hDLG/SAP97, a member of the MAGUK protein family, is a novel caspase target during cell-cell detachment in apoptosis.
Cell-cell detachment is one of the hallmarks of apoptosis. To date, several transmembrane and plaque proteins from tight and adherent junctions have been characterised as caspase targets during apoptosis. Human discs large protein (hDLG)/SAP97 is a member of the membrane-associated guanylate kinase (MAGUK) family of proteins, localised at the adherent junctions of epithelial and endothelial cells, that is required for adherens junction assembly and differentiation. Here, hDLG is shown to be a caspase target during UV irradiation and staurosporine (STS)-induced apoptosis in HaCaT and CaCo-2 cells. Immunohistological data show a rapid loss of hDLG localisation at the sites of cell-cell contacts, preceding actual cell-cell detachment. In vitro experiments revealed cleavages at multiple sites located in the N-terminal half of the protein by caspase-3 only. Using Ala scanning mutagenesis, one cleavage site with an unusual recognition sequence for the executioner caspases (QSVD427/N) was identified. These data suggest that caspase-mediated cleavage of hDLG, and other MAGUKs, and their removal from sites of cell-cell contacts is an early step in the disruption of adherens junctions and dismantling of cell-cell contacts during apoptosis.
Gregorc
Uros
U
Department of Biochemistry and Molecular Biology, J. Stefan Institute, SI-1000 Ljubljana, Slovenia.
Ivanova
Saska
S
Thomas
Miranda
M
Turk
Vito
V
Banks
Lawrence
L
Turk
Boris
B
D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology*; D017209:Apoptosis / Q000187:drug effects / Q000502:physiology* / Q000528:radiation effects; D001483:Base Sequence; D002460:Cell Line; D017931:DNA Primers; D000074288:Discs Large Homolog 1 Protein; D006801:Humans; D008565:Membrane Proteins / Q000502:physiology*; D019311:Staurosporine / Q000494:pharmacology; D013347:Subcellular Fractions / Q000378:metabolism; D019108:Tight Junctions; D014466:Ultraviolet Rays
D048868:Adaptor Proteins, Signal Transducing; C513314:DLG1 protein, human; D017931:DNA Primers; D000074288:Discs Large Homolog 1 Protein; D008565:Membrane Proteins; D019311:Staurosporine