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Basic properties of an inositol 1,4,5‐trisphosphate‐gated channel in carp olfactory cilia
Author(s) -
Cadiou Hervé,
Sienaert Ilse,
Vanlingen Sara,
Parys Jan B.,
Molle Gérard,
Duclohier Hervé
Publication year - 2000
Publication title -
european journal of neuroscience
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 206
eISSN - 1460-9568
pISSN - 0953-816X
DOI - 10.1046/j.1460-9568.2000.00166.x
Subject(s) - ruthenium red , chemistry , biophysics , receptor , divalent , inositol , biochemistry , calcium , biology , organic chemistry
In addition to the activation of cAMP‐dependent pathways, odorant binding to its receptor can lead to inositol 1,4,5‐trisphosphate (InsP 3 ) production that may induce the opening of plasma membrane channels. We therefore investigated the presence and nature of such channels in carp olfactory cilia. Functional analysis was performed by reconstitution of the olfactory cilia in planar lipid bilayers (tip‐dip method). In the presence of InsP 3 (10 μ m ) and Ca 2+ (100 n m ), a current of 1.6 ± 0.1 pA (mean ± SEM, n = 4) was measured, using Ba 2+ as charge carrier. The I/V curve displayed a slope conductance of 45 ± 5 pS and a reversal potential of −29 mV indicating a higher selectivity for divalent cations. This current was characterized by two mean open times (3.0 ± 0.4 ms and 42.0 ± 2.6 ms, n = 4) and was strongly inhibited by ruthenium red (30 μ m ) or heparin (10 μg/mL). Importantly, the channel activity was closely dependent on the Ca 2+ concentration, with the highest open probability (P o ) at 100 n m Ca 2+ (P o = 0.50 ± 0.02, n = 4). P o is lower at both higher and lower Ca 2+ concentrations. A structural identification of the channel was attempted by using a large panel of antibodies, raised against several InsP 3 receptor (InsP 3 R)/Ca 2+ release channel isoforms. The type 1 InsP 3 R was detected in carp cerebellum and whole brain, while a lower molecular mass InsP 3 R, which may correspond to type 2 or 3, was detected in heart, whole brain and the soma of the olfactory neurons. None of the antibodies, however, cross‐reacted with olfactory cilia. Taken together, these results indicate that in carp olfactory cilia an InsP 3 ‐dependent channel is present, distinct from the classical InsP 3 Rs localized on intracellular membranes.