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Primary cilia regulate mTORC1 activity and cell size through Lkb1.
Christopher Boehlke1, Fruzsina Kotsis, Vishal Patel
1Renal Unit, Department of Medicine, University Medical Center, Albert-Ludwig-University of Freiburg, Hugstetter Strasse 55, D-79106 Freiburg, Germany.
Nature Cell Biology
|October 26, 2010
Summary
Cilia sense cell flow to control cell size by regulating the mTOR pathway. This study reveals cilia
Area of Science:
- Cell Biology
- Molecular Biology
- Physiology
Background:
- The mechanistic target of rapamycin (mTOR) pathway regulates cell size, with its deregulation implicated in diseases like polycystic kidney disease (PKD).
- Cilia, sensory organelles, are crucial for sensing environmental cues, and their dysfunction is linked to PKD, suggesting a potential role in cellular regulation.
- The integration of external signals by the mTOR pathway and its precise translation into cellular responses remain incompletely understood.
Purpose of the Study:
- To investigate the role of cilia in regulating the mTOR pathway and cell size control.
- To elucidate the molecular mechanisms by which cilia influence mTOR signaling and cellular homeostasis.
Main Methods:
- Ablation of cilia in transgenic mice to assess effects on cell size.
- In vitro analysis of cilia bending induced by fluid flow to study mTOR downregulation.
- Investigation of the involvement of Lkb1, AMPK, calcium transients, and Akt in cilia-mediated cell-size regulation.
Main Results:
- Cilia ablation led to enlarged cells in transgenic mice, indicating a role for cilia in preventing excessive cell growth.
- Cilia bending, induced by fluid flow, is essential for mTOR downregulation and maintaining normal cell size.
- Cilia-mediated cell-size regulation is independent of flow-induced calcium transients and Akt, but relies on Lkb1 localization within the cilium and subsequent AMPK phosphorylation at the basal body.
Conclusions:
- Cilia play a critical role in regulating mTOR signaling and controlling cell size.
- The cilium-basal body compartment acts as a specific site for Lkb1 signaling activation in response to fluid flow.
- Understanding cilia-mTOR interactions provides insights into cellular homeostasis and potential therapeutic targets for diseases like PKD.
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