News

The Max Planck Society has succeeded in recruiting two renowned scientists. Kikuë Tachibana and John Briggs will now be conducting their research at the MPI of Biochemistry in Martinsried.

The Max Planck Institute of Biochemistry (MPIB) expands its scientific expertise with two new directors: Kikuë Tachibana and John Briggs. Molecular geneticist Kikuë Tachibana has moved with her research group from Vienna to Martinsried. Since August 1, she heads the research department "Totipotency". Together with her team, she studies cells that have the ability to develop into whole organisms. In parallel, structural biologist John Briggs starts his work at the institute. He has moved from Cambridge, UK, to Martinsried and heads the department "Cell and Virus Structure" since September 1. John Briggs and his team will study the structures of viruses as well as fundamental molecular cellular mechanisms.

Martinsried - since August 1 and September 1, respectively, Dr. Kikuë Tachibana and Dr. John Briggs are new full-time directors at MPIB. With the two new researchers, the institute now has nine directors, sharpening the research profile of the Max Planck Society. The new director Tachibana says: “I am delighted to have the opportunity offered by the Max Planck Society to devote our research to uncover the molecular mechanisms underlying the start of life. I am looking forward to collaborate scientifically with my colleagues and to work together for developing the Martinsried campus." John Briggs explains, "Structural biology and method development in microscopy have a long tradition in Martinsried. My team and I, together with our new colleagues in Martinsried, are looking forward to finding out more about how viruses assemble and how they function." 

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New mouse type reveals when neurons fail to cope with misfolded proteins.

Proteins are the "tools" of our cells – they are essential to all vital tasks. However, they are only able to do their jobs if they fold correctly and adopt their respective, very specific 3D structure. To ensure that nothing goes wrong with the folding process, it is strictly monitored in the cell. The consequences of a flawed quality control can be seen, for example, in the deposition of misfolded proteins in neurodegenerative diseases such as Alzheimer's. Researchers at the Max Planck Institutes of Neurobiology and of Biochemistry have now developed a mouse line that makes the state of protein balance visible in the mammalian brain for the first time. In this way, the processes of protein quality control can now be studied in healthy and diseased neurons in more detail.

Proteins fulfill all important tasks in our body: They transport substances, protect against diseases, support the cell and catalyze chemical reactions – to name just a few. With the building instructions in our genetic code, every protein can be produced as a long chain of amino acids. However, that's not the end of the story: in order to perform their vital functions, proteins have to fold into complex 3D structures.

Each cell contains a whole machinery that helps proteins to fold, corrects folding errors and discards misfolded proteins. As a kind of quality control, the system thus contributes to proteostasis – the controlled function of all proteins.

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Merino-Salomón, A., Babl, L., and Schwille, P.
Curr Opin Cell Biol, 2021, 72, 106-115, online ahead of print.
doi: 10.1016/j.ceb.2021.07.001

Self-organized protein patterns: The MinCDE and ParABS systems

Self-organized protein patterns are of tremendous importance for biological decision-making processes. Protein patterns have been shown to identify the site of future cell division, establish cell polarity, and organize faithful DNA segregation. Intriguingly, several key concepts of pattern formation and regulation apply to a variety of different protein systems. Herein, we explore recent advances in the understanding of two prokaryotic pattern-forming systems: the MinCDE system, positioning the FtsZ ring precisely at the midcell, and the ParABS system, distributing newly synthesized DNA along with the cell. Despite differences in biological functionality, these two systems have remarkably similar molecular components, mechanisms, and strategies to achieve biological robustness.

 


 

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Murali Mahadevan, H., Hashemiaghdam, A., Ashrafi, G., and Harbauer, A.B.
Adv Biol (Weinh), 2021, e2100663, online ahead of print.
doi: 10.1002/adbi.202100663

Mitochondria in Neuronal Health: From Energy Metabolism to Parkinson's Disease

Mitochondria are the main suppliers of neuronal adenosine triphosphate and play a critical role in brain energy metabolism. Mitochondria also serve as Ca2+ sinks and anabolic factories and are therefore essential for neuronal function and survival. Dysregulation of neuronal bioenergetics is increasingly implicated in neurodegenerative disorders, particularly Parkinson's disease. This review describes the role of mitochondria in energy metabolism under resting conditions and during synaptic transmission, and presents evidence for the contribution of neuronal mitochondrial dysfunction to Parkinson's disease.

 


 

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Frauenstein, A., Ebner, S., Hansen, F.M., Sinha, A., Phulphagar, K., Swatek, K., Hornburg, D., Mann, M., and Meissner, F.
(IMPRS-LS students and alumni students are in bold)
Mol Syst Biol, 2021, 17, e10125.
doi: 10.15252/msb.202010125

Identification of covalent modifications regulating immune signaling complex composition and phenotype

Cells signal through rearrangements of protein communities governed by covalent modifications and reversible interactions of distinct sets of proteins. A method that identifies those post-transcriptional modifications regulating signaling complex composition and functional phenotypes in one experimental setup would facilitate an efficient identification of novel molecular signaling checkpoints. Here, we devised modifications, interactions and phenotypes by affinity purification mass spectrometry (MIP-APMS), comprising the streamlined cloning and transduction of tagged proteins into functionalized reporter cells as well as affinity chromatography, followed by MS-based quantification. We report the time-resolved interplay of more than 50 previously undescribed modification and hundreds of protein-protein interactions of 19 immune protein complexes in monocytes. Validation of interdependencies between covalent, reversible, and functional protein complex regulations by knockout or site-specific mutation revealed ISGylation and phosphorylation of TRAF2 as well as ARHGEF18 interaction in Toll-like receptor 2 signaling. Moreover, we identify distinct mechanisms of action for small molecule inhibitors of p38 (MAPK14). Our method provides a fast and cost-effective pipeline for the molecular interrogation of protein communities in diverse biological systems and primary cells.

 


 

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Martinelli, S., Anderzhanova, E.A., Bajaj, T., Wiechmann, S., Dethloff, F., Weckmann, K., Heinz, D.E., Ebert, T., Hartmann, J., Geiger, T.M., et al.
(IMPRS-LS students and alumni students are in bold)
Nat Commun, 2021, 12, 4643.
doi: 10.1038/s41467-021-24810-5

Stress-primed secretory autophagy promotes extracellular BDNF maturation by enhancing MMP9 secretion

The stress response is an essential mechanism for maintaining homeostasis, and its disruption is implicated in several psychiatric disorders. On the cellular level, stress activates, among other mechanisms, autophagy that regulates homeostasis through protein degradation and recycling. Secretory autophagy is a recently described pathway in which autophagosomes fuse with the plasma membrane rather than with lysosomes. Here, we demonstrate that glucocorticoid-mediated stress enhances secretory autophagy via the stress-responsive co-chaperone FK506-binding protein 51. We identify the matrix metalloproteinase 9 (MMP9) as one of the proteins secreted in response to stress. Using cellular assays and in vivo microdialysis, we further find that stress-enhanced MMP9 secretion increases the cleavage of pro-brain-derived neurotrophic factor (proBDNF) to its mature form (mBDNF). BDNF is essential for adult synaptic plasticity and its pathway is associated with major depression and posttraumatic stress disorder. These findings unravel a cellular stress adaptation mechanism that bears the potential of opening avenues for the understanding of the pathophysiology of stress-related disorders.

 


 

JSPACongratulations!

 

The Junior Scientists' Publication Award Committee of the Max Planck Institute of Biochemistry has selected this year's award winners.

22 awardees with 19 publications have been awarded the JSPA this year. The celebration took place online and some of the young scientists presented their exciting research results during the minisyposium.

We are very proud that 10 out of 22 awardees are or have been IMPRS-LS graduate students. We are very proud of you!

 


 

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Amaro, D., Ferreiro, D.N., Grothe, B., and Pecka, M.
Curr Biol, 2021, online ahead of print.
doi: 10.1016/j.cub.2021.06.025

Source identity shapes spatial preference in primary auditory cortex during active navigation

Information about the position of sensory objects and identifying their concurrent behavioral relevance is vital to navigate the environment. In the auditory system, spatial information is computed in the brain based on the position of the sound source relative to the observer and thus assumed to be egocentric throughout the auditory pathway. This assumption is largely based on studies conducted in either anesthetized or head-fixed and passively listening animals, thus lacking self-motion and selective listening. Yet these factors are fundamental components of natural sensing that may crucially impact the nature of spatial coding and sensory object representation. How individual objects are neuronally represented during unrestricted self-motion and active sensing remains mostly unexplored. Here, we trained gerbils on a behavioral foraging paradigm that required localization and identification of sound sources during free navigation. Chronic tetrode recordings in primary auditory cortex during task performance revealed previously unreported sensory object representations. Strikingly, the egocentric angle preference of the majority of spatially sensitive neurons changed significantly depending on the task-specific identity (outcome association) of the sound source. Spatial tuning also exhibited large temporal complexity. Moreover, we encountered egocentrically untuned neurons whose response magnitude differed between source identities. Using a neural network decoder, we show that, together, these neuronal response ensembles provide spatiotemporally co-existent information about both the egocentric location and the identity of individual sensory objects during self-motion, revealing a novel cortical computation principle for naturalistic sensing.

 


 

graduation

Congratulations on your PhD!

 

Andreas-David Brunner


True single-cell proteomics using advanced ion mobility mass spectrometry


RG: Matthias Mann

 


 

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Sinitcyn, P.#, Hamzeiy, H.#, Salinas Soto, F., Itzhak, D., McCarthy, F., Wichmann, C., Steger, M., Ohmayer, U., Distler, U., Kaspar-Schoenefeld, S., Prianichnikov, N., Yılmaz, Ş., Rudolph, J.D., Tenzer, S., Perez-Riverol, Y., Nagaraj, N., Humphrey, S.J., and Cox, J.
#equal contribution
Nat Biotechnol, 2021, online ahead of print.
doi: 10.1038/s41587-021-00968-7

MaxDIA enables library-based and library-free data-independent acquisition proteomics

MaxDIA is a software platform for analyzing data-independent acquisition (DIA) proteomics data within the MaxQuant software environment. Using spectral libraries, MaxDIA achieves deep proteome coverage with substantially better coefficients of variation in protein quantification than other software. MaxDIA is equipped with accurate false discovery rate (FDR) estimates on both library-to-DIA match and protein levels, including when using whole-proteome predicted spectral libraries. This is the foundation of discovery DIA-hypothesis-free analysis of DIA samples without library and with reliable FDR control. MaxDIA performs three- or four-dimensional feature detection of fragment data, and scoring of matches is augmented by machine learning on the features of an identification. MaxDIA's bootstrap DIA workflow performs multiple rounds of matching with increasing quality of recalibration and stringency of matching to the library. Combining MaxDIA with two new technologies-BoxCar acquisition and trapped ion mobility spectrometry-both lead to deep and accurate proteome quantification.