Studies on the design and synthesis of modified tyrosine-containing peptide analogs as potential inhibitors in signal transduction pathways

Eung-Seok Lee, Purdue University

Abstract

Phosphorylation or dephosphorylation of proteins on tyrosine residues in signal transduction pathways plays an important role in the regulation of cell growth and transformation. The protein tyrosine kinases (PTK's) specifically catalyze tyrosine phosphorylations in substrate proteins or peptides. Tyrosine phosphorylation regulates the activities of the c-src family PTK's and the associations of PTK's with cytosolic proteins such as phosphatidylinositol 3-kinase or phospholipase C-$\gamma$, which meditate further signal transduction. Such regulations are thought to be performed by binding of phosphotyrosine residues to the src homology region 2 (SH-2) domain in proteins. The activities of the c-src family PTK's can also be regulated by the specific protein tyrosine phosphatases (PTPases) which catalyze the dephosphorylation of phosphotyrosine residues in the regulatory domains of the c-src family PTKs. Also, PTPase may be involved in cell cycle regulation. The design and synthesis of analogs of modified tyrosine-containing peptides as PTK inhibitors, as blocking agents of the association of PTK's with cytosolic proteins, or as PTPase inhibitors offers a strategy for the development of potential anticancer agents. Peptides containing modified tyrosine residues could act as product inhibitors or suicide substrate inhibitors of PTK's, as blocking agents, as well as substrate analog inhibitors of PTPases. Also the modified tyrosine-containing peptides are expected to be stable to the action of phosphatases. For the synthesis, the t-Boc protected modified tyrosine derivatives were prepared as key intermediates and then incorporated into the peptide sequence by standard solid phase peptide synthesis methodology using an automated peptide synthesizer. Phosphotyrosine-containing angiotensin I, phosphotyrosine-containing src peptide, p-phosphonomethyl-L-phenylalanine(Pmp)-containing angiotensin I, Pmp-containing lck peptide, and L-3-deoxymimosine-containing angiotensin I were synthesized and tested for their inhibition activities. The initial study of the synthesis of thiophosphotyrosine-containing peptides was performed. The t-Boc protected modified tyrosine derivatives should also be useful for additional synthetic strategies, as well. By arranging peptide sequences specific to each target molecule, modified tyrosine-containing peptides would be expected to serve as PTK inhibitors, blocking agents, or PTPase inhibitors, respectively. Also, the utilization of these modified tyrosine moieties in synthetic peptides will be helpful in the study of the mechanistic details of signal transductions.

Degree

Ph.D.

Advisors

Cushman, Purdue University.

Subject Area

Organic chemistry|Pharmacology

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