Mechanisms of E-cadherin force transmission

All cells experience force. Tension, compression, and shear stress are all forces that can arise from normal cellular processes. Imbalances in sensing and responding to force can contribute to multiple diseases such as, cancer, diabetes, and cardiovascular disease. Identifying mechanisms by which cells sense and respond to force under normal conditions can deepen our understating of how these diseases progress and occur.

External forces are sensed by cell surface adhesion receptors, such as the cadherins. In epithelia, E-cadherin is the principal adhesion receptor at intercellular junctions and mediates adhesion between neighboring cells. In response to force, E-cadherin triggers robust actin cytoskeletal reinforcement and growth of the adhesion complex. Collectively, known as cell stiffening or reinforcement. These changes allow cells to resist the force and are energetically costly. However, little is known on how energy generation and E-cadherin mediated force transmission are linked.

In this thesis I investigate how the application of force on E-cadherin stimulates actomyosin contractility, glucose uptake, and ATP production. More specifically, I focus on determining the force-induced linkage between glucose uptake and the reinforcement of the actin cytoskeleton. I determine that force on E-cadherin localizes and enriches the glucose transporter, GLUT1. Localization of GLUT1 is required for force-induced glucose uptake, ATP production and reinforcement of actin and the cadherin-adhesion complex. Additionally, I identify a novel linkage between GLUT1, E-cadherin, and an adaptor protein, ankyrin G. Ankyrin G is known to meditate the retention of several membrane-bound proteins and bind to E-cadherin directly. I demonstrate that binding of Ankyrin G to E-cadherin is required for the localization and enrichment of GLUT1 to the cadherin-containing junctions in response to force. Furthermore, the reinforcement of actin and the adhesions are dependent on ankyrin G binding to E-cadherin.

The work in this thesis provides three significant conceptual advancements: (1) a mechanism by which force induces glucose uptake, (2) the identification of a force-activated glucose transporter, (3) a novel link between cytoskeletal reinforcement and nutrient uptake.