期刊
TOXICON
卷 77, 期 -, 页码 32-39出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.toxicon.2013.10.025
关键词
Serine protease; Saliva; Ixodes scapularis; Protease activated receptors (PAR); Activated protein C (APC)
资金
- National Institute of Health [AI 37230, 1U19 AI 082642, P20 RR16457]
- Intramural Research Program of the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health
- URI Proteomics Core facility
- [2006-34438-17306]
The saliva of ticks is critical to their survival as parasites and hematophagous animals. In this study, we have purified an enzyme with trypsin-like activity from the saliva of the tick vector of Lyme Disease, Ixodes scapularis. This enzyme, named as IXOSP (I. scapularis salivary serine protease), is a 29.9 kDa molecule with N-terminus FPxMVxLRIKxR. A BLAST search identified IXOSP as a secreted serine protease (AAY66740) with a conserved catalytic triad His, Asp, and Set. In vitro studies demonstrated that IXOSP cleaves chromogenic substrates with arginine in the P-1 position, by a mechanism inhibited by PMSF or aprotinin. Gene expression studies revealed that IXOSP is expressed at different tick developmental stages, including eggs, and unfed or fed adult tick salivary glands, but not in nymphs or in the midgut While the physiological substrate for IXOSP remains to be identified, we demonstrated that I. scapularis saliva activate protein C (PC) resulting in the production of activated PC, a potent anticoagulant that also regulates a myriad of inflammatory responses through protease activated receptors. In contrast, the salivary glands of Anopheles gambiae, Anopheles stephensi, Anopheles albimanus, Aedes aegypti, Lutzomyia longipalpis, and Phlebotomus ariasi did not activate protein C. These discoveries are discussed in the context of blood coagulation, inflammation and vector-host interactions. Published by Elsevier Ltd.
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