Synthesis and PKC binding of conformationally restricted indolactams by aza-Claisen rearrangement

点击翻译按钮获取中文摘要

Protein kinase C (PKC) is a key enzyme family involved in cellular signal transduction and tumor promotion. It consists of a catalytic domain for protein phosphorylation and a regulatory domain which binds tumor promoters like phorbol esters and teleocidins. The tumor promoter-binding site in PKC is a cysteine-rich domain (CRD) at the N-terminal regulatory region. With the discovery of eleven PKC isozymes, increasing importance is placed on isozyme specific analysis of function. Isozyme-selective activators or inhibitors represent powerful tools to analyze the role of PKC and become new medicinal leads for diseases related to PKC activation like the vascular complications by hyperglycemia.However, the development of such compounds has been hampered since pure PKC isozymes are not easily obtainable from natural sources. We have synthesized the CRD's of PKCgamma, delta, and eta consisting of ca.50 amino acids by solid phase strategy to establish the models of native PKCs. These peptides were efficiently folded upon zinc treatment to produce PKC regulatory domain surrogates that bind [^3H] phorbol 12,13-dibutyrate (PDBu) with high affinity comparable to native PKC itself, suggesting that these peptides serve as effective models for native PKCgamma, delta, and eta.Teleocidins and its core structure (-) -indolactam-V are most promising as lead compounds for isozyme selective activation or inhibition of PKC since they are chemically very stable and easily synthesized. Using the PKC surrogate peptides, we have identified two new indolactam derivatives with high PKCgamma CRD selectivity based on our strategy for the design of conformationally restricted indolactam derivatives by aza-Claisen rearrangement. Bridge formation between position 5 and 13 of (-) -indolactam-V was proved to be one of the most effective methods to fix the molecule to the active conformation and to develop new PKC activators with high isozyme selectivity.