An IAP retrotransposon in the mouse ADAMTS13 gene creates ADAMTS13 variant proteins that are less effective in cleaving von Willebrand factor multimers

Abstract

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 (

Extensive contacts between ADAMTS13 exosites and von Willebrand factor domain A2 contribute to substrate specificity

“…Sites within VWF domain A2 interact with proximal MDTCS domains ( Table 1). 17 However, the cleavage of VWF multimers also requires interactions with distal TSP1 and CUB domains, [12][13][14] and these interactions may involve binding sites outside of VWF domain A2. Further mutagenesis of both ADAMTS13 and VWF should be able to identify and characterize these interactions, providing a framework for understanding how ADAMTS13 regulates VWF-dependent platelet adhesion to promote hemostasis and prevent thrombosis.…”

“…ADAMTS13 domains distal to the spacer are required to recognize and cleave VWF multimers under conditions of high fluid shear stress. [12][13][14] In addition, the proximal MDTCS domains ( Figure 1A) are necessary under all conditions, and they are sufficient for many substrates that do not depend on fluid shear stress to expose the scissile bond. 12,15,16 The ADAMTS13 metalloprotease domain recognizes the Tyr 1605 -Met 1606 bond of VWF, and an exosite in the spacer domain binds a C-terminal segment of the A2 domain that is approximately 60 residues distant.…”

“…In fact, C-terminal truncations of ADAMTS13 after the S, C, T, D, and M domains cause progressive decreases in protease activity. 12,13,17 Similarly, decreasing the length of peptides derived from the C-terminus of the VWF A2 domain causes a progressive decrease in their potency as ADAMTS13 inhibitors. 18 These data indicate that the MDTCS domains of ADAMTS13 interact with an extended segment of VWF domain A2.…”

A novel binding site for ADAMTS13 constitutively exposed on the surface of globular VWF

“…18,19,21 In contrast, ADAMTS13 murine strains, lacking the C-terminal TSPs and the CUB domains, showed appreciable reductions in VWF proteolysis in vitro. 22 Furthermore, a peptide from the first CUB domain has been found to inhibit VWF proteolysis under flow, but not under static, conditions. 23 The importance of ADAMTS13 C-terminal domains under flow has also been highlighted when the ADAMTS13 truncation mutant MDTCS was shown to have a reduced activity against VWF under the shear stress generated by a mini-vortex, 24 but the same activity as wild-type ADAMTS13 in a static assay.…”

A novel active endogenous retrovirus family contributes to genome variability in rat inbred strains

“…The orientation of inserting transposable elements might have an impact on its mutagenic potential: For the L1 retrotransposons, sense intronic insertions are usually more mutagenic, while antisense insertions frequently escape purifying selection (Chen et al 2006). Depending on the position of the insertion, it might be deleterious to protein function or can leave some function of the protein intact, potentially leading to dominant negative effects (Zhou et al 2007). The lack of any abnormalities in hd heterozygotes argues against an interference of the truncated centrobin product with normal protein function (Liška et al 2009).…”