Mechanical Regulation of Glycolysis via Cytoskeleton Architecture
The mechanical properties of the microenvironment continuously induce cells to modulate functions like growth, survival, apoptosis, differentiation, and morphogenesis. These adaptations rely on dynamic cytoskeletal remodeling and actomyosin contractility. Although all these processes are coupled to energy consumption, it is unknown if and how cells metabolically adapt to mechanical cues. In this thesis, I demonstrate that phosphofructokinase (PFK), a rate-limiting regulator of glycolysis, responds to mechanical cues in human bronchial epithelial cells (HBECs). Transferring HBECs from stiff to soft substrates causes downregulation of glycolysis via degradation of PFK. The loss of PFK expression is triggered by stress fiber disassembly, which releases the PFK-targeting E3 ubiquitin ligase, tripartite motif(TRIM)-containing protein 21 (TRIM21). Transformed non-small cell lung cancer cells (NSCLCs), which maintain high glycolytic rates regardless of changing mechanical cues, retain PFK expression by downregulating TRIM21, and by sequestering residual TRIM21 to a stress fiber population that is insensitive to substrate stiffness. Thus, I dissected a mechanism by which glycolysis responds to architectural features of the actomyosin cytoskeleton, coupling cell metabolism to the mechanical properties of the surrounding tissue. These processes enable normal cells to modulate energy production in variable microenvironments, while the resistance of the cytoskeleton to respond to extracellular mechanical cues allows high glycolytic rates to persist in cancer cells despite constant alterations of the tumor tissue.