Center for Hemostasis and Thrombosis Research, Molecular Oncology Research Institute; Tufts Medical Center; Boston, MA, USA
Cell-penetrating lipidated peptides, called pepducins, target specific intracellular loops of GPCRs and have recently emerged as effective allosteric modulators of GPCR activity that can turn receptors ‘On’ or ‘Off.' Pepducins translocate across the plasma membrane to activate or inhibit their cognate receptor at allosteric site(s) on the intracellular surface of the receptor-G protein interface. Membrane flipping is readily achieved through attachment of a hydrophobic lipid tether to the peptide which confers the ability to rapidly flip to the inner side where it remains tethered and efficiently targets specific receptor-G protein interactions encoded in the native receptor. For instance, we determined that the protease-activated receptor-1 (PAR1) i3-loop pepducin, P1pal-19, requires the PAR1 H8 helix and TM7 tyrosine propeller to stabilize the on-state and activate PAR1-G protein signaling. We also report the development of a first-in-class intracellular PAR1 inhibitor PZ-128 derived from the juxtamembrane region of the i3 loop/N-terminus of TM6 of PAR1. PZ-128 is an antiplatelet agent that provides rapid, specific, and reversible inhibition of platelet PAR1 in patients with coronary artery disease. The NMR structure of PZ-128 revealed a well-defined a-helix extending from the palmitate lipid, which is highly similar with the structure of the corresponding region of PAR1 in the off-state. Following a successful First-in-Human clinical trial in 31 subjects, we are currently evaluating PZ-128 for anti-thrombotic efficacy and safety in a multicenter Phase II clinical trial in patients undergoing PCI. Lastly, we are also developing a potent PAR2 pepducin antagonist to treat patients suffering from dysfunctional fibrotic, inflammatory and metabolic processes that contribute to severe NASH in the liver.
Keywords: Pepducins, peptide, liver, inflammatory, patients.