Enantioselective synthesis of N-boc and N-fmoc protected diethyl 4-phosphono(difluoromethyl)-L-phenylalanine; agents suitable for the solid-phase synthesis of peptides containing nonhydrolyzable analogues of O-phosphotyrosine

SH2 domain protein interaction and possibilities for pharmacological intervention

SH2 domain containing proteins play a key role in the process of intracellular transmission of signalling events initiated at the cell surface. As a pre-requisite in the fulfillment of this function, these proteins bind to a variety of phospho-tyrosine (pY) containing target molecules. Delineation of these binding sites as essentially short linear peptides (both structurally and functionally) has led to the suggestion that the activity of these signalling complexes may be manipulated by the development of relatively simple peptide reagents. This review examines the range of possibilities open on this approach and the extent to which positive results have already been realised.

F2(Pmp)2-TAM zeta 3, a novel competitive inhibitor of the binding of ZAP-70 to the T cell antigen receptor, blocks early T cell signaling

Signaling by the T cell antigen receptor (TCR) is mediated by 17-residue tyrosine-based activation motifs (TAM) present in the cytoplasmic tails of the TCR zeta and CD3 chains. TAMs become tyrosine-phosphorylated upon TCR stimulation, creating a high affinity binding site for the tandem SH2 domains of ZAP-70. In permeabilized T cells, the association of TCR and ZAP-70 was inhibited by a protein tyrosine phosphatase (PTPase)-resistant TAM peptide analog, in which difluorophosphonomethyl phenylalanyl (F2Pmp) residues replaced phosphotyrosine. Inhibition of this association prevented TCR-stimulated tyrosine phosphorylation of ZAP-70 and reduced ZAP-70 kinase activity to basal levels. The reduction in ZAP-70 activity coincided with reduced tyrosine phosphorylation of a number of substrates. Such PTPase-resistant peptides, capable of disrupting SH2 domain-mediated protein-protein interactions, should prove useful in further dissection of multiple signaling pathways and may serve as models for rationally designed chemotherapeutic agents for the treatment of autoimmune and neoplastic disorders.