Experimental Modification fo Ion Channels. Transgenic Animal Models

Transcription

1 Experimental Modification fo Ion Channels Transgenic Animal Models

2 Molecular Diversity of Potassium Channels

3 Functional Diversity of potassium channels

4 Inward rectifier K+ channels I K1 Subunits: Kir2.1 (KCNJ2) Kir2.2 (KCNJ12) Kir2.3 (KCNJ4) Kir2.4 (KCNJ14) Function: AP phase 4 resting potential AP Dysfunction: Long QT Syndrome Short QT Syndrome Andersen-Tawil Syndrome Brugada Syndrome I K1

5 Let`sexperiment with I K1 blocker! Test Potential (mv) Curren nt Density (p pa/pf) Can we extract info on the function of Kir2.1 (or Kir2.2, 2.3, 2.4)?

6 Transient outward K+ channels I to : transient outward K + current Pore-forming subunits: Kv1.4 (KCNA4), Kv4.2 (KCND2), Kv4.3 (KCND3) Homo- or heteromeric structure Sensitive to 4-aminopyridine Auxiliary subunits: KChIP2, DPP6, KCNE1-5? Function AP Phase 1 Region-specific AP configurations Dysfunction Brugada Syndrome Idiopathic Ventricular Fibrillation Unclosed files, case no. 1: Subunit composition of I to 50 mv channels -35 mv -80 mv

7 herg Delayed rectifier K+ channels KvLQT Unclosed files case no. 2: Subunit composition of I K Delayed outward rectifiers channels Rapidlyactivating component: I Kr, herg (KCNH2) Slowly activating component: I Ks, KvLQT1 (KCNQ1) Auxiliary subunits: KCNE1 5 Function: AP phase 2 and 3 Dysfunction: long QT Syndrome I Ks I Kr

8 α1c -/+ Transgenic models of disease (knock-out variations) Traditional knock-out α1c α1c +/fl, Cre loxp Cardiac specific KO α1c loxp α1c αmhc Cre α1c +/fl, MerCreMer Cardiac specific, inducible KO loxp α1c loxp α1c αmhc Mer Cre Mer

9 Transgenic models of disease (knock-out variations) loxp α1c loxp α1cfl/fl, Cre Cre loxp αmhc α1c loxp loxp α1c loxp α1c-/fl, Cre αmhc Cre

10 Transgenic models of disease (knock-out variations) Pros Subunit-specific function is well reflected All environmental parameters are present Cons Works for chronic models (there is time for compensatory effects to develop) Tissue or cell-type specific targeting is problematic

11 Heterologous expression systems: Oocyte injection Xenopus laevis cdna in vitro transcription T7 YFG AAAAA crna Amp r microinjection Microinjection of Xenopus eggs crna translation nucleus Cytoplasm oocyte mature protein

12 Role of auxiliary subunits: I Ks channels, an illustrative example The KvLQT1 pore-forming subunit produces no current in the absence of mink. Inject mink RNA into Xenopus oocytes big current. Why? Auxiliary subunits, fields of action: Gating Protein folding, trafficking Ssubcellular localization Sensitivity to blockers Receptor-and/or ligand-dependent effects

13 Heterologous expression systems: Transfection of mammalian cells CMV YFG IRES GFP pa cdna transfection Amp r Neo r CHO cells transfected with GFP cdna transcription mrna nucleus cytoplasm translation mature protein

14 Heterologous expression systems: Transfection of mammalian cells KvLQT1 + mink 50mV -40mV -80mV KvLQT1 + MiRP2 50mV -40mV -80mV

15 Heterologous expression systems: Transfection of mammalian cells Pros Subunit-specific function is absolutely reflected Subunit interactions can be assessed Easy to carry out Cons No environmental parameters are present (ionic, receptorial, metabolic, protein, lipid environment)

16 Viral gene transfer Lentivirus-based vector Fibroblast Cardiomyocyte Adenovirus-based vector Cardiomyocyte Pukinje cells A A

17 Over-expression of dominant negative mutant subunits G Y G A A A WT DN

18 Role of I Kir inil-1βproduction in macrophages

19 The RNAipathway

20 Artificial micrornas

21 DPP6: an auxiliary subunit of I to channels in Purkinje cells AV-GFP-DPP6 mrna protein DPP6 overexpression P DPP6 IRES GFP pa VM PC

22 DPP6: an auxiliary subunit of I to channels in Purkinje cells AdV-DPP6-KD DPP6 gene silencing CMV GFP Ω pa VM PC

23 Manipulating microrna expression in vitro LV-mir29b sponge CMV GFP mir29b UUGUGACUAAA sponge target site 5`...AACACTGATTT G UU U ACCACGAU 5` C T G TGGTGCTA... LV-mir29b-OE CMV GFP hsa-pri-mir29b mir-29b knock-down in vitro Relative Expression (a. u.) ** ** * * GFP Control mir29b sponge Relative Expression (a. u.) mir29b over-expression in vitro ** 10 9 SCR control mir29b over-expressing *** *** 10***

24 Manipulating microrna expression in vivo Adeno-associated virus, serotype 9 AAV-sp29b ITR EF1α` intron `EF1α GFP T T T pa ITR AAV9

25 Viral gene delivery Vector classes Lentivirus In vitro applications For proliferating target cells Establishment of stable cell lines Produced with ease Adenovirus In vitroandin vivo( atiral painting ) broad host range transient transduction Tedious production Adeno-associated virus(aav9) Cardiac gene transfer in vivo Produced with ease Only for light payload Applications Protein overexpression wild type(dpp6) mutant(kir2.1-dn) Gene silencing RNA interference MicroRNA manipulations microrna sponge microrna overexpression

26 Molecular biology of lentiviral vectors TG: Kir2.1-DN Kir2.1-WT

27 Molecular biology of adenoviral vectors YFG AV shuttle left arm right arm left arm right arm AV backbone E1-E left arm YFG complete AV genome E1-E3 3. right arm 2.