The depalmitoylase APT1 directs the asymmetric partitioning of Notch and Wnt signaling during cell division

Abstract

Asymmetric cell division results in two distinctly fated daughter cells. A molecular hallmark of asymmetric division is the unequal partitioning of cell fate determinants. 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 and β-catenin through the activity of the depalmitoylating enzyme APT1. Using point mutations, we show specific palmitoylated residues on Numb are required for asymmetric localization. By live-cell imaging, we show that reciprocal interactions between APT1 and the Rho-family GTPase CDC42 promote the asymmetric localization of Numb and β-catenin to the plasma membrane. This in turn restricts Notch- and Wnt-responsive transcriptional activity to one daughter cell. Moreover, we show altering APT1 expression changes the transcriptional signatures of MDA-MB-231 triple receptor–negative breast cancer cells similarly to changes in Notch and β-catenin–mediated Wnt signaling. We also show that loss of APT1 depletes a specific subpopulation of tumorigenic cells in colony formation assays. Together, our findings demonstrate that APT1-mediated depalmitoylation is a major mechanism of asymmetric cell division maintaining Notch and Wnt-associated protein dynamics, gene expression, and cellular functions.

A Model of Differential Mammary Growth Initiation by Stat3 and Asymmetric Integrin-α6 Inheritance

“…(legend on next page) observed in tissues (Goulas et al, 2012;Lechler and Fuchs, 2005) but was different from the asymmetric division in suspension observed for Numb, which is non-polar in interphase cells and becomes asymmetrically partitioned during cell division (Stypulkowski et al, 2018;Tosoni et al, 2015; Figures S4G and S4H). To further quantify Integrin-a6 inheritance, we analyzed Stat3-inhibitor-treated NMMECs and TDMMECs by using fluorescence-activated cell sorting.…”

Temporal Profiling Establishes a Dynamic S-Palmitoylation Cycle

“…APT enzymes have been studied nearly exclusively in cancer cell models, where APT1 and APT2 inhibition represses oncogenic signaling and stem cell-like features by modulating lateral polarity complexes 5 and asymmetric cell division 29 . Surprisingly, APT1 −/− /APT2 −/− mice are viable and have no overt developmental defects.…”

Regulation of Wnt Signaling Pathways at the Plasma Membrane and Their Misregulation in Cancer

“…Studies on the zebrafish canonical Wnt ligands have reported that Wnt palmitoylation is essential for activation of signaling but may be dispensable for secretion ( Luz et al, 2014 ; Azbazdar et al, 2019 ). APT1-mediated depalmitoylation has been shown to be important for asymmetric localization of β-catenin and Wnt signaling activity during development ( Stypulkowski et al, 2018 ). Interestingly, Drosophila WntD does not appear to undergo any glycolysis and acylation ( Ching et al, 2008 ).…”