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The Enigmatic Protein Kinase C-eta. Cancers (Basel) 2019; 11:cancers11020214. [PMID: 30781807 PMCID: PMC6406448 DOI: 10.3390/cancers11020214] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2019] [Revised: 02/04/2019] [Accepted: 02/10/2019] [Indexed: 01/02/2023] Open
Abstract
Protein kinase C (PKC), a multi-gene family, plays critical roles in signal transduction and cell regulation. Protein kinase C-eta (PKCη) is a unique member of the PKC family since its regulation is distinct from other PKC isozymes. PKCη was shown to regulate cell proliferation, differentiation and cell death. It was also shown to contribute to chemoresistance in several cancers. PKCη has been associated with several cancers, including renal cell carcinoma, glioblastoma, breast cancer, non-small cell lung cancer, and acute myeloid leukemia. However, mice lacking PKCη were more susceptible to tumor formation in a two-stage carcinogenesis model, and it is downregulated in hepatocellular carcinoma. Thus, the role of PKCη in cancer remains controversial. The purpose of this review article is to discuss how PKCη regulates various cellular processes that may contribute to its contrasting roles in cancer.
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2
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Ghosh T, Varshney A, Kumar P, Kaur M, Kumar V, Shekhar R, Devi R, Priyanka P, Khan MM, Saxena S. MicroRNA-874-mediated inhibition of the major G 1/S phase cyclin, CCNE1, is lost in osteosarcomas. J Biol Chem 2017; 292:21264-21281. [PMID: 29109143 DOI: 10.1074/jbc.m117.808287] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 10/24/2017] [Indexed: 01/26/2023] Open
Abstract
The tumor microenvironment is characterized by nutrient-deprived conditions in which the cancer cells have to adapt for survival. Serum starvation resembles the growth factor deprivation characteristic of the poorly vascularized tumor microenvironment and has aided in the discovery of key growth regulatory genes and microRNAs (miRNAs) that have a role in the oncogenic transformation. We report here that miR-874 down-regulates the major G1/S phase cyclin, cyclin E1 (CCNE1), during serum starvation. Because the adaptation of cancer cells to the tumor microenvironment is vital for subsequent oncogenesis, we tested for miR-874 and CCNE1 interdependence in osteosarcoma cells. We observed that miR-874 inhibits CCNE1 expression in primary osteoblasts, but in aggressive osteosarcomas, miR-874 is down-regulated, leading to elevated CCNE1 expression and appearance of cancer-associated phenotypes. We established that loss of miR-874-mediated control of cyclin E1 is a general feature of osteosarcomas. The down-regulation of CCNE1 by miR-874 is independent of E2F transcription factors. Restoration of miR-874 expression impeded S phase progression, suppressing aggressive growth phenotypes, such as cell invasion, migration, and xenograft tumors, in nude mice. In summary, we report that miR-874 inhibits CCNE1 expression during growth factor deprivation and that miR-874 down-regulation in osteosarcomas leads to CCNE1 up-regulation and more aggressive growth phenotypes.
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Affiliation(s)
- Tanushree Ghosh
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Akhil Varshney
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Praveen Kumar
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Manpreet Kaur
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Vipin Kumar
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Ritu Shekhar
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Raksha Devi
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Priyanka Priyanka
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Md Muntaz Khan
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
| | - Sandeep Saxena
- From the National Institute of Immunology, Aruna Asaf Ali Marg, New Delhi-110067, India
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3
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PKCη is an anti-apoptotic kinase that predicts poor prognosis in breast and lung cancer. Biochem Soc Trans 2015; 42:1519-23. [PMID: 25399563 DOI: 10.1042/bst20140182] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
The successful treatment of cancer in a disseminated stage using chemotherapy is limited by the occurrence of drug resistance, often mediated by anti-apoptotic mechanisms. Thus the challenge is to pinpoint the underlying key factors and to develop therapies for their direct targeting. Protein kinase C (PKC) enzymes are promising candidates, as some PKCs were shown to be involved in regulation of apoptosis. Our studies and others have shown that PKCη is an anti-apoptotic kinase, able to confer protection on tumour cells against stress and chemotherapy. We have demonstrated that PKCη shuttles between the cytoplasm and the nucleus and that upon DNA damage is tethered at the nuclear membrane. The C1b domain mediates translocation of PKCη to the nuclear envelope and, similar to the full-length protein, could also confer protection against cell death. Furthermore, its localization in cell and nuclear membranes in breast cancer biopsies of neoadjuvant-treated breast cancer patients was an indicator for poor survival and a predictor for the effectiveness of treatment. PKCη is also a novel biomarker for poor prognosis in non-small-cell lung cancer (NSCLC). Thus PKCη presents a potential target for therapy where inhibition of its activity and/or translocation to membranes could interfere with the resistance to chemotherapy.
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4
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Ku BM, Yune YP, Lee ES, Hah YS, Park JY, Jeong JY, Lee DH, Cho GJ, Choi WS, Kang SS. PKCη Regulates the TGFβ3-induced Chondevrepogenic Differentiation of Human Mesenchymal Stem Cell. Dev Reprod 2015; 17:299-309. [PMID: 25949145 PMCID: PMC4382954 DOI: 10.12717/dr.2013.17.4.299] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2013] [Revised: 11/07/2013] [Accepted: 11/11/2013] [Indexed: 11/17/2022]
Abstract
Transforming growth factor (TGF) family is well known to induce the chondevrepogenic differentiation of mesenchymal stem cells (MSC). However, the precise signal transduction pathways and underlying factors are not well known. Thus the present study aims to evaluate the possible role of C2 domain in the chondevrepogenic differentiation of human mesenchymal stem cells. To this end, 145 C2 domains in the adenovirus were individually transfected to hMSC, and morphological changes were examined. Among 145 C2 domains, C2 domain of protein kinase C eta (PKCη) was selected as a possible chondevrepogenic differentiation factor for hMSC. To confirm this possibility, we treated TGFβ3, a well known chondevrepogenic differentiation factor of hMSC, and examined the increased-expression of glycosaminoglycan (GAG), collagen type II (COL II) as well as PKCη using PT-PCR, immunocytochemistry and Western blot analysis. To further evaluation of C2 domain of PKCη, we examined morphological changes, expressions of GAG and COL II after transfection of PKCη -C2 domain in hMSC. Overexpression of PKCη-C2 domain induced morphological change and increased GAG and COL II expressions. The present results demonstrate that PKCη involves in the TGF-β3-induced chondevrepogenic differentiation of hMSC, and C2 domain of PKCη has important role in this process.
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Affiliation(s)
- Bo Mi Ku
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Young Phil Yune
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Eun Shin Lee
- Department of Rehabilitation Medicine, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Young-Sool Hah
- Clinical Research Institute, Gyeongsang National University Hospital, Jinju 660-702, Republic of Korea
| | - Jae Yong Park
- Dept. of Physiology, School of Medicine, Gyeongsang National University, Jinju 660-751, Republic of Korea
| | - Joo Yeon Jeong
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Dong Hoon Lee
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Gyeong Jae Cho
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Wan Sung Choi
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
| | - Sang Soo Kang
- Department of Anatomy & Neurobiology, Institute of Health Sciences, School of Medicine, Gyeongsang National University, Jinju 660-290, Republic of Korea
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5
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Zurgil U, Ben-Ari A, Atias K, Isakov N, Apte R, Livneh E. PKCη promotes senescence induced by oxidative stress and chemotherapy. Cell Death Dis 2014; 5:e1531. [PMID: 25412309 PMCID: PMC4260739 DOI: 10.1038/cddis.2014.481] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2014] [Revised: 10/06/2014] [Accepted: 10/09/2014] [Indexed: 12/21/2022]
Abstract
Senescence is characterized by permanent cell-cycle arrest despite continued viability and metabolic activity, in conjunction with the secretion of a complex mixture of extracellular proteins and soluble factors known as the senescence-associated secretory phenotype (SASP). Cellular senescence has been shown to prevent the proliferation of potentially tumorigenic cells, and is thus generally considered a tumor suppressive process. However, some SASP components may act as pro-tumorigenic mediators on premalignant cells in the microenvironment. A limited number of studies indicated that protein kinase C (PKC) has a role in senescence, with different isoforms having opposing effects. It is therefore important to elucidate the functional role of specific PKCs in senescence. Here we show that PKCη, an epithelial specific and anti-apoptotic kinase, promotes senescence induced by oxidative stress and DNA damage. We further demonstrate that PKCη promotes senescence through its ability to upregulate the expression of the cell cycle inhibitors p21Cip1 and p27Kip1 and enhance transcription and secretion of interleukin-6 (IL-6). Moreover, we demonstrate that PKCη creates a positive loop for reinforcing senescence by increasing the transcription of both IL-6 and IL-6 receptor, whereas the expression of IL-8 is specifically suppressed by PKCη. Thus, the presence/absence of PKCη modulates major components of SASP. Furthermore, we show that the human polymorphic variant of PKCη, 374I, that exhibits higher kinase activity in comparison to WT-374V, is also more effective in IL-6 secretion, p21Cip1 expression and the promotion of senescence, further supporting a role for PKCη in senescence. As there is now considerable interest in senescence activation/elimination to control tumor progression, it is first crucial to reveal the molecular regulators of senescence. This will improve our ability to develop new strategies to harness senescence as a potential cancer therapy in the future.
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Affiliation(s)
- U Zurgil
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - A Ben-Ari
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - K Atias
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - N Isakov
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - R Apte
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
| | - E Livneh
- The Shraga Segal Department of Microbiology Immunology and Genetics, Faculty of Health Sciences, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
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Park GB, Choi Y, Kim YS, Lee HK, Kim D, Hur DY. Silencing of PKCη induces cycle arrest of EBV(+) B lymphoma cells by upregulating expression of p38-MAPK/TAp73/GADD45α and increases susceptibility to chemotherapeutic agents. Cancer Lett 2014; 350:5-14. [PMID: 24784886 DOI: 10.1016/j.canlet.2014.04.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2013] [Revised: 03/28/2014] [Accepted: 04/21/2014] [Indexed: 01/01/2023]
Abstract
PKCη is involved in proliferation, differentiation, and drug resistance. However, PKCη function in EBV(+) B lymphoma remains poorly understood. Gene silencing of PKCη through siRNA knockdown inhibited cellular proliferation, induced cell cycle arrest in G0/G1 and G2/M phases, and sensitized cells to chemotherapeutic drugs. Upon PKCη knockdown, expression levels of p21, GADD45α, and TAp73 were all increased, whereas expression levels of CDK2, CDK4, CDK6, cyclin E, cyclin B1, and cdc2 were all downregulated. PKCη silencing also activated p38-MAPK, which in turn contributed to the expression of cell cycle arrest-related molecules. These results suggest that siRNA-mediated silencing of PKCη can be a potent tool to complement existing chemotherapy regimens for treating EBV(+) B lymphoma.
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Affiliation(s)
- Ga Bin Park
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Yunock Choi
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Yeong-Seok Kim
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Hyun-Kyung Lee
- Department of Internal Medicine, Inje University Busan Paik Hospital, Busan 614-735, Republic of Korea
| | - Daejin Kim
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea
| | - Dae Young Hur
- Department of Anatomy and Research Center for Tumor Immunology, Inje University College of Medicine, Busan 614-735, Republic of Korea.
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7
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Karp G, Abu-Ghanem S, Novack V, Mermershtain W, Ariad S, Sion-Vardy N, Livneh E. Localization of PKCη in cell membranes as a predictor for breast cancer response to treatment. ACTA ACUST UNITED AC 2012; 35:260-6. [PMID: 22868505 DOI: 10.1159/000338443] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
BACKGROUND Successful treatment of breast cancer is frequently limited by the resistance of tumors to chemotherapy. Recent studies suggested a role for protein kinase C (PKC) in the resistance to chemotherapy. Here we used retrospective analysis of breast cancer biopsies of neoadjuvantly treated patients to investigate the correlation of PKC expression with aggressiveness and resistance to chemotherapy. PATIENTS AND METHODS Our cohort (n = 25) included patients with advanced and aggressive breast cancers, who underwent neoadjuvant therapy with the CAF regimen (cyclophosphamide, doxorubicin, fluorouracil). Core biopsies (pre-chemotherapy) and surgical biopsies of primary tumors and lymph node metastases (post-chemotherapy) were scored for PKCeta (PKCh) and PKCepsilon (PKCe) expression in the cytoplasm, cell membrane, nuclear membrane, and the nucleus. RESULTS Our results showed increased expression of PKCh (not PKCe) in the cytoplasm and cell membranes of post-chemotherapy biopsies (p = 0.03). PKCh presence in cell membranes, indicating activation, was in correlation with poor survival (p = 0.007). CONCLUSION PKCh staining in cell and nuclear membranes is an indicator for poor survival and a predictor for the effectiveness of neoadjuvant treatment. Other avenues of treatment should be considered for these patients. PKCh presents a target for therapy where inhibition of its activity and/or translocation to membranes could interfere with the resistance to chemotherapy.
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Affiliation(s)
- Galia Karp
- The Shraga Segal Department of Microbiology and Immunology, Faculty of Health Sciences, Ben Gurion University, Beer Sheva, Israel
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8
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Shahaf G, Rotem-Dai N, Koifman G, Raveh-Amit H, Frost SA, Livneh E. PKCη is a negative regulator of AKT inhibiting the IGF-I induced proliferation. Exp Cell Res 2012; 318:789-99. [PMID: 22305966 DOI: 10.1016/j.yexcr.2012.01.018] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2010] [Revised: 01/16/2012] [Accepted: 01/17/2012] [Indexed: 10/14/2022]
Abstract
The PI3K-AKT pathway is frequently activated in human cancers, including breast cancer, and its activation appears to be critical for tumor maintenance. Some malignant cells are dependent on activated AKT for their survival; tumors exhibiting elevated AKT activity show sensitivity to its inhibition, providing an Achilles heel for their treatment. Here we show that the PKCη isoform is a negative regulator of the AKT signaling pathway. The IGF-I induced phosphorylation on Ser473 of AKT was inhibited by the PKCη-induced expression in MCF-7 breast adenocarcinoma cancer cells. This was further confirmed in shRNA PKCη-knocked-down MCF-7 cells, demonstrating elevated phosphorylation on AKT Ser473. While PKCη exhibited negative regulation on AKT phosphorylation it did not alter the IGF-I induced ERK phosphorylation. However, it enhanced ERK phosphorylation when stimulated by PDGF. Moreover, its effects on IGF-I/AKT and PDGF/ERK pathways were in correlation with cell proliferation. We further show that both PKCη and IGF-I confer protection against UV-induced apoptosis and cell death having additive effects. Although the protective effect of IGF-I involved activation of AKT, it was not affected by PKCη expression, suggesting that PKCη acts through a different route to increase cell survival. Hence, our studies show that PKCη provides negative control on AKT pathway leading to reduced cell proliferation, and further suggest that its presence/absence in breast cancer cells will affect cell death, which could be of therapeutic value.
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Affiliation(s)
- Galit Shahaf
- The Shraga Segal department of Microbiology and Immunology, Faculty of Health Science and the Cancer Research Center, Ben Gurion University of the Negev, Beer Sheva 84105, Israel
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9
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DNA damage targets PKCη to the nuclear membrane via its C1b domain. Exp Cell Res 2011; 317:1465-75. [PMID: 21514295 DOI: 10.1016/j.yexcr.2011.03.021] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Revised: 03/10/2011] [Accepted: 03/31/2011] [Indexed: 11/23/2022]
Abstract
Translocation to cellular membranes is one of the hallmarks of PKC activation, occurring as a result of the generation of lipid secondary messengers in target membrane compartments. The activation-induced translocation of PKCs and binding to membranes is largely directed by their regulatory domains. We have previously reported that PKCη, a member of the novel subfamily and an epithelial specific isoform, is localized at the cytoplasm and ER/Golgi and is translocated to the plasma membrane and the nuclear envelope upon short-term activation by PMA. Here we show that PKCη is shuttling between the cytoplasm and the nucleus and that upon etoposide induced DNA damage is tethered at the nuclear envelope. Although PKCη expression and its phosphorylation on the hydrophobic motif (Ser675) are increased by etoposide, this phosphorylation is not required for its accumulation at the nuclear envelope. Moreover, we demonstrate that the C1b domain is sufficient for translocation to the nuclear envelope. We further show that, similar to full-length PKCη, the C1b domain could also confer protection against etoposide-induced cell death. Our studies demonstrate translocation of PKCη to the nuclear envelope, and suggest that its spatial regulation could be important for its cellular functions including effects on cell death.
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10
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Translational control of protein kinase Ceta by two upstream open reading frames. Mol Cell Biol 2009; 29:6140-8. [PMID: 19797084 DOI: 10.1128/mcb.01044-09] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Protein kinase C (PKC) represents a family of serine/threonine kinases that play a central role in the regulation of cell growth, differentiation, and transformation. Posttranslational control of the PKC isoforms and their activation have been extensively studied; however, not much is known about their translational regulation. Here we report that the expression of one of the PKC isoforms, PKCeta, is regulated at the translational level both under normal growth conditions and during stress imposed by amino acid starvation, the latter causing a marked increase in its protein levels. The 5' untranslated region (5' UTR) of PKCeta is unusually long and GC rich, characteristic of many oncogenes and growth regulatory genes. We have identified two conserved upstream open reading frames (uORFs) in its 5' UTR and show their effect in suppressing the expression of PKCeta in MCF-7 growing cells. While the two uORFs function as repressive elements that maintain low basal levels of PKCeta in growing cells, they are required for its enhanced expression upon amino acid starvation. We show that the translational regulation during stress involves leaky scanning and is dependent on eIF-2alpha phosphorylation by GCN2. Our work further suggests that translational regulation could provide an additional level for controlling the expression of PKC family members, being more common than currently recognized.
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Rotem-Dai N, Oberkovitz G, Abu-Ghanem S, Livneh E. PKCη confers protection against apoptosis by inhibiting the pro-apoptotic JNK activity in MCF-7 cells. Exp Cell Res 2009; 315:2616-23. [DOI: 10.1016/j.yexcr.2009.06.004] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2009] [Revised: 05/31/2009] [Accepted: 06/04/2009] [Indexed: 12/17/2022]
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Breitkreutz D, Braiman-Wiksman L, Daum N, Denning MF, Tennenbaum T. Protein kinase C family: on the crossroads of cell signaling in skin and tumor epithelium. J Cancer Res Clin Oncol 2007; 133:793-808. [PMID: 17661083 DOI: 10.1007/s00432-007-0280-3] [Citation(s) in RCA: 99] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2006] [Accepted: 07/03/2007] [Indexed: 12/28/2022]
Abstract
The protein kinase C (PKC) family represents a large group of phospholipid dependent enzymes catalyzing the covalent transfer of phosphate from ATP to serine and threonine residues of proteins. Phosphorylation of the substrate proteins induces a conformational change resulting in modification of their functional properties. The PKC family consists of at least ten members, divided into three subgroups: classical PKCs (alpha, betaI, betaII, gamma), novel PKCs (delta, epsilon, eta, theta), and atypical PKCs (zeta, iota/lambda). The specific cofactor requirements, tissue distribution, and cellular compartmentalization suggest differential functions and fine tuning of specific signaling cascades for each isoform. Thus, specific stimuli can lead to differential responses via isoform specific PKC signaling regulated by their expression, localization, and phosphorylation status in particular biological settings. PKC isoforms are activated by a variety of extracellular signals and, in turn, modify the activities of cellular proteins including receptors, enzymes, cytoskeletal proteins, and transcription factors. Accordingly, the PKC family plays a central role in cellular signal processing. Accumulating data suggest that various PKC isoforms participate in the regulation of cell proliferation, differentiation, survival and death. These findings have enabled identification of abnormalities in PKC isoform function, as they occur in several cancers. Specifically, the initiation of squamous cell carcinoma formation and progression to the malignant phenotype was found to be associated with distinct changes in PKC expression, activation, distribution, and phosphorylation. These studies were recently further extended to transgenic and knockout animals, which allowed a more direct analysis of individual PKC functions. Accordingly, this review is focused on the involvement of PKC in physiology and pathology of the skin.
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Affiliation(s)
- D Breitkreutz
- Division of Differentiation and Carcinogenesis (A080/A110), German Cancer Research Center (DKFZ), POB 101949, Im Neuenheimer Feld 280, 69009, Heidelberg, Germany.
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13
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Karp G, Maissel A, Livneh E. Hormonal regulation of PKC: Estrogen up-regulates PKCη expression in estrogen-responsive breast cancer cells. Cancer Lett 2007; 246:173-81. [PMID: 16580129 DOI: 10.1016/j.canlet.2006.02.012] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2005] [Revised: 02/08/2006] [Accepted: 02/17/2006] [Indexed: 11/24/2022]
Abstract
Protein kinase C (PKC) is involved in several major signal transduction pathways that control gene expression cell growth and differentiation. The PKCeta isoform appears as a candidate regulator of mammary gland proliferation or differentiation, as its expression is up-regulated in the mammary gland in the transit from resting to the pregnant state. The purpose of this study was to examine the hormonal regulation of PKCeta. Here we show that estradiol specifically up-regulates the expression of PKCeta in the estrogen-responsive lines MCF-7 and T47D but not in the estrogen non-responsive line MDA-MB 231. Interestingly, the presence of progesterone, involved in the differentiation of the mammary gland, reduced the estrogen-induced PKCeta expression in a time-dependent manner. Thus, our studies suggest that PKCeta has an important role in signalling pathways regulating mammary gland proliferation and its development.
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Affiliation(s)
- Galia Karp
- Department of Microbiology and Immunology, Faculty of Health Sciences and the Cancer Research Center, Ben Gurion University, 84105 Beer Sheva, Israel
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14
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Maissel A, Marom M, Shtutman M, Shahaf G, Livneh E. PKCeta is localized in the Golgi, ER and nuclear envelope and translocates to the nuclear envelope upon PMA activation and serum-starvation: C1b domain and the pseudosubstrate containing fragment target PKCeta to the Golgi and the nuclear envelope. Cell Signal 2005; 18:1127-39. [PMID: 16242915 DOI: 10.1016/j.cellsig.2005.09.003] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2005] [Accepted: 09/09/2005] [Indexed: 11/27/2022]
Abstract
Protein kinase C (PKC) represents a family of serin/threonine kinases, playing a central role in the regulation of cell growth, differentiation and transformation. These enzymes differ in their primary structure, biochemical properties, tissue distribution and subcellular localization. The specific cellular functions of PKC isoforms are largely controlled by their localization. PKCeta, a member of the novel subfamily, is expressed predominantly in epithelial tissues. However, not much is known with respect to its mechanism of activation and regulation. Our recent studies suggest its role in cell cycle control. Here we show that PKCeta is localized at the Golgi apparatus, ER and the nuclear envelope. Furthermore, using GFP-fusion proteins of the different functional domains of PKCeta we deciphered the specific structural domains of the protein responsible for its apparent localization. We show that the cysteine-rich repeat C1b is responsible for its Golgi localization, while for its presence at the ER/nuclear envelope the pseudosubstrate containing fragment coupled to the C1 domain is required. In response to short-term activation by PMA we show translocation of PKCeta to the plasma membrane and the nuclear envelope. We demonstrate that the C1b is sufficient for its translocation to the plasma membrane. Interestingly, accumulation of PKCeta at the nuclear envelope also occurred in response to serum-starvation. It should be noted that interaction of PKCeta with the cyclin E/Cdk2 complex at the perinuclear region was recently reported by us in response to serum-starvation. Thus, our studies demonstrate translocation of PKCeta to the nuclear envelope, and suggest that the spatial regulation of PKCeta could be important for its cellular functions including effects on cell cycle control and involvement in tumor promotion.
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Affiliation(s)
- Adva Maissel
- Department of Microbiology and Immunology, Faculty of Health Sciences and the Cancer Research Center, Ben Gurion University, Beer Sheva 84105, Israel
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15
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Matos P, Jordan P. Expression of Rac1b stimulates NF-kappaB-mediated cell survival and G1/S progression. Exp Cell Res 2005; 305:292-9. [PMID: 15817154 DOI: 10.1016/j.yexcr.2004.12.029] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2004] [Revised: 12/10/2004] [Accepted: 12/16/2004] [Indexed: 10/25/2022]
Abstract
The small GTPase Rac1 can stimulate various signaling pathways following a tightly controlled GDP-GTP exchange. A splicing variant designated Rac1b was found to exist predominantly in the active GTP-bound state but the functional consequences of its expression remain unknown. Here we used mouse fibroblasts as a model to assess the signaling properties of Rac1b. We show that, in contrast to Rac1, expression of wild-type Rac1b is sufficient to stimulate cyclin D1 accumulation and G1/S progression in these cells. Moreover, expression of wild-type Rac1b, but not of wild-type Rac1, dramatically increased cell survival in the presence of only minimal growth stimuli. Both cellular responses were blocked by the NF-kappaB super-repressor IkappaBalpha(A32A36). Active Rac1b induced the phosphorylation and membrane translocation of IkappaBalpha, a prerequisite for the activation of NF-kappaB. These data demonstrate that Rac1b is a highly active Rac1 variant that stimulates cell cycle progression and cell survival in pathways involving NF-kappaB.
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Affiliation(s)
- Paulo Matos
- Centro de Genética Humana, Instituto Nacional de Saúde Dr. Ricardo Jorge, Avenida Padre Cruz, 1649-016 Lisboa, Portugal
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Kapoor GS, Kapitonov D, O'Rourke DM. Transcriptional Regulation of Signal Regulatory Protein α1 Inhibitory Receptors by Epidermal Growth Factor Receptor Signaling. Cancer Res 2004; 64:6444-52. [PMID: 15374953 DOI: 10.1158/0008-5472.can-04-0256] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Signal regulatory protein (SIRP) alpha1 is a membrane glycoprotein and a member of the SIRP receptor family. These transmembrane receptors have been shown to exert negative effects on signal transduction by receptor tyrosine kinases via immunoreceptor tyrosine-based inhibitory motifs in the carboxyl domain. Previous work has demonstrated that SIRPs negatively regulate many signaling pathways leading to reduction in tumor migration, survival, and cell transformation. Thus, modulation of SIRP expression levels or activity could be of great significance in the field of cancer therapy. The aim of the present study was to determine the factors that regulate levels of SIRPalpha1 in human glioblastoma cells that frequently overexpress the epidermal growth factor receptor (EGFR) because SIRPs have been shown to negatively regulate EGFR signaling. Northern blot analysis and immunoprecipitation assays showed variable expression levels of endogenous SIRPalpha transcripts in nine well-characterized glioblastoma cell lines. We examined SIRPalpha1 regulation in U87MG and U373MG cells in comparison with clonal derivatives that express a truncated form of erbB2, which negatively regulates EGFR signaling by inducing the formation of nonfunctional heterodimeric complexes. Mutant erbB2-expressing cells contained more SIRPalpha1 mRNA when compared with the parental cells in presence or absence of serum. Similarly, immunoprecipitation assays showed increased SIRPalpha1 protein levels in erbB-inhibited cells when compared with parental cells. Messenger RNA stability assays revealed that the increased mRNA levels in EGFR-inhibited cells were due to an induction of transcription. Consistent with this finding, expression of the erbB2 mutant receptor up-regulated SIRPalpha1 promoter activity in all cell lines tested. Interestingly, pharmacological inhibition of the kinase activities of EGFR, erbB2, and src and activation of mitogen-activated protein kinase, but not phosphatidylinositol 3'-kinase, significantly up-regulated SIRPalpha1 promoter activity. Based on these observations, we hypothesize that down-modulation of EGFR signaling leads to transcriptional up-regulation of the inhibitory SIRPalpha1 gene. These data may be important in the application of erbB-inhibitory strategies and for design of therapies for the treatment of glial tumors and other epithelial malignancies.
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MESH Headings
- Antigens, Differentiation/biosynthesis
- Antigens, Differentiation/genetics
- Antigens, Differentiation/physiology
- Cell Line, Tumor
- ErbB Receptors/physiology
- Gene Expression Regulation, Neoplastic
- Glioblastoma/genetics
- Glioblastoma/metabolism
- Humans
- Membrane Glycoproteins/antagonists & inhibitors
- Membrane Glycoproteins/biosynthesis
- Membrane Glycoproteins/genetics
- Membrane Glycoproteins/physiology
- Mitogen-Activated Protein Kinases/antagonists & inhibitors
- Neural Cell Adhesion Molecule L1/antagonists & inhibitors
- Neural Cell Adhesion Molecule L1/biosynthesis
- Neural Cell Adhesion Molecule L1/genetics
- Neural Cell Adhesion Molecule L1/physiology
- Oncogene Proteins v-erbB/antagonists & inhibitors
- Phosphoinositide-3 Kinase Inhibitors
- Promoter Regions, Genetic
- RNA, Messenger/biosynthesis
- RNA, Messenger/genetics
- Receptors, Immunologic/antagonists & inhibitors
- Receptors, Immunologic/biosynthesis
- Receptors, Immunologic/genetics
- Receptors, Immunologic/physiology
- Signal Transduction/physiology
- Transcriptional Activation
- Transfection
- Up-Regulation
- src-Family Kinases/antagonists & inhibitors
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Affiliation(s)
- Gurpreet S Kapoor
- Department of Neurosurgery, University of Pennsylvania School of Medicine, Philadelphia, Pennsylvania 19104, USA
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Alisi A, Spagnuolo S, Napoletano S, Spaziani A, Leoni S. Thyroid hormones regulate DNA-synthesis and cell-cycle proteins by activation of PKC? and p42/44 MAPK in chick embryo hepatocytes. J Cell Physiol 2004; 201:259-65. [PMID: 15334660 DOI: 10.1002/jcp.20060] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The molecular mechanism by which thyroid hormones exert their effects on cell growth is still unknown. In this study, we used chick embryo hepatocytes at different stages of development as a model to investigate the effect of the two thyroid hormones, T3 and T4, and of their metabolite T2, on the control of cell proliferation. We observed that T2 provokes increase of DNA-synthesis as well as T3 and T4, independently of developmental stage. We found that this stimulatory effect on the S phase is reverted by specific inhibitors of protein kinase C (PKC) and p42/44 mitogen-activated protein kinase (p42/44 MAPK), Ro 31-8220 or PD 98059. Furthermore, the treatment with thyroid hormones induces the activation of PKCalpha and p42/44 MAPK, suggesting their role as possible downstream mediators of cell response mediated by thyroid hormones. The increase of DNA-synthesis is well correlated with the increased levels of cyclin D1 and cdk4 that control the G1 phase, and also with the activities of cell-cycle proteins involved in the G1 to S phase progression, such as cyclin E/A-cdk2 complexes. Interestingly, the activity of cyclin-cdk2 complexes is strongly repressed in the presence of PKC and p42/44 MAPK inhibitors. In conclusion, we demonstrated that the thyroid hormones could modulate different signaling pathways that are able to control cell-cycle progression, mainly during G1/S transition.
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Affiliation(s)
- A Alisi
- Department of Cellular and Developmental Biology, University La Sapienza, Roma, Italy
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