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

Fracture and fatigue of rock bit cemented carbides: Mechanics and mechanisms of crack growth resistance under monotonic and cyclic loading

In an attempt to improve the material selection, design and reliability of rock bit WC-Co cemented carbides (hardmetals), an extensive and detailed study is conducted with the main goal of characterizing the fracture and fatigue crack growth (FCG) behavior of four hardmetal grades. Work includes basic microstructural and mechanical characterization of the materials, assessment of fracture toughness and FCG kinetics. It is found that rock bit cemented carbides exhibit relatively high fracture toughness values (between 17 and 20 MPa root m) in direct association with their specific microstructural characteristics, i.e. medium/coarse carbide grain size and medium cobalt content. The influence of microstructure on the measured crack growth mechanics under monotonic loading may be accounted by considering the effective operation of ductile ligament bridging and crack deflection as the prominent toughening mechanisms. Regarding FCG behavior, it is observed to exhibit a significant Km influence. Furthermore, relative increments in toughness are maintained, in terms of crack growth threshold, under cyclic loading. As a consequence, fatigue sensitivity for rock bit cemented carbides is found to be lower than that extrapolated from data reported for fine-grained grades. Crack growth resistance under cyclic loading for the hardmetals studied may be understood on the basis that prevalent toughening mechanisms (ductile ligament bridging and crack deflection) show distinct susceptibility to fatigue degradation and are thus critical in determining fatigue sensitivity. (C) 2014 Elsevier Ltd. All rights reserved