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Open Access Research article

Mitotic phosphorylation activates hepatoma-derived growth factor as a mitogen

Allen D Everett1*, Jun Yang1, Monzur Rahman1, Pratima Dulloor1 and David L Brautigan2

Author affiliations

1 Department of Pediatrics, Cardiology Division, Johns Hopkins University, 600 N. Wolfe Street, Baltimore, 21287, USA

2 Center for Cell Signaling and Department of Microbiology, University of Virginia, 1400 Jefferson Park Avenue, Charlottesville, 22908, USA

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Citation and License

BMC Cell Biology 2011, 12:15  doi:10.1186/1471-2121-12-15

Published: 13 April 2011

Abstract

Background

Hepatoma-derived growth factor (HDGF) is a nuclear protein that is a mitogen for a wide variety of cells. Mass spectrometry based methods have identified HDGF as a phosphoprotein without validation or a functional consequence of this post-translational modification.

Results

We found that HDGF in primary mouse aortic vascular smooth muscle cells (VSMC) was phosphorylated. Wild type HDGF was phosphorylated in asynchronous cells and substitution of S103, S165 and S202 to alanine each demonstrated a decrease in HDGF phosphorylation. A phospho-S103 HDGF specific antibody was developed and demonstrated mitosis-specific phosphorylation. HDGF-S103A was not mitogenic and FACS analysis demonstrated a G2/M arrest in HDGF-S103A expressing cells, whereas cells expressing HDGF-S103D showed cell cycle progression. Nocodazole arrest increased S103 phosphorylation from 1.6% to 29% (P = 0.037).

Conclusions

Thus, HDGF is a phosphoprotein and phosphorylation of S103 is mitosis related and required for its function as a mitogen. We speculate that cell cycle regulated phosphorylation of HDGF may play an important role in vascular cell proliferation.