Interaction with Cystic Fibrosis Transmembrane Conductance Regulator-associated Ligand (CAL) Inhibits β1-Adrenergic Receptor Surface Expression

Abstract

G protein-coupled receptors such as the β1-adrenergic receptor (β1AR) must be trafficked to the plasma membrane in order to bind with their extracellular ligands and regulate cellular physiology. By using glutathione S-transferase pull-down techniques, we found that the β1AR carboxyl terminus directly interacts with the cystic fibrosis transmembrane conductance regulator-associated ligand (CAL; also known as PIST, GOPC, and FIG), a protein known to be primarily localized to the Golgi apparatus. CAL contains two predicted coiled-coil domains and one PSD-95/Discs-large/ZO-1 homology (PDZ) domain. The β1AR carboxyl terminus (CT) binds to the PDZ domain of CAL, with the last few amino acids (ESKV) of the β1AR-CT being the key determinants for the interaction. Mutation of the terminal valine residue resulted in markedly reduced association of the β1AR-CT with CAL. Numerous other mutations to the ESKV motif also impaired the β1AR-CT/CAL interaction, suggesting that this motif is close to optimal for association with the CAL PDZ domain. In cells, full-length β1AR robustly associates with CAL, and this interaction is abolished by mutation of the terminal valine to alanine of the receptor (V477A), as determined by co-immunoprecipitation experiments and immunofluorescence co-localization studies. Consistent with observations that CAL is a Golgi-associated protein, overexpression of CAL reduces surface expression of β1AR. Interaction with CAL promotes retention of β1AR within the cell, whereas PSD-95, another β1AR-associated PDZ domain-containing protein, competitively blocks β1AR association with CAL and promotes receptor trafficking to the cell surface. These data reveal that CAL, a novel β1AR-binding partner, modulates β1AR intracellular trafficking, thereby revealing a new mechanism of regulation for β1AR anterograde trafficking through the endoplasmic reticulum-Golgi complex to the plasma membrane. G protein-coupled receptors such as the β1-adrenergic receptor (β1AR) must be trafficked to the plasma membrane in order to bind with their extracellular ligands and regulate cellular physiology. By using glutathione S-transferase pull-down techniques, we found that the β1AR carboxyl terminus directly interacts with the cystic fibrosis transmembrane conductance regulator-associated ligand (CAL; also known as PIST, GOPC, and FIG), a protein known to be primarily localized to the Golgi apparatus. CAL contains two predicted coiled-coil domains and one PSD-95/Discs-large/ZO-1 homology (PDZ) domain. The β1AR carboxyl terminus (CT) binds to the PDZ domain of CAL, with the last few amino acids (ESKV) of the β1AR-CT being the key determinants for the interaction. Mutation of the terminal valine residue resulted in markedly reduced association of the β1AR-CT with CAL. Numerous other mutations to the ESKV motif also impaired the β1AR-CT/CAL interaction, suggesting that this motif is close to optimal for association with the CAL PDZ domain. In cells, full-length β1AR robustly associates with CAL, and this interaction is abolished by mutation of the terminal valine to alanine of the receptor (V477A), as determined by co-immunoprecipitation experiments and immunofluorescence co-localization studies. Consistent with observations that CAL is a Golgi-associated protein, overexpression of CAL reduces surface expression of β1AR. Interaction with CAL promotes retention of β1AR within the cell, whereas PSD-95, another β1AR-associated PDZ domain-containing protein, competitively blocks β1AR association with CAL and promotes receptor trafficking to the cell surface. These data reveal that CAL, a novel β1AR-binding partner, modulates β1AR intracellular trafficking, thereby revealing a new mechanism of regulation for β1AR anterograde trafficking through the endoplasmic reticulum-Golgi complex to the plasma membrane. β-Adrenergic receptors (βARs) 1The abbreviations used are: βARs, β-adrenergic receptors; PDZ, PSD-95/Discs-large/ZO-1 homology; NHERF-1, Na+/H+ exchanger regulatory factor; CFTR, cystic fibrosis transmembrane conductance regulator; GST, glutathione S-transferase; CT, carboxyl-terminus; PSD-95, postsynaptic density protein of 95 kDa; MAGI, membrane-associated guanylate kinase-like protein with an inverted domain structure; HA, hemagglutinin; HEK, human embryonic kidney; ER, endoplasmic reticulum; GPCRs, G protein-coupled receptors; CAL, CFTR-associated ligand; PBS, phosphate-buffered saline.1The abbreviations used are: βARs, β-adrenergic receptors; PDZ, PSD-95/Discs-large/ZO-1 homology; NHERF-1, Na+/H+ exchanger regulatory factor; CFTR, cystic fibrosis transmembrane conductance regulator; GST, glutathione S-transferase; CT, carboxyl-terminus; PSD-95, postsynaptic density protein of 95 kDa; MAGI, membrane-associated guanylate kinase-like protein with an inverted domain structure; HA, hemagglutinin; HEK, human embryonic kidney; ER, endoplasmic reticulum; GPCRs, G protein-coupled receptors; CAL, CFTR-associated ligand; PBS, phosphate-buffered saline. are G protein-coupled receptors (GPCRs) that play critical roles in mediating physiological responses to the hormone epinephrine and the neurotransmitter norepinephrine. Noradrenergic stimulation of β1-adrenergic receptor (β1AR) in the brain potently regulates memory formation and synaptic plasticity (1Huang Y.Y. Kandel E.R. Neuron. 1996; 16: 611-617Abstract Full Text Full Text PDF PubMed Scopus (166) Google Scholar, 2Thomas M.J. Moody T.D. Makhinson M. O'Dell T.J. Neuron. 1996; 17: 475-482Abstract Full Text Full Text PDF PubMed Scopus (248) Google Scholar, 3Watanabe Y. Ikegaya Y. Saito H. Abe K. Neuroscience. 1996; 71: 1031-1035Crossref PubMed Scopus (18) Google Scholar, 4Winder D.G. Martin K.C. Muzzio I.A. Rohrer D. Chruscinski A. Kobilka B. Kandel E.R. Neuron. 1999; 24: 715-726Abstract Full Text Full Text PDF PubMed Scopus (282) Google Scholar, 5Wang S.J. Cheng L.L. Gean P.W. J. Neurosci. 1999; 19: 570-577Crossref PubMed Google Scholar, 6McGaugh J.L. Science. 2000; 287: 248-251Crossref PubMed Scopus (3160) Google Scholar), and stimulation of β1AR in the heart profoundly regulates both the rate and force of cardiac contractions (7Lohse M.J. Engelhardt S. Eschenhagen T. Circ. Res. 2003; 93: 896-906Crossref PubMed Scopus (586) Google Scholar, 8Xiang Y. Kobilka B.K. Science. 2003; 300: 1530-1532Crossref PubMed Scopus (178) Google Scholar, 9Dorn II, G.W. Molkentin J.D. Circulation. 2004; 109: 150-158Crossref PubMed Scopus (91) Google Scholar). Neither norepinephrine nor epinephrine can easily cross the plasma membrane; thus, β1AR must be localized at the cell surface in order to be activated by its ligands. The regulation of the trafficking and surface expression of β1AR and other GPCRs is therefore a topic of considerable physiological importance. Intracellular trafficking of GPCRs has been extensively studied, with most of this work focused on the events involved in receptor internalization and recycling. Within seconds or minutes of agonist stimulation, βARs are phosphorylated by G protein-coupled receptor kinases and cAMP-dependent protein kinases (10Ferguson S.S. Pharmacol Rev. 2001; 53: 1-24PubMed Google Scholar, 11Claing A. Laporte S.A. Caron M.G. Lefkowitz R.J. Prog. Neurobiol. 2002; 66: 61-79Crossref PubMed Scopus (443) Google Scholar). Subsequently, in the cases of β1AR and β2AR, this phosphorylation promotes the binding of the cytosolic protein β-arrestin, which inhibits the ability of the βARs to couple to G proteins and targets the phosphorylated receptors to clathrin-coated pits for endocytosis. In the cytoplasm, the internalized receptors are first accumulated in early endosomes, dephosphorylated, and subsequently recycled back via a perinuclear compartment to the plasma membrane in a fully resensitized state (10Ferguson S.S. Pharmacol Rev. 2001; 53: 1-24PubMed Google Scholar, 11Claing A. Laporte S.A. Caron M.G. Lefkowitz R.J. Prog. Neurobiol. 2002; 66: 61-79Crossref PubMed Scopus (443) Google Scholar). PDZ domain-containing scaffold proteins have recently been shown to modulate βAR intracellular trafficking via specific interactions with the carboxyl termini of β1AR and β2AR (12Hall R.A. Premont R.T. Chow C.W. Blitzer J.T. Pitcher J.A. Claing A. Stoffel R.H. Barak L.S. Shenolikar S. Weinman E.J. Grinstein S. Lefkowitz R.J. Nature. 1998; 392: 626-630Crossref PubMed Scopus (516) Google Scholar, 13Cao T.T. Deacon H.W. Reczek D. Bretscher A. von Zastrow M. Nature. 1999; 401: 286-290Crossref PubMed Scopus (561) Google Scholar, 14Hu L.A. Tang Y. Miller W.E. Cong M. Lau A.G. Lefkowitz R.J. Hall R.A. J. Biol. Chem. 2000; 275: 38659-38666Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar, 15Xu J. Paquet M. Lau A.G. Wood J.D. Ross C.A. Hall R.A. J. Biol. Chem. 2001; 276: 41310-41317Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar, 16Xiang Y. Devic E. Kobilka B. J. Biol. Chem. 2002; 277: 33783-33790Abstract Full Text Full Text PDF PubMed Scopus (87) Google Scholar). PDZ domains are named for the first three proteins in which they were identified (the post-synaptic density protein PSD-95, the Drosophila tumor suppressor protein Dlg, and the tight junction protein ZO-1), and are known to bind to their target proteins through specific carboxyl-terminal motifs (17Hung A.Y. Sheng M. J. Biol. Chem. 2002; 277: 5699-5702Abstract Full Text Full Text PDF PubMed Scopus (584) Google Scholar). The Na+/H+ exchanger regulatory factor (NHERF-1), a PDZ domain-containing protein, is known to associate with the β2-adrenergic receptor (β2AR) to control β2AR-mediated regulation of Na+/H+ exchange (12Hall R.A. Premont R.T. Chow C.W. Blitzer J.T. Pitcher J.A. Claing A. Stoffel R.H. Barak L.S. Shenolikar S. Weinman E.J. Grinstein S. Lefkowitz R.J. Nature. 1998; 392: 626-630Crossref PubMed Scopus (516) Google Scholar) and also to modulate β2AR endocytic sorting (13Cao T.T. Deacon H.W. Reczek D. Bretscher A. von Zastrow M. Nature. 1999; 401: 286-290Crossref PubMed Scopus (561) Google Scholar). β1AR does with associates with other PDZ proteins such as PSD-95, and to regulate its intracellular trafficking and L.A. Tang Y. Miller W.E. Cong M. Lau A.G. Lefkowitz R.J. Hall R.A. J. Biol. Chem. 2000; 275: 38659-38666Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar, 15Xu J. Paquet M. Lau A.G. Wood J.D. Ross C.A. Hall R.A. J. Biol. Chem. 2001; 276: 41310-41317Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar, L.A. Martin E.J. Premont R.T. Lefkowitz R.J. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. D. Biol. 2002; PubMed Scopus Google Scholar). and are PDZ proteins of the they on β1AR promotes β1AR internalization J. Paquet M. Lau A.G. Wood J.D. Ross C.A. Hall R.A. J. Biol. Chem. 2001; 276: 41310-41317Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar), whereas markedly inhibits L.A. Tang Y. Miller W.E. Cong M. Lau A.G. Lefkowitz R.J. Hall R.A. J. Biol. Chem. 2000; 275: 38659-38666Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar). on βAR trafficking have focused on the events involved in receptor and A. Laporte S.A. Caron M.G. Lefkowitz R.J. Prog. Neurobiol. 2002; 66: 61-79Crossref PubMed Scopus (443) Google Scholar), with to βARs are through their novel Golgi-associated PDZ protein CAL CFTR-associated has recently been found to modulate trafficking of J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar). a carboxyl-terminal motif to that of β1AR and β2AR and in and β2AR have both been found to associate with via this motif (12Hall R.A. Premont R.T. Chow C.W. Blitzer J.T. Pitcher J.A. Claing A. Stoffel R.H. Barak L.S. Shenolikar S. Weinman E.J. Grinstein S. Lefkowitz R.J. Nature. 1998; 392: 626-630Crossref PubMed Scopus (516) Google Scholar, R.A. L.S. Premont R.T. Blitzer J.T. M.J. Lefkowitz R.J. S. A. 1998; PubMed Scopus Google Scholar, S. M. 1998; PubMed Scopus Google Scholar, Reczek D. Bretscher A. M.J. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). the the and βAR carboxyl we the that CAL with one or both of the βARs to regulate the trafficking of the in the experiments in the of and CAL by B. The and PDZ domains of CAL and were via of a human CAL amino acids and amino acids by expression and proteins and were by the J. Lau A.G. Hall R.A. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar, J. J. S. Lau A.G. Hall R.A. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar). The β1AR carboxyl terminus (the last amino acids of the human β1-adrenergic and β2AR carboxyl terminus (the last amino acids of the human β2-adrenergic were by and mutations of both β1AR-CT and full-length were by and by The a Sheng of and and were and were in and in a receptors in the or of PDZ of with and to of in at of to the to and were were on for at and to The were in for at and with in for at The were three with of and were for at with a in the were three with of and were via using the proteins were using to the and were in and of proteins on were with of cell with at with for the were extensively with were with by and to CAL via with the by were via using the binding of receptor carboxyl-terminal proteins to PDZ domain proteins via a The receptor proteins were on and with the PDZ domains in a of in for at The were three with with for at and via as used for has been J. J. Hall R.A. 2003; PubMed Scopus Google Scholar). were and in the and with of for with at three the proteins were by with to the to the were in and in the and of The were in PBS, with in for and three in and with in for at The were with in for at The were subsequently three with of and for at with in the were three with of and one with of and with of for The which to the of receptor on the cell determined by using a J. J. Lau A.G. Hall R.A. Res. 2002; PubMed Scopus Google Scholar). CAL as a of and carboxyl-terminal motifs and are known to associate via motifs with of the PDZ such as and regulatory protein (12Hall R.A. Premont R.T. Chow C.W. Blitzer J.T. Pitcher J.A. Claing A. Stoffel R.H. Barak L.S. Shenolikar S. Weinman E.J. Grinstein S. Lefkowitz R.J. Nature. 1998; 392: 626-630Crossref PubMed Scopus (516) Google Scholar, R.A. L.S. Premont R.T. Blitzer J.T. M.J. Lefkowitz R.J. S. A. 1998; PubMed Scopus Google Scholar, S. M. 1998; PubMed Scopus Google Scholar, Reczek D. Bretscher A. M.J. J. Biol. Chem. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar, M.J. R.A. J. Biol. Chem. 2000; 275: Full Text Full Text PDF PubMed Scopus Google Scholar). the J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar) that can via its carboxyl-terminal motif with another PDZ protein, CAL, a that β2AR also associate with CAL. this we a protein pull-down The carboxyl termini of the human β2-adrenergic receptor and human β1-adrenergic receptor were as of with were and with cell that been with CAL. shown in bind to CAL. which a PDZ interaction motif to that of CFTR, found to robustly CAL the cell the that can associate with CAL. The ESKV of to the for the CAL PDZ the determinants of the β1AR-CT/CAL we the last of β1AR-CT to alanine and as shown in three of the at at the and at the resulted in of β1AR-CT binding to CAL. Mutation of at the to also resulted in a markedly reduced interaction. is known the target binding of the CAL PDZ we a of β1AR-CT shown in most of the mutations resulted in in the of CAL by the The mutation of at the to an a on the interaction, this resulted in a in CAL pull-down by Mutation of at to or also reduced the β1AR-CT/CAL These that the last of β1AR-CT are critical determinants for association with CAL, with the ESKV motif most being close to an binding motif for the CAL PDZ domain. In to the protein pull-down we also the interaction β1AR-CT and CAL via a a of this mutations to the terminal amino of the is shown in Consistent with the pull-down proteins to the CAL PDZ domain to with mutation of the terminal to amino acids such as and in in CAL binding to the In we also the with a protein to NHERF-1, a PDZ protein that to bind to carboxyl-terminal motifs in (12Hall R.A. Premont R.T. Chow C.W. Blitzer J.T. Pitcher J.A. Claing A. Stoffel R.H. Barak L.S. Shenolikar S. Weinman E.J. Grinstein S. Lefkowitz R.J. Nature. 1998; 392: 626-630Crossref PubMed Scopus (516) Google Scholar, R.A. L.S. Premont R.T. Blitzer J.T. M.J. Lefkowitz R.J. S. A. 1998; PubMed Scopus Google Scholar, S. M. 1998; PubMed Scopus Google Scholar). associate with robustly with the β1AR-CT that its terminal to These data the of the interactions of the CAL PDZ domains with carboxyl-terminal and that CAL a for binding to carboxyl termini such as β1AR-CT that in the of the interaction, binding were The binding of CAL PDZ and β1AR-CT at revealing that this interaction is of β1AR with CAL in full-length β1AR associate with CAL in a cellular were with and of β1AR by for CAL co-immunoprecipitation of a complex stimulation with the β-adrenergic receptor the of CAL found to be The pull-down and that the last amino of the β1AR is a critical of the or this also the in cells, we the mutation in the of full-length and we co-immunoprecipitation shown in the mutation reduced the ability of the receptor to CAL the interaction be at of CAL the experiments were using the that were with CAL using a shown in CAL expression in cells, with T. S. T. Res. 2001; PubMed Scopus Google Scholar). β1AR to CAL, the that the receptor the with CAL in of the a of CAL of that a of cellular CAL with β1AR in studies. CAL Intracellular of the of β1AR and CAL, were on with In with β1-adrenergic receptors the receptors were in the plasma as a the cell CAL in the as with the expression of the Golgi-associated protein These data are with observations J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, T. S. T. Res. 2001; PubMed Scopus Google Scholar, A. K. K. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar) that CAL is primarily with the β1AR with CAL, a of β1AR in the co-localization with CAL the β1AR with CAL, the receptors the cell surface with CAL CAL with the β1AR the of CAL on β1AR trafficking to the plasma membrane in a we in the and of cells, and we β1AR surface expression using a which has been J. J. Lau A.G. Hall R.A. Res. 2002; PubMed Scopus Google Scholar). shown in β1AR surface expression reduced by with CAL, suggesting that the interaction CAL and β1AR promotes retention of β1AR within the expression of the β1AR in reduced by with CAL. surface expression of the surface expression of the These data are with the that CAL can regulate β1AR expression on the cell with this being by overexpression of CAL. with CAL to with β1AR and β1AR associates with β1AR via interaction with the carboxyl-terminal ESKV motif of the which is the of β1AR that interacts with other such as PSD-95, and L.A. Tang Y. Miller W.E. Cong M. Lau A.G. Lefkowitz R.J. Hall R.A. J. Biol. Chem. 2000; 275: 38659-38666Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar, 15Xu J. Paquet M. Lau A.G. Wood J.D. Ross C.A. Hall R.A. J. Biol. Chem. 2001; 276: 41310-41317Abstract Full Text Full Text PDF PubMed Scopus (106) Google Scholar, L.A. Martin E.J. Premont R.T. Lefkowitz R.J. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar, Y. D. Biol. 2002; PubMed Scopus Google Scholar). to that PDZ proteins that bind to the target motif bind in a this primarily for the of known PDZ directly the that the association and β1AR the interaction by the pull-down of CAL cell by in the of of which is the of that binds to the shown in the binding of CAL to the β1AR-CT markedly reduced by the of These data reveal that and CAL associate with β1AR-CT in a in is known to be plasma membrane-associated of that to the plasma membrane Neuron. 1998; Full Text Full Text PDF PubMed Scopus Google Scholar). CAL is found in the Golgi J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, T. S. T. Res. 2001; PubMed Scopus Google Scholar, A. K. K. J. Biol. Chem. 2001; 276: Full Text Full Text PDF PubMed Scopus Google Scholar), we and CAL in to regulate β1AR intracellular trafficking and cell surface β1AR in the and of cells, and β1AR surface expression using the shown in overexpression of resulted in a in receptor expression at the cell surface to of β1AR These data are with the that can with CAL to β1AR surface have identified CAL as a novel binding of the β1-adrenergic The interaction CAL and β1AR is specific and on the PDZ domain of CAL and the carboxyl terminus of β1AR. is known that PDZ domain binding is primarily determined by the last few amino acids on the carboxyl termini of target proteins (17Hung A.Y. Sheng M. J. Biol. Chem. 2002; 277: 5699-5702Abstract Full Text Full Text PDF PubMed Scopus (584) Google Scholar). CAL has been found to associate with proteins other β1AR J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar), M. A. J. Biol. Chem. 2003; Full Text Full Text PDF PubMed Scopus Google Scholar), A. M. Neuron. 2002; Full Text Full Text PDF PubMed Scopus Google Scholar), and protein and T. S. T. Res. 2001; PubMed Scopus Google Scholar). The last amino acids of proteins are and protein and of motifs to the which is of the is a amino at the carboxyl and is amino β1AR in the motif which is to the motifs found in the other proteins that associate with CAL. mutations that we to the ESKV with the of to at the resulted in in CAL that ESKV is close to the binding motif for the CAL PDZ domain. that overexpression of CAL resulted in the intracellular of β1AR and a in the of β1AR on the cell surface. have found that PDZ proteins can modulate β1AR we that interaction with inhibits β1AR whereas association with β1AR the internalization of the receptor L.A. Tang Y. Miller W.E. Cong M. Lau A.G. Lefkowitz R.J. Hall R.A. J. Biol. 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Chem. 1999; Full Text Full Text PDF PubMed Scopus Google Scholar). we that the retention and of β1AR in the is of CAL of β1AR anterograde trafficking the to the cell surface. to that CAL β1AR trafficking, CAL has been to play a in the of both J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar, J. H. J. Biol. Chem. 2004; Full Text Full Text PDF PubMed Scopus (106) Google Scholar) and T. S. T. Res. 2001; PubMed Scopus Google Scholar) the Golgi to the plasma membrane. a transmembrane receptor for found to co-localization in the Golgi with CAL T. S. T. Res. 2001; PubMed Scopus Google Scholar). In the of CFTR, a transmembrane CAL found to the cell surface expression of in by the rate of anterograde trafficking to the plasma membrane J. M. J. M. M. J. Biol. Chem. 2002; 277: Full Text Full Text PDF PubMed Scopus Google Scholar). The Golgi is an in the for the of complex on proteins and and for the sorting of proteins and to their M.G. Biol. 1998; Full Text PDF PubMed Scopus Google Scholar). CAL play a in the regulation of the of transmembrane thereby the formation of transmembrane proteins for to the cell surface. we have found that of β1AR in the regulates of the receptor to the plasma membrane J. J. Lau A.G. Hall R.A. Res. 2002; PubMed Scopus Google Scholar), an that has been for other transmembrane proteins D. 2003; PubMed Scopus Google Scholar, Rev. 2002; PubMed Scopus Google Scholar). Golgi-associated PDZ proteins such as CAL as to regulate the and surface expression of specific transmembrane proteins such as β1AR. The β1AR carboxyl-terminal motif associates with CAL also with PDZ such as L.A. Tang Y. Miller W.E. Cong M. Lau A.G. Lefkowitz R.J. Hall R.A. J. Biol. Chem. 2000; 275: 38659-38666Abstract Full Text Full Text PDF PubMed Scopus (136) Google Scholar), J. Paquet M. Lau A.G. Wood J.D. Ross C.A. Hall R.A. J. Biol. 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M.G. S. A. 1998; PubMed Scopus Google Scholar, C.A. D. Biol. 2000; Full Text Full Text PDF PubMed Scopus Google Scholar). The interaction of β1AR with PDZ in to cell regulation of β1AR trafficking and In we have found that β1AR interacts via its carboxyl terminus with the PDZ domain of CAL, a Golgi-associated protein that is known to with proteins involved in the regulation of In both and the association of β1AR with CAL found to be on the carboxyl-terminal motif of the terminal valine The interaction of β1AR with CAL resulted in the retention and of β1AR in the These observations for the of PDZ interactions in β1AR trafficking through the complex to the plasma membrane and have for the regulation of for other transmembrane proteins that are known to with Lefkowitz for the B. for the and Sheng of for the also Lau and for