The Tight Junction Protein ZO-2 Contains Three PDZ (PSD-95Discs-LargeZO-1) Domains and an Alternatively Spliced Region

Abstract

The complete cDNA sequence for canine ZO-2, a tight junction-specific protein, is presented. A single open reading frame encodes a polypeptide of 1,174 amino acids with a predicted molecular mass of 132,085 daltons. As noted previously (1), ZO-2 is a member of the membraneassociated guanylate kinase-containing (MAGUK) protein family, a family which includes an additional tight junction-associated protein, ZO-1. These proteins contain a region homologous to guanylate kinase, an SH3 domain, and variable numbers of PSD-95/discs-large/ ZO-1 (PDZ) domains, shown to be involved in proteinprotein interactions. ZO-2 and ZO-1 contain three PDZ domains in the N-terminal half of the molecule. Between the first and second PDZ domains, ZO-2 displays a basic region (pI ‫؍‬ 10.27) containing 22% arginine residues. Both ZO-1 and ZO-2 have proline-rich C-terminal regions that are not homologous to other MAGUK family members. Sequence analysis of multiple ZO-2 cDNAs reveals a 36-amino acid domain in this C-terminal region present in only some of the cDNAs. Overall, ZO-2 is highly homologous to ZO-1, showing 51% amino acid identity; however, the C-terminal ends of the molecules show only 25% amino acid identity. This suggests that the C-terminal ends of ZO-1 and ZO-2 have different functions.Several molecular constituents of the tight junction have been identified. These include ZO-1 (2), cingulin (3), ZO-2 (1, 4), 7H6 (5), Rab3B (6), and occludin (7). The presence of other proteins at the tight junction, including spectrin (8, 9), another Rab protein (Rab13) (10), and p130 (11), has been implicated but not confirmed.The complete mouse (12) and human (13) protein and cDNA sequences of ZO-1 have been published. A partial sequence for ZO-2 has also been characterized (1). Analyses of these sequences indicate that ZO-1 and ZO-2 share significant homology with each other and with several other proteins, including the lethal(1)discs-large-1 (dlg) tumor suppressor gene product (dlg-A) of Drosophila (14), erythrocyte membrane-associated p55 (15), and PSD-95/SAP90, a protein found at brain presynaptic membranes (16,17). These proteins share several conserved regions, including a region homologous to guanylate kinase (GUK), 1 an enzyme which converts GMP to GDP, a single src homology (SH3) domain, hypothesized to be involved in protein-protein interactions necessary for signal transduction (18,19), and a variable number of N-terminal repeats termed PDZ domains (from PSD-95, discs-large, ZO-1), shown to bind integral plasma membrane proteins (20 -23). As all proteins in this group are associated with the plasma membrane, they have collectively been termed the MAGUK family (membrane-associated guanylate kinase-containing) (24).ZO-1 and ZO-2 are different from other family members but similar to each other in that they display C-terminal acidic and proline-rich regions (1, 13). ZO-1 also contains an alternatively spliced region, termed the ␣ motif, in the C-terminal region (25,26). The exact function of this splice domain remains unknown. Her...

Isolation and characterization of mammalian homologues of Caenorhabditis elegans lin-7: localization at cell-cell junctions

“…However, in contrast to synaptic junctions, the molecular mechanism of the assembly of the components of tight and adherens junctions is not clear. Tight and adherens junctions have several PDZ domain-containing proteins, such as ZO-1, -2, -3, SAP97/hDLG, afadin, and neurabin-11/spinophilin, which may function as scaffolding proteins (Itoh et al, 1993;Willott et al, 1993;Lue et al, 1994;Muller et al, 1995;Beatch et al, 1996;Allen et al, 1997;Mandai et al, 1997;Haskins et al, 1998;Reuver and Garner, 1998;Satoh et al, 1998). The vulval induction in Caenorhabditis elegans (C. elegans) is a well characterized example of the intercellular signaling between non-neuronal cells.…”

Angiopoietin-1 reduces vascular endothelial growth factor-induced brain endothelial permeability via upregulation of ZO-2

“…ZO-1 was the first protein associated with tight junctions of endothelial cells and well characterized tight junction protein (10). Tight junction associated protein ZO-2 interacts with ZO-1 and binds directly to the COOH-terminal cytoplasmic tail of the transmembrane protein occludin (11).…”

hScrib interacts with ZO‐2 at the cell–cell junctions of epithelial cells

“…Like other MAGUKs, ZO-2 contains three PDZ domains, a SH3 domain, and a GUK domain devoided of enzymatic activity [4]. ZO-2 interacts with several components of the TJs, including ZO-1 [2,5], 4.1R protein [6], cingulin [7], occludin [5], claudins [8] and actin [9].…”