Fig. 6: iRhoms control BCL-2 antiapoptotic effect on IP3Rs.
From: iRhom pseudoproteases regulate ER stress-induced cell death through IP3 receptors and BCL-2
a Cell lysates from WT and iRhom1/2 DKO MEFs treated with tunicamycin (0.5 µg/ml) alone or in the presence of BIRD-2 (10 µM) or ABT-199/Venetoclax (ABT, 1 µM) were analysed by immunoblotting with indicated antibodies. b Levels of iRhom2 and endogenous IP3R1, IP3R3 and BCL-2 were analysed by immunoblotting in whole cell lysate (WCL) and immunoprecipitation (IP: HA) from iRhom1/2 DKO MEFs stably expressing iRhom2-HA after treatment for 18 h with control or BIRD-2 peptides (10 µM or 20 µM). c, d Levels of iRhom2, IP3R1 and BCL-2 were analysed by immunoblotting in whole cell lysate (WCL) and immunoprecipitation (IP: FLAG) from HEK293T cells transiently transfected for 36 h with FLAG-IP3R1 (1.25 µg), iRhom2-HA (0.25 µg) and VENUS-BCL-2_ER (0.25 µg; BCL-2 targeted specifically to ER) in (c) or GFP-IP3R1 (1.25 µg), iRhom2-HA (0.25 µg) and FLAG-BCL-2_ER (0.25 µg; Bcl-2 targeted specifically to ER) in (d). Immunoblotting data are representative of 2–3 independent experiments. e Proposed model for the role of iRhoms in regulating IP3R function via BCL-2. In WT cells, IP3R, iRhoms and BCL-2 interact at the ER within a regulatory complex, where iRhom2 attenuates the inhibitory effect of BCL-2 on IP3R activity. This enhances the flow of Ca2+ from the ER into mitochondria under basal conditions and during acute release of Ca2+ (e.g. ER stress) to regulate apoptosis. In the absence of iRhoms, the inhibitory effect of BCL-2 on IP3Rs is maintained, thereby reducing ER-mitochondrial Ca2+ transfer and enhancing cell survival. Source data are provided as a Source data file.
