Clinical expert round table discussion (session 3) at the Margaux Conference on Critical Illness: the role of activated protein C in severe sepsis.
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Blood Coagulation Disorders↗
Biomedical subjects
C Esmon
Publications and source records attributed to C Esmon.
The protein C pathway.
OBJECTIVE: To examine the role of the protein C anticoagulant pathway in the regulation of microvascular thrombosis. The mechanisms by which inflammation impairs the function of this pathway are also reviewed; conversely, we will survey emerging knowledge of the multiple mechanisms by which the protein C anticoagulant pathway can control the inflammatory response. DATA SOURCES: The information reviewed here was taken from the primary literature, including recent abstracts. STUDY SELECTION: All studies that bear directly on the interrelationship between the protein C anticoagulant pathway and inflammation were included, as was a summary of the initial clinical experience with protein C/activated protein C therapy in sepsis. DATA EXTRACTION AND SYNTHESIS: The results from each of the experimental approaches are summarized. Clinical experience with protein C supplementation in sepsis, although promising, is still in the early stages of study. CONCLUSIONS: The protein C anticoagulant pathway is a major mechanism in controlling microvascular thrombosis. Protein C deficiency that can occur in sepsis facilitates thrombin generation in the microvasculature, probably augmenting inflammatory responses and contributing to endothelial cell dysfunction. Animal studies and preliminary clinical results suggest that protein C/activated protein C supplementation may be useful in reversing microvascular dysfunction.
Animals↗
The 2.8 A crystal structure of Gla-domainless activated protein C.
The structure of the Gla-domainless form of the human anticoagulant enzyme activated protein C has been solved at 2.8 A resolution. The light chain is composed of two domains: an epidermal growth factor (EGF)-like domain modified by a large insert containing an additional disulfide, followed by a typical EGF-like domain. The arrangement of the long axis of these domains describes an angle of approximately 80 degrees. Disulfide linked to the light chain is the catalytic domain, which is generally trypsin-like but contains a large insertion loop at the edge of the active site, a third helical segment, a prominent cationic patch analogous to the anion binding exosite I of thrombin and a trypsin-like Ca[II] binding site. The arrangement of loops around the active site partially restricts access to the cleft. The S2 and S4 subsites are much more polar than in factor Xa and thrombin, and the S2 site is unrestricted. While quite open and exposed, the active site contains a prominent groove, the surface of which is very polar with evidence for binding sites on the primed side, in addition to those typical of the trypsin class found on the non-primed side.
Binding Sites↗