Human neutrophil elastase activates human factor V but inactivates thrombin-activated human factor V

Area of Science:

• Biochemistry
• Hematology
• Protease research

Background:

• Human factor V (F.V) is a crucial cofactor in the prothrombinase complex.
• F.V activation by alpha-thrombin is essential for blood coagulation.
• Human neutrophil elastase (HNE) is a serine protease implicated in various physiological and pathological processes.

Purpose of the Study:

• To investigate the in vitro effects of human neutrophil elastase (HNE) on human factor V (F.V) and its activated form, F.Va.
• To compare HNE's proteolytic activity on F.V and F.Va with known physiological activators and inactivators.

Main Methods:

• Prothrombinase assays were used to measure cofactor activity.
• Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analyzed protein cleavage products.
• NH2-terminal sequence analysis identified specific cleavage sites.

Main Results:

• HNE treatment of F.V resulted in a time-dependent increase in cofactor activity, generating distinct cleavage products compared to alpha-thrombin.
• HNE treatment of F.Va led to a time-dependent decrease in cofactor activity, with cleavage of both heavy and light chains.
• Identified HNE cleavage sites on F.V and F.Va were near those targeted by alpha-thrombin and Activated Protein C (APC).

Conclusions:

• HNE can proteolytically activate F.V, yielding enhanced procoagulant cofactor activity similar to alpha-thrombin.
• HNE inactivates F.Va, with a mechanism comparable to APC-mediated inactivation.
• These findings suggest HNE plays a role in modulating coagulation factor V activity.