In October 2002 Prof. Friedrich W. Herberg joined the Institute of Biology in the Faculty of Mathematics and Natural Sciences at Kassel University. Currently he leads a group of about 20 people working on cyclic nucleotide signalling (see picture1) and protein kinases structure and function with a focus on cAMP dependent protein kinase (PKA). We use PKA as a model system to understand basic mechanism of protein kinase function as well for the development of novel biotechnological and pharmaceutical tools. The PKA-Model system is also used to implement and validate techniques from functional proteomics. Here a main focus is the detailed characterization of molecular interactions within cellular protein networks employing a variety of techniques summarized under Biomolecular Interaction Analysis (BIA).

D. Bertinetti, PhD thesis, 2007

Picture 1: cAMP-signaling
Extracellular stimuli i.e. hormones (ligand) bind to a G-Protein coupled receptor (GPCR) and activate via a trimeric G-protein an Adenylate Cyclase (AC) generating the second messenger cAMP whereas
Phosphodiesterases (PDEs) degrade cAMP. Primary target of cAMP are the Regulatory subunits (R) of PKA releasing the Catalytic subunits (C) after cAMP-binding. Further targets of cAMP are cyclic nucleotide gated channels (CNG) and hyperpolarization-activated cyclic nucleotide - gated cation channel (HCN) as well as the exchange protein activated by cAMP (Epac). A-Kinase Anchoring Proteins (AKAPs) mediate the spatial/temporal organization of PKA-signalling. The heat stable Protein Kinase Inhibitor (PKI) controls PKA-activity in the nucleus.

We were among the first to quantify the binding affinities of various effectors in cAMP-signaling (PKA subunits, cyclic nucleotides, A-Kinase Anchoring Proteins (AKAPs), Phosphodiesterases, Epac…..). We investigate the effects of nucleotides, metal ions, substrates and cofactors on binding kinetics between the catalytic (C)-subunit and physiological inhibitors, i.e. the regulatory subunits (R) and the heat stable protein kinase inhibitor (PKI). We investigate the role of components of the cAMP-signaling system in the context of neuropathic pain. Recently we have expanded our work to structure / function studies on the cGMP-dependent protein kinase (PKG) in humans and in Plasmodium falciparum with a focus on isoenzyme selectivity towards cyclic nucleotides In studies on function and regulation of Park 8 (LRRK2) we address the interplay between LRRK2 and PKA and generated a new mechanistic model to explain how the LRRK2 mutations R1441C/G/H can mediate Parkinson pathogenesis. Other second messengers like cdiGMP crucial in bacterial regulation are investigated by BIA and cyclic nucleotide analogs.

Understanding the structure and function of kinases is essential for the analysis complex cellular signal transduction events. The main focus of the group is on research on the molecular basis of fine tuning kinase activity employing biochemical, biophysical, cell biological and bioinformatical technologies, e.g. surface plasmon resonance (SPR), fluorescence polarisation (FP), isothermal titration calorimetry (ITC), bioluminescence resonance energy transfer (BRET) and FRET. Those BIA–techniques are applied within a national wide research consortium funded by the German Federal Ministry of Education and Research (BMBF), the European Union and the Deutsche Forschungsgemeinschaft (DFG) as well as the University of Kassel. The group has a long standing expertise in particular in surface plasmon resonance, a technique that is exquisitely sensitive and capable of monitoring the association and dissociation rate constants of biomolecular interactions. We have several Biacore instruments as well as SPR-devices from Sierra Sensors and are in mutual exchange with the Biaffin GmBH & CoKG, a spin off from the Biochemistry department.

In addition, the group is part of the Center of Interdisciplinary Nanostructure and Science (CINSaT) generating miniaturised devices for advanced biosensing at increased sensitivity and throughput.