Spermidine promotes adipogenesis of 3T3-L1 cells by preventing interaction of ANP32 with HUR and PP2A

We previously showed that the polyamine spermidine is indispensable for differentiation of 3T3-L1 preadipocytes. Here, we studied the mechanism of spermidine function by using polyamine biosynthesis inhibitor α-difluoromethylornithine in combination with the metabolically stable polyamine analogs γ-methylspermidine or (R,R)-α,ω-bismethylspermine. At the early phase of differentiation, spermidine-depleted 3T3-L1 cells showed decreased translation of transcription factor CCAAT/enhancer binding protein β (C/EBPβ), decreased protein phosphatase 2A (PP2A) activity and increased cytoplasmic localization of the RNA-binding protein human antigen R (HuR). The amount of HuR bound to C/EBPβ mRNA was reduced, whereas the amount of bound CUGBP2, an inhibitor of C/EBPβ translation, was increased. Acidic nuclear phosphoproteins 32 (ANP32), which are known PP2A inhibitors and HuR ligands, bound more PP2A and HuR in spermidine-depleted than in control cells, while immunodepletion of ANP32 from the lysate of spermidine-depleted cells restored PP2A activity. Taken together, our data shows that spermidine promotes C/EBPβ translation in differentiating 3T3-L1 cells, and that this process is controlled by the interaction of ANP32 with HuR and PP2A.

Source: BJ Cell - May 14, 2013 Category: Biochemistry Authors: M T Hyvönen, T Koponen, J Weisell, M Pietilä, A R Khomutov, J Vepsäläinen, L Alhonen, T A Keinänen Tags: BJ Cell Source Type: research