#	project manager	location	title
P1	Baukrowitz, T.	Kiel	currently under construction
P2	Budde, T. Meuth, S.G.	Münster	Modulation, function and neuroprotective potential of TASK and TREK channels in the central nervous system
P3	Decher, N.	Marburg	currently under construction
P4 (involved 2008-2011)	Köhler, R. Hoyer, J.	Marburg	Physiological and pathophysiological relevance of vascular K2P channels
P5	Schulze-Bahr E.	Münster	currently under construction
P6	Warth, R. Bandulik S.	Regensburg	Role of TASK potassium channels for adrenal gland and respiratory physiology
P7	Daut, J.	Marburg	currently under construction
P8	Oliver, D.	Marburg	currently under construction
P9	Schwappach, B.	Göttingen	Intracellular transport of the two-pore domain potassium (K2P) channels TASK-1 and TASK-3

currently under construction



Staff:

Dr. Hariolf Fritzenschaft	Dr. Markus Rapedius	Murali Krishna Bollepalli	Paula Piechotta

Modulation, function and neuroprotective potential of TASK and TREK channels in the central nervous system

Until now we have analyzed the function of TASK-1 and TASK-3 channels in thalamocortical relay neurons of dorsal part of the lateral geniculate nucleus (dLGN). While these cells are regarded as prototypical relay neurons, the expression level of TASK channels is rather moderate. Therefore we now plan to analyze thalamic cell types with strong expression of specific TASK channel subtypes. For TASK-1 this is true for cells of the centromedian intralaminar nucleus (CM). For TASK-3 this is true for cells of the anterodorsal nucleus (AD). Thus these cells may be regarded as prototypical for neurons expression a specific TASK channel subtype. Furthermore we now extend our studies to analyze the elusive dLGN interneurons which seem to synchronize thalamic activity and to TRESK channels which have yet not been extensively studied in the brain. In order to be able to reliably identify the small and rare GABAergic interneurons we will use transgenic GAD67-GFP mice. Crossbreeding with TASK-1- and TASK-3-deficient mice will allow the investigation of specific channel function in interneurons. Possible pathophysiological alterations of K2P channels will be analyzed in a mouse model of human absence epilepsy (backcross of C3H/HeJ mice).

Staff:

Pawan Bista	Stefan Bittner	Petra Ehling
Patrick Meuth	Manuela Cerina

currently under construction



Staff:

Susanne Rinné	Konstantin Wemhöner	Anne-Kathrin Streit	Michael F. Nette
Magdalena Walecki	Franca Kempf	Mathias Goldstein	Diana Salek

Physiological and pathophysiological relevance of vascular K_2P channels

The vascular endothelium is a central regulator of vascular function. Release of modulators, like NO and prostaglandins, as well as EDHF control vessel tone. These endothelial effector systems are mainly Ca²⁺-dependent. Therefore an intact endothelial function requires effective control of the intracellular Ca²⁺ homeostasis by Ca²⁺-permeable ion channels and the membrane potential via hyperpolarizing channels. Recent studies began to unravel the role of endothelial hyperpolarization and the EDHF system especially by characterizing hyperpolarizing K⁺ channels. The present project will further advance the molecular and mechanistic characterization of K⁺ channels by focussing on the newly identified K_2P channels as part of the endothelial vasodilatory system. The first goal of the present project is to identify K_2P channels in the wall of blood vessels and to characterize and understand their physiological function in the regulation of vessel tone. A second goal of our project is to clarify whether an altered function of K_2P channels is of pathomechanistic relevance for cardiovascular diseases. We hypothesize that mechanosensitive and pH-sensitive K_2P channels, especially of the TREK-1 type, act as a protective vasodilatory reserve during hypertonia. In this respect we will investigate whether K_2P channels may represent pharmacological targets for antihypertensive therapy.




Genetic Variation in K_2P channel genes and cardiac arrhythmias

Genetic variations in K_2P channels are widely unknown to date. Recently the first gene mutations were described in a family affected by migraine with aura (KCNK18) and in patients with Barel Birk syndrome, a very rare and complex malformation syndrome (KCNK9). That shows a clinical relevance of this ion channel family in monogenetic disorders. Our investigations implicate that mutations in KCNK genes might be a new genetic cause of arrhythmias of unknown origin. We have identified a classical gain of function mutation in a patient and two further mutations in patients with the same phenotype where the analyses are in progress. The gene mutations we have identified so far will be characterized biochemically and electrophysiologically (in cooperation with FOR1086). Furthermore we will analyze additional patients in the identified groups of disease and in other groups to get a comprehensive view of the relevance of the genetic variation in cardiac expressed K_2P channel genes and the functional consequences in heart disease.

Staff:

Dr. Birgit Stallmeyer	Dr. Corinna Wewer	Sabine von Rüden

Role of TASK potassium channels for adrenal gland and respiratory physiology

TASK-1 and TASK-3 channels are involved in many physiological processes. They are key regulators of adrenal hormone synthesis, and they seem to be decisive for chemoreception and respiratory control. During the second period of funding, we will focus on the role of TASK channels for the normal and pathological function of the adrenal cortex and for the control of respiration. The main points of our interest are:

• Why are neonatal TASK-3 knockout mice hyperaldosteronic? Are the underlying mechanisms important for the physiological control of aldosterone secretion?
  
• What is the function of TASK-1 and TASK-3 potassium channels in native adrenal cells?
  
• How is the respiration influenced by inactivation of TASK-1 and TASK-3 channels in mice? Is the inhibition of TASK channels a possible novel therapeutic strategy for respiratory diseases (e.g. sleep apnea)?
  

Our general aim is to gain new insights into the pathophysiology of TASK channels and their potential relevance for human diseases. The results could help to improve our understanding of aldosterone secretion and adrenal gland development as well as the molecular mechanisms underlying chemoreception and respiratory control.


Staff:

Philipp Tauber	David Penton Ribas	Ines Tegtmeier	Christina Sterner

currently under construction





currently under construction





Intracellular transport of the two-pore domain potassium (K_2P) channels TASK-1 and TASK-3

14-3-3 proteins are switch proteins that influence many cellular processes. One such process is the cell surface expression of multimeric membrane proteins, in particular ion channels and receptors. 14-3-3 proteins antagonize sorting signals present in the individual subunits of these membrane proteins. These peptide sorting motifs are also recognised by the COPI vesicle coat complex thereby leading to the retrieval of unassembled or unphosphorylated subunits. Properly assembled and phosphorylated multimers can engage 14-3-3 proteins and hence travel the secretory pathway to the cell surface.

K_2P channels are a class of membrane proteins that require 14-3-3 protein binding to reach the cell surface. The project addresses structural and mechanistic aspects of 14-3-3 binding to K_2P channels by further elucidating steric aspects of the interaction (relationship between valency of binding sites and avidity, quantitative effect of amino acid side chain exchanges). Furthermore it will be elucidated how COPI recognizes these sorting signals – the mode of recognition is already known to differ from that of canonical COPI binding motifs. The project aims to purify K_2P channels and associated Proteins from native tisues. A directed crosslinking approach will be employed to identify the physiologically relevant kinase responsible for phosphorylating the 14-3-3 binding site.