Gabriela Villalpando Torres is a rising senior currently studying bioengineering at the University of California Merced. She is an undergraduate researcher in Dr. Robert Mauck’s lab, investigating regulators that dysregulate SMAD signaling in cells with fibrodysplasia ossificans progressiva. After earning her bachelor’s degree, Gabriela plans to pursue a PhD in biomedical engineering.
Substrate stiffness and contractility regulate Nesprin expression in 3T3 cells
Mechanotransduction is the process by which cells convert mechanical stimuli to biochemical cues1. The cytoskeleton transfers forces from the ECM to the nucleus via the Linker of Nucleoskeleton and Cytoskeleton (LINC) complex. One component of the LINC complex is nesprin, a family of large proteins that can bind cytoskeletal elements and are required for cytoskeletal-nuclear mechanotransduction. While much is known regarding the role of the LINC complex in mechanotransduction, less is known about how the LINC complex itself is regulated by mechanical forces. To address this, we investigated nesprin expression in response to changing microenvironmental stiffness and alterations in cytoskeletal architecture and tension. Nesprin expression was measured by quantitative polymerase chain reaction (qPCR) with primers designed for each isoform of nesprin 1 and 2. Immunofluorescence (IF) was used to evaluate nesprin localization, nesprin-cytoskeletal engagement, and qualitative expression based on intensity. 3T3 cells were seeded on polyarylamide gels and stained by IF for cytoskeletal components and Nesprin 1/2 to investigate the effects of substrate stiffness. To study the effects of contractility, the same experiment was repeated with exposure to a contractility antagonist (Y-27632) or agonist (CNO3). Decreasing substrate stiffness (from glass to 5kPa) on either fibronectin- or laminin-coated PA gels resulted in an increase in nuclear nesprin 1 and 2 staining intensity. Inhibition and promotion of contractility led to similar increases on tissue culture plastic. Substrate stiffness also appears to be a regulator of nesprin expression and localization, and contractility impacts which cytoskeletal element engages with nesprins. It could be that decreasing substrate stiffness increases nesprin expression to help anchor the cells to a softer environment and contractility regulates which cytoskeletal element participates in this cytoskeletal-nuclear mechanotransduction.