Longistatin,a plasminogen activator,is key to the availability of blood-meals for ixodid ticks

Ixodid ticks are notorious blood-sucking ectoparasites and are completely dependent on blood-meals from hosts. in addition to the direct severe effects on health and productivity,ixodid ticks transmit various deadly diseases to humans and animals. unlike rapidly feeding vessel-feeder hematophagous insects,the hard ticks feed on hosts for a long time (5-10 days or more),making a large blood pool beneath the skin. tick's salivary glands produce a vast array of bio-molecules that modulate their complex and persistent feeding processes. however,the specific molecule that functions in the development and maintenance of a blood pool is yet to be identified. recently,we have reported on longistatin,a 17.8-kda protein with two functional ef-hand ca++-binding domains,from the salivary glands of the disease vector,haemaphysalis longicornis,that has been shown to be linked to blood-feeding processes. here,we show that longistatin plays vital roles in the formation of a blood pool and in the acquisition of blood-meals. data clearly revealed that post-transcriptional silencing of the longistatin-specific gene disrupted ticks' unique ability to create a blood pool,and they consequently failed to feed and replete on blood-meals from hosts. longistatin completely hydrolyzed α%,β and γ chains of fibrinogen and delayed fibrin clot formation. longistatin was able to bind with fibrin meshwork,and activated fibrin clot-bound plasminogen into its active form plasmin,as comparable to that of tissue-type plasminogen activator (t-pa),and induced lysis of fibrin clot and platelet-rich thrombi. plasminogen activation potentiality of longistatin was increased up to 4 times by soluble fibrin. taken together,our results suggest that longistatin may exert potent functions both as a plasminogen activator and as an anticoagulant in the complex scenario of blood pool formation; the latter is critical to the feeding success and survival of ixodid ticks. © 2011 anisuzzaman et al.