# Regulatory mechanisms for Snail protein stability: ubiquitin–proteasome system and chaperone-mediated autophagy

## TL;DR

Snail, a protein that promotes cancer spread, is controlled by two cellular systems that break it down, and disrupting these systems can lead to cancer metastasis.

## Contribution

This review integrates recent findings on dual degradative control of Snail via the ubiquitin–proteasome system and chaperone-mediated autophagy.

## Key findings

- The ubiquitin–proteasome system regulates Snail stability through phosphorylation and ubiquitination.
- Chaperone-mediated autophagy selectively degrades cytoplasmic Snail via LAMP2A-dependent lysosomal pathways.
- Impairment of chaperone-mediated autophagy leads to nuclear Snail accumulation and enhanced metastasis.

## Abstract

Snail (SNAI1), a central transcription factor driving epithelial–mesenchymal transition (EMT), is pivotal in cancer metastasis and tissue remodeling. Owing to its labile nature, Snail activity is tightly controlled by post-translational modifications that dictate its stability. Here this review summarizes how the ubiquitin–proteasome system orchestrates Snail degradation through coordinated phosphorylation and ubiquitination, mediated by diverse E3 ligases and regulated by kinases, acetyltransferases and deubiquitinases. These mechanisms dynamically adjust Snail levels in both the cytoplasm and nucleus, thereby modulating EMT outcomes. In parallel, emerging studies reveal that chaperone-mediated autophagy (CMA) provides an additional layer of regulation. Through recognition of KFERQ-like motifs, CMA selectively directs cytoplasmic Snail to lysosomes for LAMP2A-dependent degradation, functioning as a quality control system. Impairment of CMA leads to nuclear accumulation of Snail, enhancing its EMT-inducing and prometastatic potential. Together, the ubiquitin–proteasome system and CMA represent complementary, context-dependent axes that maintain Snail homeostasis. Their disruption facilitates EMT activation and metastatic progression. By integrating recent findings, this review highlights the dual degradative control of Snail and its implications for cancer biology, providing a conceptual framework for therapeutic approaches aimed at restoring degradative balance and limiting metastasis.

Cancer can spread in the body through a process called metastasis, which is often linked to a change in cell behavior known as epithelial–mesenchymal transition (EMT). A protein called Snail plays a key role in EMT by helping cancer cells become more mobile and invasive. Researchers are trying to understand how Snail is controlled because it could lead to new cancer treatments. Snail is usually broken down by the cell’s waste disposal system, the ubiquitin–proteasome system. This involves tagging Snail with a small protein called ubiquitin, which marks it for destruction. However, Snail can also be degraded through another process called chaperone-mediated autophagy, where it is transported to lysosomes for breakdown. This study found that when Snail avoids these degradation pathways, it accumulates and promotes cancer spread.

This summary was initially drafted using artificial intelligence, then revised and fact-checked by the author.