Date of Award

2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Graduate Group

Cell & Molecular Biology

First Advisor

Eric S. Witze

Abstract

Protein palmitoylation is a reversible lipid modification that regulates protein-membrane interaction, activity, trafficking, and stability in a spatio-temporal manner similar to phosphorylation and ubiquitination. Asymmetric cell division results in two distinctly fated daughter cells, by unequally partitioning proteins known as cell fate determinants. I have characterized a mechanism for protein palmitoylation to asymmetrically partition cell fate determinants, e.g. Numb and β-catenin, through the activity of the depalmitoylating enzyme APT1. Using point mutations, I have found specific palmitoylated residues on Numb are required for its asymmetric localization in dividing cells. By live-cell imaging, I have also identified a reciprocal interaction between APT1 and the Rho family GTPase, CDC42, which promotes asymmetric localization of Numb and β-catenin to the plasma membrane. In turn, this mechanism restricts Notch- or Wnt-responsive transcriptional activity to one daughter cell. Moreover, I show that altering APT1 expression levels alters the transcriptional signatures of MDA-MB-231 triple receptor-negative breast cancer cells, resembling altered Notch and β-catenin-mediated Wnt signaling. Furthermore, loss of APT1 depletes a specific subpopulation of tumorigenic cells. Together, this dissertation presents palmitoylation as a major mechanism of asymmetric cell division that maintains Notch- and Wnt-associated protein dynamics, gene expression, and cellular functions.

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Additional Files

Stypulkowski_Supplementary Table 1 .xlsx (15973 kB)
Stypulkowski_Supplementary Movies.zip (1006 kB)

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Cell Biology Commons

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