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Biochem Biophys Res Commun

Title:		Relationship between the G protein signaling and homologous desensitization of G protein-coupled receptors
Author(s):		Barak LS; Gilchrist J; Becker JM; Kim KM;
Address:		"Department of Cell Biology, Duke University Medical Center, Durham, NC 27710, USA"
Journal Title:		Biochem Biophys Res Commun
Year:		2006
Volume:		339
Issue:		2
Page Number:		695 - 700
DOI:		10.1016/j.bbrc.2005.11.070
ISSN/ISBN:		0006-291X (Print) 0006-291X (Linking)
Abstract:		"Signaling and desensitization of G protein-coupled receptor are intimately related, and measuring them separately requires certain parameters that represent desensitization independently of signaling. In this study, we tested whether desensitization requires signaling in three different receptors, beta2-adrenergic receptor (beta2AR) in S49 lymphoma cells, alpha-factor pheromone receptor (Ste2p) in Saccharomyces cerevisiae LM102 cells, and dopamine D3 receptor (D3R) in HEK-293 cells. Agonist-induced beta-arrestin translocation to the plasma membrane or receptor sequestration was measured to estimate homologous desensitization. To separate the signaling and desensitization of beta2AR, which mediates stimulation of adenylyl cyclase, S49 lymphoma cys- cells that lack the alpha subunit of Gs were used. Stimulation of beta2AR in these cells failed to increase intracellular cAMP, but beta-arrestin translocation still occurred, suggesting that feedback from beta2AR signaling is not required for homologous desensitization to occur. Agonist-induced sequestration of the yeast Ste2p-L236R, which showed reduced signaling through G protein, was not different from that of wildtype Ste2p, suggesting that the receptor signaling and sequestration are not directly linked cellular events. Both G protein coupling and D3R signaling, measured as inhibition of cAMP production, were greatly enhanced by co-expression of exogenous alpha subunit of Go (Goalpha) or adenylyl cyclase type 5 (AC5), respectively. However, agonist-induced beta-arrestin translocation, receptor phosphorylation, and sequestration were not affected by co-expression of Galphao and AC5, suggesting that the extent of signaling does not determine desensitization intensity. Taken together, our results consistently suggest that G protein signaling and homologous desensitization are independent cellular processes"
Keywords:		"Animals Cell Line Chlorocebus aethiops Heterotrimeric GTP-Binding Proteins/*metabolism Humans Ligands Receptors, Adrenergic, beta-2/genetics/metabolism Receptors, Dopamine D3/genetics/metabolism Receptors, G-Protein-Coupled/genetics/*metabolism Receptors, ;"
Notes:		"MedlineBarak, Larry S Gilchrist, Jacqueline Becker, Jeffrey M Kim, Kyeong-Man eng GM22087/GM/NIGMS NIH HHS/ Research Support, N.I.H., Extramural Research Support, Non-U.S. Gov't 2005/12/06 Biochem Biophys Res Commun. 2006 Jan 13; 339(2):695-700. doi: 10.1016/j.bbrc.2005.11.070"