The tight junction protein ZO-1 establishes a link between the transmembrane protein occludin and the actin cytoskeleton.
The tight junction protein ZO-1 belongs to a family of multidomain proteins known as the membrane-associated guanylate kinase homologs (MAGUKs). ZO-1 has been demonstrated to interact with the transmembrane protein occludin, a second tight junction-specific MAGUK, ZO-2, and F-actin, although the nature and functional significance of these interactions is poorly understood. To further elucidate the role of ZO-1 within the epithelial tight junction, we have introduced epitope-tagged fragments of ZO-1 into cultured MDCK cells and identified domains critical for the interaction with ZO-2, occludin, and F-actin. A combination of in vitro and in vivo binding assays indicate that both ZO-2 and occludin interact with specific domains within the N-terminal (MAGUK-like) half of ZO-1, whereas the unique proline-rich C-terminal half of ZO-1 cosediments with F-actin. Consistent with these observations, we found that a construct encoding the N-terminal half of ZO-1 is specifically associated with tight junctions, whereas the unique C-terminal half of ZO-1 is distributed over the entire lateral surface of the plasma membrane and other actin-rich structures. In addition, we have identified a 244-amino acid domain within the N-terminal half of ZO-1, which is required for the stable incorporation of ZO-1 into the junctional complex of polarized MDCK cells. These observations suggest that one functional role of ZO-1 is to organize components of the tight junction and link them to the cortical actin cytoskeleton.
Fanning
A S
AS
Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut 06510, USA. alan.fanning@yale.edu
Jameson
B J
BJ
Jesaitis
L A
LA
Anderson
J M
JM
D000199:Actins / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D003599:Cytoskeleton / Q000378:metabolism*; D017931:DNA Primers; D004285:Dogs; D008565:Membrane Proteins / Q000737:chemistry / Q000378:metabolism*; D062793:Occludin; D010750:Phosphoproteins / Q000737:chemistry / Q000378:metabolism*; D062826:Zonula Occludens-1 Protein
D000199:Actins; D017931:DNA Primers; D008565:Membrane Proteins; D062793:Occludin; D010750:Phosphoproteins; D062826:Zonula Occludens-1 Protein