Disintegrins from Hematophagous Sources

Abstract

Bloodsucking arthropods are a rich source of salivary molecules (sialogenins) which inhibit platelet aggregation, neutrophil function and angiogenesis. Here we review the literature on salivary disintegrins and their targets. Disintegrins were first discovered in snake venoms, and were instrumental in our understanding of integrin function and also for the development of anti-thrombotic drugs. In hematophagous animals, most disintegrins described so far have been discovered in the salivary gland of ticks and leeches. A limited number have also been found in hookworms and horseflies, and none identified in mosquitoes or sand flies. The vast majority of salivary disintegrins reported display a RGD motif and were described as platelet aggregation inhibitors, and few others as negative modulator of neutrophil or endothelial cell functions. This notably low number of reported disintegrins is certainly an underestimation of the actual complexity of this family of proteins in hematophagous secretions. Therefore an algorithm was created in order to identify the tripeptide motifs RGD, KGD, VGD, MLD, KTS, RTS, WGD, or RED (flanked by cysteines) in sialogenins deposited in GenBank database. The search included sequences from various blood-sucking animals such as ticks (e.g., Ixodes sp., Argas sp., Rhipicephalus sp., Amblyommasp.), tabanids (e.g., Tabanus sp.), bugs (e.g., Triatoma sp., Rhodnius prolixus), mosquitoes (e.g., Anopheles sp., Aedes sp., Culex sp.), sand flies (e.g., Lutzomyia sp., Phlebotomus sp.), leeches (e.g., Macrobdella sp., Placobdella sp.) and worms (e.g., Ancylostoma sp.). This approach allowed the identification of a remarkably high number of novel putative sialogenins with tripeptide motifs typical of disintegrins (>450 sequences) whose biological activity remains to be verified. This database is accessible online as a hyperlinked worksheet and displays biochemical, taxonomic, and gene ontology aspects for each putative disintegrin. It is also freely available for download (right click with the mouse) at links (web version) and (stand alone version).

Ayadualin, a novel RGD peptide with dual antihemostatic activities from the sand fly Lutzomyia ayacuchensis, a vector of Andean-type cutaneous leishmaniasis

“…The relatively weaker inhibitory effect of ayadualin observed in the collagen-induced platelet aggregation suggested the involvement of several molecules, including integrin α IIb β 3 , in the primary platelet aggregation induced by collagen. Our result demonstrated that ayadualin required a higher concentration, at the micromolar level (IC 50 5.66 μM), for the inhibition of ADP-induced platelet aggregation than that reported in disintegrins (IC 50~1 50-300 nM) [28,29]. Similarly, the inhibitory activity of the binding between integrin α IIb β 3 and fibrinogen was lower in ayadualin (IC 50 0.15 μM) when compared to that of disintegrins (IC 50~1 .5-5 nM) [28,29].…”

“…Our result demonstrated that ayadualin required a higher concentration, at the micromolar level (IC 50 5.66 μM), for the inhibition of ADP-induced platelet aggregation than that reported in disintegrins (IC 50~1 50-300 nM) [28,29]. Similarly, the inhibitory activity of the binding between integrin α IIb β 3 and fibrinogen was lower in ayadualin (IC 50 0.15 μM) when compared to that of disintegrins (IC 50~1 .5-5 nM) [28,29]. The loop structure characterized in disintegrins may be required to express maximum binding affinity of the RGD sequence to integrins, although ayadualin is expected to form a disulfide bond structure to present the RGD sequence.…”

“…The natural RGD-containing peptides, disintegrins, identified in snake venoms, and the salivary glands of leeches, ticks, and horseflies, were shown to inhibit platelet aggregation by interfering with the binding of integrin α IIb β 3 on platelets to fibrinogen [27][28][29]. Functional analysis of ayadualin showed that the peptide inhibited both collagen and ADP-induced platelet aggregation, and the inhibition depended on the C-terminal RGD sequence and disulfide bond structure located on both sides of the RGD sequence.…”

“…Disintegrins present their RGD sequences to integrins by forming a characteristic disulfide bond-stabilized loop, the formation of which is essential for their activity, and competitively interfere with the binding between fibrinogen and integrins resulting in inhibition of platelet aggregation [27][28][29]. In insects, this family of proteins has been found solely in the salivary glands of the horsefly Tabanus yao [29,30].…”

“…The natural RGD-containing peptide, disintegrin, is a family of cysteine-rich peptides containing RGD motifs, discovered originally in snake venoms and later in saliva of hematophagous animals such as leeches and ticks [27][28][29]. Disintegrins present their RGD sequences to integrins by forming a characteristic disulfide bond-stabilized loop, the formation of which is essential for their activity, and competitively interfere with the binding between fibrinogen and integrins resulting in inhibition of platelet aggregation [27][28][29].…”