Development of alkyne-containing isoprenoid analogues to study protein prenylation in vivo and in vitro models of Alzheimer's disease and leukemia.

Abstract

Prenylation is a ubiquitous process in eukaryotes consisting of the post-translational modification of an array of proteins through the attachment of a lipophilic isoprenoid moiety. Prenyltransferase enzymes catalyze this process: farnesyltransferase appends the C15 isoprenoid from farnesyl diphosphate (FPP), and geranylgeranyltransferase type I, II and III append one or two C20 isoprenoids from geranylgeranyl diphosphate (GGPP). This modification allows proteins to fulfill their essential roles in cellular processes such as signal transduction or mediating protein-protein interactions. It has been reported that prenylation affects approximately 2% of the mammalian proteome. Due to the impact prenylation has on cellular biology, its presence and/or dysregulation has been linked to numerous diseases, including Alzheimer’s disease and multiple types of cancer. To study prenylated proteins as potential drug targets, several alkyne-modified chemical probes have been synthesized: a shorter C15AlkOPP designed to label both farnesylated and geranylgeranylated proteins, a longer C15PentOPP, designed to be specific for geranylgeranylated proteins, and a BisC15AlkOPP probe that uses a prodrug approach to increase the bioavailability of the C15AlkOPP probe when delivered in vivo. Proteomic experiments in different cell lines revealed the selectivity of C15PentOPP towards geranylgeranylated proteins (up to 93% of total prenylated proteins identified) and confirmed the C15AlkOPP and BisC15AlkOPP as probes for both farnesylation and geranylgeranylation. The latter 2 probes were used in in vivo and in vitro experiments using models for Alzheimer’s disease and leukemia to identify proteins whose extent of prenylation is altered, with the ultimate goal of discovering new potential drug targets.