Cloning and Tissue expression of the Tissue Prothrombinase Fgl-2 in the Sprague-Dawley Rat

Abstract

Objective: To sequence and characterize the expression of the prothrombinase Fgl-2 in the Sprague-Dawley rat.

Methods: Reverse-transcriptase polymerase chain reaction was performed on RNA from spontaneoulsy cycling adult pregnant Sprague-Dawley rats by using specific Fgl-w primers. The resulting amplicon was also used to screen a rat spleen bacteriophage library and to probe a Northern blot of various tissues. The rat Fgl-2 amino acid sequence was compared with the known sequences in mouse and human.

Results: Fgl-w specific amplicon bands were observed in the rat brain, kidney, liver, ovary, spleen, and gestational day 22 and postpartum uterus. The rat Fgl-2 cDNA and amino acid sequence were found to be homologous with those of human (86% and 74%, respectively) and mouse (91% and 87%, respectively). Northern blotting demonstrated two different-sized transcripts (1.3 and 3.4 kb), and expression was observed in the cevix, heart, liver, ovary, and nongestational and gestational day 22 myometrium.

Conclusion: Thrombin is classically generated from the clevage of the proenzyme prothrombin by activated factors V and X. In tissues thrombin appears to be generated by a novel prothrombinase Fgl-2 (fibrinogen-like protein) whose activity is stimulated by proinflammatory mediators. Fgl-2 provides the mechanistic coupling between proinflammatory cytokines and generation of active thrombin independent of the coagulation cascade. Our studies confirmed the expression of Fgl-2 mRNA in several rat tissues, including the pregnant uterus, where it could play a key role in the initiation of parturition especially in response to local or systemic infection.

Keywords

Prothrombinase Fgl-2 parturition

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