The distal carboxyl-terminal domains of ADAMTS13 are required for regulation of in vivo thrombus formation

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Abstract
ADAMTS13 is a multidomain protease that limits platelet thrombogenesis through the cleavage of von Willebrand factor (VWF). We previously identified 2 types of mouse Adamts13 gene: the 129/Sv-strain Adamts13 gene encodes the long-form ADAMTS13 having the same domains as human ADAMTS13, whereas the C57BL/6-strain Adamts13 gene encodes the short-form ADAMTS13 lacking the distal C-terminal domains. To assess the physiologic significance of the distal C-terminal domains of ADAMTS13, we generated and analyzed 129/Sv-genetic background congenic mice (Adamts13S/S) that carry the short-form ADAMTS13. Similar to wild-type 129/Sv mice (Adamts13L/L), Adamts13S/S did not have ultralarge VWF multimers in plasma, in contrast to 129/Sv-genetic background ADAMTS13-deficient mice (Adamts13−/−). However, in vitro thrombogenesis under flow at a shear rate of 5000 s−1 was accelerated in Adamts13S/S compared with Adamts13L/L. Both in vivo thrombus formation in ferric chloride–injured arterioles and thrombocytopenia induced by collagen plus epinephrine challenge were more dramatic in Adamts13S/S than in Adamts13L/L but less than in Adamts13−/−. These results suggested that the C-terminally truncated ADAMTS13 exhibited decreased activity in the cleavage of VWF under high shear rate. Role of the C-terminal domains may become increasingly important under prothrombotic conditions.