Cells of the human body do not act as isolated entities of unorganized matter. Even though cells cannot be visualized with the naked eye, they are capable of stowing away about 2 meters of genetic material and regulate hundreds of processes simultaneously with immaculate speed and precision. At a tiny micrometer level, they are highly organized, with separate functional entities called organelles, and they even contain a refined ‘waste disposal system’. Cells don’t live in isolation. Instead, they are highly interactive and communicate intensively and continuously with neighboring cells, and even with cells as remote as a meter away from them. Apart from only communicating, cells also regulate their responses to these signals in an orchestrated manner. In my team we share the excitement of the prospect of understanding the intricacies of these highly evolved cellular communication systems. The Cellular Signaling and Communication Lab is headed by associate professor Kerensa Broersen.
We aim at revealing the manner in which cells communicate at their most fundamental level: with their similar neighbors, with other cell types in the same tissue and with cells from different tissues.
To achieve all this, we make use of classical biochemical, molecular biology, and cell biological read-outs combined with highly advanced and refined engineering tools to make our observations. These include stem cell derived organoids, chip technology and microfluidics.
Our starting point is the brain which we view as an awesome piece of complex wired engineering and questions we typically address include:
- How does the microbiome, even though at a distance of close to one meter, communicate with the brain such that alteration of microbiome composition, as observed in a range of pathologies, can affect brain functioning?
- How are potentially neuropathological proteins processed and secreted?
- How are inflammasome signaling and neuronal degradation related?
1. Microbiome-brain communication – the development of a microbiome-gut-brain axis on a chip
Since the start of the Netherlands Organ-on-Chip Initiative, or NOCI (https://noci-organ-on-chip.nl/), we started pursuing the challenging question how the gut, or actually the complex microbiome consisting of millions of interconnecting bacterial species, communicates with the brain. Embedded within the NOCI consortium as well as the stem cell oriented lab Applied Stem cell Technologies, and our fruitful collaboration with the BIOS group at the UT (https://www.utwente.nl/en/eemcs/bios/) combined with our own knowledge and expertise we reasoned we have all the tools available to address this question. Nevertheless, this proved to be an adventurous ride ever since the start during which we are challenged to the tips of our toes on diverse topics such as co-culturing of anaerobic bacteria with oxygen-requiring cells of the gut, growing a vagal nerve in a dish, gene-editing mucin, and measurement of brain activity.
We decided to approach this challenge by building a gut-brain axis on a microfluidic chip (see figure 1) to comply with shear flow requirement of intestinal cells. Once we obtain a validated working model that recapitulates well the typical features characterizing microbiome-gut-brain coexistence, we strive to understand better the molecular mechanisms of brain gut interaction and to extend our observations to investigate microbiome related gut brain abnormalities and pathologies, such as schizophrenia, autism, Parkinson’s disease and Alzheimer’s disease.
Figure 1. Left: microfluidic chip, middle: set-up to probe bidirectional communication at gut-brain axis level, right, CDX2-positive IPSC-derived intestinal organoids.
For more information on this project, please contact:
2. Processing and secretion of potentially neuropathological proteins
The cell is challenged on a daily basis by dyshomeostasis of the many complex and interacting processes that take place in its tiny environment. The cell has a surprising number of rescuing mechanisms available to maintain and restore homeostasis. One of the proteins that is crucial to the cellular organization but can cause absolute mayhem when dysregulated is tau. One of the consequences is that tau can be found as intracellular sediments in the brain neurons of for example Alzheimer’s disease patients. We set out, in collaboration with Randy Schekman at the University of California – Berkeley in the US, to explore how tau levels are regulated in the cell by studying some of the mechanisms responsible for maintaining tau levels within strict values. A cell is capable of eliminating unwanted or excess components by either spewing them out or by activating an internal waste disposal unit called the autophagolysosome. We are in the process of determining the relevance of either of these processes in regulating tau levels and preliminary data showed that upregulation of the proteins USP19 and DNAJC5, involved in a process termed Misfolding Associated Protein Secretion (MAPS), induces secretion of tau showing that MAPS is involved in intracellular tau level maintenance. We further found that knock-out of Vesicle Associated Membrane Proteins, or VAMPS, upregulates MAPS-mediated tau secretion even further. We are now in the process of determining how these two processes are regulated and compete to maintain tau levels within healthy limits.
Figure 2. Upregulation of USP19 and DNAJC5, involved in Misfolding Associated Protein Secretion, induces secretion of tau from tau overexpressing neuroblastoma SH-SY5Y cells.
3. Relation between inflammasome signaling and neuronal degradation
Weirdly enough, when neurons start degenerating, invariably an inflammatory component is simultaneously seen at work. We decided to investigate how neurodegeneration and neuroinflammation are related by studying the interactions between immune cells and neurons in the brain. We figured out that the assembly of the microglial NLRP3 inflammasome complex is required to induce neuronal dysfunction and that the presence of amyloid beta peptide, a protein that sediments extracellularly in the brain in Alzheimer’s disease, is required to induce asynchronous firing patterns of neurons in the brain.
Are you as excited as we are to delve into the inner fundamentals and workings of cells? Contact us for student projects.
See personal profile pages for full list.
Cioffi F, Adam RHI, Broersen K (2019). Molecular mechanisms and genetics of oxidative stress in Alzheimer's disease. J Alzheimers Dis. Nov 11. doi: 10.3233/JAD-190863.
Hubin E, Verghese PB, van Nuland N, Broersen K (2019). Apolipoprotein E associated with reconstituted high-density lipoprotein-like particles is protected from aggregation. FEBS Lett. 593(11):1144-1153. doi: 10.1002/1873-3468.13428.
Broersen K, Ruiperez V, Davletov B (2018). Structural and aggregation properties of alpha-synuclein linked to phospholipase A2 action. Protein Pept Lett. 25(4):368-378. doi: 10.2174/0929866525666180326120052.
Teodorowicz M, Perdijk O, Verhoek I, Govers C, Savelkoul HF, Tang Y, Wichers H, Broersen K (2017). Optimized Triton X-114 assisted lipopolysaccharide (LPS) removal method reveals the immunomodulatory effect of food proteins. PLoS One. 12(3):e0173778. doi: 10.1371/journal.pone.0173778. eCollection 2017.
Hubin E, Cioffi F, Rozenski J, van Nuland NA, Broersen K (2016). Characterization of insulin-degrading enzyme-mediated cleavage of Aβ in distinct aggregation states. Biochim Biophys Acta. 1860(6):1281-90. doi: 10.1016/j.bbagen.2016.03.010.
Hubin E, Deroo S, Schierle GK, Kaminski C, Serpell L, Subramaniam V, van Nuland N, Broersen K, Raussens V, Sarroukh R (2015). Two distinct β-sheet structures in Italian-mutant amyloid-beta fibrils: a potential link to different clinical phenotypes. Cell Mol Life Sci. 72(24):4899-913. doi: 10.1007/s00018-015-1983-2.
Hubin E, van Nuland NA, Broersen K, Pauwels K (2014). Transient dynamics of Aβ contribute to toxicity in Alzheimer's disease. Cell Mol Life Sci. 71(18):3507-21. doi: 10.1007/s00018-014-1634-z.
Vandersteen A, Masman MF, De Baets G, Jonckheere W, van der Werf K, Marrink SJ, Rozenski J, Benilova I, De Strooper B, Subramaniam V, Schymkowitz J, Rousseau F, Broersen K (2012). Molecular plasticity regulates oligomerization and cytotoxicity of the multipeptide-length amyloid-β peptide pool. J Biol Chem. 287(44):36732-43. doi: 10.1074/jbc.M112.394635.
Chávez-Gutiérrez L, Bammens L, Benilova I, Vandersteen A, Benurwar M, Borgers M, Lismont S, Zhou L, Van Cleynenbreugel S, Esselmann H, Wiltfang J, Serneels L, Karran E, Gijsen H, Schymkowitz J, Rousseau F, Broersen K, De Strooper B (2012). The mechanism of γ-secretase dysfunction in familial Alzheimer disease. EMBO J. 31(10):2261-74. doi: 10.1038/emboj.2012.79.
Pauwels K, Williams TL, Morris KL, Jonckheere W, Vandersteen A, Kelly G, Schymkowitz J, Rousseau F, Pastore A, Serpell LC, Broersen K (2012). Structural basis for increased toxicity of pathological aβ42:aβ40 ratios in Alzheimer disease. J Biol Chem. 287(8):5650-60. doi: 10.1074/jbc.M111.264473.
Kuperstein I, Broersen K, Benilova I, Rozenski J, Jonckheere W, Debulpaep M, Vandersteen A, Segers-Nolten I, Van Der Werf K, Subramaniam V, Braeken D, Callewaert G, Bartic C, D'Hooge R, Martins IC, Rousseau F, Schymkowitz J, De Strooper B (2010). Neurotoxicity of Alzheimer's disease Aβ peptides is induced by small changes in the Aβ42 to Aβ40 ratio. EMBO J. 29(19):3408-20. doi: 10.1038/emboj.2010.211.
Broersen K, van den Brink D, Fraser G, Goedert M, Davletov B (2006). Alpha-synuclein adopts an alpha-helical conformation in the presence of polyunsaturated fatty acids to hinder micelle formation. Biochemistry. 45(51):15610-6. doi: 10.1021/bi061743l