The ovine urokinase plasminogen activator and its receptor cDNAs: molecular cloning, characterization and expression...

The activation of plasminogen plays a crucial role in a variety of extracellular proteolytic events such as, fibrinolysis, cell migration, ovulation, involution of the mammary gland and the activation of other protease classes and growth factors. In this paper we describe the isolation of the full-length cDNAs of ovine urokinase plasminogen activator (u-PA) and its receptor (u-PAR) using a polymerase chain reaction based strategy. The ovine u-PA cDNA comprised of 2350 bp and it is characterized by a coding region of 1302 bp, and 5'- and 3'-UTR regions of 129 and 919 bp, respectively. The deduced amino acid sequence consists of 433 amino acids. The ovine u-PAR cDNA is comprised of 1247 bp and it is characterized by a coding region of 957 bp and 5'- and 3'-UTR regions of 44 and 246 bp respectively. The deduced amino acid sequence consists of 318 amino acids. Three-dimensional models of the putative protein products of both cDNAs showed that the proteins bear a high similarity with their human counterparts. Real-time PCR revealed high levels of u-PA expression in the adipose tissue, followed by that in mammary gland and kidney. Lower levels of expression were detected in the adrenal glands, heart, ovaries, spleen, liver and cerebellum. A similar pattern was observed in u-PAR expression with noticeably lower levels of expression in heart, liver and cerebellum. To the best of our knowledge, this is the first paper reporting expression of u-PA and u-PAR in the adipose tissue. These data strengthen the suggestion that adipose tissue functions as an endocrine organ besides an energy storage organ. Furthermore, u-PA and u-PAR mRNA levels were 7 and 8.5 fold higher respectively in involuting mammary tissue obtained from non-lactating ewes compared to that detected in mammary tissue obtained from lactating ewes. These data are consistent with the notion that upregulation of u-PA and u-PAR expression may play a key role in the process of involution of the mammary gland.