Publications by authors named "Saleem Jahangeer"

20 Publications

  • Page 1 of 1

Low Rates of Permanent Pacing Are Observed Following Self-Expanding Transcatheter Aortic Valve Replacement Using an Annular Plane Projection for Deployment.

Circ Cardiovasc Interv 2021 Jan 12;14(1):e009258. Epub 2021 Jan 12.

Manchester Heart Centre, Manchester Royal Infirmary, Manchester University NHS Trust, United Kingdom (A.D.P., H.B.E.M., S.J., M.J.D., R.H., D.G.W.F.).

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http://dx.doi.org/10.1161/CIRCINTERVENTIONS.120.009258DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7813438PMC
January 2021

Aberrant subclavian: new face of an old disease.

J Vis Surg 2018 22;4:108. Epub 2018 May 22.

Department of Cardiac Surgery, Barts Heart Centre, St Bartholomew's Hospital, West Smithfield, London, UK.

An aneurysm of an aberrant subclavian artery is un usual prevalence of anomalies of aortic arch, with a literature reported prevalence of 2%. Timely elective intervention is of paramount. The advancement in stenting techniques has promoted this practice to be an alternative to conventional open surgical repair which is associated with high rates of perioperative complications including mortality outcomes. However, new faces of this old disease are emerging as we move to novelty and innovation era. We discuss in this review the advancements in this disease entity highlighting and collecting the world experiences.
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http://dx.doi.org/10.21037/jovs.2018.05.11DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5994462PMC
May 2018

Varying Evidence on Deep Hypothermic Circulatory Arrest in Thoracic Aortic Aneurysm Surgery.

Tex Heart Inst J 2018 04 7;45(2):70-75. Epub 2018 Apr 7.

Cardiovascular surgeons have long debated the safe duration of deep hypothermic circulatory arrest during thoracic aortic aneurysm surgery. The rationale for using adjunctive cerebral perfusion (or not) is to achieve the best technical aortic repair with the lowest risk of morbidity and death. In this literature review, we highlight the debates surrounding these issues, evaluate the disparate findings on deep hypothermic circulatory arrest durations and temperatures, and consider the usefulness of adjunctive perfusion.
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http://dx.doi.org/10.14503/THIJ-17-6364DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5940289PMC
April 2018

Successful Management of an Occult Cardiac Tamponade with Prompt Surgical Intervention and a Novel, Defined Pericardial Irrigation Protocol.

Thorac Cardiovasc Surg Rep 2015 Dec 31;4(1):28-30. Epub 2015 Mar 31.

Department of Cardiothoracic Surgery, Cork University Hospital, Cork, Ireland.

Purulent pericarditis is a rare entity in the postantibiotic era. It usually occurs in patients who have underlying chronic and immunosuppressing conditions and its presentation in the healthy adult population is quite rare. Infection of the pericardial space can occur via direct extension from infectious endocarditis, pneumonia, or empyema, or from a more distant source such as meningitis. Purulent pericarditis carries a very high mortality because of delay in the diagnosis and early occurrence of fatal complications. We describe a case of purulent pericarditis with impending cardiac tamponade in a previously healthy 40-year-old female patient, which was successfully treated with a combination of prompt surgical drainage and a novel irrigation protocol.
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http://dx.doi.org/10.1055/s-0035-1549302DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4670316PMC
December 2015

Surgical repair of an asymptomatic giant right coronary artery aneurysm.

Thorac Cardiovasc Surg Rep 2013 Dec 1;2(1):6-8. Epub 2013 Jul 1.

Department of Cardiothoracic Surgery, Cork University Hospital, Cork, Ireland.

Background Coronary artery aneurysm (CAA) is a rare finding, being mostly diagnosed on angiography or at autopsies. It is defined as being a dilation of the coronary artery that exceeds the diameter of the patient's largest coronary vessel by 1.5 to 2 times. Case Report We describe the operative correction of a giant right CAA measuring in excess of 10 cm. Conclusion Management of giant CAAs is not standardized and surgical strategy remains controversial. In our case, the patient has a successful surgical repair with no postoperative shunts on follow-up investigations.
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http://dx.doi.org/10.1055/s-0033-1348947DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4176070PMC
December 2013

Intravascular cell delivery device for therapeutic VEGF-induced angiogenesis in chronic vascular occlusion.

Biomaterials 2014 Oct 2;35(32):9012-22. Epub 2014 Aug 2.

Centre for Research in Vascular Biology (CRVB), Biosciences Institute, University College Cork, Cork, Ireland; Division of Cardiovascular Diseases, Molecular Medicine Program, Mayo Clinic, Rochester, MN, USA. Electronic address:

Site specific targeting remains elusive for gene and stem cell therapies in the cardiovascular field. One promising option involves use of devices that deliver larger and more sustained cell/gene payloads to specific disease sites using the versatility of percutaneous vascular access technology. Smooth muscle cells (SMCs) engineered to deliver high local concentrations of an angiogenic molecule (VEGF) were placed in an intravascular cell delivery device (ICDD) in a porcine model of chronic total occlusion (CTO) involving ameroid placement on the proximal left circumflex (LCx) artery. Implanted SMC were retained within the ICDD and were competent for VEGF production in vitro and in vivo. Following implantation, micro-CT analyses revealed that ICDD-VEGF significantly enhanced vasa vasora microvessel density with a concomitant increase in tissue VEGF protein levels and formation of endothelial cell colonies suggesting increased angiogenic potential. ICDD-VEGF markedly enhanced regional blood flow determined by microsphere and contrast CT analysis translating to a functional improvement in regional wall motion and global left ventricular (LV) systolic and diastolic function. Our data indicate robust, clinically relevant angiogenesis can be achieved in a human scale porcine chronic vascular occlusion model following ICDD-VEGF-based delivery of angiogenic cells. This may have implications for percutaneous delivery of numerous therapeutic factors promoting creation of microvascular bypass networks in chronic vaso-occlusive diseases.
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http://dx.doi.org/10.1016/j.biomaterials.2014.07.016DOI Listing
October 2014

Releasing pressure in tumors: what do we know so far and where do we go from here? A review.

Cancer Res 2014 May 28;74(10):2655-62. Epub 2014 Apr 28.

Authors' Affiliations: Cork Cancer Research Centre, Leslie C Quick Laboratory, BioSciences Institute, University College Cork; and Department of Cardiothoracic Surgery, Cork University Hospital, Wilton, Cork, Ireland

Tumor interstitial pressure is a fundamental feature of cancer biology. Elevation in tumor pressure affects the efficacy of cancer treatment. It causes heterogenous intratumoral distribution of drugs and macromolecules. It also causes the development of hypoxia within tumor bulk, leading to reduced efficacy of therapeutic drugs and radiotherapy. Tumor pressure has been associated with increased metastatic potential and poor prognosis in some tumors. The formation of increased pressure in solid tumors is multifactorial. Factors known to affect tumor pressure include hyperpermeable tortuous tumor vasculatures, the lack of functional intratumoral lymphatic vessels, abnormal tumor microenvironment, and the solid stress exerted by proliferating tumor cells. Reducing this pressure is known to enhance the uptake and homogenous distribution of many therapies. Pharmacologic and biologic agents have been shown to reduce tumor pressure. These include antiangiogenic therapy, vasodilatory agents, antilymphogenic therapy, and proteolytic enzymes. Physical manipulation has been shown to cause reduction in tumor pressure. These include irradiation, hyperbaric oxygen therapy, hyper- or hypothermic therapy, and photodynamic therapy. This review explores the methods to reduce tumor pressure that may open up new avenues in cancer treatment.
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http://dx.doi.org/10.1158/0008-5472.CAN-13-3696DOI Listing
May 2014

Review of current thermal ablation treatment for lung cancer and the potential of electrochemotherapy as a means for treatment of lung tumours.

Cancer Treat Rev 2013 Dec 17;39(8):862-71. Epub 2013 Apr 17.

Department of Cardiothoracic Surgery, Cork University Hospital, Wilton, Cork, Ireland; Cork Cancer Research Centre, Bioscience Institute, University College Cork, Cork, Ireland. Electronic address:

Lung cancer remains the most common cancer diagnosed worldwide and has one of the lowest survival rates of all cancers. Surgery remains the only curative treatment option but because most patients are either diagnosed at advanced stages or are unfit for surgery, less than a third of all lung cancer patients will undergo a surgical resection. Thermal ablation has emerged as an alternative option in patients who are unfit to undergo surgery. Thermal ablative therapies used in clinical practice to date include Radiofrequency Ablation (RFA), Microwave Ablation (MWA) and Cryoablation This article will focus on the advantages and limitations of thermal ablative therapy and investigates the potential of a relatively new treatment modality, Electrochemotherapy (ECT), as a novel treatment for lung cancer.
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http://dx.doi.org/10.1016/j.ctrv.2013.03.007DOI Listing
December 2013

Sphingosine kinase 1 regulates mucin production via ERK phosphorylation.

Pulm Pharmacol Ther 2010 Feb 14;23(1):36-42. Epub 2009 Oct 14.

The Division of Respiratory Medicine, Department of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1 Kusunoki-cho, Chuo-ku, Kobe 650-0017, Japan.

Our previous report showed that inhibition of sphingosine kinase (SphK) ameliorates eosinophilic inflammation and mucin production in a mouse asthmatic model. To clarify the role of SphK in airway mucin production, we utilized the mouse asthmatic model and found that both SphK and MUC5AC expression were increased and co-localized in airway epithelium. Next we cultured normal human bronchial epithelial cells in an air-liquid interface and treated with IL-13 to induce their differentiation into goblet cells. We found that SphK1 and MUC5AC expression was increased by IL-13 treatment at both protein and mRNA levels, whereas SphK2 expression was not changed. N,N-dimethylsphingosine (DMS), a potent SphK inhibitor, decreased MUC5AC expression up-regulated by IL-13 treatment. Furthermore, DMS inhibited IL-13-induced ERK1/2 phosphorylation but neither p38 MAPK nor STAT6 phosphorylation. These results suggest that SphK1 is involved in MUC5AC production induced by IL-13 upstream of ERK1/2 phosphorylation, and independent of STAT6 phosphorylation.
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http://dx.doi.org/10.1016/j.pupt.2009.10.005DOI Listing
February 2010

Roles of extracellular and intracellular sphingosine 1-phosphate in cell migration.

Genes Cells 2009 May 15;14(5):597-605. Epub 2009 Apr 15.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.

Sphingosine 1-phosphate (S1P) is an important factor for the regulation of cell motility acting both inside and outside the cells. The precise role of S1P in the control of cell motility, however, remains unclear. Here we describe the roles of S1P in the regulation of cell motility by dissecting them into intracellular and extracellular actions using a liposomal S1P transfer technique. In a Boyden chamber assay free S1P enhanced directional cell movement, whereas liposomal S1P induced nondirectional cell movement. Furthermore, inhibition of sphingosine kinase (SphK) 1 by several inhibitors or knockdown of the enzyme expression by siRNA caused reduced wound-faced cell polarity formation as assessed by wound-healing assay. Moreover, S1P-induced cell migration was strongly inhibited by SphK inhibitors. These results indicate that extracellular S1P acting through S1P receptors facilitates the formation of cell polarity, whereas S1P generated inside the cells functions as an intracellular mediator per se to enhance nondirectional cell movement, thus S1P enhances directional cell movement in a coordinated fashion.
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http://dx.doi.org/10.1111/j.1365-2443.2009.01295.xDOI Listing
May 2009

CtBP1/BARS is an activator of phospholipase D1 necessary for agonist-induced macropinocytosis.

EMBO J 2009 May 26;28(9):1197-207. Epub 2009 Mar 26.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe, Japan.

Vesicular trafficking such as macropinocytosis is a dynamic process that requires coordinated interactions between specialized proteins and lipids. A recent report suggests the involvement of CtBP1/BARS in epidermal growth factor (EGF)-induced macropinocytosis. Detailed mechanisms as to how lipid remodelling is regulated during macropinocytosis are still undefined. Here, we show that CtBP1/BARS is a physiological activator of PLD1 required in agonist-induced macropinocytosis. EGF-induced macropinocytosis was specifically blocked by 1-butanol but not by 2-butanol. In addition, stimulation of cells by serum or EGF resulted in the association of CtBP1/BARS with PLD1. Finally, CtBP1/BARS activated PLD1 in a synergistic manner with other PLD activators, including ADP-ribosylation factors as demonstrated by in vitro and intact cell systems. The present results shed light on the molecular basis of how the 'fission protein' CtBP1/BARS controls vesicular trafficking events including macropinocytosis.
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http://dx.doi.org/10.1038/emboj.2009.78DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2664659PMC
May 2009

Sphingosine kinase/sphingosine 1-phosphate signalling in central nervous system.

Cell Signal 2009 Jan 22;21(1):7-13. Epub 2008 Jul 22.

Division of Biochemistry, Department of Biochemistry/Molecular Biology, Kobe University Graduate School of Medicine, Kobe, 650-0017, Japan.

Sphingolipids were once regarded as inert structural components of cell membranes. Now these metabolites are generally believed to be important bioactive molecules that control a wide repertoire of cellular processes such as proliferation and survival of cells. Along with these ubiquitous cell functions observed in many peripheral tissues sphingolipid metabolites, especially sphingosine 1-phosphate, exert important neuron-specific functions such as regulation of neurotransmitter release. This review summarizes physiological and pathological roles of sphingolipid metabolites emphasizing the role of sphingosine 1-phosphate in the central nervous system.
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http://dx.doi.org/10.1016/j.cellsig.2008.07.011DOI Listing
January 2009

Inhalation of sphingosine kinase inhibitor attenuates airway inflammation in asthmatic mouse model.

Am J Physiol Lung Cell Mol Physiol 2008 Jun 21;294(6):L1085-93. Epub 2008 Mar 21.

Division of Respiratory Medicine, Deptartment of Internal Medicine, Kobe University Graduate School of Medicine, 7-5-1, Kusunoki-cho, Chuo-ku, Kobe, 650-0017, Japan.

Sphingosine 1-phosphate (S1P) produced by sphingosine kinase (SPHK) is implicated in acute immunoresponses, however, mechanisms of SPHK/S1P signaling in the pathogenesis of bronchial asthma are poorly understood. In this study, we hypothesized that SPHK inhibition could ameliorate lung inflammation in ovalbumin (OVA)-challenged mouse lungs. Six- to eight-week-old C57BL/6J mice were sensitized and exposed to OVA for 3 consecutive days. Twenty-four hours later, mice lungs and bronchoalveolar lavage (BAL) fluid were analyzed. For an inhibitory effect, either of the two different SPHK inhibitors, N,N-dimethylsphingosine (DMS) or SPHK inhibitor [SK-I; 2-(p-hydroxyanilino)-4-(p-chlorophenyl) thiazole], was nebulized for 30 min before OVA inhalation. OVA inhalation caused S1P release into BAL fluid and high expression of SPHK1 around bronchial epithelial walls and inflammatory areas. DMS or SK-I inhalation resulted in a decrease in S1P amounts in BAL fluid to basal levels, accompanied by decreased eosinophil infiltration and peroxidase activity. The extent of inhibition caused by DMS inhalation was higher than that caused by SK-I. Like T helper 2 (Th2) cytokine release, OVA inhalation-induced increase in eotaxin expression was significantly suppressed by DMS pretreatment both at protein level in BAL fluid and at mRNA level in lung homogenates. Moreover, bronchial hyperresponsiveness to inhaled methacholine and goblet cell hyperplasia were improved by SPHK inhibitors. These data suggest that the inhibition of SPHK affected acute eosinophilic inflammation induced in antigen-challenged mouse model and that targeting SPHK may provide a novel therapeutic tool to treat bronchial asthma.
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http://dx.doi.org/10.1152/ajplung.00445.2007DOI Listing
June 2008

Requirement of phospholipase D for ilimaquinone-induced Golgi membrane fragmentation.

J Biol Chem 2007 Nov 26;282(47):34085-92. Epub 2007 Sep 26.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe, Japan.

Although organelles such as the endoplasmic reticulum and Golgi apparatus are highly compartmentalized, these organelles are interconnected through a network of vesicular trafficking. The marine sponge metabolite ilimaquinone (IQ) is known to induce Golgi membrane fragmentation and is widely used to study the mechanism of vesicular trafficking. Although IQ treatment causes protein kinase D (PKD) activation, the detailed mechanism of IQ-induced Golgi membrane fragmentation remains unclear. In this work, we found that IQ treatment of cells caused a robust activation of phospholipase D (PLD). In the presence of 1-butanol but not 2-butanol, IQ-induced Golgi membrane fragmentation was completely blocked. In addition, IQ failed to induce Golgi membrane fragmentation in PLD knock-out DT40 cells. Furthermore, IQ-induced PKD activation was completely blocked by treatment with either 1-butanol or propranolol. Notably, IQ-induced Golgi membrane fragmentation was also blocked by propranolol treatment. These results indicate that PLD-catalyzed formation of phosphatidic acid is a prerequisite for IQ-induced Golgi membrane fragmentation and that enzymatic conversion of phosphatidic acid to diacylglycerol is necessary for subsequent activation of PKD and IQ-induced Golgi membrane fragmentation.
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http://dx.doi.org/10.1074/jbc.M705593200DOI Listing
November 2007

Protein kinase D-mediated phosphorylation and nuclear export of sphingosine kinase 2.

J Biol Chem 2007 Sep 16;282(37):27493-27502. Epub 2007 Jul 16.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kusunoki-cho 7-5-1, Chuo-ku, Kobe 650-0017, Japan. Electronic address:

Sphingosine kinase (SPHK) is a key enzyme producing important messenger sphingosine 1-phosphate and is implicated in cell proliferation and suppression of apoptosis. Because the extent of agonist-induced activation of SPHK is modest, signaling via SPHK may be regulated through its localization at specific intracellular sites. Although the SPHK1 isoform has been extensively studied and characterized, the regulation of expression and function of the other isoform, SPHK2, remain largely unexplored. Here we describe an important post-translational modification, namely, phosphorylation of SPHK2 catalyzed by protein kinase D (PKD), which regulates its localization. Upon stimulation of HeLa cells by tumor promoter phorbol 12-myristate 13-acetate, a serine residue in a novel and putative nuclear export signal, identified for the first time, in SPHK2 was phosphorylated followed by SPHK2 export from the nucleus. Constitutively active PKD phosphorylated this serine residue in the nuclear export signal both in vivo and in vitro. Moreover, down-regulation of PKDs through RNA interference resulted in the attenuation of both basal and phorbol 12-myristate 13-acetate-induced phosphorylation, which was followed by the accumulation of SPHK2 in the nucleus in a manner rescued by PKD over-expression. These results indicate that PKD is a physiologically relevant enzyme for SPHK2 phosphorylation, which leads to its nuclear export for subsequent cellular signaling.
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http://dx.doi.org/10.1074/jbc.M701641200DOI Listing
September 2007

Involvement of sphingosine-1-phosphate in glutamate secretion in hippocampal neurons.

Mol Cell Biol 2007 May 26;27(9):3429-40. Epub 2007 Feb 26.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.

Neuronal activity greatly influences the formation and stabilization of synapses. Although receptors for sphingosine-1-phosphate (S1P), a lipid mediator regulating diverse cellular processes, are abundant in the central nervous system, neuron-specific functions of S1P remain largely undefined. Here, we report two novel actions of S1P using primary hippocampal neurons as a model system: (i) as a secretagogue where S1P triggers glutamate secretion and (ii) as an enhancer where S1P potentiates depolarization-evoked glutamate secretion. Sphingosine kinase 1 (SK1), a key enzyme for S1P production, was enriched in functional puncta of hippocampal neurons. Silencing SK1 expression by small interfering RNA as well as SK1 inhibition by dimethylsphingosine resulted in a strong inhibition of depolarization-evoked glutamate secretion. Fluorescence recovery after photobleaching analysis showed translocation of SK1 from cytosol to membranes at the puncta during depolarization, which resulted in subsequent accumulation of S1P within cells. Fluorescent resonance energy transfer analysis demonstrated that the S1P(1) receptor at the puncta was activated during depolarization and that depolarization-induced S1P(1) receptor activation was inhibited in SK1-knock-down cells. Importantly, exogenously added S1P at a nanomolar concentration by itself elicited glutamate secretion from hippocampal cells even when the Na(+)-channel was blocked by tetrodotoxin, suggesting that S1P acts on presynaptic membranes. Furthermore, exogenous S1P at a picomolar level potentiated depolarization-evoked secretion in the neurons. These findings indicate that S1P, through its autocrine action, facilitates glutamate secretion in hippocampal neurons both by secretagogue and enhancer actions and may be involved in mechanisms underlying regulation of synaptic transmission.
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http://dx.doi.org/10.1128/MCB.01465-06DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1899953PMC
May 2007

Involvement of N-terminal-extended form of sphingosine kinase 2 in serum-dependent regulation of cell proliferation and apoptosis.

J Biol Chem 2005 Oct 15;280(43):36318-25. Epub 2005 Aug 15.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.

Sphingosine kinase (SPHK) 1 is implicated in the regulation of cell proliferation and anti-apoptotic processes by catalyzing the formation of an important bioactive messenger, sphingosine 1-phosphate. Unlike the proliferative action of SPHK1, another isozyme, SPHK2, has been shown to possess anti-proliferative or pro-apoptotic action. Molecular mechanisms of SPHK2 action, however, are largely unknown. The present studies were undertaken to characterize the N-terminal-extended form of SPHK2 (SPHK2-L) by comparing it with the originally reported form, SPHK2-S. Real-time quantitative PCR analysis revealed that SPHK2-L mRNA is the major form in several human cell lines and tissues. From sequence analyses it was concluded that SPHK2-L is a species-specific isoform that is expressed in human but not in mouse. At the protein level it has been demonstrated by immunoprecipitation studies that SPHK2-L is the major isoform in human hepatoma HepG2 cells. SPHK2-L, when expressed in human embryonic kidney (HEK) 293 cells, did not show any inhibition of DNA synthesis in the presence of serum, whereas it showed marked inhibition in the absence of serum. Moreover, serum deprivation resulted in the translocation of SPHK2-L into the nuclei. In addition, serum deprivation induced SPHK2-L expression in HEK293 cells. Furthermore, suppression of SPHK2 by small interfering RNA treatment prevented serum deprivation- or drug-induced apoptosis in HEK293 cells. Taken together, these results indicate that a major form of SPHK2 splice variant, SPHK2-L, in human cells does not inhibit DNA synthesis under normal conditions and that SPHK2-L accumulation in the nucleus induced by serum deprivation may be involved in the cessation of cell proliferation or apoptosis depending on the cell type.
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http://dx.doi.org/10.1074/jbc.M504507200DOI Listing
October 2005

Delta-catenin/NPRAP (neural plakophilin-related armadillo repeat protein) interacts with and activates sphingosine kinase 1.

Biochem J 2004 Sep;382(Pt 2):717-23

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.

Sphingosine kinase (SPHK) is a key enzyme catalysing the formation of sphingosine 1-phosphate (SPP), a lipid messenger that is implicated in the regulation of a wide variety of important cellular events acting through intracellular, as well as extracellular, mechanisms. However, the molecular mechanism of intracellular actions of SPP remains unclear. Here, we have identified delta-catenin/NPRAP (neural plakophilin-related armadillo repeat protein) as a potential binding partner for SPHK1 by yeast two-hybrid screening. From co-immunoprecipitation analyses, the C-terminal portion of delta-catenin/NPRAP containing the seventh to tenth armadillo repeats was found to be required for interaction with SPHK1. Endogenous delta-catenin/NPRAP was co-localized with endogenous SPHK1 and transfected delta-catenin/NPRAP was co-localized with transfected SPHK1 in dissociated rat hippocampal neurons. MDCK (Madin-Darby canine kidney) cells stably expressing delta-catenin/NPRAP contained elevated levels of intracellular SPP. In a purified system delta-catenin/NPRAP stimulated SPHK1 in a dose-dependent manner. Furthermore, delta-catenin/NPRAP-induced increased cell motility in MDCK cells was completely inhibited by dimethylsphingosine, a specific inhibitor of SPHK1. These results strongly suggest that at least some of delta-catenin/NPRAP functions, including increased cell motility, are mediated by an SPHK-SPP signalling pathway.
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http://dx.doi.org/10.1042/BJ20040141DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1133830PMC
September 2004

Sphingosine kinase 2 is a nuclear protein and inhibits DNA synthesis.

J Biol Chem 2003 Nov 2;278(47):46832-9. Epub 2003 Sep 2.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.

Sphingosine kinase-1 (SPHK1) is a key enzyme catalyzing the formation of an important bioactive lipid messenger, sphingosine 1-phosphate, and is implicated in the regulation of cell proliferation and antiapoptotic processes. Biological features of another isozyme SPHK2, however, remain unclear. The present studies were undertaken to characterize SPHK2 by comparison with SPHK1. When SPHK2 was transiently expressed in various cell lines, it was localized in the nuclei as well as in the cytosol, whereas SPHK1 was distributed in the cytosol but not in the nucleus. We have mapped a functional nuclear localization signal (NLS) to the N-terminal region of SPHK2. We have observed that the expression of SPHK2 in various cell types causes inhibition of DNA synthesis, resulting in the cell cycle arrest at G1/S phase. We have also demonstrated that an NLS mutant of SPHK2, SPHK2R93E/R94E, failed to enter the nucleus and to inhibit DNA synthesis. Moreover, a fusion protein, NLS-SPHK1, where SPHK1 was fused to the NLS sequence of SPHK2 acquired the ability to enter nuclei and inhibited DNA synthesis. These results indicate that SPHK2 localizes in the nuclei and causes inhibition of DNA synthesis, and this may affect subsequent cellular events.
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http://dx.doi.org/10.1074/jbc.M306577200DOI Listing
November 2003

Identification and characterization of RPK118, a novel sphingosine kinase-1-binding protein.

J Biol Chem 2002 Sep 20;277(36):33319-24. Epub 2002 Jun 20.

Division of Biochemistry, Department of Molecular and Cellular Biology, Kobe University Graduate School of Medicine, Kobe 650-0017, Japan.

Sphingosine kinase (SPHK) is a key enzyme catalyzing the formation of sphingosine 1 phosphate (SPP), a lipid messenger that is implicated in the regulation of a wide variety of important cellular events through intracellular as well as extracellular mechanisms. However, the molecular mechanism of the intracellular actions of SPP remains unclear. Here we have cloned a novel sphingosine kinase-1 (SPHK1)-binding protein, RPK118, by yeast two-hybrid screening. RPK118 contains several functional domains whose sequences are homologous to other known proteins including the phox homology domain and pseudokinase 1 and 2 domains and is shown to be a member of an evolutionarily highly conserved gene family. The pseudokinase 2 domain of RPK118 is responsible for SPHK1 binding as judged by yeast two-hybrid screening and immunoprecipitation studies. RPK118 is also shown to co-localize with SPHK1 on early endosomes in COS7 cells expressing both recombinant proteins. Furthermore, RPK118 specifically binds to phosphatidylinositol 3-phosphate. These results strongly suggest that RPK118 is a novel SPHK1-binding protein that may be involved in transmitting SPP-mediated signaling into the cell.
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http://dx.doi.org/10.1074/jbc.M201442200DOI Listing
September 2002