The receptor tyrosine kinase Ror2 plays important roles in developmental morphogenesis. It has recently been shown that Ror2 mediates Wnt5a-induced noncanonical Wnt signaling by activating the Wnt–JNK pathway and inhibiting the β-catenin–TCF pathway. However, the function of Ror2 in noncanonical Wnt signaling leading to cell migration is largely unknown. We show, using genetically different or manipulated cultured cells, that Ror2 is critical for Wnt5a-induced, but not Wnt3a-induced, cell migration. Ror2-mediated cell migration requires the extracellular cysteine-rich domain (CRD), which is the binding site for Wnt5a, and the cytoplasmic proline-rich domain (PRD) of Ror2. Furthermore, Ror2 can mediate filopodia formation via actin reorganization, irrespective of Wnt5a, and this Ror2-mediated filopodia formation requires the actin-binding protein filamin A, which associates with the PRD of Ror2. Intriguingly, disruption of filopodia formation by suppressing the expression of either Ror2 or filamin A inhibits Wnt5a-induced cell migration, indicating that Ror2-mediated filopodia formation is essential for Wnt5a-induced cell migration.
The receptor tyrosine kinase Ror2 has recently been shown to act as an alternative receptor or coreceptor for Wnt5a and to mediate Wnt5a-induced migration of cultured cells. However, little is known about the molecular mechanism underlying this migratory process. Here we show by wound-healing assays that Ror2 plays critical roles in Wnt5a-induced cell migration by regulating formation of lamellipodia and reorientation of microtubule-organizing center (MTOC). Wnt5a stimulation induces activation of the c-Jun N-terminal kinase JNK at the wound edge in a Ror2-dependent manner, and inhibiting JNK activity abrogates Wnt5a-induced lamellipodia formation and MTOC reorientation. Additionally, the association of Ror2 with the actinbinding protein filamin A is required for Wnt5a-induced JNK activation and polarized cell migration. We further show that Wnt5a-induced JNK activation and MTOC reorientation can be suppressed by inhibiting PKC. Taken together, our findings indicate that Wnt5a/Ror2 activates JNK, through a process involving filamin A and PKC, to regulate polarized cell migration.Ror2 belongs to the Ror family of evolutionally conserved receptor tyrosine kinases (1) and acts as an alternative or coreceptor for Wnt5a, a representative noncanonical Wnt protein (2-4). During mouse development, Ror2 plays essential roles in developmental morphogenesis (5,6) and is expressed in various cell types that display extensive migratory activities, including neural crest-derived cells and mesenchymal cells (7). Loss-or gain-of-function analyses in mice, Xenopus laevis and Caenorhabditis elegans reveal that, like Wnt5a, Ror2 and/or Ror2 orthologs are required for convergent extension movements and for polarity and migration of several cell types during development (4 -6, 8, 9).It has been proposed that Ror2 mediates Wnt5a signaling by activating the Wnt-c-Jun N-terminal kinase (JNK) 4 pathway, which regulates convergent extension movements in Xenopus gastrulation, and/or inhibiting the -catenin-TCF pathway (2, 4, 10). Wnt5a stimulation is known to promote cell migration (11-13), which Ror2 seems to mediate through its association with filamin A (FLNa) (3). However, it remains largely unknown how Ror2 and FLNa function in Wnt5a-induced cell migration and whether JNK is involved in this process.Polarized cell migration is essential for development and wound-healing and requires rearrangements of microtubule (MT) and actin cytoskeletons (14,15). In directionally migrating cells in wounded monolayers of cultured cells (e.g. fibroblasts) following external stimuli (e.g. epidermal growth factor and lysophosphatidic acid), MT arrays and actin filaments become polarized facing to the wound edge. In such cells, selectively stabilized MTs (post-translationally detyrosinated tubulins or Glu tubulins) orient toward the leading edge and MT organizing center (MTOC) is reoriented to lie between the nucleus and the leading edge (16). At the leading edge, actin cytoskeletons are also reorganized to form lamellipodia, generating driving forc...
Ror2, a member of the mammalian Ror family of receptor tyrosine kinases, plays important roles in developmental morphogenesis, although the mechanism underlying activation of Ror2 remains largely elusive. We show that when expressed in mammalian cells, Ror2 associates with casein kinase I⑀ (CKI⑀), a crucial regulator of Wnt signaling. This association occurs primarily via the cytoplasmic C-terminal proline-rich domain of Ror2. We also show that Ror2 is phosphorylated by CKI⑀ on serine/threonine residues, in its C-terminal serine/ threonine-rich 2 domain, resulting in autophosphorylation of Ror2 on tyrosine residues. Furthermore, it was found that association of Ror2 with CKI⑀ is required for its serine/threonine phosphorylation by CKI⑀. Site-directed mutagenesis of tyrosine residues in Ror2 reveals that the sites of phosphorylation are contained among the five tyrosine residues in the proline-rich domain but not among the four tyrosine residues in the tyrosine kinase domain. Moreover, we show that in mammalian cells, CKI⑀-mediated phosphorylation of Ror2 on serine/ threonine and tyrosine residues is followed by the tyrosine phosphorylation of G protein-coupled receptor kinase 2, a kinase with a developmental expression pattern that is remarkably similar to that of Ror2. Intriguingly, a mutant of Ror2 lacking five tyrosine residues, including the autophosphorylation sites, fails to tyrosine phosphorylate G protein-coupled receptor kinase 2. This indicates that autophosphorylation of Ror2 is required for full activation of its tyrosine kinase activity. These findings demonstrate a novel role for CKI⑀ in the regulation of Ror2 tyrosine kinase.
Moesin is a member of the ezrin-radixin-moesin (ERM) family of cytoskeletal proteins. These proteins organize membrane domains by interacting with plasma membrane proteins and the actin cytoskeleton. Because of their high sequence similarity, ERM proteins are usually thought to be functionally redundant. Lymphocytes express two ERM proteins, ezrin and moesin. Whether each ERM plays a specialized role in lymphocytes, particularly in vivo, remains unknown. Here, we show that moesin has a crucial, non-redundant role in lymphocyte homeostasis. Moesin-deficient mice exhibited decreases in both T and B cells in the peripheral blood and lymph nodes, but not in the spleen. This phenotype was recapitulated in bone marrow (BM) chimeras with a hematopoietic moesin deficiency. Although the T and B cells apparently developed without major defects in the moesin-deficient mice, T cell egress from the thymus and immature B cell egress from the BM were impaired. In the periphery, both T and B cells showed delayed egress from lymphoid organs. We showed that moesin is the primary phosphorylated ERM subject to dynamic regulation during cell shape changes and migration. Our findings identify a previously unknown, non-redundant function of moesin in lymphocyte homeostasis in regulating lymphocyte egress from lymphoid organs.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.