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The hepatitis B x antigen anti-apoptotic effector URG7 is localized to the endoplasmic reticulum membrane
Stockholm University, Faculty of Science, Department of Biochemistry and Biophysics.
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2013 (English)In: FEBS Letters, ISSN 0014-5793, E-ISSN 1873-3468, Vol. 587, no 18, 3058-3062 p.Article in journal (Refereed) Published
Abstract [en]

Hepatitis B x antigen up-regulates the liver expression of URG7 that contributes to sustain chronic virus infection and to increase the risk for hepatocellular carcinoma by its anti-apoptotic activity. We have investigated the subcellular localization of URG7 expressed in HepG2 cells and determined its membrane topology by glycosylation mapping in vitro. The results demonstrate that URG7 is N-glycosylated and located to the endoplasmic reticulum membrane with an N-lumen-C-cytosol orientation. The results imply that the anti-apoptotic effect of URG7 could arise from the C-terminal cytosolic tail binding a pro-apoptotic signaling factor and retaining it to the endoplasmic reticulum membrane.

Place, publisher, year, edition, pages
2013. Vol. 587, no 18, 3058-3062 p.
Keyword [en]
URG7, Hepatitis B x antigen, Apoptosis, Cellular localization, Topology, Endoplasmic reticulum
National Category
Biochemistry and Molecular Biology Biophysics Cell Biology
URN: urn:nbn:se:su:diva-94175DOI: 10.1016/j.febslet.2013.07.042ISI: 000324033700026OAI: diva2:652628


Funding Agencies:

Swedish Cancer Society;  Swedish Foundation for Strategic Research 

Available from: 2013-10-01 Created: 2013-09-30 Last updated: 2015-01-30Bibliographically approved
In thesis
1. Integration and topology of membrane proteins related to diseases
Open this publication in new window or tab >>Integration and topology of membrane proteins related to diseases
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Membranes are boundaries that separate the cell from the external environment.   Membrane proteins can function as e.g. receptors and channels, allowing cells to communicate with the exterior and molecules to pass through the membrane. The biogenesis of membrane proteins involves a protein-conducting channel that aids the hydrophobic segments to partition into the membrane and translocate the hydrophilic loops. Membrane proteins need to fold to its native conformation including post-translational modifications and assembly with other proteins and/or cofactors. If this regulated pathway goes wrong the degradation machinery degrades the protein. If the system is failing can result in serious disorders. The main focus in this thesis is membrane proteins associated to diseases.

We have studied mutations in the gene of presenilin 1, which is involved in Alzheimer’s disease. We found that some mutations affect the structure and other the function of the PS1. URG7 is an unknown protein associated with liver cancer. We suggest it is localized and targeted to the ER membrane, having an NoutCin topology. SP-C is important for our lungs to function. Mutations can cause the protein to aggregate. We have studied the highly Val-rich transmembrane segment (poly-Val) and its analogue (poly-Leu) and show that poly-Leu folds into a more compact conformation than poly-Val. We show that the C-terminal chaperon-like BRICHOS domain interacts with the ER membrane, suggesting an involvement in poly-Val folding. We have also confirmed the topology of URG7, MRP6 and SP-C poly-Val/Leu using gGFP that is fused to the C-terminal of the protein.

Place, publisher, year, edition, pages
Stockholm: Department of Biochemistry and Biophysics, Stockholm Univeristy, 2015. 76 p.
National Category
Biochemistry and Molecular Biology
Research subject
urn:nbn:se:su:diva-113397 (URN)978-91-7649-094-5 (ISBN)
Public defence
2015-03-06, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 10:00 (English)

At the time of the doctoral defense paper 3 was unpublished and had a status as manuscript.

Available from: 2015-02-12 Created: 2015-01-29 Last updated: 2016-02-23Bibliographically approved

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