The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
John H Kehrl - One of the best experts on this subject based on the ideXlab platform.
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variations in gnai2 and RGS1 expression affect chemokine receptor signaling and the organization of secondary lymphoid organs
Genes and Immunity, 2010Co-Authors: Iiyoung Hwang, Ningna Huang, Chung Park, Kathleen Harrision, John H KehrlAbstract:Variations in Gnai2 and RGS1 expression affect chemokine receptor signaling and the organization of secondary lymphoid organs
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RGS1 and RGS13 mrna silencing in a human b lymphoma line enhances responsiveness to chemoattractants and impairs desensitization
Journal of Leukocyte Biology, 2006Co-Authors: Jangil Han, Ningna Huang, Donguk Kim, John H KehrlAbstract:Chemokines bind receptors that are members of the G-protein-coupled receptor family. Chemokine receptors transduce intracellular signals by activating heterotrimeric G-proteins. Acting to limit and modulate heterotrimeric G-protein signaling is a family of proteins, termed regulator of G-protein signaling (RGS). Two of these proteins, RGS1 and RGS13, are well-expressed in germinal center B cells and many Burkitt's lymphoma cell lines. Reducing RGS13 and to a lesser extent RGS1 expression in a Burkitt's lymphoma cell line enhances responsiveness to two chemokines, CXC chemokine ligand 12 (CXCL12) and CXCL13, and reducing both mRNAs augments the responses more dramatically. The double knock-down (KD) cells respond better to restimulation with CXCL12 or CXCL13 after a primary stimulation with CXCL12 than do the control cells. The double-KD cells also exhibit a greater propensity to polarize and to develop multiple small lamellipodia. These results indicate that RGS1 and RGS13 act together to regulate chemokine receptor signaling in human germinal center B lymphocytes and provide evidence that they contribute significantly to the rapid desensitization of the signaling pathway.
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RGS1 and gnai2 regulate the entrance of b lymphocytes into lymph nodes and b cell motility within lymph node follicles
Immunity, 2005Co-Authors: Sangbae Han, Chantal Moratz, Chongshan Shi, Ningna Huang, Brian L Kelsall, Hyeseon Cho, Owen Schwartz, John H KehrlAbstract:Signaling by G protein-coupled receptors coupled to Galpha(i) assists in triggering lymphocyte movement into and out of lymph nodes. Here, we show that modulating the signaling output from these receptors dramatically alters B cell trafficking. Intravital microscopy of adoptively transferred B cells from wild-type and RGS1-/- mice revealed that RGS1-/- B cells stick better to lymph node high endothelial venules, home better to lymph nodes, and move more rapidly within lymph node follicles than do wild-type B cells. In contrast, B cells from Gnai2-/- mice enter lymph nodes poorly and move more slowly than do wild-type B cells. The Gnai2-/- mice often lack multiple peripheral lymph nodes, and their B cells respond poorly to chemokines, indicating that Galpha(i1) and Galpha(i3) poorly compensate for the loss of Galpha(i2). These results demonstrate opposing roles for RGS1 and Gnai2 in B cell trafficking into and within lymph nodes.
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abnormal b cell responses to chemokines disturbed plasma cell localization and distorted immune tissue architecture in RGS1 mice
Molecular and Cellular Biology, 2004Co-Authors: Chantal Moratz, Russell J Hayman, John H KehrlAbstract:The migration of developing lymphocytes into lymphoid tissues, the recirculation of lymphocytes, as well as organization of secondary immune structures such as lymphoid follicles results from a regulated configuration of cell surface adhesion molecules and chemoattractant receptors as well as a spatial overlay of multiple chemoattractant gradients (1, 23, 29, 32). Mechanisms that allow a cell, such as a B-lymphocyte, to interrupt, modify, and prioritize signals from such a milieu of stimuli are essential for efficient and normal immune function. Inappropriate interpretations by cells within such a complex environment is deleterious, leading to inappropriate trafficking, survival, and activation of cells (10, 12, 28, 37). Previous work has detailed B-cell migratory patterns following antigen challenge, including the establishment of germinal centers; cycling within germinal centers; the exiting of memory and antibody-secreting B cells (ASCs) from germinal centers; and the trafficking of ASCs to bone marrow, lamina propria, and other mucosal sites (5, 16, 22, 27, 30, 42, 45). Much of this work has focused on chemokines and their receptors and upon adhesion molecules, while less is known about the signaling mechanisms that allow B cells to efficiently negotiate the complex chemokine gradients likely present in tissues. Most chemoattracant receptors and all chemokine receptors couple to heterotrimeric G-proteins (1). Activated receptors trigger Gα subunits to exchange GTP for GDP, which dissociates the Gα subunit from βγ heterodimers, leading to the activation of downstream effectors. However, Gα subunits possess an intrinsic GTPase activity that limits the duration of their remaining GTP bound. GTP hydrolysis allows the heterotrimer to reform, and signaling ceases (18, 35). Also limiting the duration of Gα subunits' remaining GTP bound, members of the regulator of G protein signaling (RGS) protein family dramatically increase the intrinsic Gα GTPase activity, a property that defines them as GTPase activating proteins (GAPs). Genetic studies in Saccharomyces cerevisiae, Caenorhabditis elegans, and Aspergillus nidulans first identified such proteins (7, 21, 25). Independently, a mammalian protein termed GAIP was discovered to interact with a Gα subunit (6) and four mammalian proteins designated RGS1, RGS2, RGS3, and RGS4 substituted to various degrees for Sst2p, a yeast protein involved in the desensitization of pheromone signaling (9). Approximately 25 human RGS proteins have now been identified. When tested in standard in vitro GAP assays, most RGS proteins possess GAP activity for the α subunits of the Gi and Gq subfamilies (3, 19, 44). Since chemokine receptors use Gi and perhaps Gq to transduce intracellular signals, the presence of an RGS protein in target cells could substantially alter the response to chemokine stimulation (20). B-lymphocytes, especially following B-cell activation through their antigen receptors, express RGS1. Consistent with a role for RGS1 in regulating the B-cell responses to chemokines, the expression of RGS1 in B-cell lines dramatically impairs their migratory response to CXCL12 and CXCL13 (4, 33, 38). Because the normal trafficking of B cells depends upon the ligand receptor pairs CXCL12-CXCR4 (34, 46) and CXCL13-CXCR5 (11, 15, 26), a deficiency of RGS1 in vivo could alter B-cell development and/or the organization of B cells in lymphoid tissues. To test that possibility we generated RGS1−/− mice.
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RGS13 regulates germinal center b lymphocytes responsiveness to cxc chemokine ligand cxcl 12 and cxcl13
Journal of Immunology, 2002Co-Authors: Gengxian Shi, Chantal Moratz, Kathleen Harrison, Gaye Lynn Wilson, John H KehrlAbstract:Normal lymphoid tissue development and function depend upon directed cell migration. Providing guideposts for cell movement and positioning within lymphoid tissues, chemokines signal through cell surface receptors that couple to heterotrimeric G proteins, which are in turn subject to regulation by regulator of G protein signaling (RGS) proteins. In this study, we report that germinal center B lymphocytes and thymic epithelial cells strongly express one of the RGS family members, RGS13. Located between RGS1 and Rgs2, RGS13 spans 42 kb on mouse chromosome 1. RGS13 encodes a 157-aa protein that shares 82% amino acid identity with its 159-aa human counterpart. In situ hybridization with sense and antisense probes localized RGS13 expression to the germinal center regions of mouse spleens and Peyer's patches and to the thymus medulla. Affinity-purified RGS13 Abs detected RGS13-expressing cells in the light zone of the germinal center. RGS13 interacted with both Gialpha and Gqalpha and strongly impaired signaling through G(i)-linked signaling pathways, including signaling through the chemokine receptors CXCR4 and CXCR5. Prolonged CD40 signaling up-regulated RGS13 expression in human tonsil B lymphocytes. These results plus previous studies of RGS1 indicate the germinal center B cells use two RGS proteins, RGS1 and RGS13, to regulate their responsiveness to chemokines.
Kirk M Druey - One of the best experts on this subject based on the ideXlab platform.
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R4 Regulator of G Protein Signaling (RGS) Proteins in Inflammation and Immunity
The AAPS Journal, 2016Co-Authors: Eunice C. Chan, Kirk M DrueyAbstract:G protein-coupled receptors (GPCRs) have important functions in both innate and adaptive immunity, with the capacity to bridge interactions between the two arms of the host responses to pathogens through direct recognition of secreted microbial products or the by-products of host cells damaged by pathogen exposure. In the mid-1990s, a large group of intracellular proteins was discovered, the regulator of G protein signaling (RGS) family, whose main, but not exclusive, function appears to be to constrain the intensity and duration of GPCR signaling. The R4/B subfamily—the focus of this review—includes RGS1–5, 8, 13, 16, 18, and 21, which are the smallest RGS proteins in size, with the exception of RGS3. Prominent roles in the trafficking of B and T lymphocytes and macrophages have been described for RGS1, RGS13, and RGS16, while RGS18 appears to control platelet and osteoclast functions. Additional G protein independent functions of RGS13 have been uncovered in gene expression in B lymphocytes and mast cell-mediated allergic reactions. In this review, we discuss potential physiological roles of this RGS protein subfamily, primarily in leukocytes having central roles in immune and inflammatory responses. We also discuss approaches to target RGS proteins therapeutically, which represents a virtually untapped strategy to combat exaggerated immune responses leading to inflammation.
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rgs4 and rgs2 bind coatomer and inhibit copi association with golgi membranes and intracellular transport
Molecular Biology of the Cell, 2000Co-Authors: Brandon M Sullivan, Kimberly J Harrisonlavoie, John H Kehrl, Vladimir Marshansky, Dennis A. Ausiello, Dennis Brown, Kirk M DrueyAbstract:COPI, a protein complex consisting of coatomer and the small GTPase ARF1, is an integral component of some intracellular transport carriers. The association of COPI with secretory membranes has been implicated in the maintenance of Golgi integrity and the normal functioning of intracellular transport in eukaryotes. The regulator of G protein signaling, RGS4, interacted with the COPI subunit β′-COP in a yeast two-hybrid screen. Both recombinant RGS4 and RGS2 bound purified recombinant β′-COP in vitro. Endogenous cytosolic RGS4 from NG108 cells and RGS2 from HEK293T cells cofractionated with the COPI complex by gel filtration. Binding of β′-COP to RGS4 occurred through two dilysine motifs in RGS4, similar to those contained in some aminoglycoside antibiotics that are known to bind coatomer. RGS4 inhibited COPI binding to Golgi membranes independently of its GTPase-accelerating activity on Giα. In RGS4-transfected LLC-PK1 cells, the amount of COPI in the Golgi region was considerably reduced compared with that in wild-type cells, but there was no detectable difference in the amount of either Golgi-associated ARF1 or the integral Golgi membrane protein giantin, indicating that Golgi integrity was preserved. In addition, RGS4 expression inhibited trafficking of aquaporin 1 to the plasma membrane in LLC-PK1 cells and impaired secretion of placental alkaline phosphatase from HEK293T cells. The inhibitory effect of RGS4 in these assays was independent of GTPase-accelerating activity but correlated with its ability to bind COPI. Thus, these data support the hypothesis that these RGS proteins sequester coatomer in the cytoplasm and inhibit its recruitment onto Golgi membranes, which may in turn modulate Golgi–plasma membrane or intra-Golgi transport.
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regulator of g protein signaling 1 RGS1 markedly impairs giα signaling responses of b lymphocytes
Journal of Immunology, 2000Co-Authors: Chantal Moratz, Kirk M Druey, Astrid Scheschonka, Tohru Kozasa, Veronica H Kang, Chongshan Shi, Philip M Murphy, John H KehrlAbstract:Regulator of G protein signaling (RGS) proteins modulate signaling through pathways that use heterotrimeric G proteins as transducing elements. RGS1 is expressed at high levels in certain B cell lines and can be induced in normal B cells by treatment with TNF-α. To determine the signaling pathways that RGS1 may regulate, we examined the specificity of RGS1 for various Gα subunits and assessed its effect on chemokine signaling. G protein binding and GTPase assays revealed that RGS1 is a Giα and Gqα GTPase-activating protein and a potential G12α effector antagonist. Functional studies demonstrated that RGS1 impairs platelet activating factor-mediated increases in intracellular Ca+2, stromal-derived factor-1-induced cell migration, and the induction of downstream signaling by a constitutively active form of G12α. Furthermore, germinal center B lymphocytes, which are refractory to stromal-derived factor-1-triggered migration, express high levels of RGS1. These results indicate that RGS proteins can profoundly effect the directed migration of lymphoid cells.
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regulation of chemotactic and proadhesive responses to chemoattractant receptors by rgs regulator of g protein signaling family members
Journal of Biological Chemistry, 1998Co-Authors: Edward P Bowman, John H Kehrl, Kirk M Druey, James J Campbell, Astrid Scheschonka, Eugene C ButcherAbstract:Serpentine Galphai-linked receptors support rapid adhesion and directed migration of leukocytes and other cell types. The intracellular mechanisms mediating and regulating chemoattractant-directed adhesion and locomotion are only now beginning to be explored. RGS (for regulator of G-protein signaling) proteins are a recently described family that regulate Galphai-stimulated pathways by acting as GTPase-activating proteins. Little is known about the GTPase activity of the Galphai proteins involved in adhesion and chemotaxis, or the significance of their regulation to these responses. Using transiently transfected lymphoid cells as a model system, we show that expression of RGS1, RGS3, and RGS4 inhibits chemoattractant-induced migration. In contrast, RGS2, a regulator of Galphaq activity, had no effect on cell migration to any chemoattractant. RGS1, RGS3, and RGS4 also reduced rapid chemoattractant-triggered adhesion, although the proadhesive response appears quantitatively less sensitive to RGS action than chemotaxis. The results suggest that the duration of the Galphai signal may be a particularly important parameter in the chemotactic responses of leukocytes, and demonstrate the potential for RGS family members to regulate cellular adhesive and migratory behaviors.
Chantal Moratz - One of the best experts on this subject based on the ideXlab platform.
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RGS1 and gnai2 regulate the entrance of b lymphocytes into lymph nodes and b cell motility within lymph node follicles
Immunity, 2005Co-Authors: Sangbae Han, Chantal Moratz, Chongshan Shi, Ningna Huang, Brian L Kelsall, Hyeseon Cho, Owen Schwartz, John H KehrlAbstract:Signaling by G protein-coupled receptors coupled to Galpha(i) assists in triggering lymphocyte movement into and out of lymph nodes. Here, we show that modulating the signaling output from these receptors dramatically alters B cell trafficking. Intravital microscopy of adoptively transferred B cells from wild-type and RGS1-/- mice revealed that RGS1-/- B cells stick better to lymph node high endothelial venules, home better to lymph nodes, and move more rapidly within lymph node follicles than do wild-type B cells. In contrast, B cells from Gnai2-/- mice enter lymph nodes poorly and move more slowly than do wild-type B cells. The Gnai2-/- mice often lack multiple peripheral lymph nodes, and their B cells respond poorly to chemokines, indicating that Galpha(i1) and Galpha(i3) poorly compensate for the loss of Galpha(i2). These results demonstrate opposing roles for RGS1 and Gnai2 in B cell trafficking into and within lymph nodes.
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abnormal b cell responses to chemokines disturbed plasma cell localization and distorted immune tissue architecture in RGS1 mice
Molecular and Cellular Biology, 2004Co-Authors: Chantal Moratz, Russell J Hayman, John H KehrlAbstract:The migration of developing lymphocytes into lymphoid tissues, the recirculation of lymphocytes, as well as organization of secondary immune structures such as lymphoid follicles results from a regulated configuration of cell surface adhesion molecules and chemoattractant receptors as well as a spatial overlay of multiple chemoattractant gradients (1, 23, 29, 32). Mechanisms that allow a cell, such as a B-lymphocyte, to interrupt, modify, and prioritize signals from such a milieu of stimuli are essential for efficient and normal immune function. Inappropriate interpretations by cells within such a complex environment is deleterious, leading to inappropriate trafficking, survival, and activation of cells (10, 12, 28, 37). Previous work has detailed B-cell migratory patterns following antigen challenge, including the establishment of germinal centers; cycling within germinal centers; the exiting of memory and antibody-secreting B cells (ASCs) from germinal centers; and the trafficking of ASCs to bone marrow, lamina propria, and other mucosal sites (5, 16, 22, 27, 30, 42, 45). Much of this work has focused on chemokines and their receptors and upon adhesion molecules, while less is known about the signaling mechanisms that allow B cells to efficiently negotiate the complex chemokine gradients likely present in tissues. Most chemoattracant receptors and all chemokine receptors couple to heterotrimeric G-proteins (1). Activated receptors trigger Gα subunits to exchange GTP for GDP, which dissociates the Gα subunit from βγ heterodimers, leading to the activation of downstream effectors. However, Gα subunits possess an intrinsic GTPase activity that limits the duration of their remaining GTP bound. GTP hydrolysis allows the heterotrimer to reform, and signaling ceases (18, 35). Also limiting the duration of Gα subunits' remaining GTP bound, members of the regulator of G protein signaling (RGS) protein family dramatically increase the intrinsic Gα GTPase activity, a property that defines them as GTPase activating proteins (GAPs). Genetic studies in Saccharomyces cerevisiae, Caenorhabditis elegans, and Aspergillus nidulans first identified such proteins (7, 21, 25). Independently, a mammalian protein termed GAIP was discovered to interact with a Gα subunit (6) and four mammalian proteins designated RGS1, RGS2, RGS3, and RGS4 substituted to various degrees for Sst2p, a yeast protein involved in the desensitization of pheromone signaling (9). Approximately 25 human RGS proteins have now been identified. When tested in standard in vitro GAP assays, most RGS proteins possess GAP activity for the α subunits of the Gi and Gq subfamilies (3, 19, 44). Since chemokine receptors use Gi and perhaps Gq to transduce intracellular signals, the presence of an RGS protein in target cells could substantially alter the response to chemokine stimulation (20). B-lymphocytes, especially following B-cell activation through their antigen receptors, express RGS1. Consistent with a role for RGS1 in regulating the B-cell responses to chemokines, the expression of RGS1 in B-cell lines dramatically impairs their migratory response to CXCL12 and CXCL13 (4, 33, 38). Because the normal trafficking of B cells depends upon the ligand receptor pairs CXCL12-CXCR4 (34, 46) and CXCL13-CXCR5 (11, 15, 26), a deficiency of RGS1 in vivo could alter B-cell development and/or the organization of B cells in lymphoid tissues. To test that possibility we generated RGS1−/− mice.
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RGS13 regulates germinal center b lymphocytes responsiveness to cxc chemokine ligand cxcl 12 and cxcl13
Journal of Immunology, 2002Co-Authors: Gengxian Shi, Chantal Moratz, Kathleen Harrison, Gaye Lynn Wilson, John H KehrlAbstract:Normal lymphoid tissue development and function depend upon directed cell migration. Providing guideposts for cell movement and positioning within lymphoid tissues, chemokines signal through cell surface receptors that couple to heterotrimeric G proteins, which are in turn subject to regulation by regulator of G protein signaling (RGS) proteins. In this study, we report that germinal center B lymphocytes and thymic epithelial cells strongly express one of the RGS family members, RGS13. Located between RGS1 and Rgs2, RGS13 spans 42 kb on mouse chromosome 1. RGS13 encodes a 157-aa protein that shares 82% amino acid identity with its 159-aa human counterpart. In situ hybridization with sense and antisense probes localized RGS13 expression to the germinal center regions of mouse spleens and Peyer's patches and to the thymus medulla. Affinity-purified RGS13 Abs detected RGS13-expressing cells in the light zone of the germinal center. RGS13 interacted with both Gialpha and Gqalpha and strongly impaired signaling through G(i)-linked signaling pathways, including signaling through the chemokine receptors CXCR4 and CXCR5. Prolonged CD40 signaling up-regulated RGS13 expression in human tonsil B lymphocytes. These results plus previous studies of RGS1 indicate the germinal center B cells use two RGS proteins, RGS1 and RGS13, to regulate their responsiveness to chemokines.
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regulator of g protein signaling 1 RGS1 markedly impairs giα signaling responses of b lymphocytes
Journal of Immunology, 2000Co-Authors: Chantal Moratz, Kirk M Druey, Astrid Scheschonka, Tohru Kozasa, Veronica H Kang, Chongshan Shi, Philip M Murphy, John H KehrlAbstract:Regulator of G protein signaling (RGS) proteins modulate signaling through pathways that use heterotrimeric G proteins as transducing elements. RGS1 is expressed at high levels in certain B cell lines and can be induced in normal B cells by treatment with TNF-α. To determine the signaling pathways that RGS1 may regulate, we examined the specificity of RGS1 for various Gα subunits and assessed its effect on chemokine signaling. G protein binding and GTPase assays revealed that RGS1 is a Giα and Gqα GTPase-activating protein and a potential G12α effector antagonist. Functional studies demonstrated that RGS1 impairs platelet activating factor-mediated increases in intracellular Ca+2, stromal-derived factor-1-induced cell migration, and the induction of downstream signaling by a constitutively active form of G12α. Furthermore, germinal center B lymphocytes, which are refractory to stromal-derived factor-1-triggered migration, express high levels of RGS1. These results indicate that RGS proteins can profoundly effect the directed migration of lymphoid cells.
Shelley B Hooks - One of the best experts on this subject based on the ideXlab platform.
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regulators of g protein signaling RGS10 and RGS17 regulate chemoresistance in ovarian cancer cells
Molecular Cancer, 2010Co-Authors: Shelley B Hooks, Phillip Callihan, Molly K Altman, Jillian H Hurst, Mandi M. MurphAbstract:A critical therapeutic challenge in epithelial ovarian carcinoma is the development of chemoresistance among tumor cells following exposure to first line chemotherapeutics. The molecular and genetic changes that drive the development of chemoresistance are unknown, and this lack of mechanistic insight is a major obstacle in preventing and predicting the occurrence of refractory disease. We have recently shown that Regulators of G-protein Signaling (RGS) proteins negatively regulate signaling by lysophosphatidic acid (LPA), a growth factor elevated in malignant ascites fluid that triggers oncogenic growth and survival signaling in ovarian cancer cells. The goal of this study was to determine the role of RGS protein expression in ovarian cancer chemoresistance. In this study, we find that RGS2, RGS5, RGS10 and RGS17 transcripts are expressed at significantly lower levels in cells resistant to chemotherapy compared with parental, chemo-sensitive cells in gene expression datasets of multiple models of chemoresistance. Further, exposure of SKOV-3 cells to cytotoxic chemotherapy causes acute, persistent downregulation of RGS10 and RGS17 transcript expression. Direct inhibition of RGS10 or RGS17 expression using siRNA knock-down significantly reduces chemotherapy-induced cell toxicity. The effects of cisplatin, vincristine, and docetaxel are inhibited following RGS10 and RGS17 knock-down in cell viability assays and phosphatidyl serine externalization assays in SKOV-3 cells and MDR-HeyA8 cells. We further show that AKT activation is higher following RGS10 knock-down and RGS 10 and RGS17 overexpression blocked LPA mediated activation of AKT, suggesting that RGS proteins may blunt AKT survival pathways. Taken together, our data suggest that chemotherapy exposure triggers loss of RGS10 and RGS17 expression in ovarian cancer cells, and that loss of expression contributes to the development of chemoresistance, possibly through amplification of endogenous AKT signals. Our results establish RGS10 and RGS17 as novel regulators of cell survival and chemoresistance in ovarian cancer cells and suggest that their reduced expression may be diagnostic of chemoresistance.
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RGS6, RGS7, RGS9, and RGS11 stimulate GTPase activity of Gi family G-proteins with differential selectivity and maximal activity.
The Journal of biological chemistry, 2003Co-Authors: Shelley B Hooks, Andrejs M Krumins, G L Waldo, James Corbitt, Erik T. Bodor, T. Kendall HardenAbstract:Abstract Regulator of G-protein signaling (RGS) proteins are GTPase activating proteins (GAPs) of heterotrimeric G-proteins that alter the amplitude and kinetics of receptor-promoted signaling. In this study we defined the G-protein α-subunit selectivity of purified Sf9 cell-derived R7 proteins, a subfamily of RGS proteins (RGS6, -7, -9, and -11) containing a Gγ-like (GGL) domain that mediates dimeric interaction with Gβ5. Gβ5/R7 dimers stimulated steady state GTPase activity of Gα-subunits of the Gi family, but not of Gαq or Gα11, when added to proteoliposomes containing M2 or M1 muscarinic receptor-coupled G-protein heterotrimers. Concentration effect curves of the Gβ5/R7 proteins revealed differences in potencies and efficacies toward Gα-subunits of the Gi family. Although all four Gβ5/R7 proteins exhibited similar potencies toward Gαo, Gβ5/RGS9 and Gβ5/RGS11 were more potent GAPs of Gαi1, Gαi2, and Gαi3 than were Gβ5/RGS6 and Gβ5/RGS7. The maximal GAP activity exhibited by Gβ5/RGS11 was 2- to 4-fold higher than that of Gβ5/RGS7 and Gβ5/RGS9, with Gβ5/RGS6 exhibiting an intermediate maximal GAP activity. Moreover, the less efficacious Gβ5/RGS7 and Gβ5/RGS9 inhibited Gβ5/RGS11-stimulated GTPase activity of Gαo. Therefore, R7 family RGS proteins are Gi family-selective GAPs with potentially important differences in activities.
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RGS6, RGS7, RGS9, and RGS11 stimulate GTPase activity of Gi family G-proteins with differential selectivity and maximal activity.
The Journal of biological chemistry, 2003Co-Authors: Shelley B Hooks, Andrejs M Krumins, G L Waldo, James Corbitt, Erik T. Bodor, T. Kendall HardenAbstract:Regulator of G-protein signaling (RGS) proteins are GTPase activating proteins (GAPs) of heterotrimeric G-proteins that alter the amplitude and kinetics of receptor-promoted signaling. In this study we defined the G-protein alpha-subunit selectivity of purified Sf9 cell-derived R7 proteins, a subfamily of RGS proteins (RGS6, -7, -9, and -11) containing a Ggamma-like (GGL) domain that mediates dimeric interaction with Gbeta(5). Gbeta(5)/R7 dimers stimulated steady state GTPase activity of Galpha-subunits of the G(i) family, but not of Galpha(q) or Galpha(11), when added to proteoliposomes containing M2 or M1 muscarinic receptor-coupled G-protein heterotrimers. Concentration effect curves of the Gbeta(5)/R7 proteins revealed differences in potencies and efficacies toward Galpha-subunits of the G(i) family. Although all four Gbeta(5)/R7 proteins exhibited similar potencies toward Galpha(o), Gbeta(5)/RGS9 and Gbeta(5)/RGS11 were more potent GAPs of Galpha(i1), Galpha(i2), and Galpha(i3) than were Gbeta(5)/RGS6 and Gbeta(5)/RGS7. The maximal GAP activity exhibited by Gbeta(5)/RGS11 was 2- to 4-fold higher than that of Gbeta(5)/RGS7 and Gbeta(5)/RGS9, with Gbeta(5)/RGS6 exhibiting an intermediate maximal GAP activity. Moreover, the less efficacious Gbeta(5)/RGS7 and Gbeta(5)/RGS9 inhibited Gbeta(5)/RGS11-stimulated GTPase activity of Galpha(o). Therefore, R7 family RGS proteins are G(i) family-selective GAPs with potentially important differences in activities.
Thomas M Wilkie - One of the best experts on this subject based on the ideXlab platform.
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RGS16 and Rgs8 in embryonic endocrine pancreas and mouse models of diabetes
Disease models & mechanisms, 2010Co-Authors: Alethia Villasenor, Ozhan Ocal, Rolf A. Brekken, Lee B. Rivera, Zhao V. Wang, Ingrid Wernstedt Asterholm, Philipp E. Scherer, Ondine Cleaver, Thomas M WilkieAbstract:SUMMARY Diabetes is characterized by the loss, or gradual dysfunction, of insulin-producing pancreatic β-cells. Although β-cells can replicate in younger adults, the available diabetes therapies do not specifically target β-cell regeneration. Novel approaches are needed to discover new therapeutics and to understand the contributions of endocrine progenitors and β-cell regeneration during islet expansion. Here, we show that the regulators of G protein signaling RGS16 and Rgs8 are expressed in pancreatic progenitor and endocrine cells during development, then extinguished in adults, but reactivated in models of both type 1 and type 2 diabetes. Exendin-4, a glucagon-like peptide 1 (Glp-1)/incretin mimetic that stimulates β-cell expansion, insulin secretion and normalization of blood glucose levels in diabetics, also promoted re-expression of RGS16::GFP within a few days in pancreatic ductal-associated cells and islet β-cells. These findings show that RGS16::GFP and Rgs8::GFP are novel and early reporters of G protein-coupled receptor (GPCR)-stimulated β-cell expansion after therapeutic treatment and in diabetes models. RGS16 and Rgs8 are likely to control aspects of islet progenitor cell activation, differentiation and β-cell expansion in embryos and metabolically stressed adults.
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differentially regulated expression of endogenous rgs4 and rgs7
Journal of Biological Chemistry, 2004Co-Authors: Andrejs M Krumins, Sheryll A Barker, Kan Yu, Thomas M Wilkie, Stephen J Gold, Chunfa Huang, Roger K. Sunahara, Susanne M MumbyAbstract:Regulators of G protein signaling (RGS proteins) constitute a family of newly appreciated components of G protein-mediated signal transduction. With few exceptions, most information available on mammalian RGS proteins was gained by transfection/overexpression or in vitro experiments, with relatively little known about the endogenous counterparts. Transfection studies, typically of tagged RGS proteins, have been conducted to overcome the low natural abundance of endogenous RGS proteins. Because transfection studies can lead to imprecise or erroneous conclusions, we have developed antibodies of high specificity and sensitivity to focus study on endogenous proteins. Expression of both RGS4 and RGS7 was detected in rat brain tissue and cultured PC12 and AtT-20 cells. Endogenous RGS4 presented as a single 27–28-kDa protein. By contrast, cultured cells transfected with a plasmid encoding RGS4 expressed two observable forms of the protein, apparently due to utilization of distinct sites of initiation of protein synthesis. Subcellular localization of endogenous RGS4 revealed predominant association with membrane fractions, rather than in cytosolic fractions, where most heterologously expressed RGS4 has been found. Endogenous levels of RGS7 exceeded RGS4 by 30 – 40-fold, and studies of cultured cells revealed regulatory differences between the two proteins. We observed that RGS4 mRNA and protein were concomitantly augmented with increased cell density and decreased by exposure of PC12M cells to nerve growth factor, whereas RGS7 was unaffected. Endogenous RGS7 was relatively stable, whereas proteolysis of endogenous RGS4 was a strong determinant of its lower level expression and short halflife. Although we searched without finding evidence for regulation of RGS4 proteolysis, the possibility remains that alterations in the degradation of this protein could provide a means to promptly alter patterns of signal transduction. G proteins transduce signals across the plasma membrane by sequential interactions with cell surface receptors and appropriate second messenger-producing effectors (e.g. enzymes and ion channels). These interactions are modulated by nucleotide-driven conformational changes in the subunits of heterotrimeric G proteins (G). 1 A ligand-bound receptor catalyzes the exchange of GDP for GTP on its cognate G and the dissociation of G from the complex of G protein and subunits (G). These dissociated subunits are competent to modulate the activity of effectors. The duration of G protein-mediated responses are dependent on the intrinsic GTPase rate of G and on extrinsic factors, such as regulators of G protein signaling (RGS proteins).