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SLO-2 potassium channel is an important regulator of neurotransmitter release in Caenorhabditis elegans.

Liu P, Chen B, Wang ZW - Nat Commun (2014)

Bottom Line: Loss-of-function mutation of slo-2 increases the duration and charge transfer rate of spontaneous postsynaptic current bursts at the neuromuscular junction, which are physiological signals used by motor neurons to control muscle cells, without altering postsynaptic receptor sensitivity.SLO-2 activity in motor neurons depends on Ca(2+) entry through EGL-19, an L-type voltage-gated Ca(2+) channel (CaV1), but not on other proteins implicated in either Ca(2+) entry or intracellular Ca(2+) release.Thus, SLO-2 is functionally coupled with CaV1 and regulates neurotransmitter release.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.

ABSTRACT
Slo2 channels are prominent K(+) channels in mammalian neurons but their physiological functions are not well understood. Here we investigate physiological functions and regulation of the Caenorhabditis elegans homologue SLO-2 in motor neurons through electrophysiological analyses of wild-type and mutant worms. We find that SLO-2 is the primary K(+) channel conducting delayed outward current in cholinergic motor neurons, and one of two K(+) channels with this function in GABAergic motor neurons. Loss-of-function mutation of slo-2 increases the duration and charge transfer rate of spontaneous postsynaptic current bursts at the neuromuscular junction, which are physiological signals used by motor neurons to control muscle cells, without altering postsynaptic receptor sensitivity. SLO-2 activity in motor neurons depends on Ca(2+) entry through EGL-19, an L-type voltage-gated Ca(2+) channel (CaV1), but not on other proteins implicated in either Ca(2+) entry or intracellular Ca(2+) release. Thus, SLO-2 is functionally coupled with CaV1 and regulates neurotransmitter release.

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SLO-2 is an important contributor to delayed outward current in cholinergic and GABAergicmotor neurons. A. Diagram showing the locations of the recorded motor neuronsVD5, VA5 and VB6 (based on published anatomical data63). B. Sample whole-cell current traces in response tovoltage steps (−60 to +70 mV at 10-mV intervals) from a holding voltage of−60 mV (left) and current-voltage relationships(right) from VA5, VB6 and VD5 of wild type (WT),slo-2(nf101), slo-2 rescue, shk-1(ok1581),slo-2(nf101);shk-1(ok1581), shl-1(ok1168), andslo-1(md1745). In VA5 and VB6, delayed outward current was greatlydecreased in slo-2(nf101) compared with WT but not further decreased inthe slo-2;shk-1 double mutant. In VD5, delayed outward current wasgreatly decreased in both slo-2(nf101) andshk-1(ok1581), and was essentially absent in theslo-2;shk-1 double mutant. Data are shown as mean ± SE. Theasterisk (*) indicates a significant difference compared with WT whereas the poundsign (#) indicates a significant difference compared with the single mutants ofslo-2 and shk-1 (p < 0.01, two-waymixed model ANOVA with Tukey’s post hoc tests). The recordingswere performed with extracellular solution I and pipette solution I.
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Figure 1: SLO-2 is an important contributor to delayed outward current in cholinergic and GABAergicmotor neurons. A. Diagram showing the locations of the recorded motor neuronsVD5, VA5 and VB6 (based on published anatomical data63). B. Sample whole-cell current traces in response tovoltage steps (−60 to +70 mV at 10-mV intervals) from a holding voltage of−60 mV (left) and current-voltage relationships(right) from VA5, VB6 and VD5 of wild type (WT),slo-2(nf101), slo-2 rescue, shk-1(ok1581),slo-2(nf101);shk-1(ok1581), shl-1(ok1168), andslo-1(md1745). In VA5 and VB6, delayed outward current was greatlydecreased in slo-2(nf101) compared with WT but not further decreased inthe slo-2;shk-1 double mutant. In VD5, delayed outward current wasgreatly decreased in both slo-2(nf101) andshk-1(ok1581), and was essentially absent in theslo-2;shk-1 double mutant. Data are shown as mean ± SE. Theasterisk (*) indicates a significant difference compared with WT whereas the poundsign (#) indicates a significant difference compared with the single mutants ofslo-2 and shk-1 (p < 0.01, two-waymixed model ANOVA with Tukey’s post hoc tests). The recordingswere performed with extracellular solution I and pipette solution I.

Mentions: Motor neurons controlling C. elegans body-wall muscle includethree major classes: A, B and D. The A and B classes mediate backward and forwardmovements, respectively, and contract muscle by releasing acetylcholine (ACh), whereas theD class relaxes muscle by releasing GABA28,29. To investigate physiological roles ofSLO-2 in motor neurons, we chose VA5, VB6 and VD5 (the letter “V” standsfor ventral) as representatives of the three classes of motor neuronsbecause these ventral muscle-innervating neurons could be easily identified based on theiranatomical locations (Figure 1A). We first examinedthe effect of slo-2 mutation on delayed outward current in response tovoltage steps (−60 to +70 mV at 10-mV intervals). The amplitude of delayedoutward current was greatly decreased in slo-2(nf101), a putative resulting from a deletion30, comparedwith wild type in all the motor neurons (Figure 1B).The decrease was more severe in VA5 and VB6 than VD5. Compared with wild type, delayedoutward current at +70 mV decreased by 80% in VA5 (168.9 ± 16.6versus 33.6 ± 2.4 pA/pF), 67% in VB6 (176.1 ± 13.4 versus 58.1± 3.1 pA/pF), and 33% in VD5 (197.1 ± 12.5 versus 131.9 ±5.6 pA/pF) (Figure 1B). The deficiency of delayedoutward current in the mutant was rescued by expressing a SLO-2::GFP fusion protein, inwhich GFP coding sequence was fused in-frame to the 3′-end ofslo-2b (F08B12.3b) cDNA (www.wormbase.org)23, under the control of the pan-neuronalrab-3 promoter (Prab-3)31, 32 (Figure 1B), suggesting that the deficiency resulted fromslo-2 mutation in neurons, and that the SLO-2::GFP fusion protein wasfunctional.


SLO-2 potassium channel is an important regulator of neurotransmitter release in Caenorhabditis elegans.

Liu P, Chen B, Wang ZW - Nat Commun (2014)

SLO-2 is an important contributor to delayed outward current in cholinergic and GABAergicmotor neurons. A. Diagram showing the locations of the recorded motor neuronsVD5, VA5 and VB6 (based on published anatomical data63). B. Sample whole-cell current traces in response tovoltage steps (−60 to +70 mV at 10-mV intervals) from a holding voltage of−60 mV (left) and current-voltage relationships(right) from VA5, VB6 and VD5 of wild type (WT),slo-2(nf101), slo-2 rescue, shk-1(ok1581),slo-2(nf101);shk-1(ok1581), shl-1(ok1168), andslo-1(md1745). In VA5 and VB6, delayed outward current was greatlydecreased in slo-2(nf101) compared with WT but not further decreased inthe slo-2;shk-1 double mutant. In VD5, delayed outward current wasgreatly decreased in both slo-2(nf101) andshk-1(ok1581), and was essentially absent in theslo-2;shk-1 double mutant. Data are shown as mean ± SE. Theasterisk (*) indicates a significant difference compared with WT whereas the poundsign (#) indicates a significant difference compared with the single mutants ofslo-2 and shk-1 (p < 0.01, two-waymixed model ANOVA with Tukey’s post hoc tests). The recordingswere performed with extracellular solution I and pipette solution I.
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Figure 1: SLO-2 is an important contributor to delayed outward current in cholinergic and GABAergicmotor neurons. A. Diagram showing the locations of the recorded motor neuronsVD5, VA5 and VB6 (based on published anatomical data63). B. Sample whole-cell current traces in response tovoltage steps (−60 to +70 mV at 10-mV intervals) from a holding voltage of−60 mV (left) and current-voltage relationships(right) from VA5, VB6 and VD5 of wild type (WT),slo-2(nf101), slo-2 rescue, shk-1(ok1581),slo-2(nf101);shk-1(ok1581), shl-1(ok1168), andslo-1(md1745). In VA5 and VB6, delayed outward current was greatlydecreased in slo-2(nf101) compared with WT but not further decreased inthe slo-2;shk-1 double mutant. In VD5, delayed outward current wasgreatly decreased in both slo-2(nf101) andshk-1(ok1581), and was essentially absent in theslo-2;shk-1 double mutant. Data are shown as mean ± SE. Theasterisk (*) indicates a significant difference compared with WT whereas the poundsign (#) indicates a significant difference compared with the single mutants ofslo-2 and shk-1 (p < 0.01, two-waymixed model ANOVA with Tukey’s post hoc tests). The recordingswere performed with extracellular solution I and pipette solution I.
Mentions: Motor neurons controlling C. elegans body-wall muscle includethree major classes: A, B and D. The A and B classes mediate backward and forwardmovements, respectively, and contract muscle by releasing acetylcholine (ACh), whereas theD class relaxes muscle by releasing GABA28,29. To investigate physiological roles ofSLO-2 in motor neurons, we chose VA5, VB6 and VD5 (the letter “V” standsfor ventral) as representatives of the three classes of motor neuronsbecause these ventral muscle-innervating neurons could be easily identified based on theiranatomical locations (Figure 1A). We first examinedthe effect of slo-2 mutation on delayed outward current in response tovoltage steps (−60 to +70 mV at 10-mV intervals). The amplitude of delayedoutward current was greatly decreased in slo-2(nf101), a putative resulting from a deletion30, comparedwith wild type in all the motor neurons (Figure 1B).The decrease was more severe in VA5 and VB6 than VD5. Compared with wild type, delayedoutward current at +70 mV decreased by 80% in VA5 (168.9 ± 16.6versus 33.6 ± 2.4 pA/pF), 67% in VB6 (176.1 ± 13.4 versus 58.1± 3.1 pA/pF), and 33% in VD5 (197.1 ± 12.5 versus 131.9 ±5.6 pA/pF) (Figure 1B). The deficiency of delayedoutward current in the mutant was rescued by expressing a SLO-2::GFP fusion protein, inwhich GFP coding sequence was fused in-frame to the 3′-end ofslo-2b (F08B12.3b) cDNA (www.wormbase.org)23, under the control of the pan-neuronalrab-3 promoter (Prab-3)31, 32 (Figure 1B), suggesting that the deficiency resulted fromslo-2 mutation in neurons, and that the SLO-2::GFP fusion protein wasfunctional.

Bottom Line: Loss-of-function mutation of slo-2 increases the duration and charge transfer rate of spontaneous postsynaptic current bursts at the neuromuscular junction, which are physiological signals used by motor neurons to control muscle cells, without altering postsynaptic receptor sensitivity.SLO-2 activity in motor neurons depends on Ca(2+) entry through EGL-19, an L-type voltage-gated Ca(2+) channel (CaV1), but not on other proteins implicated in either Ca(2+) entry or intracellular Ca(2+) release.Thus, SLO-2 is functionally coupled with CaV1 and regulates neurotransmitter release.

View Article: PubMed Central - PubMed

Affiliation: Department of Neuroscience, University of Connecticut Health Center, Farmington, Connecticut 06030, USA.

ABSTRACT
Slo2 channels are prominent K(+) channels in mammalian neurons but their physiological functions are not well understood. Here we investigate physiological functions and regulation of the Caenorhabditis elegans homologue SLO-2 in motor neurons through electrophysiological analyses of wild-type and mutant worms. We find that SLO-2 is the primary K(+) channel conducting delayed outward current in cholinergic motor neurons, and one of two K(+) channels with this function in GABAergic motor neurons. Loss-of-function mutation of slo-2 increases the duration and charge transfer rate of spontaneous postsynaptic current bursts at the neuromuscular junction, which are physiological signals used by motor neurons to control muscle cells, without altering postsynaptic receptor sensitivity. SLO-2 activity in motor neurons depends on Ca(2+) entry through EGL-19, an L-type voltage-gated Ca(2+) channel (CaV1), but not on other proteins implicated in either Ca(2+) entry or intracellular Ca(2+) release. Thus, SLO-2 is functionally coupled with CaV1 and regulates neurotransmitter release.

Show MeSH