Identification of Ribosome-binding Protein p34 as an Intracellular Protein That Binds Acidic Fibroblast Growth Factor

Camilla Skiple Skjerpen,Jørgen Wesche,Sjur Olsnes

doi:10.1074/jbc.m112193200

Camilla Skiple Skjerpen, Jørgen Wesche + Show 1 more

Open Access

https://doi.org/10.1074/jbc.m112193200

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Abstract

With the aim of identifying new intracellular binding partners for acidic fibroblast growth factor (aFGF), proteins from U2OS human osteosarcoma cells were adsorbed to immobilized aFGF. One of the adsorbed proteins is a member of the leucine-rich repeat protein family termed ribosome-binding protein p34 (p34). This protein has previously been localized to endoplasmic reticulum membranes and is thought to span the membrane with the N terminus on the cytosolic side. Confocal microscopy of cells transfected with Myc-p34 confirmed the endoplasmic reticulum localization, and Northern blotting determined p34 mRNA to be present in a multitude of different tissues. Cross-linking experiments indicated that the protein is present in the cell as a dimer. In vitro translated p34 was found to interact with maltose-binding protein-aFGF through its cytosolic coiled-coil domain. The interaction between aFGF and p34 was further characterized by surface plasmon resonance, giving a K(D) of 1.4 +/- 0.3 microm. Even though p34 interacted with mitogenic aFGF, it bound poorly to the non-mitogenic aFGF(K132E) mutant, indicating a possible involvement of p34 in intracellular signaling by aFGF.

Highlights

Acidic fibroblast growth factor1 belongs to the large family of FGF growth factors
Has been shown to enter NIH/3T3, BALB/c 3T3, and human umbilical vein endothelial cells as well as U2OS cells that were stably transfected with high affinity FGF receptor-4 (2, 6 – 8), whereas basic FGF (bFGF) has been found to enter the nucleus from the cytosol of adult bovine aortic endothelial cells in a cell cycledependent manner [9]. acidic fibroblast growth factor (aFGF) signaling through cell-surface receptors is sufficient to induce tyrosine phosphorylation of the receptors and concomitant activation of the MAPK cascade [2, 8]
AFGF forms complexes with synaptotagmin-1 and the calcium-binding protein S100A13 (18 –20). bFGF has been shown to interact with CK2 [21] and with FGF-binding protein-1 (FGF-BP1) [17]; and recently, we found that aFGF interacts with both the ␣- and ␤-subunits of protein kinase CK2.2 bFGF was reported to associate with platelet-derived growth factor-BB [22], the nuclear protein FGF-2-interacting factor [23], and the ribosomal proteins L6 and s19 [24, 25]

Summary

Introduction

Acidic fibroblast growth factor (aFGF)1 belongs to the large family of FGF growth factors. In vitro translated p34 was found to interact with maltose-binding protein-aFGF through its cytosolic coiled-coil domain.

Results

Conclusion