APT1 regulates the asymmetric partitioning of Notch and Wnt signaling during cell division

Asymmetric cell division results in two distinctly fated daughter cells to generate cellular diversity. A major molecular hallmark of an asymmetric division is the unequal partitioning of cell-fate determinant proteins. We have previously established that growth factor signaling promotes protein depalmitoylation to foster polarized protein localization, which in turns drives migration and metastasis. Here, we report protein palmitoylation as a key mechanism for the asymmetric partitioning of the cell-fate determinants Numb (Notch antagonist) and ß-catenin (canonical Wnt regulator) through the activity of a depalmitoylating enzyme, APT1. Using point mutants, we show specific palmitoylated residues on proteins, such as Numb, are required for asymmetric localization. Furthermore, by live-cell imaging, we show that reciprocal interactions between APT1 and CDC42 regulate the asymmetric localization of Numb and ß-catenin to the plasma membrane. This in turn restricts Notch and Wnt transcriptional activity to one daughter cell. Moreover, we show altering APT1 expression changes the transcriptional signatures to those resembling that of Notch and ß-catenin in MDA-MB-231 cells. We also show loss of APT1 depletes the population of CD44+/CD24lo/ALDH+ tumorigenic cells in colony formation assays. Together, the findings of this study demonstrate that palmitoylation, via APT1, is a major mechanism of asymmetric cell division regulating Notch and Wnt-associated protein dynamics, gene expression, and cellular functions. Overall design: Gene expression by RNAseq of MDA-MB-231 triple receptor negative breast cancer cells expressing scramble control vector, shAPT1 knockdown, and APT1wt performed in triplicate. Total of 9 samples were analyzed.

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Stypulkowski E, Asangani IA, Witze ES