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Odorants selectively activate distinct G protein subtypes in olfactory cilia
M Schandar1, K L Laugwitz, I Boekhoff
1Universität Stuttgart-Hohenheim, Institut für Physiologie, 70593 Stuttgart, Germany.
The Journal of Biological Chemistry
|June 27, 1998
Summary
Olfactory signal transduction uses distinct G protein pathways. Different odorants activate specific G protein subtypes, leading to either cAMP or IP3 formation, revealing dual olfactory signaling pathways.
Area of Science:
- Neuroscience
- Molecular Biology
- Biochemistry
Background:
- Chemoelectrical signal transduction in olfactory neurons relies on intracellular cascades.
- Heterotrimeric GTP-binding proteins (G proteins) are implicated in these signaling pathways.
Purpose of the Study:
- To identify specific G protein subtypes in olfactory cilia activated by odorant signals.
- To elucidate the roles of different G proteins in olfactory signal transduction.
Main Methods:
- Utilized subtype-specific antibodies against G protein alpha subunits to block second messenger responses.
- Employed activation-dependent photolabeling with [alpha-32P]GTP azidoanilide followed by immunoprecipitation.
- Investigated the effects of Gbeta antibodies on odorant-induced inositol 1,4,5-trisphosphate (IP3) formation.
Main Results:
- Antibodies against Gαs selectively inhibited odorant-induced cAMP formation.
- Antibodies against Gαo blocked odorant-induced IP3 formation.
- Photolabeling identified Gαs-like proteins activated by cAMP-inducing odorants and Gαo-like proteins by IP3-inducing odorants.
- Gβ antibodies inhibited IP3 formation, suggesting Gβγ subunit involvement.
Conclusions:
- Olfactory signaling involves at least two distinct transduction pathways.
- Different odorant subsets selectively activate specific G protein subtypes (Gαs and Gαo).
- Evidence supports dual pathways: one involving cAMP and Gαs, another involving IP3, phospholipase C, and Gαo/Gβγ subunits.