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Tu-Sekine B, Goldschmidt HL, Raben DM. DGK-θ: Structure, Enzymology, and Physiological Roles. Front Cell Dev Biol 2016; 4:101. [PMID: 27683659 PMCID: PMC5021689 DOI: 10.3389/fcell.2016.00101] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2016] [Accepted: 08/29/2016] [Indexed: 12/13/2022] Open
Abstract
Diacylglycerol kinases (DGKs) are a family of enzymes that catalyze the ATP-dependent phosphorylation of diacylglycerol (DAG) to phosphatidic acid (PtdOH). The recognition of the importance of these enzymes has been increasing ever since it was determined that they played a role in the phosphatidylinositol (PtdIns) cycle and a number of excellent reviews have already been written [(see van Blitterswijk and Houssa, 2000; Kanoh et al., 2002; Mérida et al., 2008; Tu-Sekine and Raben, 2009, 2011; Shulga et al., 2011; Tu-Sekine et al., 2013) among others]. We now know there are ten mammalian DGKs that are organized into five classes. DGK-θ is the lone member of the Type V class of DGKs and remains as one of the least studied. This review focuses on our current understanding of the structure, enzymology, regulation, and physiological roles of this DGK and suggests some future areas of research to understand this DGK isoform.
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Affiliation(s)
- Becky Tu-Sekine
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Hana L Goldschmidt
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine Baltimore, MD, USA
| | - Daniel M Raben
- Department of Biological Chemistry, The Johns Hopkins University School of Medicine Baltimore, MD, USA
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Dong H, Wang C, Lu S, Yu C, Huang L, Feng W, Xu H, Chen X, Zen K, Yan Q, Liu W, Zhang C, Zhang CY. A panel of four decreased serum microRNAs as a novel biomarker for early Parkinson's disease. Biomarkers 2015; 21:129-37. [PMID: 26631297 DOI: 10.3109/1354750x.2015.1118544] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
CONTEXT Sensitive, non-invasive biomarkers that facilitate Parkinson's disease (PD) detection and stage assignment are currently unavailable. OBJECTIVE The objective of this study is to investigate the potential of circulating microRNAs (miRNAs) as novel biomarkers for PD. MATERIALS AND METHODS Solexa sequencing technology and quantitative real-time PCR were applied to screen and verify altered serum miRNAs in PD patients. RESULTS Serum miR-141, miR-214, miR-146b-5p, and miR-193a-3p were decreased significantly in PD patients compared with controls. Furthermore, the 4-miRNA panel enabled the differentiation of HY stage 1 and 2 PD patients from controls. DISCUSSION AND CONCLUSION The four serum miRNAs may represent novel biomarkers for the early detection of PD.
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Affiliation(s)
- Hui Dong
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
| | - Cheng Wang
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China .,b Department of Clinical Laboratory , Jinling Hospital, Nanjing University School of Medicine , Nanjing , China , and
| | - Sunbin Lu
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
| | - Cuiyu Yu
- c Department of Neurology , Affiliated Brain Hospital of Nanjing Medical University , Nanjing , China
| | - Lei Huang
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
| | - Wuruo Feng
- c Department of Neurology , Affiliated Brain Hospital of Nanjing Medical University , Nanjing , China
| | - Hui Xu
- c Department of Neurology , Affiliated Brain Hospital of Nanjing Medical University , Nanjing , China
| | - Xi Chen
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
| | - Ke Zen
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
| | - Qiao Yan
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
| | - Weiguo Liu
- c Department of Neurology , Affiliated Brain Hospital of Nanjing Medical University , Nanjing , China
| | - Chunni Zhang
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China .,b Department of Clinical Laboratory , Jinling Hospital, Nanjing University School of Medicine , Nanjing , China , and
| | - Chen-Yu Zhang
- a State Key Laboratory of Pharmaceutical Biotechnology, Nanjing Advanced Institute for Life Sciences, Nanjing University School of Life Sciences, Jiangsu Engineering Research Center for MicroRNA Biology and Biotechnology, Nanjing University , Nanjing , China
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Cai K, Lucki NC, Sewer MB. Silencing diacylglycerol kinase-theta expression reduces steroid hormone biosynthesis and cholesterol metabolism in human adrenocortical cells. Biochim Biophys Acta Mol Cell Biol Lipids 2013; 1841:552-62. [PMID: 24369117 DOI: 10.1016/j.bbalip.2013.12.005] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2013] [Revised: 12/10/2013] [Accepted: 12/13/2013] [Indexed: 11/29/2022]
Abstract
Diacylglycerol kinase theta (DGKθ) plays a pivotal role in regulating adrenocortical steroidogenesis by synthesizing the ligand for the nuclear receptor steroidogenic factor 1 (SF1). In response to activation of the cAMP signaling cascade nuclear DGK activity is rapidly increased, facilitating PA-mediated, SF1-dependent transcription of genes required for cortisol and dehydroepiandrosterone (DHEA) biosynthesis. Based on our previous work identifying DGKθ as the enzyme that produces the agonist for SF1, we generated a tetracycline-inducible H295R stable cell line to express a short hairpin RNA (shRNA) against DGKθ and characterized the effect of silencing DGKθ on adrenocortical gene expression. Genome-wide DNA microarray analysis revealed that silencing DGKθ expression alters the expression of multiple genes, including steroidogenic genes, nuclear receptors and genes involved in sphingolipid, phospholipid and cholesterol metabolism. Interestingly, the expression of sterol regulatory element binding proteins (SREBPs) was also suppressed. Consistent with the suppression of SREBPs, we observed a down-regulation of multiple SREBP target genes, including 3-hydroxy-3-methylglutary coenzyme A reductase (HMG-CoA red) and CYP51, concomitant with a decrease in cellular cholesterol. DGKθ knockdown cells exhibited a reduced capacity to metabolize PA, with a down-regulation of lipin and phospholipase D (PLD) isoforms. In contrast, suppression of DGKθ increased the expression of several genes in the sphingolipid metabolic pathway, including acid ceramidase (ASAH1) and sphingosine kinases (SPHK). In summary, these data demonstrate that DGKθ plays an important role in steroid hormone production in human adrenocortical cells.
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Affiliation(s)
- Kai Cai
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Natasha C Lucki
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA
| | - Marion B Sewer
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.
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Ueda S, Tu-Sekine B, Yamanoue M, Raben DM, Shirai Y. The expression of diacylglycerol kinase theta during the organogenesis of mouse embryos. BMC DEVELOPMENTAL BIOLOGY 2013; 13:35. [PMID: 24079595 PMCID: PMC3850696 DOI: 10.1186/1471-213x-13-35] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2013] [Accepted: 09/27/2013] [Indexed: 12/11/2022]
Abstract
Background Diacylglycerol kinase (DGK) is a key enzyme that regulates diacylglycerol (DG) turnover and is involved in a variety of physiological functions. The isoform DGKθ has a unique domain structure and is the sole member of type V DGK. To reveal the spatial and temporal expression of DGKθ we performed immunohistochemical staining on paraffin sections of mouse embryos. Results At an early stage of development (E10.5 and 11.5), the expression of DGKθ was prominently detected in the brain, spinal cord, dorsal root ganglion, and limb bud, and was also moderately detected in the bulbus cordis and the primordium of the liver and gut. At later stages (E12.5 and 14.5), DGKθ expression persisted or increased in the neocortex, epithalamus, hypothalamus, medulla oblongata, and pons. DGKθ was also evident in the epidermis, and nearly all epithelia of the oropharyngeal membrane, digestive tract, and bronchea. At prenatal developmental stages (E16.5 and E18.5), the expression pattern of DGKθ was maintained in the central nervous system, intestine, and kidney, but was attenuated in the differentiated epidermis. Conclusion These results suggest that DGKθ may play important physiological roles not only in the brain, but also in diverse organs and tissues during the embryonic stages.
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Affiliation(s)
- Shuji Ueda
- Department of Agrobioscience, Graduate School of Agricultural Science, Kobe University, Kobe, Hyogo, Japan.
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Cai K, Sewer MB. cAMP-stimulated transcription of DGKθ requires steroidogenic factor 1 and sterol regulatory element binding protein 1. J Lipid Res 2013; 54:2121-2132. [PMID: 23610160 DOI: 10.1194/jlr.m035634] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Diacylglycerol kinase (DGK)θ is a lipid kinase that phosphorylates diacylglycerol to form phosphatidic acid (PA). We have previously shown that PA is a ligand for the nuclear receptor steroidogenic factor 1 (SF1) and that cAMP-stimulated expression of SF1 target genes requires DGKθ. In this study, we sought to investigate the role of cAMP signaling in regulating DGKθ gene expression. Real time RT-PCR and Western blot analysis revealed that dibutyryl cAMP (Bt2cAMP) increased the mRNA and protein expression, respectively, of DGKθ in H295R human adrenocortical cells. SF1 and sterol regulatory element binding protein 1 (SREBP1) increased the transcriptional activity of a reporter plasmid containing 1.5 kb of the DGKθ promoter fused to the luciferase gene. Mutation of putative cAMP responsive sequences abolished SF1- and SREBP-dependent DGKθ reporter gene activation. Consistent with this finding, chromatin immunoprecipitation assay demonstrated that Bt2cAMP signaling increased the recruitment of SF1 and SREBP1 to the DGKθ promoter. Coimmunoprecipitation assay revealed that SF1 and SREBP1 interact, suggesting that the two transcription factors form a complex on the DGKθ promoter. Finally, silencing SF1 and SREBP1 abolished cAMP-stimulated DGKθ expression. Taken together, we demonstrate that SF1 and SREBP1 activate DGKθ transcription in a cAMP-dependent manner in human adrenocortical cells.
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Affiliation(s)
- Kai Cai
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093
| | - Marion B Sewer
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA 92093.
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Tong Q, Wang F, Zhou H, Sun H, Song H, Shu Y, Gong Y, Zhang W, Cai T, Yang F, Tang J, Jiang T. Structural and functional insights into lipid‐bound nerve growth factors. FASEB J 2012; 26:3811-21. [DOI: 10.1096/fj.12-207316] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Qiong Tong
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Feng Wang
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
- School of PharmacyGuangxi Medical UniversityNanningChina
| | - Hong‐Zhe Zhou
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Han‐Li Sun
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Hui Song
- School of PharmacyGuangxi Medical UniversityNanningChina
| | - Yu‐Yan Shu
- Snake Venom Research InstituteGuangxi Medical UniversityNanningChina
| | - Yong Gong
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Wen‐Ting Zhang
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Tan‐xi Cai
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Fu‐Quan Yang
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Jie Tang
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
| | - Tao Jiang
- National Key Laboratory of BiomacromoleculesInstitute of BiophysicsBeijingChina
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Abstract
Nuclear lipid metabolism is implicated in various processes, including transcription, splicing, and DNA repair. Sphingolipids play roles in numerous cellular functions, and an emerging body of literature has identified roles for these lipid mediators in distinct nuclear processes. Different sphingolipid species are localized in various subnuclear domains, including chromatin, the nuclear matrix, and the nuclear envelope, where sphingolipids exert specific regulatory and structural functions. Sphingomyelin, the most abundant nuclear sphingolipid, plays both structural and regulatory roles in chromatin assembly and dynamics in addition to being an integral component of the nuclear matrix. Sphingosine-1-phosphate modulates histone acetylation, sphingosine is a ligand for steroidogenic factor 1, and nuclear accumulation of ceramide has been implicated in apoptosis. Finally, nuclear membrane-associated ganglioside GM1 plays a pivotal role in Ca(2+) homeostasis. This review highlights research on the factors that control nuclear sphingolipid metabolism and summarizes the roles of these lipids in various nuclear processes.
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Affiliation(s)
- Natasha C Lucki
- School of Biology, Georgia Institute of Technology, Atlanta, Georgia 30332, USA
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Shulga YV, Topham MK, Epand RM. Regulation and functions of diacylglycerol kinases. Chem Rev 2011; 111:6186-208. [PMID: 21800853 DOI: 10.1021/cr1004106] [Citation(s) in RCA: 158] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Yulia V Shulga
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4K1, Canada
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Baldanzi G, Pietronave S, Locarno D, Merlin S, Porporato P, Chianale F, Filigheddu N, Cantelmo AR, Albini A, Graziani A, Prat M. Diacylglycerol kinases are essential for hepatocyte growth factor-dependent proliferation and motility of Kaposi's sarcoma cells. Cancer Sci 2011; 102:1329-36. [PMID: 21477072 DOI: 10.1111/j.1349-7006.2011.01953.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Hepatocyte growth factor (HGF) is involved in the pathogenesis of Kaposi's sarcoma (KS), the most frequent neoplasia in patients with AIDS, characterized by proliferating spindle cells, infiltrating inflammatory cells, angiogenesis, edema, and invasiveness. In vitro, this factor sustains the biological behavior of KS derived cells, after activation of its receptor and the downstream MAPK and AKT signals. In other cell types, namely endothelial and epithelial cells, movement, proliferation, and survival stimulated by HGF and other growth factors and cytokines depend on diacylglycerol kinases (DGK). In an effort to identify new intracellular transducers operative in KS cells, which could represent therapeutic targets, we investigated the role of DGK in KS cell movement and proliferation by treating cells with the DGK pharmacological inhibitor R59949. We report that R59949 strongly inhibits HGF-induced KS motility, proliferation, and anchorage-independent growth with only a partial effect on cell adhesion and spreading. R59949 does not affect cell survival, HGF receptor activation, or the classical MAPK and AKT signalling pathways. Furthermore, we carried out an siRNA screen to characterize the DGK isoforms involved in KS motility and anchorage independent growth. Our data indicate a strong involvement of DGK-δ in KS motility and of DGK-ι in anchorage-independent growth. These results indicate that DGK inhibition is sufficient to impair in vitro KS cell proliferation and movement and suggest that selected DGK represent new pharmacological targets to interfere with the malignant properties of KS, independently from the well-known RAS/MAPK and PI3K/AKT pathways.
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Affiliation(s)
- Gianluca Baldanzi
- Department of Experimental and Clinical Medicine, Università del Piemonte Orientale Amedeo Avogadro, Novara IRCCS Multimedica, Milan, Italy
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Negative regulation of diacylglycerol kinase theta mediates adenosine-dependent hepatocyte preconditioning. Cell Death Differ 2010; 17:1059-68. [PMID: 20057501 DOI: 10.1038/cdd.2009.210] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
In liver ischemic preconditioning (IP), stimulation of adenosine A2a receptors (A2aR) prevents ischemia/reperfusion injury by promoting diacylglycerol-mediated activation of protein kinase C (PKC). By concerting diacylglycerol to phosphatidic acid, diacylglycerol kinases (DGKs) act as terminator of diacylglycerol signalling. This study investigates the role of DGK in the development of hepatocyte IP. DGK activity and cell viability were evaluated in isolated rat hepatocytes preconditioned by 10 min hypoxia followed by 10 min re-oxygenation or by the treatment with the A2aR agonist, CGS21680, and subsequently exposed to prolonged hypoxia. We observed that after IP or A2aR activation, a decrease in DGK activity was associated with the onset of hepatocyte tolerance to hypoxia. CGS21680-induced stimulation of A2aR specifically inhibited DGK isoform theta by activating RhoA-GTPase. Consistently, both siRNA-mediated downregulation of DGK theta and hepatocyte pretreatment with the DGK inhibitor R59949 induced cell tolerance to hypoxia. The pharmacological inhibition of DGK was associated with the diacylglycerol-dependent activation of PKC delta and epsilon and of their downstream target p38 MAPK. In conclusion, we unveil a novel signalling pathway contributing to the onset of hepatocyte preconditioning, which through RhoA-GTPase, couples A2aR to the downregulation of DGK. Such an inhibition is essential for the sustained accumulation of diacylglycerol required for triggering PKC-mediated survival signals.
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Li D, Urs AN, Allegood J, Leon A, Merrill AH, Sewer MB. Cyclic AMP-stimulated interaction between steroidogenic factor 1 and diacylglycerol kinase theta facilitates induction of CYP17. Mol Cell Biol 2007; 27:6669-85. [PMID: 17664281 PMCID: PMC2099220 DOI: 10.1128/mcb.00355-07] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In the human adrenal cortex, adrenocorticotropin (ACTH) activates CYP17 transcription by promoting the binding of the nuclear receptor steroidogenic factor 1 (SF1) (Ad4BP, NR5A1) to the promoter. We recently found that sphingosine is an antagonist for SF1 and inhibits cyclic AMP (cAMP)-dependent CYP17 gene transcription. The aim of the current study was to identify phospholipids that bind to SF1 and to characterize the mechanism by which ACTH/cAMP regulates the biosynthesis of this molecule(s). Using tandem mass spectrometry, we show that in H295R human adrenocortical cells, SF1 is bound to phosphatidic acid (PA). Activation of the ACTH/cAMP signal transduction cascade rapidly increases nuclear diacylglycerol kinase (DGK) activity and PA production. PA stimulates SF1-dependent transcription of CYP17 reporter plasmids, promotes coactivator recruitment, and induces the mRNA expression of CYP17 and several other steroidogenic genes. Inhibition of DGK activity attenuates the binding of SF1 to the CYP17 promoter, and silencing of DGK-theta expression inhibits cAMP-dependent CYP17 transcription. LXXLL motifs in DGK-theta mediate a direct interaction of SF1 with the kinase and may facilitate binding of PA to the receptor. We conclude that ACTH/cAMP stimulates PA production in the nucleus of H295R cells and that this increase in PA concentrations facilitates CYP17 induction.
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Affiliation(s)
- Donghui Li
- School of Biology, Georgia Institute of Technology, Atlanta, GA 30332-0230, USA
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Goto K, Hozumi Y, Nakano T, Saino SS, Kondo H. Cell Biology and Pathophysiology of the Diacylglycerol Kinase Family: Morphological Aspects in Tissues and Organs. INTERNATIONAL REVIEW OF CYTOLOGY 2007; 264:25-63. [DOI: 10.1016/s0074-7696(07)64002-9] [Citation(s) in RCA: 68] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
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Evangelisti C, Riccio M, Faenza I, Zini N, Hozumi Y, Goto K, Cocco L, Martelli AM. Subnuclear localization and differentiation-dependent increased expression of DGK-zeta in C2C12 mouse myoblasts. J Cell Physiol 2006; 209:370-8. [PMID: 16897754 DOI: 10.1002/jcp.20744] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Diacylglycerol kinases (DGKs) catalyze phosphorylation of diacylglycerol (DG) to yield phosphatidic acid (PA). Previous evidence has shown that the nucleus contains several DGK isoforms. In this study, we have analyzed the expression and subnuclear localization of DGK-zeta employing C2C12 mouse myoblasts. Immunocytochemistry coupled to confocal laser scanning microscopy showed that both endogenous and green fluorescent protein-tagged overexpressed DGK-zeta localized mostly to the nucleus. In contrast, overexpressed DGK-alpha, -beta, -delta, and -iota did not migrate to the nucleus. DGK-zeta was present in the nuclear speckle domains, as also revealed by immuno-electron microscopy analysis. Moreover, DGK-zeta co-localized and interacted with phosphoinositide-specific phospholipase Cbeta1 (PLCbeta1), that is involved in inositide-dependent signaling pathways important for the regulation of cell proliferation and differentiation. Furthermore, we report that DGK-zeta associated with nuclear matrix, the fundamental organizing principle of the nucleus where many cell functions take place, including DNA replication, gene expression, and protein phosphorylation. Nuclear DGK-zeta increased during myogenic differentiation of C2C12 cells, while DGK-zeta down-regulation by siRNA markedly impaired differentiation. Overall, our findings further support the importance of speckles and nuclear matrix in lipid-dependent signaling and suggest that nuclear DGK-zeta might play some fundamental role during myogenic differentiation of C2C12 cells.
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Affiliation(s)
- Camilla Evangelisti
- Dipartimento di Scienze Anatomiche Umane e Fisiopatologia dell'Apparato Locomotore, Sezione di Anatomia, Università di Bologna, Bologna, Italy
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Abstract
Cytosolic Ca(2+) is a versatile secondary messenger that regulates a wide range of cellular activities. In the past decade, evidence has accumulated that free Ca(2+) within the nucleus also plays an important messenger function. Here we review the mechanisms and effects of Ca(2+) signals within the nucleus. In particular, evidence is reviewed that the nucleus contains the machinery necessary for production of inositol 1,4,5-trisphosphate and for inositol 1,4,5-trisphosphate receptor-mediated Ca(2+) release. The role of Ca(2+) signals within the nucleus is discussed including regulation of such critical cell functions as gene expression, activation of kinases, and permeability of nuclear pores.
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Affiliation(s)
- Dawidson A Gomes
- Department of Pharmacology, Federal University of Minas Gerais, Belo Horizonte, Brazil
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Abstract
Diacylglycerol kinases (DGKs) attenuate diacylglycerol signaling by converting this lipid to phosphatidic acid (PA). The nine mammalian DGKs that have been identified are widely expressed, but each isoform has a unique tissue and subcellular distribution. Their kinase activity is regulated by mechanisms that modify their access to diacylglycerol, directly affect their kinase activity, or alter their ability to bind to other proteins. In many cases, these enzymes regulate the activity of proteins that are modulated by either diacylglycerol or PA. Experiments using cultured cells and model organisms have demonstrated that DGKs have prominent roles in neuronal transmission, lymphocyte signaling, and carcinogenesis.
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Affiliation(s)
- Matthew K Topham
- Department of Internal Medicine, The Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope, Salt Lake City, UT 84112-5550, USA.
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