title: alpha B-crystallin is a cytoplasmic interaction partner of the kidney-specific cadherin-16.
abstract: The Ca(2+)-dependent membrane-spanning classical cadherins bind directly to cytosolic catenins. This cadherin-catenin interaction is known to be critical for the fundamental role of cadherins in cell-cell adhesion. The small subfamily of the 7D-cadherins, however, cannot interact with catenins due to their highly truncated cytoplasmic tail. Thus far, no cytoplasmic interaction partner for the 7D-cadherins has been described. With the use of the cytoplasmic domain of the Ksp (kidney-specific)-cadherin, which belongs to the family of 7D-cadherins, as bait in affinity chromatography with human kidney lysates, the small heat-shock protein alpha B-crystallin was identified by matrix-assisted laser desorption/ionization-time-of-flight analysis as a cytosolic binding partner of Ksp-cadherin. This interaction was verified by co-immunoprecipitation analysis. With the use of overlapping peptides representing the entire alpha B-crystallin molecule, the N-terminal part of alpha B-crystallin, which does not possess chaperone activity, was identified as responsible for the binding to Ksp-cadherin. This interaction was found to be specific since only the cytoplasmic domain of Ksp-cadherin, but not LI (liver-intestine)-cadherin (another member of the 7D-cadherin family), interacted with alpha B-crystallin. In the human kidney, both alpha B-crystallin and Ksp-cadherin co-localize to cells of the collecting duct. They also co-localize with the actin cytoskeleton and co-precipitate with the latter. These findings suggest that the interaction of Ksp-cadherin with alpha B-crystallin is important for the connection of Ksp-cadherin to the cytoskeleton and thus for maintaining tissue integrity in the kidney.
authors.affiliation: Section for Transplantation Immunology and Immunohematology, Center for Medical Research, University Medical Clinic, Waldhörnlestrasse 22, D-72072 Tübingen, Germany.
authors.forename: Cornelia
authors.initials: C
authors.lastname: Thedieck
authors.forename: Hubert
authors.initials: H
authors.lastname: Kalbacher
authors.forename: Ulrich
authors.initials: U
authors.lastname: Kratzer
authors.forename: Reiner
authors.initials: R
authors.lastname: Lammers
authors.forename: Stefan
authors.initials: S
authors.lastname: Stevanovic
authors.forename: Gerd
authors.initials: G
authors.lastname: Klein
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D002417:Cattle; D003593:Cytoplasm / Q000737:chemistry / Q000378:metabolism; D006801:Humans; D007668:Kidney / Q000737:chemistry / Q000378:metabolism*; D008969:Molecular Sequence Data; D025941:Protein Interaction Mapping; D038203:alpha-Crystallin B Chain / Q000032:analysis / Q000378:metabolism*
chemical_list: C114483:CDH16 protein, human; D015820:Cadherins; D038203:alpha-Crystallin B Chain