Reciprocal Regulation of Angiotensin Receptor-activated Extracellular Signal-regulated Kinases by β-Arrestins 1 and 2

β-Arrestin2 not only plays essential roles in seven membrane-spanning receptor desensitization and internalization but also functions as a signal transducer in mitogen-activated protein kinase cascades. Here we show that the angiotensin II type 1A receptor-mediated activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in HEK-293 cells is increased when the cellular level of β-arrestin1 is down-regulated by RNA interference but is decreased or eliminated when the cellular level of β-arrestin2 is diminished. Such reciprocal effects of down-regulated levels of β-arrestins 1 and 2 are primarily due to differences in the ability of the two forms of β-arrestins to directly mediate ERK activation. These results are the first to demonstrate reciprocal activity of β-arrestin isoforms on a signaling pathway and suggest that physiological levels of β-arrestin1 may act as “dominant-negative” inhibitors of β-arrestin2-mediated ERK activation. β-Arrestin2 not only plays essential roles in seven membrane-spanning receptor desensitization and internalization but also functions as a signal transducer in mitogen-activated protein kinase cascades. Here we show that the angiotensin II type 1A receptor-mediated activation of extracellular signal-regulated kinases 1 and 2 (ERK1/2) in HEK-293 cells is increased when the cellular level of β-arrestin1 is down-regulated by RNA interference but is decreased or eliminated when the cellular level of β-arrestin2 is diminished. Such reciprocal effects of down-regulated levels of β-arrestins 1 and 2 are primarily due to differences in the ability of the two forms of β-arrestins to directly mediate ERK activation. These results are the first to demonstrate reciprocal activity of β-arrestin isoforms on a signaling pathway and suggest that physiological levels of β-arrestin1 may act as “dominant-negative” inhibitors of β-arrestin2-mediated ERK activation. Upon agonist binding, seven membrane-spanning (7MS) 1The abbreviations used are: 7MS, seven membrane-spanning; RNAi, RNA interference; siRNA, small interfering RNA; AT1A, angiotensin II type 1A; AngII, angiotensin II; SII-AngII, Sal1,Ile4,Ile8-angiotensin II; ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; PKC, protein kinase C; V2, vasopressin 2; EGF, epidermal growth factor; PMA, phorbol 12-myristate 13-acetate; HA, hemagglutinin; IP, inositol phosphate. 1The abbreviations used are: 7MS, seven membrane-spanning; RNAi, RNA interference; siRNA, small interfering RNA; AT1A, angiotensin II type 1A; AngII, angiotensin II; SII-AngII, Sal1,Ile4,Ile8-angiotensin II; ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; PKC, protein kinase C; V2, vasopressin 2; EGF, epidermal growth factor; PMA, phorbol 12-myristate 13-acetate; HA, hemagglutinin; IP, inositol phosphate. receptors are phosphorylated by G protein-coupled receptor kinases, which promotes recruitment of cytosolic β-arrestins to the receptor (1Lefkowitz R.J. J. Biol. Chem. 1998; 273: 18677-18680Abstract Full Text Full Text PDF PubMed Scopus (903) Google Scholar). Binding of β-arrestins not only mediates receptor desensitization by physically interfering with the receptor coupling to its cognate G protein (1Lefkowitz R.J. J. Biol. Chem. 1998; 273: 18677-18680Abstract Full Text Full Text PDF PubMed Scopus (903) Google Scholar, 2Pitcher J.A. Freedman N.J. Lefkowitz R.J. Annu. Rev. Biochem. 1998; 67: 653-692Crossref PubMed Scopus (1060) Google Scholar) but also initiates receptor internalization by interaction with several elements of the clathrin-coated pit endocytic machinery (3Goodman Jr., O.B. Krupnick J.G. Santini F. Gurevich V.V. Penn R.B. Gagnon A.W. Keen J.H. Benovic J.L. Nature. 1996; 383: 447-450Crossref PubMed Scopus (1154) Google Scholar, 4Laporte S.A. Oakley R.H. Zhang J. Holt J.A. Ferguson S.S. Caron M.G. Barak L.S. Proc. Natl. PubMed Scopus Google Scholar, J.A. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of is as a signal transducer and which a of signaling kinases Ferguson S.S. F. Caron M.G. Lefkowitz R.J. PubMed Scopus Google Scholar, J. Ferguson S.S. PubMed Scopus Google Scholar, Proc. Natl. PubMed Scopus Google Scholar) and of mitogen-activated protein kinase to activation Proc. Natl. PubMed Scopus Google Scholar, J. J. Biol. PubMed Scopus Google Scholar, S.A. R.J. Lefkowitz R.J. PubMed Google Scholar, Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Oakley R.H. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Such and of extracellular signal-regulated kinases to a angiotensin II type 1A Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google 1 Proc. Natl. PubMed Scopus Google J. J. Biol. PubMed Scopus Google and vasopressin 2 receptors Oakley R.H. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of β-arrestins cytosolic ERK activation of or receptors Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Oakley R.H. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the RNA interference that β-arrestin2 mediates G activation receptor S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google as as that β-arrestin2 is receptor-mediated and activation J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google of two in and and the β-arrestins 1 and also as 2 and in J.L. J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google Scholar, Benovic J.L. J. Caron M.G. Lefkowitz R.J. PubMed Scopus Google Scholar, J.G. Benovic J.L. Annu. Rev. 1998; PubMed Scopus Google Scholar). 1 and 2 are may in of functions of desensitization and of β-arrestin2 β-arrestin1 in (3Goodman Jr., O.B. Krupnick J.G. Santini F. Gurevich V.V. Penn R.B. Gagnon A.W. Keen J.H. Benovic J.L. Nature. 1996; 383: 447-450Crossref PubMed Scopus (1154) Google Scholar). also to β-arrestin2 in S.A. Oakley R.H. Zhang J. Holt J.A. Ferguson S.S. Caron M.G. Barak L.S. Proc. Natl. PubMed Scopus Google Scholar). several receptors to β-arrestin2 β-arrestin1 R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). G protein-coupled as as the type growth to but not in internalization J. Caron M.G. Barak L.S. Lefkowitz R.J. PubMed Scopus Google Scholar, J. Lefkowitz R.J. PubMed Scopus Google Scholar). the the receptor 1 and the receptor to β-arrestin1 PubMed Scopus Google Scholar, J.L. Ferguson S.S. PubMed Scopus Google Scholar). the of of but not kinase by S.A. R.J. Lefkowitz R.J. PubMed Google Scholar). the of ERK, of β-arrestin2 levels by is to G activation S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google that physiological the of β-arrestin2 to to as to the roles of β-arrestins 1 and physiological in signal to ERK the II and II and II by growth phorbol 12-myristate and the receptor by Caron of with RNA and in and β-arrestin 1 and β-arrestin 2 are and to the and to the Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). RNA as the used as a and cells as R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). to cells in with of and 2 the receptor the as Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). cells receptor or inositol or to cellular receptor by as S.A. 1996; Google and of protein in of and in a 2 1 1 1 and by of on or β-arrestins 1 and and to and β-arrestins by with or kinase and or R.H. J.A. PubMed Scopus Google Scholar) the and and β-arrestin by with a β-arrestins 1 and 2 a of J.L. J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google in of in of essential with with and with agonist and as J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google Scholar). to of in the we that β-arrestin2 plays a in G activation by the receptor in HEK-293 cells S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). receptor to with β-arrestins 1 and 2 R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the cellular level of β-arrestin1 of is as as that of β-arrestin2 of in HEK-293 cells we the of of β-arrestin1 on activation of receptors in HEK-293 that β-arrestin1 or of β-arrestin with of β-arrestin2 receptor-mediated activation by of that in cells of β-arrestin1 receptor-mediated activation of β-arrestin on activation that of β-arrestins receptor-mediated ERK results that β-arrestins 1 and 2 roles in receptor-mediated ERK as a and a β-arrestin1 levels receptor-mediated which is to the of β-arrestin2 two on that the receptor mediate activation two and G signaling S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). is that but not mediates receptor desensitization of G protein of β-arrestin1 by desensitization of the in of G activation. is that β-arrestin1 as a physiological the level of the receptor to the ERK activation the receptor β-arrestins R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the decreased level of β-arrestin1 β-arrestin2 to in the ERK pathway receptor in of receptor is to which to of and β-arrestins 1 and 2 roles in receptor we activation of the receptor in or β-arrestin2 cells of β-arrestin1 or β-arrestin2 not receptor-mediated with that in that of β-arrestin is not to of receptor coupling to G These are with results with β-arrestin in which of β-arrestins is to desensitization of Lefkowitz R.J. Proc. Natl. Google Scholar). results suggest that increased receptor-mediated activation in β-arrestin1 cells is not due to coupling of the receptor to G of of β-arrestin 1 or 2 on HEK-293 with and the with of cells with AngII, of by of inositol in and as of in the in that the G pathway to ERK activation in HEK-293 cells is to the S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). that the in receptor-mediated activation by of β-arrestin1 levels is not primarily due to of G we effects of on the activation of with the results in in receptor-mediated activation in that as G activation of by to results S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google β-arrestin2 of and the signal is by with the which These results suggest that in of the activation by is by β-arrestin2 and by G with with the only of the receptor-mediated activation in cells These that activation is a of the ERK signaling pathway by the receptor in HEK-293 β-arrestin1 activation receptor is that in cells that the increased level of receptor-mediated activation of β-arrestin1 levels is primarily due to in of the on receptor-mediated ERK activation in β-arrestin HEK-293 with and the and with or 1 with or and cellular to of as of in of which is by in cells as a of ERK in by and as of the ERK level in the to its to receptor coupling to G J. PubMed Scopus Google Scholar). that activation of in to is S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). to the by which the ERK activity is by of we receptor-mediated activation by in and β-arrestin2 cells with results S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google the of β-arrestin2 activation. the of β-arrestin1 activation with that in These the that the in receptor-mediated which in the of decreased levels of β-arrestin1 is due to signaling the ERK effects of of β-arrestins 1 and 2 on ERK HEK-293 cells with and the cells in by with of and of as of in the of ERK in by and as of the ERK in to in the results demonstrate that the two β-arrestins 1 and reciprocal roles in receptor-mediated ERK suggest that physiological levels in HEK-293 as a that with β-arrestin2-mediated activation. a in cells that of β-arrestin1 as as β-arrestin2 receptor-mediated cytosolic activation Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). that β-arrestin1 is β-arrestin2 in the ERK activation β-arrestins are to the receptor R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). physiological β-arrestin1 with β-arrestin2 to the a in the level of receptor that activation the which are by β-arrestin1 a to the ERK not only are levels of β-arrestin1 β-arrestin2 to β-arrestin2 activation by AngII, but levels of β-arrestin1 to not are also with of β-arrestin1 is that of β-arrestin2 in receptor-mediated cytosolic activation Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the results as as S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar) that G activation with by of β-arrestin2 demonstrate that β-arrestin1 physiological levels the signal to activation receptor a of physiological roles of β-arrestins not only in receptor-mediated but also in receptor that β-arrestins 1 and 2 are not in the are the first to that the two forms of β-arrestins reciprocal functions in a receptor-mediated signaling the β-arrestins 1 and 2 in may in signaling of the cellular of β-arrestin may of of Upon agonist binding, seven membrane-spanning (7MS) 1The abbreviations used are: 7MS, seven membrane-spanning; RNAi, RNA interference; siRNA, small interfering RNA; AT1A, angiotensin II type 1A; AngII, angiotensin II; SII-AngII, Sal1,Ile4,Ile8-angiotensin II; ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; PKC, protein kinase C; V2, vasopressin 2; EGF, epidermal growth factor; PMA, phorbol 12-myristate 13-acetate; HA, hemagglutinin; IP, inositol phosphate. 1The abbreviations used are: 7MS, seven membrane-spanning; RNAi, RNA interference; siRNA, small interfering RNA; AT1A, angiotensin II type 1A; AngII, angiotensin II; SII-AngII, Sal1,Ile4,Ile8-angiotensin II; ERK, extracellular signal-regulated kinase; MAPK, mitogen-activated protein kinase; PKC, protein kinase C; V2, vasopressin 2; EGF, epidermal growth factor; PMA, phorbol 12-myristate 13-acetate; HA, hemagglutinin; IP, inositol phosphate. receptors are phosphorylated by G protein-coupled receptor kinases, which promotes recruitment of cytosolic β-arrestins to the receptor (1Lefkowitz R.J. J. Biol. Chem. 1998; 273: 18677-18680Abstract Full Text Full Text PDF PubMed Scopus (903) Google Scholar). Binding of β-arrestins not only mediates receptor desensitization by physically interfering with the receptor coupling to its cognate G protein (1Lefkowitz R.J. J. Biol. Chem. 1998; 273: 18677-18680Abstract Full Text Full Text PDF PubMed Scopus (903) Google Scholar, 2Pitcher J.A. Freedman N.J. Lefkowitz R.J. Annu. Rev. Biochem. 1998; 67: 653-692Crossref PubMed Scopus (1060) Google Scholar) but also initiates receptor internalization by interaction with several elements of the clathrin-coated pit endocytic machinery (3Goodman Jr., O.B. Krupnick J.G. Santini F. Gurevich V.V. Penn R.B. Gagnon A.W. Keen J.H. Benovic J.L. Nature. 1996; 383: 447-450Crossref PubMed Scopus (1154) Google Scholar, 4Laporte S.A. Oakley R.H. Zhang J. Holt J.A. Ferguson S.S. Caron M.G. Barak L.S. Proc. Natl. PubMed Scopus Google Scholar, J.A. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of is as a signal transducer and which a of signaling kinases Ferguson S.S. F. Caron M.G. Lefkowitz R.J. PubMed Scopus Google Scholar, J. Ferguson S.S. PubMed Scopus Google Scholar, Proc. Natl. PubMed Scopus Google Scholar) and of mitogen-activated protein kinase to activation Proc. Natl. PubMed Scopus Google Scholar, J. J. Biol. PubMed Scopus Google Scholar, S.A. R.J. Lefkowitz R.J. PubMed Google Scholar, Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Oakley R.H. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). Such and of extracellular signal-regulated kinases to a angiotensin II type 1A Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google 1 Proc. Natl. PubMed Scopus Google J. J. Biol. PubMed Scopus Google and vasopressin 2 receptors Oakley R.H. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of β-arrestins cytosolic ERK activation of or receptors Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar, Oakley R.H. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the RNA interference that β-arrestin2 mediates G activation receptor S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google as as that β-arrestin2 is receptor-mediated and activation J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). of two in and and the β-arrestins 1 and also as 2 and in J.L. J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google Scholar, Benovic J.L. J. Caron M.G. Lefkowitz R.J. PubMed Scopus Google Scholar, J.G. Benovic J.L. Annu. Rev. 1998; PubMed Scopus Google Scholar). 1 and 2 are may in of functions of desensitization and of β-arrestin2 β-arrestin1 in (3Goodman Jr., O.B. Krupnick J.G. Santini F. Gurevich V.V. Penn R.B. Gagnon A.W. Keen J.H. Benovic J.L. Nature. 1996; 383: 447-450Crossref PubMed Scopus (1154) Google Scholar). also to β-arrestin2 in S.A. Oakley R.H. Zhang J. Holt J.A. Ferguson S.S. Caron M.G. Barak L.S. Proc. Natl. PubMed Scopus Google Scholar). several receptors to β-arrestin2 β-arrestin1 R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). G protein-coupled as as the type growth to but not in internalization J. Caron M.G. Barak L.S. Lefkowitz R.J. PubMed Scopus Google Scholar, J. Lefkowitz R.J. PubMed Scopus Google Scholar). the the receptor 1 and the receptor to β-arrestin1 PubMed Scopus Google Scholar, J.L. Ferguson S.S. PubMed Scopus Google Scholar). the of of but not kinase by S.A. R.J. Lefkowitz R.J. PubMed Google Scholar). the of ERK, of β-arrestin2 levels by is to G activation S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google that physiological the of β-arrestin2 to to as to the roles of β-arrestins 1 and physiological in signal to ERK the II and II and II by growth phorbol 12-myristate and the receptor by Caron of with RNA and in and β-arrestin 1 and β-arrestin 2 are and to the and to the Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). RNA as the used as a and cells as R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). to cells in with of and 2 the receptor the as Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). cells receptor or inositol or to cellular receptor by as S.A. 1996; Google and of protein in of and in a 2 1 1 1 and by of on or β-arrestins 1 and and to and β-arrestins by with or kinase and or R.H. J.A. PubMed Scopus Google Scholar) the and and β-arrestin by with a β-arrestins 1 and 2 a of J.L. J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google in of in of essential with with and with agonist and as J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google Scholar). to of in II and II and II by growth phorbol 12-myristate and the receptor by Caron of with RNA and in and β-arrestin 1 and β-arrestin 2 are and to the and to the Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). RNA as the used as a and cells as R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). to cells in with of and 2 the receptor the as Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). cells receptor or inositol or to cellular receptor by as S.A. 1996; Google and of protein in of and in a 2 1 1 1 and by of on or β-arrestins 1 and and to and β-arrestins by with or kinase and or R.H. J.A. PubMed Scopus Google Scholar) the and and β-arrestin by with a β-arrestins 1 and 2 a of J.L. J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google Scholar). in of in of essential with with and with agonist and as J. Caron M.G. Lefkowitz R.J. J. Biol. Chem. Full Text PDF PubMed Google Scholar). to of in the we that β-arrestin2 plays a in G activation by the receptor in HEK-293 cells S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). receptor to with β-arrestins 1 and 2 R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the cellular level of β-arrestin1 of is as as that of β-arrestin2 of in HEK-293 cells we the of of β-arrestin1 on activation of receptors in HEK-293 that β-arrestin1 or of β-arrestin with of β-arrestin2 receptor-mediated activation by of that in cells of β-arrestin1 receptor-mediated activation of β-arrestin on activation that of β-arrestins receptor-mediated ERK results that β-arrestins 1 and 2 roles in receptor-mediated ERK as a and a β-arrestin1 levels receptor-mediated which is to the of β-arrestin2 two on that the receptor mediate activation two and G signaling S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). is that but not mediates receptor desensitization of G protein of β-arrestin1 by desensitization of the in of G activation. is that β-arrestin1 as a physiological the level of the receptor to the ERK activation the receptor β-arrestins R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the decreased level of β-arrestin1 β-arrestin2 to in the ERK pathway receptor in of receptor is to which to of and β-arrestins 1 and 2 roles in receptor we activation of the receptor in or β-arrestin2 cells of β-arrestin1 or β-arrestin2 not receptor-mediated with that in that of β-arrestin is not to of receptor coupling to G These are with results with β-arrestin in which of β-arrestins is to desensitization of Lefkowitz R.J. Proc. Natl. Google Scholar). results suggest that increased receptor-mediated activation in β-arrestin1 cells is not due to coupling of the receptor to G that the G pathway to ERK activation in HEK-293 cells is to the S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). that the in receptor-mediated activation by of β-arrestin1 levels is not primarily due to of G we effects of on the activation of with the results in in receptor-mediated activation in that as G activation of by to results S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google β-arrestin2 of and the signal is by with the which These results suggest that in of the activation by is by β-arrestin2 and by G with with the only of the receptor-mediated activation in cells These that activation is a of the ERK signaling pathway by the receptor in HEK-293 β-arrestin1 activation receptor is that in cells that the increased level of receptor-mediated activation of β-arrestin1 levels is primarily due to in of the on receptor-mediated ERK activation in β-arrestin HEK-293 with and the and with or 1 with or and cellular to of as of in of which is by in cells as a of ERK in by and as of the ERK level in the to its to receptor coupling to G J. PubMed Scopus Google Scholar). that activation of in to is S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). to the by which the ERK activity is by of we receptor-mediated activation by in and β-arrestin2 cells with results S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google the of β-arrestin2 activation. the of β-arrestin1 activation with that in These the that the in receptor-mediated which in the of decreased levels of β-arrestin1 is due to signaling the ERK effects of of β-arrestins 1 and 2 on ERK HEK-293 cells with and the cells in by with of and of as of in the of ERK in by and as of the ERK in to in the results demonstrate that the two β-arrestins 1 and reciprocal roles in receptor-mediated ERK suggest that physiological levels in HEK-293 as a that with β-arrestin2-mediated activation. a in cells that of β-arrestin1 as as β-arrestin2 receptor-mediated cytosolic activation Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). that β-arrestin1 is β-arrestin2 in the ERK activation β-arrestins are to the receptor R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). physiological β-arrestin1 with β-arrestin2 to the a in the level of receptor that activation the which are by β-arrestin1 a to the ERK not only are levels of β-arrestin1 β-arrestin2 to β-arrestin2 activation by AngII, but levels of β-arrestin1 to not are also with of β-arrestin1 is that of β-arrestin2 in receptor-mediated cytosolic activation Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the results as as S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar) that G activation with by of β-arrestin2 demonstrate that β-arrestin1 physiological levels the signal to activation receptor a of physiological roles of β-arrestins not only in receptor-mediated but also in receptor that β-arrestins 1 and 2 are not in the are the first to that the two forms of β-arrestins reciprocal functions in a receptor-mediated signaling the β-arrestins 1 and 2 in may in signaling of the cellular of β-arrestin may of of the we that β-arrestin2 plays a in G activation by the receptor in HEK-293 cells S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar, Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). receptor to with β-arrestins 1 and 2 R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the cellular level of β-arrestin1 of is as as that of β-arrestin2 of in HEK-293 cells we the of of β-arrestin1 on activation of receptors in HEK-293 that β-arrestin1 or of β-arrestin with of β-arrestin2 receptor-mediated activation by of that in cells of β-arrestin1 receptor-mediated activation of β-arrestin on activation that of β-arrestins receptor-mediated ERK results that β-arrestins 1 and 2 roles in receptor-mediated ERK as a and a β-arrestin1 levels receptor-mediated which is to the of β-arrestin2 two on that the receptor mediate activation two and G signaling S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). is that but not mediates receptor desensitization of G protein of β-arrestin1 by desensitization of the in of G activation. is that β-arrestin1 as a physiological the level of the receptor to the ERK activation the receptor β-arrestins R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the decreased level of β-arrestin1 β-arrestin2 to in the ERK pathway receptor in of activation. receptor is to which to of and β-arrestins 1 and 2 roles in receptor we activation of the receptor in or β-arrestin2 cells of β-arrestin1 or β-arrestin2 not receptor-mediated with that in that of β-arrestin is not to of receptor coupling to G These are with results with β-arrestin in which of β-arrestins is to desensitization of Lefkowitz R.J. Proc. Natl. Google Scholar). results suggest that increased receptor-mediated activation in β-arrestin1 cells is not due to coupling of the receptor to G that the G pathway to ERK activation in HEK-293 cells is to the S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). that the in receptor-mediated activation by of β-arrestin1 levels is not primarily due to of G we effects of on the activation of with the results in in receptor-mediated activation in that as G activation of by to results S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google β-arrestin2 of and the signal is by with the which These results suggest that in of the activation by is by β-arrestin2 and by G with with the only of the receptor-mediated activation in cells These that activation is a of the ERK signaling pathway by the receptor in HEK-293 β-arrestin1 activation receptor is that in cells that the increased level of receptor-mediated activation of β-arrestin1 levels is primarily due to in to its to receptor coupling to G J. PubMed Scopus Google Scholar). that activation of in to is S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar). to the by which the ERK activity is by of we receptor-mediated activation by in and β-arrestin2 cells with results S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google the of β-arrestin2 activation. the of β-arrestin1 activation with that in These the that the in receptor-mediated which in the of decreased levels of β-arrestin1 is due to signaling the ERK results demonstrate that the two β-arrestins 1 and reciprocal roles in receptor-mediated ERK suggest that physiological levels in HEK-293 as a that with β-arrestin2-mediated activation. a in cells that of β-arrestin1 as as β-arrestin2 receptor-mediated cytosolic activation Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). that β-arrestin1 is β-arrestin2 in the ERK activation β-arrestins are to the receptor R.H. S.A. Holt J.A. Caron M.G. Barak L.S. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). physiological β-arrestin1 with β-arrestin2 to the a in the level of receptor that activation the which are by β-arrestin1 a to the ERK not only are levels of β-arrestin1 β-arrestin2 to β-arrestin2 activation by AngII, but levels of β-arrestin1 to not are also with of β-arrestin1 is that of β-arrestin2 in receptor-mediated cytosolic activation Lefkowitz R.J. J. Biol. Chem. Full Text Full Text PDF PubMed Scopus Google Scholar). the results as as S.S. Lefkowitz R.J. Proc. Natl. PubMed Scopus Google Scholar) that G activation with by of β-arrestin2 demonstrate that β-arrestin1 physiological levels the signal to activation receptor activation. a of physiological roles of β-arrestins not only in receptor-mediated but also in receptor that β-arrestins 1 and 2 are not in the are the first to that the two forms of β-arrestins reciprocal functions in a receptor-mediated signaling the β-arrestins 1 and 2 in may in signaling of the cellular of β-arrestin may of of and also and of the and