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Odorant receptors directly activate phospholipase C/inositol‐1,4,5‐trisphosphate coupled to calcium influx in Odora cells
Author(s) -
Liu Guang,
Badeau Robert M.,
Tanimura Akihiko,
Talamo Barbara R.
Publication year - 2006
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1111/j.1471-4159.2006.03667.x
Subject(s) - microbiology and biotechnology , calcium signaling , phospholipase c , adenylyl cyclase , biology , calcium , signal transduction , calcium in biology , receptor , olfactory receptor , calcium imaging , gq alpha subunit , chemistry , biochemistry , g protein coupled receptor , intracellular , organic chemistry
Mechanisms by which odorants activate signaling pathways in addition to cAMP are hard to evaluate in heterogeneous mixtures of primary olfactory neurons. We used single cell calcium imaging to analyze the response to odorant through odorant receptor (OR) U131 in the olfactory epithelial cell line Odora (Murrell and Hunter 1999), a model system with endogenous olfactory signaling pathways. Because adenylyl cyclase levels are low, agents activating cAMP formation do not elevate calcium, thus unmasking independent signaling mediated by OR via phospholipase C (PLC), inositol‐1,4,5‐trisphosphate (IP 3 ), and its receptor. Unexpectedly, we found that extracellular calcium is required for odor‐induced calcium elevation without the release of intracellular calcium, even though the latter pathway is intact and can be stimulated by ATP. Relevant signaling components of the PLC pathway and G protein isoforms are identified by western blot in Odora cells as well as in olfactory sensory neurons (OSNs), where they are localized to the ciliary zone or cell bodies and axons of OSNs by immunohistochemistry. Biotinylation studies establish that IP 3 receptors type 2 and 3 are at the cell surface in Odora cells. Thus, individual ORs are capable of elevating calcium through pathways not directly mediated by cAMP and this may provide another avenue for odorant signaling in the olfactory system.