Helle Prætorius

Group Leader

Helle Prætorius
MSO Professor, PhD
More information

RESEARCH
The overall research interests is membrane transport and the influence of local signalling. The focus is primarily the local signalling system known as purinergic signalling, which involves cellular release of ATP reacting on specific, extracellular P2-receptors. Purinergic signalling is known to have a significant impact on membrane transport and how cells respond to hormonal, noxious and mechanical stimulation. As an example, we previous defined the primary cilium as a mechanical sensor of fluid flow, which is essential in epithelial polarity.

RESEARCH INTERESTS
Bacterial pore formersrequire P2X receptor activation to lyse red blood cells
Recently, we have recently shown that pore-forming toxins like ?-haemolysin from E. coli (HlyA) in itself are not sufficient to destroy the red blood cells. The insertion of the pore in the cell membrane triggers release of ATP. Once outside the cells, ATP acts as a signalling molecule amplify the cell destruction by increasing the membrane conductance through ionotropic P2X receptors. This finding does not only apply for HlyA but for a variety of cellular pore-formers including the membrane attack complex of the complement cascade. These findings give a new understanding of the pathology of many haemolytic disorders, and opens new therapeutic perspectives.

Cellular volume regulation in the lytic process
Surprisingly, HlyA does not only swell and lyse erythrocytes. Apparently the insertion of HlyA primarily triggers a significant volume reduction and crenation of the erythrocytes. This shrinkage is the consequence of activation of Ca2+ dependent K+ and Cl- channels. Our ongoing studies evaluate the contribution of known volume regulatory proteins in the pore-induced lysis of red blood cells. The perspective is to understand how intravascular haemolysis can be postponed through the modulation of membrane transport and signalling.

ATP release from renal epithelial cells
The kidney continuously handles enormous amounts of water and salt transport. This transport occurs across the epithelia and is tightly regulated by central hormones as antidiuretic hormone (arginine vasopressin, AVP) and aldosterone. There is however, increasing evidence of local signalling between the renal epithelial cells as important regulator of the epithelial function. Extracellular ATP inhibits the renal water and salt transport via specific P2X and P2Y receptors. ATP is released constitutively by the renal epithelial cells themselves. This can be observed as spontaneous increments of the intracellular Ca2+ concentration. Release of ATP is further provoked by for instance mechanical stimulation – and the signalling molecules are then able to communicate eventual danger signals to its fellow cells and coordinate a collective response against external stimuli. Our group has extensive experience with purinergic signalling in renal epithelial cells and is currently amongst other things in the midst of characterising the mechanism for ATP release in renal epithelia.

METHODOLOGIES
Live cell microscopy: Ca2+ imaging in cells or tissues under physiological conditions, wide field or structural illumination as well as total internal reflection microscopy.

Flow cytomerty: For cell size determination (electronic volume/side scatter) combined with fluorescence.

Lumenometry : for ATP determination (luciferin/luciferase).

Plate readers for absorbance and fluorescence

Animal models: Transgenic mice: For various P2- receptors, transporters and channels, disease models: sepsis models.

Cell and bacterial cultures: various renal epithelial cells, monocytes/macrophages, HlyA producing E.coli.

Protein analysis: immunoblotting and -cytochemistry

RNA analysis: RT-PCR and qPCR

COLLABORATORS

  • Dr. Niklas R. Jorgensen, Dept. of Clinical Biochemistry, Glostrup Hospital
  • MD-PhD Troels Krarup Hansen, Head of the Center for Emergency Reseach, Aarhus University Hospital
  • Prof. Friedrich Koch-Nolte, Institute of Immunology, University Medical Center, Hamburg, Germany
  • Prof. Nathan Shapiro at Beth Israel Deaconess Medical Center, Harvard University, Boston, USA
  • Peter Hanley, Institute for Physiology II, University of Münster, Germany
  • Prof. Karl Kunzelmann, Dept of Physiology, University of Regensburg, Germany
  • Jens Leipziger, MSO Professor 
  • Thomas Vorup-Jensen, Associate Professor
  • K. Jesper Reinholdt, Associate Professor
  • Knud Polsen, Associate Professor
  • Henrik Birn, MSO Professor
  • Daniel Otzen, Professor
  • Robert A. Fenton, MSO Professor 
  • Bente Vilsen, Professor

RESEARCH GROUP MEMBERS
Marianne G. Skals, postdoc; Randi G. Bjælde, PhD student; Steen K. Fagerberg, PhD student, Peter S. Munksgaard, resarch year student; C. Martin Söderström, research year student; medical student Julie L. Hejl; technician Helle Jakobsen

 

Henvendelse om denne sides indhold: 
Revideret 03.08.2016