Differential phosphorylation of mitogen-activated protein kinase families by epidermal growth factor and ultraviolet B irradiation in SV40-transformed human keratinocytes

Abstract

ELSEVIER, Nakamura, S; Takahashi, H; Kinouchi, M; Manabe, A; Ishida-Yamamoto, A; Hashimoto, Y; Iizuka, H, JOURNAL OF DERMATOLOGICAL SCIENCE, 25(2), 139-149, 2001. authorSV-40 transformed human keratinocytes (SVHK cells) were stimulated with epidermal growth factor (EGF)2 and ultraviolet B (UVB) irradiation. Following the stimulation, cell growth, apoptosis, and the activities of mitogen-activated protein (MAP) kinase families were analyzed. EGF (100ng/ml) increased SVHK cell number compared with control cells cultured in serum-free DMEM medium. The EGF-stimulated cells did not show DNA fragmentation. In contrast, UVB irradiation (40mJ/cm2) markedly decreased viable cell number, that was accompanied with DNA fragmentation. EGF stimulated extracellular signal-regulated kinase (ERK) and stress-activated protein kinase/c-Jun N-terminal kinase (JNK). Following the EGF stimulation, phosphorylated ERK and JNK were detected by phospho-p42/44 MAP kinase antibody and phospho-SAPK/JNK antibody, respectively. On the other hand, UVB irradiation stimulated the phosphorylation of p38 and JNK but not of ERK. The stimulation of ERK and JNK induced by EGF was observed earlier than the stimulation of p38 and JNK induced by UVB. PD98059, a specific MAP kinase kinase (MAPKK) 1 (also referred to as MEK1) inhibitor, inhibited EGF-dependent cell proliferation, that was associated with the inhibition of ERK and JNK phosphorylation. In contrast, UVB-induced overall cell death was not significantly affected by PD98059, that inhibited phosphorylation of JNK but not of p38. PD98059, however, significantly augmented UVB-induced cell death earlier time points (30min - 2 h). These results indicate that ERK and JNK are activated following EGF stimulation, that might be associated with cell proliferation. On the other hand, UVB-induced apoptosis seems to be mostly associated with the activation of p38. JNK stimulation might provide an anti-apoptotic tonus during the UVB-induced, p38-associated SVHK cell death

IAP Suppression of Apoptosis Involves Distinct Mechanisms: the TAK1/JNK1 Signaling Cascade and Caspase Inhibition

“…Our data support the contention that MAP kinase activation, specifically of JNK family members, is related to protection against apoptosis (3,29,37,42,54). There is a growing consensus that if any correlation exists between activation of MAP kinases and protection or induction of apoptosis, it is stimuli and/or cell type dependent (15,22,36,52).…”

The Role of H2O2as a Mediator of UVB-induced Apoptosis in Keratinocytes

“…These results are consistent with another report by Gunn-Moore et al, in which it was described that ERK inhibition had no significant effect on the insulin-or brain-derived neurotrophic factor-induced survival of cerebellar granule cells (GunnMoore et al, 1997). Similarly, it was reported by Nakamura et al (Nakamura et al, 2001) that UVB-irradiation induced significant increase in the phosphorylation of p38 MAPK, but only a slight increase of ERK phosphorylation, moreover, UVB-induced cell death was not significantly affected by PD98059. These results are in accordance with the findings described here and suggest that UVB-induced apoptosis in keratinocytes is not mediated by the activation of ERK signaling pathway.…”

Mitogen-Activated Protein Kinase Activation in UV-Induced Signal Transduction

“…Many reports indicate that UVB stimulates JNKs, p38 kinase, and ERKs and activates AP-1. As with the data related to UVA exposure, there are variations in responses depending on cell type and exposure dose (87,95,(155)(156)(157). Some examples of the discrepancies are highlighted.…”

“…However, these actively proliferating cells had unusually high steady-state levels of ERK activity that were attributed to autocrine production of EGFR ligands. Another group showed that UVB (4000 J/m 2 ) stimulated the phosphorylation of p38 kinase and JNKs, but not ERKs, and that p38 kinase appeared to mediate apoptosis induced by UVB (156). Thus, as with UVA-induced signaling, UVB exposure stimulates cell type-specific signaling.…”