Rag GTPases and mTORC1 regulate intestinal stem cell activity in response to nutrient availability

Area of Science:

• Cell Biology
• Developmental Biology
• Gastroenterology

Background:

• The intestinal epithelium maintains homeostasis by regulating intestinal stem cell (ISC) activity.
• Dietary cues are integrated by enterocytes (ECs) to control ISC function, but mechanisms are unclear.
• Nutrient-sensing pathways, including Rag GTPases and mTORC1, are crucial for cellular function.

Purpose of the Study:

• To investigate the roles of Rag GTPases and mTORC1 in regulating Drosophila ISC activity.
• To elucidate the signaling pathways by which nutrient sensing in ECs impacts ISC proliferation and differentiation.

Main Methods:

• Genetic manipulation of Rag GTPases and mTORC1 in Drosophila enterocytes and ISCs.
• Analysis of gene expression (Mitf, Upd3) and signaling pathways (JAK-STAT).
• Assessment of ISC proliferation and differentiation under varying nutrient conditions.

Main Results:

• Inhibition of Rag GTPases in ECs activates Mitf, inducing Upd3 expression and non-cell autonomous ISC proliferation via JAK-STAT.
• mTORC1 inactivation in ECs also increases ISC activity through Upd3-JAK-STAT, but independently of Mitf.
• Nutrient starvation enhances ISC activity and Upd3 expression, supporting a role for nutrient sensing in ISC regulation.

Conclusions:

• A nutrient-sensing regulatory network involving Rag GTPases-Mitf axis and mTORC1 activity controls ISC proliferation.
• Enterocyte-specific nutrient sensing pathways modulate ISC behavior through paracrine signaling.
• These findings reveal novel mechanisms linking diet to intestinal homeostasis.