The DNA repair protein ku is involved in gp130-mediated signal transduction events in PBMC from young but not from elderly subjects.
Ku, composed of 70kDa (ku 70) and 86kDa (ku 80) proteins, is the DNA-targeting subunit of the DNA-dependent serine/threonine kinase (DNA-PK), which plays a crucial role in DNA double strand break recognition and repair in mammalian cells. We have investigated the effects of an IL-6-type cytokine (K-7/D-6), known to trigger gp130, on the expression and function of the ku protein in cytoplasmic and nuclear extracts of freshly isolated human peripheral blood mononuclear cells (PBMC) from subjects of different ages. DNA-binding of nuclear ku was found to be increased by cytokine treatment of cells from young donors but only to a negligible extent from elderly subjects. This cytokine effect was correlated with a greater amount of phosphorylated ku 80, rather than increased expression of ku 70 and ku 80 proteins. DNA-binding activity of cytoplasmic ku was hardly discernible, as compared to nuclear ku, in both young and elderly subjects and was unaffected by the cytokine treatment regardless of age. Regarding the mechanisms whereby ku and gp130 signaling are coupled in PBMC, results from co-immunoprecipitation experiments have shown that ku in the cytoplasm of PBMC from young, but not from elderly subjects, is associated with Tyk-2, a kinase involved in signal transduction events after gp130 triggering by IL-6-type cytokines. This association was independent of PHA stimulation. Moreover, the present results indicate that after gp130 signaling both Tyk-2 and ku 80 are phosphorylated, suggesting their activation by K-7/D-6.
Frasca
Daniela
D
Laboratory of Immunology, ENEA C.R. Casaccia, AMB-PRO-TOSS, Via Anguillarese 301, 00060 S. Maria di Galeria, Rome, Italy. dfrasca@med.miami.edu
Scarpaci
Salvatore
S
Barattini
Paola
P
Bartoloni
Carlo
C
Guidi
Luisa
L
Costanzo
Mario
M
Doria
Gino
G
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000375:Aging / Q000378:metabolism*; D015703:Antigens, CD / Q000378:metabolism*; D034961:Antigens, Nuclear; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D050822:Cytokine Receptor gp130; D003593:Cytoplasm / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D004265:DNA Helicases; D004260:DNA Repair; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000378:metabolism*; D005260:Female; D006801:Humans; D015850:Interleukin-6 / Q000378:metabolism; D000072200:Ku Autoantigen; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D008297:Male; D008562:Membrane Glycoproteins / Q000378:metabolism*; D009687:Nuclear Proteins / Q000096:biosynthesis / Q000378:metabolism*; D010766:Phosphorylation; D011505:Protein-Tyrosine Kinases; D011506:Proteins / Q000378:metabolism; D015398:Signal Transduction; D053634:TYK2 Kinase
D015703:Antigens, CD; D034961:Antigens, Nuclear; D004268:DNA-Binding Proteins; C494199:IL6ST protein, human; D015850:Interleukin-6; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D011506:Proteins; D050822:Cytokine Receptor gp130; D004247:DNA; D011505:Protein-Tyrosine Kinases; D053634:TYK2 Kinase; C070139:TYK2 protein, human; D004265:DNA Helicases; C106893:XRCC5 protein, human; C000606509:Xrcc6 protein, human; D000072200:Ku Autoantigen