title: PDZ motifs in PTP-BL and RIL bind to internal protein segments in the LIM domain protein RIL.
abstract: The specificity of protein-protein interactions in cellular signaling cascades is dependent on the sequence and intramolecular location of distinct amino acid motifs. We used the two-hybrid interaction trap to identify proteins that can associate with the PDZ motif-rich segment in the protein tyrosine phosphatase PTP-BL. A specific interaction was found with the Lin-11, Isl-1, Mec-3 (LIM) domain containing protein RIL. More detailed analysis demonstrated that the binding specificity resides in the second and fourth PDZ motif of PTP-BL and the LIM domain in RIL. Immunohistochemistry on various mouse tissues revealed a submembranous colocalization of PTP-BL and RIL in epithelial cells. Remarkably, there is also an N-terminal PDZ motif in RIL itself that can bind to the RIL-LIM domain. We demonstrate here that the RIL-LIM domain can be phosphorylated on tyrosine in vitro and in vivo and can be dephosphorylated in vitro by the PTPase domain of PTP-BL. Our data point to the presence of a double PDZ-binding interface on the RIL-LIM domain and suggest tyrosine phosphorylation as a regulatory mechanism for LIM-PDZ associations in the assembly of multiprotein complexes. These findings are in line with an important role of PDZ-mediated interactions in the shaping and organization of submembranous microenvironments of polarized cells.
authors.affiliation: Department of Cell Biology and Histology, Institute of Cellular Signaling, University of Nijmegen, the Netherlands.
authors.forename: E
authors.initials: E
authors.lastname: Cuppen
authors.forename: H
authors.initials: H
authors.lastname: Gerrits
authors.forename: B
authors.initials: B
authors.lastname: Pepers
authors.forename: B
authors.initials: B
authors.lastname: Wieringa
authors.forename: W
authors.initials: W
authors.lastname: Hendriks
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites / Q000235:genetics; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004848:Epithelium / Q000378:metabolism; D006801:Humans; D007150:Immunohistochemistry; D060588:LIM Domain Proteins; D051379:Mice; D008840:Microfilament Proteins; D008969:Molecular Sequence Data; D010766:Phosphorylation; D011485:Protein Binding; D017027:Protein Tyrosine Phosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D013379:Substrate Specificity
chemical_list: D004268:DNA-Binding Proteins; D060588:LIM Domain Proteins; D008840:Microfilament Proteins; C486247:PDLIM4 protein, human; C486248:Pdlim4 protein, mouse; C091504:Pdlim4 protein, rat; D017027:Protein Tyrosine Phosphatases