EFR3s are palmitoylated plasma membrane proteins that control responsiveness to G-protein-coupled receptors.
The yeast Efr3p protein is a main regulator of the Stt4p phosphatidylinositol 4-kinase at contact sites between the endoplasmic reticulum and the plasma membrane. A mutation in its fly homologue Rbo, leads to diminished light responses in the eye attributed to progressively impaired PLC signaling. Here, we find that Efr3s plays a role in maintaining responsiveness to the type-I angiotensin II (AngII) receptors. siRNA-mediated depletion of EFR3A and EFR3B impaired the sustained phase of cytosolic Ca(2+) response to high concentration of AngII in HEK293 cells that express wild type but not truncated AGTR1 (AT1a receptor), missing the phosphorylation sites. Efr3 depletion had minimal effect on the recovery of plasma membrane phosphoinositides during stimulation, and AT1 receptors still underwent ligand-induced internalization. A higher level of basal receptor phosphorylation and a larger response was observed after stimulation. Moreover, Gq activation more rapidly desensitized after AngII stimulation in Efr3 downregulated cells. A similar but less pronounced effect of EFR3 depletion was observed on the desensitization of the cAMP response after stimulation with isoproterenol. These data suggest that mammalian Efr3s contribute to the control of the phosphorylation state and, hence, desensitization of AT1a receptors, and could affect responsiveness of G-protein-coupled receptors in higher eukaryotes.
Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA.
Naveen
N
Bojjireddy
Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA.
Maria Luisa
ML
Guzman-Hernandez
Swammerdam Institute for Life Sciences, University of Amsterdam, 1012 WX Amsterdam, The Netherlands.
Nathalie Renée
NR
Reinhard
Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA.
Marko
M
Jovic
Section on Molecular Signal Transduction, Program for Developmental Neuroscience, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA ballat@mail.nih.gov.
Tamas
T
Balla
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000242:Cyclic AMP / Q000235:genetics / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D007545:Isoproterenol / Q000494:pharmacology; D054878:Lipoylation / Q000187:drug effects / Q000502:physiology*; D010766:Phosphorylation / Q000187:drug effects; D044140:Receptor, Angiotensin, Type 1 / Q000235:genetics / Q000378:metabolism*; D015290:Second Messenger Systems / Q000187:drug effects / Q000502:physiology*
C544065:AGTR1 protein, human; D000318:Adrenergic beta-Agonists; D044140:Receptor, Angiotensin, Type 1; D000242:Cyclic AMP; D007545:Isoproterenol
Angiotensin II; EFR3; GPCR; PI 4-kinase; Phosphoinositide; Receptor desensitization