title: Oligomerization of NHERF-1 and NHERF-2 PDZ domains: differential regulation by association with receptor carboxyl-termini and by phosphorylation.
abstract: PDZ domains bind to the carboxyl-termini of target proteins, and some PDZ domains are capable of oligomerization to facilitate the formation of intracellular signaling complexes. The Na(+)/H(+) exchanger regulatory factor (NHERF-1; also called "EBP50") and its relative NHERF-2 (also called "E3KARP", "SIP-1", and "TKA-1") both have two PDZ domains. We report here that the PDZ domains of NHERF-1 and NHERF-2 bind specifically to each other but not to other PDZ domains. Purified NHERF-2 PDZ domains associate with each other robustly in the absence of any associated proteins, but purified NHERF-1 PDZ domains associate with each other only weakly when examined alone. The oligomerization of the NHERF-1 PDZ domains is greatly facilitated when they are bound with carboxyl-terminal ligands, such as the carboxyl-termini of the beta(2)-adrenergic receptor or the platelet-derived growth factor receptor. Oligomerization of full-length NHERF-1 is also enhanced by mutation of serine 289 to aspartate (S289D), which mimics the phosphorylated form of NHERF-1. Co-immunoprecipitation experiments with differentially tagged versions of the NHERF proteins reveal that NHERF-1 and NHERF-2 form homo- and hetero-oligomers in a cellular context. A point-mutated version of NHERF-1 (S289A), which cannot be phosphorylated on serine 289, exhibits a reduced capacity for co-immunoprecipitation from cells. These studies reveal that both NHERF-1 and NHERF-2 can oligomerize, which may facilitate NHERF-mediated formation of cellular signaling complexes. These studies furthermore reveal that oligomerization of NHERF-1, but not NHERF-2, is highly regulated by association with other proteins and by phosphorylation.
authors.affiliation: Department of Pharmacology, Rollins Research Center, Emory University, School of Medicine, Atlanta, Georgia 30322, USA.
authors.forename: A G
authors.initials: AG
authors.lastname: Lau
authors.forename: R A
authors.initials: RA
authors.lastname: Hall
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000235:genetics / Q000378:metabolism*; D029721:Drosophila Proteins; D006801:Humans; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism; D010446:Peptide Fragments / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation; D017434:Protein Structure, Tertiary / Q000235:genetics; D011817:Rabbits; D017479:Receptors, Platelet-Derived Growth Factor / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D012694:Serine / Q000235:genetics; D017923:Sodium-Hydrogen Exchangers / Q000235:genetics / Q000378:metabolism*; D014162:Transfection; D062826:Zonula Occludens-1 Protein
chemical_list: D002352:Carrier Proteins; D003598:Cytoskeletal Proteins; D029721:Drosophila Proteins; D019476:Insect Proteins; D008565:Membrane Proteins; D009419:Nerve Tissue Proteins; D010446:Peptide Fragments; D010750:Phosphoproteins; D011993:Recombinant Fusion Proteins; C081517:SLC9A2 protein, human; D017923:Sodium-Hydrogen Exchangers; C569042:TJP1 protein, human; D062826:Zonula Occludens-1 Protein; C118488:dlt protein, Drosophila; C033652:postsynaptic density proteins; C093376:sodium-hydrogen exchanger regulatory factor; D012694:Serine; D017479:Receptors, Platelet-Derived Growth Factor