# Mechanism underlying cofactor-dependent proteolysis of von Willebrand Factor

> **NIH NIH R01** · UNIVERSITY OF KANSAS MEDICAL CENTER · 2022 · $459,810

## Abstract

PROJECT SUMMARY
von Willebrand factor (VWF), a large multimeric plasma protein, plays a critical role in hemostasis. VWF
is synthesized and secreted as ultra-large (UL) multimers that contain 25-50 protomers. If not
processed by a plasma metalloprotease ADAMTS13, ULVWF can initiate the formation of life-
threatening thrombosis as in thrombotic thrombocytopenic purpura (TTP). How the proteolytic cleavage
of ULVWF by ADAMTS13 is regulated under physiological conditions is not fully understood. The
cleavage site is buried under the central β-sheet within the A2 domain of VWF, and tensile force is
required to expose the cleavage site for enzymatic cleavage to occur. Our preliminary studies have
demonstrated that coagulation factor VIII (FVIII) may function as a cofactor that facilitates the cleavage
of VWF by ADAMTS13 under mechanic shear. Taking advantage of our unique combination of
molecular, biochemical and single-molecule biophysical tools available in both laboratories, we will test
the hypothesis that the binding of FVIII to VWF-D’D3 and other adjacent domains such as the A2
domain may result in conformational changes in the central A2, thus exposing the cleavage site
(Y1605-M1606) more readily to ADAMTS13 under mechanical force. In Aim 1, we will determine
the mechanical unfolding profile of A2 with or without other adjacent domains in the absence and
presence of FVIII; in Aim 2, we will elucidate the molecular mechanism of A2 and FVIII interactions by
investigating their variants and mutants; and in Aim 3, we will determine the physiological relevance of
the FVIII-dependent proteolytic cleavage of VWF under force and in animal models and human with
heareditary TTP. The completion of the proposed project will help understand the molecular interactions
among substrate, enzyme, and protein cofactor under physiological conditions, which provides
rationales for the development of novel therapeutics for the prevention and treatment of TTP and other
thrombotic and inflammatory disorders.

## Key facts

- **NIH application ID:** 10376469
- **Project number:** 1R01HL157975-01A1
- **Recipient organization:** UNIVERSITY OF KANSAS MEDICAL CENTER
- **Principal Investigator:** Xiaohui Frank Zhang
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $459,810
- **Award type:** 1
- **Project period:** 2022-02-01 → 2026-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10376469

## Citation

> US National Institutes of Health, RePORTER application 10376469, Mechanism underlying cofactor-dependent proteolysis of von Willebrand Factor (1R01HL157975-01A1). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10376469. Licensed CC0.

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