Phosphohexose isomerase/autocrine motility factor/neuroleukin/maturation factor is a multifunctional phosphoprotein.
Phosphohexose isomerase (PHI) is a member of the ectoenzyme/exoenzyme family and plays a key role in both glycolysis and gluconeogenesis pathways. Upon secretion PHI acts as a cytokine with tumor autocrine motility factor (AMF), neuroleukin (NLK) and maturation factor (MF) functions. Signaling is initiated by its binding to a cell surface 78 kDa glycoprotein (gp78). However, since PHI protein is a 'leaderless' secretory protein, released from cells via a non-classical route(s), we questioned whether the molecule undergoes post-translation modification while retaining proper folding and maintaining intact enzymatic and motogenic activities. To address this, we have generated, expressed and isolated a recombinant human AMF (rhAMF). The rhAMF retained the biological activities of the native AMF, i.e., catalyzes phosphohexose isomerization and stimulated cell motility. Additionally, we show here that human PHI is phosphorylated at serine 185 by casein kinase II (CK II) and we provide experimental evidence suggesting that this phosphorylation is associated with secretion, thus providing insights for elucidating the intracellular signal transmission of cell response to stimulation by AMF/NLK/MF.
Haga
A
A
Metastasis Research Program, Karmanos Cancer Institute, Detroit, MI 48201, USA.
Niinaka
Y
Y
Raz
A
A
D000595:Amino Acid Sequence; D047390:Casein Kinase II; D005956:Glucose-6-Phosphate Isomerase / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D008969:Molecular Sequence Data; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D012694:Serine / Q000378:metabolism; D014407:Tumor Cells, Cultured
D011994:Recombinant Proteins; D012694:Serine; D047390:Casein Kinase II; D017346:Protein Serine-Threonine Kinases; D005956:Glucose-6-Phosphate Isomerase