The Cell Biophysics & Imaging Group
at the Netherlands Cancer Institute (NKI-AVL)

Kees Jalink, PhD, Investigator

Genomic- and high-throughput screening methods have identified tremendous amounts of biomedically relevant proteins. The functions of these proteins can not be fully understood without detailed knowledge of their localization, concentration, and particularly, their mutual interactions and activa­tion state in living cells. Many of these interactions are short-lived or exist very locally within the cell and therefore techniques with high spatiotemporal resolution are required to study them in single living cells. Our lab focuses on biophysical techniques to provide this resolution. Our lab is well-equipped for both electrophysiological and advanced biophotonic studies, and we develop and implement new techniques. We apply biophysics in our ongoing research and in a number of collaborations within and outside of the institute.  

Biophotonic techniques
Major techniques to obtain detailed spatiotemporal information on biomolecules rely on studying the interactions of cellular constituents with light, an area termed biophotonics. Proteins can be labelled with fluorescent tags like GFP or chemical fluorochromes and studied non-invasively by live cell imaging. However, due to the limited resolu­tion of light microscopy many essential parameters escape detection: examples are kinetic parameters such as on- and off-rates (often in the ms or us time range), protein-protein interactions, and protein confor­ma­tion/ activation state (both at nm-scale). Details on kinetic parameters and interactions are therefore derived indirectly by using approaches such as Fluorescence Recovery After Photobleaching (FRAP), Fluorescence Loss In Photobleaching (FLIP), Fluorescence Resonance Energy Transfer (FRET), Total Internal Reflectance Fluorescence (TIRF), Fluorescence Lifetime Imaging (FLIM), electrophysiological techniques, and Fluorescence Correlation Spectroscopy (FCS). A whole range of novel tools including fluorescent proteins in all colours, photo-activatable compounds (pa-GFP, light-inducible crosslinkers, and UV-releasable ‘caged’ second messengers have recently become available. Consequently, over the last one or two decades, ‘biophotonics’ has rapidly become an important tool in virtually all biomedical disciplines.

Ongoing research
One line of our research focusses on the spatial distribution of phosphoinositides along membranes. These lipids play crucial roles as second messengers in numerous processes. But how can a single, diffusible lipid regulate so many different processes with spatial precision? Imaging, FRET, FRAP and computer modelling have provided important insights.
We also study regulation of the channel TRPM7, a cation channel with intrinsic kinase that is involved in cell adhesion. We postulate that TRPM7 may function as a mechano receptor! TRPM7 gating depends on phosphoinositide signalling in a beautiful, but complex way. It’s close relative TRPM6, a key player in maintaining a healthy Mg2+ level in the body, is also studied.  
FRET sensors are genetically encoded constructs engineered to report on intracellular signaling events. Our sensors for messengers like PIP2 (the first lipid FRET sensor ever!) and cAMP are used in hundreds of labs, and we continue to develop new sensors and improve existing ones. Developing and testing a FRET sensor makes a nice student project!

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Last update October 2013