The Experts below are selected from a list of 159 Experts worldwide ranked by ideXlab platform
Yoshihisa Kurachi - One of the best experts on this subject based on the ideXlab platform.
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phosphatidylinositol 3 4 5 trisphosphate and ca2 calmodulin competitively bind to the regulators of g Protein signalling rgs domain of RGS4 and reciprocally regulate its action
Biochemical Journal, 2005Co-Authors: Masaru Ishii, Mitsuhiko Yamada, Yukio Hosaka, Satoru Fujita, Yoshihisa KurachiAbstract:RGS (regulators of G-Protein signalling) are a diverse group of Proteins, which accelerate intrinsic GTP hydrolysis on heterotrimeric G-Protein α subunits. They are involved in the control of a physiological behaviour known as ‘relaxation’ of G-Protein-gated K+ channels in cardiac myocytes. The GTPase-accelerating activity of cardiac RGS Proteins, such as RGS4, is inhibited by PtdIns(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) and this inhibition is cancelled by Ca2+/calmodulin (CaM) formed during membrane depolarization. G-Protein-gated K+ channel activity decreases on depolarization owing to the facilitation of GTPase-activating Protein activity by RGS Proteins and vice versa on hyperpolarization. The molecular mechanism responsible for this reciprocal control of RGS action by PtdIns(3,4,5)P3 and Ca2+/CaM, however, has not been fully elucidated. Using lipid–Protein co-sedimentation assay and surface plasmon resonance measurements, we show in the present study that the control of the GTPase-accelerating activity of the RGS4 Protein is achieved through the competitive binding of PtdIns(3,4,5)P3 and Ca2+/CaM within its RGS domain. Competitive binding occurs exclusively within the RGS domain and involves a cluster of positively charged residues located on the surface opposite to the Gα interaction site. In the RGS Proteins conserving these residues, the reciprocal regulation by PtdIns(3,4,5)P3 and Ca2+/CaM may be important for their physiological regulation of G-Protein signalling.
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Phosphatidylinositol 3,4,5-trisphosphate and Ca2+/calmodulin competitively bind to the regulators of G-Protein-signalling (RGS) domain of RGS4 and reciprocally regulate its action.
Biochemical Journal, 2004Co-Authors: Masaru Ishii, Mitsuhiko Yamada, Yukio Hosaka, Satoru Fujita, Yoshihisa KurachiAbstract:RGS (regulators of G-Protein signalling) are a diverse group of Proteins, which accelerate intrinsic GTP hydrolysis on heterotrimeric G-Protein α subunits. They are involved in the control of a physiological behaviour known as ‘relaxation’ of G-Protein-gated K+ channels in cardiac myocytes. The GTPase-accelerating activity of cardiac RGS Proteins, such as RGS4, is inhibited by PtdIns(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) and this inhibition is cancelled by Ca2+/calmodulin (CaM) formed during membrane depolarization. G-Protein-gated K+ channel activity decreases on depolarization owing to the facilitation of GTPase-activating Protein activity by RGS Proteins and vice versa on hyperpolarization. The molecular mechanism responsible for this reciprocal control of RGS action by PtdIns(3,4,5)P3 and Ca2+/CaM, however, has not been fully elucidated. Using lipid–Protein co-sedimentation assay and surface plasmon resonance measurements, we show in the present study that the control of the GTPase-accelerating activity of the RGS4 Protein is achieved through the competitive binding of PtdIns(3,4,5)P3 and Ca2+/CaM within its RGS domain. Competitive binding occurs exclusively within the RGS domain and involves a cluster of positively charged residues located on the surface opposite to the Gα interaction site. In the RGS Proteins conserving these residues, the reciprocal regulation by PtdIns(3,4,5)P3 and Ca2+/CaM may be important for their physiological regulation of G-Protein signalling.
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pip3 inhibition of rgs Protein and its reversal by ca2 calmodulin mediate voltage dependent control of the g Protein cycle in a cardiac k channel
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Masaru Ishii, Atsushi Inanobe, Yoshihisa KurachiAbstract:Regulators of G Protein signaling (RGS) accelerate intrinsic GTP hydrolysis on α subunits of trimeric G Proteins and play crucial roles in the physiological regulation of G Protein-mediated cell signaling. The control mechanisms of the action of RGS Proteins per se are poorly clarified, however. We recently showed a physiological mode of action of a RGS Protein in cardiac myocytes. The voltage-dependent formation of Ca2+/calmodulin facilitated the GTPase activity of RGS by an unidentified mechanism, which underlay the “relaxation” behavior of G Protein-gated K+ (KG) channels. Here we report the mechanism which is the reversal by Ca2+/calmodulin of phosphatidylinositol-3,4,5,-trisphosphate (PIP3)-mediated inhibition of RGS. Purified RGS4 Protein alone inhibited GTP-induced KG channel activity in inside-out patches from atrial myocytes. The inhibitory effect of RGS4 was reduced by PIP3 and restored by addition of Ca2+/calmodulin. The intracellular application of anti-PIP3 antibody abolished the RGS-dependent relaxation behavior of KG current in atrial myocytes. This study, therefore, reveals a general physiological control mechanism of RGS Proteins by lipid–Protein interaction.
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PIP3 inhibition of RGS Protein and its reversal by Ca2+/calmodulin mediate voltage-dependent control of the G Protein cycle in a cardiac K+ channel
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Masaru Ishii, Atsushi Inanobe, Yoshihisa KurachiAbstract:Regulators of G Protein signaling (RGS) accelerate intrinsic GTP hydrolysis on alpha subunits of trimeric G Proteins and play crucial roles in the physiological regulation of G Protein-mediated cell signaling. The control mechanisms of the action of RGS Proteins per se are poorly clarified, however. We recently showed a physiological mode of action of a RGS Protein in cardiac myocytes. The voltage-dependent formation of Ca2+/calmodulin facilitated the GTPase activity of RGS by an unidentified mechanism, which underlay the "relaxation" behavior of G Protein-gated K+ (K(G)) channels. Here we report the mechanism which is the reversal by Ca2+/calmodulin of phosphatidylinositol-3,4,5,-trisphosphate (PIP3)-mediated inhibition of RGS. Purified RGS4 Protein alone inhibited GTP-induced K(G) channel activity in inside-out patches from atrial myocytes. The inhibitory effect of RGS4 was reduced by PIP3 and restored by addition of Ca2+/calmodulin. The intracellular application of anti-PIP3 antibody abolished the RGS-dependent relaxation behavior of K(G) current in atrial myocytes. This study, therefore, reveals a general physiological control mechanism of RGS Proteins by lipid-Protein interaction.
Masaru Ishii - One of the best experts on this subject based on the ideXlab platform.
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phosphatidylinositol 3 4 5 trisphosphate and ca2 calmodulin competitively bind to the regulators of g Protein signalling rgs domain of RGS4 and reciprocally regulate its action
Biochemical Journal, 2005Co-Authors: Masaru Ishii, Mitsuhiko Yamada, Yukio Hosaka, Satoru Fujita, Yoshihisa KurachiAbstract:RGS (regulators of G-Protein signalling) are a diverse group of Proteins, which accelerate intrinsic GTP hydrolysis on heterotrimeric G-Protein α subunits. They are involved in the control of a physiological behaviour known as ‘relaxation’ of G-Protein-gated K+ channels in cardiac myocytes. The GTPase-accelerating activity of cardiac RGS Proteins, such as RGS4, is inhibited by PtdIns(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) and this inhibition is cancelled by Ca2+/calmodulin (CaM) formed during membrane depolarization. G-Protein-gated K+ channel activity decreases on depolarization owing to the facilitation of GTPase-activating Protein activity by RGS Proteins and vice versa on hyperpolarization. The molecular mechanism responsible for this reciprocal control of RGS action by PtdIns(3,4,5)P3 and Ca2+/CaM, however, has not been fully elucidated. Using lipid–Protein co-sedimentation assay and surface plasmon resonance measurements, we show in the present study that the control of the GTPase-accelerating activity of the RGS4 Protein is achieved through the competitive binding of PtdIns(3,4,5)P3 and Ca2+/CaM within its RGS domain. Competitive binding occurs exclusively within the RGS domain and involves a cluster of positively charged residues located on the surface opposite to the Gα interaction site. In the RGS Proteins conserving these residues, the reciprocal regulation by PtdIns(3,4,5)P3 and Ca2+/CaM may be important for their physiological regulation of G-Protein signalling.
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Phosphatidylinositol 3,4,5-trisphosphate and Ca2+/calmodulin competitively bind to the regulators of G-Protein-signalling (RGS) domain of RGS4 and reciprocally regulate its action.
Biochemical Journal, 2004Co-Authors: Masaru Ishii, Mitsuhiko Yamada, Yukio Hosaka, Satoru Fujita, Yoshihisa KurachiAbstract:RGS (regulators of G-Protein signalling) are a diverse group of Proteins, which accelerate intrinsic GTP hydrolysis on heterotrimeric G-Protein α subunits. They are involved in the control of a physiological behaviour known as ‘relaxation’ of G-Protein-gated K+ channels in cardiac myocytes. The GTPase-accelerating activity of cardiac RGS Proteins, such as RGS4, is inhibited by PtdIns(3,4,5)P3 (phosphatidylinositol 3,4,5-trisphosphate) and this inhibition is cancelled by Ca2+/calmodulin (CaM) formed during membrane depolarization. G-Protein-gated K+ channel activity decreases on depolarization owing to the facilitation of GTPase-activating Protein activity by RGS Proteins and vice versa on hyperpolarization. The molecular mechanism responsible for this reciprocal control of RGS action by PtdIns(3,4,5)P3 and Ca2+/CaM, however, has not been fully elucidated. Using lipid–Protein co-sedimentation assay and surface plasmon resonance measurements, we show in the present study that the control of the GTPase-accelerating activity of the RGS4 Protein is achieved through the competitive binding of PtdIns(3,4,5)P3 and Ca2+/CaM within its RGS domain. Competitive binding occurs exclusively within the RGS domain and involves a cluster of positively charged residues located on the surface opposite to the Gα interaction site. In the RGS Proteins conserving these residues, the reciprocal regulation by PtdIns(3,4,5)P3 and Ca2+/CaM may be important for their physiological regulation of G-Protein signalling.
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pip3 inhibition of rgs Protein and its reversal by ca2 calmodulin mediate voltage dependent control of the g Protein cycle in a cardiac k channel
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Masaru Ishii, Atsushi Inanobe, Yoshihisa KurachiAbstract:Regulators of G Protein signaling (RGS) accelerate intrinsic GTP hydrolysis on α subunits of trimeric G Proteins and play crucial roles in the physiological regulation of G Protein-mediated cell signaling. The control mechanisms of the action of RGS Proteins per se are poorly clarified, however. We recently showed a physiological mode of action of a RGS Protein in cardiac myocytes. The voltage-dependent formation of Ca2+/calmodulin facilitated the GTPase activity of RGS by an unidentified mechanism, which underlay the “relaxation” behavior of G Protein-gated K+ (KG) channels. Here we report the mechanism which is the reversal by Ca2+/calmodulin of phosphatidylinositol-3,4,5,-trisphosphate (PIP3)-mediated inhibition of RGS. Purified RGS4 Protein alone inhibited GTP-induced KG channel activity in inside-out patches from atrial myocytes. The inhibitory effect of RGS4 was reduced by PIP3 and restored by addition of Ca2+/calmodulin. The intracellular application of anti-PIP3 antibody abolished the RGS-dependent relaxation behavior of KG current in atrial myocytes. This study, therefore, reveals a general physiological control mechanism of RGS Proteins by lipid–Protein interaction.
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PIP3 inhibition of RGS Protein and its reversal by Ca2+/calmodulin mediate voltage-dependent control of the G Protein cycle in a cardiac K+ channel
Proceedings of the National Academy of Sciences of the United States of America, 2002Co-Authors: Masaru Ishii, Atsushi Inanobe, Yoshihisa KurachiAbstract:Regulators of G Protein signaling (RGS) accelerate intrinsic GTP hydrolysis on alpha subunits of trimeric G Proteins and play crucial roles in the physiological regulation of G Protein-mediated cell signaling. The control mechanisms of the action of RGS Proteins per se are poorly clarified, however. We recently showed a physiological mode of action of a RGS Protein in cardiac myocytes. The voltage-dependent formation of Ca2+/calmodulin facilitated the GTPase activity of RGS by an unidentified mechanism, which underlay the "relaxation" behavior of G Protein-gated K+ (K(G)) channels. Here we report the mechanism which is the reversal by Ca2+/calmodulin of phosphatidylinositol-3,4,5,-trisphosphate (PIP3)-mediated inhibition of RGS. Purified RGS4 Protein alone inhibited GTP-induced K(G) channel activity in inside-out patches from atrial myocytes. The inhibitory effect of RGS4 was reduced by PIP3 and restored by addition of Ca2+/calmodulin. The intracellular application of anti-PIP3 antibody abolished the RGS-dependent relaxation behavior of K(G) current in atrial myocytes. This study, therefore, reveals a general physiological control mechanism of RGS Proteins by lipid-Protein interaction.
John R Traynor - One of the best experts on this subject based on the ideXlab platform.
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Opioid-induced Down-Regulation of RGS4 ROLE OF UBIQUITINATION AND IMPLICATIONS FOR RECEPTOR CROSS-TALK
The Journal of biological chemistry, 2011Co-Authors: Qin Wang, John R TraynorAbstract:Regulator of G Protein signaling Protein 4 (RGS4) acts as a GTPase accelerating Protein to modulate μ- and δ- opioid receptor (MOR and DOR, respectively) signaling. In turn, exposure to MOR agonists leads to changes in RGS4 at the mRNA and/or Protein level. Here we have used human neuroblastoma SH-SY5Y cells that endogenously express MOR, DOR, and RGS4 to study opioid-mediated down-regulation of RGS4. Overnight treatment of SH-SY5Y cells with the MOR agonist DAMGO or the DOR agonist DPDPE decreased RGS4 Protein by ∼60% accompanied by a profound loss of opioid receptors but with no change in RGS4 mRNA. The decrease in RGS4 Protein was prevented by the pretreatment with pertussis toxin or the opioid antagonist naloxone. The agonist-induced down-regulation of RGS4 Proteins was completely blocked by treatment with the proteasome inhibitors MG132 or lactacystin or high concentrations of leupeptin, indicating involvement of ubiquitin-proteasome and lysosomal degradation. Polyubiquitinated RGS4 Protein was observed in the presence of MG132 or the specific proteasome inhibitor lactacystin and promoted by opioid agonist. The loss of opioid receptors was not prevented by MG132, demonstrating a different degradation pathway. RGS4 is a GTPase accelerating Protein for both Gα(i/o) and Gα(q) Proteins. After overnight treatment with DAMGO to reduce RGS4 Protein, signaling at the Gα(i/o)-coupled DOR and the Gα(q)-coupled M(3) muscarinic receptor (M(3)R) was increased but not signaling of the α(2) adrenergic receptor or bradykinin BK(2) receptor, suggesting the development of cross-talk between the DOR and M(3)R involving RGS4.
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differential modulation of μ and δ opioid receptor agonists by endogenous RGS4 Protein in sh sy5y cells
Journal of Biological Chemistry, 2009Co-Authors: Qin Wang, Leeyuan Liuchen, John R TraynorAbstract:Regulator of G-Protein signaling (RGS) Proteins are a family of molecules that control the duration of G Protein signaling. A variety of RGS Proteins have been reported to modulate opioid receptor signaling. Here we show that RGS4 is abundantly expressed in human neuroblastoma SH-SY5Y cells that endogenously express μ- and δ-opioid receptors and test the hypothesis that the activity of opioids in these cells is modulated by RGS4. Endogenous RGS4 Protein was reduced by ∼90% in SH-SY5Y cells stably expressing short hairpin RNA specifically targeted to RGS4. In these cells, the potency and maximal effect of δ-opioid receptor agonist (SNC80)-mediated inhibition of forskolin-stimulated cAMP accumulation was increased compared with control cells. This effect was reversed by transient transfection of a stable RGS4 mutant (HA-RGS4C2S). Furthermore, MAPK activation by SNC80 was increased in cells with knockdown of RGS4. In contrast, there was no change in the μ-opioid (morphine) response at adenylyl cyclase or MAPK. FLAG-tagged opioid receptors and HA-RGS4C2S were transiently expressed in HEK293T cells, and co-immunoprecipitation experiments showed that the δ-opioid receptor but not the μ-opioid receptor could be precipitated together with the stable RGS4. Using chimeras of the δ- and μ-opioid receptors, the C-tail and third intracellular domain of the δ-opioid receptor were suggested to be the sites of interaction with RGS4. The findings demonstrate a role for endogenous RGS4 Protein in modulating δ-opioid receptor signaling in SH-SY5Y cells and provide evidence for a receptor-specific effect of RGS4.
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Differential Modulation of μ- and δ-Opioid Receptor Agonists by Endogenous RGS4 Protein in SH-SY5Y Cells
The Journal of biological chemistry, 2009Co-Authors: Qin Wang, Lee-yuan Liu-chen, John R TraynorAbstract:Regulator of G-Protein signaling (RGS) Proteins are a family of molecules that control the duration of G Protein signaling. A variety of RGS Proteins have been reported to modulate opioid receptor signaling. Here we show that RGS4 is abundantly expressed in human neuroblastoma SH-SY5Y cells that endogenously express mu- and delta-opioid receptors and test the hypothesis that the activity of opioids in these cells is modulated by RGS4. Endogenous RGS4 Protein was reduced by approximately 90% in SH-SY5Y cells stably expressing short hairpin RNA specifically targeted to RGS4. In these cells, the potency and maximal effect of delta-opioid receptor agonist (SNC80)-mediated inhibition of forskolin-stimulated cAMP accumulation was increased compared with control cells. This effect was reversed by transient transfection of a stable RGS4 mutant (HA-RGS4C2S). Furthermore, MAPK activation by SNC80 was increased in cells with knockdown of RGS4. In contrast, there was no change in the mu-opioid (morphine) response at adenylyl cyclase or MAPK. FLAG-tagged opioid receptors and HA-RGS4C2S were transiently expressed in HEK293T cells, and co-immunoprecipitation experiments showed that the delta-opioid receptor but not the mu-opioid receptor could be precipitated together with the stable RGS4. Using chimeras of the delta- and mu-opioid receptors, the C-tail and third intracellular domain of the delta-opioid receptor were suggested to be the sites of interaction with RGS4. The findings demonstrate a role for endogenous RGS4 Protein in modulating delta-opioid receptor signaling in SH-SY5Y cells and provide evidence for a receptor-specific effect of RGS4.
Qin Wang - One of the best experts on this subject based on the ideXlab platform.
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Opioid-induced Down-Regulation of RGS4 ROLE OF UBIQUITINATION AND IMPLICATIONS FOR RECEPTOR CROSS-TALK
The Journal of biological chemistry, 2011Co-Authors: Qin Wang, John R TraynorAbstract:Regulator of G Protein signaling Protein 4 (RGS4) acts as a GTPase accelerating Protein to modulate μ- and δ- opioid receptor (MOR and DOR, respectively) signaling. In turn, exposure to MOR agonists leads to changes in RGS4 at the mRNA and/or Protein level. Here we have used human neuroblastoma SH-SY5Y cells that endogenously express MOR, DOR, and RGS4 to study opioid-mediated down-regulation of RGS4. Overnight treatment of SH-SY5Y cells with the MOR agonist DAMGO or the DOR agonist DPDPE decreased RGS4 Protein by ∼60% accompanied by a profound loss of opioid receptors but with no change in RGS4 mRNA. The decrease in RGS4 Protein was prevented by the pretreatment with pertussis toxin or the opioid antagonist naloxone. The agonist-induced down-regulation of RGS4 Proteins was completely blocked by treatment with the proteasome inhibitors MG132 or lactacystin or high concentrations of leupeptin, indicating involvement of ubiquitin-proteasome and lysosomal degradation. Polyubiquitinated RGS4 Protein was observed in the presence of MG132 or the specific proteasome inhibitor lactacystin and promoted by opioid agonist. The loss of opioid receptors was not prevented by MG132, demonstrating a different degradation pathway. RGS4 is a GTPase accelerating Protein for both Gα(i/o) and Gα(q) Proteins. After overnight treatment with DAMGO to reduce RGS4 Protein, signaling at the Gα(i/o)-coupled DOR and the Gα(q)-coupled M(3) muscarinic receptor (M(3)R) was increased but not signaling of the α(2) adrenergic receptor or bradykinin BK(2) receptor, suggesting the development of cross-talk between the DOR and M(3)R involving RGS4.
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differential modulation of μ and δ opioid receptor agonists by endogenous RGS4 Protein in sh sy5y cells
Journal of Biological Chemistry, 2009Co-Authors: Qin Wang, Leeyuan Liuchen, John R TraynorAbstract:Regulator of G-Protein signaling (RGS) Proteins are a family of molecules that control the duration of G Protein signaling. A variety of RGS Proteins have been reported to modulate opioid receptor signaling. Here we show that RGS4 is abundantly expressed in human neuroblastoma SH-SY5Y cells that endogenously express μ- and δ-opioid receptors and test the hypothesis that the activity of opioids in these cells is modulated by RGS4. Endogenous RGS4 Protein was reduced by ∼90% in SH-SY5Y cells stably expressing short hairpin RNA specifically targeted to RGS4. In these cells, the potency and maximal effect of δ-opioid receptor agonist (SNC80)-mediated inhibition of forskolin-stimulated cAMP accumulation was increased compared with control cells. This effect was reversed by transient transfection of a stable RGS4 mutant (HA-RGS4C2S). Furthermore, MAPK activation by SNC80 was increased in cells with knockdown of RGS4. In contrast, there was no change in the μ-opioid (morphine) response at adenylyl cyclase or MAPK. FLAG-tagged opioid receptors and HA-RGS4C2S were transiently expressed in HEK293T cells, and co-immunoprecipitation experiments showed that the δ-opioid receptor but not the μ-opioid receptor could be precipitated together with the stable RGS4. Using chimeras of the δ- and μ-opioid receptors, the C-tail and third intracellular domain of the δ-opioid receptor were suggested to be the sites of interaction with RGS4. The findings demonstrate a role for endogenous RGS4 Protein in modulating δ-opioid receptor signaling in SH-SY5Y cells and provide evidence for a receptor-specific effect of RGS4.
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Differential Modulation of μ- and δ-Opioid Receptor Agonists by Endogenous RGS4 Protein in SH-SY5Y Cells
The Journal of biological chemistry, 2009Co-Authors: Qin Wang, Lee-yuan Liu-chen, John R TraynorAbstract:Regulator of G-Protein signaling (RGS) Proteins are a family of molecules that control the duration of G Protein signaling. A variety of RGS Proteins have been reported to modulate opioid receptor signaling. Here we show that RGS4 is abundantly expressed in human neuroblastoma SH-SY5Y cells that endogenously express mu- and delta-opioid receptors and test the hypothesis that the activity of opioids in these cells is modulated by RGS4. Endogenous RGS4 Protein was reduced by approximately 90% in SH-SY5Y cells stably expressing short hairpin RNA specifically targeted to RGS4. In these cells, the potency and maximal effect of delta-opioid receptor agonist (SNC80)-mediated inhibition of forskolin-stimulated cAMP accumulation was increased compared with control cells. This effect was reversed by transient transfection of a stable RGS4 mutant (HA-RGS4C2S). Furthermore, MAPK activation by SNC80 was increased in cells with knockdown of RGS4. In contrast, there was no change in the mu-opioid (morphine) response at adenylyl cyclase or MAPK. FLAG-tagged opioid receptors and HA-RGS4C2S were transiently expressed in HEK293T cells, and co-immunoprecipitation experiments showed that the delta-opioid receptor but not the mu-opioid receptor could be precipitated together with the stable RGS4. Using chimeras of the delta- and mu-opioid receptors, the C-tail and third intracellular domain of the delta-opioid receptor were suggested to be the sites of interaction with RGS4. The findings demonstrate a role for endogenous RGS4 Protein in modulating delta-opioid receptor signaling in SH-SY5Y cells and provide evidence for a receptor-specific effect of RGS4.
Nancy A Muma - One of the best experts on this subject based on the ideXlab platform.
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Chronic Olanzapine Activates the Stat3 Signal Transduction Pathway and Alters Expression of Components of the 5-HT2A Receptor Signaling System in Rat Frontal Cortex
Neuropharmacology, 2007Co-Authors: Nancy A Muma, Rakesh K. Singh, M.s. Vercillo, D.n. D'souza, B. Zemaitaitis, F. Garcia, K.j. Damjanoska, Y. Zhang, George Battaglia, L.d. Van De KarAbstract:The mechanisms underlying desensitization of serotonin 2A (5-HT(2A)) receptor signaling by antagonists are unclear but may involve changes in gene expression mediated via signal transduction pathways. In cells in culture, olanzapine causes desensitization of 5-HT(2A) receptor signaling and increases the levels of regulators of G Protein signaling (RGS) 7 Protein dependent on phosphorylation/activation of the Janus kinase 2 (Jak2)/signal transducers and activators of transcription 3 (Stat3) signaling pathway. In the current study, the 5-HT(2A) receptor signaling system in rat frontal cortex was examined following 7 days of daily treatment with 0.5, 2.0 or 10.0 mg/kg i.p. olanzapine. Olanzapine increased phosphorylation of Stat3 in rats treated daily with 10 mg/kg olanzapine and caused a dose-dependent desensitization of 5-HT(2A) receptor-mediated phospholipase C activity. There were dose-dependent increases in the levels of membrane-associated 5-HT(2A) receptor, G(alpha11) and G(alphaq) Protein levels but no changes in the G(beta) Protein levels. With olanzapine treatment, RGS4 Protein levels increase in the membrane-fraction and decrease in the cytosolic fraction by similar amounts suggesting a redistribution of RGS4 Protein within neurons. RGS7 Protein levels increase in both the membrane and cytosolic fractions in rats treated daily with 10mg/kg olanzapine. The olanzapine-induced increase in Stat3 activity could underlie the increase in RGS7 Protein expression in vivo as previously demonstrated in cultured cells. Furthermore, the increases in membrane-associated RGS Proteins could play a role in desensitization of signaling by terminating the activated G(alphaq/11) Proteins more rapidly.
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differences in regional and subcellular localization of gq 11 and RGS4 Protein levels in alzheimer s disease correlation with muscarinic m1 receptor binding parameters
Synapse, 2003Co-Authors: Nancy A Muma, Ramesh Mariyappa, Kyle WilliamsAbstract:Deficits in M1 muscarinic receptor system signaling in Alzheimer's disease (AD) prompted an analysis of components of these systems, namely, the Gq/11 Protein and the regulator of G-Protein signaling (RGS) 4 Protein. In AD parietal cortex, total levels of Gq/11 and RGS4 Proteins were significantly lower than age-matched control cases by 40% and 53%, respectively. However, the levels of membrane-bound Gq/11 and RGS4 Protein in AD parietal cortex were maintained at levels comparable to controls. Furthermore, in the frontal cortex and cerebellum both the total and membrane levels of Gq/11 and RGS4 Protein were not altered in AD cases compared to control cases. To our knowledge, this is the first report to examine RGS Proteins in AD. Using receptor binding assays on the parietal cortex membrane fractions from AD cases, we found the muscarinic agonist carbachol still bound to high- and low-affinity sites (two-site fit) and the potency of 5-guanylylimidodiphosphate (GppNHp) to shift receptors from the high- to low-affinity state (based on the ternary complex model) was greater in AD cases compared to controls. In contrast, we previously reported a lack of high-affinity agonist binding sites in the frontal cortex in AD cases even in the absence of GppNHp. The data suggest that the equilibrium dynamics between the cytosolic and membrane levels of Gq/11 and RGS4 may contribute to the regional differences in the coupling of muscarinic M1 receptors in AD and have implications for the variability in effects of cholingeric treatment strategies currently in place. Synapse 47:58–65, 2003. © 2002 Wiley-Liss, Inc.
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Differences in regional and subcellular localization of Gq/11 and RGS4 Protein levels in Alzheimer's disease: Correlation with muscarinic M1 receptor binding parameters
Synapse, 2002Co-Authors: Nancy A Muma, Ramesh Mariyappa, Kyle WilliamsAbstract:Deficits in M1 muscarinic receptor system signaling in Alzheimer's disease (AD) prompted an analysis of components of these systems, namely, the Gq/11 Protein and the regulator of G-Protein signaling (RGS) 4 Protein. In AD parietal cortex, total levels of Gq/11 and RGS4 Proteins were significantly lower than age-matched control cases by 40% and 53%, respectively. However, the levels of membrane-bound Gq/11 and RGS4 Protein in AD parietal cortex were maintained at levels comparable to controls. Furthermore, in the frontal cortex and cerebellum both the total and membrane levels of Gq/11 and RGS4 Protein were not altered in AD cases compared to control cases. To our knowledge, this is the first report to examine RGS Proteins in AD. Using receptor binding assays on the parietal cortex membrane fractions from AD cases, we found the muscarinic agonist carbachol still bound to high- and low-affinity sites (two-site fit) and the potency of 5-guanylylimidodiphosphate (GppNHp) to shift receptors from the high- to low-affinity state (based on the ternary complex model) was greater in AD cases compared to controls. In contrast, we previously reported a lack of high-affinity agonist binding sites in the frontal cortex in AD cases even in the absence of GppNHp. The data suggest that the equilibrium dynamics between the cytosolic and membrane levels of Gq/11 and RGS4 may contribute to the regional differences in the coupling of muscarinic M1 receptors in AD and have implications for the variability in effects of cholingeric treatment strategies currently in place. Synapse 47:58–65, 2003. © 2002 Wiley-Liss, Inc.