Limits...
Direct binding of three tight junction-associated MAGUKs, ZO-1, ZO-2, and ZO-3, with the COOH termini of claudins.

Itoh M, Furuse M, Morita K, Kubota K, Saitou M, Tsukita S - J. Cell Biol. (1999)

Bottom Line: Claudin-1 and -2 were concentrated at cell-cell borders in an elaborate network pattern, to which endogenous ZO-1 was recruited.When ZO-2 or ZO-3 were further transfected, both were recruited to the claudin-based networks together with endogenous ZO-1.Detailed analyses showed that ZO-2 and ZO-3 are recruited to the claudin-based networks through PDZ2 (ZO-2 or ZO-3)/PDZ2 (endogenous ZO-1) and PDZ1 (ZO-2 or ZO-3)/COOH-terminal YV (claudins) interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.

ABSTRACT
ZO-1, ZO-2, and ZO-3, which contain three PDZ domains (PDZ1 to -3), are concentrated at tight junctions (TJs) in epithelial cells. TJ strands are mainly composed of two distinct types of four-transmembrane proteins, occludin, and claudins, between which occludin was reported to directly bind to ZO-1/ZO-2/ZO-3. However, in occludin-deficient intestinal epithelial cells, ZO-1/ZO-2/ZO-3 were still recruited to TJs. We then examined the possible interactions between ZO-1/ZO-2/ZO-3 and claudins. ZO-1, ZO-2, and ZO-3 bound to the COOH-terminal YV sequence of claudin-1 to -8 through their PDZ1 domains in vitro. Then, claudin-1 or -2 was transfected into L fibroblasts, which express ZO-1 but not ZO-2 or ZO-3. Claudin-1 and -2 were concentrated at cell-cell borders in an elaborate network pattern, to which endogenous ZO-1 was recruited. When ZO-2 or ZO-3 were further transfected, both were recruited to the claudin-based networks together with endogenous ZO-1. Detailed analyses showed that ZO-2 and ZO-3 are recruited to the claudin-based networks through PDZ2 (ZO-2 or ZO-3)/PDZ2 (endogenous ZO-1) and PDZ1 (ZO-2 or ZO-3)/COOH-terminal YV (claudins) interactions. In good agreement, PDZ1 and PDZ2 domains of ZO-1/ZO-2/ZO-3 were also recruited to claudin-based TJs, when introduced into cultured epithelial cells. The possible molecular architecture of TJ plaque structures is discussed.

Show MeSH

Related in: MedlinePlus

Schematic drawing of the molecular architecture of the TJ plaque. TJ strands are represented as linear co-polymers of claudins and occludin with short and long COOH-terminal tails, respectively. ZO-1, ZO-2, and ZO-3 are directly associated with the COOH termini of claudins at their PDZ1 domains. These molecules are depicted here to interact with occludin at their GUK domains. ZO-1/ZO-2 and ZO-1/ZO-3 heterodimers are depicted to be formed through direct PDZ2/PDZ2 interaction, but the possibility cannot be completely excluded that these interaction requires some linker protein. It remains unclear whether ZO-1, ZO-2, and ZO-3 exist as monomers and/or homodimers (not depicted here), except that ZO-1/ZO-1 homodimers were reported to be undetectable. The COOH-terminal region of ZO-1 and ZO-2 has a binding affinity to actin filaments to function as cross-linkers between TJ strands and actin filaments. The interaction between ZO-3 and actin filaments has not yet been examined.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2168087&req=5

Figure 11: Schematic drawing of the molecular architecture of the TJ plaque. TJ strands are represented as linear co-polymers of claudins and occludin with short and long COOH-terminal tails, respectively. ZO-1, ZO-2, and ZO-3 are directly associated with the COOH termini of claudins at their PDZ1 domains. These molecules are depicted here to interact with occludin at their GUK domains. ZO-1/ZO-2 and ZO-1/ZO-3 heterodimers are depicted to be formed through direct PDZ2/PDZ2 interaction, but the possibility cannot be completely excluded that these interaction requires some linker protein. It remains unclear whether ZO-1, ZO-2, and ZO-3 exist as monomers and/or homodimers (not depicted here), except that ZO-1/ZO-1 homodimers were reported to be undetectable. The COOH-terminal region of ZO-1 and ZO-2 has a binding affinity to actin filaments to function as cross-linkers between TJ strands and actin filaments. The interaction between ZO-3 and actin filaments has not yet been examined.

Mentions: These findings led to the molecular architecture model for the TJ plaque shown schematically in Fig. 11. In this scheme, TJ strands are represented as linear co-polymers of occludin and various species of claudin (Furuse et al. 1999; Tsukita and Furuse 1999). It is likely that these kinds of co-polymers present large linear clusters of YV sequences toward the cytoplasm, which may strongly attract cytoplasmic proteins containing PDZ domains with high affinity to the COOH-terminal sequence of claudins. Since the PDZ1 domains, but not PDZ2 or PDZ3 domains, of ZO-1, ZO-2, and ZO-3 has an affinity to the COOH-terminal sequence of claudins, they are recruited to TJ strands (see Fig. 11). In good agreement, GFP-fusion proteins with PDZ1 domains of ZO-1/ZO-2/ZO-3 were recruited to TJs in MDCK cells (see Fig. 10). These three MAGUKs were also reported to bind to the COOH-terminal 150–amino acid sequence of the cytoplasmic domain of occludin (Furuse et al. 1994; Haskins et al. 1998; Itoh et al. 1999). Since occludin does not end in valine, the molecular basis for the occludin-MAGUKs interaction may be different from that of the claudin-MAGUKs interaction. In ZO-1, the GUK domain was reported to be responsible for occludin-ZO-1 binding (Fanning et al. 1998). If this is the case also for ZO-2 and ZO-3, each MAGUK molecule can bind to occludin and claudins simultaneously through GUK and PDZ1 domains, respectively. Furthermore, to complicate the molecular architecture model for the TJ plaque, ZO-1/ZO-2 and ZO-1/ZO-3 interactions were also reported, suggesting the existence of heterodimers of MAGUKs (Fanning et al. 1998; Haskins et al. 1998; Itoh et al. 1999). The results of this and previous studies revealed that these interactions were dependent on the PDZ2/PDZ2 interaction (Itoh et al. 1999). GFP-fusion proteins with PDZ2 domains of ZO-1/ZO-2/ZO-3 were recruited to TJs in MDCK cells (see Fig. 10), probably through this PDZ2/PDZ2 interaction. ZO-1 does not form homodimers reportedly (Fanning et al. 1998), but no information is available regarding the homodimers of ZO-2 and ZO-3. Furthermore, it remains unclear whether ZO-1, ZO-2, and ZO-3 exist in the TJ plaque as monomers. On the other hand, the COOH-terminal region of ZO-1 and ZO-2 directly binds to actin filaments (Itoh et al. 1997, Itoh et al. 1999; Fanning et al. 1998). These findings indicated that ZO-1, ZO-2 and ZO-3 function as scaffolds of the TJ plaque to cross-link TJ strands to the actin-based cytoskeleton.


Direct binding of three tight junction-associated MAGUKs, ZO-1, ZO-2, and ZO-3, with the COOH termini of claudins.

Itoh M, Furuse M, Morita K, Kubota K, Saitou M, Tsukita S - J. Cell Biol. (1999)

Schematic drawing of the molecular architecture of the TJ plaque. TJ strands are represented as linear co-polymers of claudins and occludin with short and long COOH-terminal tails, respectively. ZO-1, ZO-2, and ZO-3 are directly associated with the COOH termini of claudins at their PDZ1 domains. These molecules are depicted here to interact with occludin at their GUK domains. ZO-1/ZO-2 and ZO-1/ZO-3 heterodimers are depicted to be formed through direct PDZ2/PDZ2 interaction, but the possibility cannot be completely excluded that these interaction requires some linker protein. It remains unclear whether ZO-1, ZO-2, and ZO-3 exist as monomers and/or homodimers (not depicted here), except that ZO-1/ZO-1 homodimers were reported to be undetectable. The COOH-terminal region of ZO-1 and ZO-2 has a binding affinity to actin filaments to function as cross-linkers between TJ strands and actin filaments. The interaction between ZO-3 and actin filaments has not yet been examined.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2168087&req=5

Figure 11: Schematic drawing of the molecular architecture of the TJ plaque. TJ strands are represented as linear co-polymers of claudins and occludin with short and long COOH-terminal tails, respectively. ZO-1, ZO-2, and ZO-3 are directly associated with the COOH termini of claudins at their PDZ1 domains. These molecules are depicted here to interact with occludin at their GUK domains. ZO-1/ZO-2 and ZO-1/ZO-3 heterodimers are depicted to be formed through direct PDZ2/PDZ2 interaction, but the possibility cannot be completely excluded that these interaction requires some linker protein. It remains unclear whether ZO-1, ZO-2, and ZO-3 exist as monomers and/or homodimers (not depicted here), except that ZO-1/ZO-1 homodimers were reported to be undetectable. The COOH-terminal region of ZO-1 and ZO-2 has a binding affinity to actin filaments to function as cross-linkers between TJ strands and actin filaments. The interaction between ZO-3 and actin filaments has not yet been examined.
Mentions: These findings led to the molecular architecture model for the TJ plaque shown schematically in Fig. 11. In this scheme, TJ strands are represented as linear co-polymers of occludin and various species of claudin (Furuse et al. 1999; Tsukita and Furuse 1999). It is likely that these kinds of co-polymers present large linear clusters of YV sequences toward the cytoplasm, which may strongly attract cytoplasmic proteins containing PDZ domains with high affinity to the COOH-terminal sequence of claudins. Since the PDZ1 domains, but not PDZ2 or PDZ3 domains, of ZO-1, ZO-2, and ZO-3 has an affinity to the COOH-terminal sequence of claudins, they are recruited to TJ strands (see Fig. 11). In good agreement, GFP-fusion proteins with PDZ1 domains of ZO-1/ZO-2/ZO-3 were recruited to TJs in MDCK cells (see Fig. 10). These three MAGUKs were also reported to bind to the COOH-terminal 150–amino acid sequence of the cytoplasmic domain of occludin (Furuse et al. 1994; Haskins et al. 1998; Itoh et al. 1999). Since occludin does not end in valine, the molecular basis for the occludin-MAGUKs interaction may be different from that of the claudin-MAGUKs interaction. In ZO-1, the GUK domain was reported to be responsible for occludin-ZO-1 binding (Fanning et al. 1998). If this is the case also for ZO-2 and ZO-3, each MAGUK molecule can bind to occludin and claudins simultaneously through GUK and PDZ1 domains, respectively. Furthermore, to complicate the molecular architecture model for the TJ plaque, ZO-1/ZO-2 and ZO-1/ZO-3 interactions were also reported, suggesting the existence of heterodimers of MAGUKs (Fanning et al. 1998; Haskins et al. 1998; Itoh et al. 1999). The results of this and previous studies revealed that these interactions were dependent on the PDZ2/PDZ2 interaction (Itoh et al. 1999). GFP-fusion proteins with PDZ2 domains of ZO-1/ZO-2/ZO-3 were recruited to TJs in MDCK cells (see Fig. 10), probably through this PDZ2/PDZ2 interaction. ZO-1 does not form homodimers reportedly (Fanning et al. 1998), but no information is available regarding the homodimers of ZO-2 and ZO-3. Furthermore, it remains unclear whether ZO-1, ZO-2, and ZO-3 exist in the TJ plaque as monomers. On the other hand, the COOH-terminal region of ZO-1 and ZO-2 directly binds to actin filaments (Itoh et al. 1997, Itoh et al. 1999; Fanning et al. 1998). These findings indicated that ZO-1, ZO-2 and ZO-3 function as scaffolds of the TJ plaque to cross-link TJ strands to the actin-based cytoskeleton.

Bottom Line: Claudin-1 and -2 were concentrated at cell-cell borders in an elaborate network pattern, to which endogenous ZO-1 was recruited.When ZO-2 or ZO-3 were further transfected, both were recruited to the claudin-based networks together with endogenous ZO-1.Detailed analyses showed that ZO-2 and ZO-3 are recruited to the claudin-based networks through PDZ2 (ZO-2 or ZO-3)/PDZ2 (endogenous ZO-1) and PDZ1 (ZO-2 or ZO-3)/COOH-terminal YV (claudins) interactions.

View Article: PubMed Central - PubMed

Affiliation: Department of Cell Biology, Faculty of Medicine, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.

ABSTRACT
ZO-1, ZO-2, and ZO-3, which contain three PDZ domains (PDZ1 to -3), are concentrated at tight junctions (TJs) in epithelial cells. TJ strands are mainly composed of two distinct types of four-transmembrane proteins, occludin, and claudins, between which occludin was reported to directly bind to ZO-1/ZO-2/ZO-3. However, in occludin-deficient intestinal epithelial cells, ZO-1/ZO-2/ZO-3 were still recruited to TJs. We then examined the possible interactions between ZO-1/ZO-2/ZO-3 and claudins. ZO-1, ZO-2, and ZO-3 bound to the COOH-terminal YV sequence of claudin-1 to -8 through their PDZ1 domains in vitro. Then, claudin-1 or -2 was transfected into L fibroblasts, which express ZO-1 but not ZO-2 or ZO-3. Claudin-1 and -2 were concentrated at cell-cell borders in an elaborate network pattern, to which endogenous ZO-1 was recruited. When ZO-2 or ZO-3 were further transfected, both were recruited to the claudin-based networks together with endogenous ZO-1. Detailed analyses showed that ZO-2 and ZO-3 are recruited to the claudin-based networks through PDZ2 (ZO-2 or ZO-3)/PDZ2 (endogenous ZO-1) and PDZ1 (ZO-2 or ZO-3)/COOH-terminal YV (claudins) interactions. In good agreement, PDZ1 and PDZ2 domains of ZO-1/ZO-2/ZO-3 were also recruited to claudin-based TJs, when introduced into cultured epithelial cells. The possible molecular architecture of TJ plaque structures is discussed.

Show MeSH
Related in: MedlinePlus