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hCASK and hDlg associate in epithelia, and their src homology 3 and guanylate kinase domains participate in both intramolecular and intermolecular interactions.

Authors
  • Nix, S L
  • Chishti, A H
  • Anderson, J M
  • Walther, Z
Type
Published Article
Journal
The Journal of biological chemistry
Publication Date
Dec 29, 2000
Volume
275
Issue
52
Pages
41192–41200
Identifiers
PMID: 10993877
Source
Medline
License
Unknown

Abstract

Membrane-associated guanylate kinase (MAGUK) proteins act as molecular scaffolds organizing multiprotein complexes at specialized regions of the plasma membrane. All MAGUKs contain a Src homology 3 (SH3) domain and a region homologous to yeast guanylate kinase (GUK). We showed previously that one MAGUK protein, human CASK (hCASK), is widely expressed and associated with epithelial basolateral plasma membranes. We now report that hCASK binds another MAGUK, human discs large (hDlg). Immunofluorescence microscopy demonstrates that hCASK and hDlg colocalize at basolateral membranes of epithelial cells in small and large intestine. These proteins co-precipitate from lysates of an intestinal cell line, Caco-2. The GUK domain of hCASK binds the SH3 domain of hDlg in both yeast two-hybrid and fusion protein binding assays, and it is required for interaction with hDlg in transfected HEK293 cells. In addition, the SH3 and GUK domains of each protein participate in intramolecular binding that in vitro predominates over intermolecular binding. The SH3 and GUK domains of human p55 display the same interactions in yeast two-hybrid assays as those of hCASK. Not all SH3-GUK interactions among these MAGUKs are permissible, however, implying specificity to SH3-GUK interactions in vivo. These results suggest MAGUK scaffold assembly may be regulated through effects on intramolecular SH3-GUK binding.

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