Localization of a G protein G_i2 in the cilia of rat ependyma, oviduct and trachea

Abstract

In previous studies, the localization of a pertussis toxin-sensitive G protein was demonstrated in ependymal cilia, but the identification of the subtype of G protein was inconsistent. To clarify this issue, we studied the localization of Goalpha, Gi1alpha, Gi3alpha and Gi2alpha in the ciliated ependymal cells and in the cilia of some other tissues of rats using specific antibodies. The cilia of the ependymal cells that line the ventricular cavity of the brain were intensely immunoreactive for Gi2alpha, but not for Goalpha, Gi1alpha or Gi3alpha. Immunoblot analysis demonstrated higher levels of Gi2alpha in the ependymal cilia-rich pellet than in the motor area of the parietal cortex. At the ultrastructural level, the immunoreactivity specific for Gi2alpha was found predominantly in the cilia, but rarely in the microvilli or the basal bodies of ependymal cells. In cross-sections, the immunoreactivity specific for Gi2alpha was observed only in cell membranes, in particular, in the inner electron-dense leaflet of the trilaminar structure. In addition to that in the ependymal cilia, such specific localization of Gi2alpha was observed in the motile cilia in other tissues, including the oviduct and trachea. By contrast, the stereocilia in the ductus deferens were not immunopositive for Gi2alpha. These findings suggest that Gi2 might play an important role in the signal transduction in ciliary membrane-associated function(s) of the ependymal cells, oviduct and trachea.

Ciliary subcellular localization of TGR5 determines the cholangiocyte functional response to bile acid signaling

“…Several published observations support our findings. For example, G␣ i2 , a member of the G␣ i family, is localized to motile cilia in the rat ependyma, oviduct, and trachea (35) and in the human endometrium and fallopian tubes (30). G␣ i1 , G␣ i2 , and G␣ i3 are distributed between the base and shaft of the primary cilium when expressed in cultured cerebellar granular neuronal precursors (1).…”

Characterization of a Targeting Motif for a Flagellar Membrane Protein in Leishmania enriettii

“…For example, Caenorhabditis elegans expresses ODR-10 (a seven-transmembrane domain receptor), OSM-9 (a cation channel), and ODR-3 (a G␣ protein) that localize to the cilia of AWA olfactory neurons (4 -7). Mammalian ependymal cells, oviduct, and trachea contain a G protein subtype (G i2 ) that localizes predominantly in cilia (8). In addition to distinct protein compositions, considerable evidence has accumulated that flagella and cilia exhibit lipid compositions distinct from other domains of the plasma membrane (9).…”

Intracerebroventricular antisense knockdown of Gαi2 results in ciliary stasis and ventricular dilatation in the rat

“…In contrast, Gα i2 has a highly restricted localization in the ventricle-surrounding areas. In the rat brain, Gα i2 is localized in the subventricular zone, the rostral migratory stream [4], the accessory olfactory bulb [5] and the ependymal cilia [6]. Such a specific localization implies that Gα i2 may well subserve physiological function distinct from those of the other Gα subunits.…”

“…Such a specific localization implies that Gα i2 may well subserve physiological function distinct from those of the other Gα subunits. Moreover, Gα i2 is also present in motile cilia which have a characteristic 9+2 ultrastructure in different peripheral tissues, such as rat oviduct and trachea [6]. This may mean that the Gα i2 subunit plays a specific, regulatory role in ciliary function.…”

“…Although the morphology of the ciliated epithelium at the interface between the cerebrospinal fluid (CSF) and the brain parenchyma has been studied in detail [17-20], ependymal functions have remained largely unexplored. The highly restricted anatomical localization of Gα i2 in the ependymal cilia and the subventricular areas [4,6] makes this subtype a particularly attractive target for specific and temporally controlled knockdown by icv-delivered antisense-oligodeoxynucleotides (AS-ODNs) without the fear for development of compensatory mechanisms, which were evident in previous studies with Gα i2 knockout mice [9]. Our data shows that knockdown of Gα i2 by specific antisense oligonucleotide caused irreversible, unilateral ventricular dilatation in rat in vivo , and ciliary stasis on cultured rat ependymal cells in vitro .…”