Rescuing Cell Polarity with Small Molecule Inhibitors of De‐Palmitoylation

Abstract

Protein palmitoylation is a unique post‐translational modification required for the membrane anchoring and trafficking of numerous regulatory proteins that play key roles in cell growth, polarity, and signaling. In pulse‐chase palmitoylation proteomics studies, we identified the subset of epithelial tumor suppressors as enzymatically regulated palmitoylated proteins in malignant cells. One such protein, Scribble, localizes at the basolateral membrane where it regulates epithelial cell apical‐basolateral polarity, junctional integrity, proliferation, and metastasis. Loss of Scribble at the plasma membrane cooperates with oncogenic Ras or Myc overexpression to drive tumor formation, promote epidermal to mesenchymal transition (EMT), and bypass contact inhibition. Interestingly, overexpression of Snail in polarized cells eliminates Scribble membrane localization. We recently reported a class of in vivo active small selective inhibitors of the acyl protein thioesterases APT1 and APT2. Addition of a small molecule APT2 inhibitor restores Scribble membrane localization and enhances E‐Cadherin expression, overcoming Snail‐mediated repression. Using a combination of x‐ray crystal structures, medicinal chemistry, and mass spectrometry, we present a broadened understanding of thioesterase function and inhibition in cells. These findings highlight APT2 as a primary regulator of cell polarity protein palmitoylation, and highlight a strategy to attenuate oncogenic signaling and restore cell polarity pathways in malignant cells.