The Shaker-like potassium channels of the mouse rod bipolar cell and their contributions to the membrane current

Abstract

RT PCR on mRNA from enzymatically dissociated, isolated bipolar cells showed that these neurons express the Shaker-like K+ channels Kv1.1, Kv1.2, and Kv1.3. Immunohistochemical localization showed each channel to have a unique subcellular distribution: Kv1.1 immunoreactivity was detected in the dendrites and axons terminal, whereas Kv1.2 and Kv1.3 subunits were localized to the axon and the postsynaptic membrane of the rod ribbon synapse, respectively. Whole-cell patch-clamp recordings indicated that the activation voltage of the delayed rectifier current of the isolated bipolar cell and the inhibitory constants for current blockade by TEA, 4-AP, and Ba2+ were similar to these same properties measured for Kv1.1 expressed in oocytes. However, the TEA and 4-AP inhibitory constants for the bipolar cell current differed from the inhibitory constants for Kv1.2 or Kv1.3. These results suggest that the current of the isolated rod bipolar cell is most similar to Kv1.1 but that all three channels may function in the intact retina to allow complex modulation of retinal synaptic signals.

Progesterone Potentiates IP₃-Mediated Calcium Signaling Through Akt/PKB

“…Therefore, the present study utilized this model system for the analysis of IP 3 R-driven Ca 2+ signaling and confirmed the maintenance of sub-cellular protein distributions related to this pathway [8,[10][11][12][13]57]. Previous reports that describe the presence of progesterone receptors [57] as well as genomic steroid hormone receptor activity in the retina [80] corroborate our results of progesterone receptor immunoreactivity and function in the present paper. Kobrinsky and colleagues had shown that reduced levels of IP 3 R protein decrease progesterone-mediated cellular activity in a model system of oocyte maturation [81].…”

“…As reported previously, acute enzymatic and mechanical isolation of rod bipolar cells does not affect cellular morphology and key physiological functional properties [13,[56][57][58][59][60][61]. Therefore, the present study utilized this model system for the analysis of IP 3 R-driven Ca 2+ signaling and confirmed the maintenance of sub-cellular protein distributions related to this pathway [8,[10][11][12][13]57].…”

“…Morphology and immunoreactivity of the dissociated cells were used for identification [13,54,55]. Previous reports had shown that both subcellular morphology and functions are maintained in these acutely, dissociated isolated rod bipolar cells [13,[56][57][58][59][60][61]. We had shown previously for this cellular preparation that substructural distribution of key signaling proteins is also preserved after mechanical and enzymatic dissociation of rod bipolar cells and that redistribution of proteins does not occur during or after dissociation [13].…”

Association of Kv1.5 and Kv1.3 Contributes to the Major Voltage-dependent K+ Channel in Macrophages

“…Tissue localization and the absence of currents other than those generated by homomeric channels argue against certain Kv complexes (30 -32). Thus, the assembly of Kv1.3 with Kv1.1 and Kv1.2 was questioned by immunohistochemical localization in mouse rod bipolar cells (30). In addition, a differential distribution also argues against a heteropolymer between Kv1.1 and Kv1.5 in Schwann cells (31).…”

Differential distribution ofShaker-like andShab-like K+-channel subunits in goldfish retina and retinal bipolar cells

“…Such K ϩ channels are very sensitive to 4-aminopyridine (4AP) and tetraethylammonium (Stü hmer et al, 1989). Calcium-insensitive, delayed rectifiers (I K [V] ) appear to be a general feature of vertebrate retinas, because they have been recorded from a wide variety of retinal neurons, including rod and cone photoreceptors (Attwell and Wilson, 1980;Bader et al, 1982;Barnes and Hille, 1989;Maricq and Korenbrot, 1990), horizontal cells (Tachibana, 1981), bipolar cells (Attwell et al, 1987;Kaneko et al, 1989;Karschin and Wä ssle, 1990;Klumpp et al, 1995a), and ganglion cells (Lipton and Tauck, 1987). ICC localization of ''delayedrectifier'' subunits indicates good general correspondence with the electrophysiological data obtained from rat and mouse retinas (Karschin and Wä ssle, 1990;Hwang et al, 1993;Klumpp et al, 1995a,b).…”