Identification of a crucial tryptophan residue in ADAMTS13 required for its secretion and enzymatic activity

[Diagnosis of thrombotic thrombocytopenic purpura]

Thrombotic thrombocytopenic purpura (TTP) is a rare, life-threatening disease, disease, characterised by microangiopathic hemolytic anaemia, consumption thrombocytopenia, and organ dysfunction. The pathogenesis of TTP is attributed to the deficiency in the activity of the metalloproteinase ADAMTS13, specific von Willebrand factor cleaving protease. TTP is suspected when detecting microangiopathic hemolytic anemia, thrombocytopenia, damage to various organs. Diagnosis of TTP is confirmed by the detection of ADAMTS13 activity in plasma less than 10%. Plasma samples for the study of ADAMTS13 activity should be taken before the start of plasma transfusions or plasma exchange. In patients with severe ADAMTS-13 deficiency autoantibodies anti-ADAMTS13 and inhibitor ADAMTS13 should be investigated. Anti-ADAMTS13 antibodies belonging to IgG not always have inhibitory effects. The inhibitory effect of anti-ADAMTS13 antibodies is confirmed by mixing test. All patients with the first established diagnosis of TTP should be examined for mutations of the ADAMTS13 gene.

Tryptophan 387 and 390 residues in ADAMTS13 are crucial to the ability of vascular tube formation and cell migration of endothelial cells

A disintegrin and metalloproteinase with thrombospondin motifs 13 (ADAMTS13) was mainly generated and secreted from endothelial cells (ECs). Our previous study showed that tryptophan (Trp) residues at 387 and 390 in ADAMTS13 are required for its secretion and enzymatic activity. However, the effects on its host cell as well as the potential mechanism have not been clear. The aim of the study was to examine the effects of Trp residues 387 and 390 of ADAMTS13 on the biological processes of ECs. Herein, Trp was substituted with alanine in ADAMTS13 to generate ADAMTS13 mutants at 387 (W387A), 390 (W390A), and double mutants at 387 and 390 (2WA), respectively. We found that substitution mutation impaired vascular endothelial growth factor (VEGF) secretion and the downstream JAK1/STAT3 activation, the binding ability to Von Willebrand factor, cell proliferation, migration, and vascular tube formation. Overall, our study concluded that Trp387 and Trp390 of ADAMTS13 play vital roles in the biological function of ECs.