The Experts below are selected from a list of 51 Experts worldwide ranked by ideXlab platform
Hydar Ali - One of the best experts on this subject based on the ideXlab platform.
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Regulation of C3a receptor signaling in human mast cells by G protein coupled receptor kinases
PloS one, 2011Co-Authors: Qiang Guo, Hariharan Subramanian, Kshitij Gupta, Hydar AliAbstract:Background The Complement Component C3a activates human mast cells via its cell surface G protein coupled receptor (GPCR) C3aR. For most GPCRs, agonist-induced receptor phosphorylation leads to receptor desensitization, internalization as well as activation of downstream signaling pathways such as ERK1/2 phosphorylation. Previous studies in transfected COS cells overexpressing G protein coupled receptor kinases (GRKs) demonstrated that GRK2, GRK3, GRK5 and GRK6 participate in agonist-induced C3aR phosphorylation. However, the roles of these GRKs on the regulation of C3aR signaling and mediator release in human mast cells remain unknown. Methodology/Principal Findings We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of GRK2, GRK3, GRK5 and GRK6 in human mast cell lines, HMC-1 and LAD2, that endogenously express C3aR. Silencing GRK2 or GRK3 expression caused a more sustained Ca2+ mobilization, attenuated C3aR desensitization, and enhanced degranulation as well as ERK1/2 phosphorylation when compared to shRNA control cells. By contrast, GRK5 or GRK6 knockdown had no effect on C3aR desensitization, but caused a significant decrease in C3a-induced mast cell degranulation. Interestingly, GRK5 or GRK6 knockdown rendered mast cells more responsive to C3a for ERK1/2 phosphorylation. Conclusion/Significance This study demonstrates that GRK2 and GRK3 are involved in C3aR desensitization. Furthermore, it reveals the novel finding that GRK5 and GRK6 promote C3a-induced mast cell degranulation but inhibit ERK1/2 phosphorylation via C3aR desensitization-independent mechanisms. These findings thus reveal a new level of complexity for C3aR regulation by GRKs in human mast cells.
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distinct and shared roles of β arrestin 1 and β arrestin 2 on the regulation of C3a receptor signaling in human mast cells
PLOS ONE, 2011Co-Authors: Arpana Vibhuti, Qiang Guo, Hariharan Subramanian, Kshitij Gupta, Hydar AliAbstract:Background The Complement Component C3a induces degranulation in human mast cells via the activation of cell surface G protein coupled receptors (GPCR; C3aR). For most GPCRs, agonist-induced receptor phosphorylation leads to the recruitment of β-arrestin-1/β-arrestin-2; resulting in receptor desensitization and internalization. Activation of GPCRs also leads to ERK1/2 phosphorylation via two temporally distinct pathways; an early response that reflects G protein activation and a delayed response that is G protein independent but requires β-arrestins. The role of β-arrestins on C3aR activation/regulation in human mast cells, however, remains unknown. Methodology/Principal Findings We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of β-arrestin-1 and β-arrrestin-2 in human mast cell lines, HMC-1 and LAD2 that endogenously expresses C3aR. Silencing β-arrestin-2 attenuated C3aR desensitization, blocked agonist-induced receptor internalization and rendered the cells responsive to C3a for enhanced NF-κB activity as well as chemokine generation. By contrast, silencing β-arrestin-1 had no effect on these responses but resulted in a significant decrease in C3a-induced mast cell degranulation. In shRNA control cells, C3a caused a transient ERK1/2 phosphorylation, which peaked at 5 min but disappeared by 10 min. Knockdown of β-arrestin-1, β-arrestin-2 or both enhanced the early response to C3a and rendered the cells responsive for ERK1/2 phosphorylation at later time points (10–30 min). Treatment of cells with pertussis toxin almost completely blocked both early and delayed C3a-induced ERK1/2 phosphorylation in β-arrestin1/2 knockdown cells. Conclusion/Significance This study demonstrates distinct roles for β-arrestins-1 and β-arrestins-2 on C3aR desensitization, internalization, degranulation, NF-κB activation and chemokine generation in human mast cells. It also shows that both β-arrestin-1 and β-arrestin-2 play a novel and shared role in inhibiting G protein-dependent ERK1/2 phosphorylation. These findings reveal a new level of complexity for C3aR regulation by β-arrestins in human mast cells.
Hong Zhou - One of the best experts on this subject based on the ideXlab platform.
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Complement Component C3a plays a critical role in endothelial activation and leukocyte recruitment into the brain
Journal of Neuroinflammation, 2016Co-Authors: Qiang Zou, Xiaodan Ding, Dongyan Shi, Xingxing Zhu, Lixin Liu, Hong ZhouAbstract:Background The Complement system is becoming increasingly recognized as a key participant in many neurodegenerative diseases of the brain. Complement-deficient animals exhibit reduced neuroinflammation.
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Complement Component C3a plays a critical role in endothelial activation and leukocyte recruitment into the brain
Journal of Neuroinflammation, 2016Co-Authors: Qiang Zou, Xiaodan Ding, Dongyan Shi, Xingxing Zhu, Lixin Liu, Hong ZhouAbstract:The Complement system is becoming increasingly recognized as a key participant in many neurodegenerative diseases of the brain. Complement-deficient animals exhibit reduced neuroinflammation. In the present study, we administered intracerebroventricularly lipopolysaccharide (LPS) to mimic local infection of the brain and investigated the role of key Complement Component C3 in brain vasculature endothelial activation and leukocyte recruitment. The degree of neutrophil infiltration was determined by esterase staining. Leukocyte-endothelial interactions were measured using intravital microscopy. Cerebral endothelial activation was evaluated using real-time PCR and Western blotting. Neutrophil infiltration into the brain cortex and hippocampus was significantly reduced in C3−/− mice and C3aR−/− mice but not in C6−/− mice. We detected markedly attenuated leukocyte-endothelial interactions in the brain microvasculature of C3−/− mice. Accordingly, in response to LPS administration, the brain microvasculature in these mice had decreased expression of P-selectin, E-selectin, intercellular cell adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). Depletion of C3 from the circulation also caused reduction in VCAM-1 and E-selectin expression and leukocyte recruitment, suggesting that C3 in the circulation contributed to brain endothelial activation. Furthermore, C3−/− mice exhibited decreased leukocyte recruitment into the brain upon tumor necrosis factor-α (TNF-α) stimulation. C3a activated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) and induced the upregulation of VCAM-1 and ICAM-1 expression in murine primary cerebral endothelial cells in vitro. Our study provides the first evidence that C3a plays a critical role in cerebral endothelial activation and leukocyte recruitment during inflammation in the brain.
Qiang Zou - One of the best experts on this subject based on the ideXlab platform.
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Complement Component C3a plays a critical role in endothelial activation and leukocyte recruitment into the brain
Journal of Neuroinflammation, 2016Co-Authors: Qiang Zou, Xiaodan Ding, Dongyan Shi, Xingxing Zhu, Lixin Liu, Hong ZhouAbstract:Background The Complement system is becoming increasingly recognized as a key participant in many neurodegenerative diseases of the brain. Complement-deficient animals exhibit reduced neuroinflammation.
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Complement Component C3a plays a critical role in endothelial activation and leukocyte recruitment into the brain
Journal of Neuroinflammation, 2016Co-Authors: Qiang Zou, Xiaodan Ding, Dongyan Shi, Xingxing Zhu, Lixin Liu, Hong ZhouAbstract:The Complement system is becoming increasingly recognized as a key participant in many neurodegenerative diseases of the brain. Complement-deficient animals exhibit reduced neuroinflammation. In the present study, we administered intracerebroventricularly lipopolysaccharide (LPS) to mimic local infection of the brain and investigated the role of key Complement Component C3 in brain vasculature endothelial activation and leukocyte recruitment. The degree of neutrophil infiltration was determined by esterase staining. Leukocyte-endothelial interactions were measured using intravital microscopy. Cerebral endothelial activation was evaluated using real-time PCR and Western blotting. Neutrophil infiltration into the brain cortex and hippocampus was significantly reduced in C3−/− mice and C3aR−/− mice but not in C6−/− mice. We detected markedly attenuated leukocyte-endothelial interactions in the brain microvasculature of C3−/− mice. Accordingly, in response to LPS administration, the brain microvasculature in these mice had decreased expression of P-selectin, E-selectin, intercellular cell adhesion molecule 1 (ICAM-1), and vascular cell adhesion molecule 1 (VCAM-1). Depletion of C3 from the circulation also caused reduction in VCAM-1 and E-selectin expression and leukocyte recruitment, suggesting that C3 in the circulation contributed to brain endothelial activation. Furthermore, C3−/− mice exhibited decreased leukocyte recruitment into the brain upon tumor necrosis factor-α (TNF-α) stimulation. C3a activated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) and induced the upregulation of VCAM-1 and ICAM-1 expression in murine primary cerebral endothelial cells in vitro. Our study provides the first evidence that C3a plays a critical role in cerebral endothelial activation and leukocyte recruitment during inflammation in the brain.
Qiang Guo - One of the best experts on this subject based on the ideXlab platform.
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Regulation of C3a receptor signaling in human mast cells by G protein coupled receptor kinases
PloS one, 2011Co-Authors: Qiang Guo, Hariharan Subramanian, Kshitij Gupta, Hydar AliAbstract:Background The Complement Component C3a activates human mast cells via its cell surface G protein coupled receptor (GPCR) C3aR. For most GPCRs, agonist-induced receptor phosphorylation leads to receptor desensitization, internalization as well as activation of downstream signaling pathways such as ERK1/2 phosphorylation. Previous studies in transfected COS cells overexpressing G protein coupled receptor kinases (GRKs) demonstrated that GRK2, GRK3, GRK5 and GRK6 participate in agonist-induced C3aR phosphorylation. However, the roles of these GRKs on the regulation of C3aR signaling and mediator release in human mast cells remain unknown. Methodology/Principal Findings We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of GRK2, GRK3, GRK5 and GRK6 in human mast cell lines, HMC-1 and LAD2, that endogenously express C3aR. Silencing GRK2 or GRK3 expression caused a more sustained Ca2+ mobilization, attenuated C3aR desensitization, and enhanced degranulation as well as ERK1/2 phosphorylation when compared to shRNA control cells. By contrast, GRK5 or GRK6 knockdown had no effect on C3aR desensitization, but caused a significant decrease in C3a-induced mast cell degranulation. Interestingly, GRK5 or GRK6 knockdown rendered mast cells more responsive to C3a for ERK1/2 phosphorylation. Conclusion/Significance This study demonstrates that GRK2 and GRK3 are involved in C3aR desensitization. Furthermore, it reveals the novel finding that GRK5 and GRK6 promote C3a-induced mast cell degranulation but inhibit ERK1/2 phosphorylation via C3aR desensitization-independent mechanisms. These findings thus reveal a new level of complexity for C3aR regulation by GRKs in human mast cells.
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distinct and shared roles of β arrestin 1 and β arrestin 2 on the regulation of C3a receptor signaling in human mast cells
PLOS ONE, 2011Co-Authors: Arpana Vibhuti, Qiang Guo, Hariharan Subramanian, Kshitij Gupta, Hydar AliAbstract:Background The Complement Component C3a induces degranulation in human mast cells via the activation of cell surface G protein coupled receptors (GPCR; C3aR). For most GPCRs, agonist-induced receptor phosphorylation leads to the recruitment of β-arrestin-1/β-arrestin-2; resulting in receptor desensitization and internalization. Activation of GPCRs also leads to ERK1/2 phosphorylation via two temporally distinct pathways; an early response that reflects G protein activation and a delayed response that is G protein independent but requires β-arrestins. The role of β-arrestins on C3aR activation/regulation in human mast cells, however, remains unknown. Methodology/Principal Findings We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of β-arrestin-1 and β-arrrestin-2 in human mast cell lines, HMC-1 and LAD2 that endogenously expresses C3aR. Silencing β-arrestin-2 attenuated C3aR desensitization, blocked agonist-induced receptor internalization and rendered the cells responsive to C3a for enhanced NF-κB activity as well as chemokine generation. By contrast, silencing β-arrestin-1 had no effect on these responses but resulted in a significant decrease in C3a-induced mast cell degranulation. In shRNA control cells, C3a caused a transient ERK1/2 phosphorylation, which peaked at 5 min but disappeared by 10 min. Knockdown of β-arrestin-1, β-arrestin-2 or both enhanced the early response to C3a and rendered the cells responsive for ERK1/2 phosphorylation at later time points (10–30 min). Treatment of cells with pertussis toxin almost completely blocked both early and delayed C3a-induced ERK1/2 phosphorylation in β-arrestin1/2 knockdown cells. Conclusion/Significance This study demonstrates distinct roles for β-arrestins-1 and β-arrestins-2 on C3aR desensitization, internalization, degranulation, NF-κB activation and chemokine generation in human mast cells. It also shows that both β-arrestin-1 and β-arrestin-2 play a novel and shared role in inhibiting G protein-dependent ERK1/2 phosphorylation. These findings reveal a new level of complexity for C3aR regulation by β-arrestins in human mast cells.
Hariharan Subramanian - One of the best experts on this subject based on the ideXlab platform.
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Regulation of C3a receptor signaling in human mast cells by G protein coupled receptor kinases
PloS one, 2011Co-Authors: Qiang Guo, Hariharan Subramanian, Kshitij Gupta, Hydar AliAbstract:Background The Complement Component C3a activates human mast cells via its cell surface G protein coupled receptor (GPCR) C3aR. For most GPCRs, agonist-induced receptor phosphorylation leads to receptor desensitization, internalization as well as activation of downstream signaling pathways such as ERK1/2 phosphorylation. Previous studies in transfected COS cells overexpressing G protein coupled receptor kinases (GRKs) demonstrated that GRK2, GRK3, GRK5 and GRK6 participate in agonist-induced C3aR phosphorylation. However, the roles of these GRKs on the regulation of C3aR signaling and mediator release in human mast cells remain unknown. Methodology/Principal Findings We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of GRK2, GRK3, GRK5 and GRK6 in human mast cell lines, HMC-1 and LAD2, that endogenously express C3aR. Silencing GRK2 or GRK3 expression caused a more sustained Ca2+ mobilization, attenuated C3aR desensitization, and enhanced degranulation as well as ERK1/2 phosphorylation when compared to shRNA control cells. By contrast, GRK5 or GRK6 knockdown had no effect on C3aR desensitization, but caused a significant decrease in C3a-induced mast cell degranulation. Interestingly, GRK5 or GRK6 knockdown rendered mast cells more responsive to C3a for ERK1/2 phosphorylation. Conclusion/Significance This study demonstrates that GRK2 and GRK3 are involved in C3aR desensitization. Furthermore, it reveals the novel finding that GRK5 and GRK6 promote C3a-induced mast cell degranulation but inhibit ERK1/2 phosphorylation via C3aR desensitization-independent mechanisms. These findings thus reveal a new level of complexity for C3aR regulation by GRKs in human mast cells.
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distinct and shared roles of β arrestin 1 and β arrestin 2 on the regulation of C3a receptor signaling in human mast cells
PLOS ONE, 2011Co-Authors: Arpana Vibhuti, Qiang Guo, Hariharan Subramanian, Kshitij Gupta, Hydar AliAbstract:Background The Complement Component C3a induces degranulation in human mast cells via the activation of cell surface G protein coupled receptors (GPCR; C3aR). For most GPCRs, agonist-induced receptor phosphorylation leads to the recruitment of β-arrestin-1/β-arrestin-2; resulting in receptor desensitization and internalization. Activation of GPCRs also leads to ERK1/2 phosphorylation via two temporally distinct pathways; an early response that reflects G protein activation and a delayed response that is G protein independent but requires β-arrestins. The role of β-arrestins on C3aR activation/regulation in human mast cells, however, remains unknown. Methodology/Principal Findings We utilized lentivirus short hairpin (sh)RNA to stably knockdown the expression of β-arrestin-1 and β-arrrestin-2 in human mast cell lines, HMC-1 and LAD2 that endogenously expresses C3aR. Silencing β-arrestin-2 attenuated C3aR desensitization, blocked agonist-induced receptor internalization and rendered the cells responsive to C3a for enhanced NF-κB activity as well as chemokine generation. By contrast, silencing β-arrestin-1 had no effect on these responses but resulted in a significant decrease in C3a-induced mast cell degranulation. In shRNA control cells, C3a caused a transient ERK1/2 phosphorylation, which peaked at 5 min but disappeared by 10 min. Knockdown of β-arrestin-1, β-arrestin-2 or both enhanced the early response to C3a and rendered the cells responsive for ERK1/2 phosphorylation at later time points (10–30 min). Treatment of cells with pertussis toxin almost completely blocked both early and delayed C3a-induced ERK1/2 phosphorylation in β-arrestin1/2 knockdown cells. Conclusion/Significance This study demonstrates distinct roles for β-arrestins-1 and β-arrestins-2 on C3aR desensitization, internalization, degranulation, NF-κB activation and chemokine generation in human mast cells. It also shows that both β-arrestin-1 and β-arrestin-2 play a novel and shared role in inhibiting G protein-dependent ERK1/2 phosphorylation. These findings reveal a new level of complexity for C3aR regulation by β-arrestins in human mast cells.