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Voltage-Gated K+ Channels
MK Mathew NCBS, TIFR UAS – GKVK Campus Bangalore IBRO Course in Neuroscience Center for Cognitive Neuroscience & Semantics, University of Latvia Riga, Latvia August 21-August 29, 2013
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PROPERTIES OF VOLTAGE-GATED ION CHANNELS
Voltage sensitive Requires voltage-sensing apparatus Requires transduction machinery High Throughput: 108 ions/second Protein supports an aqueous column traversing the membrane Discriminates between Na+ and K+ Requires a selectivity filter
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1982 Noda … Numa Nature AChR a-subunit cloned from peptide information
1983 Noda … Numa Nature All AChR subunits cloned 1984 Noda … Numa Nature Na channel a-subunit cloned 1987 Stuhmer .. Numa Eur J Biophys Xenopus expression Na channel 1989 Stuhmer Conti .. Numa Nature S4 mutations in Na channel
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Sodium Channel
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1982 Noda … Numa Nature AChR a-subunit cloned from peptide information
1983 Noda … Numa Nature All AChR subunits cloned 1984 Noda … Numa Nature Na channel a-subunit cloned 1987 Stuhmer .. Numa Eur J Biophys Xenopus expression Na channel 1989 Stuhmer Conti .. Numa Nature S4 mutations in Na channel 1987 Kamb Iverson Tanouye Cell 1987 Papazian … Jan Science Shaker Cloning !988 Pongs … Ferrus EMBO J
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Xenopus oocytes Two Electrode Voltage clamp
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ELECTROPHYSIOLOGICAL PROPERTIES OF HUMAN K+ CHANNELS
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hKv1.4
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KcsA Doyle et al., Science 1998; 280: 69
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Doyle et al., Science 1998; 280: 69 Jiang et al., Nature ; 523
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Gary Yellen
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KcsA Doyle et al., Science 1998; 280: 69
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Zhou .. MacKinnon (01) Nature
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Varma & Rempe (2007) Biophys J 93:1093–1099
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Zhou .. MacKinnon (01) Nature
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Payandeh .. Catterall (2011) Nature
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I II III IV selctivity Ca E Ca/Na~ 3000 Na D K A Na/Ca ~ 1000 Ca start
RajGanesh et al (2000) Proteins
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KcsA Doyle et al., Science 1998; 280: 69
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Kv 1.2 Crystal Structure MacKinnon ,2005
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… Catterall (2006) PNAS
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Pathak .. Isacoff (2007) Neuron
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Sequence Alignment of The S4-S5 Region
Ken (1991) PNAS
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Mutant V1/2 (mV) Wt 1±5 V1 100±6 V2 69±7 V3 -5±2 V4 -22±3 V5 -7±7
L1 L2 L3 L4 L5 Mutant V1/2 (mV) Wt 1±5 V1 100±6 V2 69±7 V3 -5±2 V4 -22±3 V5 -7±7 V2A3 32±5 V1/2 Val/Ala mutations in Shaker Phenylalanine mutations in hKv 1.4 McCormack et al., (1991) Judge et al., (2002) McCormack et al (91) PNAS
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Bezanilla (2000) Physiol Rev 80, 555 - 592
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Gating charge Sensor Movement Po Schoppa Sigworth (98) JGP
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Kv 1.2 Crystal Structure MacKinnon ,2005
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L312M-L326V DV1/2 = 0 mV V406L–L312M DV1/2 = -42 mV A305L-L312M DV1/2 = +18 mV Sanjeev
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Sanjeev, Nagarajan J Physiol
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OPEN STATE Sanjeev, Nagarajan
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CLOSED STATE
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CLOSED OPEN Sanjeev, Nagarajan J Physiol
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Gating charge Po Ledwell Aldrich (99) JGP
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Gating charge Po Ledwell Aldrich (99) JGP
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ACTIVATED STATE
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CLOSED ACTIVATED OPEN
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Sanjeev, Nagarajan J Physiol
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Kaczmarek Nature Reviews Neuroscience 7, 761–771 (October 2006) | doi:10.1038/nrn1988
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KCNRG : K (Potassium) / CN (Channel) / RG (Regulator)
+ T1 S S S S S5 p S6 Ball KCNRG (monomer)n ? D.V. Ivanov et al./FEBS Letters 539 (2003)
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Surface Expression Analysis
5um KCNRG reduces Surface targeting of hKv 1.4 Hyder (2010)
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KS Krishnan 1976
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YD Ramu Baron Chanda Anurag Varshney Kavitha S Sanjeev Upadhyay
S Nagarajan Hyder Usman 5um Ken McCormack
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