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Robert J. Lefkowitz

Bio: Robert J. Lefkowitz is an academic researcher from Howard Hughes Medical Institute. The author has contributed to research in topics: Receptor & G protein-coupled receptor. The author has an hindex of 214, co-authored 860 publications receiving 147995 citations. Previous affiliations of Robert J. Lefkowitz include University of Nice Sophia Antipolis & University of Stuttgart.


Papers
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Journal ArticleDOI
TL;DR: A prospective, large library virtual screen against an activated β2-adrenergic receptor (β2AR) structure returned potent agonists to the exclusion of inverse-agonists, providing the first complement to the previous virtual screening campaigns against inverse-agonist-bound G protein coupled receptor (GPCR) structures.
Abstract: A prospective, large library virtual screen against an activated β2-adrenergic receptor (β2AR) structure returned potent agonists to the exclusion of inverse-agonists, providing the first complement to the previous virtual screening campaigns against inverse-agonist-bound G protein coupled receptor (GPCR) structures, which predicted only inverse-agonists. In addition, two hits recapitulated the signaling profile of the co-crystal ligand with respect to the G protein and arrestin mediated signaling. This functional fidelity has important implications in drug design, as the ability to predict ligands with predefined signaling properties is highly desirable. However, the agonist-bound state provides an uncertain template for modeling the activated conformation of other GPCRs, as a dopamine D2 receptor (DRD2) activated model templated on the activated β2AR structure returned few hits of only marginal potency.

100 citations

Journal ArticleDOI
TL;DR: It is reported here that brief exposure of wild type S49 lymphoma cells to somatostatin promotes the translocation of beta AR kinase to an extent comparable to that observed in the presence of the beta agonist isoproterenol or prostaglandin E1, thus emerging as a general kinase that regulates the function of different receptors in an agonist-specific fashion.

100 citations

Journal ArticleDOI
TL;DR: Heterotrimeric G proteins may represent a previously unappreciated class of potential substrates for pp60c-src and G proteins with functional consequences, and are explored in this study.
Abstract: A number of lines of evidence suggest that cross-talk exists between the cellular signal transduction pathways involving tyrosine phosphorylation catalyzed by members of the pp60c-src kinase family and those mediated by guanine nucleotide regulatory proteins (G proteins). In this study, we explore the possibility that direct interactions between pp60c-src and G proteins may occur with functional consequences. Preparations of pp60c-src isolated by immunoprecipitation phosphorylate on tyrosine residues the purified G-protein alpha subunits (G alpha) of several heterotrimeric G proteins. Phosphorylation is highly dependent on G-protein conformation, and G alpha(GDP) uncomplexed by beta gamma subunits appears to be the preferred substrate. In functional studies, phosphorylation of stimulatory G alpha (G alpha s) modestly increases the rate of binding of guanosine 5'-[gamma-[35S]thio]triphosphate to Gs as well as the receptor-stimulated steady-state rate of GTP hydrolysis by Gs. Heterotrimeric G proteins may represent a previously unappreciated class of potential substrates for pp60c-src.

100 citations

Journal ArticleDOI
TL;DR: One mechanism by which cortisone modulates beta-adrenergic receptor function appears to be through facilitating the formation of the high affinity state of the receptor, resulting in greater coupling of receptor occupation with adenylate cyclase activation.
Abstract: β-Adrenergic agonists form high affinity complexes with receptors, resulting in activation of the associated adenylate cyclase. To examine the formation of the high affinity state of the receptor, curves were constructed for the competition of the full β-adrenergic agonist isoproterenol, partial agonists cobefrin and soterenol, and the antagonist propranolol for [3H]dihydroalprenolol binding to β-adrenergic receptors on human neutrophil membranes. Curve modeling by computer yielded a two-state binding model for the agonists, with distinct dissociation constants for the high (KH) and low (KL) affinity states. The ratio of dissociation constants (KL/KH) was found to be well correlated (P < 0.01) with the drug’s intrinsic activity for stimulation of adenylate cyclase. Thus, the degree of coupling of receptor occupation with adenylate cyclase activation is correlated with the magnitude of KL/KH. Administration of cortisone to humans resulted in a substantial rise in the proportion of receptors in the high aff...

100 citations

Journal Article
TL;DR: The polyene antibiotic Filipin appears to "uncouple" receptor binding and enzyme activation, since a marked reduction in isoproterenol-stimulated adenylate cyclase is not accompanied by a decrease in specific (-)-[3H]dihydroalprenolol binding.
Abstract: Binding of (-)-[3H]dihydroalprenolol, a potent competitive beta adrenergic antagonist, to sites in frog erythrocyte membranes has previously been demonstrated to possess the essential properties expected of binding to adenylate cyclase-coupled beta adrenergic receptors. The present studies were designed to test the effects of a variety of membrane lipid-perturbing agents on both beta adrenergic receptor binding and catecholamine-responsive adenylate cyclase in frog erythrocyte membranes. Digestion of membranes with phospholipases A, C, and D causes a dose-dependent decline in receptor binding capacity without altering receptor affinity. Amphotericin B, a nondegradative membrane lipid perturbant, also causes a dose-dependent decrease in (-)-[3H]dihydroalprenolol binding. Decrements in catecholamine-stimulated adenylate cyclase activity caused by these agents are always greater than decreases in basal and fluoride-sensitive enzyme activities. Decreases in (-)-[3H]dihydroalprenolol binding parallel the disproportionate reduction in catecholamine responsiveness of adenylate cyclase. By contrast, the polyene antibiotic Filipin appears to "uncouple" receptor binding and enzyme activation, since a marked reduction in isoproterenol-stimulated adenylate cyclase is not accompanied by a decrease in specific (-)-[3H]dihydroalprenolol binding. ACKNOWLEDGMENTS The electron microscopic studies in consultation were performed by Dr. J. R. Sommer, Director, Veterans Administration EM Laboratory, Veterans Administration Hospital, Durham, N. C. The authors thank Dr. Mary Ellen Switzer for fibrinogen degradation studies and Dr. Patrick McKee for helpful discussion. The authors also acknowledge Mr. Michael Coverstone for technical assistance.

99 citations


Cited by
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28 Jul 2005
TL;DR: PfPMP1)与感染红细胞、树突状组胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作�ly.
Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1(PfPMP1)与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用,在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员,通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

18,940 citations

Journal ArticleDOI
19 Feb 1998-Nature
TL;DR: To their surprise, it was found that double-stranded RNA was substantially more effective at producing interference than was either strand individually, arguing against stochiometric interference with endogenous mRNA and suggesting that there could be a catalytic or amplification component in the interference process.
Abstract: Experimental introduction of RNA into cells can be used in certain biological systems to interfere with the function of an endogenous gene Such effects have been proposed to result from a simple antisense mechanism that depends on hybridization between the injected RNA and endogenous messenger RNA transcripts RNA interference has been used in the nematode Caenorhabditis elegans to manipulate gene expression Here we investigate the requirements for structure and delivery of the interfering RNA To our surprise, we found that double-stranded RNA was substantially more effective at producing interference than was either strand individually After injection into adult animals, purified single strands had at most a modest effect, whereas double-stranded mixtures caused potent and specific interference The effects of this interference were evident in both the injected animals and their progeny Only a few molecules of injected double-stranded RNA were required per affected cell, arguing against stochiometric interference with endogenous mRNA and suggesting that there could be a catalytic or amplification component in the interference process

15,374 citations

Journal ArticleDOI
TL;DR: This approach provides two major advantages compared with other available methods: it uses an exact mathematical model of the ligand-binding system, thereby avoiding the possible biases introduced by several commonly used approximations and it uses a statistically valid, appropriately weighted least-squares curve-fitting algorithm with objective measurement of goodness of fit.

8,717 citations

Journal ArticleDOI
13 Oct 2000-Cell
TL;DR: Understanding of the complex signaling networks downstream from RTKs and how alterations in these networks are translated into cellular responses provides an important context for therapeutically countering the effects of pathogenic RTK mutations in cancer and other diseases.

7,056 citations

Journal ArticleDOI
TL;DR: This review considers recent findings regarding GC action and generates criteria for determining whether a particular GC action permits, stimulates, or suppresses an ongoing stress-response or, as an additional category, is preparative for a subsequent stressor.
Abstract: The secretion of glucocorticoids (GCs) is a classic endocrine response to stress. Despite that, it remains controversial as to what purpose GCs serve at such times. One view, stretching back to the time of Hans Selye, posits that GCs help mediate the ongoing or pending stress response, either via basal levels of GCs permitting other facets of the stress response to emerge efficaciously, and/or by stress levels of GCs actively stimulating the stress response. In contrast, a revisionist viewpoint posits that GCs suppress the stress response, preventing it from being pathologically overactivated. In this review, we consider recent findings regarding GC action and, based on them, generate criteria for determining whether a particular GC action permits, stimulates, or suppresses an ongoing stressresponse or, as an additional category, is preparative for a subsequent stressor. We apply these GC actions to the realms of cardiovascular function, fluid volume and hemorrhage, immunity and inflammation, metabolism, neurobiology, and reproductive physiology. We find that GC actions fall into markedly different categories, depending on the physiological endpoint in question, with evidence for mediating effects in some cases, and suppressive or preparative in others. We then attempt to assimilate these heterogeneous GC actions into a physiological whole. (Endocrine Reviews 21: 55‐ 89, 2000)

6,707 citations