Alpha-2 Macroglobulin: A Novel Putative Interacting Partner of FXIII/FXIIIB Subunit?

Introduction Coagulation factor XIII (FXIII) is plasma circulating heterotetrameric protransglutaminase complex composed of two catalytic FXIII-A and two protective/regulatory FXIII-B subunits that covalently cross-links preformed fibrin clots to prevent premature fibrinolysis. The FXIII-A subunit is known to have pleiotropic roles outside coagulation as well. The FXIII-B subunit on the other hand is a relatively unknown entity, with roles limited to that of carrier and regulatory protein within the coagulation system so far.

Aim In the present study, we attempted to find putative novel interacting partners for FXIII/FXIII-B subunit.

Methods We combined content characterization of a commercial plasma FXIII concentrate FibrogamminP with pull-down assays performed for resin-bound recombinant FXIII-B on a FXIII-deficient plasma background to identify the common denominator in both experiments. Content characterization was done using gel filtration chromatography-based separation of the FibrogamminP excipient peaks and subsequent identification by mass spectrometry. Pull-down assays involved exposing resin-bound recombinant FXIII-B (through monoclonal antibody) to FXIII-deficient plasma and then evaluating the bound eluate with mass spectrometry. We anticipated that the proteins occurring in both these experiments are likely to be interacting partners of FXIII/FXIII-B subunit.

Results and Discussion We could identify only alpha-2-macroglobulin, a coagulation and fibrinolysis inhibitor as the common denominator in both experiments. Some complement system proteins like complement C3 and complement C1q also turned up as putative interacting partners in the pull-down assays only, whereas complement factor H was found in content analysis of plasma FXIII concentrate FibrogamminP.

No conflict of interest has been declared by the author(s).

Publication History

Article published online:
13 November 2020