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Analysis of C-cadherin regulation during tissue morphogenesis with an activating antibody.

Zhong Y, Brieher WM, Gumbiner BM - J. Cell Biol. (1999)

Bottom Line: Thus, the activin-induced decrease in C-cadherin adhesive activity appears to be required for animal cap elongation.It does not work when added to CEC1-5 on the substrate.Together these findings suggest that the regulation of C-cadherin by activin and its activation by mAb AA5 involve changes in its cellular organization or interactions with other cell components that are not intrinsic to the isolated protein.

View Article: PubMed Central - PubMed

Affiliation: Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.

ABSTRACT
The regulation of cadherin-mediated adhesion at the cell surface underlies several morphogenetic processes. To investigate the role of cadherin regulation in morphogenesis and to begin to analyze the molecular mechanisms of cadherin regulation, we have screened for monoclonal antibodies (mAbs) that allow us to manipulate the adhesive state of the cadherin molecule. Xenopus C-cadherin is regulated during convergent extension movements of gastrulation. Treatment of animal pole tissue explants (animal caps) with the mesoderm-inducing factor activin induces tissue elongation and decreases the strength of C-cadherin-mediated adhesion between blastomeres (Brieher, W.M., and B.M. Gumbiner. 1994. J. Cell Biol. 126:519-527). We have generated a mAb to C-cadherin, AA5, that restores strong adhesion to activin-treated blastomeres. This C-cadherin activating antibody strongly inhibits the elongation of animal caps in response to activin without affecting mesodermal gene expression. Thus, the activin-induced decrease in C-cadherin adhesive activity appears to be required for animal cap elongation. Regulation of C-cadherin and its activation by mAb AA5 involve changes in the state of C-cadherin that encompass more than changes in its homophilic binding site. Although mAb AA5 elicited a small enhancement in the functional activity of the soluble C-cadherin ectodomain (CEC1-5), it was not able to restore cell adhesion activity to mutant C-cadherin lacking its cytoplasmic tail. Furthermore, activin treatment regulates the adhesion of Xenopus blastomeres to surfaces coated with two other anti-C-cadherin mAbs, even though these antibodies probably do not mediate adhesion through a normal homophilic binding mechanism. Moreover, mAb AA5 restores strong adhesion to these antibodies. mAb AA5 only activates adhesion of blastomeres to immobilized CEC1-5 when it binds to C-cadherin on the cell surface. It does not work when added to CEC1-5 on the substrate. Together these findings suggest that the regulation of C-cadherin by activin and its activation by mAb AA5 involve changes in its cellular organization or interactions with other cell components that are not intrinsic to the isolated protein.

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Activin regulation of blastomere attachment to anti– C-cadherin mAbs. (A) Attachment of uninduced, activin-induced, or activin-induced and mAb AA5-treated blastomeres  to substrates coated with CEC1-5, anti–C-cadherin mAb 6B6, or  anti–C-cadherin mAb 5G5. (B) Uninduced and activin-induced  blastomere attachment to fibronectin. (C) Attachment of uninduced and activin-induced blastomeres expressing an IL-2β receptor–C-cadherin cytoplasmic tail fusion protein to substrates  coated with anti–IL-2β receptor mAbs.
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Figure 5: Activin regulation of blastomere attachment to anti– C-cadherin mAbs. (A) Attachment of uninduced, activin-induced, or activin-induced and mAb AA5-treated blastomeres to substrates coated with CEC1-5, anti–C-cadherin mAb 6B6, or anti–C-cadherin mAb 5G5. (B) Uninduced and activin-induced blastomere attachment to fibronectin. (C) Attachment of uninduced and activin-induced blastomeres expressing an IL-2β receptor–C-cadherin cytoplasmic tail fusion protein to substrates coated with anti–IL-2β receptor mAbs.

Mentions: Regulation of cell adhesion may involve complex changes in the state of the adhesion molecule other than modulation of binding affinity. Therefore, we investigated whether activin and mAb AA5 could regulate C-cadherin–mediated adhesion independent of its homophilic binding site. To do so, we assayed blastomere attachment to two anti–C-cadherin mAbs raised against portions of C-cadherin expressed in bacteria, 6B6, and 5G5 (Brieher and Gumbiner, 1994), which are not expected to interact with C-cadherin via its homophilic binding site (Fig. 5). Xenopus blastomeres do attach to surfaces coated with these mAbs, and like attachment to CEC1-5, activin decreases the number of blastomeres that attach to the antibodies (Fig. 5 A). This effect is specific to C-cadherin, because activin did not decrease attachment to other substrates. Activin did not affect the attachment of blastomeres to mAbs raised against another cell surface protein, the IL-2β receptor ectodomain fused to the C-cadherin cytoplasmic tail (Fig. 5 C). Moreover, as reported previously (Smith et al., 1990), activin stimulates, instead of decreasing, attachment of blastomeres to fibronectin (Fig. 5 B). Therefore, activin specifically regulates the adhesion of blastomeres to two different anti–C-cadherin mAbs as well as adhesion by the normal C-cadherin homophilic interaction. Blastomere adhesion to mAbs 6B6 and 5G5 is also activated by mAb AA5 (Fig. 5 A). Addition of mAb AA5 stimulated the adhesion of activin-induced blastomeres to the mAbs to the same extent as it stimulated adhesion to CEC1-5, the homophilic binding substrate. Since mAbs 6B6 and 5G5 are highly unlikely to interact with C-cadherin through its homophilic binding site, these findings provide evidence that regulation of C-cadherin– mediated adhesion by activin and its activation by mAb AA5 occur by mechanisms other than modulation of homophilic binding affinity.


Analysis of C-cadherin regulation during tissue morphogenesis with an activating antibody.

Zhong Y, Brieher WM, Gumbiner BM - J. Cell Biol. (1999)

Activin regulation of blastomere attachment to anti– C-cadherin mAbs. (A) Attachment of uninduced, activin-induced, or activin-induced and mAb AA5-treated blastomeres  to substrates coated with CEC1-5, anti–C-cadherin mAb 6B6, or  anti–C-cadherin mAb 5G5. (B) Uninduced and activin-induced  blastomere attachment to fibronectin. (C) Attachment of uninduced and activin-induced blastomeres expressing an IL-2β receptor–C-cadherin cytoplasmic tail fusion protein to substrates  coated with anti–IL-2β receptor mAbs.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2132887&req=5

Figure 5: Activin regulation of blastomere attachment to anti– C-cadherin mAbs. (A) Attachment of uninduced, activin-induced, or activin-induced and mAb AA5-treated blastomeres to substrates coated with CEC1-5, anti–C-cadherin mAb 6B6, or anti–C-cadherin mAb 5G5. (B) Uninduced and activin-induced blastomere attachment to fibronectin. (C) Attachment of uninduced and activin-induced blastomeres expressing an IL-2β receptor–C-cadherin cytoplasmic tail fusion protein to substrates coated with anti–IL-2β receptor mAbs.
Mentions: Regulation of cell adhesion may involve complex changes in the state of the adhesion molecule other than modulation of binding affinity. Therefore, we investigated whether activin and mAb AA5 could regulate C-cadherin–mediated adhesion independent of its homophilic binding site. To do so, we assayed blastomere attachment to two anti–C-cadherin mAbs raised against portions of C-cadherin expressed in bacteria, 6B6, and 5G5 (Brieher and Gumbiner, 1994), which are not expected to interact with C-cadherin via its homophilic binding site (Fig. 5). Xenopus blastomeres do attach to surfaces coated with these mAbs, and like attachment to CEC1-5, activin decreases the number of blastomeres that attach to the antibodies (Fig. 5 A). This effect is specific to C-cadherin, because activin did not decrease attachment to other substrates. Activin did not affect the attachment of blastomeres to mAbs raised against another cell surface protein, the IL-2β receptor ectodomain fused to the C-cadherin cytoplasmic tail (Fig. 5 C). Moreover, as reported previously (Smith et al., 1990), activin stimulates, instead of decreasing, attachment of blastomeres to fibronectin (Fig. 5 B). Therefore, activin specifically regulates the adhesion of blastomeres to two different anti–C-cadherin mAbs as well as adhesion by the normal C-cadherin homophilic interaction. Blastomere adhesion to mAbs 6B6 and 5G5 is also activated by mAb AA5 (Fig. 5 A). Addition of mAb AA5 stimulated the adhesion of activin-induced blastomeres to the mAbs to the same extent as it stimulated adhesion to CEC1-5, the homophilic binding substrate. Since mAbs 6B6 and 5G5 are highly unlikely to interact with C-cadherin through its homophilic binding site, these findings provide evidence that regulation of C-cadherin– mediated adhesion by activin and its activation by mAb AA5 occur by mechanisms other than modulation of homophilic binding affinity.

Bottom Line: Thus, the activin-induced decrease in C-cadherin adhesive activity appears to be required for animal cap elongation.It does not work when added to CEC1-5 on the substrate.Together these findings suggest that the regulation of C-cadherin by activin and its activation by mAb AA5 involve changes in its cellular organization or interactions with other cell components that are not intrinsic to the isolated protein.

View Article: PubMed Central - PubMed

Affiliation: Cellular Biochemistry and Biophysics Program, Memorial Sloan-Kettering Cancer Center, New York 10021, USA.

ABSTRACT
The regulation of cadherin-mediated adhesion at the cell surface underlies several morphogenetic processes. To investigate the role of cadherin regulation in morphogenesis and to begin to analyze the molecular mechanisms of cadherin regulation, we have screened for monoclonal antibodies (mAbs) that allow us to manipulate the adhesive state of the cadherin molecule. Xenopus C-cadherin is regulated during convergent extension movements of gastrulation. Treatment of animal pole tissue explants (animal caps) with the mesoderm-inducing factor activin induces tissue elongation and decreases the strength of C-cadherin-mediated adhesion between blastomeres (Brieher, W.M., and B.M. Gumbiner. 1994. J. Cell Biol. 126:519-527). We have generated a mAb to C-cadherin, AA5, that restores strong adhesion to activin-treated blastomeres. This C-cadherin activating antibody strongly inhibits the elongation of animal caps in response to activin without affecting mesodermal gene expression. Thus, the activin-induced decrease in C-cadherin adhesive activity appears to be required for animal cap elongation. Regulation of C-cadherin and its activation by mAb AA5 involve changes in the state of C-cadherin that encompass more than changes in its homophilic binding site. Although mAb AA5 elicited a small enhancement in the functional activity of the soluble C-cadherin ectodomain (CEC1-5), it was not able to restore cell adhesion activity to mutant C-cadherin lacking its cytoplasmic tail. Furthermore, activin treatment regulates the adhesion of Xenopus blastomeres to surfaces coated with two other anti-C-cadherin mAbs, even though these antibodies probably do not mediate adhesion through a normal homophilic binding mechanism. Moreover, mAb AA5 restores strong adhesion to these antibodies. mAb AA5 only activates adhesion of blastomeres to immobilized CEC1-5 when it binds to C-cadherin on the cell surface. It does not work when added to CEC1-5 on the substrate. Together these findings suggest that the regulation of C-cadherin by activin and its activation by mAb AA5 involve changes in its cellular organization or interactions with other cell components that are not intrinsic to the isolated protein.

Show MeSH
Related in: MedlinePlus