The Magic of Proteases: From a Procoagulant and Anticoagulant Factor V to an Equitable Treatment of Its Inherited Deficiency

Abstract

Proteostasis, i.e., the homeostasis of proteins, responsible for ensuring protein turnover, is regulated by proteases, which also participate in the etiopathogenesis of multiple conditions. The magic of proteases is such that, in blood coagulation, one same molecule, such as coagulation factor V, for example, can perform both a procoagulant and an anticoagulant function as a result of the activity of proteases. However, this magic has an insidious side to it, as it may also prevent the completion of the clinical value chain of factor V deficiency. This value chain encompasses the discovery of knowledge, the transfer of this knowledge, and its translation to clinical practice. In the case of rare and ultra-rare diseases like factor V deficiency, this value chain has not been completed as the knowledge acquisition phase has dragged out over time, holding up the transfer of knowledge to clinical practice. The reason for this is related to the small number of patients afflicted with these conditions. As a result, new indications must be found to make the therapies cost-effective. In the case of factor V, significant research efforts have been directed at developing a recombinant factor V capable of resisting the action of the proteases capable of inactivating this factor. This is where bioethics and health equity considerations come into the equation.

Keywords: coagulation; coagulopathies; equity; factor V; homeostasis; proteases; rare diseases.

Figure 1

Activation and inactivation of coagulation factor V. The structure of the protein is made up of several domains: A1, A2, B, A3, C1, and C2. (A) Thrombin-mediated activation and deletion of the B domain. (B) Inactivation by APC and PS, assisted by vascular or platelet membrane phospholipids, and deletion of the A2 domain. FVa: activated factor V; APC, activated protein C; PS, protein S.

Figure 2

Factor V’s procoagulant and anticoagulant activity. (A) Prothrombinase complex-mediated procoagulant activity with thrombin generation. (B) Anticoagulant activity mediated by inactivation of the factor VIII component of the tenase complex and by the tissue factor pathway. F, factor; APC, activated protein C; PS, protein S; TFPI, tissue factor pathway inhibitor.

Figure 3

Evolution of the various strategies for the treatment of factor V deficiency and hemophilia A (Factor VIII deficiency).

Figure 4

Clinical value chain of factor V deficiency. APC, activated protein C.