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Fomo KN, Perumal N, Manicam C, Pfeiffer N, Grus FH. Neuroretinal Cell Culture Model as a Tool for the Development of New Therapeutic Approaches for Oxidative Stress-Induced Ocular Diseases, with a Focus on Glaucoma. Cells 2024; 13:775. [PMID: 38727311 PMCID: PMC11083839 DOI: 10.3390/cells13090775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2024] [Revised: 04/15/2024] [Accepted: 04/29/2024] [Indexed: 05/13/2024] Open
Abstract
Glaucoma is a heterogeneous group of optic neuropathies characterized by a progressive degeneration of the retinal ganglion cells (RGCs), leading to irreversible vision loss. Nowadays, the traditional therapeutic approach to glaucoma consists of lowering the intraocular pressure (IOP), which does not address the neurodegenerative features of the disease. Besides animal models of glaucoma, there is a considerable need for in vitro experimental models to propose new therapeutic strategies for this ocular disease. In this study, we elucidated the pathological mechanisms leading to neuroretinal R28 cell death after exposure to glutamate and hydrogen peroxide (H2O2) in order to develop new therapeutic approaches for oxidative stress-induced retinal diseases, including glaucoma. We were able to show that glutamate and H2O2 can induce a decrease in R28 cell viability in a concentration-dependent manner. A cell viability of about 42% was found after exposure to 3 mM of glutamate and about 56% after exposure to 100 µM of H2O2 (n = 4). Label-free quantitative mass spectrometry analysis revealed differential alterations of 193 and 311 proteins in R28 cells exposed to 3 mM of glutamate and 100 µM of H2O2, respectively (FDR < 1%; p < 0.05). Bioinformatics analysis indicated that the protein changes were associated with the dysregulation of signaling pathways, which was similar to those observed in glaucoma. Thus, the proteomic alteration induced by glutamate was associated with the inhibition of the PI3K/AKT signaling pathway. On the other hand, H2O2-induced toxicity in R28 cells was linked to the activation of apoptosis signaling and the inhibition of the mTOR and ERK/MAPK signaling pathways. Furthermore, the data show a similarity in the inhibition of the EIF2 and AMPK signaling pathways and the activation of the sumoylation and WNT/β-catenin signaling pathways in both groups. Our findings suggest that the exposure of R28 cells to glutamate and H2O2 could induce glaucoma-like neurodegenerative features and potentially provide a suitable tool for the development of new therapeutic strategies for retinal diseases.
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Affiliation(s)
| | | | | | | | - Franz H. Grus
- Experimental and Translational Ophthalmology, Department of Ophthalmology, University Medical Centre of the Johannes Gutenberg University Mainz, 55131 Mainz, Germany; (K.N.F.); (N.P.); (C.M.); (N.P.)
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2
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Goris M, Jacobsen RG, Lewis AE. Presence of active AKT in the nucleus upon adipocyte differentiation of 3T3-L1 cells. MICROPUBLICATION BIOLOGY 2024; 2024:10.17912/micropub.biology.001140. [PMID: 38495585 PMCID: PMC10940900 DOI: 10.17912/micropub.biology.001140] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Figures] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 02/14/2024] [Accepted: 02/25/2024] [Indexed: 03/19/2024]
Abstract
AKT is an essential player in the phosphoinositide 3-kinase (PI3K) signalling pathway. Although the mechanisms of its action are well understood at the plasma membrane, AKT can also be found in the nucleus. In adipocytes, this pathway is activated during the process of adipogenesis and solicits both plasma membrane and nuclear AKT activity. However, the endogenous presence of active AKT in the nucleus during adipogenesis has not been shown. Here, we show that the levels of active AKT phosphorylated at Ser-473 increase rapidly after the induction of differentiation in 3T3-L1 cells, both in the cytoplasm and in the nucleus, and tend to remain elevated over the course of differentiation. In conclusion, these results support the notion that nuclear AKT plays an important role in this process.
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Affiliation(s)
- Marianne Goris
- Department of Biological Sciences, University of Bergen, Bergen, Vestland, Norway
| | - Rhîan G. Jacobsen
- Department of Biological Sciences, University of Bergen, Bergen, Vestland, Norway
| | - Aurélia E. Lewis
- Department of Biological Sciences, University of Bergen, Bergen, Vestland, Norway
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3
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Gupta S, Kumar M, Chaudhuri S, Kumar A. The non-canonical nuclear functions of key players of the PI3K-AKT-MTOR pathway. J Cell Physiol 2022; 237:3181-3204. [PMID: 35616326 DOI: 10.1002/jcp.30782] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Revised: 04/05/2022] [Accepted: 05/02/2022] [Indexed: 12/29/2022]
Abstract
The PI3K-AKT-MTOR signal transduction pathway is one of the essential signalling cascades within the cell due to its involvement in many vital functions. The pathway initiates with the recruitment of phosphatidylinositol-3 kinases (PI3Ks) onto the plasma membrane, generating phosphatidylinositol-3,4,5-triphosphate [PtdIns(3,4,5)P3 ] and subsequently activating AKT. Being the central node of the PI3K network, AKT activates the mechanistic target of rapamycin kinase complex 1 (MTORC1) via Tuberous sclerosis complex 2 inhibition in the cytoplasm. Although the cytoplasmic role of the pathway has been widely explored for decades, we now know that most of the effector molecules of the PI3K axis diverge from the canonical route and translocate to other cell organelles including the nucleus. The presence of phosphoinositides (PtdIns) inside the nucleus itself indicates the existence of a nuclear PI3K signalling. The nuclear localization of these signaling components is evident in regulating many nuclear processes like DNA replication, transcription, DNA repair, maintenance of genomic integrity, chromatin architecture, and cell cycle control. Here, our review intends to present a comprehensive overview of the nuclear functions of the PI3K-AKT-MTOR signaling biomolecules.
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Affiliation(s)
- Sakshi Gupta
- Department of Molecular Reproduction, Development & Genetics, Indian Institute of Science, Bangalore, Karnataka, India
| | - Mukund Kumar
- Department of Molecular Reproduction, Development & Genetics, Indian Institute of Science, Bangalore, Karnataka, India
| | - Soumi Chaudhuri
- Department of Molecular Reproduction, Development & Genetics, Indian Institute of Science, Bangalore, Karnataka, India
| | - Arun Kumar
- Department of Molecular Reproduction, Development & Genetics, Indian Institute of Science, Bangalore, Karnataka, India
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Sun Y, Yuan Y, Wu W, Lei L, Zhang L. The effects of locomotion on bone marrow mesenchymal stem cell fate: insight into mechanical regulation and bone formation. Cell Biosci 2021; 11:88. [PMID: 34001272 PMCID: PMC8130302 DOI: 10.1186/s13578-021-00601-9] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2020] [Accepted: 05/04/2021] [Indexed: 02/06/2023] Open
Abstract
Bone marrow mesenchymal stem cells (BMSCs) refer to a heterogeneous population of cells with the capacity for self-renewal. BMSCs have multi-directional differentiation potential and can differentiate into chondrocytes, osteoblasts, and adipocytes under specific microenvironment or mechanical regulation. The activities of BMSCs are closely related to bone quality. Previous studies have shown that BMSCs and their lineage-differentiated progeny (for example, osteoblasts), and osteocytes are mechanosensitive in bone. Thus, a goal of this review is to discuss how these ubiquious signals arising from mechanical stimulation are perceived by BMSCs and then how the cells respond to them. Studies in recent years reported a significant effect of locomotion on the migration, proliferation and differentiation of BMSCs, thus, contributing to our bone mass. This regulation is realized by the various intersecting signaling pathways including RhoA/Rock, IFG, BMP and Wnt signalling. The mechanoresponse of BMSCs also provides guidance for maintaining bone health by taking appropriate exercises. This review will summarize the regulatory effects of locomotion/mechanical loading on BMSCs activities. Besides, a number of signalling pathways govern MSC fate towards osteogenic or adipocytic differentiation will be discussed. The understanding of mechanoresponse of BMSCs makes the foundation for translational medicine.
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Affiliation(s)
- Yuanxiu Sun
- Department of Orthopaedics, The Second Affiliated Hospital and Yuying Children's Hospital of Wenzhou Medical University, Wenzhou, 325000, Zhejiang, China
| | - Yu Yuan
- School of Sport and Health, Guangzhou Sport University, Guangzhou, 510500, Guangdong, China
| | - Wei Wu
- School of Kinesiology, Shanghai University of Sport, Shanghai, 200438, China
| | - Le Lei
- School of Kinesiology, Shanghai University of Sport, Shanghai, 200438, China
| | - Lingli Zhang
- School of Physical Education & Sports Science, South China Normal University, 55 Zhongshan Road West, Tianhe District, Guangzhou, 510631, Guangdong, China.
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Wu Z, Zhou C, Yuan Q, Zhang D, Xie J, Zou S. CTGF facilitates cell-cell communication in chondrocytes via PI3K/Akt signalling pathway. Cell Prolif 2021; 54:e13001. [PMID: 33522639 PMCID: PMC7941231 DOI: 10.1111/cpr.13001] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Revised: 01/06/2021] [Accepted: 01/19/2021] [Indexed: 02/05/2023] Open
Abstract
Purposes Gap junction intercellular communication (GJIC) is essential for articular cartilage to respond appropriately to physical or biological stimuli and maintain homeostasis. Connective tissue growth factor (CTGF), identified as an endochondral ossification genetic factor, plays a vital role in cell proliferation, migration and adhesion. However, how CTGF regulates GJIC in chondrocytes is still unknown. This study aims to explore the effects of CTGF on GJIC in chondrocytes and its potential biomechanism. Materials and methods qPCR was performed to determine the expression of gene profile in the CCN family in chondrocytes. After CTGF treatment, CCK‐8 assay and scratch assay were performed to explore cell proliferation and migration. A scrape loading/dye transfer assay was adopted to visualize GJIC in living chondrocytes. Western blot analysis was done to detect the expression of Cx43 and PI3K/Akt signalling. Immunofluorescence staining was used to show protein distribution. siRNA targeting CTGF was used to detect the influence on cell‐cell communication. Results The CTGF (CCN2) was shown to be the highest expressed member of the CCN family in chondrocytes. CTGF facilitated functional gap junction intercellular communication in chondrocytes through up‐regulation of Cx43 expressions. CTGF activated PI3K/Akt signalling to promote Akt phosphorylation and translocation. Suppressing CTGF also reduced the expression of Cx43. The inhibition of PI3K/Akt signalling decreased the expressions of Cx43 and thus impaired gap junction intercellular communication enhanced by CTGF. Conclusions For the first time, we provide evidence to show CTGF facilitates cell communication in chondrocytes via PI3K/Akt signalling pathway.
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Affiliation(s)
- Zuping Wu
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Chenchen Zhou
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Quan Yuan
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Demao Zhang
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Jing Xie
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
| | - Shujuan Zou
- State Key Laboratory of Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China.,National Clinical Research Center for Oral Diseases, West China Hospital of Stomatology, Sichuan University, Chengdu, China
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AKT/protein kinase B associates with β-actin in the nucleus of melanoma cells. Biosci Rep 2019; 39:BSR20181312. [PMID: 30643008 PMCID: PMC6356016 DOI: 10.1042/bsr20181312] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Revised: 12/21/2018] [Accepted: 01/07/2019] [Indexed: 12/19/2022] Open
Abstract
The serine-threonine kinase AKT/PKB is a critical regulator of various essential cellular processes, and dysregulation of AKT has been implicated in many diseases, including cancer. Despite AKT action is known to function mainly in the cytoplasm, AKT has been reported to translocate to the nucleus. However, very little is known about the mechanism required for the nuclear import of AKT as well as its function in this cellular compartment. In the present study, we characterized the presence of endogenous nuclear AKT in human melanoma cells and addressed the possible role of AKT by exploring its potential association with key interaction nuclear partners. Confocal and Western blot analyses showed that both phosphorylated and non-phosphorylated forms of AKT are present in melanoma cells nuclei. Using mass spectrometry in combination with protein-crosslinking and co-immunoprecipitation, we identified a series of putative protein partners of nuclear AKT, including heterogeneous nuclear ribonucleoprotein (hnRNP), cytoskeleton proteins β-actin, γ-actin, β-actin-like 2 and vimentin. Confocal microscopy and biochemical analyses validated β-actin as a new nuclear AKT-interacting partner. Cofilin and active RNA Polymerase II, two proteins that have been described to interact and work in concert with nuclear actin in transcription regulation, were also found associated with nuclear AKT. Overall, the present study uncovered a yet unrecognized nuclear coupling of AKT and provides insights into the involvement of AKT in the interaction network of nuclear actin.
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Effects of In Utero Thyroxine Exposure on Murine Cranial Suture Growth. PLoS One 2016; 11:e0167805. [PMID: 27959899 PMCID: PMC5154521 DOI: 10.1371/journal.pone.0167805] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2016] [Accepted: 11/21/2016] [Indexed: 01/05/2023] Open
Abstract
Large scale surveillance studies, case studies, as well as cohort studies have identified the influence of thyroid hormones on calvarial growth and development. Surveillance data suggests maternal thyroid disorders (hyperthyroidism, hypothyroidism with pharmacological replacement, and Maternal Graves Disease) are linked to as much as a 2.5 fold increased risk for craniosynostosis. Craniosynostosis is the premature fusion of one or more calvarial growth sites (sutures) prior to the completion of brain expansion. Thyroid hormones maintain proper bone mineral densities by interacting with growth hormone and aiding in the regulation of insulin like growth factors (IGFs). Disruption of this hormonal control of bone physiology may lead to altered bone dynamics thereby increasing the risk for craniosynostosis. In order to elucidate the effect of exogenous thyroxine exposure on cranial suture growth and morphology, wild type C57BL6 mouse litters were exposed to thyroxine in utero (control = no treatment; low ~167 ng per day; high ~667 ng per day). Thyroxine exposed mice demonstrated craniofacial dysmorphology (brachycranic). High dose exposed mice showed diminished area of the coronal and widening of the sagittal sutures indicative of premature fusion and compensatory growth. Presence of thyroid receptors was confirmed for the murine cranial suture and markers of proliferation and osteogenesis were increased in sutures from exposed mice. Increased Htra1 and Igf1 gene expression were found in sutures from high dose exposed individuals. Pathways related to the HTRA1/IGF axis, specifically Akt and Wnt, demonstrated evidence of increased activity. Overall our data suggest that maternal exogenous thyroxine exposure can drive calvarial growth alterations and altered suture morphology.
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8
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Akt drives buffalo casein-derived novel peptide-mediated osteoblast differentiation. J Nutr Biochem 2016; 38:134-144. [DOI: 10.1016/j.jnutbio.2016.08.003] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2016] [Revised: 08/09/2016] [Accepted: 08/28/2016] [Indexed: 01/02/2023]
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Korkmaz Y, Bloch W, Steinritz D, Baumann MA, Addicks K, Schneider K, Raab WHM. Bradykinin Mediates Phosphorylation of eNOS in Odontoblasts. J Dent Res 2016; 85:536-41. [PMID: 16723651 DOI: 10.1177/154405910608500611] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
While the activation of eNOS by Akt/PKB-dependent phosphorylation, leading to NO release, and the inhibition of enzyme activity by bradykinin (BK)-mediated phosphorylation of eNOS in endothelial cells are established, the phosphorylation of eNOS in odontoblasts is unknown. To clarify the regulation of eNOS in odontoblasts by BK, we examined the phosphorylation of eNOS, Akt/PKB, and ERK1/2 in odontoblasts of rat molars. BK (10−7 M) transiently induced the phosphorylation of eNOS at Ser1177, Akt/PKB in odontoblasts, while it induced the phosphorylation of eNOS at Thr495 throughout the entire period of BK treatment. BK receptor 2 antagonist HOE 140 (10−6 M) significantly reduced signal intensities of phosphorylated-eNOS at Ser1177, Thr495, and phosphorylated-Akt/PKB. These results suggest that BK has dual effects on the activation of eNOS in odontoblasts, the Akt/PKB-dependent up-regulation of eNOS by the transient phosphorylation at Ser1177, and the ERK1/2-independent down-regulation of eNOS by the phosphorylation at Thr495.
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Affiliation(s)
- Y Korkmaz
- Department of Operative and Preventive Dentistry and Endodontics, Heinrich-Heine-University, Moorenstr. 5, 40225 Düsseldorf, Germany.
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Golden D, Saria EA, Hansen MF. Regulation of Osteoblast Migration Involving Receptor Activator of Nuclear Factor-kappa B (RANK) Signaling. J Cell Physiol 2015; 230:2951-60. [PMID: 25893522 DOI: 10.1002/jcp.25024] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2014] [Accepted: 04/16/2015] [Indexed: 01/12/2023]
Abstract
Bone remodeling requires osteoclast activation, resorption, and reversal, prior to osteoblast migration into the bone pit. The Receptor Activator of NF-κB (RANK) signaling pathway plays an important role in bone remodeling. Two components of the RANK signaling pathway, RANK Ligand (RANKL) and the decoy receptor Osteoprotegerin (OPG), are expressed predominantly on the surface of osteoblasts, while RANK is principally expressed on the surface of osteoclasts. However, RANK has also been reported to be expressed on the surface of osteoblasts and osteosarcoma tumor cells. Treatment with soluble RANKL (sRANKL) of both normal osteoblasts and osteosarcoma tumor cells activated phosphorylation of ERK, p38(MAPK) , Akt, and p65(NF-κB). However, modified Boyden chamber assays and wound repair assays showed differential response to sRANKL-induced chemotactic migration in normal osteoblasts and osteosarcoma tumor cells. In contrast to previously published results, both normal osteoblasts and osteosarcoma tumor cells responded to sRANKL-induced chemotactic migration but the normal osteoblasts did so only in the presence of an ERK pathway inhibitor. For both normal and tumor cells, the chemotactic response could be blocked by inhibiting the PI3K/Akt or p65(NF-κB) pathway. Response to sRANKL in normal and tumor cells suggests a role for RANK/ERK-mediated signaling in normal osteoblasts chemotactic migration during bone remodeling that is altered or lost during osteosarcoma tumorigenesis.
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Affiliation(s)
- Diana Golden
- Center for Molecular Medicine, University of Connecticut Health Center, Farmington, Connecticut
| | - Elizabeth A Saria
- Center for Molecular Medicine, University of Connecticut Health Center, Farmington, Connecticut
| | - Marc F Hansen
- Center for Molecular Medicine, University of Connecticut Health Center, Farmington, Connecticut
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Krebs K, Ruusmann A, Simonlatser G, Velling T. Expression of FLNa in human melanoma cells regulates the function of integrin α1β1 and phosphorylation and localisation of PKB/AKT/ERK1/2 kinases. Eur J Cell Biol 2015; 94:564-75. [PMID: 26572583 DOI: 10.1016/j.ejcb.2015.10.006] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2015] [Revised: 10/23/2015] [Accepted: 10/29/2015] [Indexed: 11/20/2022] Open
Abstract
FLNa is a ubiquitous cytoskeletal protein that links transmembrane receptors, including integrins, to F-actin and functions as a signalling intermediate. We investigated FLNa's role in the function of integrin-type collagen receptors, EGF-EGFR signalling and regulation of PKB/Akt and ERK1/2. Using FLNa-deficient M2 human melanoma cells, and same cells expressing EGFP-FLNa (M2F) or its Ig-like repeats 1-8+24, 8-15+24 and 16-24, we found that in M2F and M2 8-15+24 cells, EGF induced the increased phosphorylation of PKB/Akt and ERK1/2. In M2F cells EGF induced the localisation of these kinases to cell nucleus and lamellipodia, respectively, and the ERK1/2 phosphorylation-dependent co-immunoprecipitation of FLNa with ERK1/2. Only M2F and M2 8-15+24 cells adhered to and spread on type I collagen whereas on fibronectin all cells behaved similarly. α1β1 and α2β1 were the integrin-type collagen receptors expressed on these cells with primarily α1β1 localising to focal contacts and affecting cell adhesion and migration in a manner dependent on FLNa or its Ig-like repeats 8-15. Our results suggest a role for FLNa repeats 8-15 in the α1-subunit-dependent regulation of integrin α1β1 function, EGF-EGFR signalling to PKB/Akt and ERK1/2, identify ERK1/2 in EGF-induced FLNa-associated protein complexes, and show that the function of different integrins is subjected to differential regulation by FLNa.
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Affiliation(s)
- Kristi Krebs
- Institute of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Anu Ruusmann
- Institute of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Grethel Simonlatser
- Institute of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia
| | - Teet Velling
- Institute of Gene Technology, Tallinn University of Technology, Akadeemia tee 15, 12618 Tallinn, Estonia.
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Frenkel B, White W, Tuckermann J. Glucocorticoid-Induced Osteoporosis. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2015. [PMID: 26215995 DOI: 10.1007/978-1-4939-2895-8_8] [Citation(s) in RCA: 106] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
Osteoporosis is among the most devastating side effects of glucocorticoid (GC) therapy for the management of inflammatory and auto-immune diseases. Evidence from both humans and mice indicate deleterious skeletal effects within weeks of pharmacological GC administration, both related and unrelated to a decrease in bone mineral density (BMD). Osteoclast numbers and bone resorption are also rapidly increased, and together with osteoblast inactivation and decreased bone formation, these changes lead the fastest loss in BMD during the initial disease phase. Bone resorption then decreases to sub-physiological levels, but persistent and severe inhibition of bone formation leads to further bone loss and progressively increased fracture risk, up to an order of magnitude higher than that observed in untreated individuals. Bone forming osteoblasts are thus considered the main culprits in GC-induced osteoporosis (GIO). Accordingly, we focus this review primarily on deleterious effects on osteoblasts: inhibition of cell replication and function and acceleration of apoptosis. Mediating these adverse effects, GCs target pivotal regulatory mechanisms that govern osteoblast growth, differentiation and survival. Specifically, GCs inhibit growth factor pathways, including Insulin Growth Factors, Growth Hormone, Hepatocyte Growth/Scatter Factor and IL6-type cytokines. They also inhibit downstream kinases, including PI3-kinase and the MAP kinase ERK, the latter attributable in part to direct transcriptional stimulation of MAP kinase phosphatase 1. Most importantly, however, GCs inhibit the Wnt signaling pathway, which plays a pivotal role in osteoblast replication, function and survival. They transcriptionally stimulate expression of Wnt inhibitors of both the Dkk and Sfrp families, and they induce reactive oxygen species (ROS), which result in loss of ß-catenin to ROS-activated FoxO transcription factors. Identification of dissociated GCs, which would suppress the immune system without causing osteoporosis, is proving more challenging than initially thought, and GIO is currently managed by co-treatment with bisphosphonates or PTH. These drugs, however, are not ideally suited for GIO. Future therapeutic approaches may aim at GC targets such as those mentioned above, or newly identified targets including the Notch pathway, the AP-1/Il11 axis and the osteoblast master regulator RUNX2.
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Affiliation(s)
- Baruch Frenkel
- Department of Orthopaedic Surgery, Keck School of Medicine, Institute for Genetic Medicine, University of Southern California, 2250 Alcazar Street, CSC-240, Los Angeles, CA, 90033, USA,
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13
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Xiong GM, Do AT, Wang JK, Yeoh CL, Yeo KS, Choong C. Development of a miniaturized stimulation device for electrical stimulation of cells. J Biol Eng 2015; 9:14. [PMID: 26339287 PMCID: PMC4559357 DOI: 10.1186/s13036-015-0012-1] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2015] [Accepted: 08/09/2015] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND Directing cell behaviour using controllable, on-demand non-biochemical methods, such as electrical stimulation is an attractive area of research. While there exists much potential in exploring different modes of electrical stimulation and investigating a wider range of cellular phenomena that can arise from electrical stimulation, progress in this field has been slow. The reasons for this are that the stimulation techniques and customized setups utilized in past studies have not been standardized, and that current approaches to study such phenomena rely on low throughput platforms with restricted variability of waveform outputs. RESULTS Here, we first demonstrated how a variety of cellular responses can be elicited using different modes of DC and square waveform stimulation. Intracellular calcium levels were found to be elevated in the neuroblast cell line SH-SY5Y during stimulation with 5 V square waves and, stimulation with 150 mV/mm DC fields and 1.5 mA DC current resulted in polarization of protein kinase Akt in keratinocytes and elongation of endothelial cells, respectively. Next, a miniaturized stimulation device was developed with an integrated cell chamber array to output multiple discrete stimulation channels. A frequency dividing circuit implemented on the device provides a robust system to systematically study the effects of multiple output frequencies from a single input channel. CONCLUSION We have shown the feasibility of directing cellular responses using various stimulation waveforms, and developed a modular stimulation device that allows for the investigation of multiple stimulation parameters, which previously had to be conducted with different discrete equipment or output channels. Such a device can potentially spur the development of other high throughput platforms for thorough investigation of electrical stimulation parameters on cellular responses.
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Affiliation(s)
- Gordon Minru Xiong
- />School of Materials Science and Engineering, Nanyang Technological University, Block N4.1, Nanyang Avenue, 639798 Singapore
| | - Anh Tuan Do
- />School of Electrical and Electronic Engineering, Nanyang Technological University, Block S2.1, 50 Nanyang Avenue, 639798 Singapore
| | - Jun Kit Wang
- />Residues and Resource Reclamation Centre (R3C), Nanyang Environmental and Water Research Institute (NEWRI), 1 Cleantech Loop, 637141 Singapore
- />Interdisciplinary Graduate School, Nanyang Technological University, 50 Nanyang Avenue, 639798 Singapore
| | - Chee Leong Yeoh
- />School of Electrical and Electronic Engineering, Nanyang Technological University, Block S2.1, 50 Nanyang Avenue, 639798 Singapore
| | - Kiat Seng Yeo
- />School of Electrical and Electronic Engineering, Nanyang Technological University, Block S2.1, 50 Nanyang Avenue, 639798 Singapore
| | - Cleo Choong
- />School of Materials Science and Engineering, Nanyang Technological University, Block N4.1, Nanyang Avenue, 639798 Singapore
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Eapen A, George A. Dentin phosphophoryn in the matrix activates AKT and mTOR signaling pathway to promote preodontoblast survival and differentiation. Front Physiol 2015; 6:221. [PMID: 26300786 PMCID: PMC4528161 DOI: 10.3389/fphys.2015.00221] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2015] [Accepted: 07/21/2015] [Indexed: 11/16/2022] Open
Abstract
Dentin phosphophoryn (DPP) is an extracellular matrix protein synthesized by odontoblasts. It is highly acidic and the phosphorylated protein possesses a strong affinity for calcium ions. Therefore, DPP in the extracellular matrix can promote hydroxyapatite nucleation and can regulate the size of the growing crystal. Besides its calcium binding property, DPP can initiate signaling functions from the ECM (Extracellular matrix). The signals that promote the cytodifferentiation of preodontoblasts to fully functional odontoblasts are not known. In this study, we demonstrate that preodontoblasts on a DPP matrix, generates mechanical and biochemical signals. This is initiated by the ligation of the integrins with the RGD containing DPP. The downstream biochemical response observed is the activation of the AKT(protein kinase B) and mTOR (mammalian target of rapamycin) signaling pathways leading to the activation of the transcription factor NF-κB (Nuclear factor κB). Terminal differentiation of the preodontoblasts was assessed by identifying phosphate and calcium deposits in the matrix using von Kossa and Alizarin red staining respectively. Identifying the signaling pathways initiated by DPP in the dentin matrix would help in devising strategies for dentin tissue engineering.
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Affiliation(s)
- Asha Eapen
- Brodie Tooth Development Genetics and Regenerative Medicine, Department of Oral Biology, University of Illinois at Chicago Chicago, IL, USA
| | - Anne George
- Brodie Tooth Development Genetics and Regenerative Medicine, Department of Oral Biology, University of Illinois at Chicago Chicago, IL, USA
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15
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Zhang Y, Lv J, Guo H, Wei X, Li W, Xu Z. Hypoxia-induced proliferation in mesenchymal stem cells and angiotensin II-mediated PI3K/AKT pathway. Cell Biochem Funct 2015; 33:51-8. [PMID: 25703688 DOI: 10.1002/cbf.3080] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2014] [Revised: 10/06/2014] [Accepted: 11/04/2014] [Indexed: 11/09/2022]
Affiliation(s)
- Yujuan Zhang
- Institute for Fetology; First Hospital of Soochow University; Suzhou China
| | - Juanxiu Lv
- Institute for Fetology; First Hospital of Soochow University; Suzhou China
| | - Hui Guo
- Institute for Fetology; First Hospital of Soochow University; Suzhou China
| | - Xiaoguang Wei
- Institute for Fetology; First Hospital of Soochow University; Suzhou China
| | - Weisheng Li
- Institute for Fetology; First Hospital of Soochow University; Suzhou China
| | - Zhice Xu
- Institute for Fetology; First Hospital of Soochow University; Suzhou China
- Center for Perinatal Biology; Loma Linda University; California USA
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16
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Miura H, Matsuda M, Aoki K. Development of a FRET biosensor with high specificity for Akt. Cell Struct Funct 2013; 39:9-20. [PMID: 24212374 DOI: 10.1247/csf.13018] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022] Open
Abstract
The serine/threonine kinase Akt plays a critical role in cell proliferation, survival, and tumorigenesis. As a central kinase in the phosphatidylinositol 3-kinase pathway, its activation mechanism at the plasma membrane has been well characterized. However, the subcellular Akt activity in living cells is still largely unknown. Fluorescence resonance energy transfer (FRET)-based biosensors have emerged as indispensable tools to visualize the subcellular activities of signaling molecules. In this study, we developed a highly specific FRET biosensor for Akt based on the Eevee backbone, called Eevee-iAkt. Using inhibitors targeting kinases upstream and downstream of Akt, we showed that Eevee-iAkt specifically monitors Akt activity in living cells. To visualize Akt activity at different subcellular compartments, we targeted Eevee-iAkt to raft and non-raft regions of the plasma membrane, mitochondria, and nucleus in HeLa and Cos7 cells. Interestingly, we revealed substantial differences in Akt activation between HeLa and Cos7 cells upon epidermal growth factor (EGF) stimulation: Akt was transiently activated in HeLa cells with comparable levels at the plasma membrane, cytosol, and mitochondria. In contrast, sustained and spatially localized Akt activation was observed in EGF-stimulated Cos7 cells. We found high Akt activity at the plasma membrane, low activity in the cytosol, and no detectable activity at the mitochondria and nucleus in Cos7 cells. The Eevee-iAkt biosensor was shown to be a valuable tool to study the functional relationship between subcellular Akt activation and its anti-apoptotic role in living cells.
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Affiliation(s)
- Haruko Miura
- Laboratory of Bioimaging and Cell Signaling, Graduate School of Biostudies, Kyoto University
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17
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Yadav RB, Burgos P, Parker AW, Iadevaia V, Proud CG, Allen RA, O'Connell JP, Jeshtadi A, Stubbs CD, Botchway SW. mTOR direct interactions with Rheb-GTPase and raptor: sub-cellular localization using fluorescence lifetime imaging. BMC Cell Biol 2013; 14:3. [PMID: 23311891 PMCID: PMC3549280 DOI: 10.1186/1471-2121-14-3] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Accepted: 12/21/2012] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND The mammalian target of rapamycin (mTOR) signalling pathway has a key role in cellular regulation and several diseases. While it is thought that Rheb GTPase regulates mTOR, acting immediately upstream, while raptor is immediately downstream of mTOR, direct interactions have yet to be verified in living cells, furthermore the localisation of Rheb has been reported to have only a cytoplasmic cellular localization. RESULTS In this study a cytoplasmic as well as a significant sub-cellular nuclear mTOR localization was shown , utilizing green and red fluorescent protein (GFP and DsRed) fusion and highly sensitive single photon counting fluorescence lifetime imaging microscopy (FLIM) of live cells. The interaction of the mTORC1 components Rheb, mTOR and raptor, tagged with EGFP/DsRed was determined using fluorescence energy transfer-FLIM. The excited-state lifetime of EGFP-mTOR of ~2400 ps was reduced by energy transfer to ~2200 ps in the cytoplasm and to 2000 ps in the nucleus when co-expressed with DsRed-Rheb, similar results being obtained for co-expressed EGFP-mTOR and DsRed-raptor. The localization and distribution of mTOR was modified by amino acid withdrawal and re-addition but not by rapamycin. CONCLUSIONS The results illustrate the power of GFP-technology combined with FRET-FLIM imaging in the study of the interaction of signalling components in living cells, here providing evidence for a direct physical interaction between mTOR and Rheb and between mTOR and raptor in living cells for the first time.
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Affiliation(s)
- Rahul B Yadav
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Pierre Burgos
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Anthony W Parker
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Valentina Iadevaia
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | - Christopher G Proud
- School of Biological Sciences, University of Southampton, Southampton, SO17 1BJ, UK
| | | | | | - Ananya Jeshtadi
- School of Life Sciences, Headington Campus, Oxford Brookes University, Oxford, OX3 0BP, UK
| | - Christopher D Stubbs
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
| | - Stanley W Botchway
- Central Laser Facility, STFC, Rutherford Appleton Laboratory, Research Complex at Harwell, Didcot, Oxon OX110QX, UK
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18
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Inhibition of protein kinase B activity induces cell cycle arrest and apoptosis during early G1phase in CHO cells. Cell Biol Int 2012; 36:357-65. [DOI: 10.1042/cbi20110092] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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19
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Pineda D, AmpurdanÉS C, Medina MG, Serratosa J, Tusell JM, Saura J, Planas AM, Navarro P. Tissue plasminogen activator induces microglial inflammation via a noncatalytic molecular mechanism involving activation of mitogen-activated protein kinases and Akt signaling pathways and AnnexinA2 and Galectin-1 receptors. Glia 2011; 60:526-40. [DOI: 10.1002/glia.22284] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Accepted: 11/22/2011] [Indexed: 01/03/2023]
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20
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Long RK, Nishida S, Kubota T, Wang Y, Sakata T, Elalieh HZ, Halloran BP, Bikle DD. Skeletal unloading-induced insulin-like growth factor 1 (IGF-1) nonresponsiveness is not shared by platelet-derived growth factor: the selective role of integrins in IGF-1 signaling. J Bone Miner Res 2011; 26:2948-58. [PMID: 21932337 PMCID: PMC3222734 DOI: 10.1002/jbmr.511] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Integrin receptors bind extracellular matrix proteins, and this link between the cell membrane and the surrounding matrix may translate skeletal loading to biologic activity in osteoprogenitor cells. The interaction between integrin and growth factor receptors allows for mechanically induced regulation of growth factor signaling. Skeletal unloading leads to decreased bone formation and osteoblast proliferation that can be explained in part by a failure of insulin-like growth factor 1 (IGF-1) to activate its signaling pathways in unloaded bone. The aim of this study is to determine whether unloading-induced resistance is specific for IGF-1 or common to other skeletal growth factors, and to examine the regulatory role of integrins in IGF-1 signaling. Bone marrow osteoprogenitor (BMOp) cells were isolated from control or hindlimb suspended rats. Unloaded BMOp cells treated with IGF-1 failed to respond with increased proliferation, receptor phosphorylation, or signaling activation in the setting of intact ligand binding, whereas the platelet-derived growth factor (PDGF) response was fully intact. Pretreatment of control BMOp cells with an integrin inhibitor, echistatin, failed to disrupt PDGF signaling but blocked IGF-1 signaling. Recovery of IGF-1 signaling in unloaded BMOp cells followed the recovery of marked reduction in integrin expression induced by skeletal unloading. Selective targeting of integrin subunits with siRNA oligonucleotides revealed that integrin β1 and β3 are required for normal IGF-1 receptor phosphorylation. We conclude that integrins, in particular integrin β3, are regulators of IGF-1, but not PDGF, signaling in osteoblasts, suggesting that PDGF could be considered for investigation in prevention and/or treatment of bone loss during immobilization and other forms of skeletal unloading.
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Affiliation(s)
- Roger K Long
- Department of Medicine, University of California, Davis, CA, USA.
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21
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Hamaguchi N, Ohdaira T, Shinohara A, Iwamatsu A, Ihara S, Fukui Y. Identification of ribosomal protein S3a as a candidate for a novel PI 3-kinase target in the nucleus. Cytotechnology 2011; 40:85-92. [PMID: 19003108 DOI: 10.1023/a:1023970222898] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Phosphatidylinositol 3,4,5-trisphosphate (PIP(3)) is an important lipid second messenger that mediates various cell responses. We have searched for the nuclear PIP(3) binding proteins using PIP(3) analogue beads. A 33 kD protein was detected in this method, which was identified as ribosomal protein S3a by the mass spectrometric analysis. The recombinant S3a protein bound specifically to PIP(3). S3a localized not only in the cytosol but also in the nucleus. Interestingly, not cytosolic but nuclear S3a bound to PIP(3), suggesting different roles of S3a in the cytosol and the nucleus.
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Affiliation(s)
- Norihisa Hamaguchi
- Laboratory of Biological Chemistry, Department of Applied Biological Chemistry, Graduate School of Agriculture and Life Science, University of Tokyo, Yayoi, Bunkyo-ku, Tokyo, Japan
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22
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Activation of the PI3K/Akt signaling pathway through P2Y₂ receptors by extracellular ATP is involved in osteoblastic cell proliferation. Arch Biochem Biophys 2011; 513:144-52. [PMID: 21763267 DOI: 10.1016/j.abb.2011.06.013] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2011] [Revised: 06/28/2011] [Accepted: 06/29/2011] [Indexed: 12/31/2022]
Abstract
We studied the PI3K/Akt signaling pathway modulation and its involvement in the stimulation of ROS 17/2.8 osteoblast-like cell proliferation by extracellular ATP. A dose- and time-dependent increase in Akt-Ser 473 phosphorylation (p-Akt) was observed. p-Akt was increased by ATPγS and UTP, but not by ADPβS. Akt activation was abolished by PI3K inhibitors and reduced by inhibitors of PI-PLC, Src, calmodulin (CaM) but not of CaMK. p-Akt was diminished by cell incubation in a Ca²⁺-free medium but not by the use of L-type calcium channel blockers. The rise in intracellular Ca²⁺ induced by ATP was potentiated in the presence of Ro318220, a PKC inhibitor, and attenuated by the TPA, a known activator of PKC. ATP-dependent p-Akt was diminished by TPA and augmented by Ro318220 treatment in a Ca²⁺-containing but not in a Ca²⁺-free medium. ATP stimulated the proliferation of both ROS 17/2.8 cells and rat osteoblasts through PI3K/Akt. In the primary osteoblasts, ATP induces alkaline phosphatase activity via PI3K, suggesting that the nucleotide promotes osteoblast differentiation. These results suggest that ATP stimulates osteoblast proliferation through PI-PLC linked-P2Y₂ receptors and PI3K/Akt pathway activation involving Ca²⁺, CaM and Src. PKC seems to regulate Akt activation through Src and the Ca²⁺ influx/CaM pathway.
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23
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Mandal CC, Drissi H, Choudhury GG, Ghosh-Choudhury N. Integration of phosphatidylinositol 3-kinase, Akt kinase, and Smad signaling pathway in BMP-2-induced osterix expression. Calcif Tissue Int 2010; 87:533-40. [PMID: 20872216 PMCID: PMC3055166 DOI: 10.1007/s00223-010-9419-3] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/18/2010] [Accepted: 07/23/2010] [Indexed: 12/31/2022]
Abstract
Osterix (Osx), a BMP-2-regulated transcription factor, controls expression of genes essential for osteoblast differentiation. Using progressive deletion of the Osx promoter, we characterized a Smad binding element (SBE) between -552 and -839 bp from its transcription start site. Electrophoretic mobility shift assay and chromatin immunoprecipitation assay showed binding and in vivo recruitment of Smads 1 and 5 to the Osx SBE. Inactivation of PI 3-kinase by the pharmacologic inhibitor Ly294002 or by dominant negative (DN) enzyme significantly blocked BMP-2-induced Osx protein and mRNA expression and Osx transcription. Finally, both DN PI 3-kinase and DN Akt significantly attenuated Smad 5-dependent transcription of Osx, demonstrating the first evidence for a concerted action of PI 3-kinase/Akt signaling with BMP-specific Smads for expression of Osx.
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Affiliation(s)
- Chandi Charan Mandal
- Department of Pathology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA
| | - Hicham Drissi
- Department of Orthopedic Surgery, New England Musculoskeletal Institute, University of Connecticut Health Center, Farmington, CT, USA
| | - Goutam Ghosh Choudhury
- Department of Medicine, University of Texas Health Science Center at San Antonio, San Antonio, TX, USA. Geriatric Research, Education and Clinical Center, South Texas Veterans Health Care System, San Antonio, TX, USA. VA Research, South Texas Veterans Health Care System, San Antonio, TX, USA
| | - Nandini Ghosh-Choudhury
- Department of Pathology, University of Texas Health Science Center at San Antonio, San Antonio, TX 78229, USA. VA Research, South Texas Veterans Health Care System, San Antonio, TX, USA
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24
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Santi SA, Lee H. The Akt isoforms are present at distinct subcellular locations. Am J Physiol Cell Physiol 2010; 298:C580-91. [DOI: 10.1152/ajpcell.00375.2009] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Akt is involved in the regulation of diverse cellular functions such as cell proliferation, energy metabolism, and apoptosis. Although three Akt isoforms are known, the function of each isoform is poorly understood. To gain a better understanding of each Akt isoform, we examined the subcellular localization and expression of each isoform in transformed and nontransformed cells. Akt1 was localized in the cytoplasm, which is in agreement with the currently accepted model that cytoplasmic Akt is translocated and activated at the inner leaflet of the plasma membrane. Interestingly, HEK-293 and HEK-293T cells contained Akt1 in the nucleus and cytoplasm, respectively, suggesting that SV40 T-antigen plays a crucial role in the cytoplasmic localization and activation of Akt1 in HEK-293T. Akt2 was colocalized with the mitochondria, while Akt3 was localized in both the nucleus and nuclear membrane. The subcellular localization of the Akt isoforms was not substantially altered in response to ionizing radiation or EGF. Furthermore, the ablation of one Akt isoform by small interfering RNA (siRNA) did not alter the subcellular location of the remaining isoforms, suggesting that the major function of one isoform is not compensated for by other isoforms. Together, our data support the notion that Akt2 and Akt3 are regulated at the mitochondrial and nuclear membranes, respectively. The mitochondrial localization of Akt2 raises the possibility that this isoform may be involved in both glucose-based energy metabolism and suppression of apoptosis, two Akt functions previously identified with anti-pan-Akt antibodies.
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Affiliation(s)
- Stacey A. Santi
- Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa; and
- Tumor Biology Group, Northeastern Ontario Regional Cancer Centre, Sudbury Regional Hospital and
| | - Hoyun Lee
- Department of Biochemistry, Microbiology, and Immunology, Faculty of Medicine, University of Ottawa, Ottawa; and
- Tumor Biology Group, Northeastern Ontario Regional Cancer Centre, Sudbury Regional Hospital and
- Department of Medical Sciences, Northern Ontario School of Medicine, Sudbury, Ontario, Canada
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25
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Abstract
The phosphoinositide (PI) cycle, discovered over 50 years ago by Mabel and Lowell Hokin, describes a series of biochemical reactions that occur on the inner leaflet of the plasma membrane of cells in response to receptor activation by extracellular stimuli. Studies from our laboratory have shown that the retina and rod outer segments (ROSs) have active PI metabolism. Biochemical studies revealed that the ROSs contain the enzymes necessary for phosphorylation of phosphoinositides. We showed that light stimulates various components of the PI cycle in the vertebrate ROS, including diacylglycerol kinase, PI synthetase, phosphatidylinositol phosphate kinase, phospholipase C, and phosphoinositide 3-kinase (PI3K). This article describes recent studies on the PI3K-generated PI lipid second messengers in the control and regulation of PI-binding proteins in the vertebrate retina.
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Affiliation(s)
- Raju V S Rajala
- Departments of Ophthalmology and Cell Biology, and Dean A. McGee Eye Institute, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA. r
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26
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Forbes K, West G, Garside R, Aplin JD, Westwood M. The protein-tyrosine phosphatase, SRC homology-2 domain containing protein tyrosine phosphatase-2, is a crucial mediator of exogenous insulin-like growth factor signaling to human trophoblast. Endocrinology 2009; 150:4744-54. [PMID: 19589868 DOI: 10.1210/en.2009-0166] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Adequate fetal growth depends on placental transfer of nutrients and gases from the mother; thus, as pregnancy progresses, the placenta must grow to meet the increasing demands of the developing fetus. IGFs control proliferation, differentiation, and survival of trophoblast in first-trimester placenta via intracellular tyrosine kinase signaling cascades, the activation of which is also regulated by tyrosine phosphatases. The protein-tyrosine phosphatase, Src homology-2 domain containing protein tyrosine phosphatase (SHP)-2, is crucial for mouse placental development and is known to mediate IGF actions in other systems. In this study we examined the role of SHP-2 in regulating IGF-mediated proliferation in human trophoblast. Immunohistochemical analysis demonstrated that SHP-2 is expressed strongly in cytotrophoblast and only weakly in syncytium. After small interfering RNA-mediated knockdown of SHP-2 in BeWo choriocarcinoma cells and human first-trimester placental explants, IGF-induced trophoblast proliferation, examined using immunohistochemical analysis of Ki67 and 5-bromo-2'-deoxyuridine incorporation, was significantly reduced (P < 0.05). Kinase activation assays suggested that SHP-2 interacts with the MAPK pathway to mediate these effects. Markers of trophoblast differentiation were elevated after SHP-2 knockdown. This study demonstrates a role for tyrosine phosphatases in human trophoblast and establishes SHP-2 as a component of the IGF signaling pathway that is required for normal placental growth.
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Affiliation(s)
- Karen Forbes
- Maternal and Fetal Health Research Group, University of Manchester, Manchester M13 0JH, United Kingdom
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27
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Abstract
Melanocytes undergo extensive genetic changes during transformation into aggressive melanomas. These changes deregulate genes whose aberrant activity promotes the development of this disease. The phosphoinositide-3-kinase (PI3K) and mitogen-activated protein (MAP) kinase pathways are two key signaling cascades that have been found to play prominent roles in melanoma development. These pathways relay extra-cellular signals via an ordered series of consecutive phosphorylation events from cell surface throughout the cytoplasm and nucleus regulating diverse cellular processes including proliferation, survival, invasion and angiogenesis. It is generally accepted that therapeutic agents would need to target these two pathways to be an effective therapy for the long-term treatment of advanced-stage melanoma patients. This review provides an overview of the PI3 kinase pathway focusing specifically on two members of the pathway, called PTEN and Akt3, which play important roles in melanoma development. Mechanisms leading to deregulation of these two proteins and therapeutic implications of targeting this signaling cascade to treat melanoma are detailed in this review.
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Affiliation(s)
| | - Gavin P. Robertson
- Department of Pharmacology, The Pennsylvania State University College of Medicine, Hershey, PA 17033
- Department of Pathology, The Pennsylvania State University College of Medicine, Hershey, PA 17033
- Department of Dermatology, The Pennsylvania State University College of Medicine, Hershey, PA 17033
- The Foreman Foundation for Melanoma Research, The Pennsylvania State University College of Medicine, Hershey, PA 17033
- Penn State Melanoma Therapeutics Program, The Pennsylvania State University College of Medicine, Hershey, PA 17033
- Penn State Cancer Institute, The Pennsylvania State University College of Medicine, Hershey, PA 17033
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28
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Madhunapantula SV, Robertson GP. The PTEN-AKT3 signaling cascade as a therapeutic target in melanoma. Pigment Cell Melanoma Res 2009. [DOI: 10.1111/j.1755-1471.2009.00585.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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29
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Wine RN, McPherson CA, Harry GJ. IGF-1 and pAKT signaling promote hippocampal CA1 neuronal survival following injury to dentate granule cells. Neurotox Res 2009; 16:280-92. [PMID: 19526277 DOI: 10.1007/s12640-009-9060-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2009] [Revised: 04/20/2009] [Accepted: 04/27/2009] [Indexed: 11/26/2022]
Abstract
Insulin-like growth factor-1 (IGF-1) protects neurons from apoptosis and in vivo offers neuroprotective support to hippocampal CA1 pyramidal neurons following ischemia or seizure. IGF-1 signals through IGF-1 receptors activating phosphytidylinositol 3-kinase (PI3K)/Akt or pMAPK pathways. IGF-1 can be induced with injury and microglia and astrocytes may serve as a source of this neurotrophic factor to promote neuronal survival. An acute systemic injection of trimethyltin (TMT; 2 mg/kg, ip) to mice induces apoptosis of dentate granule neurons within 24 h and a differential response of microglia with ramified microglia present in the CA-1 region. Using this model, we studied the role of IGF-1 in the survival of CA-1 pyramidal neurons under conditions of altered synaptic input due to changes in the dentate gyrus. Within 24 h of injection, IGF-1 mRNA levels were elevated in the hippocampus and IGF-1 protein detected in both astrocytes and microglia. IGF-1 was redistributed within the CA-1 neurons corresponding with an increase in cytoplasmic pAkt, elevated PKBalpha/Akt protein levels, and a decrease in the antagonist, Rho. pMAPK was not detected in CA-1 neurons and ERK2 showed a transient decrease followed by a significant increase, suggesting a lack of recruitment of the pMAPK signaling pathway for neuronal survival. In mice deficient for IGF-1, a similar level of apoptosis was observed in dentate granule neurons as compared to wildtype; however, TMT induced a significant level CA-1 neuronal death, further supporting a role for IGF-1 in the survival of CA-1 neurons.
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Affiliation(s)
- Robert N Wine
- Laboratory of Molecular Toxicology, National Institute of Environmental Health Sciences, National Institutes of Health, P.O. Box 12233, MD C1-04, Research Triangle Park, NC 27709, USA
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30
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Rubio M, Avitabile D, Fischer K, Emmanuel G, Gude N, Miyamoto S, Mishra S, Schaefer EM, Brown JH, Sussman MA. Cardioprotective stimuli mediate phosphoinositide 3-kinase and phosphoinositide dependent kinase 1 nuclear accumulation in cardiomyocytes. J Mol Cell Cardiol 2009; 47:96-103. [PMID: 19269295 DOI: 10.1016/j.yjmcc.2009.02.022] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/13/2008] [Revised: 02/04/2009] [Accepted: 02/20/2009] [Indexed: 12/20/2022]
Abstract
The phosphoinositide 3-kinase (PI3K)/phosphoinositide dependent kinase 1 (PDK1) signaling pathway exerts cardioprotective effects in the myocardium through activation of key proteins including Akt. Activated Akt accumulates in nuclei of cardiomyocytes suggesting that biologically relevant targets are located in that subcellular compartment. Nuclear Akt activity could be potentiated in both intensity and duration by the presence of a nuclear-associated PI3K/PDK1 signaling cascade as has been described in other non-myocyte cell types. PI3K/PDK1 distribution was determined in vitro and in vivo by immunostaining and nuclear extraction of cultured rat neonatal cardiomyocytes or transgenic mouse hearts. Results show that PI3K and PDK1 are present at a basal level in cardiomyocytes nuclei and that cardioprotective stimulation with atrial natriuretic peptide (ANP) increases their nuclear localization. In comparison, overexpression of nuclear-targeted Akt does not mediate increased translocation of either PI3K or PDK1 indicating that accumulation of Akt does not drive PI3K or PDK1 into the nuclear compartment. Furthermore, PI3K and phospho-Akt(473) show parallel temporal accumulation in the nucleus following (MI) infarction challenge. These findings demonstrate the presence of a dynamically regulated nuclear-associated signaling cascade involving PI3K and PDK that presumably influences nuclear Akt activation.
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Affiliation(s)
- Marta Rubio
- SDSU Heart Institute, Department of Biology, San Diego State University, 5500 Campanile Drive, San Diego, CA 92182, USA.
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31
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The expression of protein kinase B in gastric cancer cell apoptosis induced by 12-O-tetradecanoylphorbol-1, 3-acetate. Cell Mol Biol Lett 2009; 14:466-80. [PMID: 19238332 PMCID: PMC6276013 DOI: 10.2478/s11658-009-0013-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2008] [Accepted: 01/17/2009] [Indexed: 12/20/2022] Open
Abstract
Protein kinase B (PKB/Akt) is a serine-threonine kinase functioning downstream of phosphatidylinositol 3-kinase (PI-3 kinase) in response to mitogen or growth factor stimulation. In several cell types, it plays an important anti-apoptotic role. TPA is a potent regulator of the growth of many different cell types. Here, we detected that TPA could induce cell apoptosis in the gastric cancer cell line, BGC-823. We also found that TPA inhibited the expression of PKB/Akt in a TPA concentration- and time-dependent manner. Furthermore, TPA inhibited the phosphorylation of PKB at Ser473, but did not affect the phosphorylation of Thr308. It only attenuated the expression of PKB/Akt and the phosphorylation of Ser473 in the cell nucleus, whereas it did not change the PKB/Akt distribution in BGC-823 cells. These results suggest that PKB/Akt inhibition by TPA may be the important factor in the mechanism of effect of TPA on gastric cell lines.
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32
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Barksdale KA, Bijur GN. The basal flux of Akt in the mitochondria is mediated by heat shock protein 90. J Neurochem 2009; 108:1289-99. [PMID: 19187436 DOI: 10.1111/j.1471-4159.2009.05878.x] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Akt is a known client protein of heat shock protein 90 (HSP90). We have found that HSP90 is responsible for Akt accumulation in the mitochondria in unstimulated cells. Treatment of SH-SY5Y neuroblastoma cells and human embryonic kidney cells with the HSP90 inhibitors novobiocin and geldanamycin caused substantial decreases in the level of Akt in the mitochondria without affecting the level of Akt in the cytosol. Moreover, intracerebroventricular injection of novobiocin into mice brains decreased Akt levels in cortical mitochondria. Knockdown of HSP90 expression with short interfering RNA also caused a significant decrease in Akt levels in the mitochondria without affecting total Akt levels. Using a mitochondrial import assay it was found that Akt is transported into the mitochondria. Furthermore, it was found that the mitochondrial import of Akt was independent of Akt activation as both an unmodified Akt and constitutively active mutant Akt; both readily accumulated in the mitochondria in an HSP90-dependent manner. Interestingly, incubation of isolated mitochondria with constitutively active Akt caused visible alterations in mitochondrial morphology, including pronounced remodeling of the mitochondrial matrix. This effect was blocked when Akt was mostly excluded from the mitochondria with novobiocin treatment. These results indicate that the level of Akt in the mitochondria is dependent on HSP90 chaperoning activity and that Akt import can cause dynamic changes in mitochondrial configuration.
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Affiliation(s)
- Keri A Barksdale
- Department of Psychiatry and Behavioral Neurobiology, University of Alabama at Birmingham, 35294-0017, USA
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Measurement of PTEN activity in vivo by imaging phosphorylated Akt. Methods Mol Biol 2009. [PMID: 19160672 DOI: 10.1007/978-1-60327-115-8_14] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register]
Abstract
This chapter describes an indirect approach to measure PTEN's lipid phosphatase activity in vivo. PTEN counteracts phosphatidylinositol 3-kinase action in dephosphorylating 3-phosphorylated phosphoinositides. Therefore, PtdIns(3,4,5)P3-dependent activation and phosphorylation of the survival kinase Akt can be used as readout for cellular PTEN activity. Here we have outlined a detailed procedure employing a phosphoserine-specific anti-Akt antibody to examine the content of phosphorylated Akt by immunofluorescence and its dependence on PTEN activity.
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Jackson TC, Rani A, Kumar A, Foster TC. Regional hippocampal differences in AKT survival signaling across the lifespan: implications for CA1 vulnerability with aging. Cell Death Differ 2008; 16:439-48. [PMID: 19039330 PMCID: PMC2680608 DOI: 10.1038/cdd.2008.171] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
Distinct neuronal populations differ by the degree of damage caused from cellular stress. Hippocampal neurons of area CA1 are especially vulnerable to several stressors that increase as age advances. We show here that survival signaling, as measured by activated protein kinase B (AKT), was significantly reduced in the nuclear CA1 region across the lifespan compared with CA3. In agreement with these findings, the pro-apoptotic protein and AKT nuclear substrate, forkhead box O3a transcription factor (FOXO3a), were significantly higher in CA1. Further, regional differences in PH domain and leucine-rich repeat protein phosphatase 1 (PHLPP1), a recently discovered inhibitor of AKT, inversely correlated with nuclear phosphorylated AKT at Ser473. Altogether, our data suggest that regional differences in nuclear levels of activated AKT may contribute to regional differences in hippocampal vulnerability and implicate PHLPP1 as a potential target for therapeutic intervention to improve hippocampal health.
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Affiliation(s)
- T C Jackson
- Department of Neuroscience, McKnight Brain Institute, University of Florida, Gainesville, FL 32610-0244, USA
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35
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Serine 396 of PDK1 is required for maximal PKB activation. Cell Signal 2008; 20:2038-49. [DOI: 10.1016/j.cellsig.2008.07.015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2008] [Revised: 07/10/2008] [Accepted: 07/17/2008] [Indexed: 11/23/2022]
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36
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Li G, Rajala A, Wiechmann AF, Anderson RE, Rajala RVS. Activation and membrane binding of retinal protein kinase Balpha/Akt1 is regulated through light-dependent generation of phosphoinositides. J Neurochem 2008; 107:1382-97. [PMID: 18823366 DOI: 10.1111/j.1471-4159.2008.05707.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Akt is a phospholipid-binding protein and the downstream effector of the phosphoinositide 3-kinase (PI3K) pathway. Akt has three isoforms: Akt1, Akt2, and Akt3. All of these isoforms are expressed in rod photoreceptor cells, but the individual functions of each isoform are not known. In this study, we found that light induces the activation of Akt1. The membrane binding of Akt1 to rod outer segments (ROS) is insulin receptor (IR)/PI3K-dependent as demonstrated by reduced binding of Akt1 to ROS membranes of photoreceptor-specific IR knockout mice. Membrane binding of Akt1 is mediated through its Pleckstrin homology (PH) domain. To determine whether binding of the PH domain of Akt1 to photoreceptor membranes is regulated by light, various green fluorescent protein (GFP)/Akt1-PH domain fusion proteins were expressed in rod photoreceptors of transgenic Xenopus laevis under the control of the Xenopus opsin promoter. The R25C mutant PH domain of Akt1, which does not bind phosphoinositides, failed to associate with plasma membranes in a light-dependent manner. This study suggests that light-dependent generation of phosphoinositides regulates the activation and membrane binding of Akt1 in vivo. Our results also suggest that actin cytoskeletal organization may be regulated through light-dependent generation of phosphoinositides.
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Affiliation(s)
- Guiyuan Li
- Departments of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA
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37
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Missiroli S, Etro D, Buontempo F, Ye K, Capitani S, Neri LM. Nuclear translocation of active AKT is required for erythroid differentiation in erythropoietin treated K562 erythroleukemia cells. Int J Biochem Cell Biol 2008; 41:570-7. [PMID: 18694847 DOI: 10.1016/j.biocel.2008.07.002] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2008] [Revised: 06/25/2008] [Accepted: 07/10/2008] [Indexed: 11/28/2022]
Abstract
Erythroid differentiation of human erythroleukemia cell line K562 induced by erythropoietin is a complex process that involves modifications at nuclear level, including nuclear translocation of phosphatidyl-inositol 3-kinase. In this work we show that erythropoietin stimulation of K562 cells can induce nuclear translocation of active Akt, a downstream molecule of the phosphatidyl-inositol 3-kinase signaling pathway. Akt shows a peak of activity in whole cell homogenates at earlier stage when compared to the nucleus, which shows a peak delayed of 10 min. Akt increases its intranuclear amount and activity rapidly and transiently in response to EPO. Almost all Akt kinase that translocates to the nucleus shows a marked phosphorylation on serine 473. Nuclear enzyme translocation is blocked by the phosphatidyl-inositol 3-kinase inhibitor Ly294002 or Wortmannin. The specific Akt pharmacological inhibitor VI, VII and VIII that act as blocking enzyme activation inhibited translocation as well, whereas Akt inhibitor IX, that inhibits Akt activity, did not block Akt nuclear translocation. When cells were treated by means of siRNA sequences or with the Akt inhibitors the differentiation process was arrested, thus showing the requirement of the nuclear translocation of the active enzyme to differentiate. These findings strongly suggest that the intranuclear translocation of active Akt kinase represents an important step in the signaling pathway that mediates erythropoietin-induced erythroid differentiation.
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Affiliation(s)
- Silvia Missiroli
- Dipartimento di Morfologia ed Embriologia, Sezione di Anatomia Umana, Signal Transduction Unit, Universita' di Ferrara, Ferrara, Italy
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Rosner M, Hengstschläger M. Cytoplasmic and nuclear distribution of the protein complexes mTORC1 and mTORC2: rapamycin triggers dephosphorylation and delocalization of the mTORC2 components rictor and sin1. Hum Mol Genet 2008; 17:2934-48. [PMID: 18614546 DOI: 10.1093/hmg/ddn192] [Citation(s) in RCA: 181] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
The mammalian target of rapamycin (mTOR) is part of two distinct complexes, mTORC1, containing raptor and mLST8, and mTORC2, containing rictor, mLST8 and sin1. Although great endeavors have already been made to elucidate the function and regulation of mTOR, the cytoplasmic nuclear distribution of the mTOR complexes is unknown. Upon establishment of the proper experimental conditions, we found mTOR, mLST8, rictor and sin1 to be less abundant in the nucleus than in the cytoplasm of non-transformed, non-immortalized, diploid human primary fibroblasts. Although raptor is also high abundant in the nucleus, the mTOR/raptor complex is predominantly cytoplasmic, whereas the mTOR/rictor complex is abundant in both compartments. Rapamycin negatively regulates the formation of both mTOR complexes, but the molecular mechanism of its effects on mTORC2 remained elusive. We describe that in primary cells short-term treatment with rapamycin triggers dephosphorylation of rictor and sin1 exclusively in the cytoplasm, but does not affect mTORC2 assembly. Prolonged drug treatment leads to complete dephosphorylation and cytoplasmic translocation of nuclear rictor and sin1 accompanied by inhibition of mTORC2 assembly. The distinct cytoplasmic and nuclear upstream and downstream effectors of mTOR are involved in many cancers and human genetic diseases, such as tuberous sclerosis, Peutz-Jeghers syndrome, von Hippel-Lindau disease, neurofibromatosis type 1, polycystic kidney disease, Alzheimer's disease, cardiac hypertrophy, obesity and diabetes. Accordingly, analogs of rapamycin are currently tested in many different clinical trials. Our data allow new insights into the molecular consequences of mTOR dysregulation under pathophysiological conditions and should help to optimize rapamycin treatment of human diseases.
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Affiliation(s)
- Margit Rosner
- Medical Genetics, Medical University of Vienna, Währinger Gürtel 18-20, 1090 Vienna, Austria
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39
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Akt1/protein kinase B alpha is involved in gastric cancer progression and cell proliferation. Dig Dis Sci 2008; 53:1801-10. [PMID: 18379876 DOI: 10.1007/s10620-007-9824-2] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Accepted: 03/16/2007] [Indexed: 12/13/2022]
Abstract
Akt (also known as protein kinase B, PKB) is involved in a variety of biological processes, for example cell development, proliferation, and angiogenesis. Clinical studies in support of the idea that increased activity of Akt could contribute directly to gastric carcinogenesis are rare, however. In this study we discovered that phospho-Akt1 was overexpressed in human gastric cancers and its levels correlated with tumor differentiation and pTNM. Akt1 activation promoted cell survival, because the phosphatidylinositol 3-kinase(PI3K) inhibitor LY294002 inhibited Akt1 phosphorylation and inhibited cell growth, especially in cells with active Akt1. Dominant negative Akt inhibited proliferation of gastric cancer cells and induced G1 cell-cycle arrest whereas constitutively active Akt increased cell proliferation. We have therefore identified Akt1 as an active kinase that contributes to gastric cancer progression and promotes proliferation of gastric cancer cells.
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40
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Mortenson MM, Galante JG, Gilad O, Schlieman MG, Virudachalam S, Kung HJ, Bold RJ. BCL-2 functions as an activator of the AKT signaling pathway in pancreatic cancer. J Cell Biochem 2008; 102:1171-9. [PMID: 17960583 DOI: 10.1002/jcb.21343] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
BCL-2 is the prototypic anti-apoptotic protein involved in the regulation of apoptosis. Overexpression of BCL-2 is common in pancreatic cancer and confers resistance to the apoptotic effect of chemo- and radiotherapy. Although these cellular effects of BCL-2 are traditionally related to pathways involving the mitochondrial membrane, we sought to investigate whether BCL-2 is involved in other signaling pathways regulating cell survival and focused on AKT. We examined the effect of overexpression of BCL-2 in the MIA-PaCa-2 human pancreatic cancer cell line on the function and subcellular location of AKT. We observed that the stable subclones of MIA-PaCa-2 overexpressing BCL-2 demonstrated increased activity of AKT as well as IKK (a downstream target of AKT), increasing the transcriptional activity of NF-kappaB. Using immunoprecipitation techniques, we observed co-immunoprecipitation of AKT and BCL-2. Immunocytochemistry demonstrated co-localization of BCL-2 and AKT, which was abrogated by treatment with HA14-1, a small molecule inhibitor of BH-3-mediated protein interaction by BCL-2. Furthermore, treatment with HA14-1 decreased phosphorylation of AKT and increased sensitivity to the apoptotic effect of the chemotherapeutic agent, paclitaxel. These results demonstrate an additional mechanism of regulation of cell survival mediated by BCL-2, namely through AKT activation, in the MIA-PaCa-2 pancreatic cancer cell line. Therefore, directed inhibition of BCL-2 may alter diverse pathways controlling cell survival and overcome the apoptotic resistance that is the hallmark of pancreatic cancer.
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Affiliation(s)
- Melinda M Mortenson
- Department of Surgery, University of California Davis School of Medicine, Sacramento, California, USA
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41
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Administration of Triiodo-l-thyronine into Dorsal Hippocampus Alters Phosphorylation of Akt, Mammalian Target of Rapamycin, p70S6 Kinase and 4E-BP1 in Rats. Neurochem Res 2007; 33:1065-76. [DOI: 10.1007/s11064-007-9551-2] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2007] [Accepted: 11/15/2007] [Indexed: 11/26/2022]
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42
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Kwon O, Kim KA, He L, Jung M, Jeong SJ, Ahn JS, Kim BY. Complex formation of p65/RelA with nuclear Akt1 for enhanced transcriptional activation of NF-kappaB. Biochem Biophys Res Commun 2007; 365:771-6. [PMID: 18035048 DOI: 10.1016/j.bbrc.2007.11.037] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2007] [Accepted: 11/09/2007] [Indexed: 11/28/2022]
Abstract
Akt1 was revealed to interact with Ki-Ras in the cytoplasm of Ki-Ras-transformed human prostate epithelial cells, 267B1/K-ras. Moreover, p65/RelA in the nucleus was found to interact with both Ki-Ras and Akt1, suggesting the nuclear translocation of Akt1:Ki-Ras complex for NF- kappaB activation. In support of this, compared with wild type Akt1, the dominant negative Akt1 mutant was decreased in its nuclear expression, reducing the Ki-Ras-induced NF-kappaB transcriptional activation. Moreover, inhibitors of Ras (sulindac sulfide and farnesyltransferase inhibitor I) or PI3K/Akt (wortmannin), reduced the amounts of Akt1 and Ki-Ras in the nucleus as well as partial NF-kappaB activity. The complete inhibition of Ki-Ras-induced NF-kappaB activation, however, could only be obtained by combined treatment with wortmannin and proteasome inhibitor-1. Accordingly, clonogenic assay showed Akt1 contribution to IkappaBalpha-mediated NF-kappaB activation for oncogenic cell growth by Ki-Ras. Our data suggest a crucial role of Ki-Ras:Akt1 complex in NF-kappaB transcriptional activation and enhancement of cell survival.
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Affiliation(s)
- Osong Kwon
- Functional Metabolomics Research Center, KRIBB, Yuseong, Daejeon, Republic of Korea
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43
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Zhang Y, Zhang L, Yan M, Zheng X. Inhibition of phosphatidylinositol 3-kinase causes cell death in rat osteoblasts through inactivation of Akt. Biomed Pharmacother 2007; 61:277-84. [PMID: 17433610 DOI: 10.1016/j.biopha.2007.02.014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2006] [Accepted: 02/12/2007] [Indexed: 12/29/2022] Open
Abstract
Previous evidences indicated that phosphatidylinositol 3-kinase (PI3-kinase) is an important regulatory molecule that is involved in the cell growth and survival, and inhibition of the PI3-kinase activity enhances apoptotic cell death. However, the relationship between PI3-kinase activity and osteoblasts, capable of new bone formation, remained unknown. In the present study, pharmacological inhibitor of PI3-kinase LY294002 was used to observe the role of the PI3-kinase in the growth of rat osteoblasts. To identify its molecular mechanism, Western blots analysis and immunocytochemistry were applied to examine changes of Akt phosphorylation and its distribution. Our data showed that inhibition of PI3-kinase activity significantly triggered the decrease of cell growth, cell apoptosis and loss of mitochondrial membrane potential (Deltapsi(m)). Osteoblastic dysfunction stimulated by LY294002 was accompanied by inactivation of Akt and its redistribution. In all these results demonstrated that inhibition of PI3-kinase induced apoptotic cell death, which was mediated by inactivation of Akt pathway in rat osteoblasts.
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Affiliation(s)
- Yun Zhang
- Department of Biomedical Engineering, Key Laboratory of Biomedical Engineering of Ministry of Education, Zhejiang University, Zheda Road 38, 310027 Hangzhou, China
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44
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Kim SJ, Kim SY, Kwon CH, Kim YK. Differential effect of FGF and PDGF on cell proliferation and migration in osteoblastic cells. Growth Factors 2007; 25:77-86. [PMID: 17852407 DOI: 10.1080/08977190701398977] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
It has been known that growth factors such as fibroblast growth factor (FGF) and platelet-derived growth factor (PDGF) can promote proliferation and migration in a variety of cell types including osteoblastic cells. However, the mechanism underlying their action has not been clearly defined. The present study was undertaken to examine the effect of FGF and PDGF on cell proliferation and migration and to determine the role of extracellular signal-regulated kinase (ERK) and Akt in action of FGF and PDGF in osteoblastic cells. FGF enhanced proliferation in a dose- and time-dependent manner, whereas it did not affect cell migration. FGF induced a transient activation of ERK, but not Akt, which was inhibited by an inhibitor of MEK, the upstream kinase of ERK, but not by inhibitors of PI3K/Akt (LY294002), epidermal growth factor receptor (EGFR, AG1478), and Src (PP2). FGF-induced proliferation was inhibited by inhibitors of MEK/ERK and Src pathways. Exposure of cells to FGF stimulated transition of cell cycle from the G1 phase to S phase and increased phosphorylation of Rb. FGF-induced phosphorylation of Rb was attenuated by inhibitors of MEK/ERK and Src pathways. Cell migration studies indicated that PDGF stimulated migration, but it had no effect on cell proliferation. PDGF induced activation of ERK and Akt. The ERK activatin was inhibited by the Src inhibitor and the Akt activation was inhibited by inhibitors of EGFR and Src. PDGF-induced migration was inhibited by inhibitors of MEK/ERK, PI3K/Akt, EGFR and Src pathways. Taken together, these findings suggest that the MEK/ERK and Src pathways play an important role in the FGF-induced proliferation and signaling pathways involving MEK/ERK, EGFR, Src and PI3K/Akt mediate the PDGF-induced migration. These data are of importance in understanding the roles of these growth factors in osteoblastic cell proliferation and migration.
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Affiliation(s)
- Su Jin Kim
- Department of Pediatrics, College of Medicine, Pusan National University, Pusan 602-739, South Korea.
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45
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Boonstra J. Identification of a restriction point at the M/G1 transition during the ongoing cell cycle. ACTA ACUST UNITED AC 2007; 47:208-21. [PMID: 17337291 DOI: 10.1016/j.advenzreg.2006.11.001] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Affiliation(s)
- Johannes Boonstra
- Cellular Architecture and Dynamics, Faculty of Sciences, Padualaan 8, University Utrecht, 3584 CH Utrecht, The Netherlands.
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46
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Barnes NLP, Warnberg F, Farnie G, White D, Jiang W, Anderson E, Bundred NJ. Cyclooxygenase-2 inhibition: effects on tumour growth, cell cycling and lymphangiogenesis in a xenograft model of breast cancer. Br J Cancer 2007; 96:575-82. [PMID: 17285134 PMCID: PMC2360050 DOI: 10.1038/sj.bjc.6603593] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Cyclooxygenase-2 (COX-2) is associated with poor-prognosis breast cancer. We used a nude mouse xenograft model to determine the effects of COX-2 inhibition in breast cancer. Oestrogen receptor (ER)-positive MCF7/HER2-18 and ER-negative MDAMB231 breast cancer cell lines were injected into nude mice and allowed to form tumours. Mice then received either chow containing Celecoxib (a COX-2 inhibitor) or control and tumour growth measured. Tumour proliferation, apoptosis, COX-2, lymphangiogenesis and angiogenesis were assessed by immunohistochemistry (IHC), Western blotting or Q-PCR. Celecoxib inhibited median tumour growth in MCF7/HER2-18 (58.7%, P=0.029) and MDAMB231 (46.3%, P=0.0002) cell lines compared to control. Cyclooxygenase-2 expression decreased following Celecoxib treatment (MCF7/HER2-18 median control 65.3% vs treated 22.5%, P=0.0001). Celecoxib increased apoptosis in MCF7/HER2-18 tumours (TUNEL 0.52% control vs 0.73% treated, P=0.0004) via inactivation of AKT (median pAKTser473 57.3% control vs 35.5% treated, P=0.0001 – confirmed at Western blotting). Q-PCR demonstrated decreased podoplanin RNA (lymphangiogenesis marker) in the MCF7/HER2-18 – median 2.9 copies treated vs 66.6 control (P=0.05) and MDAMB231-treated groups – median 160.7 copies vs 0.05 control copies (P=0.015), confirmed at IHC. Cyclooxygenase-2 is associated with high levels of activated AKTser473 and lymphangiogenesis in breast cancer. Cyclooxygenase-2 inhibition decreases tumour growth, and may potentially decrease recurrence, by inactivating AKT and decreasing lymphangiogenesis.
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Affiliation(s)
- N L P Barnes
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK
| | - F Warnberg
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK
| | - G Farnie
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK
| | - D White
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK
| | - W Jiang
- The Department of Angiogenesis and Metastasis Research, University of Wales College of Medicine, Cardiff, Wales, UK
| | - E Anderson
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK
| | - N J Bundred
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK
- Department of Academic Surgery, South Manchester University Hospital, Research and Education Building 2nd Floor, Southmoor Road, Wythenshawe, Manchester M23 9LT, UK. E-mail:
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Hanai Y, Tokuda H, Ohta T, Matsushima-Nishiwaki R, Takai S, Kozawa O. Phosphatidylinositol 3-kinase/Akt auto-regulates PDGF-BB-stimulated interleukin-6 synthesis in osteoblasts. J Cell Biochem 2007; 99:1564-71. [PMID: 16817229 DOI: 10.1002/jcb.21007] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
It has been reported that platelet-derived growth factor (PDGF)-BB stimulates the synthesis of interleukin (IL)-6 in osteoblasts. In the present study, we investigated whether the phosphatidylinositol 3-kinase (PI3K)/Akt is involved in the PDGF-BB-induced IL-6 synthesis in osteoblast-like MC3T3-E1 cells. PDGF-BB markedly induced the phosphorylation of Akt and GSK-3beta. Akt inhibitor, 1L-6-hydroxymethyl-chiro-inositol 2-(R)-2-O-methyl-3-O-octadecylcarbonate, significantly amplified the synthesis of IL-6 by PDGF-BB. The PDGF-BB-induced GSK-3beta phosphorylation was suppressed by the Akt inhibitor. The IL-6 synthesis stimulated by PDGF-BB was markedly enhanced by LY294002 and wortmannin, inhibitors of PI3K. Wortmannin and LY294002 suppressed the PDGF-BB-induced phosphorylation of Akt and GSK-3beta. Taken together, these results strongly suggest that PI3K/Akt negatively regulates the PDGF-BB-stimulated IL-6 synthesis in osteoblasts.
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Affiliation(s)
- Yoshiteru Hanai
- Department of Clinical Laboratory, National Hospital for Geriatric Medicine, National Center for Geriatrics and Gerontology, Obu, Aichi 474-8511, Japan
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Guenou H, Kaabeche K, Dufour C, Miraoui H, Marie PJ. Down-regulation of ubiquitin ligase Cbl induced by twist haploinsufficiency in Saethre-Chotzen syndrome results in increased PI3K/Akt signaling and osteoblast proliferation. THE AMERICAN JOURNAL OF PATHOLOGY 2006; 169:1303-11. [PMID: 17003487 PMCID: PMC1698848 DOI: 10.2353/ajpath.2006.060102] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Genetic mutations of Twist, a basic helix-loop-helix transcription factor, induce premature fusion of cranial sutures in Saethre-Chotzen syndrome (SCS). We report here a previously undescribed mechanism involved in the altered osteoblastogenesis in SCS. Cranial osteoblasts from an SCS patient with a Twist mutation causing basic helix-loop-helix deletion exhibited decreased expression of E3 ubiquitin ligase Cbl compared with wild-type osteoblasts. This was associated with decreased ubiquitin-mediated degradation of phosphatidyl inositol 3 kinase (PI3K) and increased PI3K expression and PI3K/Akt signaling. Increased PI3K immunoreactivity was also found in osteoblasts in histological sections of affected cranial sutures from SCS patients. Transfection with Twist or Cbl abolished the increased PI3K/Akt signaling in Twist mutant osteoblasts. Forced overexpression of Cbl did not correct the altered expression of osteoblast differentiation markers in Twist mutant cells. In contrast, pharmacological inhibition of PI3K/Akt, but not ERK signaling, corrected the increased cell growth in Twist mutant osteoblasts. The results show that Twist haploinsufficiency results in decreased Cbl-mediated PI3K degradation in osteoblasts, causing PI3K accumulation and activation of PI3K/Akt-dependent osteoblast growth. This provides genetic and biochemical evidence for a role for Cbl-mediated PI3K signaling in the altered osteoblast phenotype induced by Twist haploinsufficiency in SCS.
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Affiliation(s)
- Hind Guenou
- Laboratory of Osteoblast Biology and Pathology, INSERM U 606, Lariboisière Hospital, 2 rue Ambroise Paré, 75475 Paris Cedex 10, France
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49
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Li M, Chiu JF, Mossman BT, Fukagawa NK. Down-regulation of manganese-superoxide dismutase through phosphorylation of FOXO3a by Akt in explanted vascular smooth muscle cells from old rats. J Biol Chem 2006; 281:40429-39. [PMID: 17079231 DOI: 10.1074/jbc.m606596200] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Manganese-superoxide dismutase (MnSOD) is one of the major cellular antioxidant defense systems. To study the effect of age on the regulation of MnSOD in the vasculature, we compared MnSOD expression and its transcriptional regulation in explanted vascular smooth muscle cells (VSMC) isolated from old (24 months old) versus young (6 months old) rats and grown in a normal (5 mM) or high (12.5 and 25 mM) glucose or tumor necrosis factor alpha (5 ng/ml) environment to induce oxidative stress. Both MnSOD protein and activity were reduced in VSMC from old compared with young animals. FOXO3a, a member of the family of Forkhead transcription factors, interacted with the promoter of the rat MnSOD gene at a specific binding site. Inhibition of FOXO3a transcription with small interfering RNA led to a reduction in MnSOD gene expression. VSMC from old rats had increased phosphorylated FOXO3a at Ser(253), which paralleled the reduction of MnSOD protein. Treatment of VSMC with 5 nm insulin-like growth factor-1 induced phosphorylation of Akt and FOXO3a over time, repressing FOXO3a DNA binding and consequently MnSOD gene expression. Furthermore, Akt activity was selectively increased in VSMC from the old, supporting the hypothesis that increased age-related Akt activity might be responsible for the phosphorylation and inactivation of FOXO3a, which in turn down-regulates MnSOD transcription.
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Affiliation(s)
- Muyao Li
- Departments of Medicine, Pathology, and Biochemistry, University of Vermont College of Medicine, Burlington, Vermont 05405, USA
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50
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Xuan Nguyen TL, Choi JW, Lee SB, Ye K, Woo SD, Lee KH, Ahn JY. Akt phosphorylation is essential for nuclear translocation and retention in NGF-stimulated PC12 cells. Biochem Biophys Res Commun 2006; 349:789-98. [PMID: 16956580 DOI: 10.1016/j.bbrc.2006.08.120] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2006] [Accepted: 08/16/2006] [Indexed: 11/23/2022]
Abstract
Nerve growth factor (NGF) elicits Akt translocation into the nucleus, where it phosphorylates nuclear targets. Here, we describe that Akt phosphorylation can promote the nuclear translocation of Akt and is necessary for its nuclear retention. Overexpression of Akt-K179A, T308A, S473A-mutant failed to show either nuclear translocation or nuclear Akt phosphorylation, whereas expression of wild-type counterpart elicited profound Akt phosphorylation and induced nuclear translocation under NGF stimulation. Employing the PI3K inhibitor and a variety of mutants PI3K, we showed that nuclear translocation of Akt was mediated by activation of PI3K, and Akt phosphorylation status in the nucleus required PI3K activity. Thus the activity of PI3K might contribute to the nuclear translocation of Akt, and that Akt phosphorylation is essential for its nuclear retention under NGF stimulation conditions.
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Affiliation(s)
- Truong Le Xuan Nguyen
- Department of Molecular Cell Biology, Center for Molecular Medicine, Samsung Biomedical Research Institute, Sungkyunkwan University School of Medicine, Suwon 440-746, Republic of Korea
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