UMLS:C0043167 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UMLS:C0043167 (pertussis)
19,595 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The alpha2A-adrenoceptor is the prototypic example of the family of G-protein-coupled receptors which function by activation of 'Gi-like' pertussis toxin-sensitive G-proteins. A number of members of this subfamily of G-proteins are often co-expressed in a single cell type. To examine the interaction of this receptor with individual Gi-family G-proteins the porcine alpha2A-adrenoceptor was transiently transfected into COS-7 cells either alone or with each of wild-type Gi1alpha, Gi2alpha and Gi3alpha or mutations of each of these G-proteins in which the cysteine residue which is the target for pertussis toxin-catalysed ADP-ribosylation was exchanged for a glycine residue. The alpha2-adrenoceptor agonist UK14304 stimulated both high-affinity GTPase activity and the binding of guanosine 5'-[gamma-35thio]-triphosphate (GTP[35S]), when expressed without any additional G-protein. These effects were greatly reduced by pretreatment of the cells with pertussis toxin. Co-expression of each of the wild-type Gi-like G-protein alpha-subunits resulted in enhanced agonist activation of the cellular G-protein population which was fully prevented by pretreatment with pertussis toxin. Co-expression of the receptor along with the cysteine-to-glycine mutations of Gi1alpha, Gi2alpha and Gi3alpha resulted in agonist stimulation of these G-proteins, which was as great as that of the wild type proteins, but now the agonist stimulation produced over that due to the activation of endogenously expressed Gi-like G-proteins was resistant to pertussis toxin treatment. The Cys --> Gly mutations of Gi1alpha, Gi2alpha and Gi3alpha were each also able to limit agonist-mediated stimulation of adenylate cyclase activity. The degree of agonist-mediated activation of the pertussis toxin-resistant mutant of Gi1alpha was correlated highly both with the level of expression of this G-protein and with the level of expression of the alpha2A-adrenoceptor. Half-maximal stimulation of high-affinity GTPase activity of the Cys --> Gly mutants of Gi1alpha, Gi2alpha and Gi3alpha required 10-15-fold higher concentrations of agonist than did stimulation of their wild-type counterparts, consistent with a model in which the affinity of functional interactions of the alpha2A-adrenoceptor with the wild-type G-protein is greater than with the pertussis toxin-resistant mutant G-protein.
...
PMID:Interactions of the alpha2A-adrenoceptor with multiple Gi-family G-proteins: studies with pertussis toxin-resistant G-protein mutants. 903 59

Recombinant regulators of G protein-signaling (RGS) proteins stimulate hydrolysis of GTP by alpha subunits of the Gi family but have not been reported to regulate other G protein alpha subunits. Expression of recombinant RGS proteins in cultured cells inhibits Gi-mediated hormonal signals probably by acting as GTPase-activating proteins for Galphai subunits. To ask whether an RGS protein can also regulate cellular responses mediated by G proteins in the Gq/11 family, we compared activation of mitogen-activated protein kinase (MAPK) by a Gq/11-coupled receptor, the bombesin receptor (BR), and a Gi-coupled receptor, the D2 dopamine receptor, transiently co-expressed with or without recombinant RGS4 in COS-7 cells. Pertussis toxin, which uncouples Gi from receptors, blocked MAPK activation by the D2 dopamine receptor but not by the BR. Co-expression of RGS4, however, inhibited activation of MAPK by both receptors causing a rightward shift of the concentration-effect curve for both receptor agonists. RGS4 also inhibited BR-stimulated synthesis of inositol phosphates by an effector target of Gq/11, phospholipase C. Moreover, RGS4 inhibited inositol phosphate synthesis activated by addition of AlF4- to cells overexpressing recombinant alphaq, probably by binding to alphaq.GDP.AlF4-. These results demonstrate that RGS4 can regulate Gq/11-mediated cellular signals by competing for effector binding as well as by acting as a GTPase-activating protein.
...
PMID:RGS4 inhibits Gq-mediated activation of mitogen-activated protein kinase and phosphoinositide synthesis. 911 54

Using transient transfection of COS-7 and human embryonic kidney 293 cells, we studied the functional properties of a previously cloned muscarinic Xenopus receptor [Herrera et al. (1994): FEBS Lett 352:175-179] and its coupling to adenylyl cyclase (AC) and mitogen-activated protein kinase (MAPK) pathways. Expression of the Xenopus muscarinic receptor results in the inhibition of AC activity and activation of the MAPK pathway through a mechanism that involves a Pertussis-toxin-sensitive G-protein and the G beta gamma subunits. The signal transduction properties of this receptor are similar to the mammalian m2 and m4 muscarinic receptors. These results strongly support the idea that inhibition of AC and MAPK activation, signaled out from the muscarinic oocyte receptor, are involved in the oocyte maturation process.
...
PMID:Dual transduction signaling by a Xenopus muscarinic receptor: adenylyl cyclase inhibition and MAP kinase activation. 913 82

Proposed mechanisms by which alpha 2-adrenergic receptors (alpha 2AR) regulate intracellular calcium ([Ca2+]i) include stimulation and inhibition of cell surface calcium channels, stimulation of calcium release via receptor coupling to Gq with subsequent activation of phospholipase C and release of IP3, or stimulation of calcium release via coupling to Gi in an IP3-independent manner. These potential mechanisms were explored in cells that expressed alpha(2A)AR endogenously (HEL cells), permanently transfected CHO cells, and transiently transfected COS-7 cells. Each cell type displayed agonist (UK14304)-dependent increases in [Ca2+]i that were blocked by yohimbine, ablated by pertussis toxin, and largely unaffected by chelation of extracellular calcium. Furthermore, calcium release was associated with IP3 accumulation and was blocked by an inhibitor of phospholipase C (PLC). When expressed in CHO cells, a mutated alpha(2A)AR which has the amino and carboxyl termini of the third intracellular loop substituted with beta 2AR sequence poorly coupled to Gi in adenylyl cyclase assays, and likewise displayed virtually no coupling to increased [Ca2+]i. These results all point toward a Gi- versus a Gq-mediated coupling pathway triggering release of intracellular calcium stores. The possibility that G(beta gamma) subunits released from alpha(2A)AR-Gi coupling is the mechanism of PLC activation was explored in COS-7 cells by coexpressing alpha(2A)AR with the G(beta gamma) inhibitors transducin or a carboxy-terminal portion of the beta AR kinase. Both beta gamma inhibitors markedly inhibited alpha(2A)AR modulation of [Ca2+]i while not affecting thromboxane A2 receptor mediated stimulation of [Ca2+]i via Gq coupling. Thus, alpha(2A)AR couple to calcium release via Gi-associated G(beta gamma) subunits. This coupling is present in multiple cell types and should be considered a major signal transduction pathway of this receptor.
...
PMID:Alpha 2A-adrenergic receptor stimulated calcium release is transduced by Gi-associated G(beta gamma)-mediated activation of phospholipase C. 917 58

Mitogenic G protein-coupled receptors, such as those for lysophosphatidic acid (LPA) and thrombin, activate the Ras/MAP kinase pathway via pertussis toxin (PTX)-sensitive Gi, tyrosine kinase activity and recruitment of Grb2, which targets guanine nucleotide exchange activity to Ras. Little is known about the tyrosine phosphorylations involved, although Src activation and Shc phosphorylation are thought to be critical. We find that agonist-induced Src activation in Rat-1 cells is not mediated by Gi and shows no correlation with Ras/MAP kinase activation. Furthermore, LPA-induced tyrosine phosphorylation of Shc is PTX-insensitive and Ca2+-dependent in COS cells, but undetectable in Rat-1 cells. Expression of dominant-negative Src or Shc does not affect MAP kinase activation by LPA. Thus, Gi-mediated Ras/MAP kinase activation in fibroblasts and COS cells involves neither Src nor Shc. Instead, we detect a 100 kDa tyrosine-phosphorylated protein (p100) that binds to the C-terminal SH3 domain of Grb2 in a strictly Gi- and agonist-dependent manner. Tyrosine kinase inhibitors and wortmannin, a phosphatidylinositol (PI) 3-kinase inhibitor, prevent p100-Grb2 complex formation and MAP kinase activation by LPA. Our results suggest that the p100-Grb2 complex, together with an upstream non-Src tyrosine kinase and PI 3-kinase, couples Gi to Ras/MAP kinase activation, while Src and Shc act in a different pathway.
...
PMID:Gi-mediated activation of the Ras/MAP kinase pathway involves a 100 kDa tyrosine-phosphorylated Grb2 SH3 binding protein, but not Src nor Shc. 921 27

A fusion protein was generated between the porcine alpha2A-adrenoceptor and a pertussis-toxin-insensitive (Cys351-->Gly) variant of the alpha subunit of Gi1alpha by direct in-frame fusion of the N-terminus of the G-protein to the C-terminus of the receptor. The fusion protein could be transiently expressed to high levels in COS-7 cells. Addition of the alpha2-adrenoceptor agonist 5-bromo-N-(4,5-dihydro- 1H-imidazol-2-yl)-6-quinoxalinamine (UK14304) to membranes of pertussis-toxin-treated transfected cells resulted in a concentration-dependent stimulation of high-affinity GTPase activity. Vmax estimations for the GTPase activity demonstrated an induced catalytic-centre activity of 2.0+/-0.2 min-1 for Gi1alpha when the alpha2A-adrenoceptor was maximally stimulated by UK14304 with a Km for GTP of 0.37+/-0.07 microM. Co-expression of excess beta1gamma2 along with the alpha2A-adrenoceptor-Gi1alpha fusion protein resulted in greater maximal UK14304-induced stimulation of high-affinity GTPase activity (2.1+/-0.2-fold) without alteration in agonist EC50. These studies demonstrate the functionality of the fusion construct, its capacity to interact with betagamma complex and its utility in measuring agonist regulation of the catalytic-centre activity of GTP by a receptor-associated G-protein.
...
PMID:Measurement of agonist-induced guanine nucleotide turnover by the G-protein Gi1alpha when constrained within an alpha2A-adrenoceptor-Gi1alpha fusion protein. 922 24

Pertussis toxin-resistant (C351G) and also palmitoylation-negative (C3S/C351G), myristoylation-negative (G2A/C351G) and combined acylation-negative (G2A/C3S/C351G) forms of the G-protein Gi1 alpha were expressed in COS-7 cells along with the porcine alpha 2A-adrenoceptor. G2A/C3S/C351G Gi1 alpha and G2A/C351G Gi1 alpha were largely cytosolic and failed to interact with the agonist-occupied alpha 2A-adrenoceptor in membrane preparations. In contrast, C351G Gi1 alpha was almost entirely particulate and the alpha 2-adrenoceptor agonist UK14304 caused a marked stimulation of its GTPase activity and binding of [35S]GTP gamma S which was not prevented by pertussis toxin treatment of the cells. C3S/C351G Gi1 alpha was present in both the particulate and cytosolic fractions but the GTPase activity of the membrane bound fraction was only slightly activated by the alpha 2A-adrenoceptor. Coexpression of C3S/C351G Gi1 alpha and the alpha 2A-adrenoceptor along with beta 1 and gamma 2 subunits increased the P2 membrane complement of the alpha subunit and increased substantially the ratio of membrane bound to cytosolic protein. However, this also failed to allow marked stimulation of high-affinity GTPase activity by the alpha 2A-adrenoceptor despite the increased proportion of G-protein in the P2 membrane fraction. Despite the low fractional activation of C3S/C351G Gi1 alpha by the alpha 2A-adrenoceptor compared to C351G Gi1 alpha, the palmitoylation-resistant G-protein caused a marked reduction in pertussis toxin-resistant, agonist (UK14304)-mediated stimulation of adenylyl cyclase activity. UK14304 caused the same degree of effect on adenylyl cyclase activity in pertussis toxin-treated cells following transfection of the same amounts of C351G Gi1 alpha and C3S/C351G Gi1 alpha, as both appear to act to sequester beta gamma subunits. By contrast, neither G2A/C351G Gi1 alpha nor G2A/C3S/C351G Gi1 alpha resulted in effective regulation of adenylyl cyclase activity.
...
PMID:A cysteine-3 to serine mutation of the G-protein Gi1 alpha abrogates functional activation by the alpha 2A-adrenoceptor but not interactions with the beta gamma complex. 927 92

COS-7 cells were transiently transfected with human thyrotropin receptor and dog A1 adenosine receptor cDNAs. An A1 agonist, N6-(L-2-phenylisopropyl) adenosine (PIA), which is ineffective alone, enhanced the thyrotropin (TSH)-induced inositol phosphate production, reflecting phospholipase C (PLC) activation, but inhibited the TSH-induced cAMP accumulation, reflecting adenylyl cyclase inhibition. These PIA-induced actions were completely inhibited by pertussis toxin (PTX) treatment. Moreover, in the cells expressing a PTX-insensitive mutant of Gi2alpha or Gi3alpha, in which a glycine residue was substituted for a cysteine residue to be ADP-ribosylated by PTX, at the fourth position of the C terminus, PIA effectively exerted both stimulatory and inhibitory effects on the TSH-induced actions although the cells were treated with the toxin. Overexpression of the betagamma subunits of the G proteins enhanced the TSH-induced inositol phosphate production without any significant effect on the cAMP response; under these conditions, PIA did not further increase the elevated inositol phosphate response to TSH. On the contrary, overexpression of a constitutively active mutant of Gi2alpha, in which the guanosine triphosphatase activity is lost, inhibited the TSH-induced cAMP accumulation but hardly affected the inositol phosphate response; under these conditions, PIA never exerted further inhibitory effects on the cAMP response to TSH. In contrast to the case of the TSH-induced inositol phosphate response, the response to a constitutively active G11alpha mutant was not appreciably affected, and that to NaF was rather inhibited by PIA and overexpression of the betagamma subunits. Taken together, these results suggest that a single type of PTX-sensitive G protein mediates the A1 adenosine receptor-linked modulation of two signaling pathways in collaboration with an activated thyrotropin receptor; alpha subunits of the PTX-sensitive G proteins mediate the inhibitory action on adenylyl cyclase, and the betagamma subunits mediate the stimulatory action on PLC. In the case of the latter stimulatory action on PLC, the betagamma subunits may not directly activate PLC. The possible mechanism by which betagamma subunits enhance the TSH-induced PLC activation is discussed.
...
PMID:Betagamma subunits of pertussis toxin-sensitive G proteins mediate A1 adenosine receptor agonist-induced activation of phospholipase C in collaboration with thyrotropin. A novel stimulatory mechanism through the cross-talk of two types of receptors. 928 15

1 Phosphoinositide-specific phospholipase C (PLC) is involved in the regulation of many cellular functions. In the myocardium, PLC-generated second messengers play a role in the regulation of contractile function and in the pathophysiology of myocardial hypertrophy. 2 In the present study, the effect of mastoparan, a tetradecapeptide which is capable of activating heterotrimeric G proteins by mimicking the action of an activated receptor, on membrane-bound human myocardial PLC, was investigated in a cell-free assay with exogenous phospholipids as a substrate. 3 Mastoparan stimulated human myocardial PLC approximately two fold with a half-maximal effect at approximately 2 microM and a maximal effect at 10 microM. The peptide did not alter the dependence of PLC on free calcium ions. In order to exclude non-specific effects of mastoparan due to its amphiphilic properties, different mastoparan derivatives were used as positive and negative controls. Mas17, an inactive mastoparan analogue with physical properties very similar to mastoparan, did not induce substantial PLC stimulation in human myocardial membranes. In contrast, Mas7, the most active mastoparan derivative known, caused a more pronounced PLC activation compared with the mother compound indicating that the effect was sequence-specific. Human myocardial PLC stimulation was pertussis toxin-insensitive and could not be abolished by addition of excess alpha-subunits from purified retinal transducin or by excess GDP or GDP/beta S. In order to investigate whether mastoparan stimulate PLC via pertussis toxin-insensitive alpha q, a deletion mutant of PLC beta 2 deficient of the site of interaction with alpha q-subunits was expressed in COS-1 cells. Both wild-type and mutant PLC beta 2 were similarly sensitive to stimulation by mastoparan. It is concluded that mastoparan stimulates human myocardial PLC by a mechanism distinct from heterotrimeric G proteins.
...
PMID:G protein-independent stimulation of human myocardial phospholipase C by mastoparan. 929 25

In familial Alzheimer's disease (FAD), three missense mutations, V642I, V642F and V642G, that co-segregate with the disease phenotype have been discovered in the 695 amino acid form of the amyloid precursor protein APP. Expression of these mutants causes a COS cell NK1 clone to undergo pertussis toxin-sensitive apoptosis in an FAD trait-linked manner by activating the G protein Go, which consists of G alpha(o) and G betagamma subunits. We investigated which subunit was responsible for the induction of apoptosis by V642I APP in NK1 cells. In the same system, expression of mutationally activated G alpha(o) or G alpha(i) induced little apoptosis. Apoptosis by V642I APP was antagonized by the overexpression of the carboxy-terminal amino acids 495-689 of the beta-adrenergic receptor kinase-1, which blocks the specific functions of G betagamma. Co-transfection of G beta2gamma2 cDNAs, but not that of other G beta(x)gamma(z) (x = 1-3; z = 2, 3), induced DNA fragmentation in a manner sensitive to bcl-2. These data implicate G betagamma as a cell death mediator for the FAD-associated mutant of APP.
...
PMID:G protein betagamma complex-mediated apoptosis by familial Alzheimer's disease mutant of APP. 930 32

<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>