Examination of the effects of Myosin-1e expression on tumor behavior and computational analysis of MYO1E mutations associated with kidney disease

Abstract

Actin and actin cytoskeleton associated proteins are important for maintenance of cellular homeostasis and cellular processes such as cell polarization, cell movement, and endocytosis. The long-tailed class one myosin, Myosin-1e (Myo1e), is an actin dependent molecular motor that is found to be expressed in and contribute to the function of epithelial cells. Specific mutations of Myo1e are associated with dysfunction of specialized kidney epithelial cells known as podocytes and increased incidence of kidney disease. We found that disease associated mutation of Myo1e affects the conformation of key functional domains within the Myo1e protein structure using molecular dynamic simulations (Chapter 2). This finding leads to a more mechanistic understanding of dysfunctional Myo1e protein conformational pathways that may be associated with kidney disease. We also find that Myosin-1e expression influences the behavior of mammary tumors in mice (Chapter 3). Specifically, mammary epithelial cell oncogenic transformation induced using the MMTV-PyMT oncogene (mouse mammary tumor virus, polyoma middle T-antigen) was phenotypically altered in mice lacking Myo1e expression compared to Myo1e expressing mice. The tumor cells in mice lacking Myo1e were more differentiated and expressed transcriptomic profiles associated with tumor suppression compared to the more oncogenic profiles of Myo1e expressing cells. In-vitro analysis revealed a cell autonomous effect of Myo1e expression on cell-cell junctional strength and gene expression associated with differentiation (Chapter 3). Appendix chapters 1 and 2 discuss experiments examining Myo1e expression on in-vitro cell migration and epithelial to mesenchymal transition (EMT). Overall, experiments discussed in this thesis have uncovered insight into the effects of Myo1e expression on breast cancer progression, cell differentiation and motility. Moreover, experiments in this thesis also contribute to further understanding of the dynamics of protein conformation associated with disease mutations of a class one myosin.