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Subcellular localization of SUN2 is regulated by lamin A and Rab5.

Liang Y, Chiu PH, Yip KY, Chan SY - PLoS ONE (2011)

Bottom Line: We found that expression of lamin A but not lamin C partly restored the nuclear envelope localization of SUN2.Moreover, overexpression of SUN2 stimulated the uptake of transferrin while suppression of SUN2 expression attenuated the process.These findings support a role of SUN2 in endocytosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China.

ABSTRACT
SUN2 is an inner nuclear membrane protein with a conserved Sad1/UNC-84 homology SUN-domain at the C-terminus. Intriguingly, SUN2 has also been reported to interact with Rab5, which localizes in early endosomes. To clarify the dual subcellular localization of SUN2, we investigated its localization in lamin A/C deficient cells rescued with lamin A or lamin C isoform, and in HeLa cells transfected with Rab5 or its mutants. We found that expression of lamin A but not lamin C partly restored the nuclear envelope localization of SUN2. SUN2 was redistributed to endosomes upon overexpression of Rab5, but remained on the nuclear envelope when the SUN domain was deleted. To explore the physiological function of SUN2 in vesicle trafficking and endocytosis, we demonstrated the colocalization of endogenous SUN2 and Rab5. Moreover, overexpression of SUN2 stimulated the uptake of transferrin while suppression of SUN2 expression attenuated the process. These findings support a role of SUN2 in endocytosis.

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The N-terminus of SUN2 (SUN2ΔL) can interact with Rab5.(A) HA-SUN2ΔL (right) localized to both the NE and cytoplasm. Full length SUN2 is shown on the left. Scale bar, 10 µm. (B) HA-SUN2ΔL coimmunoprecipitated with EGFP-Rab5. Negative control is shown on the right.
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pone-0020507-g006: The N-terminus of SUN2 (SUN2ΔL) can interact with Rab5.(A) HA-SUN2ΔL (right) localized to both the NE and cytoplasm. Full length SUN2 is shown on the left. Scale bar, 10 µm. (B) HA-SUN2ΔL coimmunoprecipitated with EGFP-Rab5. Negative control is shown on the right.

Mentions: A previous study has shown that the C-terminus of SUN2 can interact with Rab5 [16]. This raises the question of the physiologic significance of such an interaction between the luminal domain of SUN2 and Rab5, a cytoplasmic protein. To reconcile how Rab5 can affect the localization of endogenous SUN2, we looked into the interaction between the N-terminus of SUN2 (SUN2ΔL) and Rab5. SUN2ΔL localized to both the NE and cytoplasm (Fig. 6A). SUN2ΔL coimmunoprecipitated with Rab5-EGFP, but not EGFP, in cotransfected cells (Fig. 6B). This data suggest possible interaction between Rab5 and SUN2 under physiological conditions.


Subcellular localization of SUN2 is regulated by lamin A and Rab5.

Liang Y, Chiu PH, Yip KY, Chan SY - PLoS ONE (2011)

The N-terminus of SUN2 (SUN2ΔL) can interact with Rab5.(A) HA-SUN2ΔL (right) localized to both the NE and cytoplasm. Full length SUN2 is shown on the left. Scale bar, 10 µm. (B) HA-SUN2ΔL coimmunoprecipitated with EGFP-Rab5. Negative control is shown on the right.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105078&req=5

pone-0020507-g006: The N-terminus of SUN2 (SUN2ΔL) can interact with Rab5.(A) HA-SUN2ΔL (right) localized to both the NE and cytoplasm. Full length SUN2 is shown on the left. Scale bar, 10 µm. (B) HA-SUN2ΔL coimmunoprecipitated with EGFP-Rab5. Negative control is shown on the right.
Mentions: A previous study has shown that the C-terminus of SUN2 can interact with Rab5 [16]. This raises the question of the physiologic significance of such an interaction between the luminal domain of SUN2 and Rab5, a cytoplasmic protein. To reconcile how Rab5 can affect the localization of endogenous SUN2, we looked into the interaction between the N-terminus of SUN2 (SUN2ΔL) and Rab5. SUN2ΔL localized to both the NE and cytoplasm (Fig. 6A). SUN2ΔL coimmunoprecipitated with Rab5-EGFP, but not EGFP, in cotransfected cells (Fig. 6B). This data suggest possible interaction between Rab5 and SUN2 under physiological conditions.

Bottom Line: We found that expression of lamin A but not lamin C partly restored the nuclear envelope localization of SUN2.Moreover, overexpression of SUN2 stimulated the uptake of transferrin while suppression of SUN2 expression attenuated the process.These findings support a role of SUN2 in endocytosis.

View Article: PubMed Central - PubMed

Affiliation: Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China.

ABSTRACT
SUN2 is an inner nuclear membrane protein with a conserved Sad1/UNC-84 homology SUN-domain at the C-terminus. Intriguingly, SUN2 has also been reported to interact with Rab5, which localizes in early endosomes. To clarify the dual subcellular localization of SUN2, we investigated its localization in lamin A/C deficient cells rescued with lamin A or lamin C isoform, and in HeLa cells transfected with Rab5 or its mutants. We found that expression of lamin A but not lamin C partly restored the nuclear envelope localization of SUN2. SUN2 was redistributed to endosomes upon overexpression of Rab5, but remained on the nuclear envelope when the SUN domain was deleted. To explore the physiological function of SUN2 in vesicle trafficking and endocytosis, we demonstrated the colocalization of endogenous SUN2 and Rab5. Moreover, overexpression of SUN2 stimulated the uptake of transferrin while suppression of SUN2 expression attenuated the process. These findings support a role of SUN2 in endocytosis.

Show MeSH
Related in: MedlinePlus