All cells experience force. These forces are sensed by cell surface adhesion receptors and trigger robust actin cytoskeletal rearrangements and growth of the associated adhesion complex to counter the applied forces. This process is known as cell stiffening or reinforcement. The actin re-arrangements necessary for stiffening are energetically costly suggesting that mechanisms coupling force transduction and energy production exist. Previously our laboratory identified a mechanism for coupling force transmission and energy utilization. We demonstrated that, in response to force, AMPK is recruited and activated at the E-cadherin adhesion complexes, thereby stimulating actomyosin contractility, glucose uptake, and ATP production. This increase in glucose uptake and ATP provides the energy necessary to grow the adhesion complexes and reinforce the actin cytoskeleton. Despite this advancement, how mechanical force modulates glucose uptake and glucose metabolism is not fully understood. This study aims to determine how glucose transporter-1 (GLUT1) affects force-induced metabolic changes and cell stiffening. Here we suggest that GLUT1 is the force-sensitive glucose transporter responsible for the glucose uptake necessary for the growth of adhesion complexes and reinforcement of the actin cytoskeleton. In further support of this notion, we show that GLUT1 is recruited to the cell-cell junctions and forms a complex with E-cadherin in response to force. Furthermore, we present evidence that inhibition of GLUT1 blocks force-induced cell stiffening. A second goal of the proposed work in this study is to assess how glucose metabolism is coupled to E-cadherin mediated cytoskeleton rearrangements. Multiple glycolytic enzymes are bound to filamentous actin (F-actin), such as aldolase and phosphofructokinase-1. Previous studies have demonstrated that F-actin bound aldolase is released upon insulin stimulated actin remodeling. We propose that the application of force to E-cadherin causes the release of F-actin-bound glycolytic enzymes, such as aldolase and PFK. Additionally, we suspect that cytosolic release of these enzymes mediates the increase and localization of glycolysis, necessary for force-induced energy production. This study proposes a novel connection between glucose metabolism and the energy-intensive process of force-induced cell stiffening.
Throughout their lifetimes, all cells experience force, such as tension, compression, and shear stress. Cellular imbalances in sensing and responding to force can contribute to multiple diseases such as, cancer, diabetes, and muscular dystrophies. A better understanding these diseases can arise by developing insight into the identity and complexity of the normal process by which cells respond to force. The work proposed in this study will establish a paradigm for how glucose is taken up in response to force and identify how the generation of energy is linked to cytoskeletal remodeling.
