1
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Cobbaut M, Parker PJ, McDonald NQ. Into the fold: advances in understanding aPKC membrane dynamics. Biochem J 2023; 480:2037-2044. [PMID: 38100320 PMCID: PMC10754278 DOI: 10.1042/bcj20230390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 11/21/2023] [Accepted: 11/27/2023] [Indexed: 12/17/2023]
Abstract
Atypical protein kinase Cs (aPKCs) are part of the PKC family of protein kinases and are atypical because they don't respond to the canonical PKC activators diacylglycerol (DAG) and Ca2+. They are central to the organization of polarized cells and are deregulated in several cancers. aPKC recruitment to the plasma membrane compartment is crucial to their encounter with substrates associated with polarizing functions. However, in contrast with other PKCs, the mechanism by which atypical PKCs are recruited there has remained elusive until recently. Here, we bring aPKC into the fold, summarizing recent reports on the direct recruitment of aPKC to membranes, providing insight into seemingly discrepant findings and integrating them with existing literature.
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Affiliation(s)
| | - Peter J. Parker
- Protein Phosphorylation Laboratory, The Francis Crick Institute, NW1 1AT London, U.K
- School of Cancer and Pharmaceutical Sciences, King's College London, London, U.K
| | - Neil Q. McDonald
- Signalling and Structural Biology Laboratory, The Francis Crick Institute, NW1 1AT London, U.K
- Department of Biological Sciences, Institute of Structural and Molecular Biology, Birkbeck College, London, U.K
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2
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Zou D, Li Q, Pan W, Chen P, Sun M, Bao X. A novel non‑selective atypical PKC agonist could protect neuronal cell line from Aβ‑oligomer induced toxicity by suppressing Aβ generation. Mol Med Rep 2022; 25:153. [PMID: 35244193 PMCID: PMC8941380 DOI: 10.3892/mmr.2022.12669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2021] [Accepted: 02/15/2022] [Indexed: 12/04/2022] Open
Abstract
Atypical protein kinase C (aPKCs) serve key functions in embryonic development by regulating apical-basal polarity. Previous studies have shed light on their roles during adulthood, especially in the development of Alzheimer's disease (AD). Although the crystal structure of PKCι has been resolved, an agonist of aPKCs remains to be discovered. In the present study, by using the Discovery Studio program and LibDock methodology, a small molecule library (K66-X4436 KINA Set) of compounds were screened for potential binding to PKCι. Subsequently, the computational docking results were validated using affinity selection-mass spectrometry, before in vitro kinase activity was used to determine the function of the hit compounds. A cell-based model assay that can mimic the pathology of AD was then established and used to assess the function of these hit compounds. As a result, the aPKC agonist Z640 was identified, which could bind to PKCι in silico, in vitro and in this cell-based model. Z640 was further confirmed as a non-selective aPKC agonist that can activate the kinase activity of both PKCι and PKCζ. In the cell-based assay, Z640 was found to protect neuronal cell lines from amyloid-β (Aβ) oligomer-induced cell death by reducing reactive oxygen species production and restore mitochondrial function. In addition, Z640 could reduce Aβ40 generation in a dose-dependent manner and shift amyloid precursor protein processing towards the non-amyloid pathway. To conclude, the present study is the first, to the best of the authors' knowledge to identify an aPKC agonist by combining computer-assisted drug discovery and cell-based assays. The present study also revealed that aPKC agonists have therapeutic potential for the treatment of AD.
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Affiliation(s)
- Dongmei Zou
- School of Pharmacy, Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Qian Li
- Department of Biology, College of Staten Island, Staten Island, NY 10314, USA
| | - Wenyang Pan
- School of Pharmacy, Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Peng Chen
- School of Pharmacy, Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Miao Sun
- School of Pharmacy, Nantong University, Nantong, Jiangsu 226001, P.R. China
| | - Xiaofeng Bao
- School of Pharmacy, Nantong University, Nantong, Jiangsu 226001, P.R. China
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3
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Baffi TR, Newton AC. mTOR Regulation of AGC Kinases: New Twist to an Old Tail. Mol Pharmacol 2021; 101:213-218. [PMID: 34155089 DOI: 10.1124/molpharm.121.000310] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 06/09/2021] [Indexed: 11/22/2022] Open
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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4
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Chow RY, Levee TM, Kaur G, Cedeno DP, Doan LT, Atwood SX. MTOR promotes basal cell carcinoma growth through atypical PKC. Exp Dermatol 2021; 30:358-366. [PMID: 33617094 PMCID: PMC9924159 DOI: 10.1111/exd.14255] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2020] [Revised: 10/27/2020] [Accepted: 11/30/2020] [Indexed: 12/14/2022]
Abstract
Advanced basal cell carcinomas (BCCs) are driven by the Hedgehog (HH) pathway and often possess inherent resistance to SMO inhibitors. Identifying and targeting pathways that bypass SMO could provide alternative treatments for patients with advanced or metastatic BCC. Here, we use a combination of RNA-sequencing analysis of advanced human BCC tumor-normal pairs and immunostaining of human and mouse BCC samples to identify an MTOR expression signature in BCC. Pharmacological inhibition of MTOR activity in BCC cells significantly reduces cell proliferation without affecting HH signalling. Similarly, treatment of the Ptch1 fl/fl ; Gli1-CreERT2 mouse BCC tumor model with everolimus reduces tumor growth. aPKC, a downstream target of MTOR, shows reduced activity, suggesting that MTOR promotes tumor growth by activating aPKC and demonstrating that suppressing MTOR could be a promising target for BCC patients.
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Affiliation(s)
- Rachel Y. Chow
- Department of Developmental and Cell Biology, University of California, Irvine, CA, USA
| | - Taylor M. Levee
- Department of Developmental and Cell Biology, University of California, Irvine, CA, USA
| | - Gurleen Kaur
- Department of Developmental and Cell Biology, University of California, Irvine, CA, USA
| | - Daniel P. Cedeno
- Department of Developmental and Cell Biology, University of California, Irvine, CA, USA
| | - Linda T. Doan
- Department of Dermatology, University of California, Irvine, CA, USA
| | - Scott X. Atwood
- Department of Developmental and Cell Biology, University of California, Irvine, CA, USA,Department of Dermatology, University of California, Irvine, CA, USA,Chao Family Comprehensive Cancer Center, University of California, Irvine, CA, USA
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5
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Velnati S, Centonze S, Girivetto F, Capello D, Biondi RM, Bertoni A, Cantello R, Ragnoli B, Malerba M, Graziani A, Baldanzi G. Identification of Key Phospholipids That Bind and Activate Atypical PKCs. Biomedicines 2021; 9:biomedicines9010045. [PMID: 33419210 PMCID: PMC7825596 DOI: 10.3390/biomedicines9010045] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/30/2020] [Revised: 12/30/2020] [Accepted: 01/01/2021] [Indexed: 12/02/2022] Open
Abstract
PKCζ and PKCι/λ form the atypical protein kinase C subgroup, characterised by a lack of regulation by calcium and the neutral lipid diacylglycerol. To better understand the regulation of these kinases, we systematically explored their interactions with various purified phospholipids using the lipid overlay assays, followed by kinase activity assays to evaluate the lipid effects on their enzymatic activity. We observed that both PKCζ and PKCι interact with phosphatidic acid and phosphatidylserine. Conversely, PKCι is unique in binding also to phosphatidylinositol-monophosphates (e.g., phosphatidylinositol 3-phosphate, 4-phosphate, and 5-phosphate). Moreover, we observed that phosphatidylinositol 4-phosphate specifically activates PKCι, while both isoforms are responsive to phosphatidic acid and phosphatidylserine. Overall, our results suggest that atypical Protein kinase C (PKC) localisation and activity are regulated by membrane lipids distinct from those involved in conventional PKCs and unveil a specific regulation of PKCι by phosphatidylinositol-monophosphates.
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Affiliation(s)
- Suresh Velnati
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
- Correspondence:
| | - Sara Centonze
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
| | - Federico Girivetto
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
| | - Daniela Capello
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- UPO Biobank, University of Piemonte Orientale, 28100 Novara, Italy
| | - Ricardo M. Biondi
- Department of Internal Medicine 1, Goethe University Hospital Frankfurt, 60590 Frankfurt, Germany;
- Biomedicine Research Institute of Buenos Aires—CONICET—Partner Institute of the Max Planck Society, Buenos Aires C1425FQD, Argentina
| | - Alessandra Bertoni
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
| | - Roberto Cantello
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
| | | | - Mario Malerba
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Respiratory Unit, Sant’Andrea Hospital, 13100 Vercelli, Italy;
| | - Andrea Graziani
- Molecular Biotechnology Center, Department of Molecular Biotechnology and Health Sciences, University of Torino, 10126 Turin, Italy;
- Division of Oncology, Università Vita-Salute San Raffaele, 20132 Milan, Italy
| | - Gianluca Baldanzi
- Department of Translational Medicine, University of Piemonte Orientale, 28100 Novara, Italy; (S.C.); (F.G.); (D.C.); (A.B.); (R.C.); (M.M.); (G.B.)
- Center for Translational Research on Allergic and Autoimmune Diseases (CAAD), University of Piemonte Orientale, 28100 Novara, Italy
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Role of Protein Kinase C in Immune Cell Activation and Its Implication Chemical-Induced Immunotoxicity. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2021; 1275:151-163. [PMID: 33539015 DOI: 10.1007/978-3-030-49844-3_6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Protein kinase C (PKCs) isoforms play a key regulatory role in a variety of cellular functions, including cell growth and differentiation, gene expression, hormone secretion, etc. Patterns of expression for each PKC isoform differ among tissues, and it is also clear that different PKCs are often not functionally redundant, for example specific PKCs mediate specific cellular signals required for activation, proliferation, differentiation and survival of immune cells. In the last 20 years, we have been studying the role of PKCs, mainly PKCβ and its anchoring protein RACK1 (Receptor for Activated C Kinase 1), in immune cell activation, and their implication in immunosenescence and immunotoxicity. We could demonstrate that PKCβ and RACK1 are central in dendritic cell maturation and activation by chemical allergens, and their expressions can be targeted by EDCs and anti-inflammatory drugs. In this chapter, current knowledge on the role of PKC in immune cell activation and possible implication in immunotoxicity will be described.
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Chou PC, Rajput S, Zhao X, Patel C, Albaciete D, Oh WJ, Daguplo HQ, Patel N, Su B, Werlen G, Jacinto E. mTORC2 Is Involved in the Induction of RSK Phosphorylation by Serum or Nutrient Starvation. Cells 2020; 9:E1567. [PMID: 32605013 PMCID: PMC7408474 DOI: 10.3390/cells9071567] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2020] [Revised: 06/17/2020] [Accepted: 06/23/2020] [Indexed: 12/26/2022] Open
Abstract
Cells adjust to nutrient fluctuations to restore metabolic homeostasis. The mechanistic target of rapamycin (mTOR) complex 2 responds to nutrient levels and growth signals to phosphorylate protein kinases belonging to the AGC (Protein Kinases A,G,C) family such as Akt and PKC. Phosphorylation of these AGC kinases at their conserved hydrophobic motif (HM) site by mTORC2 enhances their activation and mediates the functions of mTORC2 in cell growth and metabolism. Another AGC kinase family member that is known to undergo increased phosphorylation at the homologous HM site (Ser380) is the p90 ribosomal S6 kinase (RSK). Phosphorylation at Ser380 is facilitated by the activation of the mitogen-activated protein kinase/extracellular signal regulated kinase (MAPK/ERK) in response to growth factor stimulation. Here, we demonstrate that optimal phosphorylation of RSK at this site requires an intact mTORC2. We also found that RSK is robustly phosphorylated at Ser380 upon nutrient withdrawal or inhibition of glycolysis, conditions that increase mTORC2 activation. However, pharmacological inhibition of mTOR did not abolish RSK phosphorylation at Ser380, indicating that mTOR catalytic activity is not required for this phosphorylation. Since RSK and SIN1β colocalize at the membrane during serum restimulation and acute glutamine withdrawal, mTORC2 could act as a scaffold to enhance RSK HM site phosphorylation. Among the known RSK substrates, the CCTβ subunit of the chaperonin containing TCP-1 (CCT) complex had defective phosphorylation in the absence of mTORC2. Our findings indicate that the mTORC2-mediated phosphorylation of the RSK HM site could confer RSK substrate specificity and reveal that RSK responds to nutrient fluctuations.
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Affiliation(s)
- Po-Chien Chou
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Swati Rajput
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Xiaoyun Zhao
- Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200240, China; (X.Z.); (B.S.)
| | - Chadni Patel
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Danielle Albaciete
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Won Jun Oh
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Heineken Queen Daguplo
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Nikhil Patel
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Bing Su
- Department of Immunology and Microbiology, Shanghai Jiao Tong University School of Medicine, Shanghai 200240, China; (X.Z.); (B.S.)
| | - Guy Werlen
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
| | - Estela Jacinto
- Department of Biochemistry and Molecular Biology, Rutgers-Robert Wood Johnson Medical School, Piscataway, NJ 08854, USA; (P.-C.C.); (S.R.); (C.P.); (D.A.); (W.J.O.); (H.Q.D.); (N.P.); (G.W.)
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8
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Forteza R, Ahsan MK, Cartón-García F, Arango D, Ameen NA, Salas PJ. Glucocorticoids and myosin5b loss of function induce heightened PKA signaling in addition to membrane traffic defects. Mol Biol Cell 2019; 30:3076-3089. [PMID: 31664880 PMCID: PMC6938243 DOI: 10.1091/mbc.e18-07-0415] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Loss-of-function mutations in the nonconventional myosin Vb (Myo5b) result in microvillus inclusion disease (MVID) and massive secretory diarrhea that often begins at birth. Myo5b mutations disrupt the apical recycling endosome (ARE) and membrane traffic, resulting in reduced surface expression of apical membrane proteins. ARE disruption also results in constitutive phosphoinositide-dependent kinase 1 gain of function. In MVID, decreased surface expression of apical anion channels involved in Cl- extrusion, such as cystic fibrosis transmembrane conductance regulator (CFTR), should reduce fluid secretion into the intestinal lumen. But the opposite phenotype is observed. To explain this contradiction and the onset of diarrhea, we hypothesized that signaling effects downstream from Myo5b loss of function synergize with higher levels of glucocorticoids to activate PKA and CFTR. Data from intestinal cell lines, human MVID, and Myo5b KO mouse intestine revealed changes in the subcellular redistribution of PKA activity to the apical pole, increased CFTR phosphorylation, and establishment of apical cAMP gradients in Myo5b-defective cells exposed to physiological levels of glucocorticoids. These cells also displayed net secretory fluid fluxes and transepithelial currents mainly from PKA-dependent Cl- secretion. We conclude that Myo5b defects result in PKA stimulation that activates residual channels on the surface when intestinal epithelia are exposed to glucocorticoids at birth.
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Affiliation(s)
- Radia Forteza
- Department of Cell Biology, Miller School of Medicine, University of Miami, Miami, FL 33136
| | - M Kaimul Ahsan
- Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT 06510
| | - Fernando Cartón-García
- Group of Biomedical Research in Digestive Tract Tumors, CIBBIM-Nanomedicine, Vall d'Hebron University Hospital Research Institute (VHIR), Universitat Autónoma de Barcelona, 08035 Barcelona, Spain
| | - Diego Arango
- Group of Biomedical Research in Digestive Tract Tumors, CIBBIM-Nanomedicine, Vall d'Hebron University Hospital Research Institute (VHIR), Universitat Autónoma de Barcelona, 08035 Barcelona, Spain
| | - Nadia A Ameen
- Department of Pediatrics, Yale School of Medicine, Yale University, New Haven, CT 06510
| | - Pedro J Salas
- Department of Cell Biology, Miller School of Medicine, University of Miami, Miami, FL 33136
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9
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aPKC in neuronal differentiation, maturation and function. Neuronal Signal 2019; 3:NS20190019. [PMID: 32269838 PMCID: PMC7104321 DOI: 10.1042/ns20190019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 09/10/2019] [Accepted: 09/11/2019] [Indexed: 12/17/2022] Open
Abstract
The atypical Protein Kinase Cs (aPKCs)—PRKCI, PRKCZ and PKMζ—form a subfamily within the Protein Kinase C (PKC) family. These kinases are expressed in the nervous system, including during its development and in adulthood. One of the aPKCs, PKMζ, appears to be restricted to the nervous system. aPKCs are known to play a role in a variety of cellular responses such as proliferation, differentiation, polarity, migration, survival and key metabolic functions such as glucose uptake, that are critical for nervous system development and function. Therefore, these kinases have garnered a lot of interest in terms of their functional role in the nervous system. Here we review the expression and function of aPKCs in neural development and in neuronal maturation and function. Despite seemingly paradoxical findings with genetic deletion versus gene silencing approaches, we posit that aPKCs are likely candidates for regulating many important neurodevelopmental and neuronal functions, and may be associated with a number of human neuropsychiatric diseases.
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10
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Jung HY, Fattet L, Tsai JH, Kajimoto T, Chang Q, Newton AC, Yang J. Apical-basal polarity inhibits epithelial-mesenchymal transition and tumour metastasis by PAR-complex-mediated SNAI1 degradation. Nat Cell Biol 2019; 21:359-371. [PMID: 30804505 PMCID: PMC6546105 DOI: 10.1038/s41556-019-0291-8] [Citation(s) in RCA: 86] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2018] [Accepted: 01/21/2019] [Indexed: 01/06/2023]
Abstract
Loss of apical-basal polarity and activation of epithelial-mesenchymal transition (EMT) both contribute to carcinoma progression and metastasis. Here, we report that apical-basal polarity inhibits EMT to suppress metastatic dissemination. Using mouse and human epithelial three-dimensional organoid cultures, we show that the PAR-atypical protein kinase C (aPKC) polarity complex inhibits EMT and invasion by promoting degradation of the SNAIL family protein SNAI1. Under intact apical-basal polarity, aPKC kinases phosphorylate S249 of SNAI1, which leads to protein degradation. Loss of apical-basal polarity prevents aPKC-mediated SNAI1 phosphorylation and stabilizes the SNAI1 protein to promote EMT and invasion. In human breast tumour xenografts, inhibition of the PAR-complex-mediated SNAI1 degradation mechanism promotes tumour invasion and metastasis. Analyses of human breast tissue samples reveal negative correlations between PAR3 and SNAI1 protein levels. Our results demonstrate that apical-basal polarity functions as a critical checkpoint of EMT to precisely control epithelial-mesenchymal plasticity during tumour metastasis.
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Affiliation(s)
- Hae-Yun Jung
- Department of Pharmacology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA
| | - Laurent Fattet
- Department of Pharmacology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA
| | - Jeff H Tsai
- Department of Pharmacology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA
| | - Taketoshi Kajimoto
- Department of Pharmacology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA
| | - Qiang Chang
- Department of Medical Genetics and Department of Neurology, Waisman Center, University of Wisconsin-Madison, Madison, WI, USA
| | - Alexandra C Newton
- Department of Pharmacology, Moores Cancer Center, University of California, San Diego, La Jolla, CA, USA
| | - Jing Yang
- Department of Pharmacology, 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.
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11
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Abstract
Protein kinase C (PKC) isozymes belong to a family of Ser/Thr kinases whose activity is governed by reversible release of an autoinhibitory pseudosubstrate. For conventional and novel isozymes, this is effected by binding the lipid second messenger, diacylglycerol, but for atypical PKC isozymes, this is effected by binding protein scaffolds. PKC shot into the limelight following the discovery in the 1980s that the diacylglycerol-sensitive isozymes are "receptors" for the potent tumor-promoting phorbol esters. This set in place a concept that PKC isozymes are oncoproteins. Yet three decades of cancer clinical trials targeting PKC with inhibitors failed and, in some cases, worsened patient outcome. Emerging evidence from cancer-associated mutations and protein expression levels provide a reason: PKC isozymes generally function as tumor suppressors and their activity should be restored, not inhibited, in cancer therapies. And whereas not enough activity is associated with cancer, variants with enhanced activity are associated with degenerative diseases such as Alzheimer's disease. This review describes the tightly controlled mechanisms that ensure PKC activity is perfectly balanced and what happens when these controls are deregulated. PKC isozymes serve as a paradigm for the wisdom of Confucius: "to go beyond is as wrong as to fall short."
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Affiliation(s)
- Alexandra C Newton
- a Department of Pharmacology , University of California at San Diego , La Jolla , CA , USA
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12
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Kajimoto T, Caliman AD, Tobias IS, Okada T, Pilo CA, Van AAN, Andrew McCammon J, Nakamura SI, Newton AC. Activation of atypical protein kinase C by sphingosine 1-phosphate revealed by an aPKC-specific activity reporter. Sci Signal 2019; 12:eaat6662. [PMID: 30600259 PMCID: PMC6657501 DOI: 10.1126/scisignal.aat6662] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Atypical protein kinase C (aPKC) isozymes are unique in the PKC superfamily in that they are not regulated by the lipid second messenger diacylglycerol, which has led to speculation about whether a different second messenger acutely controls their function. Here, using a genetically encoded reporter that we designed, aPKC-specific C kinase activity reporter (aCKAR), we found that the lipid mediator sphingosine 1-phosphate (S1P) promoted the cellular activity of aPKC. Intracellular S1P directly bound to the purified kinase domain of aPKC and relieved autoinhibitory constraints, thereby activating the kinase. In silico studies identified potential binding sites on the kinase domain, one of which was validated biochemically. In HeLa cells, S1P-dependent activation of aPKC suppressed apoptosis. Together, our findings identify a previously undescribed molecular mechanism of aPKC regulation, a molecular target for S1P in cell survival regulation, and a tool to further explore the biochemical and biological functions of aPKC.
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Affiliation(s)
- Taketoshi Kajimoto
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA.
- Division of Biochemistry, Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan
| | - Alisha D Caliman
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA
| | - Irene S Tobias
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA
| | - Taro Okada
- Division of Biochemistry, Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan
| | - Caila A Pilo
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA
| | - An-Angela N Van
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA
| | - J Andrew McCammon
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA
| | - Shun-Ichi Nakamura
- Division of Biochemistry, Department of Biochemistry and Molecular Biology, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan
| | - Alexandra C Newton
- Department of Pharmacology, University of California at San Diego, La Jolla, CA 92037, USA.
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13
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Moloughney JG, Vega-Cotto NM, Liu S, Patel C, Kim PK, Wu CC, Albaciete D, Magaway C, Chang A, Rajput S, Su X, Werlen G, Jacinto E. mTORC2 modulates the amplitude and duration of GFAT1 Ser-243 phosphorylation to maintain flux through the hexosamine pathway during starvation. J Biol Chem 2018; 293:16464-16478. [PMID: 30201609 DOI: 10.1074/jbc.ra118.003991] [Citation(s) in RCA: 31] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2018] [Revised: 08/28/2018] [Indexed: 12/12/2022] Open
Abstract
The mechanistic target of rapamycin (mTOR) controls metabolic pathways in response to nutrients. Recently, we have shown that mTOR complex 2 (mTORC2) modulates the hexosamine biosynthetic pathway (HBP) by promoting the expression of the key enzyme of the HBP, glutamine:fructose-6-phosphate aminotransferase 1 (GFAT1). Here, we found that GFAT1 Ser-243 phosphorylation is also modulated in an mTORC2-dependent manner. In response to glutamine limitation, active mTORC2 prolongs the duration of Ser-243 phosphorylation, albeit at lower amplitude. Blocking glycolysis using 2-deoxyglucose robustly enhances Ser-243 phosphorylation, correlating with heightened mTORC2 activation, increased AMPK activity, and O-GlcNAcylation. However, when 2-deoxyglucose is combined with glutamine deprivation, GFAT1 Ser-243 phosphorylation and mTORC2 activation remain elevated, whereas AMPK activation and O-GlcNAcylation diminish. Phosphorylation at Ser-243 promotes GFAT1 expression and production of GFAT1-generated metabolites including ample production of the HBP end-product, UDP-GlcNAc, despite nutrient starvation. Hence, we propose that the mTORC2-mediated increase in GFAT1 Ser-243 phosphorylation promotes flux through the HBP to maintain production of UDP-GlcNAc when nutrients are limiting. Our findings provide insights on how the HBP is reprogrammed via mTORC2 in nutrient-addicted cancer cells.
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Affiliation(s)
- Joseph G Moloughney
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Nicole M Vega-Cotto
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Sharon Liu
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Chadni Patel
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Peter K Kim
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Chang-Chih Wu
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Danielle Albaciete
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Cedric Magaway
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Austin Chang
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Swati Rajput
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Xiaoyang Su
- Department of Medicine, Division of Endocrinology, Child Health Institute of New Jersey, Rutgers, The State University of New Jersey, New Brunswick, New Jersey 08901
| | - Guy Werlen
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
| | - Estela Jacinto
- From the Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854 and
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14
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Drummond ML, Li M, Tarapore E, Nguyen TTL, Barouni BJ, Cruz S, Tan KC, Oro AE, Atwood SX. Actin polymerization controls cilia-mediated signaling. J Cell Biol 2018; 217:3255-3266. [PMID: 29945904 PMCID: PMC6122990 DOI: 10.1083/jcb.201703196] [Citation(s) in RCA: 49] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2017] [Revised: 03/29/2018] [Accepted: 05/31/2018] [Indexed: 01/20/2023] Open
Abstract
Actin polymerization is important to generate primary cilia. Drummond et al. show that upstream actin regulators are necessary for this process by controlling aPKC and Src kinase activity to promote Hedgehog signaling and restrict primary cilia. Primary cilia are polarized organelles that allow detection of extracellular signals such as Hedgehog (Hh). How the cytoskeleton supporting the cilium generates and maintains a structure that finely tunes cellular response remains unclear. Here, we find that regulation of actin polymerization controls primary cilia and Hh signaling. Disrupting actin polymerization, or knockdown of N-WASp/Arp3, increases ciliation frequency, axoneme length, and Hh signaling. Cdc42, a potent actin regulator, recruits both atypical protein pinase C iota/lambda (aPKC) and Missing-in-Metastasis (MIM) to the basal body to maintain actin polymerization and restrict axoneme length. Transcriptome analysis implicates the Src pathway as a major aPKC effector. aPKC promotes whereas MIM antagonizes Src activity to maintain proper levels of primary cilia, actin polymerization, and Hh signaling. Hh pathway activation requires Smoothened-, Gli-, and Gli1-specific activation by aPKC. Surprisingly, longer axonemes can amplify Hh signaling, except when aPKC is disrupted, reinforcing the importance of the Cdc42–aPKC–Gli axis in actin-dependent regulation of primary cilia signaling.
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Affiliation(s)
- Michael L Drummond
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA
| | - Mischa Li
- Department of Dermatology, Program in Epithelial Biology, Stanford University School of Medicine, Stanford, CA
| | - Eric Tarapore
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA
| | - Tuyen T L Nguyen
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA
| | - Baina J Barouni
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA
| | - Shaun Cruz
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA
| | - Kevin C Tan
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA
| | - Anthony E Oro
- Department of Dermatology, Program in Epithelial Biology, Stanford University School of Medicine, Stanford, CA
| | - Scott X Atwood
- Department of Developmental and Cell Biology, University of California, Irvine, Irvine, CA .,Department of Dermatology, University of California, Irvine, Irvine, CA.,Chao Family Comprehensive Cancer Center, University of California, Irvine, Irvine, CA
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15
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Protein kinase Cα gain-of-function variant in Alzheimer's disease displays enhanced catalysis by a mechanism that evades down-regulation. Proc Natl Acad Sci U S A 2018; 115:E5497-E5505. [PMID: 29844158 DOI: 10.1073/pnas.1805046115] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
Conventional protein kinase C (PKC) family members are reversibly activated by binding to the second messengers Ca2+ and diacylglycerol, events that break autoinhibitory constraints to allow the enzyme to adopt an active, but degradation-sensitive, conformation. Perturbing these autoinhibitory constraints, resulting in protein destabilization, is one of many mechanisms by which PKC function is lost in cancer. Here, we address how a gain-of-function germline mutation in PKCα in Alzheimer's disease (AD) enhances signaling without increasing vulnerability to down-regulation. Biochemical analyses of purified protein demonstrate that this mutation results in an ∼30% increase in the catalytic rate of the activated enzyme, with no changes in the concentrations of Ca2+ or lipid required for half-maximal activation. Molecular dynamics simulations reveal that this mutation has both localized and allosteric effects, most notably decreasing the dynamics of the C-helix, a key determinant in the catalytic turnover of kinases. Consistent with this mutation not altering autoinhibitory constraints, live-cell imaging studies reveal that the basal signaling output of PKCα-M489V is unchanged. However, the mutant enzyme in cells displays increased sensitivity to an inhibitor that is ineffective toward scaffolded PKC, suggesting the altered dynamics of the kinase domain may influence protein interactions. Finally, we show that phosphorylation of a key PKC substrate, myristoylated alanine-rich C-kinase substrate, is increased in brains of CRISPR-Cas9 genome-edited mice containing the PKCα-M489V mutation. Our results unveil how an AD-associated mutation in PKCα permits enhanced agonist-dependent signaling via a mechanism that evades the cell's homeostatic down-regulation of constitutively active PKCα.
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16
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Börtlein C, Draeger A, Schoenauer R, Kuhlemann A, Sauer M, Schneider-Schaulies S, Avota E. The Neutral Sphingomyelinase 2 Is Required to Polarize and Sustain T Cell Receptor Signaling. Front Immunol 2018; 9:815. [PMID: 29720981 PMCID: PMC5915489 DOI: 10.3389/fimmu.2018.00815] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2018] [Accepted: 04/04/2018] [Indexed: 01/02/2023] Open
Abstract
By promoting ceramide release at the cytosolic membrane leaflet, the neutral sphingomyelinase 2 (NSM) is capable of organizing receptor and signalosome segregation. Its role in T cell receptor (TCR) signaling remained so far unknown. We now show that TCR-driven NSM activation is dispensable for TCR clustering and initial phosphorylation, but of crucial importance for further signal amplification. In particular, at low doses of TCR stimulatory antibodies, NSM is required for Ca2+ mobilization and T cell proliferation. NSM-deficient T cells lack sustained CD3ζ and ZAP-70 phosphorylation and are unable to polarize and stabilize their microtubular system. We identified PKCζ as the key NSM downstream effector in this second wave of TCR signaling supporting dynamics of microtubule-organizing center (MTOC). Ceramide supplementation rescued PKCζ membrane recruitment and MTOC translocation in NSM-deficient cells. These findings identify the NSM as essential in TCR signaling when dynamic cytoskeletal reorganization promotes continued lateral and vertical supply of TCR signaling components: CD3ζ, Zap70, and PKCζ, and functional immune synapses are organized and stabilized via MTOC polarization.
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Affiliation(s)
- Charlene Börtlein
- Institute for Virology and Immunobiology, University of Wuerzburg, Wuerzburg, Germany
| | - Annette Draeger
- Department of Cell Biology, Institute for Anatomy, University of Bern, Bern, Switzerland
| | - Roman Schoenauer
- Department of Cell Biology, Institute for Anatomy, University of Bern, Bern, Switzerland
| | - Alexander Kuhlemann
- Department of Biotechnology and Biophysics, University of Wuerzburg, Wuerzburg, Germany
| | - Markus Sauer
- Department of Biotechnology and Biophysics, University of Wuerzburg, Wuerzburg, Germany
| | | | - Elita Avota
- Institute for Virology and Immunobiology, University of Wuerzburg, Wuerzburg, Germany
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17
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Ganesan S, Summers CM, Pearce SC, Gabler NK, Valentine RJ, Baumgard LH, Rhoads RP, Selsby JT. Short-term heat stress altered metabolism and insulin signaling in skeletal muscle. J Anim Sci 2018; 96:154-167. [PMID: 29432553 PMCID: PMC6140929 DOI: 10.1093/jas/skx083] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2017] [Accepted: 02/06/2018] [Indexed: 12/12/2022] Open
Abstract
Heat-related complications continue to be a major health concern for humans and animals and lead to potentially life-threatening conditions. Heat stress (HS) alters metabolic parameters and may alter glucose metabolism and insulin signaling. Therefore, the purpose of this investigation was to determine the extent to which 12 h of HS-altered energetic metabolism in oxidative skeletal muscle. To address this, crossbred gilts (n = 8/group) were assigned to one of three environmental treatments for 12 h: thermoneutral (TN; 21 °C), HS (37 °C), or pair-fed to HS counterparts but housed in TN conditions (PFTN). Following treatment, animals were euthanized and the semitendinosus red (STR) was recovered. Despite increased relative protein abundance of the insulin receptor, insulin receptor substrate (IRS1) phosphorylation was increased (P = 0.0005) at S307, an inhibitory site, and phosphorylated protein kinase B (AKT) (S473) was decreased (P = 0.03) likely serving to impair insulin signaling following 12 h of HS. Further, HS increased phosphorylated protein kinase C (PKC) ζ/λ (P = 0.02) and phosphorylated PKCδ/θ protein abundance (P = 0.02), which are known to regulate inhibitory serine phosphorylation of IRS1 (S307). Sarcolemmal glucose transporter 4 (Glut4) was decreased (P = 0.04) in the membrane fraction of HS skeletal muscle suggesting diminished glucose uptake capacity. HS-mediated increases (P = 0.04) in mechanistic target of rapamycin (mTOR) were not accompanied by phosphorylation of eukaryotic translation initiation factor 4E-binding protein 1 (4EBP1). HS decreased (P = 0.0006) glycogen synthase (GS) and increased (P = 0.02) phosphorylated GS suggesting impaired glycogen synthesis. In addition, HS altered fatty acid metabolic signaling by increasing (P = 0.02) Acetyl-CoA carboxylase (ACC), decreasing (P = 0.005) phosphorylated ATP-citrate lyase (pATPCL) and fatty acid synthase (P = 0.01) (FAS). These data suggest that 12 h of HS blunted insulin signaling, decreased protein synthesis, and altered glycogen and fatty acid metabolism.
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Affiliation(s)
- Shanthi Ganesan
- Department of Animal Science, Iowa State University, Ames, IA
| | - Corey M Summers
- Department of Animal Science, Iowa State University, Ames, IA
- Department of Kinesiology, Iowa State University, Ames, IA
| | - Sarah C Pearce
- Department of Animal Science, Iowa State University, Ames, IA
| | | | | | | | - Robert P Rhoads
- Department of Animal and Poultry Sciences, Virginia Tech, Blacksburg, VA
| | - Joshua T Selsby
- Department of Animal Science, Iowa State University, Ames, IA
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18
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Chandrashekaran IR, Norton RS, Schmitz-Peiffer C. Characterisation of peptide interactions that regulate PKCε activation. FEBS Lett 2018; 592:179-189. [PMID: 29266266 DOI: 10.1002/1873-3468.12953] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2017] [Revised: 11/13/2017] [Accepted: 12/10/2017] [Indexed: 11/09/2022]
Abstract
Targeting the interaction between PKC isoforms and their anchoring proteins can specifically regulate kinase activity. εV1-2 and pseudoεRACK peptides, derived from the PKCε C2 domain, modulate its association with receptor for activated C-kinase 2 (RACK2) and thus its function. Details of these interactions remain obscure, and we therefore investigated binding of these peptides using biophysical techniques. Surface plasmon resonance (SPR) indicated that the inhibitory εV1-2 peptide bound to RACK2, and inhibited PKCε binding as expected. In contrast, SPR and NMR demonstrated that the activating pseudoεRACK peptide and related sequences did not bind to PKCε, indicating that their mechanisms of action do not involve binding to the kinase as previously proposed. Our results clarify which interactions could be targeted in developing new therapeutics that inhibit PKCε-RACK2 interaction.
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Affiliation(s)
- Indu R Chandrashekaran
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Raymond S Norton
- Medicinal Chemistry, Monash Institute of Pharmaceutical Sciences, Monash University, Parkville, Australia
| | - Carsten Schmitz-Peiffer
- Diabetes and Metabolism Division, Garvan Institute of Medical Research, Darlinghurst, Australia.,St Vincent's Clinical School, Faculty of Medicine, University of New South Wales, Sydney, Australia
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19
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Criteria for identifying the molecular basis of the engram (CaMKII, PKMzeta). Mol Brain 2017; 10:55. [PMID: 29187215 PMCID: PMC5707903 DOI: 10.1186/s13041-017-0337-4] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2017] [Accepted: 11/16/2017] [Indexed: 11/22/2022] Open
Abstract
The engram refers to the molecular changes by which a memory is stored in the brain. Substantial evidence suggests that memory involves learning-dependent changes at synapses, a process termed long-term potentiation (LTP). Thus, understanding the storages process that underlies LTP may provide insight into how the engram is stored. LTP involves induction, maintenance (storage), and expression sub-processes; special tests are required to specifically reveal properties of the storage process. The strongest of these is the Erasure test in which a transiently applied agent that attacks a putative storage molecule may lead to persistent erasure of previously induced LTP/memory. Two major hypotheses have been proposed for LTP/memory storage: the CaMKII and PKM-zeta hypotheses. After discussing the tests that can be used to identify the engram (Necessity test, Saturation/Occlusion test, Erasure test), the status of these hypotheses is evaluated, based on the literature on LTP and memory-guided behavior. Review of the literature indicates that all three tests noted above support the CaMKII hypothesis when done at both the LTP level and at the behavioral level. Taken together, the results strongly suggest that the engram is stored by an LTP process in which CaMKII is a critical memory storage molecule.
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20
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HIF and HOIL-1L-mediated PKCζ degradation stabilizes plasma membrane Na,K-ATPase to protect against hypoxia-induced lung injury. Proc Natl Acad Sci U S A 2017; 114:E10178-E10186. [PMID: 29109255 DOI: 10.1073/pnas.1713563114] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Organisms have evolved adaptive mechanisms in response to stress for cellular survival. During acute hypoxic stress, cells down-regulate energy-consuming enzymes such as Na,K-ATPase. Within minutes of alveolar epithelial cell (AEC) exposure to hypoxia, protein kinase C zeta (PKCζ) phosphorylates the α1-Na,K-ATPase subunit and triggers it for endocytosis, independently of the hypoxia-inducible factor (HIF). However, the Na,K-ATPase activity is essential for cell homeostasis. HIF induces the heme-oxidized IRP2 ubiquitin ligase 1L (HOIL-1L), which leads to PKCζ degradation. Here we report a mechanism of prosurvival adaptation of AECs to prolonged hypoxia where PKCζ degradation allows plasma membrane Na,K-ATPase stabilization at ∼50% of normoxic levels, preventing its excessive down-regulation and cell death. Mice lacking HOIL-1L in lung epithelial cells (CreSPC/HOIL-1Lfl/fl ) were sensitized to hypoxia because they express higher levels of PKCζ and, consequently, lower plasma membrane Na,K-ATPase levels, which increased cell death and worsened lung injury. In AECs, expression of an α1-Na,K-ATPase construct bearing an S18A (α1-S18A) mutation, which precludes PKCζ phosphorylation, stabilized the Na,K-ATPase at the plasma membrane and prevented hypoxia-induced cell death even in the absence of HOIL-1L. Adenoviral overexpression of the α1-S18A mutant Na,K-ATPase in vivo rescued the enhanced sensitivity of CreSPC/HOIL-1Lfl/fl mice to hypoxic lung injury. These data suggest that stabilization of Na,K-ATPase during severe hypoxia is a HIF-dependent process involving PKCζ degradation. Accordingly, we provide evidence of an important adaptive mechanism to severe hypoxia, whereby halting the exaggerated down-regulation of plasma membrane Na,K-ATPase prevents cell death and lung injury.
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21
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Kinases of eIF2a Switch Translation of mRNA Subset during Neuronal Plasticity. Int J Mol Sci 2017; 18:ijms18102213. [PMID: 29065505 PMCID: PMC5666893 DOI: 10.3390/ijms18102213] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 10/18/2017] [Accepted: 10/19/2017] [Indexed: 12/31/2022] Open
Abstract
Compared to other types of cells, neurons express the largest number of diverse mRNAs, including neuron-specific ones. This mRNA diversity is required for neuronal function, memory storage, maintenance and retrieval. Regulation of translation in neurons is very complicated and involves various proteins. Some proteins, implementing translational control in other cell types, are used by neurons for synaptic plasticity. In this review, we discuss the neuron-specific activity of four kinases: protein kinase R (PKR), PKR-like endoplasmic reticulum kinase (PERK), general control nonderepressible 2 kinase (GCN2), and heme-reguated eIF2α kinase (HRI), the substrate for which is α-subunit of eukaryotic initiation factor 2 (eIF2α). Phosphorylation of eIF2α is necessary for the cell during stress conditions, such as lack of amino acids, energy stress or viral infection. We propose that, during memory formation, neurons use some mechanisms similar to those involved in the cellular stress. The four eIF2α kinases regulate translation of certain mRNAs containing upstream open reading frames (uORFs). These mRNAs encode proteins involved in the processes of long-term potentiation (LTP) or long-term depression (LTD). The review examines some neuronal proteins for which translation regulation by eIF2 was suggested and checked experimentally. Of such proteins, we pay close attention to protein kinase Mζ, which is involved in memory storage and regulated at the translational level.
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Abstract
Protein and lipid kinases are deregulated in most, if not all, cancers and are among the most valuable therapeutic targets in these diseases. Despite the introduction of dozens of effective kinase inhibitors into clinical practice, the development of drug resistance remains a major barrier to treatment because of adaption of cellular signaling pathways to bypass targeted kinases. So that the basal and adaptive responses of kinases in cancer can be better understood, new methods have emerged that allow simultaneous and unbiased measurement of the activation state of a substantial fraction of the entire kinome. Here, we discuss such kinome-profiling methodologies, emphasizing the relative strengths and weaknesses of each approach.
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Affiliation(s)
- Maria Radu
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA, 19111-2497, USA
| | - Jonathan Chernoff
- Cancer Biology Program, Fox Chase Cancer Center, 333 Cottman Avenue, Philadelphia, PA, 19111-2497, USA
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23
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Protein kinase C as a tumor suppressor. Semin Cancer Biol 2017; 48:18-26. [PMID: 28476658 DOI: 10.1016/j.semcancer.2017.04.017] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2017] [Revised: 03/31/2017] [Accepted: 04/28/2017] [Indexed: 01/01/2023]
Abstract
Protein kinase C (PKC) has historically been considered an oncoprotein. This stems in large part from the discovery in the early 1980s that PKC is directly activated by tumor-promoting phorbol esters. Yet three decades of clinical trials using PKC inhibitors in cancer therapies not only failed, but in some cases worsened patient outcome. Why has targeting PKC in cancer eluded successful therapies? Recent studies looking at the disease for insight provide an explanation: cancer-associated mutations in PKC are generally loss-of-function (LOF), supporting an unexpected function as tumor suppressors. And, contrasting with LOF mutations in cancer, germline mutations that enhance the activity of some PKC isozymes are associated with degenerative diseases such as Alzheimer's disease. This review provides a background on the diverse mechanisms that ensure PKC is only active when, where, and for the appropriate duration needed and summarizes recent findings converging on a paradigm reversal: PKC family members generally function by suppressing, rather than promoting, survival signaling.
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24
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Velázquez DM, Castañeda-Patlán MC, Robles-Flores M. Dishevelled stability is positively regulated by PKCζ-mediated phosphorylation induced by Wnt agonists. Cell Signal 2017; 35:107-117. [PMID: 28366812 DOI: 10.1016/j.cellsig.2017.03.023] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2017] [Revised: 03/28/2017] [Accepted: 03/29/2017] [Indexed: 10/19/2022]
Abstract
Dishevelled (Dvl) proteins are central mediators of both canonical and non-canonical Wnt signaling. It is well known that, upon Wnt stimulation, Dvl becomes phosphorylated. However, how Wnt-induced phosphorylation of Dvl is regulated and its consequences are poorly understood. Here we found that Dvl proteins are overexpressed in colon cancer cells. In addition, we found that Wnt3a treatment rapidly induces hyperphosphorylation and stabilization of Dvl2 and Dvl3. The latter can be blocked by inhibition of Protein Kinase C (PKC)α, PKCδ, and PKCζ isoforms. We also found that Wnt3a-induced phosphorylation of Dvl3 by PKCζ is required to avoid Dvl3 degradation via proteasome. This demonstrated, to our knowledge for the first time, that hyperphosphorylation of Dvl by PKCζ results in Dvl stabilization. This is clear contrast with the consequences reported to date of CK1δ/ε-mediated Dvl phosphorylation upon Wnt treatment. Mapping the interaction domain between PKCζ and Dvl3 indicated that, although the Dvl-DIX domain is required to stabilize PKCζ-phosphorylated Dvl, it is not the region phosphorylated by this kinase. Our data show that the Dvl-DEP domain, required for specific interaction with PKCζ, is the site phosphorylated by this kinase, and also probably the Dvl-C terminus. Our findings suggest a model of positive regulation of PKCζ-mediated Dvl signaling activity, to produce a strong and sustained response to Wnt3a treatment by stabilizing Dvl protein levels.
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Affiliation(s)
- Dora M Velázquez
- Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico
| | - M Cristina Castañeda-Patlán
- Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico
| | - Martha Robles-Flores
- Department of Biochemistry, Faculty of Medicine, Universidad Nacional Autónoma de México (UNAM), Mexico City, Mexico.
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25
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Abstract
Understanding the molecular mechanisms behind the capacity of cancer cells to adapt to the tumor microenvironment and to anticancer therapies is a major challenge. In this context, cancer is believed to be an evolutionary process where random mutations and the selection process shape the mutational pattern and phenotype of cancer cells. This article challenges the notion of randomness of some cancer-associated mutations by describing molecular mechanisms involving stress-mediated biogenesis of mRNA-derived small RNAs able to target and increase the local mutation rate of the genomic loci they originate from. It is proposed that the probability of some mutations at specific loci could be increased in a stress-specific and RNA-depending manner. This would increase the probability of generating mutations that could alleviate stress situations, such as those triggered by anticancer drugs. Such a mechanism is made possible because tumor- and anticancer drug-associated stress situations trigger both cellular reprogramming and inflammation, which leads cancer cells to express molecular tools allowing them to “attack” and mutate their own genome in an RNA-directed manner.
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Affiliation(s)
- Didier Auboeuf
- Univ Lyon, ENS de Lyon, Univ Claude Bernard, CNRS UMR 5239, INSERM U1210, Laboratory of Biology and Modelling of the Cell, Lyon, France
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26
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Das J, Ramani R, Suraju MO. Polyphenol compounds and PKC signaling. Biochim Biophys Acta Gen Subj 2016; 1860:2107-21. [PMID: 27369735 DOI: 10.1016/j.bbagen.2016.06.022] [Citation(s) in RCA: 67] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2016] [Revised: 06/01/2016] [Accepted: 06/26/2016] [Indexed: 12/17/2022]
Abstract
BACKGROUND Naturally occurring polyphenols found in food sources provide huge health benefits. Several polyphenolic compounds are implicated in the prevention of disease states, such as cancer. One of the mechanisms by which polyphenols exert their biological actions is by interfering in the protein kinase C (PKC) signaling pathways. PKC belongs to a superfamily of serine-threonine kinase and are primarily involved in phosphorylation of target proteins controlling activation and inhibition of many cellular processes directly or indirectly. SCOPE OF REVIEW Despite the availability of substantial literature data on polyphenols' regulation of PKC, no comprehensive review article is currently available on this subject. This article reviews PKC-polyphenol interactions and its relevance to various disease states. In particular, salient features of polyphenols, PKC, interactions of naturally occurring polyphenols with PKC, and future perspective of research on this subject are discussed. MAJOR CONCLUSIONS Some polyphenols exert their antioxidant properties by regulating the transcription of the antioxidant enzyme genes through PKC signaling. Regulation of PKC by polyphenols is isoform dependent. The activation or inhibition of PKC by polyphenols has been found to be dependent on the presence of membrane, Ca(2+) ion, cofactors, cell and tissue types etc. Two polyphenols, curcumin and resveratrol are in clinical trials for the treatment of colon cancer. GENERAL SIGNIFICANCE The fact that 74% of the cancer drugs are derived from natural sources, naturally occurring polyphenols or its simple analogs with improved bioavailability may have the potential to be cancer drugs in the future.
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Affiliation(s)
- Joydip Das
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States.
| | - Rashmi Ramani
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
| | - M Olufemi Suraju
- Department of Pharmacological and Pharmaceutical Sciences, College of Pharmacy, University of Houston, Houston, TX 77204, United States
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Tobias IS, Newton AC. Protein Scaffolds Control Localized Protein Kinase Cζ Activity. J Biol Chem 2016; 291:13809-22. [PMID: 27143478 DOI: 10.1074/jbc.m116.729483] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/04/2016] [Indexed: 11/06/2022] Open
Abstract
Atypical protein kinase C (aPKC) isozymes modulate insulin signaling and cell polarity, but how their activity is controlled in cells is not well understood. These enzymes are constitutively phosphorylated, insensitive to second messengers, and have relatively low activity. Here we show that protein scaffolds not only localize but also differentially control the catalytic activity of the aPKC PKCζ, thus promoting activity toward localized substrates and restricting activity toward global substrates. Using cellular substrate readouts and scaffolded activity reporters in live cell imaging, we show that PKCζ has highly localized and differentially controlled activity on the scaffolds p62 and Par6. Both scaffolds tether aPKC in an active conformation as assessed through pharmacological inhibition of basal activity, monitored using a genetically encoded reporter for PKC activity. However, binding to Par6 is of higher affinity and is more effective in locking PKCζ in an active conformation. FRET-based translocation assays reveal that insulin promotes the association of both p62 and aPKC with the insulin-regulated scaffold IRS-1. Using the aPKC substrate MARK2 as another readout for activity, we show that overexpression of IRS-1 reduces the phosphorylation of MARK2 and enhances its plasma membrane localization, indicating sequestration of aPKC by IRS-1 away from MARK2. These results are consistent with scaffolds serving as allosteric activators of aPKCs, tethering them in an active conformation near specific substrates. Thus, signaling of these intrinsically low activity kinases is kept at a minimum in the absence of scaffolding interactions, which position the enzymes for stoichiometric phosphorylation of substrates co-localized on the same protein scaffold.
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Affiliation(s)
- Irene S Tobias
- From the Department of Pharmacology and Biomedical Sciences Graduate Program, University of California at San Diego, La Jolla, California 92093
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Molecular Control of Atypical Protein Kinase C: Tipping the Balance between Self-Renewal and Differentiation. J Mol Biol 2016; 428:1455-64. [PMID: 26992354 DOI: 10.1016/j.jmb.2016.03.003] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2015] [Revised: 02/20/2016] [Accepted: 03/03/2016] [Indexed: 01/05/2023]
Abstract
Complex organisms are faced with the challenge of generating and maintaining diverse cell types, ranging from simple epithelia to neurons and motile immune cells [1-3]. To meet this challenge, a complex set of regulatory pathways controls nearly every aspect of cell growth and function, including genetic and epigenetic programming, cytoskeleton dynamics, and protein trafficking. The far reach of cell fate specification pathways makes it particularly catastrophic when they malfunction, both during development and for tissue homeostasis in adult organisms. Furthermore, the therapeutic promise of stem cells derives from their ability to deftly navigate the multitude of pathways that control cell fate [4]. How the molecular components making up these pathways function to specify cell fate is beginning to become clear. Work from diverse systems suggests that the atypical Protein Kinase C (aPKC) is a key regulator of cell fate decisions in metazoans [5-7]. Here, we examine some of the diverse physiological outcomes of aPKC's function in differentiation, along with the molecular pathways that control aPKC and those that are responsive to changes in its catalytic activity.
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