Sodium/calcium (Na(+)/Ca(2+)) exchangers (NCX) are membrane transporters that play an essential role in maintaining the homeostasis of cytosolic Ca(2+) for cell signaling. We demonstrated the Na(+)/Ca(2+)-exchange function of an NCX from Methanococcus jannaschii (NCX_Mj) and report its 1.9 angstrom crystal structure in an outward-facing conformation. Containing 10 transmembrane helices, the two halves of NCX_Mj share a similar structure with opposite orientation. Four ion-binding sites cluster at the center of the protein: one specific for Ca(2+) and three that likely bind Na(+). Two passageways allow for Na(+) and Ca(2+) access to the central ion-binding sites from the extracellular side. Based on the symmetry of NCX_Mj and its ability to catalyze bidirectional ion-exchange reactions, we propose a structure model for the inward-facing NCX_Mj.

This study demonstrated that cFN isoforms are expressed and induced in HTM cells by TGF-β2. Also, increased EDA isoform protein levels were seen in GTM tissues. Our findings suggest that induction of cFN isoform expression in the TM ECM may be a novel pathologic mechanism involved in the TM changes associated with glaucoma.

Serine protease inhibitors (serpins) regulate the activities of circulating proteases. Serpins inhibit proteases by acylating the serine hydroxyl at their active sites. Before deacylation and complete proteolysis of the serpin can occur, massive conformational changes are triggered in the serpin while maintaining the covalent linkage between the protease and serpin. Here we report the structure of a serpin-trypsin Michaelis complex, which we visualized by using the S195A trypsin mutant to prevent covalent complex formation. This encounter complex reveals a more extensive interaction surface than that present in small inhibitor-protease complexes and is a template for modeling other serpin-protease pairs. Mutations of several serpin residues at the interface reduced the inhibitory activity of the serpin. The serine residue C-terminal to the scissile peptide bond is found in a closer than usual interaction with His 57 at the active site of trypsin.

Glaucoma is a leading cause of irreversible vision loss and is associated with fibrotic changes in two ocular tissues-the optic nerve head (ONH) and trabecular meshwork (TM). We investigated the differences in extracellular matrix components (ECM) including collagen, elastin, transforming growth factor beta-2, type-II receptor (TGFβRII) and Galectin3 (Gal3) in the glaucomatous human eyes to quantify fibrotic changes in ONH and TM. Glaucomatous and control human donor eyes were prepared for chemical and immunological staining to quantify ECM protein expression in the TM and ONH. Chemical staining included: Trichrome (collagen), Vernhoeff-Van Giesen (elastin) and Sirius Red (collagen). Immunohistochemistry was used to determine levels of Gal3 and TGFβ2RII. Quantitative analyses were performed using Image J software. Student's t-test was used to compare groups and Pearson's test was used to determine correlations P-values of 0.05 (or less) were considered statistically significant. Deposition of ECM proteins was elevated in glaucomatous tissues. There was increased collagen (P = 0.0469), Gal3 (P < 0.0001) and TGFβ2RII (P = 0.0005) in the TM of glaucomatous eyes. Likewise, collagen (P = 0.0517) and Galectin3 (P = 0.041) were increased in the ONH glaucomatous eyes. There was a correlation of TGFβRII with Gal3 in the TM (P < 0.0001) and optic nerve (P = 0.0003). The TM and ONH of glaucomatous eyes showed increased expression of ECM proteins supporting a fibrotic pathology. Galectin3 and TGFβ-2R II showed a positive correlation in TM and optic nerve supporting co-localization and suggesting their potential role in the glaucoma fibrotic process. Clin. Anat. 31:1031-1049, 2018. © 2018 The Authors. Clinical Anatomy published by Wiley Periodicals, Inc. on behalf of American Association of Clinical Anatomists.

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