Association of SLP‐65 / BLNK with the B cell antigen receptor through a non‐ITAM tyrosine of Ig‐α

• Published in: European journal of immunology 2001-07, Vol.31 (7), p.2126-2134
• Main Authors: Engels, Niklas, Wollscheid, Bernd, Wienands, Jürgen
• Format: Article
• Language: English
• Subjects: Adaptor protein; Adaptor Proteins, Signal Transducing; Amino Acid Motifs; Amino Acid Sequence; Animals; Antigens, CD - chemistry; Antigens, CD - metabolism; B-Lymphocytes - immunology; BLNK; BLNK protein; Carrier Proteins - chemistry; Carrier Proteins - metabolism; CD79 Antigens; Cell Line; immunoreceptor tyrosine-based activation motif; Lymphocyte antigen receptor; Models, Immunological; Molecular Sequence Data; Phosphoproteins - chemistry; Phosphoproteins - metabolism; Phosphorylation; Phosphotyrosine - metabolism; Protein tyrosine phosphorylation; Receptors, Antigen, B-Cell - chemistry; Receptors, Antigen, B-Cell - metabolism; Sequence Alignment; SLP-65 protein; SLP‐65; Src homology 2 domain; src Homology Domains
• ISSN: 0014-2980; 1521-4141
• DOI: 10.1002/1521-4141(200107)31:7<2126::AID-IMMU2126>3.0.CO;2-O

The cytoplasmic adaptor protein SLP‐65 (BLNK or BASH) is a cricital downstream effector of the B cell antigen receptor (BCR). Tyrosine‐phosphorylated SLP‐65 assembles intracellular signaling complexes such as the Ca2 + initiation complex encompassing phospholipase C‐γ2 and Bruton′s tyrosine kinase. It is, however, unclear how the SLP‐65 signaling module can be recruited to the plasma membrane. Here we show that following B cell stimulation, SLP‐65 associates directly with the BCR signaling subunit, the Ig‐α / Ig‐β heterodimer. The interaction is mediated by theSrc homology 2 domain of SLP‐65 and the phosphorylated Ig‐α tyrosine 204, which is located outside of the immunoreceptor tyrosine‐based activation motif. Our data identify an unexpected BCR phosphorylation pattern and indicate that Ig‐α has the capability to serve as transmembrane adaptor in BCR signaling.