Fibulin-4 Accelerates Amyloid Formation by Binding with a Keratin 5 Peptide Fragment.

Keratins are the major amyloid fibril component in localized cutaneous amyloidosis. We analyzed the amyloid components in the skin of patients with localized cutaneous amyloidosis by immunohistochemical staining using antisera against extracellular matrix proteins and keratin 5 (K5). Fibulin-4 and K5 colocalized in the amyloid deposits. Using 14 synthetic peptides, we screened for amyloidogenic sequences in the C-terminal region of K5, including the α-helical rod domain and the tail domain. Two peptides stained with thioflavin T possessed a ß-sheet structure and formed amyloid-like fibrils. Among the amyloidogenic peptides, a peptide KT5-6 (YQELMNTKLALDVEIATYRKLLEGE) derived from the α-helical rod domain of K5 specifically bound to fibulin-4. In addition, amyloid formation of KT5-6 was accelerated by fibulin-4. These results suggest that degraded fragments of K5 containing the KT5-6 sequence form amyloid fibrils with fibulin-4. The data further suggest that degraded fragments of K5 and fibulin-4 have the potential to initiate cutaneous amyloidosis.

Elevated circulating TWEAK levels in systemic sclerosis: association with lower frequency of pulmonary fibrosis.

OBJECTIVE: To determine serum levels of tumor necrosis factor-related weak inducer of apoptosis (TWEAK) and its clinical associations in patients with systemic sclerosis (SSc). METHODS: Serum TWEAK levels from 70 patients with SSc were examined by ELISA. In a retrospective longitudinal study, sera from 23 patients with SSc were analyzed (followup 0.8-7.2 yrs). RESULTS: Serum TWEAK levels were elevated in patients with SSc (n = 70) compared with healthy controls (n = 31) and patients with systemic lupus erythematosus (n = 22). Among patients with SSc, there were no differences in serum TWEAK levels between limited cutaneous SSc and diffuse cutaneous SSc. Patients with SSc who had elevated TWEAK levels less often had pulmonary fibrosis and decreased vital capacity than those with normal TWEAK levels. In the longitudinal study, SSc patients with inactive pulmonary fibrosis or without pulmonary fibrosis consistently exhibited increased TWEAK levels, while those with active pulmonary fibrosis showed decreased TWEAK levels during the followup period. CONCLUSION: TWEAK levels were increased in patients with SSc, and associated with a lower frequency of pulmonary fibrosis in patients with SSc. TWEAK could be a protective factor against the development of pulmonary fibrosis in this disease and as such would be a possible therapeutic target.

Hypergravity induces phosphorylation of p53 at serine 15, but not an expression of p53-downstream genes.

We investigated the p53 signaling pathway induced by hypergravity in the human glioblastoma cell line A172. Hypergravity (20 x g) induced the accumulation of p53 and the phosphorylation of p53 at Ser-15. The phosphorylation of p53 with hypergravity was not inhibited by wortmannin, the PI3-kinase inhibitor. This indicated that the p53 signal pathway induced by hypergravity is different from other p53 signal pathways, such as that of the DNA damage signal. Hypergravity did not induce an expression of the genes Waf-1 or Bax, located downstream from p53. We also examined the expression of genes with hypergravity by using a DNA microarray containing oligo DNA from 30,000 human genes. Hypergravity (20 x g, 6 h) did induce the expression of some genes concerned with the cell signaling pathway and cytoskeleton of the cell, but not any of the p53-downstream genes. DNA microarray revealed the induction of many genes to enable the cells to adapt to the hypergravity environment.

Hypergravity modifies the signal transduction of ionizing radiation through p53.

To determine the possible effect of hypergravity to modify the signal transduction of ionizing radiation, we analyzed the accumulation of p53 and the expression of p53-dependent genes, Waf-1 and Bax, using the western blot analysis. Hypergravity (20 x g) induced the accumulation of p53 in the human glioblastoma cell line A172 after 3 h of incubation. Low-dose (0.5 Gy) irradiation to the cells accumulated p53 1.5 h after irradiation, and induced Waf-1 and Bax. Under the condition of hypergravity (20 x g), the peak of p53 accumulation was shifted from 1.5 h to 3 h after irradiation, and the inductions of Waf-1 and Bax were suppressed entirely. These results indicate that hypergravity modifies the signal transduction of ionizing radiation through p53 in the cells.