A monoclonal antibody that recognizes a basolateral membrane protein in A6 epithelial cells

Methods for the isolation of sensory and primary cilia--an overview

Detailed proteomic analyses of mammalian olfactory and rod photoreceptor sensory cilia are now available, providing an inventory of resident ciliary proteins and laying the foundation for future studies of developmental and spatiotemporal changes in the composition of sensory cilia. Cilia purification methods that were elaborated and perfected over several decades were essential for these advances. In contrast, the proteome of primary cilia is yet to be established, because purification procedures for this organelle have been developed only recently. In this chapter, we review current techniques for the purification of olfactory and photoreceptor cilia, and evaluate methods designed for the selective isolation of primary cilia.

Global expression of simulated microgravity-responsive genes in Xenopus liver cells

The random positioning machine (RPM) is a method used to generate a simulated-microgravity environment at approximately 0 g. Using an RPM, we analyzed the global gene expression of A8 cells derived from the liver of adult Xenopus laevis. A range of genes on a Xenopus 44K-scale microarray were up- or downregulated two-fold or more: 43 genes (up, 36 genes; down, 7 genes) on culture day 5 in RPM, 74 genes (up, 48 genes; down, 26 genes) on day 8, 105 genes (up, 71 genes; down, 34 genes) on day 10, and 132 genes (up, 98 genes; down, 34 genes) on day 15. Five genes were upregulated two-fold or more throughout culturing in RPM, while only one gene was downregulated over the entire time. We then compared the expression patterns of the RPM-dependent genes in the A8 cells with those in A6 cells established from the kidney of adult Xenopus laevis. Six upregulated genes and three downregulated genes showed the same expression patterns throughout the culturing of A6 and A8 cells in RPM. Such globally responsive genes may play a common role in the cell response to simulated microgravity. We were particularly interested in the downregulation of SPARC in both cell types in RPM, which supported previous observations from simulated-microgravity experiments on earth or microgravity in space. We conclude that SPARC is plays a key role in the response of a cell to microgravity.

Dome formation and tubule morphogenesis by Xenopus kidney A6 cell cultures exposed to microgravity simulated with a 3D-clinostat and to hypergravity

Confluent high-density cell cultures of A6 cells derived from adult male Xenopus kidney exhibit spontaneous dome-formation at 1 g. To determine whether this morphogenetic property is altered by gravity, we used a three-dimensional (3D) clinostat to subject the cells to simulated microgravity, and a centrifuge to subject them to hypergravity. We used the generation orbit control method as the new rotation control system of the 3D-clinostat, not the random method. The growth of A6 cells was significantly enhanced by hypergravity, but significantly reduced by simulated microgravity. Dome formation by A6 cells at high confluence was inhibited under simulated microgravity conditions, whereas hypergravity promoted dome formation and induced tubule morphogenesis, compared to the control at 1 g. These results indicated that changes in gravity influence the morphogenetic properties of A6 cells, such as dome formation and tubule morphogenesis. When dome formation by A6 cells at high confluence was induced spontaneously in the control 1 g culture, the gene expression of the HGF family of pleiotropic factors, such as HGF-like protein (HLP) and growth factor-Livertine (GF-l.ivertine), an epithelial serine protease of channel activating protease 1 (CAP1), and Na+, K+-adenosine triphosphatase (ATPase), increased. Simulated microgravity increased the gene expression of activin A and reduced the gene expression of HLP, GF-Livertine, CAP1, and Na+, K+-ATPase. Hypergravity, on the other hand, decreased the gene expression of activin A and increased the gene expression of HLP, GF-Livertine, CAP1, and Na+, K+-ATPase. These results suggest that the effects of gravitational changes on expression of the HGF family member gene, CAP1, and Na+, K+-ATPase gene may be important for the cell growth, tubule morphogenesis, and dome formation of A6 cells in altered

Aldosterone induces early activation and late accumulation of Na-K-ATPase at surface of A6 cells

In A6 cells cultured on filters, aldosterone (10(-6) M) induces an early increase in the initial rate of ouabain binding to intact monolayers (in K-free buffer) that parallels an early increase in Na transport. This effect is independent of apical Na influx and precedes an increase in the synthesis of Na-K-adenosinetriphosphatase (ATPase) subunits. In the present study we observed in addition a late aldosterone-induced increase in the rate of ouabain binding (2.5 times from 3 to 120 h aldosterone). The role of Na-K-ATPase accumulation and/or translocation to the cell surface was tested by Western blotting, saturation ouabain binding, and cell-surface labeling using sulfosuccinimidobiotin or enzyme-mediated radioiodination. Only cell-surface beta 1-subunit was detected by blotting with streptavidin or autoradiography, because the alpha 1-subunit was not efficiently labeled. Three hours after hormone addition, none of the three parameters had increased significantly, whereas after 20 and 120 h similar increases (approximately 1.6 and 2.3 times, respectively) were detected by all three methods. In addition, it was shown that increasing intracellular Na with amphotericin B or a K-free preincubation also stimulated the rate of ouabain binding without increasing the surface labeling of beta 1-subunits. Taken together, these results suggest that a short aldosterone treatment or an increase in intracellular Na leads to an increase in the rate of ouabain binding that is due to an in situ activation of cell-surface Na-K-ATPase molecules. In contrast, the late increase in the rate of ouabain binding parallels an increase in the number of pumps.