Single Ca2+-activated Cl− channel currents recorded from toad olfactory cilia

Abstract

BackgroundOdor transduction, occurring in the chemosensory cilia of vertebrate olfactory sensory neurons, is triggered by guanosine triphosphate-coupled odor receptors and mediated by a cyclic adenosine monophosphate (cAMP) signaling cascade, where cAMP opens cationic non-selective cyclic nucleotide-gated (CNG) channels. Calcium enters through CNG gates Ca2+-activated Cl− channels, allowing a Cl− inward current that enhances the depolarization initiated by the CNG-dependent inward current. The anoctamin channel 2, ANO2, is considered the main Ca2+-activated Cl− channel of olfactory transduction. Although Ca2+-activated Cl− channel-dependent currents in olfactory sensory neurons were reported to be suppressed in ANO2-knockout mice, field potentials from their olfactory epithelium were only modestly diminished and their smell-dependent behavior was unaffected, suggesting the participation of additional Ca2+-activated Cl− channel types. The Bestrophin channel 2, Best2, was also detected in mouse olfactory cilia and ClCa4l, belonging to the ClCa family of Ca2+-activated Cl− channels, were found in rat cilia. Best2 knock-out mice present no electrophysiological or behavioral impairment, while the ClCa channels have not been functionally studied; therefore, the overall participation of all these channels in olfactory transduction remains unresolved.ResultsWe explored the presence of detectable Ca2+-activated Cl− channels in toad olfactory cilia by recording from inside-out membrane patches excised from individual cilia and detected unitary Cl− current events with a pronounced Ca2+ dependence, corresponding to 12 and 24 pS conductances, over tenfold higher than the aforementioned channels, and a approx. fivefold higher Ca2+ affinity (K0.5 = 0.38 µM). Remarkably, we observed immunoreactivity to anti-ClCa and anti-ANO2 antibodies in the olfactory cilia, suggesting a possible cooperative function of both channel type in chemotransduction.ConclusionsThese results are consistent with a novel olfactory cilia channel, which might play a role in odor transduction.

A CLCA regulatory protein present in the chemosensory cilia of olfactory sensory neurons induces a Ca2+-activated Cl− current when transfected into HEK293

“…This study reveals that CLCA4L can induce the HEK293 Ca 2+ -activated Cl − current, thus mimicking CLCA1. Importantly, we also detected co-expression of CLCA with ANO2 in the cilia, as previously shown in toad olfactory sensory neurons [ 9 ]. The evidence provided is consistent with a possible role of CLCA in odor transduction, regulating ANO2.…”

“…The ANO2-dependent current amplifies the depolarization initiated by the cationic current [ 13 , 14 ]. A CLCA protein, presumably CLCA4L, was previously detected in olfactory cilia [ 7 , 9 ]. We now document that this protein and ANO2 co-exist in these organelles.…”

“…The endogenous expression of CLCA4L mRNA in OSNs [ 7 ], together with the presence of CLCA in their cilia co-expressing with ANO2, is consistent with a modulatory function over ANO2, with a possible role in odor transduction. Interestingly, CLCA4L had also been found in toad olfactory cilia [ 9 ], suggesting a widely conserved function in a wide range of animals.…”

Altered mastication adversely impacts morpho-functional features of the hippocampus: A systematic review on animal studies in three different experimental conditions involving the masticatory function

“…The following studies met the inclusion criteria: 1) studies on soft-diet feeding [2,[15][16][17][18][19][20][21][22]; 2) studies on tooth extraction [23][24][25][26][27][28][29][30][31][32][33][34][35][36]; 3) studies on bite-raising [37][38][39][40][41].…”

Odor-Induced Multi-Level Inhibitory Maps inDrosophila

“…Here, odor stimulation leads to a membranecurrent composed of a cationic and a delayed Clcomponent (Kurahashi and Yau, 1993). Although Cl -conductance is in most cases associated with neuronal inhibition, this Clcurrent amplifies the olfactory signal by Clefflux through a Ca 2ϩ -activated Clchannel which is most likely mediated by anoctamin-2 (ANO2; Lowe and Gold, 1993;Stephan et al, 2009;Delgado et al, 2016). The insect olfactory signal transduction is crucially different from that of vertebrates in two aspects: First, olfactory receptors of the OR and IR type are ionotropic receptors mediating excitatory cation influx (Sato et al, 2008;Wicher et al, 2008;Rytz et al, 2013).…”