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The ubiquitination of CKIP-1 mediated by Src aggravates diabetic renal fibrosis (original article). Biochem Pharmacol 2022; 206:115339. [DOI: 10.1016/j.bcp.2022.115339] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Revised: 10/28/2022] [Accepted: 10/31/2022] [Indexed: 11/06/2022]
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2
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Ferreira A, Rivera A, Wohlgemuth JG, Dlott JS, Snyder LM, Alper SL, Romero JR. Dysregulated Erythroid Mg2+ Efflux in Type 2 Diabetes. Front Cell Dev Biol 2022; 10:861644. [PMID: 35445032 PMCID: PMC9013827 DOI: 10.3389/fcell.2022.861644] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2022] [Accepted: 03/09/2022] [Indexed: 12/23/2022] Open
Abstract
Hyperglycemia is associated with decreased Mg2+ content in red blood cells (RBC), but mechanisms remain unclear. We characterized the regulation of Mg2+ efflux by glucose in ex vivo human RBC. We observed that hemoglobin A1C (HbA1C) values correlated with Na+-dependent Mg2+ efflux (Na+/Mg2+ exchange) and inversely correlated with cellular Mg content. Treatment of cells with 50 mM D-glucose, but not with sorbitol, lowered total cellular Mg (2.2 ± 0.1 to 2.0 ± 0.1 mM, p < 0.01) and enhanced Na+/Mg2+ exchange activity [0.60 ± 0.09 to 1.12 ± 0.09 mmol/1013 cell × h (flux units, FU), p < 0.05]. In contrast, incubation with selective Src family kinase inhibitors PP2 or SU6656 reduced glucose-stimulated exchange activation (p < 0.01). Na+/Mg2+ exchange activity was also higher in RBC from individuals with type 2 diabetes (T2D, 1.19 ± 0.13 FU) than from non-diabetic individuals (0.58 ± 0.05 FU, p < 0.01). Increased Na+/Mg2+ exchange activity in RBC from T2D subjects was associated with lower intracellular Mg content. Similarly increased exchange activity was evident in RBC from the diabetic db/db mouse model as compared to its non-diabetic control (p < 0.03). Extracellular exposure of intact RBC from T2D subjects to recombinant peptidyl-N-glycosidase F (PNGase F) reduced Na+/Mg2+ exchange activity from 0.98 ± 0.14 to 0.59 ± 0.13 FU (p < 0.05) and increased baseline intracellular Mg content (1.8 ± 0.1 mM) to normal values (2.1 ± 0.1 mM, p < 0.05). These data suggest that the reduced RBC Mg content of T2D RBC reflects enhanced RBC Na+/Mg2+ exchange subject to regulation by Src family kinases and by the N-glycosylation state of one or more membrane proteins. The data extend our understanding of dysregulated RBC Mg2+ homeostasis in T2D.
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Affiliation(s)
- Ana Ferreira
- Interdisciplinary Centre of Social Sciences (CICS.NOVA), Faculty of Social Sciences and Humanities (NOVA FCSH), Lisbon, Portugal
| | - Alicia Rivera
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
- *Correspondence: Alicia Rivera,
| | | | | | | | - Seth L. Alper
- Department of Medicine, Beth Israel Deaconess Medical Center and Harvard Medical School, Boston, MA, United States
| | - Jose R. Romero
- Division of Endocrinology, Diabetes and Hypertension, Department of Medicine, Brigham and Women’s Hospital and Harvard Medical School, Boston, MA, United States
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3
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Takaishi K, Kinoshita H, Feng GG, Azma T, Kawahito S, Kitahata H. Cytoskeleton-disrupting agent cytochalasin B reduces oxidative stress caused by high glucose in the human arterial smooth muscle. J Pharmacol Sci 2020; 144:197-203. [PMID: 33070838 DOI: 10.1016/j.jphs.2020.08.004] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2020] [Revised: 08/01/2020] [Accepted: 08/19/2020] [Indexed: 12/15/2022] Open
Abstract
The role of cytoskeleton dynamics in the oxidative stress toward human vasculature has been unclear. The current study examined whether the cytoskeleton-disrupting agent cytochalasin B reduces oxidative stress caused by high glucose in the human arterial smooth muscle. All experiments in the human omental arteries without endothelium or the cultured human coronary artery smooth muscle cells were performed in d-glucose (5.5 mmol/L). The exposure toward d-glucose (20 mmol/L) for 60 min reduced the relaxation or hyperpolarization to an ATP sensitive K+ channel (KATP) opener levcromakalim (10-8 to 3 × 10-6 mol/L and 3 × 10-6 mol/L, respectively). Cytochalasin B and a superoxide inhibitor Tiron, restored them similarly. Cytochalasin B reduced the NADPH oxidase activity, leading to a decrease in superoxide levels of the arteries treated with high d-glucose. Also, cytochalasin B impaired the F-actin constitution and the membrane translocation of an NADPH oxidase subunit p47phox in artery smooth muscle cells treated with high d-glucose. A clinical concentration of cytochalasin B prevented human vascular smooth muscle malfunction via the oxidative stress caused by high glucose. Regulation of the cytoskeleton may be essential to keep the normal vascular function in patients with hyperglycemia.
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Affiliation(s)
- Kazumi Takaishi
- Department of Dental Anesthesiology, Tokushima University Hospital, Tokushima, Japan
| | - Hiroyuki Kinoshita
- Department of Anesthesiology, Tokushima University Hospital, Tokushima, Japan; Department of Anesthesiology, Aichi Medical University School of Medicine, Aichi, Japan.
| | - Guo-Gang Feng
- Department of Anesthesiology, Aichi Medical University School of Medicine, Aichi, Japan
| | - Toshiharu Azma
- Department of Anesthesiology & Pain Medicine, Kohnodai Hospital, National Center for Global Health and Medicine, Ichikawa, Japan
| | - Shinji Kawahito
- Department of Anesthesiology, Tokushima University Hospital, Tokushima, Japan
| | - Hiroshi Kitahata
- Department of Dental Anesthesiology, Tokushima University Hospital, Tokushima, Japan
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4
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Inhibition of TLR4 attenuates vascular dysfunction and oxidative stress in diabetic rats. J Mol Med (Berl) 2015; 93:1341-54. [DOI: 10.1007/s00109-015-1318-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/12/2015] [Revised: 06/24/2015] [Accepted: 06/26/2015] [Indexed: 10/23/2022]
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5
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Wright CR, Brown EL, Ward AC, Russell AP. G-CSF treatment can attenuate dexamethasone-induced reduction in C2C12 myotube protein synthesis. Cytokine 2015; 73:1-7. [PMID: 25689616 DOI: 10.1016/j.cyto.2015.01.012] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2014] [Revised: 01/20/2015] [Accepted: 01/21/2015] [Indexed: 01/27/2023]
Abstract
Granulocyte-colony stimulating factor (G-CSF) has been demonstrated to enhance skeletal muscle recovery following injury and increases muscle function in the context of neuromuscular disease in rodent models. However, understanding of the underlying mechanisms used by G-CSF to mediate these functions remains poor. G-CSF acts on responsive cells through binding to a specific membrane spanning receptor, G-CSFR. Recently identified, the G-CSFR is expressed in myoblasts, myotubes and mature skeletal muscle tissue. Therefore, elucidating the actions of G-CSF in skeletal muscle represents an important prerequisite to consider G-CSF as a therapeutic agent to treat skeletal muscle. Here we show for the first time that treatment with moderate doses (4 and 40ng/ml) of G-CSF attenuates the effects of dexamethasone in reducing protein synthesis in C2C12 myotubes. However, a higher dose (100ng/ml) of G-CSF exacerbates the dexamethasone-induced reduction in protein synthesis. In contrast, G-CSF had no effect on basal or dexamethasone-induced protein degradation, nor did G-CSF influence the phosphorylation of Akt, STAT3, Erk1/2, Src, Lyn and Erk5 in C2C12 myotubes. In conclusion, physiologically relevant doses of G-CSF may attenuate reduced skeletal muscle protein synthesis during catabolic conditions, thereby improving recovery.
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Affiliation(s)
- Craig R Wright
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Burwood 3125, Victoria, Australia
| | - Erin L Brown
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Burwood 3125, Victoria, Australia
| | - Alister C Ward
- Molecular and Medical Research SRC, School of Medicine, Deakin University, Waurn Ponds, 3216 Victoria, Australia
| | - Aaron P Russell
- Centre for Physical Activity and Nutrition, School of Exercise and Nutrition Sciences, Deakin University, Burwood 3125, Victoria, Australia.
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6
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Xie X, Lan T, Chang X, Huang K, Huang J, Wang S, Chen C, Shen X, Liu P, Huang H. Connexin43 mediates NF-κB signalling activation induced by high glucose in GMCs: involvement of c-Src. Cell Commun Signal 2013; 11:38. [PMID: 23718910 PMCID: PMC3699363 DOI: 10.1186/1478-811x-11-38] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2013] [Accepted: 05/10/2013] [Indexed: 12/23/2022] Open
Abstract
Background Nuclear factor kappa-B (NF-κB) signalling plays an important role in diabetic nephropathy. Altered expression of connexin43 (Cx43) has been found in kidneys of diabetic animals. The aim of the current study was to investigate the role of Cx43 in the activation of NF-κB induced by high glucose in glomerular mesangial cells (GMCs) and to determine whether c-Src is involved in this process. Results We found that downregulation of Cx43 expression induced by high glucose activated NF-κB in GMCs. Orverexpression of Cx43 attenuated NF-κB p65 nuclear translocation induced by high glucose. High glucose inhibited the interaction between Cx43 and c-Src, and enhanced the interaction between c-Src and IκB-α. PP2, a c-Src inhibitor, also inhibited the tyrosine phosphorylation of IκB-α and NF-κB p65 nuclear translocation induced by high glucose. Furthermore, overexpression of Cx43 or inhibition of c-Src attenuated the upregulation of intercellular adhesion molecule-1 (ICAM-1), transforming growth factor-beta 1 (TGF-β1) and fibronectin (FN) expression induced by high glucose. Conclusions In conclusion, downregulation of Cx43 in GMCs induced by high glucose activates c-Src, which in turn promotes interaction between c-Src and IκB-α and contributes to NF-κB activation in GMCs, leading to renal inflammation.
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Affiliation(s)
- Xi Xie
- Laboratory of Pharmacology & Toxicology, School of Pharmaceutical Sciences, Sun Yat-sen University, Guangzhou, 510006, China.
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Chen X, Feng L, Jin H. Constant or fluctuating hyperglycemias increases cytomembrane stiffness of human umbilical vein endothelial cells in culture: roles of cytoskeletal rearrangement and nitric oxide synthesis. BMC Cell Biol 2013; 14:22. [PMID: 23601245 PMCID: PMC3651398 DOI: 10.1186/1471-2121-14-22] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2012] [Accepted: 04/16/2013] [Indexed: 02/01/2023] Open
Abstract
Background Previous studies have implicated continuous or intermittent hyperglycemia in altered endothelium-derived nitric oxide (NO) synthesis. NO can regulate both the F-actin cytoskeleton and endothelial cell membrane stiffness. Atomic force microscopy (AFM) is a powerful tool that can be used to study plasma membrane deformability at the single cell level. As membrane stiffness is partially dependent on filamentous F-actin, the interdependence of these parameters can be studied through the combined approaches of AFM and laser scanning confocal microscopy (LSCM). In the present study, we evaluated the effects of constant or fluctuating hyperglycemia on endothelial-derived NO synthesis, the cytoskeletal contribution and endothelial cell membrane stiffness. Results Compared to control cells cultured in low glucose (5 mM), constant (25 mM) or fluctuating (25/5 mM) high glucose significantly decreased NO release along with stiffening of endothelial cell membranes and F-actin rearrangement. The non-selective nitric oxide synthase (NOS) inhibitor, NG-nitro-L-arginine methyl ester (L-NAME) exerted similar effects on endothelial cells. Increasing concentrations of L-NAME (from 0.1 to 1 mM) exacerbated these effects in a concentration-dependent manner. Conclusions Result from the present study suggest that stiffening endothelial cell membranes are associated with decreased NO synthesis, which was established through the F-actin cytoskeletal redistribution. The precise mechanisms of hyperglycemia-induced endothelial dysfunction require further investigation.
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Affiliation(s)
- Xianxian Chen
- The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong, China
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Xi G, Shen X, Maile LA, Wai C, Gollahon K, Clemmons DR. Hyperglycemia enhances IGF-I-stimulated Src activation via increasing Nox4-derived reactive oxygen species in a PKCζ-dependent manner in vascular smooth muscle cells. Diabetes 2012; 61:104-13. [PMID: 22148072 PMCID: PMC3237650 DOI: 10.2337/db11-0990] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
IGF-I-stimulated sarcoma viral oncogene (Src) activation during hyperglycemia is required for propagating downstream signaling. The aim of the current study was to determine the mechanism by which hyperglycemia enhances IGF-I-stimulated Src activation and the role of NADPH oxidase 4 (Nox4) and protein kinase C ζ (PKCζ) in mediating this response in vascular smooth muscle cells (VSMCs). Nox4 expression was analyzed in VSMCs exposed to hyperglycemia. The role of Nox4-derived reactive oxygen species (ROS) in IGF-I-stimulated Src activation was investigated via knockdown of Nox4. Different isoforms of PKC were screened to investigate their role in hyperglycemia-induced Nox4. The oxidation of Src was shown to be a prerequisite for its activation in response to IGF-I during hyperglycemia. Hyperglycemia induced Nox4, but not Nox1, and p22 phagocyte oxidase (p22phox) expression and IGF-I stimulated Nox4/p22phox complex formation, leading to increased ROS generation. Knockdown of Nox4 prevented ROS generation and impaired the oxidation and activation of Src in response to IGF-I, whereas knockdown of Nox1 had no effect. PKCζ was shown to mediate the hyperglycemia-induced increase in Nox4 expression. The key observations in cultured VSMCs were confirmed in the diabetic mice. Nox4-derived ROS is responsible for the enhancing effect of hyperglycemia on IGF-I-stimulated Src activation, which in turn amplifies IGF-I-linked downstream signaling and biological actions.
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Chalovich JM, Schroeter MM. Synaptopodin family of natively unfolded, actin binding proteins: physical properties and potential biological functions. Biophys Rev 2010; 2:181-189. [PMID: 28510039 PMCID: PMC5418383 DOI: 10.1007/s12551-010-0040-5] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2010] [Accepted: 11/01/2010] [Indexed: 12/15/2022] Open
Abstract
The synaptopodin family of proteins consists of at least 3 members: synaptopodin, the synaptopodin 2 proteins, and the synaptopodin 2-like proteins. Each family member has at least 3 isoforms that are produced by alternative splicing. Synaptopodin family members are basic proteins that are rich in proline and have little regular 2° or 3° structure at physiological temperature, pH and ionic strength. Like other natively unfolded proteins, synaptopodin family members have multiple binding partners including actin and other actin-binding proteins. Several members of the synaptopodin family have been shown to stimulate actin polymerization and to bundle actin filaments either on their own or in collaboration with other proteins. Synaptopodin 2 has been shown to accelerate nucleation of actin filament formation and to induce actin bundling. The actin polymerization activity is inhibited by Ca2+-calmodulin. Synaptopodin 2 proteins are localized in Z-bands of striated and heart muscle and dense bodies of smooth muscle cells. Depending on the developmental status and stress, at least one member of the synaptopodin family can occupy nuclei of some cells. Members of the synaptopodin 2 subfamily have been implicated in cancers.
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Affiliation(s)
- Joseph M Chalovich
- Department of Biochemistry and Molecular Biology, Brody School of Medicine at East Carolina University, 5E-122 Brody Medical Sciences Building, 600 Moye Blvd, Greenville, NC, 27834, USA.
| | - Mechthild M Schroeter
- Department of Physiology, University of Cologne, Robert-Koch-Str. 39, 50931, Cologne, Germany
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10
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Gur S, Kadowitz PJ, Hellstrom WJ. A Protein Tyrosine Kinase Inhibitor, Imatinib Mesylate (Gleevec), Improves Erectile and Vascular Function Secondary to a Reduction of Hyperglycemia in Diabetic Rats. J Sex Med 2010; 7:3341-50. [DOI: 10.1111/j.1743-6109.2010.01922.x] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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11
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Searls YM, Loganathan R, Smirnova IV, Stehno-Bittel L. Intracellular Ca2+ regulating proteins in vascular smooth muscle cells are altered with type 1 diabetes due to the direct effects of hyperglycemia. Cardiovasc Diabetol 2010; 9:8. [PMID: 20122173 PMCID: PMC2829469 DOI: 10.1186/1475-2840-9-8] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/26/2009] [Accepted: 02/01/2010] [Indexed: 02/01/2023] Open
Abstract
Background Diminished calcium (Ca2+) transients in response to physiological agonists have been reported in vascular smooth muscle cells (VSMCs) from diabetic animals. However, the mechanism responsible was unclear. Methodology/Principal Findings VSMCs from autoimmune type 1 Diabetes Resistant Bio-Breeding (DR-BB) rats and streptozotocin-induced rats were examined for levels and distribution of inositol trisphosphate receptors (IP3R) and the SR Ca2+ pumps (SERCA 2 and 3). Generally, a decrease in IP3R levels and dramatic increase in ryanodine receptor (RyR) levels were noted in the aortic samples from diabetic animals. Redistribution of the specific IP3R subtypes was dependent on the rat model. SERCA 2 was redistributed to a peri-nuclear pattern that was more prominent in the DR-BB diabetic rat aorta than the STZ diabetic rat. The free intracellular Ca2+ in freshly dispersed VSMCs from control and diabetic animals was monitored using ratiometric Ca2+ sensitive fluorophores viewed by confocal microscopy. In control VSMCs, basal fluorescence levels were significantly higher in the nucleus relative to the cytoplasm, while in diabetic VSMCs they were essentially the same. Vasopressin induced a predictable increase in free intracellular Ca2+ in the VSMCs from control rats with a prolonged and significantly blunted response in the diabetic VSMCs. A slow rise in free intracellular Ca2+ in response to thapsigargin, a specific blocker of SERCA was seen in the control VSMCs but was significantly delayed and prolonged in cells from diabetic rats. To determine whether the changes were due to the direct effects of hyperglycemica, experiments were repeated using cultured rat aortic smooth muscle cells (A7r5) grown in hyperglycemic and control conditions. In general, they demonstrated the same changes in protein levels and distribution as well as the blunted Ca2+ responses to vasopressin and thapsigargin as noted in the cells from diabetic animals. Conclusions/Significance This work demonstrates that the previously-reported reduced Ca2+ signaling in VSMCs from diabetic animals is related to decreases and/or redistribution in the IP3R Ca2+ channels and SERCA proteins. These changes can be duplicated in culture with high glucose levels.
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Affiliation(s)
- Yvonne M Searls
- Department of Physical Therapy and Rehabilitation Science, University of Kansas Medical Center, Kansas City, KS 66160, USA
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12
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Zhu P, Chen G, You T, Yao J, Jiang Q, Lin X, Shen X, Qiao Y, Lin L. High FFA-induced proliferation and apoptosis in human umbilical vein endothelial cell partly through Wnt/β-catenin signal pathway. Mol Cell Biochem 2009; 338:123-31. [DOI: 10.1007/s11010-009-0345-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2009] [Accepted: 11/19/2009] [Indexed: 10/20/2022]
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13
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Graier WF, Malli R, Kostner GM. Mitochondrial protein phosphorylation: instigator or target of lipotoxicity? Trends Endocrinol Metab 2009; 20:186-93. [PMID: 19356948 PMCID: PMC4861235 DOI: 10.1016/j.tem.2009.01.004] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/01/2008] [Revised: 01/21/2009] [Accepted: 01/21/2009] [Indexed: 01/28/2023]
Abstract
Lipotoxicity occurs as a consequence of chronic exposure of non-adipose tissue and cells to elevated concentrations of fatty acids, triglycerides and/or cholesterol. The contribution of mitochondria to lipotoxic cell dysfunction, damage and death is associated with elevated production of reactive oxygen species and initiation of apoptosis. Although there is a broad consensus on the involvement of these phenomena with lipotoxicity, the molecular mechanisms that initiate, mediate and trigger mitochondrial dysfunction in response to substrate overload remain unclear. Here, we focus on protein phosphorylation as an important phenomenon in lipotoxicity that harms mitochondria-related signal transduction and integration in cellular metabolism. Moreover, the degradation of mitochondria by mitophagy is discussed as an important landmark that leads to cellular apoptosis in lipotoxicity.
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Affiliation(s)
- Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University Graz, Graz, Austria.
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14
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Waldeck-Weiermair M, Zoratti C, Osibow K, Balenga N, Goessnitzer E, Waldhoer M, Malli R, Graier WF. Integrin clustering enables anandamide-induced Ca2+ signaling in endothelial cells via GPR55 by protection against CB1-receptor-triggered repression. J Cell Sci 2008; 121:1704-1717. [PMID: 18445684 PMCID: PMC4067516 DOI: 10.1242/jcs.020958] [Citation(s) in RCA: 145] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023] Open
Abstract
Although the endocannabinoid anandamide is frequently described to act predominantly in the cardiovascular system, the molecular mechanisms of its signaling remained unclear. In human endothelial cells, two receptors for anandamide were found, which were characterized as cannabinoid 1 receptor (CB1R; CNR1) and G-protein-coupled receptor 55 (GPR55). Both receptors trigger distinct signaling pathways. It crucially depends on the activation status of integrins which signaling cascade becomes promoted upon anandamide stimulation. Under conditions of inactive integrins, anandamide initiates CB1R-derived signaling, including Gi-protein-mediated activation of spleen tyrosine kinase (Syk), resulting in NFkappaB translocation. Furthermore, Syk inhibits phosphoinositide 3-kinase (PI3K) that represents a key protein in the transduction of GPR55-originated signaling. However, once integrins are clustered, CB1R splits from integrins and, thus, Syk cannot further inhibit GPR55-triggered signaling resulting in intracellular Ca2+ mobilization from the endoplasmic reticulum (ER) via a PI3K-Bmx-phospholipase C (PLC) pathway and activation of nuclear factor of activated T-cells. Altogether, these data demonstrate that the physiological effects of anandamide on endothelial cells depend on the status of integrin clustering.
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Affiliation(s)
| | - Cristina Zoratti
- Institute of Molecular Biology and Biochemistry, Medical University Graz, Graz, A8010, Austria
| | - Karin Osibow
- Institute of Molecular Biology and Biochemistry, Medical University Graz, Graz, A8010, Austria
| | - Nariman Balenga
- Institute of Experimental and Clinical Pharmacology, Medical University Graz, Graz, A8010, Austria
| | - Edith Goessnitzer
- Institute of Pharmaceutical Chemistry, University Graz, Graz Austria
| | - Maria Waldhoer
- Institute of Experimental and Clinical Pharmacology, Medical University Graz, Graz, A8010, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Medical University Graz, Graz, A8010, Austria
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Medical University Graz, Graz, A8010, Austria
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Graier WF, Trenker M, Malli R. Mitochondrial Ca2+, the secret behind the function of uncoupling proteins 2 and 3? Cell Calcium 2008; 44:36-50. [PMID: 18282596 DOI: 10.1016/j.ceca.2008.01.001] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2007] [Revised: 01/07/2008] [Accepted: 01/07/2008] [Indexed: 12/20/2022]
Abstract
The underlying molecular action of the novel uncoupling proteins 2 and 3 (UCP2 and UCP3) is still under debate. The proteins have been implicated in many cell functions, including the regulation of insulin secretion and regulation of reactive oxygen species (ROS) generation. These effects have mainly been explained by suggesting that the proteins establish a proton leak through the inner mitochondrial membrane (IMM). However, accumulating data question this mechanism and suggest that UCP2 and UCP3 may play other roles, including carrying free fatty acids from the matrix towards the intermembrane space, or contributing to the mitochondrial Ca(2+) uniport. Accordingly, in this review we reflect on these actions of UCP2/UCP3 and discuss alternative explanations for the molecular mechanisms by which UCP2/UCP3 might contribute to aspects of cell function. Based on the potential role of UCP2/UCP3 in regulating mitochondrial Ca(2+) uptake, we propose a scheme whereby these proteins integrate Ca(2+)-dependent signal transduction and energy metabolism in order to meet the energy demand of the cell for its continuous response, adaptation, and stimulation to environmental input.
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Affiliation(s)
- Wolfgang F Graier
- Institute of Molecular Biology and Biochemistry, Molecular and Cellular Physiology Research Unit, Center of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, Graz, Austria.
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16
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Trenker M, Malli R, Fertschai I, Levak-Frank S, Graier WF. Uncoupling proteins 2 and 3 are fundamental for mitochondrial Ca2+ uniport. Nat Cell Biol 2007; 9:445-452. [PMID: 17351641 PMCID: PMC4060164 DOI: 10.1038/ncb1556] [Citation(s) in RCA: 277] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2006] [Accepted: 01/17/2007] [Indexed: 01/05/2023]
Abstract
Mitochondrial Ca(2+) uptake is crucial for the regulation of the rate of oxidative phosphorylation, the modulation of spatio-temporal cytosolic Ca(2+) signals and apoptosis. Although the phenomenon of mitochondrial Ca(2+) sequestration, its characteristics and physiological consequences have been convincingly reported, the actual protein(s) involved in this process are unknown. Here, we show that the uncoupling proteins 2 and 3 (UCP2 and UCP3) are essential for mitochondrial Ca(2+) uptake. Using overexpression, knockdown (small interfering RNA) and mutagenesis experiments, we demonstrate that UCP2 and UCP3 are elementary for mitochondrial Ca(2+) sequestration in response to cell stimulation under physiological conditions - observations supported by isolated liver mitochondria of Ucp2(-/-) mice lacking ruthenium red-sensitive Ca(2+) uptake. Our results reveal a novel molecular function for UCP2 and UCP3, and may provide the molecular mechanism for their reported effects. Moreover, the identification of proteins fundemental for mitochondrial Ca(2+) uptake expands our knowledge of the physiological role for mitochondrial Ca(2+) sequestration.
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Affiliation(s)
- Michael Trenker
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Roland Malli
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Ismene Fertschai
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Sanja Levak-Frank
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Wolfgang F. Graier
- Institute of Molecular Biology and Biochemistry, Centre of Molecular Medicine, Medical University of Graz, Harrachgasse 21/III, 8010 Graz, Austria
- Correspondence should be addressed to W.F.G. ()
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Matsumoto T, Kobayashi T, Kamata K. Mechanisms underlying lysophosphatidylcholine-induced potentiation of vascular contractions in the Otsuka Long-Evans Tokushima Fatty (OLETF) rat aorta. Br J Pharmacol 2006; 149:931-41. [PMID: 17031383 PMCID: PMC2014696 DOI: 10.1038/sj.bjp.0706937] [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: 12/17/2022] Open
Abstract
BACKGROUND AND PURPOSE The effect of lysophosphatidylcholine (LPC) on aortic contractions in Otsuka Long-Evans Tokushima Fatty (OLETF) rats, a type 2 diabetic model, was studied. EXPERIMENTAL APPROACH Using OLETF rats and control (Long Evans Tokushima Otsuka (LETO)) rats, the effects of LPC on the contractions induced by high-K(+) (10-40 mM), UK14,304 (10 approximately 100 nM; a selective alpha(2)-adrenoceptor agonist) and sodium orthovanadate (SOV; 10 microM approximately 3 mM) in endothelium-denuded aortae were compared. Aortic ERK activity and the mRNA expression for GPR4 (a putative LPC receptor) were also measured. KEY RESULTS OLETF rats exhibited (vs. age-matched LETO rats): (1) greater potentiation of high-K(+)-induced contraction by 10 microM LPC - a potentiation attenuated by 10 microM genistein, protein tyrosine kinase (PTK) inhibitor, (2) greater potentiation of UK14,304 (10 approximately 100 nM)-induced contractions by LPC (1 microM approximately 10 microM) - a potentiation attenuated by 10 microM genistein, 50 microM tyrphostin A23 (PTK inhibitor) or 10 microM PD98059 (MEK 1/2 inhibitor), (3) greater basal and LPC (1 microM)-induced ERK activities, (4) greater basal and 100 nM UK14,304-stimulated ERK2 activities in both the absence and presence of 10 microM LPC, (5) greater SOV (10 microM approximately 3 mM)-induced contractions, (6) greater potentiation of SOV-induced contractions by 10 microM LPC - a potentiation suppressed by 10 microM PD98059 or 10 microM genistein, (7) upregulation of GPR4 mRNA. CONCLUSIONS AND IMPLICATIONS These results suggest that the LPC-induced potentiation of contractions in the OLETF rat aorta may be attributable to increased PTKs or ERK activity and/or to receptor upregulation.
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MESH Headings
- Animals
- Aorta, Thoracic/drug effects
- Brimonidine Tartrate
- Diabetes Mellitus, Type 2/physiopathology
- Disease Models, Animal
- Dose-Response Relationship, Drug
- Lysophosphatidylcholines/pharmacology
- MAP Kinase Signaling System/drug effects
- Male
- Muscle, Smooth, Vascular/chemistry
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/physiopathology
- Potassium/pharmacology
- Protein Kinase Inhibitors/pharmacology
- Protein Tyrosine Phosphatases/antagonists & inhibitors
- Quinoxalines/pharmacology
- RNA, Messenger/analysis
- Rats
- Rats, Inbred OLETF
- Rats, Long-Evans
- Receptors, G-Protein-Coupled/analysis
- Up-Regulation
- Vanadates
- Vasoconstriction/drug effects
- Vasoconstrictor Agents/pharmacology
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Affiliation(s)
- T Matsumoto
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University Shinagawa-ku, Tokyo, Japan
| | - T Kobayashi
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University Shinagawa-ku, Tokyo, Japan
| | - K Kamata
- Department of Physiology and Morphology, Institute of Medicinal Chemistry, Hoshi University Shinagawa-ku, Tokyo, Japan
- Author for correspondence:
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Osibow K, Frank S, Malli R, Zechner R, Graier W. Mitochondria maintain maturation and secretion of lipoprotein lipase in the endoplasmic reticulum. Biochem J 2006; 396:173-82. [PMID: 16466345 PMCID: PMC1449989 DOI: 10.1042/bj20060099] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Considering the physiological Ca2+ dynamics within the ER (endoplasmic reticulum), it remains unclear how efficient protein folding is maintained in living cells. Thus, utilizing the strictly folding-dependent activity and secretion of LPL (lipoprotein lipase), we evaluated the impact of ER Ca2+ content and mitochondrial contribution to Ca2+-dependent protein folding. Exhaustive ER Ca2+ depletion by inhibition of sarcoplasmic/endoplasmic reticulum Ca2+-ATPases caused strong, but reversible, reduction of cell-associated and released activity of constitutive and adenovirus-encoded human LPL in CHO-K1 (Chinese-hamster ovary K1) and endothelial cells respectively, which was not due to decline of mRNA or intracellular protein levels. In contrast, stimulation with the IP3 (inositol 1,4,5-trisphosphate)-generating agonist histamine only moderately and transiently affected LPL maturation in endothelial cells that paralleled a basically preserved ER Ca2+ content. However, in the absence of extracellular Ca2+ or upon prevention of transmitochondrial Ca2+ flux, LPL maturation discontinued upon histamine stimulation. Collectively, these data indicate that Ca2+-dependent protein folding in the ER is predominantly controlled by intraluminal Ca2+ and is largely maintained during physiological cell stimulation owing to efficient ER Ca2+ refilling. Since Ca2+ entry and mitochondrial Ca2+ homoeostasis are crucial for continuous Ca2+-dependent protein maturation in the ER, their pathological alterations may result in dysfunctional protein folding.
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Affiliation(s)
- Karin Osibow
- *Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Sasa Frank
- *Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Roland Malli
- *Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University Graz, Harrachgasse 21/III, 8010 Graz, Austria
| | - Rudolf Zechner
- †Institute of Molecular Biosciences, Karl-Franzens University Graz, Heinrichstrasse 31a, 8010 Graz, Austria
| | - Wolfgang F. Graier
- *Institute of Molecular Biology and Biochemistry, Center of Molecular Medicine, Medical University Graz, Harrachgasse 21/III, 8010 Graz, Austria
- To whom correspondence should be addressed (email )
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19
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Jazwa A, Loboda A, Golda S, Cisowski J, Szelag M, Zagorska A, Sroczynska P, Drukala J, Jozkowicz A, Dulak J. Effect of heme and heme oxygenase-1 on vascular endothelial growth factor synthesis and angiogenic potency of human keratinocytes. Free Radic Biol Med 2006; 40:1250-63. [PMID: 16545694 PMCID: PMC1414644 DOI: 10.1016/j.freeradbiomed.2005.11.016] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/25/2005] [Revised: 11/03/2005] [Accepted: 11/16/2005] [Indexed: 02/07/2023]
Abstract
BACKGROUND Skin injury leads to the release of heme, a potent prooxidant which is degraded by heme oxygenase-1 (HO-1) to carbon monoxide, iron, and biliverdin, subsequently reduced to bilirubin. Recently the involvement of HO-1 in angiogenesis has been shown; however, the role of heme and HO-1 in wound healing angiogenesis has not been yet investigated. RESULTS Treatment of HaCaT keratinocytes with hemin (heme chloride) induced HO-1 expression and activity. The effect of heme on vascular endothelial growth factor (VEGF) synthesis is variable: induction is significant after a short, 6 h treatment with heme, while longer stimulation may attenuate its production. The involvement of HO-1 in VEGF synthesis was confirmed by inhibition of VEGF expression by SnPPIX, a blocker of HO activity and by attenuation of HO-1 mRNA expression with specific siRNA. Importantly, induction of HO-1 by hemin was able to overcome the inhibitory effect of high glucose on VEGF synthesis. Moreover, HO-1 expression was also induced in keratinocytes cultured in hypoxia, with concomitant augmentation of VEGF production, which was further potentiated by hemin stimulation. Accordingly, conditioned media from keratinocytes overexpressing HO-1 enhanced endothelial cell proliferation and augmented formation of capillaries in angiogenic assay in vitro. CONCLUSIONS HO-1 is involved in hemin-induced VEGF expression in HaCaT and may play a role in hypoxic regulation of this protein. HO-1 overexpression may be beneficial in restoring the proper synthesis of VEGF disturbed in diabetic conditions.
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Affiliation(s)
- Agnieszka Jazwa
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Agnieszka Loboda
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Slawomir Golda
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Jaroslaw Cisowski
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Magdalena Szelag
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Anna Zagorska
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Patrycja Sroczynska
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Justyna Drukala
- Department of Cell Biology, Faculty of Biotechnology, Jagiellonian University, Krakow, Poland
| | - Alicja Jozkowicz
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
| | - Jozef Dulak
- Department of Medical Biotechnology, Faculty of Biotechnology, Jagiellonian University, Gronostajowa 7, 30-387 Krakow, Poland
- Corresponding author. Fax: +48 12 664 69 18. E-mail address: (J. Dulak)
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20
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Jalal DI, Kone BC. Src activation of NF-kappaB augments IL-1beta-induced nitric oxide production in mesangial cells. J Am Soc Nephrol 2005; 17:99-106. [PMID: 16338964 DOI: 10.1681/asn.2005070693] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
NF-kappaB is a critical transcription factor that is involved in glomerulonephritis and inflammatory host responses and a critical transactivator of the inducible nitric oxide (NO) synthase gene in mesangial cells. The Src protein tyrosine kinases (SFK) are involved in several signaling pathways and have been proposed to mediate cytokine activation of NF-kappaB in a few cell types. However, the specific involvement of SFK in IL-1beta induction of NO production has not been clearly established. Accordingly, pharmacologic and molecular tools were used to clarify this issue in cultured murine mesangial cells. The SFK antagonist 4-amino-5-(4-chlorophenyl)-7-(t-butyl) pyrazolo(3,4-d)pyrimidine (PP2) dramatically inhibited IL-1beta-mediated induction of endogenous NO production as measured by the Griess reaction, as well as the induction of NF-kappaB p50/p65 DNA-binding activity in gel shift assays and the activity of an NF-kappaB-responsive promoter-reporter construct transiently transfected into the cells. Immunoprecipitation and immunoblotting with anti-IkappaBalpha and anti-phosphotyrosine antibodies revealed that PP2 also inhibited IL-1beta-stimulated tyrosine phosphorylation of IkappaBalpha, a requisite step in NF-kappaB activation in this signaling cascade. In agreement with the pharmacologic inhibition studies, siRNA directed against c-Src specifically limited c-Src protein expression and inhibited IL-1beta-mediated induction of NF-kappaB DNA-binding activity, whereas control siRNA had no effect. Conversely, overexpression of constitutively active c-Src augmented basal and IL-1beta-mediated induction of NF-kappaB DNA-binding activity and NO production. Thus, SFK play a key role in IL-1beta-induced NO production in mesangial cells and do so via tyrosine phosphorylation of IkappaBalpha and consequent NF-kappaB activation.
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Affiliation(s)
- Diane I Jalal
- Department of Internal Medicine, The University of Texas Medical School at Houston, 6431 Fannin, MSB 1.150, Houston, TX 77030, USA
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Wiernsperger NF. Is non-insulin dependent glucose uptake a therapeutic alternative? Part 2: Do such mechanisms fulfil the required combination of power and tolerability? DIABETES & METABOLISM 2005; 31:521-5. [PMID: 16357799 DOI: 10.1016/s1262-3636(07)70226-4] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
The worldwide burden of diabetes, the unavoidable worsening which is observed in long-term clinical trials despite treatment and the close link between glycaemia and microangiopathy appeal for much stronger treatment strategies. This, in turn, either requires polypharmacy (with new risks) or new, more powerful drugs to be invented. The first part of this review dealt with a thorough analysis of pros and cons for some selected pathways which could potentially increase glucose uptake without necessitating insulin. The choice of such targets for developing completely new drugs, however, requires a favourable background from existing tentatives with either drugs or cell biology approaches. Moreover, because vascular complications are what must ultimately be avoided when treating diabetic patients, we must be sure that increasing glucose uptake in a fashion which is no more controlled by normal physiology is compatible with the physiology of vascular cells (long-term tolerance). The aspect of drug side-effects must therefore be considered systematically. For reasons which are individually developed, it appears that each of the potential pathways analyzed either lacks sufficient power and/or is likely to induce side effects which are not acceptable for long-term application. The fact that GLUT-1 transporters are ubiquitously distributed even extends this cardinal question to the general principle of increasing glucose uptake. In conclusion a precise evaluation suggests that, although non-insulin dependent glucose uptake represents (3/4) of whole body glucose transport, it is difficult to consider such mechanisms able to generate a new treatment fulfilling the unavoidable request of combined efficacy and tolerability.
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Affiliation(s)
- N F Wiernsperger
- INSERM UMR 585, Bâtiment Louis Pasteur, INSA Lyon, boulevard J. Chapelle, 69621 Villeurbanne Cedex, France.
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22
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Tamareille S, Mignen O, Capiod T, Rücker-Martin C, Feuvray D. High glucose-induced apoptosis through store-operated calcium entry and calcineurin in human umbilical vein endothelial cells. Cell Calcium 2005; 39:47-55. [PMID: 16243395 DOI: 10.1016/j.ceca.2005.09.008] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2005] [Revised: 09/05/2005] [Accepted: 09/09/2005] [Indexed: 12/11/2022]
Abstract
Diabetes mellitus causes multiple cardiovascular complications. Previous studies have shown that prolonged exposure (96 h) of human umbilical vein endothelial cells (HUVECs) to hyperglycemia causes a significant increase in apoptosis. We report here that this increase in apoptosis is associated with an increase in Ca(2+) current (whole cell patch-clamp recorded) resulting from Ca(2+) entry mediated by store-operated channels (SOCs). The number of apoptotic cells after prolonged high glucose (HG, 30 mmol/L) exposure was significantly reduced in the presence of the SOC inhibitor 2-APB or of La(3+). A marked increase (approximately 80%) in Ca(2+)-dependent calcineurin (CN-A) phosphatase activity also occurred after prolonged HG exposure. Prolonged HG exposure-induced increase in CN-A activity was prevented by 2-APB, and selective CN-A phosphatase inhibition by FK506 or calmodulin inhibition by calmidazolium decreased HG-induced apoptosis. Blocking hydrogen peroxide production using catalase or inhibiting the tyrosine kinase pp60(src) during prolonged exposure to HG, resulted in a marked decrease in apoptosis and was further associated with a significant reduction in CN-A phosphatase activity. The results demonstrate a significant role for Ca(2+) entry in HG-induced apoptosis in HUVECs, and suggest that this role is mediated via H(2)O(2) generation and the action of the Ca(2+)-activated protein phosphatase calcineurin.
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Affiliation(s)
- Sophie Tamareille
- Centre National de la Recherche Scientifique, Unité Mixte de Recherche 8078, Université Paris XI, Hôpital Marie Lannelongue, 92350 Le Plessis Robinson, France
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Kipmen-Korgun D, Osibow K, Zoratti C, Schraml E, Greilberger J, Kostner GM, Jürgens G, Graier WF. T-cadherin mediates low-density lipoprotein-initiated cell proliferation via the Ca(2+)-tyrosine kinase-Erk1/2 pathway. J Cardiovasc Pharmacol 2005; 45:418-30. [PMID: 15821437 DOI: 10.1097/01.fjc.0000157458.91433.86] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
The GPI-anchored protein T-cadherin was found to be an atypical LDL binding site that is expressed in various types of cells, including endothelial cells, smooth muscle cells, and neurons. Notably, the expression of T-cadherin was reduced in numerous types of cancers, although it was up-regulated in tumor-penetrating blood vessels, atherosclerotic lesions, and during neointima formation. Despite these intriguing findings, our knowledge of the physiological role and the signal transduction pathways associated with this protein is limited. Therefore, T-cadherin was overexpressed in the human umbilical vein-derived endothelial cell line EA.hy926, the human embryonic kidney cell line HEK293, and LDL-initiated signal transduction, and its consequences were elucidated. Our data revealed that T-cadherin serves as a receptor specifically for LDL. Following LDL binding to T-cadherin, mitogenic signal transduction was initiated that involved activation of PLC and IP3 formation, which subsequently yielded intracellular Ca2+ mobilization. Downstream to these early phenomena, activation of tyrosine kinase(s) Erk 1/2 kinase, and the translocation of NF kappa B toward the nucleus were found. Finally, overexpression of T-cadherin in HEK293 cells resulted in accelerated cell proliferation in an LDL-dependent manner, although cell viability was not influenced. Because LDL uptake was not facilitated by T-cadherin, our data suggest that T-cadherin serves as a signaling receptor for LDL that facilitates an LDL-dependent mitogenic signal in the vasculature.
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Affiliation(s)
- Dijle Kipmen-Korgun
- Institute of Molecular Biology & Biochemistry, Center of Molecular Medicine, Medical University Graz, Graz, Austria
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Paltauf-Doburzynska J, Malli R, Graier WF. Hyperglycemic Conditions Affect Shape and Ca2+ Homeostasis of Mitochondria in Endothelial Cells. J Cardiovasc Pharmacol 2004; 44:423-36. [PMID: 15454850 DOI: 10.1097/01.fjc.0000139449.64337.1b] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
In this study the contribution of alternating architecture and Ca2+ handling of mitochondria to cytosolic Ca2+ homeostasis was elucidated under normoglycemic and hyperglycemic (HGC) conditions in the human endothelial cell line EA.hy926. Exposure of endothelial cells to hyperglycemic medium elevated basal cytosolic free Ca2+ concentration ([Ca2+]cyto), the histamine-initiated cytosolic Ca2+ signaling, and the mitochondrial Ca2+ content after cell stimulation. The latter was possibly due to the prolonged mitochondrial Ca2+ elevation in response to agonists found in HGC-pretreated cells. Moreover, under HGC mitochondrial free radical production was increased and mitochondrial shape changed from a mainly tubular, highly interconnected network toward multiple, isolated singular structures. Such changes could not be correlated with HGC-induced alterations of cytosolic Ca2+ signaling that became normalized with antimycin A, an inhibitor of the respiratory chain. These data suggest that although mitochondrial structure changes considerably during HGC, alterations in cytosolic Ca2+ signaling are more likely due to the enhanced energy status/metabolism of the mitochondria. On the other hand, in normoglycemic cells of unforced fragmentation of mitochondria yielded elevated basal [Ca2+]cyto, while the global Ca2+ signaling in response to histamine remained unchanged. Thus, mitochondrial architecture (ie, tubular versus fragmented structure) per se does not have a detectable impact on agonist-initiated global cytosolic Ca2+ signaling, while this organelle represents an early target in hyperglycemia leading to alterations in cytosolic Ca2+ signaling.
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Affiliation(s)
- Jolanta Paltauf-Doburzynska
- Department of Medical Biochemistry and Medical Molecular Biology, Medical University of Graz, 8010 Graz, Austria
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