title: Mass-dependent signaling between G protein coupled receptors.
abstract: The present study provides evidence that G protein coupled receptor (GPCR) signaling pathways participate in an interactive signaling network governed by the principles of mass action. Using an inducible thromboxane A2 receptor (TPR)/platelet activating factor receptor (PAFR) co-expressing cell model, TPR or PAFR expression was independently up-regulated. Immunostaining and radioligand binding experiments demonstrated that this receptor up-regulation resulted in increased GPCR:G protein mass ratios. This increase in mass ratio impacted both TPR and PAFR ligand affinity. Specifically, up-regulating TPR expression not only decreased TPR ligand affinity, but also decreased the ligand affinity of PAFRs. A similar effect on ligand affinities was observed when PAFRs were up-regulated. In addition, increasing the GPCR:G protein mass ratio for TPRs led to desensitization of the calcium mobilization response to PAFR activation, and increasing PAFR mass desensitized the TPR-mediated calcium response. Finally, it was observed that an increased TPR:G protein mass ratio was associated with a shift in the TPR signaling response, and revealed an additional TPR signaling pathway through G(S). Collectively, these results describe a novel mechanism, i.e., mass-dependent GPCR signaling, by which cells can modulate their GPCR signaling pathways and signaling priorities.
authors.affiliation: Department of Pharmacology, College of Medicine, University of Illinois at Chicago, 835 S. Wolcott Ave. (mail code 868), Chicago, IL 60612, USA.
authors.forename: Jin-Sheng
authors.initials: JS
authors.lastname: Huang
authors.forename: Lanlan
authors.initials: L
authors.lastname: Dong
authors.forename: Guy C
authors.initials: GC
authors.lastname: Le Breton
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D000818:Animals; D001381:Azepines / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects; D016466:CHO Cells; D002118:Calcium / Q000378:metabolism; D006224:Cricetinae; D006801:Humans; D008024:Ligands; D010980:Platelet Membrane Glycoproteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D043562:Receptors, G-Protein-Coupled / Q000037:antagonists & inhibitors / Q000187:drug effects / Q000378:metabolism*; D044244:Receptors, Thromboxane A2, Prostaglandin H2 / Q000819:agonists / Q000037:antagonists & inhibitors / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors; D014230:Triazoles / Q000494:pharmacology; D015854:Up-Regulation
chemical_list: D001381:Azepines; D008024:Ligands; D010980:Platelet Membrane Glycoproteins; D043562:Receptors, G-Protein-Coupled; D044244:Receptors, Thromboxane A2, Prostaglandin H2; D014230:Triazoles; C039351:platelet activating factor receptor; C052518:WEB 2086; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D002118:Calcium