title: Mitotic phosphorylation activates hepatoma-derived growth factor as a mitogen.
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.
authors.affiliation: Department of Pediatrics, Cardiology Division, Johns Hopkins University, 600 N. Wolfe Street, Baltimore, MD 21287, USA. aeveret3@jhmi.edu
authors.forename: Allen D
authors.initials: AD
authors.lastname: Everett
authors.forename: Jun
authors.initials: J
authors.lastname: Yang
authors.forename: Monzur
authors.initials: M
authors.lastname: Rahman
authors.forename: Pratima
authors.initials: P
authors.lastname: Dulloor
authors.forename: David L
authors.initials: DL
authors.lastname: Brautigan
mesh_terms: D020816:Amino Acid Motifs; D000818:Animals; D002460:Cell Line; D006801:Humans; D036341:Intercellular Signaling Peptides and Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008934:Mitogens / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008938:Mitosis; D010766:Phosphorylation; D051381:Rats
chemical_list: D036341:Intercellular Signaling Peptides and Proteins; D008934:Mitogens; C051610:hepatoma-derived growth factor