Spi-1 and Spi-B control the expression of the Grap2 gene in B cells.
The Ets family members Spi-1 and Spi-B have been implicated in the regulation of genes important for B cell antigen receptor (BCR) signaling. Mice deficient in Spi-B exhibit reduced B cell proliferation in response to BCR cross-linking and impaired T cell-dependent immune responses. This defect is exacerbated in the presence of Spi-1 haplo-insufficiency (Spi1+/- SpiB-/-). Tyrosine phosphorylation and calcium mobilization induced by BCR engagement is diminished in Spi1+/- SpiB-/- B lymphocytes, although many key BCR signaling proteins are expressed, suggesting that Spi-1 and Spi-B regulate expression of additional, unidentified signaling molecules. We now demonstrate that expression of the adaptor protein Grap2 is impaired in Spi1+/- SpiB+/- and Spi1+/- SpiB-/- B lymphocytes. Analysis of two alternate murine Grap2 promoters revealed a functionally important Spi-1 and Spi-B DNA binding element located in the downstream promoter. Ectopic expression of Grap2 in Grap2-deficient B cells reduced the recruitment of BLNK to Igalpha and the phosphorylation of specific substrates. Regulation of BLNK recruitment was dependent upon the Grap2 proline-rich domain, while modulation of phosphorylation was dependent upon both the proline-rich and SH2 domains. These data indicate that Spi-1 and Spi-B directly regulate the expression of Grap2 and that Grap2 functions to modulate BCR signaling, but that reduced Grap2 expression is unlikely to account for the BCR signaling defects observed in Spi1+/- SpiB-/- B cells.
Garrett-Sinha
Lee Ann
LA
Department of Biochemistry, State University of New York at Buffalo, 140 Farber Hall, 3435 Main Street, Buffalo, NY 14214, USA. leesinha@buffalo.edu
Hou
Ping
P
Wang
Duncheng
D
Grabiner
Brian
B
Araujo
Elizabeth
E
Rao
Sridhar
S
Yun
Theodore J
TJ
Clark
Edward A
EA
Simon
M Celeste
MC
Clark
Marcus R
MR
D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D001402:B-Lymphocytes / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D015152:Blotting, Northern; D015153:Blotting, Western; D045744:Cell Line, Tumor; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation / Q000235:genetics; D024202:Electrophoretic Mobility Shift Assay; D015870:Gene Expression / Q000235:genetics; D005838:Genotype; D006579:Heterozygote; D051379:Mice; D018345:Mice, Knockout; D008969:Molecular Sequence Data; D009154:Mutation; D009841:Oligonucleotides / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding; D011518:Proto-Oncogene Proteins / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D011947:Receptors, Antigen, B-Cell / Q000378:metabolism; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D015398:Signal Transduction; D013154:Spleen / Q000166:cytology / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D000099232:Proto-Oncogene Protein Spi-1
D048868:Adaptor Proteins, Signal Transducing; D004268:DNA-Binding Proteins; D009841:Oligonucleotides; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D011947:Receptors, Antigen, B-Cell; D015534:Trans-Activators; D014157:Transcription Factors; D000099232:Proto-Oncogene Protein Spi-1