The receptor tyrosine kinase Ror2 associates with and is activated by casein kinase Iepsilon.
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 Iepsilon (CKIepsilon), 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 CKIepsilon 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 CKIepsilon is required for its serine/threonine phosphorylation by CKIepsilon. 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, CKIepsilon-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 CKIepsilon in the regulation of Ror2 tyrosine kinase.
Kani
Shuichi
S
Department of Genome Sciences, Faculty of Medical Sciences, Graduate School of Medicine, Kobe University, Kobe 650-0017, Japan. kani@med.kobe-u.ac.jp
Oishi
Isao
I
Yamamoto
Hiroyuki
H
Yoda
Akinori
A
Suzuki
Hiroaki
H
Nomachi
Akira
A
Iozumi
Kengo
K
Nishita
Michiru
M
Kikuchi
Akira
A
Takumi
Toru
T
Minami
Yasuhiro
Y
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D048149:Casein Kinase 1 epsilon / Q000378:metabolism*; D017868:Cyclic AMP-Dependent Protein Kinases / Q000378:metabolism; D054770:G-Protein-Coupled Receptor Kinase 3; D051379:Mice; D009154:Mutation; D010766:Phosphorylation; D017434:Protein Structure, Tertiary; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism*; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; D017384:Sequence Deletion; D020798:Two-Hybrid System Techniques; D051552:beta-Adrenergic Receptor Kinases
D020794:Receptor Protein-Tyrosine Kinases; D057050:Receptor Tyrosine Kinase-like Orphan Receptors; C477010:Ror2 protein, mouse; D048149:Casein Kinase 1 epsilon; D017868:Cyclic AMP-Dependent Protein Kinases; D054770:G-Protein-Coupled Receptor Kinase 3; C517850:GRK3 protein, mouse; D051552:beta-Adrenergic Receptor Kinases