ABSTRACT
Protein C inhibitor (PCI) is a plasma serine protease inhibitor of activated protein
C, which is the main protease of the anticoagulant protein C pathway. Human PCI is
synthesized in the liver, kidney, and several reproductive organs (testis, seminal
vesicle, and prostate). In the present study, we characterized cis-elements of the human PCI gene required for expression in the hepatoma-derived cell
line, HepG2 cells, and also evaluated rat PCI mRNA expression, particularly on the
effect of androgen in rat reproductive tissues. On the PCI gene expression in HepG2
cells, transient expression assays using several deletion mutants and site-directed
mutants of the human PCI gene and gel mobility shift assays using several synthetic
oligonucleotides showed that the Sp1-binding site (residues -302 to -294) and the
upstream AP2-binding site (residues -350 to -343) play roles as the promoter and the
enhancer, respectively. Both the A-activator-binding site (residues -422 to -414)
and the interferon-γ response element (residues -164 to -157) serve as the silencer.
In the study on PCI mRNA expression in the reproductive organs, we first cloned rat
PCI cDNA and then evaluated the effect of androgen on the PCI mRNA expression. The
isolated rat PCI cDNA contained a 1,218-bp coding region of a 406-amino acid precursor
protein. The deduced amino acid sequence of rat PCI showed an 85.7% and 62.2% homology
with that of mouse and human PCIs, respectively. Northern blot analysis showed that
rat PCI mRNA was strongly expressed in the seminal vesicles, moderately in the testes,
but not in the liver. PCI mRNA expression in seminal vesicles and testes increased
during the process of development. The PCI mRNA expression in seminal vesicles was
significantly decreased after castration or after 17β-estradiol treatment. Treatment
with testosterone in the castrated rats significantly enhanced its mRNA expression.
These findings suggest that the PCI gene expression in rat seminal vesicles is under
androgen control.
KEYWORD
Protein C inhibitor gene - transcriptional gene regulation -
cis-elements - reproductive tissues - androgen control