Localization of a serine proteinase inhibitor, B-43, in the bovine pancreas

Localization of TFPI-2 in the nucleus modulates MMP-2 gene expression in breast cancer cells

TFPI-2 has recently been recognized as a tumor suppressor, which not only plays a fundamental role in modulation of ECM integrity, but also involves the regulation of many oncogenes. In this study, we investigated the potential mechanism of TFPI-2 in the suppression of breast cancer growth and invasion. We showed that, with either over-expression of TFPI-2 or after treatment with exogenous rTFPI-2, breast cancer cells exhibited reduced proliferation and invasion. We demonstrated that in addition to being secreted, TFPI-2 was also distributed throughout the cytoplasm and nucleus. Nuclear localization of TFPI-2 contributed to inhibition of MMP-2 mRNA expression, which could be reversed after the nuclear localization signal was deleted. In the nucleus, interaction of TFPI-2 with Ap-2α attenuated the binding of AP-2α to the MMP-2 promoter, therefore reducing the transcriptional activity of the gene. Our results suggest that one of the mechanisms by which TFPI-2 inhibits breast cancer cell invasion could be via the regulation of MMP-2 gene transcription.

Human tissue factor pathway inhibitor-2 is internalized by cells and translocated to the nucleus by the importin system

Tissue factor pathway inhibitor-2 (TFPI-2) is a serine proteinase inhibitor that induces caspase-mediated apoptosis when offered to a variety of tumor cells. In order to investigate the mechanism of TFPI-2-induced apoptosis, we initially studied the uptake and trafficking of TFPI-2 by HT-1080 cells. Exogenously offered TFPI-2 was rapidly internalized and distributed in both the cytosolic and nuclear fractions. Nuclear localization of TFPI-2 was also detected in a variety of endothelial cells constitutively expressing TFPI-2. Nuclear localization of TFPI-2 required a NLS sequence located in its Lys/Arg-rich C-terminal tail comprising residues 191-211, as a TFPI-2 construct lacking the C-terminal tail failed to localize to the nucleus. Complexes of TFPI-2 and importin-alpha were co-immunoprecipitated from cell lysates of HT-1080 cells either offered or overexpressing this protein, providing evidence that TFPI-2 was shuttled to the nucleus by the importin system. Our results provide the initial description of TFPI-2 internalization and translocation to the nucleus in a number of cells.

The expression and localization of serine proteinase inhibitor PI-6 mRNA in developmental and ischemic mouse brain

A serine proteinase inhibitor, PI-6, is a member of the serine proteinase inhibitor (serpin) superfamily. In the present study, we investigated the developmental expression of PI-6 in the mouse brain and the effect of experimental ischemia on the expression of PI-6 in the adult brain. Northern blot analysis showed a high level of expression of PI-6 mRNA in brain stem and diencephalon as compared with other regions in the adult brain. The expression of PI-6 mRNA in the whole brain was increased gradually until 11 days after birth and was decreased again in the adult brain. In situ hybridization analysis revealed that the mRNA was localized in pyramidal cell layer of the post-natal hippocampus, especially in CA3 region, and in layer V of the cerebral cortex. In the brain stem, two specific motor nuclei, the facial nucleus and the motor nucleus of trigeminal nerve, which are important to active feeding, were strongly positive for PI-6 mRNA. Brain ischemia induced by bilateral ligation of the common carotid artery led to an increase in PI-6 mRNA expression in the whole brain, accompanied by the degeneration of hippocampal pyramidal cells. These results indicate distinct temporal and spatial expression of PI-6 in the mouse brain and suggest the involvement of PI-6 in the maturation of neurons and degenerative and regenerative processes.