Disulfide bonds reduce the toxicity of the amyloid fibrils formed by an extracellular protein

In a stable condition: Disulfide bonds stabilize folded proteins primarily by decreasing the entropic cost of folding. Such cross-links also reduce toxic aggregation by favoring the formation of highly structured amyloid fibrils (see picture). It is suggested that disulfide bonds in extracellular proteins were selected by evolutionary pressures because they decrease the propensity to form toxic aggregates. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

The laminin–keratin link shields the nucleus from mechanical deformation and signalling

The mechanical properties of the extracellular matrix dictate tissue behaviour. In epithelial tissues, laminin is a very abundant extracellular matrix component and a key supporting element. Here we show that laminin hinders the mechanoresponses of breast epithelial cells by shielding the nucleus from mechanical deformation. Coating substrates with laminin-111—unlike fibronectin or collagen I—impairs cell response to substrate rigidity and YAP nuclear localization. Blocking the laminin-specific integrin ß4 increases nuclear YAP ratios in a rigidity-dependent manner without affecting the cell forces or focal adhesions. By combining mechanical perturbations and mathematical modelling, we show that ß4 integrins establish a mechanical linkage between the substrate and keratin cytoskeleton, which stiffens the network and shields the nucleus from actomyosin-mediated mechanical deformation. In turn, this affects the nuclear YAP mechanoresponses, chromatin methylation and cell invasion in three dimensions. Our results demonstrate a mechanism by which tissues can regulate their sensitivity to mechanical signals.We thank A. Farré and the other members of IMPETUX OPTICS, S.L., for their help and expertise in the design and implementation of the optical tweezers experiments; R. Sunyer for help and advice with the microprinting experiments; S. Usieto, A. Menéndez, N. Castro, M. Purciolas and W. Haaksma for providing technical support; L. Rosetti and S. Saloustros for providing data analysis tools; and J. de Rooij, A. L. Le Roux, L. Faure, A. Labernadie, R. Oria and J. Abenza, as well as all the members of the groups of P.R.-C. and X.T. for helpful discussion. Finally, we thank G. Wiche, A. Sonnenberg and N. Montserrat for providing plasmids, antibodies or cell lines used for this work. We acknowledge funding from the Spanish Ministry of Science and Innovation (PID2021-128635NB-I00 MCIN/AEI/10.13039/501100011033 and ‘ERDF-EU A way of making Europe’ to X.T., PID2019-110949GB-I00 to M.A. and PID2019-110298GB-I00 to P.R.-C.), the European Commission (H2020-FETPROACT-01-2016-731957), the European Research Council (Adv-883739 to X.T.; CoG-681434 to M.A.; StG- 851055 to A.E.-A.), the Generalitat de Catalunya (2017-SGR-1602 to X.T. and P.R.-C.; 2017-SGR-1278 to M.A. and P.S.) and European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement no. 797621 to M.G.-G. The prize ‘ICREA Academia’ for excellence in research to M.A. and P.R.-C., Fundació la Marató de TV3 (201936-30-31 and 201903-30-31-32), and ‘la Caixa’ Foundation (LCF/PR/HR20/52400004 and ID 100010434 under agreement LCF/PR/HR20/52400004). IBEC and CIMNE are recipients of a Severo Ochoa Award of Excellence from MINCIN. A.E.M.B. was supported by a Sir Henry Wellcome Fellowship (210887/Z/18/Z). A.E.-A. receives funding from the Francis Crick Institute, which receives its core funding from the Cancer Research UK (CC2214), the UK Medical Research Council (CC2214) and the Wellcome Trust (CC2214).Peer ReviewedPostprint (published version