Identifying the Mechanism of Action of Valproic Acid on Phosphoinositide Signalling. / Kelly, Elizabeth.

2018. 274 p.

Research output: ThesisDoctoral Thesis

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@phdthesis{0c887dd08a514b0da78342b77e241199,
title = "Identifying the Mechanism of Action of Valproic Acid on Phosphoinositide Signalling",
abstract = "A third of epilepsy patients are resistant to currently available medication, highlighting a need to identify new antiepileptic drugs. To identify new drugs, researchers often explore new chemical structures with a common mechanism of action, but surprisingly the direct cellular target for many drugs remains unclear. One such drug is valproic acid (VPA), commonly used in the treatment of both epilepsy and bipolar disorder (BD). Previous research using the single celled amoeba Dictyostelium discoideum identified phosphoinositide recycling as a potential therapeutic mechanism for VPA and this has been validated in animal seizure models, however, the molecular target for this mechanism is unclear. To identify this target, research in this thesis initially focuses on assessing the role of several key enzymes involved in phosphoinositide signalling as potential VPA targets. Loss of these proteins did not confer resistance to VPA in this model, suggesting that VPA may function through targeting proteins in the phosphatidylinositol (PI) salvage pathway. In this pathway three key enzymes, cytidine-diphosphate-diacylglycerol synthase (CDS), cytidine-diphosphate- diacylglycerol-inositol-3-phosphatidyltransferase (CDIPT) and diacylglycerol kinase (DGK) were investigated, with phylogenetic analysis establishing evolutionary conservation. Attempts to ablate the single D. discoideum Cds (CdsA) and Cdipt encoding genes were unsuccessful, suggesting a vital role for these proteins. In contrast, overexpressing both proteins showed that cells with elevated expression of CDIPT, but not CDSA, were resistant to therapeutic VPA concentrations. Furthermore, deletion of the single D. discoideum DGK (DGKA) gene was successful, with the mutant resistant to VPA during both acute and chronic treatment, that was restored on reintroduction of DGKA. To investigate whether loss of DGKA is related to epilepsy and BD, a range of related compounds were investigated for an effect on cell development. These experiments suggest that in D. discoideum, DGKA may provide a common target for both epilepsy and BD treatments, supporting data provided from preclinical and clinical studies in both disorders. Together this work suggests that DGK may provide a new therapeutic target for the treatment of both epilepsy and BD.  ",
keywords = "Dictyostelium discoideum, Epilepsy, Bipolar Disorder, Valproic acid, Lithium, Valpromide, decanoic acid, Octanoic acid, 4-ethyloctanoic acid, 2-methylhexanoic acid, Phosphoinositol salvage pathway, Diacylglycerol, Diacylglycerol kinase, Cytidine-diphosphate-diacylglycerol-inositol-3-phosphatidyltransferase, Cytidine diphosphate-diacylglycerol synthase, Cytidine diphosphate-diacylglycerol, Phosphatidic acid, PHOSPHOLIPASE-C, phospholipids, phosphatidylinositol 4,5-bisphosphate, Phosphatidylinositol 3-Kinases, phosphatidylinositol 3,4,5-trisphosphate, phosphatase and tensin homolog, Phosphatidate phosphatase LPIN2, Elizabeth Kelly, Royal Holloway",
author = "Elizabeth Kelly",
year = "2018",
language = "English",
school = "Royal Holloway, University of London",

}

RIS

TY - THES

T1 - Identifying the Mechanism of Action of Valproic Acid on Phosphoinositide Signalling

AU - Kelly, Elizabeth

PY - 2018

Y1 - 2018

N2 - A third of epilepsy patients are resistant to currently available medication, highlighting a need to identify new antiepileptic drugs. To identify new drugs, researchers often explore new chemical structures with a common mechanism of action, but surprisingly the direct cellular target for many drugs remains unclear. One such drug is valproic acid (VPA), commonly used in the treatment of both epilepsy and bipolar disorder (BD). Previous research using the single celled amoeba Dictyostelium discoideum identified phosphoinositide recycling as a potential therapeutic mechanism for VPA and this has been validated in animal seizure models, however, the molecular target for this mechanism is unclear. To identify this target, research in this thesis initially focuses on assessing the role of several key enzymes involved in phosphoinositide signalling as potential VPA targets. Loss of these proteins did not confer resistance to VPA in this model, suggesting that VPA may function through targeting proteins in the phosphatidylinositol (PI) salvage pathway. In this pathway three key enzymes, cytidine-diphosphate-diacylglycerol synthase (CDS), cytidine-diphosphate- diacylglycerol-inositol-3-phosphatidyltransferase (CDIPT) and diacylglycerol kinase (DGK) were investigated, with phylogenetic analysis establishing evolutionary conservation. Attempts to ablate the single D. discoideum Cds (CdsA) and Cdipt encoding genes were unsuccessful, suggesting a vital role for these proteins. In contrast, overexpressing both proteins showed that cells with elevated expression of CDIPT, but not CDSA, were resistant to therapeutic VPA concentrations. Furthermore, deletion of the single D. discoideum DGK (DGKA) gene was successful, with the mutant resistant to VPA during both acute and chronic treatment, that was restored on reintroduction of DGKA. To investigate whether loss of DGKA is related to epilepsy and BD, a range of related compounds were investigated for an effect on cell development. These experiments suggest that in D. discoideum, DGKA may provide a common target for both epilepsy and BD treatments, supporting data provided from preclinical and clinical studies in both disorders. Together this work suggests that DGK may provide a new therapeutic target for the treatment of both epilepsy and BD.  

AB - A third of epilepsy patients are resistant to currently available medication, highlighting a need to identify new antiepileptic drugs. To identify new drugs, researchers often explore new chemical structures with a common mechanism of action, but surprisingly the direct cellular target for many drugs remains unclear. One such drug is valproic acid (VPA), commonly used in the treatment of both epilepsy and bipolar disorder (BD). Previous research using the single celled amoeba Dictyostelium discoideum identified phosphoinositide recycling as a potential therapeutic mechanism for VPA and this has been validated in animal seizure models, however, the molecular target for this mechanism is unclear. To identify this target, research in this thesis initially focuses on assessing the role of several key enzymes involved in phosphoinositide signalling as potential VPA targets. Loss of these proteins did not confer resistance to VPA in this model, suggesting that VPA may function through targeting proteins in the phosphatidylinositol (PI) salvage pathway. In this pathway three key enzymes, cytidine-diphosphate-diacylglycerol synthase (CDS), cytidine-diphosphate- diacylglycerol-inositol-3-phosphatidyltransferase (CDIPT) and diacylglycerol kinase (DGK) were investigated, with phylogenetic analysis establishing evolutionary conservation. Attempts to ablate the single D. discoideum Cds (CdsA) and Cdipt encoding genes were unsuccessful, suggesting a vital role for these proteins. In contrast, overexpressing both proteins showed that cells with elevated expression of CDIPT, but not CDSA, were resistant to therapeutic VPA concentrations. Furthermore, deletion of the single D. discoideum DGK (DGKA) gene was successful, with the mutant resistant to VPA during both acute and chronic treatment, that was restored on reintroduction of DGKA. To investigate whether loss of DGKA is related to epilepsy and BD, a range of related compounds were investigated for an effect on cell development. These experiments suggest that in D. discoideum, DGKA may provide a common target for both epilepsy and BD treatments, supporting data provided from preclinical and clinical studies in both disorders. Together this work suggests that DGK may provide a new therapeutic target for the treatment of both epilepsy and BD.  

KW - Dictyostelium discoideum

KW - Epilepsy

KW - Bipolar Disorder

KW - Valproic acid

KW - Lithium

KW - Valpromide

KW - decanoic acid

KW - Octanoic acid

KW - 4-ethyloctanoic acid

KW - 2-methylhexanoic acid

KW - Phosphoinositol salvage pathway

KW - Diacylglycerol

KW - Diacylglycerol kinase

KW - Cytidine-diphosphate-diacylglycerol-inositol-3-phosphatidyltransferase

KW - Cytidine diphosphate-diacylglycerol synthase

KW - Cytidine diphosphate-diacylglycerol

KW - Phosphatidic acid

KW - PHOSPHOLIPASE-C

KW - phospholipids

KW - phosphatidylinositol 4,5-bisphosphate

KW - Phosphatidylinositol 3-Kinases

KW - phosphatidylinositol 3,4,5-trisphosphate

KW - phosphatase and tensin homolog

KW - Phosphatidate phosphatase LPIN2

KW - Elizabeth Kelly

KW - Royal Holloway

M3 - Doctoral Thesis

ER -