B-cell linker

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B-cell linker
Symbols BLNK ; AGM4; BASH; BLNK-S; LY57; SLP-65; SLP65; bca
External IDs OMIM604515 MGI96878 HomoloGene32038 GeneCards: BLNK Gene
RNA expression pattern
PBB GE BLNK 207655 s at tn.png
More reference expression data
Species Human Mouse
Entrez 29760 17060
Ensembl ENSG00000095585 ENSMUSG00000061132
UniProt Q8WV28 Q9QUN3
RefSeq (mRNA) NM_001114094 NM_008528
RefSeq (protein) NP_001107566 NP_032554
Location (UCSC) Chr 10:
97.95 – 98.03 Mb
Chr 19:
40.93 – 40.99 Mb
PubMed search [1] [2]

The B-cell linker protein is encoded by the BLNK gene[1][2] and is an adaptor protein also known as SLP-65,[3] BASH,[4] and BCA.[5] BLNK is expressed in B cells and macrophages and plays a large role in B cell receptor signalling, in a fashion analogous to the role its paralogue SLP-76 plays in T cell receptor signalling.[6] As it has no known intrinsic enzymatic activity, the function of BLNK is to temporally and spatially coordinate and regulate signalling effectors downstream of the B cell receptor.


The function of BLNK was first illustrated in BLNK deficient DT40 cells, a chicken B-cell line, which exhibited an abrogated intracellular calcium mobilisation response and impaired activation of MAP kinases p38, JNK, and to a lesser degree ERK upon B-cell receptor (BCR) activation as compared to wild type DT40 cells.[7] In knockout mice, BLNK deficiency results in a partial block in B-cell development,[8][9] and in humans BLNK deficiency results in a much more profound block in B-cell development.[10]

Linker or adaptor proteins provide mechanisms by which receptors can amplify and regulate downstream effector proteins. The B-cell linker protein is essential for normal B-cell development.[supplied by OMIM][2]


BLNK consists of a N-terminal leucine zipper motif followed by an "acidic" region, a proline-rich region, and a C-terminal SH2 domain. The leucine zipper motif allows BLNK to localise to the plasma membrane, presumably by coiled-coil interactions with a membrane protein.[11] This leucine zipper motif distinguishes BLNK from its paralogue SLP-76 which, although having an N-terminal heptad-like organisation of leucine and isoleucine residues, has not been experimentally shown to have this motif. Recruitment of BLNK to the plasma membrane is also achieved by binding of the SH2 domain of BLNK to a non-ITAM phospho-tyrosine on Igα, a part of the B cell receptor complex.[12][13][14]

The acidic region of BLNK contains several inducibly phosphorylated tyrosine residues, at least five in humans, that mediate protein-protein interactions between BLNK and PLCγ2, Btk, Vav, and Nck.[15] A more recent mass spectrometry study of BLNK in DT40 cells found that at least 41 unique serine, threonine, and tyrosine residues are phosphorylated on BLNK.[16]


B-cell linker has been shown to interact with Grb2,[1][3][12][17] SH3KBP1,[18] CD79A,[12][13] MAP4K1[19] and Bruton's tyrosine kinase.[20][21]

Post-translational modification[edit]


  1. ^ a b Fu, C.; Turck, C. W.; Kurosaki, T.; Chan, A. C. (1998). "BLNK: A central linker protein in B cell activation". Immunity 9 (1): 93–103. doi:10.1016/S1074-7613(00)80591-9. PMID 9697839.  edit
  2. ^ a b "Entrez Gene: BLNK B-cell linker". 
  3. ^ a b Wienands, J.; Schweikert, J.; Wollscheid, B.; Jumaa, H.; Nielsen, P. J.; Reth, M. (1998). "SLP-65: A new signaling component in B lymphocytes which requires expression of the antigen receptor for phosphorylation". The Journal of experimental medicine 188 (4): 791–795. doi:10.1084/jem.188.4.791. PMC 2213353. PMID 9705962.  edit
  4. ^ Goitsuka, R.; Fujimura, Y.; Mamada, H.; Umeda, A.; Morimura, T.; Uetsuka, K.; Doi, K.; Tsuji, S.; Kitamura, D. (1998). "BASH, a novel signaling molecule preferentially expressed in B cells of the bursa of Fabricius". Journal of immunology (Baltimore, Md. : 1950) 161 (11): 5804–5808. PMID 9834055.  edit
  5. ^ Gangi-Peterson, L.; Peterson, S. N.; Shapiro, L. H.; Golding, A.; Caricchio, R.; Cohen, D. I.; Margulies, D. H.; Cohen, P. L. (1998). "Bca: An activation-related B-cell gene". Molecular immunology 35 (1): 55–63. PMID 9683264.  edit
  6. ^ Koretzky, G. A.; Abtahian, F.; Silverman, M. A. (2006). "SLP76 and SLP65: Complex regulation of signalling in lymphocytes and beyond". Nature Reviews Immunology 6 (1): 67–78. doi:10.1038/nri1750. PMID 16493428.  edit
  7. ^ Ishiai, M.; Kurosaki, M.; Pappu, R.; Okawa, K.; Ronko, I.; Fu, C.; Shibata, M.; Iwamatsu, A.; Chan, A. C.; Kurosaki, T. (1999). "BLNK required for coupling Syk to PLC gamma 2 and Rac1-JNK in B cells". Immunity 10 (1): 117–125. doi:10.1016/S1074-7613(00)80012-6. PMID 10023776.  edit
  8. ^ Jumaa, H.; Wollscheid, B.; Mitterer, M.; Wienands, J.; Reth, M.; Nielsen, P. J. (1999). "Abnormal development and function of B lymphocytes in mice deficient for the signaling adaptor protein SLP-65". Immunity 11 (5): 547–554. doi:10.1016/S1074-7613(00)80130-2. PMID 10591180.  edit
  9. ^ Pappu, R.; Cheng, A. M.; Li, B.; Gong, Q.; Chiu, C.; Griffin, N.; White, M.; Sleckman, B. P.; Chan, A. C. (1999). "Requirement for B cell linker protein (BLNK) in B cell development". Science 286 (5446): 1949–1954. doi:10.1126/science.286.5446.1949. PMID 10583957.  edit
  10. ^ Minegishi, Y.; Rohrer, J.; Coustan-Smith, E.; Lederman, H. M.; Pappu, R.; Campana, D.; Chan, A. C.; Conley, M. E. (1999). "An essential role for BLNK in human B cell development". Science 286 (5446): 1954–1957. doi:10.1126/science.286.5446.1954. PMID 10583958.  edit
  11. ^ Köhler, F.; Storch, B.; Kulathu, Y.; Herzog, S.; Kuppig, S.; Reth, M.; Jumaa, H. (2005). "A leucine zipper in the N terminus confers membrane association to SLP-65". Nature Immunology 6 (2): 204–210. doi:10.1038/ni1163. PMID 15654340.  edit
  12. ^ a b c Engels, N.; Wollscheid, B.; Wienands, J. R. (2001). "Association of SLP-65 / BLNK with the B cell antigen receptor through a non-ITAM tyrosine of Ig-α". European Journal of Immunology 31 (7): 2126–2134. doi:10.1002/1521-4141(200107)31:7<2126::AID-IMMU2126>3.0.CO;2-O. PMID 11449366.  edit
  13. ^ a b Kabak, S.; Skaggs, B. J.; Gold, M. R.; Affolter, M.; West, K. L.; Foster, M. S.; Siemasko, K.; Chan, A. C.; Aebersold, R.; Clark, M. R. (2002). "The Direct Recruitment of BLNK to Immunoglobulin α Couples the B-Cell Antigen Receptor to Distal Signaling Pathways". Molecular and Cellular Biology 22 (8): 2524–2535. doi:10.1128/MCB.22.8.2524-2535.2002. PMC 133735. PMID 11909947.  edit
  14. ^ Pike, K. A.; Ratcliffe, M. J. (2005). "Dual requirement for the Ig alpha immunoreceptor tyrosine-based activation motif (ITAM) and a conserved non-Ig alpha ITAM tyrosine in supporting Ig alpha beta-mediated B cell development". Journal of immunology (Baltimore, Md. : 1950) 174 (4): 2012–2020. doi:10.4049/jimmunol.174.4.2012. PMID 15699130.  edit
  15. ^ Chiu, C. W.; Dalton, M.; Ishiai, M.; Kurosaki, T.; Chan, A. C. (2002). "BLNK: Molecular scaffolding through 'cis'-mediated organization of signaling proteins". The EMBO Journal 21 (23): 6461–6472. doi:10.1093/emboj/cdf658. PMC 136961. PMID 12456653.  edit
  16. ^ Oellerich, T.; Gronborg, M.; Neumann, K.; Hsiao, H. -H.; Urlaub, H.; Wienands, J. (2009). "SLP-65 Phosphorylation Dynamics Reveals a Functional Basis for Signal Integration by Receptor-proximal Adaptor Proteins". Molecular & Cellular Proteomics 8 (7): 1738–1750. doi:10.1074/mcp.M800567-MCP200. PMC 2709198. PMID 19372136.  edit
  17. ^ Fusaki, N.; Tomita, S.; Wu, Y.; Okamoto, N.; Goitsuka, R.; Kitamura, D.; Hozumi, N. (2000). "BLNK is associated with the CD72 / SHP-1 / Grb2 complex in the WEHI231 cell line after membrane IgM cross-linking". European Journal of Immunology 30 (5): 1326–1330. doi:10.1002/(SICI)1521-4141(200005)30:5<1326::AID-IMMU1326>3.0.CO;2-Q. PMID 10820378.  edit
  18. ^ Watanabe, S.; Take, H.; Takeda, K.; Yu, Z. X.; Iwata, N.; Kajigaya, S. (2000). "Characterization of the CIN85 Adaptor Protein and Identification of Components Involved in CIN85 Complexes". Biochemical and Biophysical Research Communications 278 (1): 167–174. doi:10.1006/bbrc.2000.3760. PMID 11071869.  edit
  19. ^ Tsuji, S.; Okamoto, M.; Yamada, K.; Okamoto, N.; Goitsuka, R.; Arnold, R.; Kiefer, F.; Kitamura, D. (2001). "B Cell Adaptor Containing Src Homology 2 Domain (Bash) Links B Cell Receptor Signaling to the Activation of Hematopoietic Progenitor Kinase 1". The Journal of experimental medicine 194 (4): 529–539. doi:10.1084/jem.194.4.529. PMC 2193495. PMID 11514608.  edit
  20. ^ Yasuda, T.; Tezuka, T.; Maeda, A.; Inazu, T.; Yamanashi, Y.; Gu, H.; Kurosaki, T.; Yamamoto, T. (2002). "Cbl-b Positively Regulates Btk-mediated Activation of Phospholipase C-γ2 in B Cells". The Journal of experimental medicine 196 (1): 51–63. doi:10.1084/jem.20020068. PMC 2194016. PMID 12093870.  edit
  21. ^ Hashimoto, S.; Iwamatsu, A.; Ishiai, M.; Okawa, K.; Yamadori, T.; Matsushita, M.; Baba, Y.; Kishimoto, T.; Kurosaki, T.; Tsukada, S. (1999). "Identification of the SH2 domain binding protein of Bruton's tyrosine kinase as BLNK--functional significance of Btk-SH2 domain in B-cell antigen receptor-coupled calcium signaling". Blood 94 (7): 2357–2364. PMID 10498607.  edit

Further reading[edit]