An IAP retrotransposon in the mouse ADAMTS13 gene creates ADAMTS13 variant proteins that are less effective in cleaving von Willebrand factor multimers.
Severe deficiency of ADAMTS13, a von Willebrand factor (VWF)-cleaving metalloprotease, causes thrombotic thrombocytopenic purpura. When analyzed with VWF multimers, but not with an abbreviated VWF peptide (VWF73) as the substrate, the plasma ADAMTS13 activity levels of mouse strains segregated into a high and a low group that differed by approximately 10 fold. Low ADAMTS13 activity was detected in mice containing 2 alleles of intracisternal A-type particle (IAP) retrotransposon sequence in the ADAMTS13 gene. Molecular cloning of mouse ADAMTS13 identified 2 truncated variants (IAP-a and IAP-b) in the low-activity mice. Both of the IAP variants lacked the 2 carboxyl terminus thrombospondin type 1 repeat (TSR) and CUB domains of full-length ADAMTS13. The IAP-b variant also had splicing abnormalities affecting the spacer domain sequence and had miniscule enzymatic activity. Compared with full-length ADAMTS13, the IAP-a variant was approximately one ninth as active in cleaving VWF multimers but was only slightly less active in cleaving VWF73 peptide. Recombinant human ADAMTS13 was also less effective in cleaving VWF multimers than VWF73 when the C-terminal TSR sequence was deleted. In summary, the carboxyl terminus TSR sequence is important for cleaving VWF multimers. Assay results should be interpreted with caution when peptide substrates are used for analysis of variant ADAMTS13 proteins.
Zhou
Wenhua
W
Division of Hematology, Montefiore Medical Center, Albert Einstein College of Medicine, Bronx, NY 10467, USA.
Bouhassira
Eric E
EE
Tsai
Han-Mou
HM
D051722:ADAM Proteins / Q000235:genetics / Q000378:metabolism; D000071120:ADAMTS13 Protein; D000483:Alleles; D000818:Animals; D003001:Cloning, Molecular; D007426:Genes, Intracisternal A-Particle / Q000235:genetics; D006801:Humans; D008666:Metalloendopeptidases / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D046912:Multiprotein Complexes / Q000378:metabolism*; D016254:Mutagenesis, Insertional; D010455:Peptides / Q000378:metabolism; D017434:Protein Structure, Tertiary / Q000235:genetics; D011697:Purpura, Thrombotic Thrombocytopenic / Q000201:enzymology / Q000235:genetics; D012326:RNA Splicing; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D013379:Substrate Specificity / Q000235:genetics; D014841:von Willebrand Factor / Q000378:metabolism*
D046912:Multiprotein Complexes; D010455:Peptides; D011994:Recombinant Proteins; D014841:von Willebrand Factor; D051722:ADAM Proteins; C502939:ADAMTS13 protein, mouse; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human