Peptide Regulators of Protein-Protein Interactions with Selectivity for Specific Sub-Cellular Compartments

摘要

Protein kinase C (PKC) is a large family of 11 serine/threonine homologous isozyme kinases that are key enzymes in many signaling events as well as in disease states such as cancer [1], heart failure [2] and regulation of the immune response [3]. There are two major domains in PKC: (a) a conserved C-terminal catalytic domain, and (b) a N-terminal regulatory domain. Although the catalytic region in different PKC isozymes is highly conserved, each isozyme mediates unique cellular functions. There are no commercial isozyme-specific activators of PKC and the commercial inhibitors target the conserved catalytic domain of the enzyme and thus fail to be PKC isozymes-specific. The regulatory domain contains a C1 and C2 domains that play a critical role in PKC activation and translocation through interactions with second messengers, phospholipids, and inter- and intra-molecular protein-protein interactions [4], Relevant to this study, we showed that peptides derived from the C2 domain regulate the activity of single PKC isozyme by regulating isozyme-specific protein-protein interactions [4]. PKC delta (SPKC) isozyme participates in a variety of signal transduction pathways such as apoptosis [5], cell proliferation [6] and tumor suppression [7], and plays a significant role in many diseases such as cancer [8], stroke [9] and cardiac ischemia [10]. We previously described the use of 8V1-1 and δψRACK, 8PKC-selective antagonist and agonist, respectively. They were rationally designed [4] and are referred to here as: "First generation peptide regulators". δψRACK induces translocation of 8PKC to several sub-cellular sites where the enzyme phosphorylates select substrates. δψ1-1 blocks 8PKC translocation to all these sites and inhibits the interaction of PKC to its downstream signaling pathway [11] whereas δψRACK induces translocation to these sites. Focusing on 8PKC, we sought to identify new regulators that are selective in regulating the biological activity of SPKC related to a particular disease without affecting other housekeeping functions.