Intracellular traffic of potassium channels

Prof. Dr. Dr. Jürgen Daut

Institut für Physiologie und Pathophysiologie
Philipps Universität Marburg
Deutschhausstr. 2
35037 Marburg
Homepage: http://www.uni-marburg.de/fb20/physiologie/ags/daut/

Project description

Our group at the Institute of Physiology and Pathophysiology of Marburg University is studying the function and the regulation of potassium channels in different cell types and is trying to identify pathophysiologically relevant alterations in ion channel activity. Many inherited diseases are caused by loss-of-function mutations of ion channels (channelopathies). Many of these loss-of-function mutations impair the trafficking of the channels to the surface membrane. Other Our aim is to clarify the mechanisms underlying the assembly and the trafficking of the potassium channels, and we aim to investigate the following steps in detail:

1. The molecular mechanisms of assembly in the endoplasmic reticulum; in particular, we are looking for signal sequences in the cytosolic tails of the channel proteins that govern homomeric or heteromeric assembly immediately after (or coincident with) translation.
2. The mechanisms governing the export of the channel proteins from the ER at specialised ER export sites; in particular, we are interested in identifying novel forward trafficking signals and retention signals and their interaction with accessory proteins.
   
3. The transport between ER and the cis-Golgi complex; the understanding of these processes requires a molecular analysis of the interaction between coat proteins (COP-I and COP-II), recognition sites at the cytosolic loops of the channel proteins and motor proteins that mediate transport along microtubules.

The aims of our work can be summarised as follows:

1. Our working hypothesis is that the posttranslational regulation of the trafficking of ion channels to the surface membrane (and the internalisation of membrane-localised ion channels) is functionally important for learning and memory in neurons and for the modulation of cellular function in many other cell types. We will try to provide experimental evidence for this, both in native cells and in heterologous expression systems.
   
2. We think that ion channels can serve as prototypes for advancing our understanding of mechanisms of intracellular transport of membrane proteins. The main reason for this assumption is that the functional expression of ion channels can be measured directly, which allows discrimination between alterations in channel function (changes in the biophysical properties of the channels) and alterations in channel trafficking (changes in the extent of surface localisation). This facilitates the interpretation of mutational analysis of signal sequences and of s tudies of subcellular localisation.
3. We hope that we can analyse clinically relevant mutations of channel proteins that disturb the correct folding and the trafficking of proteins, and that we can try out new approaches for recruiting these 'intracellular-transport-deficient' channels to the surface membrane, for example by using 'pharmacological chaperones'.
   

Staff

Dr. Regina Preisig-Müller, postdoc
Dr. Vijay Renigunta, postdoc
Marylou Zuzarte, technician
Dr. Günter Schlichthörl, technician
Andrea Schubert, technician

Selected publications since 2007:

1.    Gao YD, Hanley PJ, Rinné S, Zuzarte M, Daut J. Calcium-activated K(+) channel (K(Ca)3.1) activity during Ca(2+) store depletion and store-operated Ca(2+) entry in human macrophages. Cell Calcium. 2010 Jul;48(1):19-27. Epub 2010 Jul 14.

2.    Decher N, Streit AK, Rapedius M, Netter MF, Marzian S, Ehling P, Schlichthörl G, Craan T, Renigunta V, Köhler A, Dodel RC, Navarro-Polanco RA, Preisig-Müller R, Klebe G, Budde T, Baukrowitz T, Daut J. RNA editing modulates the binding of drugs and highly unsaturated fatty acids to the open pore of Kv potassium channels. EMBO J. 2010 Jul 7;29(13):2101-13.

3.    Li XT, Rapedius M, Baukrowitz T, Liu GX, Srivastava DK, Daut J & Hanley PJ (2010). 5-Hydoxydecanoate and coenzyme A are inhibitors of native sarcolemmal KATP channels in inside-out patches. Biochim Biophys Acta. 1800 (2010)385-391.

4.    Zuzarte M, Heusser K, Renigunta V, Schlichthörl G, Rinne S, Wischmeyer E, Daut J, Schwappach B & Preisig-Müller R (2009). Intracellular traffic of the K+ channels TASK-1 and TASK-3: Role of N- and C-terminal sorting signals and interaction with 14-3-3 proteins. Journal of Physiology 587, 929-952

5.    Mederos y Schnitzler M, Rinne S, Skrobek L, Renigunta V, Schlichthörl G, Derst C, Gudermann T, Daut J & Preisig-Müller R (2009). Mutation of histidine-105 in the T1 domain of the potassium channel Kv2.1 disrupts heteromerization with Kv6.3 and Kv6.4. Journal of Biological Chemistry 283, 4695-4704.

6.    Decher N, Gonzalez T, Streit AK, Sachse FB, Renigunta V, Soom M, Heinemann SH, Daut J & Sanguinetti MC (2008). Structural determinants of Kvbeta1.3-induced channel inactivation: a hairpin modulated by PIP2. EMBO Journal 27, 3164-3174.

7.    Decher N, Renigunta V, Zuzarte M, Soom M, Heinmann SH, Timothy K, Keating MT, Daut J, Sanguinetti MC & Splawski I (2007). Impaired interaction between the slide helix and the C-terminus of Kir2.1: a novel mechanism of Andersen syndrome. Cardiovascular Research 75, 748-757.

8.    Zuzarte M, Rinné S, Schlichthörl G, Schubert A, Daut J & Preisig-Müller R (2007). A di-acidic sequence motif enhances the surface expression of the potassium channel TASK-3. Traffic 8, 1093-1100.

9.    Putzke C, Wemhöner K, Sachse FB, Rinné S, Schlichthörl G, Li XT, Jaé L, Eckhardt I, Wischmeyer E, Wulf H, Preisig-Müller R, Daut J & Decher N (2007). The acid-sensitive potassium channel TASK-1 in rat cardiac muscle. Cardiovascular Research 75, 59-68.