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Experimental Models for Study of Retinal Pigment Epithelial Physiology and Pathophysiology
Published on: November 6, 2010
SIRT2 Affects Primary Cilia Formation by Regulating mTOR Signaling in Retinal Pigmented Epithelial Cells
Jeaho Lim1, Juyoung Son1, Jaewook Ryu1
1Department of Biomedical Science, Graduate School, Kyung Hee University, Seoul 02447, Korea.
Abstract:
SIRT2, a member of the Class III HDAC family, participates in diverse cellular processes and regulates several pathological conditions. Although a few reports show that SIRT2 regulates the cell cycle, the causes and outcomes of SIRT2-dependent cell proliferation remain unclear. Here, we examined the effects of SIRT2 suppression in human RPE1 cells using siRNA targeting SIRT2, and AK-1, a SIRT2-specific inhibitor. The number of primary cilia in SIRT2-suppressed cells increased under serum-present conditions. Suppressing SIRT2 induced cell cycle arrest at G0/G1 phase by inactivating mammalian target of rapamycin (mTOR) signaling, possibly through mTORC1. Treatment with torin 1, an inhibitor of mTORC1/mTORC2, yielded results similar to those observed after SIRT2 suppression. However, SIRT2 suppression did not affect primary cilia formation or mTOR signaling following serum starvation. This suggests that SIRT2 acts as a critical sensor that links growth factor-dependent signal transduction and primary cilia formation by regulating the cell cycle.
Insights
SIRT2 (sirtuin 2) suppression increases primary cilia and arrests the cell cycle at G0/G1 by inhibiting mTOR signaling in human cells, linking growth factors to cilia formation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- SIRT2, a Class III HDAC, is involved in various cellular functions and diseases.
- The precise role of SIRT2 in cell cycle regulation and proliferation is not fully understood.
- Primary cilia are crucial cellular organelles implicated in signaling pathways.
Purpose of the Study:
- To investigate the effects of SIRT2 suppression on cell cycle progression and primary cilia formation.
- To elucidate the molecular mechanisms underlying SIRT2-dependent regulation of cell proliferation.
- To determine SIRT2's role as a sensor linking growth factor signaling to cilia dynamics.
Main Methods:
- Human RPE1 cells were treated with siRNA targeting SIRT2 or a SIRT2-specific inhibitor (AK-1).
- Cell cycle distribution was analyzed using flow cytometry.
- Mammalian target of rapamycin (mTOR) signaling was assessed, including experiments with torin 1 (mTORC1/mTORC2 inhibitor).
Main Results:
- SIRT2 suppression led to an increased number of primary cilia in cells cultured under serum-present conditions.
- Suppression of SIRT2 induced G0/G1 cell cycle arrest, associated with inactivation of mTOR signaling (potentially via mTORC1).
- Similar effects on cell cycle and cilia were observed with torin 1 treatment; however, serum starvation did not impact these processes upon SIRT2 suppression.
Conclusions:
- SIRT2 plays a critical role in regulating the cell cycle and primary cilia formation in response to growth factors.
- SIRT2 acts as a sensor connecting growth factor signaling pathways to primary cilia dynamics through mTOR regulation.
- These findings clarify the mechanisms of SIRT2-dependent cell proliferation and provide insights into cilia biology.
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