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| hnRNPK Interacts with Nef and Facilitates the Cell Surface Expression of CD4 |
| WEI Jin-mei, FAN Xiao-qin, XIONG Hai-ting, GAO Xue-juan, LIU Xiao-hui, LIU Lang-xia |
| Key Laboratory of Functional Protein Research of Guangdong Higher Education Institutes, Institute of Life and Health Engineering, Jinan University, Guangzhou 510632, China |
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Abstract Objective: Previous studies have respectively demonstrated that HIV-1 Nef down-regulated the cell surface expression of CD4, and that Nef interacted with the host protein hnRNPK. The purpose is to investigate (1) if hnRNPK regulates the surface expression of CD4, and (2) if hnRNPK is involved in the down-regulation of CD4 by HIV-1 Nef. Methods: in vitro GST-pulldown assay was used to confirm the interaction of HIV-1 Nef with hnRNPK. HIV-1 Nef was expressed in HeLa-CD4 cells by transient transfection, hnRNPK was knocked down by means of siRNA, and the cell surface expression level of CD4 was assessed by using flow cytometry. Results: (1) The GST-pulldown assay has successfully confirmed the Nef-hnRNPK interaction; (2) Nef ectopic expression resulted in about 75 percent reduction of the cell surface CD4 expression; (3) hnRNPK knockdown reduced dramatically the cell surface expression of CD4(50% of reduction) regardless Nef was present or not. Similarly, the effect of Nef on the cell surface expression of CD4 was not affected by hnRNPK knockdown. Conclusion: (1) hnRNPK interacts with Nef; (2) hnRNPK facilitates the cell surface expression of CD4, but the relationship between this effect and the down-regulation of CD4 expresion by Nef remains unclear, probably reflecting the complex regulation involving other factors.
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Received: 15 February 2015
Published: 25 April 2015
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