The unique-5 and -6 motifs of ZO-1 regulate tight junction strand localization and scaffolding properties.
The proper cellular location and sealing of tight junctions is assumed to depend on scaffolding properties of ZO-1, a member of the MAGUK protein family. ZO-1 contains a conserved SH3-GUK module that is separated by a variable region (unique-5), which in other MAGUKs has proven regulatory functions. To identify motifs in ZO-1 critical for its putative scaffolding functions, we focused on the SH3-GUK module including unique-5 (U5) and unique-6 (U6), a motif immediately C-terminal of the GUK domain. In vitro binding studies reveal U5 is sufficient for occludin binding; U6 reduces the affinity of this binding. In cultured cells, U5 is required for targeting ZO-1 to tight junctions and removal of U6 results in ectopically displaced junction strands containing the modified ZO-1, occludin, and claudin on the lateral cell membrane. These results provide evidence that ZO-1 can control the location of tight junction transmembrane proteins and reveals complex protein binding and targeting signals within its SH3-U5-GUK-U6 region. We review these findings in the context of regulated scaffolding functions of other MAGUK proteins.
Fanning
Alan S
AS
Department of Cell and Molecular Physiology, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599-7545, USA. alan.fanning@med.unc.edu
Little
Brent P
BP
Rahner
Christoph
C
Utepbergenov
Darkhan
D
Walther
Zenta
Z
Anderson
James M
JM
D020816:Amino Acid Motifs; D000818:Animals; D001665:Binding Sites; D004285:Dogs; D005614:Freeze Fracturing; D008565:Membrane Proteins / Q000737:chemistry* / Q000378:metabolism*; D062793:Occludin; D010455:Peptides / Q000378:metabolism; D010750:Phosphoproteins / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport; D019108:Tight Junctions / Q000378:metabolism*; D019076:Transgenes; D062826:Zonula Occludens-1 Protein; D018909:src Homology Domains
D008565:Membrane Proteins; D062793:Occludin; D010455:Peptides; D010750:Phosphoproteins; D062826:Zonula Occludens-1 Protein