Skip to Content
Merck
  • Signal transduction pathways involved in phosphorylation and activation of p70S6K following exposure to UVA irradiation.

Signal transduction pathways involved in phosphorylation and activation of p70S6K following exposure to UVA irradiation.

The Journal of biological chemistry (2001-03-30)
Y Zhang, Z Dong, M Nomura, S Zhong, N Chen, A M Bode, Z Dong
ABSTRACT

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).

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
MAP Kinase 1/Erk1 Protein, active, 10 µg, Active, recombinant, full-length, human MAP Kinase 1/Erk1 containing an N-terminal GST tag, for use in Kinase Assays.
Sigma-Aldrich
JNK1α1/SAPK1c Protein, active, 10 µg, Active, recombinant full-length human JNK1α1/SAPK1c with an N-terminal His-tag, for use in Kinase Assays.
Sigma-Aldrich
MAP Kinase 2/Erk2 Protein, active, mouse, 10 µg, Active, N-terminal GST-tagged, recombinant MAP Kinase 2, expressed in E. coli cells, activated using MEK1 (Catalog #14-429). For use in Kinase Assays.
Sigma-Aldrich
JNK2α2/SAPK1a Protein, active, 10 µg, Active, N-terminal His-tagged, full length human JNK2α2/SAPK1a, for use in Kinase Assays.