Penthalaris, a novel recombinant five-Kunitz tissue factor pathway inhibitor (TFPI) from the salivary gland of the tick vector of Lyme disease, Ixodes scapularis.
Research article published in Thrombosis and haemostasis (2004)
Abstract
Tick saliva is a rich source of molecules with antiinflammatory, antihemostatic and immunosupressive properties. In this paper, a novel tick salivary gland cDNA with sequence homology to tissue factor pathway inhibitor (TFPI) and coding for a protein called Penthalaris has been characterized from the Lyme disease vector, Ixodes scapularis. Penthalaris is structurally unique and distinct from TFPI or TFPI-like molecules described so far, including Ixolaris, NAPc2, TFPI-1 and TFPI-2. Penthalaris is a 308-amino-acid protein (35 kDa, pI 8.58) with 12 cysteine bridges and 5 tandem Kunitz domains. Recombinant Penthalaris was expressed in insect cells and shown to inhibit factor VIIa (FVIIa)/tissue factor(TF)-induced factor X (FX) activation with an IC50 of approximately 100 pM. Penthalaris tightly binds both zymogen FX and enzyme FXa (exosite), but not FVIIa, as demonstrated by column gel-filtration chromatography. At high concentrations, Penthalaris attenuates FVIIa/TF-induced chromogenic substrate (S2288) hydrolysis and FIX activation. In the presence of DEGR-FX or DEGR-FXa, but not des-Gla-DEGR-FXa as scaf-folds, tight and stoichiometric inhibition of FVIIa/TF was achieved. In addition, Penthalaris blocks cell surface-mediated FXa generation by monomer (de-encrypted), but not dimer (encrypted) TF in HL-60 cells. Penthalaris may act in concert with Ixolaris and other salivary anti-hemostatics in order to help ticks to successfully feed on blood. Penthalaris is a novel anticoagulant and a tool to study FVIIa/TF-initiated biologic processes.
Abstract sourced from PubMed (NCBI) for the cited record. See the original publication for the authoritative version.
Summary
Tick saliva is a rich source of molecules with antiinflammatory, antihemostatic and immunosupressive properties.
Why This Matters for Hirudotherapy
This study characterized Penthalaris, a novel five-Kunitz-domain tissue factor pathway inhibitor cloned from the salivary gland of the tick Ixodes scapularis, and showed that the recombinant protein inhibits FVIIa/tissue-factor-induced factor X activation (IC50 ~100 pM) and binds factor X/Xa at an exosite. Note clearly that this is a tick salivary anticoagulant, not a medicinal-leech (Hirudo) molecule, so it is relevant to ASH only by analogy as part of the broader blood-feeding-organism secretome drug-discovery field that frames why leech saliva is studied, not as direct evidence for hirudotherapy. The work is preclinical molecular and cell-based pharmacology (recombinant expression in insect cells, in-vitro enzyme assays, HL-60 cell-surface studies) with no clinical testing, and despite its place in the same anticoagulant-discovery field it should not be presented as supporting leech therapy.
Citation
Penthalaris, a novel recombinant five-Kunitz tissue factor pathway inhibitor (TFPI) from the salivary gland of the tick vector of Lyme disease, Ixodes scapularis.
Francischetti IM et al. · Thrombosis and haemostasis, 2004
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