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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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mAb AA5 activates cell-associated C-cadherin only.  The ability of mAb AA5 to activate C-cadherin adhesion was determined after its addition to different components of the cell attachment assay. It was added either to the complete attachment  assay (as in Fig. 2), to the CEC1-5–coated substrate alone  (rinsed), or to the blastomeres alone (rinsed).
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Figure 6: mAb AA5 activates cell-associated C-cadherin only. The ability of mAb AA5 to activate C-cadherin adhesion was determined after its addition to different components of the cell attachment assay. It was added either to the complete attachment assay (as in Fig. 2), to the CEC1-5–coated substrate alone (rinsed), or to the blastomeres alone (rinsed).

Mentions: These findings raise an important question about the observations in Fig. 4, B and C. The intrinsic homophilic binding properties of the cadherin ectodomain, CEC1-5, are enhanced by mAb AA5. To what extent can the effects of mAb AA5 on the homophilic binding activity of CEC1-5 account for the reversal of activin-induced regulation of C-cadherin on the blastomere surface? To try to address this question, we asked whether the activation of    blastomere adhesion by mAb AA5 occurs primarily through direct effects on the purified CEC1-5 ectodomain or through effects on the normal C-cadherin expressed on the cell surface (Fig. 6). Blastomere adhesion to CEC1-5 provides C-cadherin in both contexts, purified ectodomain on an inert surface and normal C-cadherin and its associated cytoplasmic proteins at the blastomere surface. mAb AA5 was added either to the surface-bound CEC1-5 or to the activin-treated blastomeres separately. mAb AA5 had little or no effect when added to the surface-bound CEC1-5, but exerted its full effect when added to the blastomeres. This finding suggests that the enhanced homophilic binding activity of the cadherin ectodomain does not account significantly for the activation of adhesion by mAb AA5. Activation by mAb AA5 probably occurs primarily by altering C-cadherin function in the context of the cell surface.


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

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

mAb AA5 activates cell-associated C-cadherin only.  The ability of mAb AA5 to activate C-cadherin adhesion was determined after its addition to different components of the cell attachment assay. It was added either to the complete attachment  assay (as in Fig. 2), to the CEC1-5–coated substrate alone  (rinsed), or to the blastomeres alone (rinsed).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2132887&req=5

Figure 6: mAb AA5 activates cell-associated C-cadherin only. The ability of mAb AA5 to activate C-cadherin adhesion was determined after its addition to different components of the cell attachment assay. It was added either to the complete attachment assay (as in Fig. 2), to the CEC1-5–coated substrate alone (rinsed), or to the blastomeres alone (rinsed).
Mentions: These findings raise an important question about the observations in Fig. 4, B and C. The intrinsic homophilic binding properties of the cadherin ectodomain, CEC1-5, are enhanced by mAb AA5. To what extent can the effects of mAb AA5 on the homophilic binding activity of CEC1-5 account for the reversal of activin-induced regulation of C-cadherin on the blastomere surface? To try to address this question, we asked whether the activation of    blastomere adhesion by mAb AA5 occurs primarily through direct effects on the purified CEC1-5 ectodomain or through effects on the normal C-cadherin expressed on the cell surface (Fig. 6). Blastomere adhesion to CEC1-5 provides C-cadherin in both contexts, purified ectodomain on an inert surface and normal C-cadherin and its associated cytoplasmic proteins at the blastomere surface. mAb AA5 was added either to the surface-bound CEC1-5 or to the activin-treated blastomeres separately. mAb AA5 had little or no effect when added to the surface-bound CEC1-5, but exerted its full effect when added to the blastomeres. This finding suggests that the enhanced homophilic binding activity of the cadherin ectodomain does not account significantly for the activation of adhesion by mAb AA5. Activation by mAb AA5 probably occurs primarily by altering C-cadherin function in the context of the cell surface.

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