Direct demonstration of involvement of the adaptor protein ShcA in the regulation of Ca2+-induced platelet aggregation

Phospho-Tyrosine(s) vs. Phosphatidylinositol Binding in Shc Mediated Integrin Signaling

The Shc adaptor protein, particularly its p52 isoform, has been identified as a primary signaling partner for the tyrosine(s)-phosphorylated cytoplasmic tails of activated β₃ integrins. Inspired by our recent structure of the Shc PTB domain in complex with a bi-phosphorylated peptide derived from β₃ cytoplasmic tail, we have initiated the investigation of Shc interaction with phospholipids of the membrane. We are particularly focused on PtdIns and their effects on Shc mediated integrin signaling in vitro. Here we present thermodynamic profiles and molecular details of the interactions between Shc, integrin, and PtdIns, all of which have been studied by ITC and solution NMR methods. A model of p52 Shc interaction with phosphorylated β₃ integrin cytoplasmic tail at the cytosolic face of the plasma membrane is proposed based on these data.

Integrin {beta}3 phosphorylation dictates its complex with the Shc phosphotyrosine-binding (PTB) domain

Adaptor protein Shc plays a key role in mitogen-activated protein kinase (MAPK) signaling pathway, which can be mediated through a number of different receptors including integrins. By specifically recognizing the tyrosine-phosphorylated integrin β(3), Shc has been shown to trigger integrin outside-in signaling, although the structural basis of this interaction remains nebulous. Here we present the detailed structural analysis of Shc phosphotyrosine-binding (PTB) domain in complex with the bi-phosphorylated β(3)integrin cytoplasmic tail (CT). We show that this complex is primarily defined by the phosphorylation state of the integrin C-terminal Tyr(759), which fits neatly into the classical PTB pocket of Shc. In addition, we have identified a novel binding interface which concurrently accommodates phosphorylated Tyr(747) of the highly conserved NPXY motif of β(3). The structure represents the first snapshot of an integrin cytoplasmic tail bound to a target for mediating the outside-in signaling. Detailed comparison with the known Shc PTB structure bound to a target TrkA peptide revealed some significant differences, which shed new light upon the PTB domain specificity.