Protein and Drug Biochemistry


Validation of meprin α as antimigratory target in cancer

Project in cooperation with Molecular Biotechnology Unit as well as Astacin Proteases Unit

Peptide aggregates and microparticles for therapeutic applications

Countless human diseases, many of which are incurable, can be traced back to the misfolding and depositing of peptides or proteins. Protein misfolding diseases include, for instance, Alzheimer’s and Parkinson’s disease as well as other neurodegenerative diseases. In these cases, fibrillose structures are formed by the body’s own proteins that are extremely stable in the organism and cause cellular damage to the affected tissue. One therapeutic approach lies in the development of antibodies that mark the stable aggregates and pave the way for alternative degradation processes (phagocytosis). Characterizing the binding behavior to the aggregate is essential in developing these types of substances.

This collaboration project between Fraunhofer IZI (Department of Drug Design and Target Validation) and Fraunhofer IMWS therefore seeks to investigate the structure of fibrillose proteins (e.g. amyloid-α, ADan) using microscopic techniques (TEM, AFM). In order to do this, the peptides and/or proteins will be synthesized, purified and caused to aggregate in vitro. The binding of monoclonal antibodies to these structures will be characterized by means of immunogold labeling. To this end, the project partners came together to draw up a protocol for processing and preparing (contrast filling) the respective proteins. Using HAADF-STEM and AFM, accumulations of proteins with ring and globular structures were able to be detected on β-synuclein filaments, for instance, during protein aggregation. Investigations focused on antibody-fibril interactions demonstrate the binding of gold cluster-labeled antibodies to Aβ filaments, enabling the antibodies’ binding positions to be differentiated on the filaments. Assisted by surface plasmon resonance (Biacore™) and isothermal titration calorimetry (ITC), these investigations are valuable in developing antibodies and therefore serve as an exemplary model for protein drug development.

The project is being handled by the High Performance Center for Chemistry and Biosystems Engineering.

Therapeutic antibodies against active chemokines

Chemokines are signal proteins or peptides secreted by cells, which direct the movement of responding immune cells. The secretion of inflammatory cytokines is induced by inflammatory processes and pathogens. This causes the recruitment of leucocytes along a concentration gradient to the source of chemokine production. Dysregulation of chemokines plays a destructive role in many chronic inflammatory diseases like arthritis, multiple sclerosis and colitis. Due to the high presence of chemokines, originally providing the clearance of pathogens and damaged tissue, enhanced influx of immune cells causes attack of endogenous healthy structures in these diseases.

After cleavage of the signal peptide, some chemokines possess an N-terminal glutamine residue, which is subsequently converted to pyroglutamate under physiological conditions by glutaminyl cyclase activity. The resulting lactam ring is not protonated in the physiological pH range. This provides an elevated resistance against aminopeptidases and exoproteases, which need a protonated amino group for substrate binding.

Furthermore, enhanced receptor activation could be shown for the respective chemokines after N-terminal pyroglutamate formation. Chemokine cleavage by endoproteases, like matrix metalloproteinases, is not affected by an N-terminal pyroglutamate. However, it was described that truncation of chemokines by matrix metalloproteinases results in receptor antagonists, which are able to bind, but fail to activate the chemokine receptor.

Our approach is the development of protein drugs, which neutralize post-translationally modified chemokines. Besides the N-terminal modifications, also other structural elements might be important. In addition to antibodies, therapeutic proteins with antibody like properties will be developed in cooperation with industry partners.

Targeting post-translational protein modifications to treat neurodegenerative disorders

Neurodegenerative diseases are characterized by the progressive loss of brain substance. The degeneration of nerve cells coincides with the development of dementia, i.e. a qualitative and quantitative decline of brain cognitive performance. Due to the rise of life expectancy, dementia, especially Alzheimer Disease (AD), will pose a major challenge to our health systems in the decades to come. Prevalence rates in Germany identify 1.4 million diseased individuals, numbers worldwide approximate 44 million and are expteced to triple by the year 2050. Despite the fact that some medication is available to extenuate the symptomes of the diseases, no curative therapy is on hand right now.

The majority of neurogenerative diseases is ascribed to a misfolding of proteins. This structural modification results in an aggregation that damages the surrounding tissue and cells causing them to die off. An effective therapy needs to prevent the peptides from aggregation and to accelarate the decomposition of these proteins respectively.

Latest research findings show that various proteins are prone to structural changes (posttranslational modification), which often accelerates their deposition. Such modifications are, among others, N-terminal pyroglutamate and Isoaspartat formation, nitroyslation or phosphorylation.

This projects aims at identifying posttranslational modifications in deposited proteins that characterize the particular neurogenerative disease. The formation of the modification as well as strategies for its supression are under investigation. New substances may either prevent the modification of proteins (enzyme effectors) or target the modified proteins by binding to accelarate their degradation (protein drugs).