RESUMO
Wnt-11/planar cell polarity signaling polarizes mesodermal cells undergoing convergent extension during Xenopus laevis gastrulation. These shape changes associated with lateral intercalation behavior require a dynamic modulation of cell adhesion. In this paper, we report that Wnt-11/frizzled-7 (Fz7) controls cell adhesion by forming separate adhesion-modulating complexes (AMCs) with the paraxial protocadherin (PAPC; denoted as AMCP) and C-cadherin (denoted as AMCC) via distinct Fz7 interaction domains. When PAPC was part of a Wnt-11-Fz7 complex, its Dynamin1- and clathrin-dependent internalization was blocked. This membrane stabilization of AMCP (Fz7/PAPC) by Wnt-11 prevented C-cadherin clustering, resulting in reduced cell adhesion and modified cell sorting activity. Importantly, Wnt-11 did not influence C-cadherin internalization; instead, it promoted the formation of AMCC (Fz7/Cadherin), which competed with cis-dimerization of C-cadherin. Because PAPC and C-cadherin did not directly interact and did not form a joint complex with Fz7, we suggest that Wnt-11 triggers the formation of two distinct complexes, AMCC and AMCP, that act in parallel to reduce cell adhesion by hampering lateral clustering of C-cadherin.
Assuntos
Caderinas/metabolismo , Adesão Celular/fisiologia , Receptores Acoplados a Proteínas G/fisiologia , Proteínas Wnt/fisiologia , Proteínas de Xenopus/metabolismo , Proteínas de Xenopus/fisiologia , Animais , Caderinas/antagonistas & inibidores , Caderinas/genética , Regulação para Baixo/genética , Regulação para Baixo/fisiologia , Embrião não Mamífero/citologia , Embrião não Mamífero/fisiologia , Feminino , Gastrulação/fisiologia , Complexos Multiproteicos/metabolismo , Oócitos/citologia , Oócitos/fisiologia , Multimerização Proteica , Protocaderinas , Receptores Acoplados a Proteínas G/genética , Proteínas Wnt/genética , Proteínas de Xenopus/antagonistas & inibidores , Proteínas de Xenopus/genética , Xenopus laevisRESUMO
Small GTPases of the Rho family are important modulators of the cytoskeleton and regulate morphogenetic cell movements during embryonic development. In the Xenopus embryo, Rho signaling contributes to the regulation of convergent extension (CE) movements in gastrula and neurula stages as well as to tissue separation (TS). Here we describe a method that allows the detection of activated (GTP-bound) Rho in fixed Xenopus tissue. The assay makes use of a fusion protein of Rhotekin and Green-Fluorescent-Protein (RBD-GFP), which is produced in bacteria and can be purified biochemically. This technique allows a temporal and spatial analysis of Rho signaling in the developing embryo. Developmental Dynamics 238:1407-1411, 2009. (c) 2009 Wiley-Liss, Inc.
Assuntos
Imuno-Histoquímica/métodos , Proteínas de Xenopus/metabolismo , Xenopus laevis/embriologia , Xenopus laevis/metabolismo , Proteínas rho de Ligação ao GTP/metabolismo , Animais , Peptídeos e Proteínas de Sinalização Intracelular/genética , Peptídeos e Proteínas de Sinalização Intracelular/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/metabolismo , Transdução de Sinais/fisiologia , Proteínas de Xenopus/genética , Xenopus laevis/anatomia & histologia , Proteínas rho de Ligação ao GTP/genéticaRESUMO
Xenopus Paraxial Protocadherin (xPAPC) has signaling functions that are essential for convergent extension (CE) movements and tissue separation during gastrulation. PAPC modulates components of the planar cell polarity (PCP) pathway, but it is not clear how PAPC is connected to beta-catenin-independent Wnt-signaling. By yeast two-hybrid screen, we found that the intracellular domain of PAPC interacts with Sprouty (Spry), an inhibitor of CE movements. Upon binding to PAPC, Spry function is inhibited and PCP signaling is enhanced. Our data indicate that PAPC promotes gastrulation movements by sequestration of Spry and reveal a novel mechanism by which protocadherins modulate beta-catenin-independent Wnt-signaling.
