N-wasp is essential for the negative regulation of B cell receptor signaling.
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.
Department of Cell Biology & Molecular Genetics, University of Maryland, College Park, Maryland, United States of America.
Chaohong
C
Liu
Xiaoming
X
Bai
Junfeng
J
Wu
Shruti
S
Sharma
Arpita
A
Upadhyaya
Carin I M
CI
Dahlberg
Lisa S
LS
Westerberg
Scott B
SB
Snapper
Xiaodong
X
Zhao
Wenxia
W
Song
D000199:Actins / Q000378:metabolism; D000818:Animals; D000974:Antibodies, Antinuclear / Q000097:blood; D000941:Antigens / Q000276:immunology; D001323:Autoantibodies / Q000097:blood; D001402:B-Lymphocytes / Q000276:immunology / Q000378:metabolism*; D002478:Cells, Cultured; D006801:Humans; D007963:Leukocytes, Mononuclear / Q000276:immunology / Q000378:metabolism; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D018345:Mice, Knockout; D021381:Protein Transport; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism*; D015398:Signal Transduction; D014923:Wiskott-Aldrich Syndrome / Q000276:immunology / Q000378:metabolism; D051316:Wiskott-Aldrich Syndrome Protein / Q000378:metabolism; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal / Q000502:physiology*
D000199:Actins; D000974:Antibodies, Antinuclear; D000941:Antigens; D001323:Autoantibodies; D011947:Receptors, Antigen, B-Cell; C495768:Was protein, mouse; C495772:Wasl protein, mouse; D051316:Wiskott-Aldrich Syndrome Protein; D051317:Wiskott-Aldrich Syndrome Protein, Neuronal