title: Subcellular localization of SUN2 is regulated by lamin A and Rab5.
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.
authors.affiliation: Department of Paediatrics and Adolescent Medicine, Li Ka Shing Faculty of Medicine, University of Hong Kong, Pokfulam, Hong Kong SAR, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Liang
authors.forename: Peng Hang
authors.initials: PH
authors.lastname: Chiu
authors.forename: Kit Yan
authors.initials: KY
authors.lastname: Yip
authors.forename: Siu Yuen
authors.initials: SY
authors.lastname: Chan
mesh_terms: D011992:Endosomes / Q000378:metabolism; D031541:Fluorescence Resonance Energy Transfer; D006367:HeLa Cells; D006801:Humans; D015151:Immunoblotting; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics / Q000378:metabolism*; D034904:Lamin Type A / Q000235:genetics / Q000378:metabolism*; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D020696:rab5 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D047908:Intracellular Signaling Peptides and Proteins; D034904:Lamin Type A; D008565:Membrane Proteins; C413025:SUN2 protein, human; C440308:lamin C; D020696:rab5 GTP-Binding Proteins