[Assembly and secretion of mutant fibrinogens with variant gamma-chain C terminal region (gamma313-gamma345)].

BACKGROUND

It has been reported that the structure of the fibrinogen gamma-chain C terminal (D) region (140-411 residues) has important functions in fibrinogen assembly and/or secretion. Variant fibrinogens, gamma313S>N, gamma336M>I, gamma341A>D, and gamma345N>D have been reported as hypofibrinogenemias or dysfibrinogenemias. To study the assembly and secretion of the variant fibrinogens containing aberrant D regions, we established CHO cells producing these four fibrinogens.

METHODS

A fibrinogen gamma-chain expression vector was altered and transfected into CHO cells that expressed normal human fibrinogen Aalpha and Bbeta-chains. Cell lysates and culture media of the selected cell lines were subjected to ELISA and immunoblot analysis.

RESULTS

The CHO cells synthesized mutant gamma-chains and assembled these into fibrinogen, although these variant fibrinogens were barely secreted into the culture media. In the cell lysates, however, concentrations of these variant fibrinogens were higher than the normal levels.

CONCLUSIONS

The present study indicated that the tertiary structure of the fibrinogen gamma-chain C terminal region between 313 and 345 is necessary for fibrinogen secretion. These findings suggest that reduced levels of fibrinogen secretion lead to the hypofibrinogen in the patients and secreted fibrinogens might show dysfibrinogenemia.