Annexin VII: an astroglial protein exhibiting a Ca2+-dependent subcellular distribution.
ABSTRACT A fundamental issue in neuronal and glial cells is how intracellular rises in Ca2+ are coupled to signaling cascades and changes in subcellular morphology. We studied the expression and localization of annexin VII (synexin), a Ca(2+)-/GTP-dependent membrane fusion protein, in the human CNS. Here, we demonstrate the presence of two annexin VII isoforms (47 and 51 kDa) in human brain tissue as well as its exclusive expression in astroglial cells. An in vitro study of astrocyte-derived C6 rat glioblastoma cells expressing a GFP tagged annexin VII fusion protein demonstrates a sequential redistribution of the fusion protein in response to rising intracellular Ca2+ concentrations. Our findings indicate a role of annexin VII in the regulation of intracellular Ca(2+)-dependent processes in astroglial cells.
- SourceAvailable from: Avinash Chander[Show abstract] [Hide abstract]
ABSTRACT: Membrane fusion between the lamellar bodies and plasma membrane is an obligatory event in the secretion of lung surfactant. Previous studies have postulated a role for annexin A7 (A7) in membrane fusion during exocytosis in some cells including alveolar type II cells. However, the intracellular trafficking of A7 during such fusion is not described. In this study, we investigated association of endogenous A7 with lamellar bodies in alveolar type II cells following treatment with several secretagogues of lung surfactant. Biochemical studies with specific antibodies showed increased membrane-association of cell A7 in type II cells stimulated with agents that increase secretion through different signaling mechanisms. Immuno-fluorescence studies showed increased co-localization of A7 with ABCA3, the lamellar body marker protein. Because these agents increase surfactant secretion through activation of PKC and PKA, we also investigated the effects of PKC and PKA inhibitors, bisindolylmaleimideI (BisI) and H89, respectively, on A7 partitioning. Western blot analysis showed that these inhibitors prevented secretagogue-mediated A7 increase in the membrane fractions. These inhibitors also blocked increased co-localization of A7 with ABCA3 in secretagogue-treated cells, as revealed by immuno-fluorescence studies. In vitro studies with recombinant A7 showed phosphorylation with PKC and PKA. The cell A7 was also phosphorylated in cells treated with surfactant secretagogues. Thus, our studies demonstrate that annexin A7 relocates to lamellar bodies in a phosphorylation-dependent manner. We suggest that activation of protein kinase promotes phosphorylation and membrane-association of A7 presumably to facilitate membrane fusion during lung surfactant secretion.Biochimica et Biophysica Acta 09/2011; 1813(12):2017-25. · 4.66 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer death in China. This study investigated the effects of Annexin A7 (ANXA7) on the inhibition of HCC lymph node metastasis in a mouse model. The stable knockup and knockdown of Annexin A7-expressing HCC cells using Annexin A7 cDNA and shRNA vectors, respectively, were injected into a mouse footpad to establish primary and metastatic tumors in mice. On the 14th, 21st, and 28th days after HCC cells inoculation, the mice were sacrificed for inspection of primary and secondary tumors and immunohistochemistry of Annexin A7 expression. The lymph node metastasis rate of the FANXA7-control group was 77%, and the lymph node metastasis rate of the FANXA7-down group was 100% (p < 0.05). In contrast, the lymph node metastasis rate of the PANXA7-up group was 0% and that of the PANXA7-control group was 36% (p < 0.05). Furthermore, immunohistochemistry experiments revealed that the subcellular localization of Annexin A7 protein in both primary and lymph node-metastasized tumors was mainly in the cytosol. In addition, the expression of the 47 kDa and 51 kDa isoforms of Annexin A7 protein changed during tumor progression. This study indicated that Annexin A7 expression was able to inhibit HCC lymph node metastasis, whereas knockdown of Annexin A7 expression significantly induced HCC metastasis to local lymph nodes.BMC Cancer 11/2013; 13(1):522. · 3.32 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: The genes coding for PGYRPs (proline-, glycine- and tyrosine-rich proteins) are widely distributed across eukaryotes and have been proposed to have critical role in plant development, especially in response to environmental stresses. In this study, total of 12 soybean PGYRPs (GmPGYRP1-12) were identified from the soybean genome database for the first time and full-length cDNA and DNA sequences of GmPGYRP7 was cloned. GmPGYRP1-12 genes encoded a set of small predicted proteins (<120 aa) with molecular mass of 7.20-13.29 kDa and isoelectric point of 4.06-6.57. All GmPGYRPs contained three exons and two introns with fixed occurring sites within genomic DNA sequences. In the putative GmPGYRP sequences, 4 amino acids (proline, glycine, tyrosine, and glutamine) account for more than 39% of the total protein composition. GmPGYRPs had a relatively flexible GYPPX motif followed by a highly conserved cysteine-rich domain (GCLAAXCCCCXLXC) and showed high similarity to other known PGYRPs, especially in C-terminal region. Most of PGYRPs can be divided into five subgroups according to phylogenetic analysis. The transcripts of GmPGYRP1, 3, 5, and 7, representing different PGYRP subgroups, appeared in different organs including seedling leaves, stems, roots, flowers, and developing seeds, but mainly accumulated in seedling roots. Furthermore, the expression of GmPGYRP1, 3, 5, and 7 was significantly regulated by drought, salt and cold, but obviously repressed by abscisic acid (ABA) at early stage. Our data suggest that GmPGYRP genes encoding a class of conservative XYPPX-repeat proteins probably play an important role in plant development as well as in response to abiotic stresses.Molecular Biology Reports 11/2010; 38(4):2739-50. · 1.96 Impact Factor