The distal carboxyterminal domains of murine ADAMTS13 influence proteolysis of platelet-decorated VWF strings in vivo.
BACKGROUND
The multidomain metalloprotease ADAMTS13 regulates the size of von Willebrand factor (VWF) multimers upon their release from endothelial cells. How the different domains in ADAMTS13 control VWF proteolysis in vivo remains largely unidentified.


METHODS
Seven C-terminally truncated murine ADAMTS13 (mADAMTS13) mutants were constructed and characterized in vitro. Their ability to cleave VWF strings in vivo was studied in the ADAMTS13(-/-) mouse.


RESULTS
Murine MDTCS (devoid of T2-8 and CUB domains) retained full enzyme activity in vitro towards FRETS-VWF73 and the C-terminal T6-8 (del(T6-CUB)) and CUB domains (delCUB) are dispensable under these assay conditions. In addition, mADAMTS13 fragments without the spacer domain (MDT and M) had reduced catalytic efficiencies. Our results hence indicate that similar domains in murine and human ADAMTS13 are required for activity in vitro, supporting the use of mouse models to study ADAMTS13 function in vivo. Interestingly, using intravital microscopy we show that removal of the CUB domains abolishes proteolysis of platelet-decorated VWF strings in vivo. In addition, whereas MDTCS is fully active in vivo, partial (del(T6-CUB)) or complete (delCUB) addition of the T2-8 domains gradually attenuates its activity.


CONCLUSIONS
Our data demonstrate that the ADAMTS13 CUB and T2-8 domains influence proteolysis of platelet-decorated VWF strings in vivo.
De Maeyer
B
B
Laboratory for Thrombosis Research, K.U. Leuven Campus Kortrijk, Kortrijk, Belgium.
De Meyer
S F
SF
Feys
H B
HB
Pareyn
I
I
Vandeputte
N
N
Deckmyn
H
H
Vanhoorelbeke
K
K
D000071120:ADAMTS13 Protein; D000818:Animals; D001665:Binding Sites; D001792:Blood Platelets / Q000166:cytology*; D015153:Blotting, Western; D002460:Cell Line; D006801:Humans; D008666:Metalloendopeptidases / Q000737:chemistry* / Q000502:physiology*; D051379:Mice; D008822:Mice, Transgenic; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D014841:von Willebrand Factor / Q000378:metabolism*
D014841:von Willebrand Factor; C502939:ADAMTS13 protein, mouse; D008666:Metalloendopeptidases; D000071120:ADAMTS13 Protein