FIGURE 3.

Endogenous iPLA₂γ amplifies ATF6 activity and ER chaperones. A, WT and iPLA₂γ KO mouse GECs were co-transfected with ATF6 firefly luciferase-reporter and Renilla luciferase. Cells were untreated (Untr), or incubated with tunicamycin (Tm, 0.1 μg/ml, 18 h). Tunicamycin-induced activation of ATF6 reporter was greater in WT cells, compared with iPLA₂γ KO. *, p < 0.001 Tm versus untreated (WT); **, p < 0.001 WT versus KO (Tm), four experiments performed in triplicate. RLU, relative luminescence units. B, WT and iPLA₂γ KO mouse GECs were untreated or incubated with Tm (0.5 or 5 μg/ml for 6 h). Lysates were immunoblotted with antibodies to GRP94, GRP78, and actin. Tunicamycin increased GRP94 and GRP78 expression levels only in WT podocytes. B, representative immunoblots; C and D, densitometric quantification. C, GRP94: *, p < 0.01; **, p < 0.001 Tm versus untreated; +, p < 0.01 WT versus KO (Tm 5), six experiments performed in duplicate. D, GRP78: *, p < 0.001 Tm versus untreated; **, p < 0.05 WT versus KO (Tm 5), five experiments performed in duplicate.