Sodium/calcium exchanger expression in the mouse and rat olfactory systems

Abstract

Sodium/calcium (Na(+)/Ca(2+)) exchangers are membrane transport systems that regulate Ca(2+)-homeostasis in many eukaryotic cells. In olfactory and vomeronasal sensory neurons ligand-induced olfactory signal transduction is associated with influx and elevation of intracellular Ca(2+), [Ca(2+)](i). While much effort has been devoted to the characterization of Ca(2+)-related excitation and adaptation events of olfactory chemosensory neurons (OSNs), much less is known about mechanisms that return [Ca(2+)](i) to the resting state. To identify proteins participating in the poststimulus Ca(2+)-clearance of mouse OSNs, we analyzed the expression of three potassium (K(+))-independent (NCX1, 2, 3) and three K(+)-dependent (NCKX1, 2, 3) Na(+)/Ca(2+) exchangers. In situ hybridization showed that mRNAs of all six Na(+)/Ca(2+) exchangers coexist in neurons of the olfactory and vomeronasal systems, and that some are already detectable in the embryo. Of these, NCX1 and NCKX1 represent the most and least abundant mRNAs, respectively. Moreover, immunohistochemistry revealed that the NCX1, 2, and 3 proteins are expressed in nearly all neurons of the olfactory epithelium, the vomeronasal organ, the septal organ of Masera, and the Grueneberg ganglion. These three exchanger proteins display different expression profiles in dendrites, knobs, and plasma membranes of OSNs and in sustentacular cells. Furthermore, we show that NCX1 mRNA in rat olfactory mucosa is expressed as 8 alternative splice variants. This is the first comprehensive analysis of Na(+)/Ca(2+) exchanger expression in the mammalian olfactory system. Our results suggest that Ca(2+)-extrusion by OSNs utilizes multiple different Na(+)/Ca(2+) exchangers and that different subtypes are targeted to different subcellular compartments.

Mouse alarm pheromone shares structural similarity with predator scents

“…The potential pathway(s) implicated in the detection of chemical danger cues by GG neurons remain(s) to be identified. Putative signaling elements have already been described (21,31,(54)(55)(56)(57)(58)(59), suggesting that GG neurons might use different pathways from those present in MOE or VNO neurons. Some proteins identified have a temporal pattern of expression and/or a restricted localization implying the presence of neuronal subpopulations in the GG.…”

The long tale of the calcium activated Cl−channels in olfactory transduction

“…[24][25][26] More recently it has been shown that the potassium-dependent Na C /Ca 2C exchanger 4 (NCKX4) is expressed in the cilia of OSNs and plays the major role in Ca 2C extrusion and therefore, in controlling the termination of the odorant response. [27][28][29] A further contribution to Ca 2C dynamics inside the cilia of OSNs is given by mitochondria in the dendritic knob. Not only do they contribute to the low resting Ca 2C but also they are responsible for its clearance during odorant stimulation.…”

Phylogenic Outline of the Olfactory System in Vertebrates

“…These systems make the mammals possible to detect all essential elements for survival, such as food, danger and mates. There are two olfactory receptors other than the OE and the VNO, that is, the septal olfactory organ of Masera (SO) [2,10,29,46,53,64,70,76,80,81,93,94] and the Grueneberg ganglion (GG) [9,20,21,27,47,51,52,69]. They play some roles as olfactory subsystems in the mammals.…”