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- Levin, Malin, 1973, et al.
(författare)
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The myocardium-protective Gly-49 variant of the beta 1-adrenergic receptor exhibits constitutive activity and increased desensitization and down-regulation.
- 2002
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Ingår i: The Journal of biological chemistry. - 0021-9258. ; 277:34, s. 30429-35
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Tidskriftsartikel (refereegranskat)abstract
- The beta(1)-adrenergic receptor (beta(1)AR) is a major mediator of catecholamine effects in human heart. Patients with heart failure who were hetero- or homozygous for the Gly-49 variant of the beta(1)AR (Gly-49-beta(1)AR) showed improved long-term survival as compared with those with the Ser-49 genotype. Here, the functional consequences of this polymorphism were studied in cells expressing either variant. The Gly-49-beta(1)AR demonstrated characteristic features of constitutively active receptors. In cells expressing the Gly-49-beta(1)AR, both basal and agonist-stimulated adenylyl cyclase activities were higher than in cells expressing the Ser-49 variant (Ser-49-beta(1)AR). The Gly-49-beta(1)AR was more sensitive to the inhibitory effect of the inverse agonist metoprolol and displayed increased affinity for agonists. Isoproterenol potency for adenylyl cyclase activation was higher on membranes expressing the Gly-49-beta(1)AR than on those expressing the Ser-49-beta(1)AR. After incubation with saturating concentrations of catecholamines or sustained stimulation, the Gly-49 variant showed a much higher desensitization, which largely prevailed over constitutive activity in terms of cAMP accumulation. The Gly-49-beta(1)AR also displayed a more profound agonist-promoted down-regulation than the Ser-49 variant. The stronger regulation of the Gly-49-beta(1)AR could explain the beneficial effect of the Gly-49 genotypes on survival, further supporting the concept that beta(1)AR desensitization is protective in heart failure.
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| 2. |
- Scott, Mark G H, et al.
(författare)
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Cooperative regulation of extracellular signal-regulated kinase activation and cell shape change by filamin A and beta-arrestins.
- 2006
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Ingår i: Molecular and cellular biology. - 0270-7306. ; 26:9, s. 3432-45
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Tidskriftsartikel (refereegranskat)abstract
- beta-Arrestins (betaarr) are multifunctional adaptor proteins that can act as scaffolds for G protein-coupled receptor activation of mitogen-activated protein kinases (MAPK). Here, we identify the actin-binding and scaffolding protein filamin A (FLNA) as a betaarr-binding partner using Son of sevenless recruitment system screening, a classical yeast two-hybrid system, coimmunoprecipitation analyses, and direct binding in vitro. In FLNA, the betaarr-binding site involves tandem repeat 22 in the carboxyl terminus. betaarr binds FLNA through both its N- and C-terminal domains, indicating the presence of multiple binding sites. We demonstrate that betaarr and FLNA act cooperatively to activate the MAPK extracellular signal-regulated kinase (ERK) downstream of activated muscarinic M1 (M1MR) and angiotensin II type 1a (AT1AR) receptors and provide experimental evidence indicating that this phenomenon is due to the facilitation of betaarr-ERK2 complex formation by FLNA. In Hep2 cells, stimulation of M1MR or AT1AR results in the colocalization of receptor, betaarr, FLNA, and active ERK in membrane ruffles. Reduction of endogenous levels of betaarr or FLNA and a catalytically inactive dominant negative MEK1, which prevents ERK activation, inhibit membrane ruffle formation, indicating the functional requirement for betaarr, FLNA, and active ERK in this process. Our results indicate that betaarr and FLNA cooperate to regulate ERK activation and actin cytoskeleton reorganization.
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