1. Biochemical and functional characterization of Salp20, an Ixodes scapularis tick salivary protein that inhibits the complement pathway
K Tyson, C Elkins, H Patterson, E Fikrig, A de Silva Insect Mol Biol. 2007 Aug;16(4):469-79. doi: 10.1111/j.1365-2583.2007.00742.x.
Ixodes ticks are vectors of several pathogens including Borrelia burgdorferi. Tick saliva contains numerous molecules that facilitate blood feeding without host immune recognition and rejection. We have expressed, purified, and characterized Ixodes scapularis salivary protein 20 (Salp20), a potential inhibitor of the alternative complement pathway that shares homology with the Isac protein family. When analysed by SDS-PAGE and size exclusion chromatography, Salp20 was approximately 48 kDa, more than double its predicted mass, primarily due N- and O-linked glycosylations. Recombinant Salp20 inhibited the alternative complement pathway by dissociating the C3 convertase, and partially protected a serum sensitive species of Borrelia from lysis by normal human serum. We propose that Salp20 facilitates tick feeding and possibly protects tick-borne pathogens from complement components.
2. A novel antimicrobial peptide from salivary glands of the hard tick, Ixodes sinensis
Da Yu, Zonggen Sheng, Xueqing Xu, Jianxu Li, Hailong Yang, Zhigang Liu, Huw H Rees, Ren Lai Peptides. 2006 Jan;27(1):31-5. doi: 10.1016/j.peptides.2005.06.020. Epub 2005 Aug 8.
A novel antimicrobial peptide named as ixosin was isolated from the salivary glands of the hard tick, Ixodes sinensis, by gel filtration, ion exchange chromatography and reverse-phase high-performance liquid chromatography (RP-HPLC). Its amino acid sequence was determined as GLHKVMREVLGYERNSYKKFFLR by Edman degradation and its molecular weight was 2870.5 analyzed by fast atom bombardment (FAB) mass spectrometry. This is the first antimicrobial peptide from ticks that lacks cysteine in its primary structure. The cDNA encoding ixosin was cloned by cDNA library screening. The predicted protein from the cDNA sequence composed of 79 amino acids including mature ixosin. Purified ixosin exerted its antimicrobial activities against bacteria and fungi. No similarity was found by BLAST search to any database entries and, thus, our findings describe a novel antimicrobial peptide.
3. Penthalaris, a novel recombinant five-Kunitz tissue factor pathway inhibitor (TFPI) from the salivary gland of the tick vector of Lyme disease, Ixodes scapularis
Ivo M B Francischetti, Thomas N Mather, José M C Ribeiro Thromb Haemost. 2004 May;91(5):886-98. doi: 10.1160/TH03-11-0715.
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.
