Nico Strohmeyer

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Strohmeyer

First Name

Nico

ORCID

0000-0002-5985-9800

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Publications 1 - 10 of 30

Rheology of rounded mammalian cells over continuous high-frequencies
Fläschner, Gotthold Viktor; Roman, Cosmin I.; Strohmeyer, Nico; et al. (2021)
Nature Communications
Understanding the viscoelastic properties of living cells and their relation to cell state and morphology remains challenging. Low-frequency mechanical perturbations have contributed considerably to the understanding, yet higher frequencies promise to elucidate the link between cellular and molecular properties, such as polymer relaxation and monomer reaction kinetics. Here, we introduce an assay, that uses an actuated microcantilever to confine a single, rounded cell on a second microcantilever, which measures the cell mechanical response across a continuous frequency range ≈ 1–40 kHz. Cell mass measurements and optical microscopy are co-implemented. The fast, high-frequency measurements are applied to rheologically monitor cellular stiffening. We find that the rheology of rounded HeLa cells obeys a cytoskeleton-dependent power-law, similar to spread cells. Cell size and viscoelasticity are uncorrelated, which contrasts an assumption based on the Laplace law. Together with the presented theory of mechanical de-embedding, our assay is generally applicable to other rheological experiments.
Engineered biomimetic fibrillar fibronectin matrices trigger long-term fibroblast decisions within seconds of adhesion
Strohmeyer, Nico (2023)
Increasing throughput of AFM-based single cell adhesion measurements through multisubstrate surfaces
Miao, Yu; Strohmeyer, Nico; Wang, Jinghe; et al. (2015)
Beilstein Journal of Nanotechnology
Mammalian cells regulate adhesion by expressing and regulating a diverse array of cell adhesion molecules on their cell surfaces. Since different cell types express distinct sets of cell adhesion molecules, substrate-specific adhesion is cell type- and condition-dependent. Single-cell force spectroscopy is used to quantify the contribution of cell adhesion molecules to adhesion of cells to specific substrates at both the cell and single molecule level. However, the low throughput of single-cell adhesion experiments greatly limits the number of substrates that can be examined. In order to overcome this limitation, segmented polydimethylsiloxane (PDMS) masks were developed, allowing the measurement of cell adhesion to multiple substrates. To verify the utility of the masks, the adhesion of four different cell lines, HeLa (Kyoto), prostate cancer (PC), mouse kidney fibroblast and MDCK, to three extracellular matrix proteins, fibronectin, collagen I and laminin 332, was examined. The adhesion of each cell line to different matrix proteins was found to be distinct; no two cell lines adhered equally to each of the proteins. The PDMS masks improved the throughput limitation of single-cell force spectroscopy and allowed for experiments that previously were not feasible. Since the masks are economical and versatile, they can aid in the improvement of various assays.
Talin and kindlin use integrin tail allostery and direct binding to activate integrins
Aretz, Jonas; Aziz, Masood; Strohmeyer, Nico; et al. (2023)
Nature Structural & Molecular Biology
Integrin affinity regulation, also termed integrin activation, is essential for metazoan life. Although talin and kindlin binding to the β-integrin cytoplasmic tail is indispensable for integrin activation, it is unknown how they achieve this function. By combining NMR, biochemistry and cell biology techniques, we found that talin and kindlin binding to the β-tail can induce a conformational change that increases talin affinity and decreases kindlin affinity toward it. We also discovered that this asymmetric affinity regulation is accompanied by a direct interaction between talin and kindlin, which promotes simultaneous binding of talin and kindlin to β-tails. Disrupting allosteric communication between the β-tail-binding sites of talin and kindlin or their direct interaction in cells severely compromised integrin functions. These data show how talin and kindlin cooperate to generate a small but critical population of ternary talin-β-integrin-kindlin complexes with high talin-integrin affinity and high dynamics.
αV-class integrins exert dual roles on α5β1 integrins to strengthen adhesion to fibronectin
Bharadwaj, Mitasha; Strohmeyer, Nico; Colo, Georgina P.; et al. (2017)
Nature Communications
Upon binding to the extracellular matrix protein, fibronectin, αV-class and α5β1 integrins trigger the recruitment of large protein assemblies and strengthen cell adhesion. Both integrin classes have been functionally specified, however their specific roles in immediate phases of cell attachment remain uncharacterized. Here, we quantify the adhesion of αV-class and/or α5β1 integrins expressing fibroblasts initiating attachment to fibronectin (≤120 s) by single-cell force spectroscopy. Our data reveals that αV-class integrins outcompete α5β1 integrins. Once engaged, αV-class integrins signal to α5β1 integrins to establish additional adhesion sites to fibronectin, away from those formed by αV-class integrins. This crosstalk, which strengthens cell adhesion, induces α5β1 integrin clustering by RhoA/ROCK/myosin-II and Arp2/3-mediated signalling, whereas overall cell adhesion depends on formins. The dual role of both fibronectin-binding integrin classes commencing with an initial competition followed by a cooperative crosstalk appears to be a basic cellular mechanism in assembling focal adhesions to the extracellular matrix.
Compressed Cells Facilitate Adhesion Through Glycocalyx
Wang, Xiaole; Helenius, Jonne; Müller, Daniel J.; et al. (2025)
Advanced Science
Exposed to mechanical confinement, mammalian cells can establish remarkable unspecific adhesion, which is independent of integrins. How cells facilitate such adhesion remains unclear. Here, it is investigated how mammalian cells exposed to compression initiate unspecific and integrin-mediated adhesion. It is observed that with increasing compression, cells increase adhesion to collagen I or fibronectin and strengthen adhesion faster. Under low and medium compression, cells minimally increase unspecific adhesion to substrates that lack specific binding sites for cell surface receptors, such as integrins. However, under high compression, mammalian cells switch to a strong unspecific adhesion state, which significantly contributes to cell-extracellular matrix (ECM) adhesion. Thereby cells use the glycocalyx to directly facilitate strong unspecific adhesion and to enhance early integrin-mediated adhesion. The mechanistic insight of how cells unspecifically adhere to substrates under confinement opens avenues to better understand cell adhesion in development, homeostasis, disease, and in a wide range of biotechnological and medical applications in which cells are exposed to mechanical confinement.
Mammalian cells measure the extracellular matrix area and respond through switching the adhesion state
Wang, Xiaole; Wang, Pengli; Zhang, Lihang; et al. (2025)
Nature Communications
Mammalian cells adjust integrin-mediated adhesion based on the composition and structure of the extracellular matrix (ECM). However, how spatially confined ECM ligands regulate cell adhesion initiation remains unclear. Here, we investigate how cells adapt early adhesion to different ECM protein areas. Through combining microcontact printing with single-cell force spectroscopy we measure cell adhesion initiation and strengthening to defined areas of ECM proteins. HeLa cells and mouse embryonic fibroblasts gradually increase adhesion with collagen I or fibronectin area, while reaching maximum adhesion force to ECM patterns having areas above certain thresholds. On much smaller patterns, both cell types switch to a different state and considerably increase the adhesion force per ECM protein area, which they strengthen much faster. This spatially enhanced adhesion state does not require talin or kindlin, indicating a fundamentally different adhesion mechanism. Mechanotransduction seems to play integrin and cell type-specific roles in the spatially enhanced adhesion state.
Morphometry and mechanical instability at the onset of epithelial bladder cancer
Lampart, Franziska L.; Vetter, Roman; Wang, Yifan; et al. (2023)
bioRxiv
Malignancies of epithelial tissues, called carcinomas, account for the majority of cancer cases. Much cancer research has focused on genetic alterations and their relation to different carcinoma phenotypes. Besides a rewiring in the signalling networks, carcinoma progression is accompanied by mechanical changes in the epithelial cells and the extracellular matrix. Here, we reveal intricate morphologies in the basement membrane at the onset of bladder cancer, and propose that they emerge from a mechanical buckling instability upon epithelial overgrowth. Using a combination of microscopy imaging of the mouse and human bladder tissue, elasticity theory, and numerical simulations of differential growth in the bladder mucosa, we find that aberrant tissue morphologies can emerge through stiffness changes in the different mucosa layers. The resulting thickening, wrinkles and folds exhibit qualitative and quantitative similarity with imaged early papillary tumors and carcinomas in situ. Atomic force microscopy indeed reveals local stiffness changes in the pathological basement membrane. Our findings suggest a mechanical origin of the different carcinoma subtypes in the bladder, which have vastly different clinical prognosis. They might provide the basis for a new line of attack in medical carcinoma treatment and prophylaxis.
Compression force induces transient actomyosin activation and compression-time dependent stiffening in cells
Ammirati, Giulia E.M.; Nava, Michele; Kasuba, Krishna Chaitanya; et al. (2023)
Biophysical Journal
αV-class integrins identify ECM-context to license cellular mechanics and mechanotransduction within seconds
Sharma, Upnishad; Reber, Jakob; Helenius, Jonne; et al. (2025)
Molecular Biology of the Cell ~ CELL BIO 2024 Abstracts: Poster Presentations

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Nico Strohmeyer

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