, PR China; Chongqing Research Institute of Nanchang University, Tai Bai Road, Tongnan, Chongqing 402679, PR China.
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Jones AC, Kornev AP, Weng JH, Manning G, Taylor SS, Newton AC. Single-residue mutation in protein kinase C toggles between cancer and neurodegeneration. Biochem J 2023; 480:1299-1316. [PMID: 37551632 PMCID: PMC10586763 DOI: 10.1042/bcj20220397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [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: 03/16/2023] [Revised: 08/04/2023] [Accepted: 08/07/2023] [Indexed: 08/09/2023]
Abstract
Conventional protein kinase C (cPKC) isozymes tune the signaling output of cells, with loss-of-function somatic mutations associated with cancer and gain-of-function germline mutations identified in neurodegeneration. PKC with impaired autoinhibition is removed from the cell by quality-control mechanisms to prevent the accumulation of aberrantly active enzyme. Here, we examine how a highly conserved residue in the C1A domain of cPKC isozymes permits quality-control degradation when mutated to histidine in cancer (PKCβ-R42H) and blocks down-regulation when mutated to proline in the neurodegenerative disease spinocerebellar ataxia (PKCγ-R41P). Using FRET-based biosensors, we determined that mutation of R42 to any residue, including lysine, resulted in reduced autoinhibition as indicated by higher basal activity and faster agonist-induced plasma membrane translocation. R42 is predicted to form a stabilizing salt bridge with E655 in the C-tail and mutation of E655, but not neighboring E657, also reduced autoinhibition. Western blot analysis revealed that whereas R42H had reduced stability, the R42P mutant was stable and insensitive to activator-induced ubiquitination and down-regulation, an effect previously observed by deletion of the entire C1A domain. Molecular dynamics (MD) simulations and analysis of stable regions of the domain using local spatial pattern (LSP) alignment suggested that P42 interacts with Q66 to impair mobility and conformation of one of the ligand-binding loops. Additional mutation of Q66 to the smaller asparagine (R42P/Q66N), to remove conformational constraints, restored degradation sensitivity. Our results unveil how disease-associated mutations of the same residue in the C1A domain can toggle between gain- or loss-of-function of PKC.
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Affiliation(s)
- Alexander C. Jones
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
- Biomedical Sciences Graduate Program, University of California, La Jolla, CA 92093, U.S.A
| | - Alexandr P. Kornev
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
| | - Jui-Hung Weng
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
| | | | - Susan S. Taylor
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, La Jolla, CA 92093, U.S.A
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5
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Abstract
Oncogenes that occur in ≤5% of non-small-cell lung cancers have been defined as 'rare'; nonetheless, this frequency can correspond to a substantial number of patients diagnosed annually. Within rare oncogenes, less commonly identified alterations (such as HRAS, NRAS, RIT1, ARAF, RAF1 and MAP2K1 mutations, or ERBB family, LTK and RASGRF1 fusions) can share certain structural or oncogenic features with more commonly recognized alterations (such as KRAS, BRAF, MET and ERBB family mutations, or ALK, RET and ROS1 fusions). Over the past 5 years, a surge in the identification of rare-oncogene-driven lung cancers has challenged the boundaries of traditional clinical grade diagnostic assays and profiling algorithms. In tandem, the number of approved targeted therapies for patients with rare molecular subtypes of lung cancer has risen dramatically. Rational drug design has iteratively improved the quality of small-molecule therapeutic agents and introduced a wave of antibody-based therapeutics, expanding the list of actionable de novo and resistance alterations in lung cancer. Getting additional molecularly tailored therapeutics approved for rare-oncogene-driven lung cancers in a larger range of countries will require ongoing stakeholder cooperation. Patient advocates, health-care agencies, investigators and companies with an interest in diagnostics, therapeutics and real-world evidence have already taken steps to surmount the challenges associated with research into low-frequency drivers.
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Affiliation(s)
- Guilherme Harada
- Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Soo-Ryum Yang
- Department of Pathology, Memorial Sloan Kettering Cancer Center, New York, NY, USA
| | - Emiliano Cocco
- Department of Biochemistry and Molecular Biology/Sylvester Comprehensive Cancer Center, University of Miami/Miller School of Medicine, Miami, FL, USA.
| | - Alexander Drilon
- Department of Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
- Department of Medicine, Weill Cornell Medical College, New York, NY, USA.
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6
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Jones AC, Kornev AP, Weng JH, Manning G, Taylor SS, Newton AC. Single-residue mutation in protein kinase C toggles between cancer and neurodegeneration. bioRxiv 2023:2023.03.16.532226. [PMID: 36993163 PMCID: PMC10055082 DOI: 10.1101/2023.03.16.532226] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Conventional protein kinase C (PKC) isozymes tune the signaling output of cells, with loss-of-function somatic mutations associated with cancer and gain-of-function germline mutations identified in neurodegeneration. PKC with impaired autoinhibition is removed from the cell by quality-control mechanisms to prevent accumulation of aberrantly active enzyme. Here, we examine how a single residue in the C1A domain of PKCβ, arginine 42 (R42), permits quality-control degradation when mutated to histidine in cancer (R42H) and blocks downregulation when mutated to proline in the neurodegenerative disease spinocerebellar ataxia (R42P). Using FRET-based biosensors, we determined that mutation of R42 to any residue, including lysine, resulted in reduced autoinhibition as indicated by higher basal activity and faster agonist-induced plasma membrane translocation. R42 is predicted to form a stabilizing salt bridge with E655 in the C-tail and mutation of E655, but not neighboring E657, also reduced autoinhibition. Western blot analysis revealed that whereas R42H had reduced stability, the R42P mutant was stable and insensitive to activator-induced ubiquitination and downregulation, an effect previously observed by deletion of the entire C1A domain. Molecular dynamics (MD) simulations and analysis of stable regions of the domain using local spatial pattern (LSP) alignment suggested that P42 interacts with Q66 to impair mobility and conformation of one of the ligand-binding loops. Additional mutation of Q66 to the smaller asparagine (R42P/Q66N), to remove conformational constraints, restored degradation sensitivity to that of WT. Our results unveil how disease-associated mutations of the same residue in the C1A domain can toggle between gain- or loss-of-function of PKC.
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7
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Gordon MT, Ziemba BP, Falke JJ. PDK1:PKCα heterodimer association-dissociation dynamics in single-molecule diffusion tracks on a target membrane. Biophys J 2023:S0006-3495(23)00090-5. [PMID: 36733254 DOI: 10.1016/j.bpj.2023.01.041] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2022] [Revised: 12/01/2022] [Accepted: 01/30/2023] [Indexed: 02/04/2023] Open
Abstract
Previous studies have documented the formation of a heterodimer between the two protein kinases PDK1 and PKCα on a lipid bilayer containing their target lipids. This work investigates the association-dissociation kinetics of this PDK1:PKCα heterodimer. The approach monitors the two-dimensional diffusion of single, membrane-associated PDK1 molecules for diffusivity changes as PKCα molecules bind and unbind. In the absence of PKCα, a membrane-associated PDK1 molecule exhibits high diffusivity (or large diffusion constant, D) because its membrane-contacting PH domain binds the target PIP3 lipid headgroup with little bilayer penetration, yielding minimal frictional drag against the bilayer. In contrast, membrane-associated PKCα contacts the bilayer via its C1A, C1B, and C2 domains, which each bind at least one target lipid with significant bilayer insertion, yielding a large frictional drag and low diffusivity. The present findings reveal that individual fluor-PDK1 molecules freely diffusing on the membrane surface undergo reversible switching between distinct high and low diffusivity states, corresponding to the PDK1 monomer and the PDK1:PKCα heterodimer, respectively. The observed single-molecule diffusion trajectories are converted to step length time courses, then subjected to two-state, hidden Markov modeling and dwell time analysis. The findings reveal that both the PDK1 monomer state and the PDK1:PKCα heterodimer state decay via simple exponential kinetics, yielding estimates of rate constants for state switching in both directions. Notably, the PDK1:PKCα heterodimer has been shown to competitively inhibit PDK1 phosphoactivation of AKT1, and is believed to play a tumor suppressor role by limiting excess activation of the highly oncogenic PDK1/AKT1/mTOR pathway. Thus, the present elucidation of the PDK1:PKCα association-dissociation kinetics has important biological and medical implications. More broadly, the findings illustrate the power of single-molecule diffusion measurements to reveal the kinetics of association-dissociation events in membrane signaling reactions that yield a large change in diffusive mobility.
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Affiliation(s)
- Moshe T Gordon
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado
| | - Brian P Ziemba
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado
| | - Joseph J Falke
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado.
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Gorczyński A, Miszewski K, Gager Y, Koch S, Pötschke J, Ugrinovski D, Gabert J, Pospieszyńska A, Wydra D, Duchnowska R, Szymanowski B, Cierniak S, Kruecken I, Neumann K, Mirkov K, Biernat W, Czapiewski P. Prognostic value of ALK overexpression and molecular abnormalities in high-grade serous ovarian carcinoma. Cancer Biomark 2023; 38:17-26. [PMID: 37522200 DOI: 10.3233/cbm-230117] [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] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/01/2023]
Abstract
BACKGROUND ALK receptor tyrosine kinase (ALK) aberrations have an established role in pathogenesis of many neoplasms, but their clinical significance in high grade serous ovarian carcinoma (HGSOC) is unclear. OBJECTIVE To analyse the frequency of ALK overexpression, molecular abnormalities of ALK, and their impact on the progression-free survival (PFS) and overall survival (OS) in HGSOC. METHODS Protein expression was examined by immunohistochemistry (IHC) using three different clones of anti-ALK antibody. The presence of translocations was analysed using fluorescent in situ hybridization. Next-generation sequencing was used for studying the copy number variation, as well as point mutation and translocations involving other commonly rearranged genes. RESULTS ALK overexpression was demonstrated in up to 52% of tumours, whereas ALK copy gains in 8.2%, with no clear impact on survival. ALK point mutations were identified in 13 tumours (8.9%), with 3 belonging to the class IV showing significantly better OS. A trend suggesting better PFS was also noticed in these cases. Additionally, three gene fusions were found: ERBB2-GRB7, PRKCA-BRCA1 and SND1-BRAF, none of which has been previously described in HGSOC. CONCLUSIONS HGSOC harbouring activating ALK mutations might be associated with a better survival, while ALK overexpression and ALK amplification does not impact the prognosis.
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Affiliation(s)
- Adam Gorczyński
- Department of Pathomorphology, Medical University of Gdansk, Gdansk, Poland
| | - Kevin Miszewski
- Department of Urology, Medical University of Gdansk, Gdansk, Poland
| | | | | | | | | | | | - Agata Pospieszyńska
- Department of Gynecology, Obstetrics and Neonatology, Medical University of Gdansk, Gdansk, Poland
| | - Dariusz Wydra
- Department of Gynecology, Obstetrics and Neonatology, Medical University of Gdansk, Gdansk, Poland
| | - Renata Duchnowska
- Department of Oncology, Military Institute of Medicine, National Research Institute, Warsaw, Poland
| | - Bartosz Szymanowski
- Department of Oncology, Military Institute of Medicine, National Research Institute, Warsaw, Poland
| | - Szczepan Cierniak
- Department of Pathology, Military Institute of Medicine, National Research Institute, Warsaw, Warsaw, Poland
| | - Irene Kruecken
- PathoNext GmbH, Leipzig, Germany
- Institute of Pathology, University of Leipzig, Leipzig, Germany
| | - Karsten Neumann
- Institute of Pathology, Staedtisches Klinikum Dessau, Brandenburg Medical School Theodor Fontane, Dessau, Germany
| | - Katarina Mirkov
- Institute of Pathology, Staedtisches Klinikum Dessau, Brandenburg Medical School Theodor Fontane, Dessau, Germany
| | - Wojciech Biernat
- Department of Pathomorphology, Medical University of Gdansk, Gdansk, Poland
| | - Piotr Czapiewski
- Institute of Pathology, Staedtisches Klinikum Dessau, Brandenburg Medical School Theodor Fontane, Dessau, Germany
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Vala RM, Tandon V, Nicely LG, Guo L, Gu Y, Banerjee S, Patel HM. Synthesis of N-(4-chlorophenyl) substituted pyrano[2,3-c]pyrazoles enabling PKBβ/AKT2 inhibitory and in vitro anti-glioma activity. Ann Med 2022; 54:2549-2561. [PMID: 36120909 PMCID: PMC9683054 DOI: 10.1080/07853890.2022.2123559] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
A series of N-(4-chlorophenyl) substituted pyrano[2,3-c]pyrazoles was synthesised and screened for their potential to inhibit kinases and exhibit anticancer activity against primary patient-derived glioblastoma 2D cells and 3D neurospheres. A collection of 10 compounds was evaluated against glioma cell lines, with compound 4j exhibiting promising glioma growth inhibitory properties. Compound 4j was screened against 139 purified kinases and exhibited low micromolar activity against kinase AKT2/PKBβ. AKT signalling is one of the main oncogenic pathways in glioma and is often targeted for novel therapeutics. Indeed, AKT2 levels correlated with glioma malignancy and poorer patient survival. Compound 4j inhibited the 3D neurosphere formation in primary patient-derived glioma stem cells and exhibited potent EC50 against glioblastoma cell lines. Although exhibiting potency against glioma cells, 4j exhibited significantly less cytotoxicity against non-cancerous cells even at fourfold-fivefold the concentration. Herein we establish a novel biochemical kinase inhibitory function for N-(4-chlorophenyl) substituted pyrano[2,3-c]pyrazoles and further report their anti-glioma activity in vitro for the first time.KEY MESSAGEAnti-glioma pyrano[2,3-c]pyrazole 4j inhibited the 3D neurosphere formation in primary patient-derived glioma stem cells. 4j also displayed PKBβ/AKT2 inhibitory activity. 4j is nontoxic towards non-cancerous cells.
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Affiliation(s)
- Ruturajsinh M Vala
- Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar, India
| | - Vasudha Tandon
- Department of Cellular & Systems Medicine, School of Medicine, University of Dundee, Dundee, UK
| | - Lynden G Nicely
- Department of Cellular & Systems Medicine, School of Medicine, University of Dundee, Dundee, UK
| | - Luxia Guo
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei, Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Yanlong Gu
- Key Laboratory of Material Chemistry for Energy Conversion and Storage, Ministry of Education, Hubei, Key Laboratory of Material Chemistry and Service Failure, School of Chemistry and Chemical Engineering, Huazhong University of Science and Technology, Wuhan, China
| | - Sourav Banerjee
- Department of Cellular & Systems Medicine, School of Medicine, University of Dundee, Dundee, UK
| | - Hitendra M Patel
- Department of Chemistry, Sardar Patel University, Vallabh Vidyanagar, India
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10
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Pilo CA, Baffi TR, Kornev AP, Kunkel MT, Malfavon M, Chen DH, Rossitto LA, Chen DX, Huang LC, Longman C, Kannan N, Raskind WH, Gonzalez DJ, Taylor SS, Gorrie G, Newton AC. Mutations in protein kinase Cγ promote spinocerebellar ataxia type 14 by impairing kinase autoinhibition. Sci Signal 2022; 15:eabk1147. [PMID: 36166510 PMCID: PMC9810342 DOI: 10.1126/scisignal.abk1147] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [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: 01/07/2023]
Abstract
Spinocerebellar ataxia type 14 (SCA14) is a neurodegenerative disease caused by germline variants in the diacylglycerol (DAG)/Ca2+-regulated protein kinase Cγ (PKCγ), leading to Purkinje cell degeneration and progressive cerebellar dysfunction. Most of the identified mutations cluster in the DAG-sensing C1 domains. Here, we found with a FRET-based activity reporter that SCA14-associated PKCγ mutations, including a previously undescribed variant, D115Y, enhanced the basal activity of the kinase by compromising its autoinhibition. Unlike other mutations in PKC that impair its autoinhibition but lead to its degradation, the C1 domain mutations protected PKCγ from such down-regulation. This enhanced basal signaling rewired the brain phosphoproteome, as revealed by phosphoproteomic analysis of cerebella from mice expressing a human SCA14-associated H101Y mutant PKCγ transgene. Mutations that induced a high basal activity in vitro were associated with earlier average age of onset in patients. Furthermore, the extent of disrupted autoinhibition, but not agonist-stimulated activity, correlated with disease severity. Molecular modeling indicated that almost all SCA14 variants not within the C1 domain were located at interfaces with the C1B domain, suggesting that mutations in and proximal to the C1B domain are a susceptibility for SCA14 because they uniquely enhance PKCγ basal activity while protecting the enzyme from down-regulation. These results provide insight into how PKCγ activation is modulated and how deregulation of the cerebellar phosphoproteome by SCA14-associated mutations affects disease progression.
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Affiliation(s)
- Caila A. Pilo
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
- Biomedical Sciences Graduate Program, University of California, La Jolla, CA 92037, USA
| | - Timothy R. Baffi
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
| | - Alexandr P. Kornev
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
| | - Maya T. Kunkel
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
| | - Mario Malfavon
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
| | - Dong-Hui Chen
- Department of Neurology, University of Washington Seattle, WA 98195, USA
| | - Leigh-Ana Rossitto
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
- Biomedical Sciences Graduate Program, University of California, La Jolla, CA 92037, USA
| | - Daniel X. Chen
- Department of Neurology, University of Washington Seattle, WA 98195, USA
| | - Liang-Chin Huang
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
| | - Cheryl Longman
- Queen Elizabeth University Hospital, Glasgow, Scotland G51 4TF, United Kingdom
| | - Natarajan Kannan
- Institute of Bioinformatics, University of Georgia, Athens, GA 30602, USA
- Department of Biochemistry and Molecular Biology, University of Georgia, Athens, GA 30602, USA
| | - Wendy H. Raskind
- Department of Medicine/Medical Genetics, University of Washington Seattle, WA 98195, USA
- Department of Psychiatry and Behavioral Sciences, University of Washington Seattle, WA 98195, USA
- Mental Illness Research, Education and Clinical Center, Department of Veterans Affairs, Seattle, WA 98108, USA
| | - David J. Gonzalez
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
| | - Susan S. Taylor
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
| | - George Gorrie
- Queen Elizabeth University Hospital, Glasgow, Scotland G51 4TF, United Kingdom
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, USA
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11
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Omar MH, Byrne DP, Jones KN, Lakey TM, Collins KB, Lee KS, Daly LA, Forbush KA, Lau HT, Golkowski M, McKnight GS, Breault DT, Lefrançois-Martinez AM, Martinez A, Eyers CE, Baird GS, Ong SE, Smith FD, Eyers PA, Scott JD. Mislocalization of protein kinase A drives pathology in Cushing's syndrome. Cell Rep 2022; 40:111073. [PMID: 35830806 PMCID: PMC9311266 DOI: 10.1016/j.celrep.2022.111073] [Citation(s) in RCA: 17] [Impact Index Per Article: 8.5] [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: 01/27/2022] [Revised: 04/20/2022] [Accepted: 06/17/2022] [Indexed: 01/15/2023] Open
Abstract
Mutations in the catalytic subunit of protein kinase A (PKAc) drive the stress hormone disorder adrenal Cushing's syndrome. We define mechanisms of action for the PKAc-L205R and W196R variants. Proximity proteomic techniques demonstrate that both Cushing's mutants are excluded from A kinase-anchoring protein (AKAP)-signaling islands, whereas live-cell photoactivation microscopy reveals that these kinase mutants indiscriminately diffuse throughout the cell. Only cAMP analog drugs that displace native PKAc from AKAPs enhance cortisol release. Rescue experiments that incorporate PKAc mutants into AKAP complexes abolish cortisol overproduction, indicating that kinase anchoring restores normal endocrine function. Analyses of adrenal-specific PKAc-W196R knockin mice and Cushing's syndrome patient tissue reveal defective signaling mechanisms of the disease. Surprisingly each Cushing's mutant engages a different mitogenic-signaling pathway, with upregulation of YAP/TAZ by PKAc-L205R and ERK kinase activation by PKAc-W196R. Thus, aberrant spatiotemporal regulation of each Cushing's variant promotes the transmission of distinct downstream pathogenic signals.
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Affiliation(s)
- Mitchell H Omar
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
| | - Dominic P Byrne
- Department of Biochemistry & Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Kiana N Jones
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Tyler M Lakey
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Kerrie B Collins
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Kyung-Soon Lee
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Leonard A Daly
- Centre for Proteome Research, Department of Biochemistry and Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Katherine A Forbush
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Ho-Tak Lau
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Martin Golkowski
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - G Stanley McKnight
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - David T Breault
- Division of Endocrinology, Boston Children's Hospital, Boston, MA 02115, USA
| | - Anne-Marie Lefrançois-Martinez
- Génétique, Reproduction et Développement (GReD), CNRS, INSERM, Université Clermont Auvergne, 63001 Clermont-Ferrand, France
| | - Antoine Martinez
- Génétique, Reproduction et Développement (GReD), CNRS, INSERM, Université Clermont Auvergne, 63001 Clermont-Ferrand, France
| | - Claire E Eyers
- Centre for Proteome Research, Department of Biochemistry and Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - Geoffrey S Baird
- Department of Laboratory Medicine and Pathology, University of Washington, Seattle, WA 98195, USA
| | - Shao-En Ong
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - F Donelson Smith
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA
| | - Patrick A Eyers
- Department of Biochemistry & Systems Biology, University of Liverpool, Liverpool L69 7ZB, UK
| | - John D Scott
- Department of Pharmacology, University of Washington, Seattle, WA 98195, USA.
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12
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Pilo CA, Newton AC. Two Sides of the Same Coin: Protein Kinase C γ in Cancer and Neurodegeneration. Front Cell Dev Biol 2022; 10:929510. [PMID: 35800893 PMCID: PMC9253466 DOI: 10.3389/fcell.2022.929510] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2022] [Accepted: 05/23/2022] [Indexed: 12/23/2022] Open
Abstract
Protein kinase C (PKC) isozymes transduce myriad signals within the cell in response to the generation of second messengers from membrane phospholipids. The conventional isozyme PKCγ reversibly binds Ca2+ and diacylglycerol, which leads to an open, active conformation. PKCγ expression is typically restricted to neurons, but evidence for its expression in certain cancers has emerged. PKC isozymes have been labeled as oncogenes since the discovery that they bind tumor-promoting phorbol esters, however, studies of cancer-associated PKC mutations and clinical trial data showing that PKC inhibitors have worsened patient survival have reframed PKC as a tumor suppressor. Aberrant expression of PKCγ in certain cancers suggests a role outside the brain, although whether PKCγ also acts as a tumor suppressor remains to be established. On the other hand, PKCγ variants associated with spinocerebellar ataxia type 14 (SCA14), a neurodegenerative disorder characterized by Purkinje cell degeneration, enhance basal activity while preventing phorbol ester-mediated degradation. Although the basis for SCA14 Purkinje cell degeneration remains unknown, studies have revealed how altered PKCγ activity rewires cerebellar signaling to drive SCA14. Importantly, enhanced basal activity of SCA14-associated mutants inversely correlates with age of onset, supporting that enhanced PKCγ activity drives SCA14. Thus, PKCγ activity should likely be inhibited in SCA14, whereas restoring PKC activity should be the goal in cancer therapies. This review describes how PKCγ activity can be lost or gained in disease and the overarching need for a PKC structure as a powerful tool to predict the effect of PKCγ mutations in disease.
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Affiliation(s)
- Caila A. Pilo
- Department of Pharmacology, University of California, San Diego, San Diego, CA, United States
- Biomedical Sciences Graduate Program, University of California, San Diego, San Diego, CA, United States
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, San Diego, San Diego, CA, United States
- *Correspondence: Alexandra C. Newton,
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13
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Peiris MN, Meyer AN, Warda D, Campos AR, Donoghue DJ. Proteomic analysis reveals dual requirement for Grb2 and PLCγ1 interactions for BCR-FGFR1-Driven 8p11 cell proliferation. Oncotarget 2022; 13:659-76. [PMID: 35574218 DOI: 10.18632/oncotarget.28228] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2022] [Accepted: 04/19/2022] [Indexed: 12/03/2022] Open
Abstract
Translocation of Fibroblast Growth Factor Receptors (FGFRs) often leads to aberrant cell proliferation and cancer. The BCR-FGFR1 fusion protein, created by chromosomal translocation t(8;22)(p11;q11), contains Breakpoint Cluster Region (BCR) joined to Fibroblast Growth Factor Receptor 1 (FGFR1). BCR-FGFR1 represents a significant driver of 8p11 myeloproliferative syndrome, or stem cell leukemia/lymphoma, which progresses to acute myeloid leukemia or T-cell lymphoblastic leukemia/lymphoma. Mutations were introduced at Y177F, the binding site for adapter protein Grb2 within BCR; and at Y766F, the binding site for the membrane associated enzyme PLCγ1 within FGFR1. We examined anchorage-independent cell growth, overall cell proliferation using hematopoietic cells, and activation of downstream signaling pathways. BCR-FGFR1-induced changes in protein phosphorylation, binding partners, and signaling pathways were dissected using quantitative proteomics to interrogate the protein interactome, the phosphoproteome, and the interactome of BCR-FGFR1. The effects on BCR-FGFR1-stimulated cell proliferation were examined using the PLCγ1 inhibitor U73122, and the irreversible FGFR inhibitor futibatinib (TAS-120), both of which demonstrated efficacy. An absolute requirement is demonstrated for the dual binding partners Grb2 and PLCγ1 in BCR-FGFR1-driven cell proliferation, and new proteins such as ECSIT, USP15, GPR89, GAB1, and PTPN11 are identified as key effectors for hematopoietic transformation by BCR-FGFR1.
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14
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Zhao J, Lampley N 3rd, Benton S, Olivares S, Zhang B, Roth A, Boutko A, Zembowicz A, Gerami P. Next-Generation Sequencing Reveals a New Class of Melanocytic Neoplasms With Hybrid Genomic Features of PEM Including Protein Kinase R 1 Alpha Gene Inactivation and Spitz Tumor-Defining Protein Kinase Fusions. Am J Dermatopathol 2022. [PMID: 35503882 DOI: 10.1097/DAD.0000000000002223] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
BACKGROUND Pigmented epithelioid melanocytoma (PEM) is a subtype of melanocytic tumor with frequent involvement of the sentinel lymph node but rare distant metastasis. Rendering a diagnosis and prognosis based on histology can be challenging. Recent genomic studies identified 2 molecular variants of PEM. One variant is characterized by the activation of the mitogen-activated protein kinase pathway and inactivation of the PRKAR1a gene. The other is associated with genomic fusions involving the protein kinase C (PRKC) gene family. OBJECTIVE We investigated the molecular and clinicopathologic features of previously unreported PEM cases to improve tumor classification and report new classes of PEM. METHODS Next-generation sequencing and histomorphologic assessment was performed on 13 PEM cases. RESULTS We identified 2 novel PEM classes. Three cases harbored PRKAR1a inactivation and genomic fusions (ALK, NTRK, and MAP3K8). These tumors had overlapping histologic features with pigmented Spitz neoplasms. Three cases had genomic fusions involving PRKCB. These cases had overlapping features with PRKCA fusions but, in 2 cases, had a notable spindle cell component. LIMITATIONS The overall sample size and amount of clinical follow-up is limited, leaving some uncertainty regarding the expected clinical course of these novel cases. CONCLUSIONS PRKAR1a-inactivated/Spitz fusion-associated PEMs and PRKCB fusion-associated PEMs represent 2 new molecular classes of PEM.
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15
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Datta A. Kinase play-off on lipid turf hints at a molecular basis for new-found tumor-suppressor activity of PKCs. Biophys J 2021; 120:5433-5435. [PMID: 34852218 DOI: 10.1016/j.bpj.2021.11.025] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Affiliation(s)
- Ankona Datta
- Department of Chemical Sciences, Tata Institute of Fundamental Research, 1 Homi Bhabha Road, Mumbai 400005, India.
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16
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Lordén G, Newton A. Conventional protein kinase C in the brain: repurposing cancer drugs for neurodegenerative treatment? Neuronal Signal 2021; 5:NS20210036. [PMID: 34737895 PMCID: PMC8536831 DOI: 10.1042/ns20210036] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2021] [Revised: 09/16/2021] [Accepted: 09/17/2021] [Indexed: 12/23/2022] Open
Abstract
Protein Kinase C (PKC) isozymes are tightly regulated kinases that transduce a myriad of signals from receptor-mediated hydrolysis of membrane phospholipids. They play an important role in brain physiology, and dysregulation of PKC activity is associated with neurodegeneration. Gain-of-function mutations in PKCα are associated with Alzheimer's disease (AD) and mutations in PKCγ cause spinocerebellar ataxia (SCA) type 14 (SCA14). This article presents an overview of the role of the conventional PKCα and PKCγ in neurodegeneration and proposes repurposing PKC inhibitors, which failed in clinical trials for cancer, for the treatment of neurodegenerative diseases.
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Affiliation(s)
- Gema Lordén
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, U.S.A
| | - Alexandra C. Newton
- Department of Pharmacology, University of California, San Diego, La Jolla, CA 92037, U.S.A
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17
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Gordon MT, Ziemba BP, Falke JJ. Single-molecule studies reveal regulatory interactions between master kinases PDK1, AKT1, and PKC. Biophys J 2021; 120:5657-5673. [PMID: 34673053 DOI: 10.1016/j.bpj.2021.10.015] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2021] [Revised: 09/30/2021] [Accepted: 10/13/2021] [Indexed: 12/26/2022] Open
Abstract
Leukocyte migration is controlled by a leading-edge chemosensory pathway that generates the regulatory lipid phosphatidylinositol-3,4,5-trisphosphate (PIP3), a growth signal, thereby driving leading-edge expansion up attractant gradients toward sites of infection, inflammation, or tissue damage. PIP3 also serves as an important growth signal in growing cells and oncogenesis. The kinases PDK1, AKT1 or PKB, and PKCα are key components of a plasma-membrane-based PIP3 and Ca2+ signaling circuit that regulates these processes. PDK1 and AKT1 are recruited to the membrane by PIP3, whereas PKCα is recruited to the membrane by Ca2+. All three of these master kinases phosphoregulate an array of protein targets. For example, PDK1 activates AKT1, PKCα, and other AGC kinases by phosphorylation at key sites. PDK1 is believed to form PDK1-AKT1 and PDK1-PKCα heterodimers stabilized by a PDK1-interacting fragment (PIF) interaction between the PDK1 PIF pocket and the PIF motif of the AGC binding partner. Here, we present the first, to our knowledge, single-molecule studies of full-length PDK1 and AKT1 on target membrane surfaces, as well as their interaction with full-length PKCα. These studies directly detect membrane-bound PDK1-AKT1 and PDK1-PKCα heterodimers stabilized by PIF interactions formed at physiological ligand concentrations. PKCα exhibits eightfold higher PDK1 affinity than AKT1 and can competitively displace AKT1 from PDK1-AKT1 heterodimers. Ensemble activity measurements under matched conditions reveal that PDK1 activates AKT1 via a cis mechanism by phosphorylating an AKT1 molecule in the same PDK1-AKT1 heterodimer, whereas PKCα acts as a competitive inhibitor of this phosphoactivation reaction by displacing AKT1 from PDK1. Overall, the findings provide insights into the binding and regulatory interactions of the three master kinases on their target membrane and suggest that a recently described tumor suppressor activity of PKC isoforms may arise from its ability to downregulate PDK1-AKT1 phosphoactivation in the PIP3-PDK1-AKT1-mTOR pathway linked to cell growth and oncogenesis.
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Affiliation(s)
- Moshe T Gordon
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado
| | - Brian P Ziemba
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado
| | - Joseph J Falke
- Molecular Biophysics Program and Department of Biochemistry, University of Colorado, Boulder, Colorado.
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18
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Abstract
The family of AGC kinases not only regulate cellular biology by phosphorylating substrates, but are themselves controlled by phosphorylation. Phosphorylation generally occurs at two conserved regions in these kinases: a loop near the entrance to the active site, termed the activation loop, that correctly aligns residues for catalysis, and a C-terminal tail whose phosphorylation at a site termed the hydrophobic motif stabilizes the active conformation. Whereas phosphorylation of the activation loop is well established to be catalyzed by the phosphoinositide-dependent kinase 1 (PDK1), the mechanism of phosphorylation of the C-tail hydrophobic motif has been controversial. For a subset of AGC kinases, which includes most protein kinase C (PKC) isozymes and Akt, phosphorylation of the hydrophobic motif in cells was shown to depend on mTORC2 over 15 years ago, yet whether by direct phosphorylation or by another mechanism has remained elusive. The recent identification of a novel and evolutionarily conserved phosphorylation site on the C-tail termed the TOR-Interaction Motif (TIM) has finally unraveled the mystery of how mTORC2 regulates its client kinases. mTORC2 does not directly phosphorylate the hydrophobic motif, rather it converts kinases such as PKC and Akt into a conformation that can ultimately autophosphorylate at the hydrophobic motif. Identification of the direct mTOR phosphorylation that facilitates auto-regulation of the C-tail hydrophobic motif revises the activation mechanisms of mTOR-regulated AGC kinases. This new twist to an old tail opens avenues for therapeutic intervention. Significance Statement The enzyme mTORC2 has been an enigmatic regulator of AGC kinases such as protein kinase C (PKC) and Akt. The recent discovery of a motif named the TOR Interaction Motif in the C-tail of these kinases solves the mystery: mTORC2 marks these kinases for maturity by, ultimately, facilitating autophosphorylation another C-tail site, the hydrophobic motif.
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