N-wasp is essential for the negative regulation of B cell receptor signaling

• Published in: PLoS biology 2013-11, Vol.11 (11), p.e1001704-e1001704
• Main Authors: Liu, Chaohong, Bai, Xiaoming, Wu, Junfeng, Sharma, Shruti, Upadhyaya, Arpita, Dahlberg, Carin I M, Westerberg, Lisa S, Snapper, Scott B, Zhao, Xiaodong, Song, Wenxia
• Format: Article
• Language: English
• Subjects: Actins - metabolism; Animals; Antibodies, Antinuclear - blood; Antigens - immunology; Autoantibodies - blood; Autoimmune diseases; B cells; B-Lymphocytes - immunology; B-Lymphocytes - metabolism; Cells, Cultured; Cellular signal transduction; Experiments; Flow cytometry; Humans; Immune system; Immunology; Kinases; Leukocytes, Mononuclear - immunology; Leukocytes, Mononuclear - metabolism; Lipids; Medicin och hälsovetenskap; Mice; Mice, 129 Strain; Mice, Inbred C57BL; Mice, Inbred CBA; Mice, Knockout; Physiological aspects; Protein Transport; Proteins; Receptors, Antigen, B-Cell - metabolism; Rodents; Signal Transduction; T cell receptors; Wiskott-Aldrich Syndrome - immunology; Wiskott-Aldrich Syndrome - metabolism; Wiskott-Aldrich Syndrome Protein - metabolism; Wiskott-Aldrich Syndrome Protein, Neuronal - physiology
• ISSN: 1545-7885; 1544-9173; 1545-7885
• DOI: 10.1371/journal.pbio.1001704

Negative regulation of receptor signaling is essential for controlling cell activation and differentiation. In B-lymphocytes, the down-regulation of B-cell antigen receptor (BCR) signaling is critical for suppressing the activation of self-reactive B cells; however, the mechanism underlying the negative regulation of signaling remains elusive. Using genetically manipulated mouse models and total internal reflection fluorescence microscopy, we demonstrate that neuronal Wiskott-Aldrich syndrome protein (N-WASP), which is coexpressed with WASP in all immune cells, is a critical negative regulator of B-cell signaling. B-cell-specific N-WASP gene deletion causes enhanced and prolonged BCR signaling and elevated levels of autoantibodies in the mouse serum. The increased signaling in N-WASP knockout B cells is concurrent with increased accumulation of F-actin at the B-cell surface, enhanced B-cell spreading on the antigen-presenting membrane, delayed B-cell contraction, inhibition in the merger of signaling active BCR microclusters into signaling inactive central clusters, and a blockage of BCR internalization. Upon BCR activation, WASP is activated first, followed by N-WASP in mouse and human primary B cells. The activation of N-WASP is suppressed by Bruton's tyrosine kinase-induced WASP activation, and is restored by the activation of SH2 domain-containing inositol 5-phosphatase that inhibits WASP activation. Our results reveal a new mechanism for the negative regulation of BCR signaling and broadly suggest an actin-mediated mechanism for signaling down-regulation.