Using financial resources economically and in compliance with the constitution does not automatically mean that they foster the purpose well. Fostering well comprises more than the mere sum of the donations. The Hans and Ilse Breuer Foundation has therefore made it its goal to ask the award winners about the impact of the funded projects. In relation to the research award, this means investigating the question of what new knowledge the respective research award winner has gained through the use of the award money in a research project. These can be changes at the level of knowledge, e.g. new therapeutic approaches or a better understanding of the complex relationships in the brain.
„Significant progress in understanding the biological and genetic factors „
Summary
With the generous support of the Hans und Ilse Breuer Stiftung, the 100-plus Study has made significant progress in understanding the biological and genetic factors that contribute to healthy aging and resilience to Alzheimer’s disease. One of our key achievements was the successful generation of 20 induced pluripotent stem cell (iPSC) lines from centenarians, providing researchers with a valuable resource for studying cellular aging and neurodegenerative diseases. These cell lines are already being shared with other scientific institutions to further advance Alzheimer’s research. Additionally, with the Foundation’s support, we were able to continue blood-based biomarkers commonly used in Alzheimer’s diagnostics. Importantly, the Foundation’s funding enabled us to strengthen project support, with a key role in managing the many administrative tasks associated with the 100-plus Study and with the research group. Overall, the support of the Hans und Ilse Breuer Stiftung has been instrumental in advancing our research, fostering collaboration, and helping us make significant strides in the study of healthy aging and cognitive resilience. We are deeply grateful for the Foundation’s contribution to our work and look forward to continuing this important research.
Final Report
We would like to express our sincere gratitude to the Hans und Ilse Breuer Stiftung for its generous support of the 100-plus Study. With your help, we have made significant progress in understanding how some people can maintain cognitive health even as they reach and surpass 100 years of age. Our work aims to identify the genetic, biological, and environmental factors that contribute to healthy aging and resilience to diseases like Alzheimer’s. Below, we summarize the key results achieved with the help of your funding.
- Generation of Stem Cell Lines from Centenarians
One of the core goals of the 100-plus Study was to generate induced pluripotent stem cells (iPSCs) from cognitively healthy centenarians. These iPSCs are created from regular cells in the body (such as skin cells) and reprogrammed to a stem cell state, where they can then be used for a variety of research purposes.
With the help of your funding, we have successfully generated 20 iPSC cell lines from centenarians. These unique cell lines offer valuable insights into cellular aging and provide researchers with an important tool to study neurodegenerative diseases like Alzheimer’s. These cells are shared with other research groups to promote collaboration. Ethical and legal agreements are currently being established to ensure this sharing is done responsibly.
- Study of Alzheimer’s Biomarkers in Centenarians
The grant has also allowed us to extend the research of a PhD student in our team, who is investigating the relationship between specific blood-based biomarkers and cognitive function in healthy centenarians. These biomarkers, such as Aβ42, Aβ40, pTau-181, NfL, and GFAP, are often used in diagnosing Alzheimer’s disease. However, it remains unclear how they behave in people who remain cognitively healthy at an advanced age.
The research of the PhD student focuses on determining how these biomarkers change as people age, and to what extent age itself should be considered when interpreting these biomarkers. This is particularly important for Alzheimer’s diagnostics, as current tests may not account for natural changes that occur due to aging rather than disease. By studying these biomarkers in centenarians and their family members, we hope to improve the accuracy of diagnostic tools for Alzheimer’s and related disorders.
- Project Support and Staffing
As the 100-plus Study expands, logistical and administrative support is critical to its continued success. The funding from the Hans und Ilse Breuer Stiftung enabled us to hire two important staff members, who provided essential support in managing the project. Their work includes coordinating data collection, ensuring smooth communication between team members, and managing other administrative tasks. This kind of project support is vital to keep our research running efficiently, as funding agencies often focus primarily on research staff and materials. The contribution toward these positions has greatly improved our ability to advance the project.
Conclusion
The support from the Hans und Ilse Breuer Stiftung has been instrumental in helping the 100-plus Study make meaningful progress toward its goals. With your assistance, we have generated valuable scientific tools, advanced our understanding of biomarkers in aging, and made strides in uncovering the genetic secrets of resilience to Alzheimer’s disease. We are excited to continue our work and share these findings with the scientific community, where they will contribute to the development of better diagnostic tools and treatments for Alzheimer’s and other age-related diseases. Your support has made a significant difference, and we are deeply grateful.
„Deeper understanding of the function of phagocytes in old age“
Prof. Simonis and his team are interested in the function of phagocytes in the brain. Phagocytes are an important component of the innate immune response and are responsible for the destruction of invading pathogens, but also of the body’s own material such as amyloid plaques. The inclusion of the particles takes place via the formation of phagosomes, which fuse with special vesicles, the lysosomes, after uptake of the particles. In order to investigate the function of these cells, the research team inject a toxin into the white matter of the brain to locally damage the myelin sheath. The damaged myelin is then taken up by phagocytes into the interior of the cell and digested. However, if this experiment is carried out in older animals, an accumulation of undigested residues is found in the cell. In older animals, cholesterol is deposited in the lysosomes of the phagocytes. The cholesterol originates from the myelin sheaths, which consist of a high proportion of cholesterol. The accumulation of cholesterol triggers an inflammatory reaction after some time. The deposits occur because the phagocytes are unable to break down cholesterol molecules. The excess cholesterol has to be removed by lipoproteins. In the brain, this task is primarily performed by apolipoprotein E. These findings are relevant for understanding the function of phagocytes in old age.
„Deeper understanding of the function of phagocytes in old age“
Prof. Simonis and his team are interested in the function of phagocytes in the brain. Phagocytes are an important component of the innate immune response and are responsible for the destruction of invading pathogens, but also of the body’s own material such as amyloid plaques. The inclusion of the particles takes place via the formation of phagosomes, which fuse with special vesicles, the lysosomes, after uptake of the particles. In order to investigate the function of these cells, the research team inject a toxin into the white matter of the brain to locally damage the myelin sheath. The damaged myelin is then taken up by phagocytes into the interior of the cell and digested. However, if this experiment is carried out in older animals, an accumulation of undigested residues is found in the cell. In older animals, cholesterol is deposited in the lysosomes of the phagocytes. The cholesterol originates from the myelin sheaths, which consist of a high proportion of cholesterol. The accumulation of cholesterol triggers an inflammatory reaction after some time. The deposits occur because the phagocytes are unable to break down cholesterol molecules. The excess cholesterol has to be removed by lipoproteins. In the brain, this task is primarily performed by apolipoprotein E. These findings are relevant for understanding the function of phagocytes in old age.
„Drug development for Alzheimer’s disease can be made more efficient and safer“
Development of safe and efficient drugs for Alzheimer’s disease – More than 1 million people in Germany suffer from Alzheimer’s disease. In Alzheimer’s research, we are working hard to develop safe and efficient drugs to treat the causes of this disease. Target molecules for drug development include certain enzymes in the brain that act as molecular scissors and cut the Alzheimer’s protein into smaller pieces. One of these fragments can form clumps that damage the nerve cells in the brain and ultimately lead to Alzheimer’s disease. With the help of the Breuer Prize, Prof. Lichtenthaler and his team have developed new analytical methods with which we then discovered that these molecular scissors not only cut the Alzheimer’s protein, but also other proteins in the brain. However, this means that inhibiting the molecular scissors with medication could potentially lead to undesirable side effects, as the other proteins are no longer cut. In order to prevent such side effects, Prof. Lichtenthaler and his team have found out which of the other proteins are particularly important in the brain. They are now developing diagnostic detection methods to easily measure precisely these proteins and their fragments in the cerebrospinal fluid and in the blood. This will make it possible in future to find the right dose of medication for each patient in order to achieve maximum efficiency while minimizing side effects. In summary, the Breuer Prize helps Prof. Lichtenthaler and his research group to make drug development for Alzheimer’s disease more efficient and safer.
„Toxicity of the dipeptide repeat (DPR) proteins“
An astonishing number of patients suffering from frontotemporal dementia (FTD) and amyotrophic lateral sclerosis (ALS) have other affected individuals in their family. Genetic studies in these families have identified numerous causative mutations. The most common is a mutation in a barely characterized gene with the cryptic name C9orf72, which affects approx. 5-10% of all ALS/FTD patients. Patients with this mutation show a massive elongation of several hundred or even thousand repeats of a (GGGGCC)n sequence in the non-coding part of the C9orf72 gene. Prof. Edbauer ans his team discovered that the extended (GGGGCC)n sequence is unexpectedly translated into aggregating proteins in all reading frames. This results in five so-called dipeptide repeat (DPR) proteins (Mori et al, Science 2013), which form numerous deposits in the nerve cells of the patients.
The key questions now are what role the DPR proteins play in the development of the disease and how toxic effects can be treated with medication. Thanks to the support of the Hans and Ilse Breuer Foundation research prize, Prof. Edbauer and his team were able to investigate the toxic effect of DPR proteins in cell culture and in mouse models in more detail. They were particularly interested in the association of DPR proteins with cytoplasmic TDP-43 deposits, because these aggregates are also observed in ALS/FTD patients without C9orf72 mutation and are probably a direct cause of cell death. They discovered that DPR proteins interfere with the normal import of TDP-43 into the nucleus and thus promote its aggregation in the cytoplasm (Khosravi et al., Hum Mol Genet 2017).
Furthermore, they were able to demonstrate an interaction between two of the DPR proteins and ribosomes as well as other RNA-binding proteins. This is thought to chronically disrupt the entire cellular translation and trigger neurodegeneration (Hartmann et al., Life Sci Alliance 2018). In cell culture, the team was able to show that monoclonal antibodies inhibit the aggregation and cell-to-cell transfer of DPR proteins (Zhou et al., EMBO Mol Med 2017). His research group is now testing the efficacy of this therapeutic approach in a transgenic mouse model for C9orf72 ALS/FTD that they have previously established and characterized in more detail (Schludi et al., Acta Neuropathol 2017). Prof. Edbauer used part of the prize money to purchase a 96-channel pipette and other equipment for high-throughput analysis of biological samples. This enabled him to develop a semi-automated method to test the efficacy of hundreds of drugs simultaneously in stem cells from C9orf72 patients. He is initially testing a collection of drugs that have already been approved for other diseases. If an already known drug proves to be effective in C9orf72 cells, this would be a promising therapeutic approach with fewer hurdles for an early clinical trial in patients.
„Identification of new targets for future course-modified treatment approaches“
In numerous neurodegenerative diseases, the involvement of inflammatory mechanisms is increasingly crystallizing as an essential component of disease development and progression. Microglial cells as representatives of the innate immune system in the CNS are simulated by aggregates of misfolded proteins or nucleic acids. Their neuroprotective and homeostatic effect under physiological conditions leads to a chronic inflammatory process that contributes to neuronal cell death via pro-inflammatory cytokines. Our work focuses on the NLRP3 inflammasome. This is a signaling pathway that is at the beginning of the activation of the innate immune system and plays a key role in the development of chronic inflammation in the brain.
Prof. Heneka and his team first demonstrated the activation of this inflammatory signaling mechanism in the brains of Alzheimer’s patients using immunohistochemical and biochemical methods. Interestingly, a strong activation of the NLRP3 immune mechanism was already detectable in patients with mild cognitive impairment (MCI), suggesting that the observed activation takes place before the dementia stage is reached. In a next step, they were able to show that the genetic blockade of the NLRP3 inflammasome has a neuroprotective effect in a mouse model of Alzheimer’s disease. The blockade of the NLRP3 inflammasome prevented the inflammatory activation of microglia, which subsequently showed improved degradation of amyloid deposits in the brains of the mice. Of particular importance was the finding that the reduced inflammatory response and improved degradation of amyloid deposits resulted in protection of synaptic connections and significantly improved hippocampal function. Since neuroinflammation starts early and before the onset of clinical symptoms of Alzheimer’s disease, the mechanisms involved are attractive targets for future course-modifying treatment approaches.
„Detection of early transport disorders in degenerative diseases of nerve cells“
Many diseases of the brain and nerve cells, including Alzheimer’s disease, are characterized by the death of nerve cells. As this death is irreversible, it is a central concern of research into these neurodegenerative diseases to understand why nerve cells are so vulnerable. One reason lies in the unusual shape of these cells: A tiny cell body supplies a huge cell process with building blocks and nutrients – this cell process, the axon, is often hundreds to thousands of times longer and larger. To maintain the axon, nerve cells have developed a complex transport system that allows them to secure this supply under normal conditions. Under disease conditions, however, this system becomes unbalanced – and the process of death begins.
With the support of the Breuer Foundation, the laboratory of Prof. Misgeld is developing methods to study these supply and transport processes in living cells and animal models. To do this, they use genetic techniques to visualize the cellular building blocks (e.g. by introducing luminescent proteins) and observe their movement patterns in the context of various neurological disease models using modern microscopy approaches. For example, they have been able to show that in models of degenerative diseases of the nerve cells that move our limbs, or in models of multiple sclerosis, an inflammatory disease of the nervous system, transport disorders occur early on. They were also able to prove that similar phenomena also occur in a strictly localized form as part of the normal development of these nerve cells. Thanks to the support of the Breuer Foundation, this research approach is now the core of an extensive research program in the field of degenerative and inflammatory diseases of the nervous system.
„Simplified diagnostics through labeling (visualization) of amyloid and tau deposits“
The aggregates of amyloid β and tau protein are the hallmarks of Alzheimer’s disease. The prevention or dissolution of these protein aggregates is being investigated in clinical trials. The therapeutic success of such studies can currently only be determined by monitoring the cognitive performance of patients, as the definitive diagnosis of Alzheimer’s disease is made by post-mortem histological diagnosis of brain tissue. The lack of diagnostics of a relevant biomarker in living patients results in high case numbers and study durations of several years and thus hinders the development of therapies. The aim of the project funded by the Hans-und-Ilse-Breuer-Stiftung was the rational development of molecular probes for these amyloid β and tau protein aggregates for the examination of the retina in Alzheimer’s disease. The molecular probes to be developed had to have certain physicochemical properties that enable sufficient fluorescence diagnostics on the eye or on the olfactory epithelium with a low signal-to-noise ratio. Furthermore, these probes must exhibit selectivity to Alzheimer’s-associated protein aggregates but not bind to similar aggregates of other proteins in order to ensure the necessary diagnostic differentiation. Using the structure-ligand affinity relationships of amyloid β- and tau-ligands, new fluorophores were synthesized from privileged compound classes that bind to Aβ and tau-PHF, respectively. These fluorescent samples were evaluated histologically against established immunohistochemical methods on brain tissue from Alzheimer’s patients and then analyzed in cell-free assays for protein affinity and their fluorescence properties in the presence of the target proteins. In parallel assays, the cellularity, localization and toxicity of the substances were analyzed. In the end, two substances were identified that exhibit brain permeability in the mouse model and mark amyloid deposits. With one of these substances, these deposits could also be visualized in vivo (mouse model). The evaluation of the dyes as markers for protein deposits in the human olfactory epithelium, which enable simplified diagnostics, is ongoing.
„New and internationally used molecular classification of frontotemporal dementia“
Frontotemporal dementia (FTD) is an incurable disease that is the second most common form of dementia in patients under the age of 65 after Alzheimer’s dementia. It is characterized by a severe change in personality and impairment of social behaviour caused by cell death, primarily in the frontal and temporal areas of the brain. Amytrophic lateral sclerosis (ALS) is the most common neurodegenerative disease of the motor nervous system and is primarily associated with muscle weakness and even respiratory paralysis. At first glance, the two diseases seem to have little in common, except that both diseases lead to pathological protein clumps (so-called inclusion bodies) in nerve cells. However, with the discovery of the RNA-binding proteins TDP-43 and FUS as clumping proteins in the inclusion bodies in both FTD and ALS, our understanding of the causes and development of FTD and ALS has changed dramatically since 2006. This work has laid the foundation stone for the realization that FTD and ALS are variants of a clinicopathological spectrum of diseases that share the same underlying pathomechanism, namely a disruption of RNA metabolism (Neumann et al. Science 2006; Neumann et al. Brain 2009).
With the support of the Breuer Foundation, Prof. Neumann and her team were able to further decipher the composition of these inclusion bodies and add TAF15, EWS and transportin to the list of pathogenic proteins (Neumann et al. Acta Neuropathol 2012). Interestingly, despite the similarities mentioned above, important differences in the composition of the inclusion bodies between ALS and FTD were also found, which are of crucial importance for further elucidating the causes of protein clumping (Rademakers et al. Nat Rev Neurol 2012, Neumann Rev Neurol 2013). Furthermore, they were able to characterize the consequences of certain mutations in the FUS or C9orf72 gene in the development of ALS and FTD (Waibel et al. Eur J Neurol 2012, Mackenzie et al, Acta Neuropathol 2013). In addition to these findings, which have led to a new and internationally used molecular classification of FTD and ALS, the work also provided the basis for the development of new FTD/ALS model systems. Such projects are very long-term and costly, so the prize money from the Breuer Foundation was also essential for the generation of new genetically modified mouse lines for TDP-43 and FUS in my laboratory. These models now allow Prof. Neumann’s team to study the functions of these proteins specifically in the brain in order to gain further insights into the disease mechanisms of FTD and ALS.
„Functional characterization of micro RNA sequence variants“
Alzheimer’s disease (AD) is the most common form of dementia in the population. Certain changes in the DNA sequence of affected patients can either trigger AD (so-called „disease-causing mutations“, very rare) or increase the risk (so-called „genetic risk factors“, common). The biochemical mode of action of genetic risk factors is often much more difficult to determine than that of mutations and has not yet been sufficiently clarified for the vast majority of variants. The overall aim of our project, funded by the Hans and Ilse Breuer Foundation, was to investigate the possible connection between established genetic risk factors of AD and the function of so-called micro-RNAs (miRNAs). MiRNAs are small RNA molecules that bind to so-called messenger RNA (mRNA) molecules and can thus influence the amount of production of the proteins (= proteins) encoded by the mRNAs. To investigate this goal, Prof. Bertram and his team used a multi-faceted study design combining „in silico“ (i.e. computer-based) with „in vitro“ (i.e. laboratory-based) methods. In total, they analyzed 22 different AD-associated common DNA variants to determine whether they interfere with the biochemical binding of miRNA to mRNA. Their silico predictions highlighted eight DNA variants, which they subsequently investigated further in the laboratory by applying so-called luciferase reporter experiments and miRNA-specific expression assays on human brain samples.
The results showed that DNA variants in the MS4A6A, FERMT2 and NUP160 genes in particular could influence the binding of miRNA to mRNA and thus protein synthesis. The results of these experiments were presented at the Alzheimer’s Association International Conference (AAIC) in Boston in 2013. In another experiment, in which Prof. Bertram analyzed genome-wide association data of human memory function, he was able to show that miRNA-138 is a potential regulator of memory function in humans (Schröder et al, 2014). Since then, his research group has intensified its activity in the field of miRNA research and has recently published several independent papers in this area (e.g. Schulz et al, 2018; Wohlers et al, 2018, Takousis et al, 2019), which would not have been possible without the preliminary work carried out as part of the Breuer project.
„Improved understanding of the biological role of the alpha secretase ADAM10“
Proteases are specialized enzymes that can cut other proteins in a targeted or random manner. Of the approximately 600 proteases found in our body, some are also responsible for the formation of amyloid peptides, which are partly responsible for the death of neurons and are increasingly produced in Alzheimer’s disease. The gamma- and beta-secretase are directly involved in this proteolytic process, whereby the alpha-secretase counteracts the cutting out of the harmful amyloid peptide. The research group led by Prof. Paul Saftig at Kiel University has concentrated on elucidating the function of this alpha-secretase in a series of studies, particularly with genetically modified mice. ADAM10 was identified as an in vivo important alpha secretase that cleaves the amyloid precursor protein. The importance of this enzyme, which belongs to the metalloprotease family, for the development of the mouse brain but also for the function of the adult brain has been demonstrated by various experimental approaches. A loss of this protease leads to changes in the structure and function of nerve contacts (synapses) and a reduction in learning ability. Further work has also shown that ADAM10 can cut a whole range of other surface proteins on nerve cells and thus modulate their function. From a potential therapeutic point of view, this means that ADAM10 is a very interesting target for the treatment of Alzheimer’s disease, but due to its diverse functions, careful consideration must be given to how to influence the activity of this protease. In this context, it is also interesting to note that the working group found that the cellular distribution and stability of ADAM10 is regulated by so-called tetraspanin proteins. It was also found that ADAM10 is of crucial importance in prion disease.
The work in Prof. Saftig’s research group funded by the Breuer Foundation prize money thus laid the foundation for an improved understanding of the biological role of the alpha secretase ADAM10 involved in Alzheimer’s disease.
„New research approaches to slow down the process of amyloid deposits“
Aβ plaques and a-synuclein-containing Lewy bodies are the main neuropathological hallmarks of Alzheimer’s and Parkinson’s disease, respectively. In 50% of Alzheimer’s patients, these two protein deposits occur simultaneously and in vitro studies also suggest a direct interaction between Aβ and α-synuclein. The significance of this interaction for plaque formation was to be investigated as part of the Hans and Ilse Breuer Prize. Interestingly, the double-transgenic APPPS1xa-synA30P mouse model of Lewy body dementia showed 50% fewer Aβ plaques and increased Aβ levels in the cerebrospinal fluid compared to its littermates. Based on this, this „inhibition hypothesis“ was investigated using intracerebral injections, transplantation experiments and in vitro aggregation assays. In each of these methodologically very different experiments, α-synuclein inhibited Aβ deposition. Further investigations suggested that although α-synuclein inhibits Aβ aggregation, it also leads to increased reduction of dendritic spinous processes due to the accumulation of toxic Aβ intermediates (Bachhuber et al 2015). Furthermore, Prof. Meyer-Lühmann’s team used in vivo 2-photon microscopy to address various questions. For example, they were able to describe the growth process of Aβ plaques in more detail over several months (McCarter et al. 2013) and to investigate the positive effects of a γ-secretase inhibitor on plaque formation and the plaque-associated dendritic spinous processes (Liebscher et al. 2014). Their results open up new research approaches to slow down or even stop the harmful process of amyloid deposition and the associated pathological changes of both morphological and functional nature.
„Start of first clinical trial for testing an epigenetically active drug“
In diseases such as Alzheimer’s dementia, more and more nerve cells in the brain die over time. It has been shown that mechanisms that influence the activation of genes play a role. The activity of genes in brain cells is controlled by so-called „epigenetic“ processes, which ensure that certain areas of the human genome can be read while others remain silenced. If this sensitive balance is disturbed, dementia can occur. The study of epigenetic processes in Alzheimer’s was still in its infancy in 2009.
With the support of the Hans and Ilse Breuer Foundation, Prof. Fischer’s team has succeeded in gaining decisive insights into the epigenetics of dementia and developing promising new therapeutic approaches that have shown outstanding results in the model system. As a result of this research, the world’s first clinical trial is now taking place in which an epigenetically active drug is being tested on Alzheimer’s patients (https://clinicaltrials.gov/ct2/show/NCT03056495).
„New research approaches for glial cells as a source for the replacement of dead nerve cells“
Ten years ago, I received a €100,000 research award from the Breuer Foundation, which enabled me to expand the research I had just started on a new source of stem cells in the brain. I am a developmental biologist, and I became interested in glial cells in the adult brain after we discovered that the neural stem cells during brain development are also glial cells. This gave rise to the idea that some of the glial cells that respond to injury or amyloid plaques in the adult brain might also have stem cell properties, and thus could provide a new source of replacement for dead neurons. The Breuer Prize was a very important help to me in pursuing this innovative thesis and identifying molecular mechanisms that promote the stem cell properties of reactive glial cells (Sirko et al., Cell Stem Cell 2013). Such projects are often long-term, and in particular require high costs for transgenic mouse lines, so the Breuer Prize was crucial to be able to carry out this research. In the meantime, Prof. Götz and her team have identified further factors that help them to stimulate these glial cells to form nerve cells (Gascón et al., Cell Stem Cell 2016) in order to be able to replace dead nerve cells from local cells. Now they need to be able to actually form the right subtypes of nerve cells so that the function of the brain can be properly repaired (Falkner et al., Nature 2016; Barker et al., Nature 2018).
„Confirmation that the amyloid precursor protein (APP) has essential functions for communication between nerve cells“
The amyloid precursor protein APP plays a key role in the development of Alzheimer’s dementia. The normal cell biological and physiological functions of APP and its cleavage products were previously largely unknown. APP is produced in almost all cells of the brain, especially in regions that are important for memory formation. Prof. Müller’s team investigated the role APP plays in healthy organisms for the development and function of the nervous system. To this end, genetically modified mouse models were created in which the genetic information for APP was destroyed, thus preventing APP production. An analysis of these mice allowed important conclusions to be drawn about the normal function of the APP protein in the organism. With the help of the Breuer Prize, Prof. Müller and her team were able to show that APP, and in particular the APP cleavage product APPsa, has essential functions for communication between nerve cells. For example, mice with an inactivated APP gene have fewer synapses, the communication sites between nerve cells, and significantly poorer learning ability in cognitive tests. Further experiments provided evidence that APPsα acts as a signaling molecule on the synaptic contacts of nerve cells that use acetylcholine as a messenger substance. The APPsα protein fragment stimulates signal transmission through the acetylcholine receptors and increases their natural responsiveness. APPsa is therefore also of great therapeutic interest, as lower quantities of APPsa are produced in the brains of Alzheimer’s patients.
One possible therapeutic approach would therefore be to induce the production of APPsa in the patient’s brain or to introduce APPsa by means of gene therapy.
„Role of the tau protein in the development of Alzheimer’s disease“
Alzheimer’s disease is characterized by 2 deposits of proteins in the brain, the „beta-amyloid“ and the „tau protein“. The aim of Prof. Mandelkow’s research is to prevent or reverse the clumping of these proteins. At the time of the research award (2007), work on amyloid was already well advanced, while far less was known about the effect of tau in the brain.
The team of Prof. Mandelkow had already investigated the properties of the isolated tau protein through preliminary work since 1990 and had found reasons why it clumps together. However, there was still a lack of experience as to how the pathology of the tau protein develops in brain tissue. So-called „transgenic mice“, which are genetically modified to produce the human tau protein, are suitable for this purpose in medical research. Such experiments are time-consuming and expensive, but they give a fairly realistic picture of the disease in humans and make it possible to test therapeutic approaches. At the time, Prof. Mandelkow had set out to investigate a complicated „mouse model“ of Alzheimer’s disease. It should enable her team to switch the tau protein on and off again in order to observe the beginning and end of the pathology. The tau protein should appear in the brain in two variants, either with rapid clumping or without clumping. This was to investigate whether and how the clumping causes the disease. Thirdly, the formation of the tau protein in the brain was to be observed from the outside using a light signal via a dye that also makes fireflies visible (luciferin). This risky research plan succeeded with the help of the research prize.
The results showed: (1) The clumping of the tau protein is responsible for the destruction of the brain cells, soluble tau protein does not do this. (2) When tau is „switched on“, the gradual loss of memory begins. But the big surprise was: when the tau is „switched off“ again, the damage largely heals. This means that the disease process is – in principle – reversible and should therefore be curable. The research confirmed that tau and beta-amyloid are both involved in the disease process and led to new research approaches. The current main goal is to transfer the findings on the brain of mice to the brain of humans and to find suitable (and safe) active substances.
„New starting points for research into the function of γ-secretase“
According to current knowledge, Alzheimer’s disease is caused by protein clumps called β-amyloid (Aβ) in the brain. Aβ is cut out of a larger protein by two scissor-like enzymes. Mr. Steiner is researching the exact function of one of these two molecular scissors, γ-secretase, to find out how to block it. Effective blocking of γ-secretase prevents the formation of Aβ and should therefore, in principle, be able to delay or even completely stop Alzheimer’s disease. Through his research, Mr. Steiner has set himself the goal of creating the basis for the development of selective γ-secretase inhibitors that prevent the formation of Aβ without affecting the cleavage of other important proteins.
With the help of the 2006 Alzheimer’s Research Prize from the Hans and Ilse Breuer Foundation, Mr. Steiner was able to gain important insights into the molecular structure of g-secretase, its active center, and the mode of action of selectively acting, special inhibitors of the enzyme, the g-secretase modulators. The results of this work formed important starting points for further research projects by Mr. Steiner on the function of γ-secretase.