title: Itchy, a Nedd4 ubiquitin ligase, downregulates latent membrane protein 2A activity in B-cell signaling.
abstract: Nedd4 family ubiquitin protein ligases (E3s) specifically associate with latent membrane protein 2A (LMP2A) of Epstein-Barr virus. Our previous studies analyzing LMP2A function in vitro have suggested that Nedd4 family E3s regulate LMP2A function. To determine the role of Nedd4 family E3s in LMP2A B-cell signaling, LMP2A transgenic (LMP2A(+)) mice were crossed with mice with the Itch-deficient (Itch(-/-)) background. Itchy, a mouse homologue of human AIP4, is a Nedd4 family E3 and is also the most abundant Nedd4 family E3 found in LMP2A affinity precipitates from B cells. There were significantly fewer B-cell receptor-positive B cells in spleen and bone marrow B cells in LMP2A(+) Itch(-/-) mice than in LMP2A(+) mice. In addition, LMP2A(+) Itch(-/-) bone marrow B cells formed larger colonies in cultures treated with interleukin-7 (IL-7) than control bone marrow B cells did. Finally, there was a dramatic increase in tyrosine phosphorylation of LMP2A and Syk in IL-7-cultured LMP2A(+) Itch(-/-) B cells. These results indicate that Nedd4 family E3s, in particular Itchy, downmodulate LMP2A activity in B-cell signaling.
authors.affiliation: Department of Microbiology-Immunology, Northwestern University Medical School, Chicago, Illinois 60611, USA.
authors.forename: Akiko
authors.initials: A
authors.lastname: Ikeda
authors.forename: Robert G
authors.initials: RG
authors.lastname: Caldwell
authors.forename: Richard
authors.initials: R
authors.lastname: Longnecker
authors.forename: Masato
authors.initials: M
authors.lastname: Ikeda
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000378:metabolism*; D002454:Cell Differentiation; D002472:Cell Transformation, Viral; D002478:Cells, Cultured; D015536:Down-Regulation; D056827:Endosomal Sorting Complexes Required for Transport; D008025:Ligases / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D000075702:Nedd4 Ubiquitin Protein Ligases; D015398:Signal Transduction; D044767:Ubiquitin-Protein Ligases; D014763:Viral Matrix Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D002135:Calcium-Binding Proteins; C037662:EBV-associated membrane antigen, Epstein-Barr virus; D056827:Endosomal Sorting Complexes Required for Transport; D014763:Viral Matrix Proteins; D000075702:Nedd4 Ubiquitin Protein Ligases; C000618483:Nedd4 protein, human; C000618461:Nedd4l protein, mouse; D044767:Ubiquitin-Protein Ligases; D008025:Ligases