ADAMTS-13 is a plasma metalloprotease that cleaves von willebrand factor (vWF).At the present,it has been made great progresses on its structure, biological characteristics and function. ADAMTS-13 plays an important role in artery and venous thrombosis,besides controlling the cleaving of vWF, and the activity of the ADAMTS-13 can be effected by ion concentration and thrombin signal transduction pathway,but how the mechanism of ADAMTS-13 controlled is still not clear. This article reviews ADAMTS-13 changes,relevant mechanism and influencing factors of the enzyme regulation.
ADAM Proteins ; ADAMTS13 Protein ; Humans ; Thrombosis

OBJECTIVETo investigate the antigen levels and activity of von Willebrand factor cleaving protease ADAMTS13 in thrombotic thrombocytopenic purpura (TTP) patients and carriers.

METHODS28 samples from 13 TTP patients and 10 samples from the carriers were examined. The activity of ADAMTS13 was measured by residue collagen binding assay, and antigen by a newly developed sandwich ELISA.

RESULTSThe mean ADAMTS13 level in Chinese normal controls (CN) was (600.93 +/- 145.36) mU/ml (n = 26) comparable to the level (1000 mU/ml) in pooled normal Caucasian plasma, and the activity was (74.79 +/- 11.81)%. Both the antigen level and activity of ADAMTS13 in congenital TTP patients either before plasma exchange (pre-PE) or interval relapse were quite lower than those in normal control, but were increased after PE (post-PE). The antigen was (331.40 +/- 109.85) mU/ml (P < 0.01, n = 10), and activity was (66.79 +/- 12.82)% (P > 0.05). The ADAMTS13 levels pre-PE in idiopathic TTP was (98.7 +/- 82.08) mU/ml (n = 11, P < 0.01), and that post-PE was up to (449.4 +/- 232.33) mU/ml (P < 0.01, n = 10). The activity of ADAMTS13 in patients pre-PE and post-PE were (22.23 +/- 19.07)% (P < 0.01) and (60.92 +/- 22.33)% (P > 0.05) respectively. In a secondary TTP patient the ADAMTS13 antigen was much higher than that in CN, and the activity was 6.00%.

CONCLUSIONThe antigen and activity of ADAMTS13 in most TTP patients pre-PE are deficient, and these two indices in most TTP patients are paralleled. The reason for ADAMTS13 deficiency is congenital shortage or clearance by immune system, but it is unknown that why in some patients the ADAMTS13 antigen is extremely high but its activity is quite low.

ADAM Proteins ; blood ; immunology ; ADAMTS13 Protein ; Adult ; Female ; Humans ; Male ; Purpura, Thrombotic Thrombocytopenic ; blood ; immunology

ADAMTS13, a plasma metalloprotease, specifically cleaves von Willebrand factor (vWF). Severe deficiency of plasma ADAMTS13 activity results in thrombotic thrombocytopenic purpura (TTP). In this review, the structure and function of ADAMTS13 protease and its relationship with TTP are summarized.
ADAM Proteins ; metabolism ; ADAMTS13 Protein ; Humans ; Purpura, Thrombotic Thrombocytopenic ; diagnosis ; pathology ; therapy

ADAM Proteins ; genetics ; ADAM17 Protein ; Animals ; Gene Library ; Genetic Vectors ; Male ; Mice ; Two-Hybrid System Techniques

OBJECTIVETo investigate the gene mutations of ADAMTS13 in a highly suspected hereditary thrombocytopenic purpura (TTP) patient, and then make a progressive diagnosis and adjust the plan of therapy.

METHODSADAMTS13 activity and inhibitor were determined by residual-collagen binding assay during several episodes. Genomic DNA extracted from the proband's peripheral blood was used for amplification of 29 exons and exon/intron boundaries of ADAMTS13 by PCR. The PCR products were screened by direct sequencing and the gene alterations were further confirmed by direct sequencing in her family members.

RESULTThe activity of the proband's ADAMTS13 was significantly reduced while no inhibitor was found. Two novel missense mutations were found in the TSPI repeated motif domain of ADAMTS13. In both mutations, thymine substituted for cytidine, resulting in the substitution of leucine for serine in nt 2708, exon 21 (codon S903L), and tryptophan for arginine in nt 3283, exon 25(codon R1095W). These two mutations were revealed as each heterozygote in the proband's parents.

CONCLUSIONThe deficiency of ADAMTS13 caused by two homozygote missense mutations might be responsible for episode of this TTP patient.

ADAM Proteins ; genetics ; Adult ; Exons ; genetics ; Female ; Humans ; Mutation ; Purpura, Thrombotic Thrombocytopenic ; genetics

OBJECTIVETo study the efficacy and safety of rituximab (RTX) in the treatment of idiopathic thrombotic thrombocytopenic purpura (ITTP).

METHODSAmong 17 ITTP patients, nine cases of the RTX group were administrated with RTX plus plasma exchange (PEX) and steroids. Eight cases of the control group received PEX plus steroids±other immune inhibitors. Patients received RTX 375 mg/m², 1 per week for 4 weeks. The laboratory parameters, including hemogram, LDH, ADAMTS13 activities and its inhibitors, and the ratio of B lymphocytes in peripheral blood were monitored. The number of PEX, total plasma volumes, remission time, relapse ratio and adverse effects in both groups were compared.

RESULTSThe median number of PEX/median total plasma volumes in the RTX and control group were 5(2-8)/9.6(4.0-15.4) L and 6(4-9)/11.2(7.5-14.6) L, respectively. Patients in the RTX and control group achieved hematologic remission at the median time of 15(5-20) days and 22(7-36) days, respectively. And the median time of immunological remission in the two groups was 2(2-8) and 2(2-4) weeks, respectively. ADAMTS13 activities increased significantly after 2 weeks in both two groups. There was no relapse in the RTX group, while 4 patients relapsed in the control group. The percentage of B lymphocytes in peripheral blood obviously deduced one week after first dose of RTX infusion compared with the level before treatment [(2.19±5.11)% vs (18.39±7.15)%, P<0.001], and began to gradually increase 9 months later. Severe adverse events were not observed in RTX group during the therapeutic procedure and follow-up, but one patient, who had sustained immunologic remission, died of severe pneumonia 7 months later.

CONCLUSIONIn the treatment of ITTP, RTX in conjunction with PEX and steroids appeared to be a safe and effective therapy, with fast and sustained remission in hematology and even in immunology, with lower relapse rate and less adverse effects. But patients needed to be paid attention to prevent and treat infectious events in time.

ADAM Proteins ; ADAMTS13 Protein ; B-Lymphocytes ; Humans ; Plasma Exchange ; Purpura, Thrombotic Thrombocytopenic ; Recurrence ; Rituximab ; Steroids

Congenital thrombotic thrombocytopenic purpura, also known as Upshaw-Schulman syndrome, is a rare autosomal recessive genetic disorder. The main pathogenesis is homozygous or compound heterozygous variants of von Willebrand factor lyase (ADAMTS13) gene mapped to chromosome 9q34, which may result in severe lack of ADAMTS13 which cleaves von Willebrand factor (vWF) multimers in the plasma and increase the risk of microvascular thrombosis, leading to various complications. The advance of research on the pathogenesis of cTTP, recombinant human ADAMTS13 and gene therapy have made breakthroughs which may lead to cure of cTTP. This article has provided a review for the latest progress made in the diagnosis and treatment of cTTP.
ADAM Proteins/genetics* ; ADAMTS13 Protein/genetics* ; Homozygote ; Humans ; Purpura, Thrombotic Thrombocytopenic/therapy* ; von Willebrand Factor/genetics*

OBJECTIVE: To investigate the biological function of Cysteine rich (CysR) domain of a disintegrin and metalloprotease with thrombospondin type 1 repeats-13 (ADAMTS13) on cleavage of von Willebrand factor (vWF) and provide experimental evidence for exploring the pathogenesis of thrombotic thrombocytopenic purpura (TTP). METHODS: The six amino acids (EDGTLS) in ADAMTS13 CysR domain were point mutated one by one, and the mutant ADAMTS13 proteins were expressed and purified. The cleavage products of vWF polymer by wild-type or mutant ADAMTS13 under denaturing condition or shear stress were separated by 1% SeaKem HGT agarose gel and detected by Western blot. RESULTS: The mutant ADAMTS13 plasmids (M1: Glu515Ala; M2: Asp516Ala; M3: Gly517Ala; M4: Thr518Ala; M5: Leu519Ala; M6: Ser520Ala) were successfully constructed and the proteins of wild-type and mutant ADAMTS13 were purified. Wild-type ADAMTS13 almost completely cleaved the vWF polymer under denaturing condition, while the cleavage activity of M1 mutant was significantly reduced in the same condition (P<0.01). The cleavage activity of M1 mutant of ADAMTS13 was also significantly reduced compared with that of the wild-type under shear stress (P<0.01). The activity of M1 mutant to cleave the FRETS-vWF73 was dramatically reduced compared with that of wild-type ADAMTS13. However, the binding ability of M1 mutant to vWF was similar with that of wild-type ADAMTS13. CONCLUSION The CysR domain of ADAMTS13 plays an important role in the digestion of vWF under denaturing condition and shear stress. The Glu515 amino acid residue might be an important site for substrate recognition.
ADAM Proteins ; ADAMTS13 Protein/genetics* ; Humans ; Purpura, Thrombotic Thrombocytopenic/genetics* ; von Willebrand Factor/genetics*

This study was to acquire recombinant protein of von Willebrand factor cleaving protease (ADAMTS13, a disintegrin and metalloprotease with a thromboSpondin type 1 motifs 13), for further studies on its biological function in thrombosis and hemostasis. We transfected the Hela cells with the plasmid pSecTag-ADAMTS13 by lipofectamine. A positive cell cloning was selected by hygromycin-B. The recombinant protein was purified with Ni-NTA agarose column by gradient imidazole. The purity and immune activity of purified products were identified with SDS-PAGE and Western blotting respectively. We also measured the enzymatic activity of recombinant protein (rADAMTS13) by GST-His two-site ELISA assay. The results showed that we successfully constructed Hela cells ADAMTS2-4 which expressed high level of rADAMTS13. We received about 5.8 mg recombinant protein in culture supernantants per liter purified with Ni-NTA column. The protein formed a main lane at the position of 190 kDa with SDS-PAGE and reacted with polyclonal antibody against ADAMTS13 by Western blotting. The amount of rADAMTS13 activity was 6.4 U/mL, according to the normal plasma defined as 1 U/mL. In conclusion, rADAMTS13 protein had high purity, immune activity and good enzymatic activity, which could establish the experimental foundation for further research on biological function and mechanism of this unique metalloprotease.
ADAM Proteins ; biosynthesis ; genetics ; metabolism ; ADAMTS13 Protein ; HeLa Cells ; Humans ; Recombinant Proteins ; biosynthesis ; genetics ; metabolism ; Transfection ; von Willebrand Factor ; metabolism

This study was aimed to construct a pEGFP-N1 vector of von Willebrand factor cleaving protease (ADAMTS13, a disintegrin and metalloprotease with a thrombospondin type 1 motifs 13) so as to pave the way for further studying its synthesis and secretion. Human full-length cDNA sequence of ADAMTS13 was acquired by polymerase chain reaction (PCR) with Phusion(®) High-Fidelity (NEB), then the PCR product was double digested with EcoRI and XhoI. After digestion, the ADAMTS13 cDNA sequence was purified and recombined with the pEGFP-N1 vector. The DNA sequence analysis showed that ADAMTS13 was ligated to the pEGFP-N1 vector correctly. After transient expression in HeLa cells, the expression of EGFP could be detected by fluorescent microscopy, and the expression of ADAMTS13 protein could be detected by SDS-PAGE and Western blot. It is concluded that the ADAMTS13-pEGFP-N1 vector is successfully constructed, and it can be widely used in further research on the mechanism of the synthesis and secretion of ADAMTS13.
ADAM Proteins ; genetics ; ADAMTS13 Protein ; Gene Expression ; Genetic Vectors ; Green Fluorescent Proteins ; genetics ; HeLa Cells ; Humans ; Transfection