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Research paper thumbnail of Faculty Opinions recommendation of ERK8 is a negative regulator of O-GalNAc glycosylation and cell migration

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature, Apr 1, 2014

ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This... more ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This process markedly stimulates cell migration and is constitutively activated in more than 60% of breast carcinomas. How this activation is achieved remains unclear. Here, we screened 948 signalling genes using RNAi and imaging. We identified 12 negative regulators of O-glycosylation that all control GalNAc-T sub-cellular localisation. ERK8, an atypical MAPK with high basal kinase activity, is a strong hit and is partially localised at the Golgi. Its inhibition induces the relocation of GalNAc-Ts, but not of KDEL receptors, revealing the existence of two separate COPI-dependent pathways. ERK8 down-regulation, in turn, activates cell motility. In human breast and lung carcinomas, ERK8 expression is reduced while ER O-glycosylation initiation is hyperactivated. In sum, ERK8 appears as a constitutive brake on GalNAc-T relocalisation, and the loss of its expression could drive cancer aggressivity through increased cell motility.

Research paper thumbnail of Cytosolic Ca2+ Modulates Golgi Structure Through PKCα-Mediated GRASP55 Phosphorylation

iScience, Mar 1, 2020

It has been well documented that the ER responds to cellular stresses through the unfolded protei... more It has been well documented that the ER responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tm), and dithiothreitol (DTT), and found that only TG treatment resulted in Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, indicating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevating intracellular Ca 2+ and protein kinase Ca (PKCa) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCa with other activating or inflammatory agents, including phorbol 12-myristate 13-acetate and histamine, modulates Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca 2+ modulates Golgi structure and function.

Research paper thumbnail of Cytosolic Ca2+modulates Golgi structure through PKC-mediated GRASP55 phosphorylation

bioRxiv (Cold Spring Harbor Laboratory), Sep 26, 2019

It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses thr... more It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tu) and Dithiothreitol (DTT), and found that only TG treatment caused Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, demonstrating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevated intracellular Ca 2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including Phorbol 12-myristate 13-acetate (PMA) and histamine, modulates the Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca 2+ modulates Golgi structure and function.

Research paper thumbnail of The Unfolded Protein Response Regulates Uterine Myocyte Anti-Oxidant Responsiveness During Pregnancy 1 Running Title : EIF 2 AK 3 Controls Uterine Myocyte Oxidative Stress

There is considerable evidence that implicates oxidative stress in the pathophysiology of human p... more There is considerable evidence that implicates oxidative stress in the pathophysiology of human pregnancy complications. However the role and the mechanism of maintaining an anti-oxidant pro-survival uterine environment during normal pregnancy is largely unresolved. Herein we report the highly active uterine unfolded protein response plays a key role in promoting anti-oxidant activity in the uterine myocyte across gestation. The unfolded protein response senses the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and activates a signaling network that consists of the transmembrane protein kinase eukaryotic translation initiation factor 2 alpha kinase 3/PKR-like-ER kinase (EIF2AK3), which acts to decrease protein translation levels allowing for a lowered need for protein folding during periods of ER stress. However independent of its translational regulatory capacity, EIF2AK3 dependent signals elicit the activation of the transcription factor, nuclear factor, eryt...

Research paper thumbnail of Cytosolic Ca2+ Modulates Golgi Structure Through PKCα-Mediated GRASP55 Phosphorylation

iScience, 2020

Summary It has been well documented that the ER responds to cellular stresses through the unfolde... more Summary It has been well documented that the ER responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tm), and dithiothreitol (DTT), and found that only TG treatment resulted in Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, indicating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevating intracellular Ca2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including phorbol 12-myristate 13-acetate and histamine, modulates Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosoli...

Research paper thumbnail of Faculty of 1000 evaluation for ERK8 is a negative regulator of O-GalNAc glycosylation and cell migration

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature, Apr 1, 2014

ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This... more ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This process markedly stimulates cell migration and is constitutively activated in more than 60% of breast carcinomas. How this activation is achieved remains unclear. Here, we screened 948 signalling genes using RNAi and imaging. We identified 12 negative regulators of O-glycosylation that all control GalNAc-T sub-cellular localisation. ERK8, an atypical MAPK with high basal kinase activity, is a strong hit and is partially localised at the Golgi. Its inhibition induces the relocation of GalNAc-Ts, but not of KDEL receptors, revealing the existence of two separate COPI-dependent pathways. ERK8 down-regulation, in turn, activates cell motility. In human breast and lung carcinomas, ERK8 expression is reduced while ER O-glycosylation initiation is hyperactivated. In sum, ERK8 appears as a constitutive brake on GalNAc-T relocalisation, and the loss of its expression could drive cancer aggressivity through increased cell motility.

Research paper thumbnail of Nuclear receptor control of opposing macrophage phenotypes in cardiovascular disease

Frontiers in Bioscience, 2012

Introduction 3. Nuclear receptor control of macrophage activation 3.1. Regulation of macrophage a... more Introduction 3. Nuclear receptor control of macrophage activation 3.1. Regulation of macrophage activation by PPARs 3.2. Mineralocorticoid receptor activates proinflammatory macrophage function 3.3. Interaction of nuclear receptors and cytokines 4. Alternatively activated macrophage phenotypes in cardiovascular disease 4.1. Cardiac inflammation, hypertrophy and fibrosis 4.2. Atherosclerosis 4.3. Stroke 5. Heme oxygenase-1 in alternatively activated macrophages 5.1. Atherosclerosis 5.2. Alveolar macrophages and pulmonary hypertension 6. Strategies to study macrophage polarization in disease 7. Summary and perspectives 8. Acknowledgements 9. References

Research paper thumbnail of Cytosolic Ca2+ modulates Golgi structure through PKC-mediated GRASP55 phosphorylation

It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses thr... more It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tu) and Dithiothreitol (DTT), and found that only TG treatment caused Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, demonstrating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevated intracellular Ca 2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including Phorbol 12-myristate 13-acetate (PMA) and histamine, modulates the Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca 2+ modulates Golgi structure and function.

Research paper thumbnail of The Unfolded Protein Response Regulates Uterine Myocyte Antioxidant Responsiveness During Pregnancy

Biology of reproduction, 2016

There is considerable evidence that implicates oxidative stress in the pathophysiology of human p... more There is considerable evidence that implicates oxidative stress in the pathophysiology of human pregnancy complications. However, the role and the mechanism of maintaining an antioxidant prosurvival uterine environment during normal pregnancy is largely unresolved. Herein we report that the highly active uterine unfolded protein response plays a key role in promoting antioxidant activity in the uterine myocyte across gestation. The unfolded protein response (UPR) senses the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and activates a signaling network that consists of the transmembrane protein kinase eukaryotic translation initiation factor 2 alpha kinase 3/PKR-like-ER kinase (EIF2AK3), which acts to decrease protein translation levels, allowing for a lowered need for protein folding during periods of ER stress. However, independent of its translational regulatory capacity, EIF2AK3-dependent signals elicit the activation of the transcription factor, nuclear f...

Research paper thumbnail of Faculty Opinions recommendation of ERK8 is a negative regulator of O-GalNAc glycosylation and cell migration

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature, Apr 1, 2014

ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This... more ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This process markedly stimulates cell migration and is constitutively activated in more than 60% of breast carcinomas. How this activation is achieved remains unclear. Here, we screened 948 signalling genes using RNAi and imaging. We identified 12 negative regulators of O-glycosylation that all control GalNAc-T sub-cellular localisation. ERK8, an atypical MAPK with high basal kinase activity, is a strong hit and is partially localised at the Golgi. Its inhibition induces the relocation of GalNAc-Ts, but not of KDEL receptors, revealing the existence of two separate COPI-dependent pathways. ERK8 down-regulation, in turn, activates cell motility. In human breast and lung carcinomas, ERK8 expression is reduced while ER O-glycosylation initiation is hyperactivated. In sum, ERK8 appears as a constitutive brake on GalNAc-T relocalisation, and the loss of its expression could drive cancer aggressivity through increased cell motility.

Research paper thumbnail of Cytosolic Ca2+ Modulates Golgi Structure Through PKCα-Mediated GRASP55 Phosphorylation

iScience, Mar 1, 2020

It has been well documented that the ER responds to cellular stresses through the unfolded protei... more It has been well documented that the ER responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tm), and dithiothreitol (DTT), and found that only TG treatment resulted in Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, indicating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevating intracellular Ca 2+ and protein kinase Ca (PKCa) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCa with other activating or inflammatory agents, including phorbol 12-myristate 13-acetate and histamine, modulates Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca 2+ modulates Golgi structure and function.

Research paper thumbnail of Cytosolic Ca2+modulates Golgi structure through PKC-mediated GRASP55 phosphorylation

bioRxiv (Cold Spring Harbor Laboratory), Sep 26, 2019

It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses thr... more It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tu) and Dithiothreitol (DTT), and found that only TG treatment caused Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, demonstrating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevated intracellular Ca 2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including Phorbol 12-myristate 13-acetate (PMA) and histamine, modulates the Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca 2+ modulates Golgi structure and function.

Research paper thumbnail of The Unfolded Protein Response Regulates Uterine Myocyte Anti-Oxidant Responsiveness During Pregnancy 1 Running Title : EIF 2 AK 3 Controls Uterine Myocyte Oxidative Stress

There is considerable evidence that implicates oxidative stress in the pathophysiology of human p... more There is considerable evidence that implicates oxidative stress in the pathophysiology of human pregnancy complications. However the role and the mechanism of maintaining an anti-oxidant pro-survival uterine environment during normal pregnancy is largely unresolved. Herein we report the highly active uterine unfolded protein response plays a key role in promoting anti-oxidant activity in the uterine myocyte across gestation. The unfolded protein response senses the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and activates a signaling network that consists of the transmembrane protein kinase eukaryotic translation initiation factor 2 alpha kinase 3/PKR-like-ER kinase (EIF2AK3), which acts to decrease protein translation levels allowing for a lowered need for protein folding during periods of ER stress. However independent of its translational regulatory capacity, EIF2AK3 dependent signals elicit the activation of the transcription factor, nuclear factor, eryt...

Research paper thumbnail of Cytosolic Ca2+ Modulates Golgi Structure Through PKCα-Mediated GRASP55 Phosphorylation

iScience, 2020

Summary It has been well documented that the ER responds to cellular stresses through the unfolde... more Summary It has been well documented that the ER responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tm), and dithiothreitol (DTT), and found that only TG treatment resulted in Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, indicating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevating intracellular Ca2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including phorbol 12-myristate 13-acetate and histamine, modulates Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosoli...

Research paper thumbnail of Faculty of 1000 evaluation for ERK8 is a negative regulator of O-GalNAc glycosylation and cell migration

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature, Apr 1, 2014

ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This... more ER O-glycosylation can be induced through relocalisation GalNAc-Transferases from the Golgi. This process markedly stimulates cell migration and is constitutively activated in more than 60% of breast carcinomas. How this activation is achieved remains unclear. Here, we screened 948 signalling genes using RNAi and imaging. We identified 12 negative regulators of O-glycosylation that all control GalNAc-T sub-cellular localisation. ERK8, an atypical MAPK with high basal kinase activity, is a strong hit and is partially localised at the Golgi. Its inhibition induces the relocation of GalNAc-Ts, but not of KDEL receptors, revealing the existence of two separate COPI-dependent pathways. ERK8 down-regulation, in turn, activates cell motility. In human breast and lung carcinomas, ERK8 expression is reduced while ER O-glycosylation initiation is hyperactivated. In sum, ERK8 appears as a constitutive brake on GalNAc-T relocalisation, and the loss of its expression could drive cancer aggressivity through increased cell motility.

Research paper thumbnail of Nuclear receptor control of opposing macrophage phenotypes in cardiovascular disease

Frontiers in Bioscience, 2012

Introduction 3. Nuclear receptor control of macrophage activation 3.1. Regulation of macrophage a... more Introduction 3. Nuclear receptor control of macrophage activation 3.1. Regulation of macrophage activation by PPARs 3.2. Mineralocorticoid receptor activates proinflammatory macrophage function 3.3. Interaction of nuclear receptors and cytokines 4. Alternatively activated macrophage phenotypes in cardiovascular disease 4.1. Cardiac inflammation, hypertrophy and fibrosis 4.2. Atherosclerosis 4.3. Stroke 5. Heme oxygenase-1 in alternatively activated macrophages 5.1. Atherosclerosis 5.2. Alveolar macrophages and pulmonary hypertension 6. Strategies to study macrophage polarization in disease 7. Summary and perspectives 8. Acknowledgements 9. References

Research paper thumbnail of Cytosolic Ca2+ modulates Golgi structure through PKC-mediated GRASP55 phosphorylation

It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses thr... more It has been well documented that the endoplasmic reticulum (ER) responds to cellular stresses through the unfolded protein response (UPR), but it is unknown how the Golgi responds to similar stresses. In this study, we treated HeLa cells with ER stress inducers, thapsigargin (TG), tunicamycin (Tu) and Dithiothreitol (DTT), and found that only TG treatment caused Golgi fragmentation. TG induced Golgi fragmentation at a low dose and short time when UPR was undetectable, demonstrating that Golgi fragmentation occurs independently of ER stress. Further experiments demonstrated that TG induces Golgi fragmentation through elevated intracellular Ca 2+ and protein kinase Cα (PKCα) activity, which phosphorylates the Golgi stacking protein GRASP55. Significantly, activation of PKCα with other activating or inflammatory agents, including Phorbol 12-myristate 13-acetate (PMA) and histamine, modulates the Golgi structure in a similar fashion. Hence, our study revealed a novel mechanism through which increased cytosolic Ca 2+ modulates Golgi structure and function.

Research paper thumbnail of The Unfolded Protein Response Regulates Uterine Myocyte Antioxidant Responsiveness During Pregnancy

Biology of reproduction, 2016

There is considerable evidence that implicates oxidative stress in the pathophysiology of human p... more There is considerable evidence that implicates oxidative stress in the pathophysiology of human pregnancy complications. However, the role and the mechanism of maintaining an antioxidant prosurvival uterine environment during normal pregnancy is largely unresolved. Herein we report that the highly active uterine unfolded protein response plays a key role in promoting antioxidant activity in the uterine myocyte across gestation. The unfolded protein response (UPR) senses the accumulation of misfolded proteins in the endoplasmic reticulum (ER) and activates a signaling network that consists of the transmembrane protein kinase eukaryotic translation initiation factor 2 alpha kinase 3/PKR-like-ER kinase (EIF2AK3), which acts to decrease protein translation levels, allowing for a lowered need for protein folding during periods of ER stress. However, independent of its translational regulatory capacity, EIF2AK3-dependent signals elicit the activation of the transcription factor, nuclear f...