The sialidase NEU3 promotes pulmonary fibrosis in mice.

BACKGROUND: Sialic acid is often the distal sugar on glycoconjugates, and sialidases are enzymes that remove this sugar. In fibrotic lesions in human and mouse lungs, there is extensive desialylation of glycoconjugates, and upregulation of sialidases including the extracellular sialidase NEU3. In the bleomycin model of pulmonary fibrosis, mice lacking NEU3 (Neu3-/-) showed strongly attenuated bleomycin-induced weight loss, lung damage, inflammation, and fibrosis. This indicates that NEU3 is necessary for the full spectrum of bleomycin-induced pulmonary fibrosis. METHODS: To determine if NEU3 is sufficient to induce pulmonary fibrosis, recombinant murine NEU3 and a mutated inactive recombinant murine NEU3 protein were produced. Mice were given recombinant NEU3 proteins by oropharyngeal aspiration, either alone or 10 days after bleomycin challenge. Over the course of 21 days, mice were assessed for weight change, and after euthanasia, bronchoalveolar lavage fluid cells and lung tissue were assessed for inflammation and fibrosis. RESULTS: Aspiration of recombinant murine NEU3 caused inflammation and fibrosis in the lungs, while inactive NEU3 caused inflammation but not fibrosis. Mice were also treated with recombinant murine NEU3 starting 10 days after bleomycin. In male but not female mice, recombinant murine NEU3 increased inflammation and fibrosis. Inactive NEU3 did not enhance bleomycin-induced lung fibrosis. CONCLUSION: These results suggest that NEU3 is sufficient to induce fibrosis in the lungs, that aspiration of NEU3 has a greater effect on male mice, and that this effect is mediated by NEU3's enzymic activity.

Changes in lung sialidases in male and female mice after bleomycin aspiration.

Aim of the study: Sialidases, also called neuraminidases, are enzymes that cleave terminal sialic acids from glycoconjugates. In humans and mice, lung fibrosis is associated with desialylation of glycoconjugates and upregulation of sialidases. There are four mammalian sialidases, and it is unclear when the four mammalian sialidases are elevated over the course of inflammatory and fibrotic responses, whether tissue resident and inflammatory cells express different sialidases, and if sialidases are differentially expressed in male and females. Materials and Methods: To determine the time course of sialidase expression and the identity of sialidase expressing cells, we used the bleomycin model of pulmonary fibrosis in mice to examine levels of sialidases during inflammation (days 3 - 10) and fibrosis (days 10 - 21). Results: Bleomycin aspiration increased sialidase NEU1 at days 14 and 21 in male mice and day 10 in female mice. NEU2 levels increased at day 7 in male and day 10 in female mice. NEU3 appears to have a biphasic response in male mice with increased levels at day 7 and then at days 14 and 21, whereas in female mice NEU3 levels increased over 21 days. In control mice, the sialidases were mainly expressed by EpCAM positive epithelial cells, but after bleomycin, epithelial cells, CD45 positive immune cells, and alveolar cells expressed NEU1, NEU2, and NEU3. Sialidase expression was higher in male compared to female mice. There was little expression of NEU4 in murine lung tissue. Conclusions: These results suggest that sialidases are dynamically expressed following bleomycin, that sialidases are differentially expressed in male and females, and that of the four sialidases only NEU3 upregulation is associated with fibrosis in both male and female mice.

Annotating Putative D. discoideum Proteins Using I-TASSER.

Using Gene Ontology annotation in any aspect or using any evidence code, we found that approximately 14% percent of predicted D. discoideum proteins have no GO annotations and no obvious similarity to any annotated protein across diverse organisms. We have been systematically examining these unannotated protein sequences using software that predicts a protein structure and then compares the predicted structure to known structures.