title: Spatial coupling of JNK activation to the B cell antigen receptor by tyrosine-phosphorylated ezrin.
abstract: The ezrin-radixin-moesin proteins regulate B lymphocyte activation via their effect on BCR diffusion and microclustering. This relies on their ability to dynamically tether the plasma membrane with actin filaments that is in turn facilitated by phosphorylation of the conserved threonine residue in the actin-binding domain. In this study, we describe a novel function of ezrin in regulating JNK activation that is mediated by phosphorylation of a tyrosine (Y353) residue that is unconserved with moesin and radixin. BCR, but not CD40, TLR4, or CXCR5 stimulation, induced phosphorylation of ezrin at Y353 in mouse splenic B cells. Ezrin existed in a preformed complex with Syk in unstimulated B cells and underwent Syk-dependent phosphorylation upon anti-IgM stimulation. Y353-phosphorylated ezrin colocalized with the BCR within minutes of stimulation and cotrafficked with the endocytosed BCRs through the early and late endosomes. The T567 residue of ezrin was rephosphorylated in late endosomes and at the plasma membrane at later times of BCR stimulation. Expression of a nonphosphorylatable Y353F mutant of ezrin specifically impaired JNK activation. BCR crosslinking induced the association of Y353-phosphorylated ezrin with JNK and its kinase MAPKK7, as well as spatial colocalization with phosphorylated JNK in the endosomes. The yellow fluorescent protein-tagged Y353F mutant displayed reduced colocalization with the endocytosed BCR as compared with wild-type ezrin-yellow fluorescent protein. Taken together, our data identify a novel role for ezrin as a spatial adaptor that couples JNK signaling components to the BCR signalosome, thus facilitating JNK activation.
authors: Department of Immunology, Lerner Research Institute, Cleveland Clinic, Cleveland, OH 44195, USA.
authors: Neetha
authors: N
authors: Parameswaran
authors: Gospel
authors: G
authors: Enyindah-Asonye
authors: Nayer
authors: N
authors: Bagheri
authors: Neilay B
authors: NB
authors: Shah
authors: Neetu
authors: N
authors: Gupta
mesh_terms: D000199:Actins / Q000235:genetics / Q000378:metabolism; D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000494:pharmacology*; D001402:B-Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001426:Bacterial Proteins; D002118:Calcium / Q000378:metabolism; D002460:Cell Line; D003598:Cytoskeletal Proteins / Q000235:genetics* / Q000378:metabolism; D004705:Endocytosis; D011992:Endosomes / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D017930:Genes, Reporter; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism; D008164:Luminescent Proteins; D008213:Lymphocyte Activation; D048670:MAP Kinase Kinase 4 / Q000235:genetics* / Q000378:metabolism; D048688:MAP Kinase Kinase 7 / Q000235:genetics / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D010766:Phosphorylation / Q000187:drug effects; D021381:Protein Transport; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D000072377:Syk Kinase; D014443:Tyrosine / Q000378:metabolism; D000099149:Ezrin
chemical_list: D000199:Actins; D000888:Antibodies, Anti-Idiotypic; D001426:Bacterial Proteins; D002118:Calcium; D003598:Cytoskeletal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; D048670:MAP Kinase Kinase 4; D048688:MAP Kinase Kinase 7; D011505:Protein-Tyrosine Kinases; D011947:Receptors, Antigen, B-Cell; D000072377:Syk Kinase; D014443:Tyrosine; D000099149:Ezrin; C044203:anti-IgM; C054562:yellow fluorescent protein, Bacteria; C000606897:Syk protein, mouse