Ligand-Occupied Integrin Internalization Links Nutrient Signaling to Invasive Migration

Cell migration is a fundamental process in development and disease, yet the precise mechanisms governing integrin trafficking remain unclear. Prior research has shown that integrins regulate adhesion and motility through dynamic membrane movements. However, the spatiotemporal organization of integrin endocytosis is not well understood. Established knowledge suggests that integrins are internalized during migration, but the role of specific GTPases in this process is less clear. No prior work had resolved how ligand-bound integrins are trafficked to lysosomes. This gap motivated the current investigation into the role of tensin and Arf4 in integrin internalization. The study builds on prior findings linking integrin dynamics to cell invasion. The focus is on α5β1 integrin and its movement under nutrient conditions. The goal is to clarify how integrin trafficking affects lysosome positioning and mTOR signaling.

This study aimed to investigate the role of integrin trafficking in cell migration and nutrient signaling. Specifically, it sought to determine how α5β1 integrin moves from the cell periphery to subnuclear adhesions. The researchers wanted to identify the mechanisms controlling integrin internalization and lysosomal trafficking. They also aimed to explore the connection between integrin endocytosis and mTOR activation. The motivation came from prior observations of integrin involvement in invasive migration. The study focused on the role of tensin and Arf4 in integrin movement. The goal was to test whether integrin trafficking influences lysosome positioning. The findings could clarify how nutrient signaling regulates metastasis.

The study used live-cell imaging to track α5β1 integrin movement in migrating cells. Researchers employed fluorescent labeling to monitor integrin localization and endocytosis. They used RNA interference to suppress tensin and Arf4 expression. Lysosome and integrin co-localization were analyzed using fluorescence microscopy. mTOR activation was assessed through phosphorylation assays. The researchers also tested the effect of nutrient depletion on integrin trafficking. They combined pharmacological inhibitors with genetic knockdowns to confirm findings. The approach integrated molecular biology with live imaging to observe trafficking dynamics.

The strongest finding was that α5β1 integrin undergoes tensin-dependent centripetal movement. Ligand-engaged integrins are internalized via Arf4-dependent endocytosis. These integrins are trafficked to late endosomes/lysosomes for degradation. Suppression of tensin or Arf4 disrupted integrin trafficking to lysosomes. The study found that Arf4 is essential for proper lysosome positioning. mTOR activation was observed at subnuclear lysosomes after integrin internalization. Nutrient depletion increased subnuclear integrin accumulation and endocytosis. The findings suggest a two-way regulatory link between integrin trafficking and mTORC1.

The authors concluded that integrin trafficking is regulated by tensin and Arf4. They proposed that ligand-bound integrins are internalized to lysosomes via Arf4. The study suggests that Arf4-dependent internalization is necessary for lysosome positioning. The findings indicate that mTOR is activated at subnuclear lysosomes. Nutrient depletion promotes integrin accumulation and endocytosis via mTORC1 inhibition. The data support a regulatory interaction between mTORC1 and integrin trafficking. The authors suggest that this interaction may contribute to invasive migration. The study highlights a link between nutrient signaling and metastasis.