The Experts below are selected from a list of 42 Experts worldwide ranked by ideXlab platform
Shin Pei Chai - One of the best experts on this subject based on the ideXlab platform.
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4-Bromocrotonic Acid enhances basal but inhibits insulin-stimulated glucose transport in 3T3-L1 adipocytes.
Biochemical and Biophysical Research Communications, 1998Co-Authors: Shin Pei Chai, Ching-fai Kwok, Jim C FongAbstract:Abstract Inhibitors of fatty Acid oxidation, 2-Bromopalmitic Acid (Br-C16) and 4-bromocrotonic Acid (Br-C4) were examined for their effect on glucose transport in 3T3-L1 adipocytes. Whereas Br-C16 was without effect, Br-C4 augmented basal but inhibited insulin-stimulated 2-deoxyglucose uptake in a dose- and time-dependent manner. Immunoblot analysis indicated that following Br-C4 pretreatment, the content of GLUT1 in plasma membranes was increased whereas insulin-induced translocation of GLUT4 was greatly eliminated. The total cellular amount of GLUT1 or GLUT4, on the other hand, was not altered. Thus these results seem to suggest that Br-C4 has opposite effect on basal and insulin-stimulated glucose transport by a mechanism other than its inhibition of fatty Acid oxidation. The translocation processes for both GLUT1 and GLUT4 transporters appears to be altered.
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differential inhibition of lipolysis by 2 Bromopalmitic Acid and 4 bromocrotonic Acid in 3t3 l1 adipocytes
Biochimica et Biophysica Acta, 1997Co-Authors: Jim C Fong, Shin Pei ChaiAbstract:Abstract Two inhibitors of fatty Acid oxidation, 2-Bromopalmitic Acid (Br-C16) and 4-bromocrotonic Acid (Br-C4) were examined for their effect on lipolysis in 3T3-L1 adipocytes. Both agents inhibited in a dose-dependent manner the rate of oxidation of exogenously added [1-14C]palmitate with similar time-courses, reaching a plateau at 3–9 h. While Br-C16 at 50 μM and 100 μM inhibited palmitate oxidation by approximately 40% and 60%, respectively, pretreatment with both concentrations inhibited lipolysis in washed cells in an almost identical manner. The magnitude of inhibition increased with time of pretreatment. On the other hand, like inhibition of fatty Acid oxidation, inhibition of lipolysis by Br-C4 pretreatment was dose-dependent with maximal inhibition reached after 3 h pretreatment. The finding that isoproterenol- and dibutyryl cAMP-stimulated lipolysis were similarly suppressed by either Br-C4 or Br-C16 pretreatment, suggesting that a step distal to cAMP formation was involved. In addition, while the inhibitory effect of Br-C16 was not significantly influenced, the inhibition of lipolysis caused by Br-C4 was attenuated by pretreating cells with crotonic Acid, octanoate, or palmitate. The longer chain-length of the fatty Acids the cells were exposed, the stronger attenuation of the inhibition caused by Br-C4 was observed. Moreover, whereas pretreatment with Br-C16 was without effect, pretreatment with Br-C4 significantly decreased hormone-sensitive lipase (HSL) activity in cell extracts, albeit to an extent much smaller than its inhibitory effect on lipolysis. In conclusion, these results indicate that irreversible inhibition of lipolysis by Br-C16 or Br-C4 cannot be attributed to their effect on fatty Acid oxidation. Some factor capable of modulating HSL activity seems to be involved.
Jim C Fong - One of the best experts on this subject based on the ideXlab platform.
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4-Bromocrotonic Acid enhances basal but inhibits insulin-stimulated glucose transport in 3T3-L1 adipocytes.
Biochemical and Biophysical Research Communications, 1998Co-Authors: Shin Pei Chai, Ching-fai Kwok, Jim C FongAbstract:Abstract Inhibitors of fatty Acid oxidation, 2-Bromopalmitic Acid (Br-C16) and 4-bromocrotonic Acid (Br-C4) were examined for their effect on glucose transport in 3T3-L1 adipocytes. Whereas Br-C16 was without effect, Br-C4 augmented basal but inhibited insulin-stimulated 2-deoxyglucose uptake in a dose- and time-dependent manner. Immunoblot analysis indicated that following Br-C4 pretreatment, the content of GLUT1 in plasma membranes was increased whereas insulin-induced translocation of GLUT4 was greatly eliminated. The total cellular amount of GLUT1 or GLUT4, on the other hand, was not altered. Thus these results seem to suggest that Br-C4 has opposite effect on basal and insulin-stimulated glucose transport by a mechanism other than its inhibition of fatty Acid oxidation. The translocation processes for both GLUT1 and GLUT4 transporters appears to be altered.
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differential inhibition of lipolysis by 2 Bromopalmitic Acid and 4 bromocrotonic Acid in 3t3 l1 adipocytes
Biochimica et Biophysica Acta, 1997Co-Authors: Jim C Fong, Shin Pei ChaiAbstract:Abstract Two inhibitors of fatty Acid oxidation, 2-Bromopalmitic Acid (Br-C16) and 4-bromocrotonic Acid (Br-C4) were examined for their effect on lipolysis in 3T3-L1 adipocytes. Both agents inhibited in a dose-dependent manner the rate of oxidation of exogenously added [1-14C]palmitate with similar time-courses, reaching a plateau at 3–9 h. While Br-C16 at 50 μM and 100 μM inhibited palmitate oxidation by approximately 40% and 60%, respectively, pretreatment with both concentrations inhibited lipolysis in washed cells in an almost identical manner. The magnitude of inhibition increased with time of pretreatment. On the other hand, like inhibition of fatty Acid oxidation, inhibition of lipolysis by Br-C4 pretreatment was dose-dependent with maximal inhibition reached after 3 h pretreatment. The finding that isoproterenol- and dibutyryl cAMP-stimulated lipolysis were similarly suppressed by either Br-C4 or Br-C16 pretreatment, suggesting that a step distal to cAMP formation was involved. In addition, while the inhibitory effect of Br-C16 was not significantly influenced, the inhibition of lipolysis caused by Br-C4 was attenuated by pretreating cells with crotonic Acid, octanoate, or palmitate. The longer chain-length of the fatty Acids the cells were exposed, the stronger attenuation of the inhibition caused by Br-C4 was observed. Moreover, whereas pretreatment with Br-C16 was without effect, pretreatment with Br-C4 significantly decreased hormone-sensitive lipase (HSL) activity in cell extracts, albeit to an extent much smaller than its inhibitory effect on lipolysis. In conclusion, these results indicate that irreversible inhibition of lipolysis by Br-C16 or Br-C4 cannot be attributed to their effect on fatty Acid oxidation. Some factor capable of modulating HSL activity seems to be involved.
Andrzej Sobota - One of the best experts on this subject based on the ideXlab platform.
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Phosphorylation of FcgammaRIIA is required for the receptor-induced actin rearrangement and capping: the role of membrane rafts.
Journal of cell science, 2003Co-Authors: Katarzyna Kwiatkowska, Jürgen Frey, Andrzej SobotaAbstract:Activation of Fcgamma receptor II (FcgammaRII) induces rearrangement of the actin-based cytoskeleton that serves as a driving force for FcgammaRII-mediated phagocytosis and FcgammaRII capping. To get insight into the signaling events that lead to the actin reorganization we investigated the role of raft-associated Src family tyrosine kinases in capping of FcgammaRII in U937 cells. After crosslinking, FcgammaRII was found to be recruited to detergent-resistant membrane domains (DRMs), rafts, where it coexisted with Lyn kinase and underwent tyrosine phosphorylation. Lyn was displaced from DRMs under the influence of DL-alpha-hydroxymyristic Acid and 2-Bromopalmitic Acid, agents blocking N-terminal myristoylation and palmitoylation of proteins, respectively, and after disruption of DRM integrity by depletion of plasma membrane cholesterol with beta-cyclodextrin. Under these conditions, phosphorylation of the crosslinked FcgammaRII was diminished and assembly of FcgammaRII caps was blocked. The similar reduction of FcgammaRII cap formation correlated with inhibition of receptor phosphorylation was achieved with the use of PP1 and herbimycin A, specific inhibitors of Src family tyrosine kinases. Phosphorylation of FcgammaRIIA expressed in BHK cells, lacking endogenous FcgammaRs, was abolished by substitution of tyrosine 298 by phenylalanine in the ITAM of the receptor. The mutant receptor did not undergo translocation towards cap-like structures and failed to promote the receptor-mediated spreading of the cells, as compared to BHK cells transfected with the wild-type FcgammaRIIA. On the basis of these data, we suggest that tyrosine phosphorylation of activated FcgammaRIIA by raft-residing tyrosine kinases of the Src family triggers signaling pathways that control the rearrangement of the actin cytoskeleton required for FcgammaRII-mediated motility.
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Phosphorylation of FcgammaRIIA is required for the receptor-induced actin rearrangement and capping: the role of membrane rafts.
Journal of Cell Science, 2002Co-Authors: Katarzyna Kwiatkowska, Jürgen Frey, Andrzej SobotaAbstract:Activation of Fcγ receptor II (FcγRII) induces rearrangement of the actin-based cytoskeleton that serves as a driving force for FcγRII-mediated phagocytosis and FcγRII capping. To get insight into the signaling events that lead to the actin reorganization we investigated the role of raft-associated Src family tyrosine kinases in capping of FcγRII in U937 cells. After crosslinking, FcγRII was found to be recruited to detergent-resistant membrane domains (DRMs), rafts, where it coexisted with Lyn kinase and underwent tyrosine phosphorylation. Lyn was displaced from DRMs under the influence of DL-α-hydroxymyristic Acid and 2-Bromopalmitic Acid, agents blocking N-terminal myristoylation and palmitoylation of proteins, respectively, and after disruption of DRM integrity by depletion of plasma membrane cholesterol withβ -cyclodextrin. Under these conditions, phosphorylation of the crosslinked FcγRII was diminished and assembly of FcγRII caps was blocked. The similar reduction of FcγRII cap formation correlated with inhibition of receptor phosphorylation was achieved with the use of PP1 and herbimycin A, specific inhibitors of Src family tyrosine kinases. Phosphorylation of FcγRIIA expressed in BHK cells, lacking endogenous FcγRs, was abolished by substitution of tyrosine 298 by phenylalanine in the ITAM of the receptor. The mutant receptor did not undergo translocation towards cap-like structures and failed to promote the receptor-mediated spreading of the cells, as compared to BHK cells transfected with the wild-type FcγRIIA. On the basis of these data, we suggest that tyrosine phosphorylation of activated FcγRIIA by raft-residing tyrosine kinases of the Src family triggers signaling pathways that control the rearrangement of the actin cytoskeleton required for FcγRII-mediated motility.
Katarzyna Kwiatkowska - One of the best experts on this subject based on the ideXlab platform.
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Phosphorylation of FcgammaRIIA is required for the receptor-induced actin rearrangement and capping: the role of membrane rafts.
Journal of cell science, 2003Co-Authors: Katarzyna Kwiatkowska, Jürgen Frey, Andrzej SobotaAbstract:Activation of Fcgamma receptor II (FcgammaRII) induces rearrangement of the actin-based cytoskeleton that serves as a driving force for FcgammaRII-mediated phagocytosis and FcgammaRII capping. To get insight into the signaling events that lead to the actin reorganization we investigated the role of raft-associated Src family tyrosine kinases in capping of FcgammaRII in U937 cells. After crosslinking, FcgammaRII was found to be recruited to detergent-resistant membrane domains (DRMs), rafts, where it coexisted with Lyn kinase and underwent tyrosine phosphorylation. Lyn was displaced from DRMs under the influence of DL-alpha-hydroxymyristic Acid and 2-Bromopalmitic Acid, agents blocking N-terminal myristoylation and palmitoylation of proteins, respectively, and after disruption of DRM integrity by depletion of plasma membrane cholesterol with beta-cyclodextrin. Under these conditions, phosphorylation of the crosslinked FcgammaRII was diminished and assembly of FcgammaRII caps was blocked. The similar reduction of FcgammaRII cap formation correlated with inhibition of receptor phosphorylation was achieved with the use of PP1 and herbimycin A, specific inhibitors of Src family tyrosine kinases. Phosphorylation of FcgammaRIIA expressed in BHK cells, lacking endogenous FcgammaRs, was abolished by substitution of tyrosine 298 by phenylalanine in the ITAM of the receptor. The mutant receptor did not undergo translocation towards cap-like structures and failed to promote the receptor-mediated spreading of the cells, as compared to BHK cells transfected with the wild-type FcgammaRIIA. On the basis of these data, we suggest that tyrosine phosphorylation of activated FcgammaRIIA by raft-residing tyrosine kinases of the Src family triggers signaling pathways that control the rearrangement of the actin cytoskeleton required for FcgammaRII-mediated motility.
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Phosphorylation of FcgammaRIIA is required for the receptor-induced actin rearrangement and capping: the role of membrane rafts.
Journal of Cell Science, 2002Co-Authors: Katarzyna Kwiatkowska, Jürgen Frey, Andrzej SobotaAbstract:Activation of Fcγ receptor II (FcγRII) induces rearrangement of the actin-based cytoskeleton that serves as a driving force for FcγRII-mediated phagocytosis and FcγRII capping. To get insight into the signaling events that lead to the actin reorganization we investigated the role of raft-associated Src family tyrosine kinases in capping of FcγRII in U937 cells. After crosslinking, FcγRII was found to be recruited to detergent-resistant membrane domains (DRMs), rafts, where it coexisted with Lyn kinase and underwent tyrosine phosphorylation. Lyn was displaced from DRMs under the influence of DL-α-hydroxymyristic Acid and 2-Bromopalmitic Acid, agents blocking N-terminal myristoylation and palmitoylation of proteins, respectively, and after disruption of DRM integrity by depletion of plasma membrane cholesterol withβ -cyclodextrin. Under these conditions, phosphorylation of the crosslinked FcγRII was diminished and assembly of FcγRII caps was blocked. The similar reduction of FcγRII cap formation correlated with inhibition of receptor phosphorylation was achieved with the use of PP1 and herbimycin A, specific inhibitors of Src family tyrosine kinases. Phosphorylation of FcγRIIA expressed in BHK cells, lacking endogenous FcγRs, was abolished by substitution of tyrosine 298 by phenylalanine in the ITAM of the receptor. The mutant receptor did not undergo translocation towards cap-like structures and failed to promote the receptor-mediated spreading of the cells, as compared to BHK cells transfected with the wild-type FcγRIIA. On the basis of these data, we suggest that tyrosine phosphorylation of activated FcγRIIA by raft-residing tyrosine kinases of the Src family triggers signaling pathways that control the rearrangement of the actin cytoskeleton required for FcγRII-mediated motility.
Jürgen Frey - One of the best experts on this subject based on the ideXlab platform.
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Phosphorylation of FcgammaRIIA is required for the receptor-induced actin rearrangement and capping: the role of membrane rafts.
Journal of cell science, 2003Co-Authors: Katarzyna Kwiatkowska, Jürgen Frey, Andrzej SobotaAbstract:Activation of Fcgamma receptor II (FcgammaRII) induces rearrangement of the actin-based cytoskeleton that serves as a driving force for FcgammaRII-mediated phagocytosis and FcgammaRII capping. To get insight into the signaling events that lead to the actin reorganization we investigated the role of raft-associated Src family tyrosine kinases in capping of FcgammaRII in U937 cells. After crosslinking, FcgammaRII was found to be recruited to detergent-resistant membrane domains (DRMs), rafts, where it coexisted with Lyn kinase and underwent tyrosine phosphorylation. Lyn was displaced from DRMs under the influence of DL-alpha-hydroxymyristic Acid and 2-Bromopalmitic Acid, agents blocking N-terminal myristoylation and palmitoylation of proteins, respectively, and after disruption of DRM integrity by depletion of plasma membrane cholesterol with beta-cyclodextrin. Under these conditions, phosphorylation of the crosslinked FcgammaRII was diminished and assembly of FcgammaRII caps was blocked. The similar reduction of FcgammaRII cap formation correlated with inhibition of receptor phosphorylation was achieved with the use of PP1 and herbimycin A, specific inhibitors of Src family tyrosine kinases. Phosphorylation of FcgammaRIIA expressed in BHK cells, lacking endogenous FcgammaRs, was abolished by substitution of tyrosine 298 by phenylalanine in the ITAM of the receptor. The mutant receptor did not undergo translocation towards cap-like structures and failed to promote the receptor-mediated spreading of the cells, as compared to BHK cells transfected with the wild-type FcgammaRIIA. On the basis of these data, we suggest that tyrosine phosphorylation of activated FcgammaRIIA by raft-residing tyrosine kinases of the Src family triggers signaling pathways that control the rearrangement of the actin cytoskeleton required for FcgammaRII-mediated motility.
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Phosphorylation of FcgammaRIIA is required for the receptor-induced actin rearrangement and capping: the role of membrane rafts.
Journal of Cell Science, 2002Co-Authors: Katarzyna Kwiatkowska, Jürgen Frey, Andrzej SobotaAbstract:Activation of Fcγ receptor II (FcγRII) induces rearrangement of the actin-based cytoskeleton that serves as a driving force for FcγRII-mediated phagocytosis and FcγRII capping. To get insight into the signaling events that lead to the actin reorganization we investigated the role of raft-associated Src family tyrosine kinases in capping of FcγRII in U937 cells. After crosslinking, FcγRII was found to be recruited to detergent-resistant membrane domains (DRMs), rafts, where it coexisted with Lyn kinase and underwent tyrosine phosphorylation. Lyn was displaced from DRMs under the influence of DL-α-hydroxymyristic Acid and 2-Bromopalmitic Acid, agents blocking N-terminal myristoylation and palmitoylation of proteins, respectively, and after disruption of DRM integrity by depletion of plasma membrane cholesterol withβ -cyclodextrin. Under these conditions, phosphorylation of the crosslinked FcγRII was diminished and assembly of FcγRII caps was blocked. The similar reduction of FcγRII cap formation correlated with inhibition of receptor phosphorylation was achieved with the use of PP1 and herbimycin A, specific inhibitors of Src family tyrosine kinases. Phosphorylation of FcγRIIA expressed in BHK cells, lacking endogenous FcγRs, was abolished by substitution of tyrosine 298 by phenylalanine in the ITAM of the receptor. The mutant receptor did not undergo translocation towards cap-like structures and failed to promote the receptor-mediated spreading of the cells, as compared to BHK cells transfected with the wild-type FcγRIIA. On the basis of these data, we suggest that tyrosine phosphorylation of activated FcγRIIA by raft-residing tyrosine kinases of the Src family triggers signaling pathways that control the rearrangement of the actin cytoskeleton required for FcγRII-mediated motility.
