Prof. Dr. Michael Schaefer
Rudolf-Boehm-Institut für Pharmakologie und Toxikologie
Härtelstr. 16-18
04107 Leipzig, Germany
Phone: +49-(0)341-9724600
Fax: +49-(0)341-9724609

multicolor TIRF image

Research interests

1. Structure, biophysics and regulation of transient receptor potential channels

Vision in Drosophila melanogaster and other insects and arthropoda is mediated by a Rhodopsin-induced activation of a G protein of the Gq family coupling to an eye-specific phospholipase C (the gene product of "no receptor potential A"; norpA). As a result of phospholipase C activation, cation entry into the photoreceptor cell is transmitted by channels of the "transient receptor potential" (TRP) family. The 28 mammalian homologues of TRP encode a highly versatile group of cation channels, which are either activated via phospholipase C (the "canonical" TRP channels TRPC1-TRPC7) or via a plethora of input signals including heat, cold, acidic pH, intracellular calcium, lack of intracellular magnesium, numerous environmental agents and irritants, lipids, voltage and possibly mechanical forces. The gene products of mammalian TRP channels group into canonical TRPC channels, vanilloid receptor-related TRPV channels, melastatin related TRPM channels, polycystin-related TRPP channels, the ankyrin-rich TRPA1 and the more distantly related mucolipidins. Our group investigates regulatory and biophysical features of several TRP family members that form Na+ and Ca2+-permeable cation channels. In addition, we are investigating the mechanisms and the specificity of the TRP channel subunit assembly into homo- or heterotetrameric channel complexes.

Specific topics:
- Gating of TRPM2 and of TRPA1
- Pharmacological modulators of TRP channels
- TRPV1 - a proton-permeable channel in nociceptive neurons
- Homo- and heterooligomeric assembly of TRPC and TRPV channel subunits

2. Visualization of receptor-induced signalling processes in living cells

Engineered fusion proteins of signalling proteins intramolecularly linked to various color variants of the green fluorescent protein have fueled novel approaches to gather information about the spatiotemporal orchestration of signal transduction in living cells. These genetically encoded fluorescent fusion proteins can be directly visualised by fluorescence microscopy without a need for additional cofactors. Thus, they may serve to follow the localization of signaling proteins in living cells at the subcellular level and in a sub-second temporal resolution. Signalling proteins that are being investigated in our group include protein kinases C, phospholipases C, phosphatidylinositol-3-kinases, receptor-tyrosine kinases, the nonreceptor tyrosine kinases Pyk2 and Src and ion channels. Our scientific interest is to understand more precisely the spatiotemporal properties and the interplay between various signaling processes and their contribution to cell biological responses.
Both methodological development and biological problems are addressed in our group. Examples are i) the fingerprinting of spectrally overlapping fluorochromes and its application to simultaneously record multiple signalling processes in living cells, ii) fluorescence resonance energy transfer (FRET) methods and their use in the determination of ion channel assembly, protein interactions of phosphoinositide-3-kinases and time-resolved monitoring of intramlecular conformational changes, iii) quantitative fluorescence recovery after photobleaching (FRAP) analysis to assess the lateral mobility of membrane-associated or cytosolic signalling proteins and iv) the quantitative analysis of ion concentrations and of the membrane translocation during receptor-induced cell activation. To more selectively observe signalling processes at the plasma membrane, we have set up two fluorescence microscopes that operate in the total internal reflection (TIR) mode. To obtain more information about the protein function, the stability of protein-membrane interactions or protein-protein interactions in the plasma membrane, these microscopes can additionally measure FRET, FRAP, fluorescence lifetime or anisotropy decay in the TIR configuration.

Specific topics:
- Computer-assisted fingerprinting of signals emanating from spectrally overlapping fluorochromes
- Receptor-induced translocation of protein kinases C
- Fluorescence resonance energy transfer FRET and various applications
- TIRF imaging technique
- Regulation and domain organization of phosphoinositide-3-kinase g

The group:

Dr. Kerstin Hill (postdoc) group leader: Physiological and pathophysiological roles of TRP channels
Isabelle Straub (PhD student) topics: Pharmacological modulators of Stim:Orai complexes, patch clamp analyses
Anke Klein (PhD student) topics: Voltage sensor domains, protein asymmetry in migrating cells
Melanie Kaiser (PhD student): Natural compounds modulate P2X7
Tanja Plötz (PhD student): Allosteric modulatory sites on P2X receptors
Beatrice Oehler (MD student): Pharmacological modulation of TRPA1
Cristoph Hempel (MD student): Novel modulators of P2X7
Marion Leonhardt (technician) molecular biology, cell culture, lab organisation
Nicole Urban (technician) digital fluorescence video imaging, screening, FLIPR
Helga Sobottka (technician) cortical and hippocampal neurons, calcium imaging, patch clamp

Former group members: