Limits...
Mechanism of inhibition of mouse Slo3 (KCa 5.1) potassium channels by quinine, quinidine and barium.

Wrighton DC, Muench SP, Lippiat JD - Br. J. Pharmacol. (2015)

Bottom Line: The F304Y mutation did not alter the effects of barium, but increased the potency of inhibition by both quinine and quinidine approximately 10-fold; this effect was not observed with the R196Q mutation.Barium inhibits mSlo3 outside the cell by interacting with the selectivity filter, whereas quinine and quinidine act from the inside, by binding in a hydrophobic pocket formed by the S6 segment of each subunit.Furthermore, we propose that the Slo3 channel activation gate lies deep within the pore between F304 in the S6 segment and the selectivity filter.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK.

No MeSH data available.


Related in: MedlinePlus

Block of mSlo3 currents by inhibitors of KSper. Oocytes were held at −80 mV and depolarizing pulses to +100 mV were applied. (A) Representative traces with each drug or condition as indicated: black trace, control currents recorded prior to drug application; light grey trace, current in the presence of the inhibitor; dark grey trace, current after washing out the inhibitor for at least 10 min. The dashed line represents the zero-current level and scale bars represent equivalent current amplitudes and timescales. The effects of Ba2+ were measured in both the standard solution containing 2.5 mM K+ (2.5K) and with a high 100 mM K+ solution (100K). (B) Mean percentage inhibition for each drug or condition as indicated (n values indicated in parentheses in the bars).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4556473&req=5

fig02: Block of mSlo3 currents by inhibitors of KSper. Oocytes were held at −80 mV and depolarizing pulses to +100 mV were applied. (A) Representative traces with each drug or condition as indicated: black trace, control currents recorded prior to drug application; light grey trace, current in the presence of the inhibitor; dark grey trace, current after washing out the inhibitor for at least 10 min. The dashed line represents the zero-current level and scale bars represent equivalent current amplitudes and timescales. The effects of Ba2+ were measured in both the standard solution containing 2.5 mM K+ (2.5K) and with a high 100 mM K+ solution (100K). (B) Mean percentage inhibition for each drug or condition as indicated (n values indicated in parentheses in the bars).

Mentions: We next studied the effects of drugs that have previously been shown to inhibit the sperm KSper channel (Navarro et al., 2007) on WT mSlo3 currents. Like Ksper (Navarro et al., 2007), Slo3 was weakly inhibited by 5 μM mibefridil and 20 mM TEA+, but more strongly inhibited by 500 μM quinine and 50 μM clofilium (Figure 2). WT mSlo3 was also strongly inhibited by 2 mM Ba2+, an effect that was prevented by raising the extracellular K+ concentration to 100 mM (Figure 2). The inhibition by each drug was reversible, although we observed that the amplitude of the current after washing out mibefridil was often larger than the control currents.


Mechanism of inhibition of mouse Slo3 (KCa 5.1) potassium channels by quinine, quinidine and barium.

Wrighton DC, Muench SP, Lippiat JD - Br. J. Pharmacol. (2015)

Block of mSlo3 currents by inhibitors of KSper. Oocytes were held at −80 mV and depolarizing pulses to +100 mV were applied. (A) Representative traces with each drug or condition as indicated: black trace, control currents recorded prior to drug application; light grey trace, current in the presence of the inhibitor; dark grey trace, current after washing out the inhibitor for at least 10 min. The dashed line represents the zero-current level and scale bars represent equivalent current amplitudes and timescales. The effects of Ba2+ were measured in both the standard solution containing 2.5 mM K+ (2.5K) and with a high 100 mM K+ solution (100K). (B) Mean percentage inhibition for each drug or condition as indicated (n values indicated in parentheses in the bars).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4556473&req=5

fig02: Block of mSlo3 currents by inhibitors of KSper. Oocytes were held at −80 mV and depolarizing pulses to +100 mV were applied. (A) Representative traces with each drug or condition as indicated: black trace, control currents recorded prior to drug application; light grey trace, current in the presence of the inhibitor; dark grey trace, current after washing out the inhibitor for at least 10 min. The dashed line represents the zero-current level and scale bars represent equivalent current amplitudes and timescales. The effects of Ba2+ were measured in both the standard solution containing 2.5 mM K+ (2.5K) and with a high 100 mM K+ solution (100K). (B) Mean percentage inhibition for each drug or condition as indicated (n values indicated in parentheses in the bars).
Mentions: We next studied the effects of drugs that have previously been shown to inhibit the sperm KSper channel (Navarro et al., 2007) on WT mSlo3 currents. Like Ksper (Navarro et al., 2007), Slo3 was weakly inhibited by 5 μM mibefridil and 20 mM TEA+, but more strongly inhibited by 500 μM quinine and 50 μM clofilium (Figure 2). WT mSlo3 was also strongly inhibited by 2 mM Ba2+, an effect that was prevented by raising the extracellular K+ concentration to 100 mM (Figure 2). The inhibition by each drug was reversible, although we observed that the amplitude of the current after washing out mibefridil was often larger than the control currents.

Bottom Line: The F304Y mutation did not alter the effects of barium, but increased the potency of inhibition by both quinine and quinidine approximately 10-fold; this effect was not observed with the R196Q mutation.Barium inhibits mSlo3 outside the cell by interacting with the selectivity filter, whereas quinine and quinidine act from the inside, by binding in a hydrophobic pocket formed by the S6 segment of each subunit.Furthermore, we propose that the Slo3 channel activation gate lies deep within the pore between F304 in the S6 segment and the selectivity filter.

View Article: PubMed Central - PubMed

Affiliation: School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, UK.

No MeSH data available.


Related in: MedlinePlus