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GSK‐3β phosphorylation regulates Aspartyl‐(asparaginyl)‐β‐hydroylase (AAH) expression and directional motility in hepatocellular carcinoma (HCC) cells: Implications for preventing metastatic spread of HCC
Author(s) -
Lizarazo Diana Beatriz,
Gao JinSong,
Tong Ming,
Wands Jack R,
Monte Suzanne M
Publication year - 2011
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.25.1_supplement.442.2
AAH is an 86 kDa transmembrane protein highly expressed in malignant neoplasms, including HCC. AAH is regulated by insulin/IGF, and has a functional role in cell motility through hydroxylation of NOTCH and Jagged. Recent studies showed that AAH could be phosphorylated by GSK‐3β, PKC, or CKII, and that inhibition of these kinases increases AAH protein stabilization and cell motility. This study examined how phosphorylation sites on AAH protein modulate AAH expression and function in transiently transfected Huh7 HCC or PNET2 CNS neuroblastoma cells. Predicted phosphorylation sites on Myc‐tagged AAH were changed from Ser or Thr to Ala by site‐directed mutagenesis. Western blot analyses and ELISAs demonstrated increased AAH protein expression in cells transfected with Myc‐AAH mutants in which GSK‐3β phosphorylation sites were mutated within the N‐terminus. Correspondingly, directional motility assays demonstrated increased adhesion and motility in cells transfected with Myc‐AAH mutated at S10, S18, S24, or S29 within the N‐terminal region. Since GSK‐3β phosphorylation inhibits AAH protein expression and function, GSK‐3β agonists may have therapeutic value for reducing metastatic spread of HCC. Research supported by grant #AA‐11431, AA‐12908, AA‐16126 from the National Institutes of Health.