Vitamin D 3 upregulated protein 1 (VDUP1) is a 1,25-dihydroxyvitamin D 3 (1,25(OH) 2 D 3 ) upregulated protein, and it is induced by various stresses. In human tumor tissues, VDUP1 expression was downregulated. Upon stimulation by growth-inhibitory signals such as TGF-b1 and 1,25(OH) 2 D 3 , its expression was rapidly upregulated as the cell growth was retarded. The transfection of VDUP1 in tumor cells reduced cell growth. The VDUP1 expression was also increased when the cell-cycle progression was arrested. Transfection of VDUP1 induced cellcycle arrest at the G0/G1 phase, indicating that VDUP1 possesses a tumor-suppressive activity. In addition, it was found that VDUP1 interacted with promyelocytic leukemia zinc-finger, Fanconi anemia zinc-finger, and histone deacetylase 1, which are known to be transcriptional corepressors. VDUP1 itself suppressed IL-3 receptor and cyclin A2 promoter activity. Taken together, these results suggest that VDUP1 is a novel antitumor gene which forms a transcriptional repressor complex.

Vitamin D3 upregulated protein 1 (VDUP1) is a stress-response gene that is upregulated by 1,25(OH)2D3 in tumor cells. The in vivo roles of VDUP1 were investigated by producing mice lacking VDUP1 (VDUP1-/- mice). VDUP1-/- mice showed minimal changes in the development of T and B cells, but there was a profound reduction in the numbers of natural killer (NK) cells. As well, these mice showed decreased NK activity. In the VDUP1-/- mice, the expression of CD122 was reduced, demonstrating that VDUP1 is required for CD122 expression and NK maturation. In addition, severe lymphoid hyperplasia in the small intestine was observed in VDUP1-/- mice. Taken together, these results suggest that VDUP1 is a critical factor for the development and function of NK cells in vivo.

Stimulation of human lung fibroblast cells with TGF-β1 resulted in a transient burst of reactive oxygen species with maximal increase at 5 min after treatment. This reactive oxygen species increase was inhibited by the antioxidant, N-acetyl-l-cysteine (NAC). TGF-β1 treatment stimulated IL-6 gene expression and protein synthesis in human lung fibroblast cells. Antioxidants including NAC, glutathione, and catalase reduced TGF-β1-induced IL-6 gene expression, and direct H2O2 treatment induced IL-6 expression in a dose-dependent manner. NAC also reduced TGF-β1-induced AP-1 binding activity, which is involved in IL-6 gene expression. It has been reported that Ca2+ influx is stimulated by TGF-β1 treatment. EGTA suppressed TGF-β1- or H2O2-induced IL-6 expression, and ionomycin increased IL-6 expression, with simultaneously modulating AP-1 activity in the same pattern. PD98059, an inhibitor of mitogen-activated protein kinase (MAPK) kinase/extracellular signal-related kinase kinase 1, suppressed TGF-β1- or H2O2-induced IL-6 and AP-1 activation. In addition, TGF-β1 or H2O2 increased MAPK activity which was reduced by EGTA and NAC, suggesting that MAPK is involved in TGF-β1-induced IL-6 expression. Taken together, these results indicate that TGF-β1 induces a transient increase of intracellular H2O2 production, which regulates downstream events such as Ca2+ influx, MAPK, and AP-1 activation and IL-6 gene expression.

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The present structural study suggests that the uncleaved alpha1-antitrypsin has many folding defects which can be improved by mutations. These folding defects seem to be utilized in a coordinated fashion in the regulation of the conformational switch of alpha1-antitrypsin. Some of the defects, represented by the Phe51 region and possibly the Met374 and the Thr59 regions, are part of the sheet-opening mechanism.

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The metastability of inhibitory serpins (serine proteinase inhibitors) is thought to play a key role in the facile conformational switch and the insertion of the reactive center loop into the central ␤-sheet, A-sheet, during the formation of a stable complex between a serpin and its target proteinase. We have examined the folding and inhibitory activity of a very stable variant of human ␣ 1 -antitrypsin, a prototype inhibitory serpin. A combination of seven stabilizing single amino acid substitutions of ␣ 1 -antitrypsin, designated Multi-7, increased the midpoint of the unfolding transition to almost that of ovalbumin, a non-inhibitory but more stable serpin. Compared with the wild-type ␣ 1 -antitrypsin, Multi-7 retarded the opening of A-sheet significantly, as revealed by the retarded unfolding and latency conversion of the native state. Surprisingly, Multi-7 ␣ 1 -antitrypsin could form a stable complex with a target elastase with the same kinetic parameters and the stoichiometry of inhibition as the wild type, indicating that enhanced A-sheet closure conferred by Multi-7 does not affect the complex formation. It may be that the stability increase of Multi-7 ␣ 1 -antitrypsin is not sufficient to influence the rate of loop insertion during the complex formation.

Z (Glu 342 3 Lys) and S iiyama (Ser 53 3 Phe) genetic variations of human ␣ 1 -antitrypsin (␣ 1 -AT) cause a secretion blockage in the hepatocytes, leading to ␣ 1 -AT deficiency in the plasma. Using in vitro folding analysis, we have shown previously that these mutations interfere with the proper folding of polypeptides. To understand the fundamental cause for the secretion defect of the Z and S iiyama variants of ␣ 1 -AT, we investigated in vivo folding and stability of these variant ␣ 1 -AT using the secretion system of yeast Saccharomyces cerevisiae. Various thermostable mutations suppressing the folding block of the Z variant in vitro corrected the secretion defect as well as the intracellular degradation in the yeast secretion system. Significantly, the extent of suppression in the secretion defect of Z protein was proportional to the extent of suppression in the folding defect, assuring that the in vivo defect associated with the Z variant is primarily derived from the folding block. In contrast, the folding and secretion efficiency of S iiyama was not much improved by the same mutations. In addition, none of the rarely secreted S iiyama ␣ 1 -AT carrying the stabilizing mutations for the wild type and Z variant were active. It appears that the major defect in S iiyama variant is the loss of stability in contrast to the kinetic block of folding in the Z variant.