Direct measurement of insulin is critical for basic and clinical studies of insulin secretion. Ho... more Direct measurement of insulin is critical for basic and clinical studies of insulin secretion. However, current methods are expensive and time-consuming. We developed an insulin assay based on homogenous time-resolved fluorescence that is significantly more rapid and cost-effective than current commonly used approaches. This assay was applied effectively to an insulin secreting cell line, INS-1E cells, as well as pancreatic islets, allowing us to validate the assay by elucidating mechanisms by which dopamine regulates insulin release. We found that dopamine functioned as a significant negative modulator of glucose-stimulated insulin secretion. Further, we showed that bromocriptine, a known dopamine D2/ D3 receptor agonist and newly approved drug used for treatment of type II diabetes mellitus, also decreased glucose-stimulated insulin secretion in islets to levels comparable to those caused by dopamine treatment.
Antipsychotic medications are associated with major metabolic changes that contribute to medical ... more Antipsychotic medications are associated with major metabolic changes that contribute to medical morbidity and a significantly shortened life span. The mechanisms for these changes provide us with a broader understanding of central nervous and peripheral organ-mediated metabolic regulation. This paper reviews an extensive literature regarding putative mechanisms for effects of antipsychotic medications on weight regulation and glucose homeostasis as well as potential inherent metabolic risks of schizophrenia itself. We present a model suggesting that peripheral antipsychotic targets play a critical role in drug-induced weight gain and diabetes. We propose that a better understanding of these mechanisms will be crucial to developing improved treatments for serious mental illnesses as well as providing potentially novel therapeutic targets of metabolic disorders including diabetes.
Advisor: Dennis Shields. Thesis (Ph. D.)--Sue Golding Graduate Division of Medical Sciences, Albe... more Advisor: Dennis Shields. Thesis (Ph. D.)--Sue Golding Graduate Division of Medical Sciences, Albert Einstein College of Medicine, Yeshiva University, 2003. Includes bibliographical references (leaves 157-178). Typescript.
Amphiphysin I is a 128 kD protein highly concentrated in nerve tenminals, where it has a putative... more Amphiphysin I is a 128 kD protein highly concentrated in nerve tenminals, where it has a putative role in endocytosis. It is a dominant autoantigen in patients with stiff-man syndrome associated with breast cancer, as well as in other paraneoplastic autoimmune neurological disorders. To elucidate the connection between amphiphysin I autoimmunity and cancer, we investigated its expression in breast cancer tissue. We report that amphiphysin I was expressed as two isoforms of 128 and 108 kD in the breast cancer of a patient with anti-amphiphysin I antibodies and paraneoplastic sensory neuronopathy. Amphiphysin I was also detectable at vari-able levels in several other human breast cancer tissues and cell lines and at low levels in normal mammary tissue and a variety of other non-neuronal tissues. The predominant amphiphysin I isoform expressed outside the brain in humans is the 108 kD isoform which represents an altematively spliced variant of neuronal amphiphysin I missing a 42 amino ...
Antipsychotic medications are associated with major metabolic changes that contribute to medical ... more Antipsychotic medications are associated with major metabolic changes that contribute to medical morbidity and a significantly shortened life span. The mechanisms for these changes provide us with a broader understanding of central nervous and peripheral organ-mediated metabolic regulation. This paper reviews an extensive literature regarding putative mechanisms for effects of antipsychotic medications on weight regulation and glucose homeostasis as well as potential inherent metabolic risks of schizophrenia itself. We present a model suggesting that peripheral antipsychotic targets play a critical role in drug-induced weight gain and diabetes. We propose that a better understanding of these mechanisms will be crucial to developing improved treatments for serious mental illnesses as well as providing potentially novel therapeutic targets of metabolic disorders including diabetes.
Biochemical and Biophysical Research Communications, 1993
ABSTRACT We have detected in human platelets two protein kinase C isozymes that have not been rep... more ABSTRACT We have detected in human platelets two protein kinase C isozymes that have not been reported previously. Using an anti-nPKCθ antibody and Western blotting, we calculated the molecular weight of platelet nPKCθ as 79K. This molecular weight is identical to that described for nPKCθ in skeletal muscle and in COS cells transfected with the nPKCθ-cDNA. Using an anti-nPKCη antibody, we determined the molecular weight of an immunoreactive protein, which we called nPKCη′, to be 95K. This molecular weight is higher than that of nPKCη found in lung and skin tissue of 82K and 78K, and it is higher than nPKCη of COS cells transfected with the nPKCη-cDNA expression plasmid.Together with previous reports, these findings make the total number of PKC isozymes in human platelets equal to six. These are the PKC isozymes: α, β, δ and ζ,which have been previously described, and η′ and θ which we describe here. To assess the functionality of these new PKC isoforms, we stimulated platelets with PAF. We found a 200% and 175% increase in the levels of membrane-bound nPKCη′ and nPKCθ, respectively, in human platelets stimulated by PAF. A concomitant decrease in the level of these isoforms in the cytoplasm was observed. This PAF-induced translocation was time-dependent, and it reached its peak after a 1 minute incubation of human platelets with PAF for nPKCθ and 30 seconds for nPKCη′.
Phospholipase D enzymes (PLDs) constitute a family of phosphodiesterases that catalyze the hydrol... more Phospholipase D enzymes (PLDs) constitute a family of phosphodiesterases that catalyze the hydrolysis of phosphatidylcholine (PtdCho) to generate choline and phosphatidic acid (PtdOH), a potent lipid signaling molecule implicated in numerous physiological processes. Mammalian PLDs have been localized to multiple organelles, including the nucleus, Golgi apparatus, lysosomes, secretory granules and plasma membrane. However, the detailed mechanisms that govern targeting of PLDs to different organelles, how their local activity is controlled or indeed the nature of PA effectors are not well understood. Here, we discuss recent observations on PLD localization to the Golgi apparatus and how members of this enzyme family might play a role in regulating the structure of this organelle.
Phospholipase D (PLD) hydrolyzes phosphatidylcholine to generate phosphatidic acid, a molecule kn... more Phospholipase D (PLD) hydrolyzes phosphatidylcholine to generate phosphatidic acid, a molecule known to have multiple physiological roles, including release of nascent secretory vesicles from the trans-Golgi network. In mammalian cells two forms of the enzyme, PLD1 and PLD2, have been described. We recently demonstrated that PLD1 is localized to the Golgi apparatus, nuclei, and to a lesser extent, plasma membrane. Due to its low abundance, the intracellular localization of PLD2 has been characterized only indirectly through overexpression of chimeric proteins. Using antibodies specific to PLD2, together with immunofluorescence microscopy, herein we demonstrate that a significant fraction of endogenous PLD2 localized to the perinuclear Golgi region and was also distributed throughout cells in dense cytoplasmic puncta; a fraction of which colocalized with caveolin-1 and the plasma membrane. On treatment with brefeldin A, PLD2 translocated into the nucleus in a manner similar to PLD1, ...
Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in use for sc... more Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in use for schizophrenia. While often effective at ameliorating psychosis, these drugs are largely ineffective at treating negative and cognitive symptoms. Increasing attention is being focused on the complex genetics of the illness and the signaling pathways implicated in its pathophysiology. We review targeted approaches for pharmacotherapy involving the glutamatergic, GABAergic and cholinergic pathways. We also describe several of the major genetic findings that identify signaling pathways representing potential targets for novel pharmacological intervention. These include genes in the 22q11 locus, DISC1, Neuregulin 1/ErbB4, and components of the Akt/GSK-3 pathway.
Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in clinical u... more Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in clinical use. Remarkably, the effector molecules through which these medications exert their actions remain poorly characterized. Increasing attention is being focused on Akt/glycogen synthase kinase-3 (GSK-3) and wingless (Wnt) signaling pathways, which have been associated with schizophrenia in a number of genetic and postmortem studies. Antipsychotic medications may treat symptoms of psychosis, at least in part, through modulation of levels and activity of Akt, GSK-3, and Wnt-related intracellular signaling. The authors review evidence that Akt/GSK-3 and Wnt-related pathways are involved in the pathogenesis of schizophrenia as well as details of intracellular events related to these molecules mediated by both typical and atypical antipsychotic medications. Further study of Akt/GSK-3 and Wnt signaling may ultimately lead to alternative therapeutics of schizophrenia-related disorders.
Direct measurement of insulin is critical for basic and clinical studies of insulin secretion. Ho... more Direct measurement of insulin is critical for basic and clinical studies of insulin secretion. However, current methods are expensive and time-consuming. We developed an insulin assay based on homogenous time-resolved fluorescence that is significantly more rapid and cost-effective than current commonly used approaches. This assay was applied effectively to an insulin secreting cell line, INS-1E cells, as well as pancreatic islets, allowing us to validate the assay by elucidating mechanisms by which dopamine regulates insulin release. We found that dopamine functioned as a significant negative modulator of glucose-stimulated insulin secretion. Further, we showed that bromocriptine, a known dopamine D2/ D3 receptor agonist and newly approved drug used for treatment of type II diabetes mellitus, also decreased glucose-stimulated insulin secretion in islets to levels comparable to those caused by dopamine treatment.
Antipsychotic medications are associated with major metabolic changes that contribute to medical ... more Antipsychotic medications are associated with major metabolic changes that contribute to medical morbidity and a significantly shortened life span. The mechanisms for these changes provide us with a broader understanding of central nervous and peripheral organ-mediated metabolic regulation. This paper reviews an extensive literature regarding putative mechanisms for effects of antipsychotic medications on weight regulation and glucose homeostasis as well as potential inherent metabolic risks of schizophrenia itself. We present a model suggesting that peripheral antipsychotic targets play a critical role in drug-induced weight gain and diabetes. We propose that a better understanding of these mechanisms will be crucial to developing improved treatments for serious mental illnesses as well as providing potentially novel therapeutic targets of metabolic disorders including diabetes.
Advisor: Dennis Shields. Thesis (Ph. D.)--Sue Golding Graduate Division of Medical Sciences, Albe... more Advisor: Dennis Shields. Thesis (Ph. D.)--Sue Golding Graduate Division of Medical Sciences, Albert Einstein College of Medicine, Yeshiva University, 2003. Includes bibliographical references (leaves 157-178). Typescript.
Amphiphysin I is a 128 kD protein highly concentrated in nerve tenminals, where it has a putative... more Amphiphysin I is a 128 kD protein highly concentrated in nerve tenminals, where it has a putative role in endocytosis. It is a dominant autoantigen in patients with stiff-man syndrome associated with breast cancer, as well as in other paraneoplastic autoimmune neurological disorders. To elucidate the connection between amphiphysin I autoimmunity and cancer, we investigated its expression in breast cancer tissue. We report that amphiphysin I was expressed as two isoforms of 128 and 108 kD in the breast cancer of a patient with anti-amphiphysin I antibodies and paraneoplastic sensory neuronopathy. Amphiphysin I was also detectable at vari-able levels in several other human breast cancer tissues and cell lines and at low levels in normal mammary tissue and a variety of other non-neuronal tissues. The predominant amphiphysin I isoform expressed outside the brain in humans is the 108 kD isoform which represents an altematively spliced variant of neuronal amphiphysin I missing a 42 amino ...
Antipsychotic medications are associated with major metabolic changes that contribute to medical ... more Antipsychotic medications are associated with major metabolic changes that contribute to medical morbidity and a significantly shortened life span. The mechanisms for these changes provide us with a broader understanding of central nervous and peripheral organ-mediated metabolic regulation. This paper reviews an extensive literature regarding putative mechanisms for effects of antipsychotic medications on weight regulation and glucose homeostasis as well as potential inherent metabolic risks of schizophrenia itself. We present a model suggesting that peripheral antipsychotic targets play a critical role in drug-induced weight gain and diabetes. We propose that a better understanding of these mechanisms will be crucial to developing improved treatments for serious mental illnesses as well as providing potentially novel therapeutic targets of metabolic disorders including diabetes.
Biochemical and Biophysical Research Communications, 1993
ABSTRACT We have detected in human platelets two protein kinase C isozymes that have not been rep... more ABSTRACT We have detected in human platelets two protein kinase C isozymes that have not been reported previously. Using an anti-nPKCθ antibody and Western blotting, we calculated the molecular weight of platelet nPKCθ as 79K. This molecular weight is identical to that described for nPKCθ in skeletal muscle and in COS cells transfected with the nPKCθ-cDNA. Using an anti-nPKCη antibody, we determined the molecular weight of an immunoreactive protein, which we called nPKCη′, to be 95K. This molecular weight is higher than that of nPKCη found in lung and skin tissue of 82K and 78K, and it is higher than nPKCη of COS cells transfected with the nPKCη-cDNA expression plasmid.Together with previous reports, these findings make the total number of PKC isozymes in human platelets equal to six. These are the PKC isozymes: α, β, δ and ζ,which have been previously described, and η′ and θ which we describe here. To assess the functionality of these new PKC isoforms, we stimulated platelets with PAF. We found a 200% and 175% increase in the levels of membrane-bound nPKCη′ and nPKCθ, respectively, in human platelets stimulated by PAF. A concomitant decrease in the level of these isoforms in the cytoplasm was observed. This PAF-induced translocation was time-dependent, and it reached its peak after a 1 minute incubation of human platelets with PAF for nPKCθ and 30 seconds for nPKCη′.
Phospholipase D enzymes (PLDs) constitute a family of phosphodiesterases that catalyze the hydrol... more Phospholipase D enzymes (PLDs) constitute a family of phosphodiesterases that catalyze the hydrolysis of phosphatidylcholine (PtdCho) to generate choline and phosphatidic acid (PtdOH), a potent lipid signaling molecule implicated in numerous physiological processes. Mammalian PLDs have been localized to multiple organelles, including the nucleus, Golgi apparatus, lysosomes, secretory granules and plasma membrane. However, the detailed mechanisms that govern targeting of PLDs to different organelles, how their local activity is controlled or indeed the nature of PA effectors are not well understood. Here, we discuss recent observations on PLD localization to the Golgi apparatus and how members of this enzyme family might play a role in regulating the structure of this organelle.
Phospholipase D (PLD) hydrolyzes phosphatidylcholine to generate phosphatidic acid, a molecule kn... more Phospholipase D (PLD) hydrolyzes phosphatidylcholine to generate phosphatidic acid, a molecule known to have multiple physiological roles, including release of nascent secretory vesicles from the trans-Golgi network. In mammalian cells two forms of the enzyme, PLD1 and PLD2, have been described. We recently demonstrated that PLD1 is localized to the Golgi apparatus, nuclei, and to a lesser extent, plasma membrane. Due to its low abundance, the intracellular localization of PLD2 has been characterized only indirectly through overexpression of chimeric proteins. Using antibodies specific to PLD2, together with immunofluorescence microscopy, herein we demonstrate that a significant fraction of endogenous PLD2 localized to the perinuclear Golgi region and was also distributed throughout cells in dense cytoplasmic puncta; a fraction of which colocalized with caveolin-1 and the plasma membrane. On treatment with brefeldin A, PLD2 translocated into the nucleus in a manner similar to PLD1, ...
Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in use for sc... more Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in use for schizophrenia. While often effective at ameliorating psychosis, these drugs are largely ineffective at treating negative and cognitive symptoms. Increasing attention is being focused on the complex genetics of the illness and the signaling pathways implicated in its pathophysiology. We review targeted approaches for pharmacotherapy involving the glutamatergic, GABAergic and cholinergic pathways. We also describe several of the major genetic findings that identify signaling pathways representing potential targets for novel pharmacological intervention. These include genes in the 22q11 locus, DISC1, Neuregulin 1/ErbB4, and components of the Akt/GSK-3 pathway.
Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in clinical u... more Dopamine D(2) receptor antagonism is a unifying property of all antipsychotic drugs in clinical use. Remarkably, the effector molecules through which these medications exert their actions remain poorly characterized. Increasing attention is being focused on Akt/glycogen synthase kinase-3 (GSK-3) and wingless (Wnt) signaling pathways, which have been associated with schizophrenia in a number of genetic and postmortem studies. Antipsychotic medications may treat symptoms of psychosis, at least in part, through modulation of levels and activity of Akt, GSK-3, and Wnt-related intracellular signaling. The authors review evidence that Akt/GSK-3 and Wnt-related pathways are involved in the pathogenesis of schizophrenia as well as details of intracellular events related to these molecules mediated by both typical and atypical antipsychotic medications. Further study of Akt/GSK-3 and Wnt signaling may ultimately lead to alternative therapeutics of schizophrenia-related disorders.
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Papers by Zachary Freyberg