Mezler M et al. (2001), Identification of a nonmammalian Golf subtype: ...

XB-ART-8277

J Comp Neurol 2001 Oct 29;4394:400-10. doi: 10.1002/cne.1358.

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Identification of a nonmammalian Golf subtype: functional role in olfactory signaling of airborne odorants in Xenopus laevis.

Mezler M , Fleischer J , Conzelmann S , Korchi A , Widmayer P , Breer H , Boekhoff I .

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Attempts to identify the Galpha subtypes in the two compartments of the olfactory system from Xenopus, which are supposed to be specialized for detecting aquatic and volatile odorous compounds, revealed that a Galpha(o1) subtype is characteristic for the "water nose," the lateral diverticulum, whereas a novel Galpha(s) subtype predominates in the "air nose," the medial diverticulum. The newly identified Galpha(s)-type is more closely related to Galpha(olf) of rat and human than to the known Galpha(s)-isoform of Xenopus; it is therefore considered the first identified nonmammalian Galpha(olf) subtype. Sequence comparison of Galpha(olf) from amphibia and mammals revealed a particular conservation within the alpha-helical domains, which are supposed to control the GDP/GTP-exchange rate. The selective expression of different Galpha subtypes in the two anatomically separated and functionally specialized nasal compartments parallels the expression of distinct classes of olfactory receptors. Moreover, biochemical analysis revealed that stimulation with appropriate odorous compounds elicits the formation of inositol trisphosphate in the lateral diverticulum. In contrast, cyclic adenosine monophosphate signals were induced in the medial diverticulum, and this response appears to be mediated by the novel Galpha(olf) subtype. The data indicate that olfactory sensory neurons in each of the nasal cavities are equipped not only with defined sets of receptor types but also with a distinct molecular machinery for the chemo-electrical transduction process.

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Species referenced: Xenopus laevis
Genes referenced: gnai1 gnai3 gnal gnao1 gnaq gnas gnat1 suclg1
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	Fig. 4. In situ hybridization of coronal sections through the sensory epithelium of the medial and lateral diverticulum of Xenopus using Ga subtype-specific antisense RNA probes. Coronal sections were hybridized with DIG-labeled antisense RNA specific for Gasx2 (A,B) and Gaox1 (C,D). Hybridization with the Gasx2-specific probe intensely labeled the olfactory sensory cell layer (A), whereas hybridization signals in the lateral diverticulum are low (B). Hybridization with the Gaox1-specific probe led to very few hybridization signals in the medial diverticulum (C), whereas many sensory cells in the lateral diverticulum were labeled (D). oe, olfactory neuron layer; sc, sustentacular cells; bs, basal cells; lp, lamina propria; bg, Bowman‘s glands. Scale bar 5 20 mm.
	Fig. 5. Immunohistochemical localization of G protein a subtypes in the olfactory epithelium of the medial and lateral diverticulum. Cryostat sections of the medial (A) and lateral diverticulum (B) of the Xenopus nasal cavity were probed with a 1:1000 dilution of a Gas/olf - or Gao1-specific antibody. Note that the immunoreactivity detectable for the Gas/olf -specific antibody is restricted to the cilia layer of the sensory epithelium (se); at the transition area toward the respiratory epithelium (re), indicated by an arrowhead, immunoreactivity disappeared. mp, melanophores. Scale bar 5 10 mm.
	Fig. 3. Tissue-specific expression of Ga genes by RT-PCR. RNA isolated from the medial diverticulum (MD) or the lateral diverticulum (LD) was subjected to RT-PCR analysis using degenerated primers corresponding to common sequences of Gas (A) and Gao (B). PCR products were size-fractionated on an agarose gel, resulting in bands of the predicted size. The position of the 100-bp ladder molecular weight marker is shown on the left.