Hyaluronan binding protein 1 (HABP1)/C1QBP/p32 is an endogenous substrate for MAP kinase and is translocated to the nucleus upon mitogenic stimulation.
The role of hyaluronan binding protein 1 (HABP1) in cell signaling was investigated and in vitro kinase assay demonstrated that it is a substrate for MAP kinase. Phosphorylation of endogenous HABP1 was also observed following treatment of J774 cells with PMA. HABP1 was coimmunoprecipitated with activated ERK, confirming their physical interaction in the cellular context. Upon PMA stimulation of normal rat fibroblast (F111) and transformed (HeLa) cells, the HABP1 level in the cytoplasm gradually decreased with a parallel increase in the nucleus. In HeLa cells, within 6 h of PMA treatment, HABP1 was completely translocated to the nucleus, which was prevented by PD98059, a selective inhibitor of ERK. We also observed that the nuclear translocation of HABP1 is concurrent with that of ERK, suggesting that ERK activation is a requirement for the translocation of HABP1. It is thus established for the first time that HABP1 is a substrate for ERK and an integral part of the MAP kinase cascade.
Majumdar
M
M
Biochemistry Laboratory, Jawaharlal Nehru University, New Delhi-110 067, India.
Meenakshi
J
J
Goswami
S K
SK
Datta
K
K
D021581:Active Transport, Cell Nucleus / Q000187:drug effects; D002352:Carrier Proteins; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism*; D006367:HeLa Cells; D006801:Humans; D018960:Hyaluronan Receptors / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D024101:Mitochondrial Proteins; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism*; D008934:Mitogens / Q000494:pharmacology; D010766:Phosphorylation; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology
C087299:C1QBP protein, human; C490195:C1qbp protein, rat; D002352:Carrier Proteins; D018960:Hyaluronan Receptors; D024101:Mitochondrial Proteins; D008934:Mitogens; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D013755:Tetradecanoylphorbol Acetate