Pradhan M, Coggeshall K M
Department of Microbiology, Ohio State University, Columbus 43210, USA.
J Cell Biochem. 1997 Oct 1;67(1):32-42. doi: 10.1002/(sici)1097-4644(19971001)67:1<32::aid-jcb4>3.0.co;2-x.
SHIP is a SH2 domain-containing inositol polyphosphatase that is selectively tyrosine phosphorylated and associated with the adapter protein Shc in B lymphocytes upon co-crosslinking surface immunoglobulin and Fc gamma RIIB1. We previously observed that this stimulation condition is associated with a reduction in the interaction of Grb2 with phosphorylated Shc, an enhanced interaction of Shc with SHIP, and a block in the Ras signaling pathway. We proposed that the SH2 domain of SHIP competes with Grb2 in binding to phospho-Shc, resulting in a block in Ras signaling. To test this model, we examined the mode of SHIP-Shc interaction. Using recombinant Shc and SHIP interaction domains and purified Shc and SHIP phosphopeptides, we show that the interaction is bi-dentate such that the SH2 domain of SHIP recognizes phosphorylated Y317 and doubly-phosphorylated Y239/Y240 of Shc and the Shc PTB domain recognizes phosphorylated NPxpY motifs within SHIP. We observed no role for the Shc SH2 domain in the interaction. These findings are consistent with our earlier model that SHIP and Grb2 compete for binding to phospho-Shc and support the notion that, in addition to the hydrolysis of inositol phosphates and phospholipids, SHIP contributes to anti-proliferative biochemistry by blocking protein-protein interactions.
SHIP是一种含SH2结构域的肌醇多磷酸酶，在表面免疫球蛋白和FcγRIIB1共同交联时，B淋巴细胞中的SHIP会被选择性地酪氨酸磷酸化，并与衔接蛋白Shc结合。我们之前观察到，这种刺激条件与Grb2与磷酸化Shc的相互作用减少、Shc与SHIP的相互作用增强以及Ras信号通路受阻有关。我们提出，SHIP的SH2结构域在与磷酸化Shc的结合中与Grb2竞争，导致Ras信号通路受阻。为了验证该模型，我们研究了SHIP与Shc的相互作用模式。使用重组的Shc和SHIP相互作用结构域以及纯化的Shc和SHIP磷酸肽，我们发现这种相互作用是双齿的，即SHIP的SH2结构域识别Shc的磷酸化Y317和双磷酸化的Y239/Y240，而Shc的PTB结构域识别SHIP内的磷酸化NPxpY基序。我们观察到Shc的SH2结构域在这种相互作用中不起作用。这些发现与我们早期的模型一致，即SHIP和Grb2竞争与磷酸化Shc的结合，并支持这样一种观点，即除了肌醇磷酸和磷脂的水解外，SHIP还通过阻断蛋白质-蛋白质相互作用来促进抗增殖生物化学过程。
