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!
Last update August 2011