Examination of Elm1, polarity, and endocytosis for regulation of cellular morphogenesis in budding yeast - Project Summary Abstract The functionality of specific cells in multicellular organisms are linked to the specific morphologies that those cells adopt. Extensive regulatory networks including polarization, cytoskeletal dynamics, exo- and endocytic membrane trafficking, and cell cycle control must be spatially and temporally controlled to ensure that proliferation and cell division occur in a stereotypical fashion. Errors in properly establishing and maintaining cellular morphologies drive cellular pathologies including many cancers, developmental disorders, and neurodegenerative diseases such as Alzheimer’s. With so many different cellular processes being involved, the coordination between and among them has remained elusive and represents a fundamental question in cellular morphogenesis control. Due to the simplicity of the model organism Saccharomyces cerevisiae, the processes outlined above have been extensively studied and are directly homologous to those in higher eukaryotes. One of the major regulations of cellular morphogenesis in budding yeast is the morphogenesis checkpoint composed of the sequential recruitment of the kinases Elm1 and Hsl1 and a methyltransferase Hsl7 that serves as a scaffold at the bud neck (i.e., site of cell division) to sequester the mitotic CDK inhibitor Swe1 for proteosome-mediated degradation. The degradation of Swe1 then allows cell cycle progression, thereby linking the mitotic cycle with the formation of a bud after genome duplication. Recent data that only active Elm1 can lead to the recruitment of both Hsl1 and Hsl7, along with preliminary global phosphoproteomic and fluorescent microscopy data that Elm1 regulates polarity factors and endocytosis leads to the hypothesis that Elm1 can directly regulate Hsl7 (in addition to Hsl1 as previously known) (Aim 1) and has expanded roles in synergy with the Cdc42 effector Ste20 and the early endocytic protein Ede1 to control cellular morphogenesis (Aim 2). Both these potential regulated effectors of Elm1 are known to play roles in cell shape control and exhibited extensive differential phosphorylation when compared between wild-type cells and cells deleted for the ELM1 gene. The proposed study will employ an integrative approach including gene editing, live cell imaging, and biochemistry to illustrate the regulatory capacity of Elm1 on the hypothesized pathways. This study will impact the understanding of the complexities involved with cellular morphogenesis control and will fill a critical knowledge gap that can give insights important to human health and development.
