Signal transduction pathways involved in phosphorylation and activation of p70S6K following exposure to UVA irradiation.
Ultraviolet light A (UVA) plays an important role in the etiology of human skin cancer, and UVA-induced signal transduction has a critical role in UVA-induced skin carcinogenesis. The upstream signaling pathways leading to p70(S6K) phosphorylation and activation are not well understood. Here, we observed that UVA induces phosphorylation and activation of p70(S6K). Further, UVA-stimulated p70(S6K) activity and phosphorylation at Thr(389) were blocked by wortmannin, rapamycin, PD98059, SB202190, and dominant negative mutants of phosphatidylinositol (PI) 3-kinase p85 subunit (DNM-Deltap85), ERK2 (DNM-ERK2), p38 kinase (DNM-p38), and JNK1 (DNM-JNK1) and were absent in Jnk1-/- or Jnk2-/- knockout cells. The p70(S6K) phosphorylation at Ser(411) and Thr(421)/Ser(424) was inhibited by rapamycin, PD98059, or DNM-ERK2 but not by wortmannin, SB202190, DNM-Deltap85, or DNM-p38. However, Ser(411), but not Thr(421)/Ser(424) phosphorylation, was suppressed in DNM-JNK1 and abrogated in Jnk1-/- or Jnk2-/- cells. In vitro assays indicated that Ser(411) on immunoprecipitated p70(S6K) proteins is phosphorylated by active JNKs and ERKs, but not p38 kinase, and Thr(421)/Ser(424) is phosphorylated by ERK1, but not ERK2, JNKs, or p38 kinase. Moreover, p70(S6K) co-immunoprecipitated with PI 3-kinase and possibly PDK1. The complex possibly possessed a partial basal level of phosphorylation, but not at MAPK sites, which was available for its activation by MAPKs in vitro. Thus, these results suggest that activation of MAPKs, like PI 3-kinase/mTOR, may be involved in UVA-induced phosphorylation and activation of p70(S6K).
Zhang
Y
Y
Hormel Institute, University of Minnesota, Austin, Minnesota 55912, USA.
Dong
Z
Z
Nomura
M
M
Zhong
S
S
Chen
N
N
Bode
A M
AM
Dong
Z
Z
D000730:Androstadienes / Q000494:pharmacology; D000818:Animals; D002460:Cell Line; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology / Q000528:radiation effects; D005419:Flavonoids / Q000494:pharmacology; D007093:Imidazoles / Q000494:pharmacology; D020935:MAP Kinase Signaling System / Q000187:drug effects / Q000502:physiology / Q000528:radiation effects*; D051379:Mice; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048055:Mitogen-Activated Protein Kinase 8; D048056:Mitogen-Activated Protein Kinase 9; D020928:Mitogen-Activated Protein Kinases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D010766:Phosphorylation; D021122:Protein Subunits; D011725:Pyridines / Q000494:pharmacology; D019893:Ribosomal Protein S6 Kinases / Q000378:metabolism* / Q000528:radiation effects; D020123:Sirolimus / Q000494:pharmacology; D014162:Transfection; D014466:Ultraviolet Rays; D000077191:Wortmannin; D048051:p38 Mitogen-Activated Protein Kinases
D000730:Androstadienes; D004791:Enzyme Inhibitors; D005419:Flavonoids; D007093:Imidazoles; D021122:Protein Subunits; D011725:Pyridines; D019869:Phosphatidylinositol 3-Kinases; D048056:Mitogen-Activated Protein Kinase 9; D019893:Ribosomal Protein S6 Kinases; D019950:Mitogen-Activated Protein Kinase 1; D048055:Mitogen-Activated Protein Kinase 8; D020928:Mitogen-Activated Protein Kinases; D048051:p38 Mitogen-Activated Protein Kinases; C090942:4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)imidazole; C093973:2-(2-amino-3-methoxyphenyl)-4H-1-benzopyran-4-one; D020123:Sirolimus; D000077191:Wortmannin