Src-like adaptor protein (SLAP) regulates B cell receptor levels in a c-Cbl-dependent manner.
Src-like adaptor protein (SLAP) and c-Cbl recently have been shown to cooperate in regulating T cell receptor (TCR) levels in developing T cells. SLAP also is expressed in developing B cells, and its deficiency leads to alterations in B cell receptor (BCR) levels and B cell development. Hence, we hypothesized that SLAP and c-Cbl may cooperate during B cell development to regulate BCR levels. In mice deficient in both SLAP and c-Cbl, we found that B cell development is altered, suggesting that they function through intersecting pathways. To study the mechanism by which SLAP and c-Cbl alter BCR levels, we coexpressed them in a mature mouse B cell line (Bal-17). First we determined that SLAP associates with proximal components of the BCR complex after stimulation and internalization. Coexpression of SLAP and c-Cbl in Bal-17 led to decreased surface and total BCR levels. This decrease in BCR levels depended on intact Src homology 2 (SH2) and C-terminal domains of SLAP. In addition, a mutation in the SH2 domain of SLAP blocked its colocalization with c-Cbl and the BCR complex, whereas deletion of the C terminus did not affect its localization. Last, coexpression of SLAP and c-Cbl altered BCR complex recycling. This alteration in BCR complex recycling depended on enzymatically active c-Cbl and Src family kinases, as well as the intact SH2 and C-terminal domains of SLAP. These data suggest that SLAP has a conserved function in B and T cells by adapting c-Cbl to the antigen-receptor complex and targeting it for degradation.
Dragone
Leonard L
LL
Division of Pediatric Immunology/Rheumatology, Department of Pediatrics, University of California, San Francisco, CA 94143, USA.
Myers
Margaret D
MD
White
Carmen
C
Gadwal
Shyam
S
Sosinowski
Tomasz
T
Gu
Hua
H
Weiss
Arthur
A
D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology / Q000276:immunology / Q000378:metabolism; D002454:Cell Differentiation; D045744:Cell Line, Tumor; D015536:Down-Regulation; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D011485:Protein Binding; D050721:Proto-Oncogene Proteins c-cbl / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D016392:Proto-Oncogene Proteins pp60(c-src) / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D011947:Receptors, Antigen, B-Cell / Q000276:immunology / Q000378:metabolism*
D011947:Receptors, Antigen, B-Cell; C095148:Sla protein, mouse; D050721:Proto-Oncogene Proteins c-cbl; D016392:Proto-Oncogene Proteins pp60(c-src); C493849:Cbl protein, mouse