Tailor-made pharmaceuticals as basis for novel antidepressants

December 02, 2014

The FK506-binding protein 51 (FKBP51) is an established risk factor for stress-related psychiatric disorders such as major depression. Drug discovery for FKBP51 has been hampered by the inability to pharmacologically differentiate against the very similar functional counterplayer FKBP52. Scientists at the Max Planck Institute of Psychiatry in Munich have now developed the first potent and highly selective inhibitor of FKBP51. The so-called SAFit-ligand inhibits FKBP51 enhancing growth of neuronal cell cultures and improving stress-coping behavior in mice. These findings provide the structural and functional basis for the development of mechanistically novel antidepressants.

FKBP51 and FKBP52 are proteins which regulate multiple cellular activities. Most importantly in the context of psychiatric diseases, they interact in an antagonistic manner with receptors for stress hormones in the brain. FKBP51 inhibits while FKBP52 enhances the activity of the glucocorticoid receptor, thus playing a major role in the regulation of stress responses.

For the first time, scientists around Felix Hausch, Project Group Leader at the Max Planck Institute of Psychiatry and lecturer at the Ludwig-Maximilians-University in Munich, developed highly selective inhibitors of FKBP51 by an induced-fit mechanism. "We initially used a chemical genetics approach and then, step by step, improved the fitting of our inhibitors," describes Steffen Gaali, post-doctoral student in the project group of Felix Hausch and first author of the current study. "Finally the most potent ligand SAFit, a selective Antagonist of FKBP51 by induced fit, had a more than 10,000-fold selectivity for FKBP51 over FKBP52." SAFit exactly fits into a pocket of FKBP51 by pushing out one of the protein's amino acid side chains. This conformational change cannot occur in the FKBP52 protein.

In further experiments, the researchers investigated the characteristics and effects of the SAFit-ligand. In cell culture, SAFit potently stimulated the differentiation of neuronal cell lines. Unlike former inhibitors of FKBP51, the new pharmacological agent did not show any immunosuppressive side-effects. Further, SAFit displayed antidepressant-like activity in mice. By inhibiting FKBP51, the protein's inhibitory effect on the glucocorticoid receptor is reduced in the brain. Thus, SAFit enhances the regulation of one of the key stress-coping mechanisms, the HPA axis.

"Depression is likely a biologically heterogeneous disease and a major shortcoming is the inability to match antidepressant agents to the specific underlying biological alterations," explains Felix Hausch. "Patients with FKBP51-hyperinducing gene variants or with a hyperactive HPA axis can be clinically identified by genotyping for FKBP51 and/or the Dex-CRF test." Taken together, by generating the SAFit-inhibitor, the Max Planck scientists provide the proof-of-principle for selective FKBP51 inhibitors as a mechanistically novel treatment for stress-related psychiatric disorders.

Further Information (HPA axis and Dex-CRF test)

The hypothalamic-pituitary-adrenal axis (HPA axis) is a complex set of interactions among the hypothalamus, the pituitary gland and the adrenal glands. The interactions among these organs play a major role in the control of reactions to stress and regulate many processes, including digestion, the immune system, mood or emotions. The stress-induced release of corticotropin-releasing factor (CRF) by the hypothalamus leads to increased cortisol production in the adrenal glands. Cortisol itself facilitates an adaptive phase in which alarm reactions including the immune response are suppressed, allowing the body to attempt countermeasures against the stress.

The activity of the HPA axis can be measured with the Dex-CRF test. The release of cortisol is significantly higher in some groups of depressed patients than in non-depressed controls, indicating hyperactivity of the HPA axis.
Original publication:

S. Gaali, A. Kirschner, S. Cuboni, J. Hartmann, C. Kozany, G. Balsevich, C. Namendorf, P. Fernandez-Vizarra, C. Sippel, A.S. Zannas, R. Draenert, E.B. Binder, O.F.X. Almeida, G. Rühter, M. Uhr, M.V. Schmidt, C. Touma, A. Bracher, F. Hausch.

Selective inhibitors for the psychiatric risk factor FKBP51 enabled by an induced-fit mechanism

Nature Chemical Biology, 1 December 2014 | http://dx.doi.org/10.1038/nchembio.1699


Related Stress Articles from Brightsurf:

Stress-free gel
Researchers at The University of Tokyo studied a new mechanism of gelation using colloidal particles.

Early life stress is associated with youth-onset depression for some types of stress but not others
Examining the association between eight different types of early life stress (ELS) and youth-onset depression, a study in JAACAP, published by Elsevier, reports that individuals exposed to ELS were more likely to develop a major depressive disorder (MDD) in childhood or adolescence than individuals who had not been exposed to ELS.

Red light for stress
Researchers from the Institute of Industrial Science at The University of Tokyo have created a biphasic luminescent material that changes color when exposed to mechanical stress.

How do our cells respond to stress?
Molecular biologists reverse-engineer a complex cellular structure that is associated with neurodegenerative diseases such as ALS

How stress remodels the brain
Stress restructures the brain by halting the production of crucial ion channel proteins, according to research in mice recently published in JNeurosci.

Why stress doesn't always cause depression
Rats susceptible to anhedonia, a core symptom of depression, possess more serotonin neurons after being exposed to chronic stress, but the effect can be reversed through amygdala activation, according to new research in JNeurosci.

How plants handle stress
Plants get stressed too. Drought or too much salt disrupt their physiology.

Stress in the powerhouse of the cell
University of Freiburg researchers discover a new principle -- how cells protect themselves from mitochondrial defects.

Measuring stress around cells
Tissues and organs in the human body are shaped through forces generated by cells, that push and pull, to ''sculpt'' biological structures.

Cellular stress at the movies
For the first time, biological imaging experts have used a custom fluorescence microscope and a novel antibody tagging tool to watch living cells undergoing stress.

Read More: Stress News and Stress Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.