Longistatin is an unconventional serine protease and induces protective immunity against tick infestation.
Classical serine proteases use the conserved Ser/His/Asp catalytic triad to hydrolyze substrates. Here, we show that longistatin, a salivary gland protein with two EF-hand domains from the vector tick Haemaphysalis longicornis, does not have the conserved catalytic triad, but still functions as a serine protease. Longistatin was synthesized in and secreted from the salivary glands of ticks, and is injected into host tissues during the acquisition of blood-meals. Longistatin hydrolyzed fibrinogen, an essential plasma protein in the coagulation cascade, and activated plasminogen, into its active form plasmin, a serine protease that dissolves fibrin clots. Longistatin efficiently hydrolyzed several serine protease-specific substrates showing its specificity to the amide bond of Arg. Longistatin did not hydrolyze synthetic substrates specific for other groups of proteases. The enzyme was active at a wide range of temperatures and pHs, with the optimum at 37°C and pH 7. Its activity was efficiently inhibited by various serine protease inhibitors such as phenylmethanesulfonyl fluoride (PMSF), aprotinin, antipain, and leupeptin with the estimated IC(50) of 278.57 μM, 0.35 μM, 41.56 μM and 198.86 μM, respectively. In addition, longistatin was also potently inhibited by Zinc (Zn(2+)) in a concentration-dependent manner with an IC(50) value of 275 μM, and the inhibitory effect of Zn(2+) was revived by ethylenediaminetetra acetic acid (EDTA). Immunization studies revealed that longistatin sharply induced high levels of protective IgG antibodies against ticks. Immunization with longistatin reduced repletion of ticks by about 54%, post engorgement body weight by >11% and molting of nymphs by approximately 34%; thus, the vaccination trial was approximately 73% effective against tick infestation. Taken together, our results suggest that longistatin is a new potent atypical serine protease, and may be an interesting candidate for the development of anti-tick vaccines.
Department of Global Agricultural Sciences, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Japan.
Anisuzzaman
M Khyrul
MK
Islam
M Abdul
MA
Alim
Takeharu
T
Miyoshi
Takeshi
T
Hatta
Kayoko
K
Yamaji
Yasunobu
Y
Matsumoto
Kozo
K
Fujisaki
Naotoshi
N
Tsuji
D000818:Animals; D000906:Antibodies / Q000276:immunology; D000976:Antipain / Q000494:pharmacology; D007611:Aprotinin / Q000494:pharmacology; D001120:Arginine / Q000378:metabolism; D001835:Body Weight; D002135:Calcium-Binding Proteins / Q000037:antagonists & inhibitors / Q000276:immunology*; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation; D005340:Fibrinogen / Q000378:metabolism; D006868:Hydrolysis; D020128:Inhibitory Concentration 50; D026863:Ixodidae / Q000201:enzymology* / Q000276:immunology* / Q000472:pathogenicity; D007976:Leupeptins / Q000494:pharmacology; D051379:Mice; D008807:Mice, Inbred BALB C; D010960:Plasminogen Activators / Q000378:metabolism; D011817:Rabbits; D011994:Recombinant Proteins / Q000276:immunology / Q000302:isolation & purification / Q000378:metabolism; D012469:Salivary Glands / Q000201:enzymology / Q000276:immunology; D012471:Salivary Proteins and Peptides / Q000037:antagonists & inhibitors / Q000276:immunology*; D057057:Serine Proteases / Q000276:immunology; D015842:Serine Proteinase Inhibitors / Q000494:pharmacology; D013379:Substrate Specificity; D013696:Temperature; D013984:Tick Infestations / Q000276:immunology* / Q000469:parasitology / Q000628:therapy; D014105:Tosyl Compounds / Q000494:pharmacology; D014611:Vaccination; D015032:Zinc / Q000494:pharmacology
D000906:Antibodies; D002135:Calcium-Binding Proteins; D007976:Leupeptins; D011994:Recombinant Proteins; D012471:Salivary Proteins and Peptides; D015842:Serine Proteinase Inhibitors; D014105:Tosyl Compounds; C559189:longistatin protein, Haemaphysalis longicornis; D000976:Antipain; C003614:4-toluenesulfonyl fluoride; D005340:Fibrinogen; D007611:Aprotinin; D001120:Arginine; D004492:Edetic Acid; D057057:Serine Proteases; D010960:Plasminogen Activators; D015032:Zinc; C032854:leupeptin