The WW domain of Yes-associated protein binds a proline-rich ligand that differs from the consensus established for Src homology 3-binding modules.

Abstract

The WW domain has previously been described as a motif of 38 semiconserved residues found in seemingly unrelated proteins, such as dystrophin, Yesassociated protein (YAP), and two transcriptional regulators, Rsp-5 and FE65. The molecular function of the WW domain has been unknown until this time. Using a functional screen of a cDNA expression library, we have identified two putative ligands of the WW domain of YAP, which we named WBP-1 and WBP-2. Peptide sequence comparison between the two partial clones revealed a homologous region consisting of a proline-rich domain followed by a tyrosine residue (with the shared sequence PPPPY), which we shall call the PY motif. Binding assays and site-specific mutagenesis have shown that the PY motif binds with relatively high affinity and specificity to the WW domain of YAP, with the preliminary consensus XPPXY being critical for binding. Herein, we have implicated the WWV domain with a role in mediating protein-protein interactions, as a variant of the paradigm set by Src homology 3 domains and their proline-rich ligands.The progressive elucidation of the function of Src homology (SH) 2 and SH3 domains, in addition to the identification of their ligands, has in the recent years spawned an era of remarkable developments in the fields of signal transduction and molecular oncology (1-3). As a result of this trend, two new domains, the pleckstrin homology domain and the phosphotyrosine interaction domain, have been identified and are extensively studied in the context of signaling pathways (4-8).The recognition of the existence of modular protein-binding domains has proven to be critical in understanding the intricacies of signal transduction where a variety of events occur. For example, proteins transiently interact with their upstream and downstream partners, substrates are brought into proximity of their catalytic centers, or proteins are localized to their subcellular compartments through the interaction of these domains with their ligands (9).The SH2 domain was first described as a conserved sequence of 100 amino acids in the noncatalytic domain of cytoplasmic tyrosine kinases such as Src and Fps, but it rapidly became recognized in other molecules involved in signaling pathways and cellular transformation including Crk, Ras-GAP, and phospholipase C-,y. When the SH2 domain was later shown to bind with high affinity to phosphotyrosine residues, it was quickly realized that the SH2 domain represented a means by which many molecules sharing a common signaling pathway may associate to regulate signal propagation from the extracellular environment into the cell and its nucleus (10). In contrast, the SH3 domain was originally identified as a 50-amino-acid-long region of homology shared between the Crk and Src oncogene products and phospholipase C-,y (11, 12).Various studies have shown that SH3 domains may mediate protein localization to the plasma membrane or the cytoskeleton, as exemplified by the interaction between Grb2 and Sos that transduces signals from cell surfa...

Human Nedd4 interacts with the human epithelial Na+ channel: WW3 but not WW1 binds to Na+-channel subunits

“…This residue is therefore critical for correct regulation of the Na + channel. Other studies have reported that a subset of WWPs, including Nedd4, require a tyrosine in the binding sites of their substrates [17,23]. Recently Lu et al [33] reported binding of murine Nedd4 and Pin1 WW domains to phosphoserine-and phosphothreonine-containing peptides.…”

“…Such regions can mediate binding to WW and SH3 (Src homology 3) domains, small hydrophobic protein domains (38 and 60 amino acids respectively) that bind to proline-containing motifs. WW domains bind to ligands containing either PPXY [17] or PPLP [18,19] sequences, whereas the minimal binding motif for SH3 domains is PXXP [20].…”

Y65C Missense Mutation in the WW Domain of the Golabi-Ito-Hall Syndrome Protein PQBP1 Affects Its Binding Activity and Deregulates Pre-mRNA Splicing

“…The WW domain is a well characterized protein module that mediates specific protein-protein interactions with ligands that contain short proline-rich motifs (15)(16)(17). The domain is composed of 38 amino acids, and it is one of the smallest among modular protein domains.…”

MAGUIN, a Novel Neuronal Membrane-associated Guanylate Kinase-interacting Protein

“…The GK domain of S-SCAM is shorter than that of PSD-95/SAP90. The WW domain is a protein-interacting module binding a proline-rich sequence (25). The recent version of simple modular architecture research tool recognizes an additional PDZ domain at the N terminus of S-SCAM (26).…”