AMPK: a multiprotein drug target unravelled

Company

CRELUX GmbH (a WuXi AppTec Company)

Challenge

AMPK (AMP-activated protein kinase) is a Ser/Thr kinase composed of two regulatory subunits and a catalytic subunit  that together as a complex regulates the levels of energy in the cells. This complex is evolutionarily conserved and ubiquitously expressed. There are a total of 12 possible isoforms, which are distributed in the human body in a tissue-specific manner. For example, one isoform is highly expressed in skeletal muscles and a different  isoform is more specific to heart, brain or liver.  All in all, AMPK senses the energy levels of the cells (in the form of the so-called ATP) and allows upstream signals to activate it, in response to external nutritional stress.  AMPK substrates are involved in lipid metabolism, autophagy, mitochondrial biogenesis, and in the maintenance of glucose homeostasis. Therefore, this complex is a highly promising therapeutic drug target against diabetes, obesity, Wolff-Parkinson-White Syndrome, cancer, and aging.

There are, however, several challenges to generate soluble and stable complexes, and this is one of the many reasons why not many X-ray structures are available, especially at resolutions suitable to drive drug discovery efforts. Firstly, it is very complicated to be able to make crystals of the complex with the activated compound bound to it. Another obstacle is the extreme sensitivity of the tiny crystals to radiation damage. 

CRELUX/ WuXi AppTec, a company expert worldwide in premium drug discovery solutions for global pharma, biotech and research organizations, came to the ESRF to tackle this  challenge. 

Sample

CRELUX/WuXi AppTec used their expertise to design and produce a fully functional AMPK complex with the needed yield, purity, and specific post-translational modifications for successful crystallization and X-ray structure determination of an active complex. The AMPK sample contains an kinase activating compound and three AMP nucleotides (ATP-depleted scenario) bound to it.

Solution

CRELUX/WuXi AppTec scientists sent crystallized AMPK samples to the ESRF’s ID30-A beamline. Because of the complexity of the project, they needed a powerful beamline, state-of- the-art detector and a skillful scientist in-house to carry out the experiment. They managed to solve the structure of the complex at a resolution of 2.9 Angstroms, which was enough for CRELUX/WuXi AppTec to see the detailed chemical enviroment of the compound in the complex binding site. This corresponds to one of the highest resolution structure published so far for any AMPK isoform.

Benefits

The work at the ESRF will help CRELUX/WuXi AppTec to support their clients in the discovery and development of novel and more specific drugs that can influence AMPK activity in the cell and, as a result, adjust the energy balance in disease affected organs. Debora Konz Makino, Lab Head at CRELUX/WuXi AppTec, explains: ”Our long-standing collaboration with ESRF has greatly contributed to the success of most of our client's projects in the early stages of drug discovery. ESRF provides not only cutting edge infrastructure, but also excellent scientific support for X-ray data collection of biological macromolecules. We at CRELUX highly appreciate ESRF prompt and open communication.” 

The AMPK structure solved. Credits: CRELUX.

Top image: A crystal of the sample. Credits: CRELUX.