Immunoreceptor tyrosine based

In B lymphocytes, coupling of the antigen receptors to Erk MAPkinase is protein tyrosine kinase (PTK)-dependent (Pao et al, 1997). Following ligation of the BCR (Fig. 19.2) the PTK, Lyn, tyrosine phosphorylates the immunoreceptor tyrosine-based activation motifs (ITAMs) on the accessory transducing molecules Ig-a and Ig-(3, leading to the recruitment... 

ITAM Immunoreceptor tyrosine-based activation motif E(M) 0(0) 0(0) ... 

Finally, platelets can be activated by immune complexes following binding of immunoglobulin G (IgG) Fc domains to platelet Fey RII. This process involves tyrosine phosphorylation of a motif designated as ITAM (immunoreceptor tyrosine-based motif) found on the cytoplasmic domain of platelet Fey RII receptors (73). This may play a role in immune complex diseases, particularly in heparin-induced thrombocytopenia. 

ITAM—immunoreceptor tyrosine-based activation motif... 

Chacko el al., 1996). Cell growth is arrested when the type II Fey receptor bl (FcyRIIbl) associates with the B cell receptor (BCR) by the interaction of their extracellular domains with immune complexes. Clustering FcyRIIbl with BCR induces the phosphorylation of the immunoreceptor tyrosine-based inhibitory motif (ITIM) within the FcyRIIb intracellular tail, which then allows SHIP to bind through its SH2 domain. Recruitment of SHIP to the cell membrane by FcyRIIb p-ITIM is believed to block extracellular Ca2+ uptake and cell growth via the inositol 5-phosphatase activity of SHIP. 

SHIP SH2 domain binds to the phosphorylated H IM (p-ITIM) of other inhibitory co-receptors (gp49Bl) (Kuroiwa etal., 1998) and to the p-ITIM-like motif of the adhesion receptor, PECAM-1 (Pumphrey et al., 1999), furthermore, in vitro it binds to the phosphorylated immunoreceptor tyrosine based activation motifs (p-ITAM) within the p and y subunits of the high affinity IgE receptor (Kimura et al. 1997)), and the zeta chain of T cell receptor (Osborne et al., 1996). However, in vivo coprecipitation of these molecules was not observed. 

Ig-a-Ig-P heterodimers. The intracellular domains of each of the Ig-a and Ig-[3 chains include an immunoreceptor tyrosine-based activation motif (ITAM). 

B. S. Gaul, M.L. Harrison, R.L. Geahlen, R.A. Burton, and C.B. Post. 2000. Substrate recognition by the Lyn protein-tyrosine kinase NMR structure of the immunoreceptor tyrosine-based activation motif signaling region of the B cell antigen receptor Biol. Chem. 275 16174-16182. (PubMed)... 

ITAM immunoreceptor tyrosine-based acdvadon modf... 

ITAM Immunoreceptor tyrosine-based activation motifs... 

Associated with each membrane-linked IgM molecule are two molecules of a heterodimeric membrane protein called Ig-a-Ig-p (see Figure 33.21). Examination of the amino acid sequences of Ig-a and Ig-P is highly instructive. The amino terminus of each protein lies outside the cell and corresponds to a single immunoglobulin, and the carboxyl terminus, which lies inside the cell, includes a sequence of 18 amino acids called an immunoreceptor tyrosine-based activation motif (ITAM see Figure 33.21). As its name suggests, each ITAM includes key tyrosine residues, which are subject to phosphorylation by particular protein kinases present in immune-system cells. 

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