Not so dry after all - DRY mutants of the AT1A receptor and H1 receptor can induce G protein-dependent signaling

Abstract

GPCRs are seven transmembrane spanning receptors that regulate a wide array of intracellular signaling cascades in response to various stimuli. To do so, they couple to different heterotrimeric G proteins and adaptor proteins, including arrestins. Importantly, arrestins were shown to regulate GPCR signaling through G proteins, as well as promote G protein-independent signaling events. Several research groups have reported successful isolation of exclusively G protein-dependent and arrestin-dependent signaling downstream of GPCR activation using biased agonists or receptor mutants incapable of coupling to either arrestins or G proteins. In the latter category, the DRY mutant of the angiotensin II type 1 receptor was extensively used to characterize functional selectivity downstream of AT1AR. In an attempt to understand histamine 1 receptor signaling, we characterized the signaling capacity of the H1R DRY mutant in a panel of dynamic, live cell biosensor assays, including arrestin recruitment, heterotrimeric G-protein activation, Ca2+ signaling, protein kinase C activity, GTP binding of RhoA, and activation of ERK1/2. Here we show that both H1R DRY mutant and the AT1AR DRY mutant (used as a reference) are capable of efficient activation of G protein-mediated signaling. Therefore, contrary to common belief, they do not constitute suitable tools for dissection of arrestin-mediated, G protein-independent signaling downstream of these receptors.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=67 SRC=\"FIGDIR/small/773044v2_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (27K):\norg.highwire.dtl.DTLVardef@3b068eorg.highwire.dtl.DTLVardef@12b6a4borg.highwire.dtl.DTLVardef@14f66a1org.highwire.dtl.DTLVardef@1dad4b3_HPS_FORMAT_FIGEXP M_FIG C_FIG