G-protein coupled receptor kinases and their inhibitors

Peptide inhibitors of G protein-coupled receptor kinases

G protein-coupled receptor kinases (GRKs) are regulatory enzymes involved in the modulation of seven-transmembrane-helix receptors. In order to develop specific inhibitors for these kinases, we synthesized and investigated peptide inhibitors derived from the sequence of the first intracellular loop of the beta2-adrenergic receptor. Introduction of changes in the sequence and truncation of N- and C-terminal amino acids increased the inhibitory potency by a factor of 40. These inhibitors not only inhibited the prototypical GRK2 but also GRK3 and GRK5. In contrast there was no inhibition of protein kinase C and protein kinase A even at the highest concentration tested. The peptide with the sequence AKFERLQTVTNYFITSE inhibited GRK2 with an IC50 of 0.6 microM, GRK3 with 2.6 microM and GRK5 with 1.6 microM. The peptide inhibitors were non-competitive for receptor and ATP. These findings demonstrate that specific peptides can inhibit GRKs in the submicromolar range and suggest that a further decrease in size is possible without losing the inhibitory potency.

Synthetic polymer systems in drug development

The use of synthetic polymers in drug discovery is reviewed, with particular reference to the increasing number of chemistries for therapeutic candidate preparation that employ linear polymers possessing differential solubilities in a variety of solvents. The uses of these polymers as primary components in liquid-phase organic synthesis, particularly applied to the generation of chemical compound libraries, are discussed, along with the challenges facing synthetic chemists and pharmaceutical scientists in preparing new and more efficient supports. The advantages inherent to the emerging field of liquid-phase combinatorial synthesis (LPCS) are considered and a number of key therapeutic targets prepared by newer polymer-supported routes are highlighted. Finally, the potential development issues for both liquid and solid-phase organic chemistries applied to parallel or combinatorial synthesis are discussed, taking into account future trends in the drug discovery and development process as a whole.