Interaction of the C-terminal domain of p43 and the alpha subunit of ATP synthase. Its functional implication in endothelial cell proliferation.
Human p43 is associated with macromolecular tRNA synthase complex and known as a precursor of endothelial monocyte-activating polypeptide II (EMAP II). Interestingly, p43 is also secreted to induce proinflammatory genes. Although p43 itself seems to be a cytokine working at physiological conditions, most of the functional studies have been obtained with its C-terminal equivalent, EMAP II. To gain an insight into the working mechanism of p43/EMAP II, we used EMAP II and searched for an interacting cell surface molecule. The level of EMAP II-binding molecule(s) was significantly increased in serum-starved tumor cells. Thus, the EMAP II-binding molecule was isolated from the membrane of the serum-starved CEM cell. The isolated protein was determined to be the alpha subunit of ATP synthase. The interaction of EMAP II and alpha-ATP synthase was confirmed by enzyme-linked immunosorbent assay and in vitro pull down assays and blocked with the antibodies raised against EMAP II and alpha-ATP synthase. The binding of EMAP II to the surface of serum-starved cells was inhibited in the presence of soluble alpha-ATP synthase. EMAP II inhibited the growth of endothelial cells, and this effect was relieved by soluble alpha-ATP synthase. Anti-alpha-ATP synthase antibody also showed an inhibitory effect on the proliferation of endothelial cells mimicking the activity of EMAP II. These results suggest the potential interaction of p43/EMAP II with alpha-ATP synthase and its role in the proliferation of endothelial cells.
Chang
Sun Young
SY
Laboratory of Immunology, College of Pharmacy, Seoul National University, Shillimdong, Kwanakgu, Seoul 151-742, Korea.
Park
Sang Gyu
SG
Kim
Sunghoon
S
Kang
Chang-Yuil
CY
D025181:ATP Synthetase Complexes / Q000737:chemistry* / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D000951:Antigens, Neoplasm / Q000737:chemistry* / Q000378:metabolism*; D001011:Aorta / Q000166:cytology; D002417:Cattle; D002455:Cell Division; D002460:Cell Line; D016895:Culture Media, Serum-Free / Q000494:pharmacology; D016207:Cytokines; D004305:Dose-Response Relationship, Drug; D004730:Endothelium, Vascular / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D005434:Flow Cytometry; D005982:Glutathione Transferase / Q000378:metabolism; D006801:Humans; D018613:Microscopy, Confocal; D024101:Mitochondrial Proteins; D008969:Molecular Sequence Data; D009363:Neoplasm Proteins / Q000737:chemistry* / Q000378:metabolism*; D010444:Peptide Elongation Factor Tu / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D016601:RNA-Binding Proteins / Q000737:chemistry* / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism
D000951:Antigens, Neoplasm; D016895:Culture Media, Serum-Free; D016207:Cytokines; D024101:Mitochondrial Proteins; D009363:Neoplasm Proteins; D016601:RNA-Binding Proteins; D011993:Recombinant Fusion Proteins; C091648:TUFM protein, human; C077219:small inducible cytokine subfamily E, member 1; D005982:Glutathione Transferase; D025181:ATP Synthetase Complexes; D010444:Peptide Elongation Factor Tu