Figure 5.

UV-induced release of ER calcium is responsible for TG2 activation. (a and b) HaCaT cells were pretreated with 20 μM U73122 or U73343 (a, n=3) and with 100 μM 2-aminoethyl diphenylborinate (2-APB) (b, n=3), and then exposed to UV irradiation (10 mJ/cm²). After 6 h, levels of in situ TG activity and mRNA for TNF-α, IL-6, and IL-8 were measured by the BP incorporation assay and QRT-PCR, respectively. (c and d) Effect of thapsigargin (500 nM) on in situ TG activity in HaCaT cells (c, n=3) and the expression of cytokines (d, n=3) or in primary epidermal keratinocytes prepared from WT and TG2^−/− littermates. All data are represented as mean±SEM. *P<0.05; **P<0.01; ***P<0.001