Structural Basis for Platelet Antiaggregation by Angiotensin II Type 1 Receptor Antagonist Losartan (DuP-753) via Glycoprotein VI

Abstract

GPVI is a key receptor for collagen-induced platelet activation. Loss or inhibition of GPVI causes only mildly prolonged bleeding times but prevents arterial thrombus formation in animal models. Therefore, GPVI is considered to be a potent target molecule for therapy of thrombotic diseases. Recently, it was reported that the AT(1)-receptor antagonist losartan (DuP-753) and EXP3179 inhibit platelet adhesion and aggregation via GPVI. However, it is still not clear how losartan is associated with inhibition of binding between GPVI and collagen at the molecular level. Here, we show by NMR that losartan directly interacts with the hydrophobic region consisting of strands C' and E in the N-terminal Ig-like domain of GPVI. A reliable GPVI-losartan complex model is presented by using a combination of NMR data and in silico tools. These data indicated that the phenyl group with the tetrazole ring in losartan plays a crucial role in the interaction with GPVI.

Discovery of Novel GPVI Receptor Antagonists by Structure-Based Repurposing

“…The angiotensin II type I receptor antagonist losartan (Figure 1m) also ranked highly as a potential antagonist (#10). Retrospective literature searches revealed that this compound had previously been reported to interact with the collagen binding pocket of GPVI [28] and inhibit platelet aggregation both in vitro [29] and in vivo [30]. The fact that losartan has been shown to interact with GPVI at the collagen binding site in an independent study validates our methodology and provides confidence that our docking parameters are appropriate.…”

“…Neither of these compounds are associated with bleeding complications, but, retrospectively, both had been reported to have effects on platelet function. In addition, losartan had been shown to interact with GPVI at the collagen binding site at/around Lys41, by NMR [28]. Due to previous observations that losartan can affect TPR signaling [30], we looked for effects on TPR-mediated platelet activation by the agonist U46619.…”

“…Losartan is one of a class of angiotensin receptor blockers (ARBs) that also includes valsartan and olmesartan, amongst others. Valsartan does not have the protective effects on cardiovascular outcomes reported for losartan in vivo [36], suggesting that the inhibitory effects of losartan on GPVI may be unique amongst this drug class, and there is structural evidence to support this [28]. Three sartans were compared with losartan for effects on GPVI-mediated Ca 2+ release to determine whether GPVI antagonism is shared amongst this drug class.…”

Structure‐Based Approach To Improve a Small‐Molecule Inhibitor by the Use of a Competitive Peptide Ligand

“…[15] By using NMR spectroscopic methods in combination with in silico tools, we found that losartan specifically interacts with extracellular immunoglobulin (Ig)like domain 1 of GPVI with a K D value of 1.7 10 À4 m, and that the phenyltetrazole (PTZ) moiety in losartan is the key chemical structure for the interaction with GPVI (Figure 1 B). [15] By using NMR spectroscopic methods in combination with in silico tools, we found that losartan specifically interacts with extracellular immunoglobulin (Ig)like domain 1 of GPVI with a K D value of 1.7 10 À4 m, and that the phenyltetrazole (PTZ) moiety in losartan is the key chemical structure for the interaction with GPVI (Figure 1 B).…”

“…[13] Only residues 4-10, which represent the minimal binding sequence for binding to GPVI, are shown. [15] All carbon atoms in losartan are numbered. The residues important for GPVI binding are indicated by black boxes.…”