LearnPick Navigation
Close

Ion Channels

Published in: Biology | Physiology | Science
102 views
  • Sourajit M

    • Bangalore
    • 3 Years of Experience
    • Qualification: Ph.D
    • Teaches: Zoology, Physics, Chemistry, Biology, Bengali, Phy...
  • Contact this tutor

This PPT contains description in brief about potassium ion channel of two-pore domain type.

  • 1
    Much more than a leak : revisiting different aspects of K2P channels + Brief history about K2P channels + Do K2P channels : display voltage-dependent gating ??? contribute to action potential generation ??? + Functional role of Alternative Splicing and Alternative Translation Initiation
  • 2
    Characteristics of Κ2Ρ channels Pore domains Extracellular Phylogeny of Κ2Ρ channels Σ Σ lntracellular c (Enyedi & 2010) Assemble ας dimers Two pore forming loops Four transmembrane helices + Distribution: CNS, Heart, Blood vessels, Kidney & others τνιικ TREK TASK ΤΑΙΚ : TRESK ΜΙΚ-Ι 37% ΚΟΝΚ-7 kCNk7, ΤΙΝΙΚ-2 kCNk6, kCNk12, κ.ρΡ12Ι ΤΗΙΚ.2 ΤΗΙΚ.1 ΚΟΝΚ13, kCNk4, Κ 2ρ4.1 TRAAK - KCNK2, ΤΑΕΚ-Ι TREk-2 kCNK10, Κ2Ρ10.1 kCNk3. TASK-1 54% TASK.3 kCNk15, Κ2Ρ15Μ KCNK17, Κ ΤΑΙ-Κ-2 (TASK-4) TASk.2 kCNk5, ΤΑΙΚ.Ι ΚΟΝΚ16, kCNk18k ιθ Ι TRESK•1 Weak inward rectification lnhibited by halothane Lipid, temperature and stretch activated lnhibited by extracellular protons φκ -65-75) lnhibjted by extracellular protons Calc;um activated (Bayliss and Barrett, 2008)
  • 3
    History of the eukaryotic K2P channels' clades
  • 4
    J. GEN. PHYSIOLw @ ne R(kkefeller University Volume 100 December 1992 1021-1040 A Mechanosensitive K + Channel in Heart Cells Activation DONCHEE KIM Acid From the Dqartment of Physiology and Bophysics, Chicago Medical Schq»li Nonh Chicago, Ilinois 60064 (mmHg) + 60 + 20 ill i (2.2) (3.7) 96 (14.8) (22.1) 100 ms 1.0 10 Pressure (mmHg)
  • 5
    A TEA-Insensitive Flickering Potassium Channel Active around the Resting Potential in Myelinated Nerve J. Membrane Biol. 130, 149-162 (1992 Duk-Su Koh, Peter Jonast, Michael E. Bräu, and Werner Vogel TEA Ba + TEA control control C; + TEA 200 ms 2 s B Fig. 1. Typical activity of the flicker channel at different time scales and different resolutions. Outside-out patch. Bath: 105 mM-Ko, pipette: 105 mM-Ki. Membrane potential Em 90 m V, filter frequency: 1 kHz (A, B) and 10 kHz (C). -90 mV TEA Ba + TEA control -60 mV 10 PA 20 s + TEA control
  • 6
    mammalian two pore domain mechano-gated -like K channel The No.15 pp.4283-4290, 0.5 TREK-I ' Amanda J.Patel, Eric Honoré. Franeois Maingret. Florian Lesage, Michel Fink. Fabrice Duprat and Michel Lazdunskil I / I max 2.4 1.2 -50 -1.2 CHCI 3 control 50 100 o -40 -80 P (mm Hg) Stretch genera anes e IC I (nA) control 1 0.8 0.6 0.4 -100 -50 2 1 -100 -50 -2 IOpMAA control 50 100 V (mV) CPZ (W M) 2 min cAMp + AA cAMP 50 100 0.1 1 CHCI 3 V (mV) cAMP addition 10 mM AA Cationic Amphipaths
  • 7
    Are K2P channels leak channels...??? K2P channels are described as : + 'Leak Channels' + 'Background Channels' + 'Open Rectifier Channels' (Goldstein et al., 2001) (Honoré, 2007) (Goldstein et al., 2001) Outward rectification in TASK channels What is an 'ion-selective leak channel' ? Assumptions of crystal-field theory + Linear voltage gradient + Independent movement of ions across membranes Current-Voltage relationship of K + channels: + Strong outward rectification in physiological conditions + Linear in symmetrical K + concentrations -150 5K 22K 55K 05K 55K 2 50 -2 -4 (Duprat et al., 1997)
  • 8
    Surprisingly... !!! Properties incompatible with the concept of 'open rectifier' or 'K + selective holes' p 2 mTASK-l 1 mTBAK-l -IOO -50 -2 NPo 0.2 0.1 50 IOOmV -80 -40 0 40 80 Inward rectification with symmetrical K + gradient Increase in open probability with depolarisation (Kim et al., 1999)
  • 9
    Do K2P channels show time-dependent gating ??? 1.0 c 0.4 02 0.0 : 20 ms TREK-I a t -19 ms decay t 210 ms decay + K2P channels are not permanently open + Open probability increases with depolarisation + Time-dependent gating is observed Upon depolarisation, an instantaneous component followed by a time- dependant component Upon repolarisation, pronounced deactivation tail is observed Is regulatory K + channel a better nomenclature for K2P channels?
  • 10
    TASK-3 KO urrent injetion 20 PA o eo frequency unnn 20 rnV 200 ms Wild-type n = 16 In s aping action potentla pattern an 24 PA 28 PA 1.0 0.3 0.6 0.4 on O 32 PA 36 PA n = 10 44 PA 48 PA 3 120 100 60 TASK-3 KO 0 4 8 12 '16 m 24 28 32 40 44 48 Current injection (PA) 4 8 12 16 20 24 28 32 36 40 Current injection above threshold (PA) (Brickley et al., 2007)
  • 11
    Regulation of the number of K2P channels on the cell surface Alternative splicing Enn I DNA Eiff I RNA 2 3 mRNA Translation Protein A Exon 2 Exon 2 Exon 3 Exon 3 Alternative Splicing 1 2 Translation Protein B Exon4 E*tn4 Exon 5 5 3 2 Translation Protein C Alternative Translation Initiation (Wikipedia) ORF of K2P channels is encoded by 2-7 exons TASK-I : 2 exons, TREK clade: 7 exons Conserved splice site: G Y/ / G Differential expression of N-terminal splice in various tissues - significance?
  • 12
    Pflu eßArch-EurJPh siol 2014 466:1559-1570 (Rinné S et al., 2014) A splice variant of the two-pore domain potassium channel TREK-I with only one pore domain reduces the surface expression of full-length TREK-I channels rTUK-1 Exon 5 Exon 6 ..CTGACCACCATTGGATTTGGCGATTATGTGGCAGqgagg..gc4TGGGICGGAC11 . tTUK-1e Exon 4 G SDI. Exon 6 ..1AAGÆTTGCCIAAGTÆGGACICATTTATTgggag..gc41GGGTCGGACA. hNK-1 hTREK-1e Exon 5 Exon 4 Exon 6 G SDI. Exon 6 V DPI TREK-I a-d TREK-Ie 0-8 0.6 0.4 0-2 0.0 . .AAAGGAATTGCCæGTGGAAGATACGTTTATTÉgag. KGIAKVEDTFI
  • 13
    Dominant Negative Effects of a Non-conducting TREK 1 Splice Variant Expressed in Brain Received for publication, January 29, 2010, and in revised form, June 29, 2010 Published, JBC Papers in Press, July 6, 2010, DOI 10.1074/Jbc.M11 0.108423 Emma L. Veale , Kathryn A. Rees*, Alistair Mathie*l, and Stefan Trapp 61 81 101 121 141 161 81 ACAGTCTCCACGATTTTCCTGGTGGTCGTCCTCTACCTGATCATCGGAGCCACGGTGTTC AAGGCATTGGAGCAGCCTCAGGAGATTTCCCAGAGGACCACCATTGTGATCCAGAAGCAG ACCT TCATAGCCCAGCATGCCT TAGTGGCÄGCAATAAÄCGCAGGGATTATCCCCTTÄGGAÄÄCAGCTCCAATCAAGTTAG CTGGGÄCCTCGGAAGCTCTTTCTT 'TTTGCTGGTACTGTTATCACAÄCCÄTÄ GATTT GGPAACATCTCCCCACGAACTGAAGGTGGAAAAÄTÄTTCTGCÄTCATCTATGCCTTGCTG GGAATTCCCCTCTTTGGCTTTCTACTGGCTGGGGTTGGTGATCAGCTAGGAACTATATTT 114 bp Frame shifted 'e Sequence • NH2 TREKIAEx4 stop 50 76 40 30 20 10 14 65 85 IOS 125 143 NH2 165 17 23 1:1 20 1.5 0.5 Exon 4 COOH TREKI TREKI + TREKlAEx4 TREKlAEx4 -100 -80 -60 Voltage (mV) -40 -20 DLETSHHAQKAAKYSVSSMPYWEFPSLVFSWLELEIS
  • 14
    Alternative Translation Initiation TREK-I + 2 translation initiation sites + 2 isoforms are functional - long and short forms + Splice variant lacking exon 4 had dominant negetive effect on long isoform Significance of ATI Reported single-channel conductance in heterologous system: 95 - 130 PS (Han J et al., 2003) TREK-2 3 translation initiation sites Long isoform's conductance- 52ps Short isoform's conductance- -200 ps - 80 2 different conductance states ! 40 PS and 130 PS were reported in Native rat cardiomyocytes and heterologous system (Li XT et al., 2006)

Discussion

Copyright Infringement: All the contents displayed here are being uploaded by our members. If an user uploaded your copyrighted material to LearnPick without your permission, please submit a Takedown Request for removal.

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related PPTs

Query submitted.

Thank you!

Drop Us a Query:

Drop Us a Query