7-hydroxy-4-Methyl-2-oxo-2H-1-Benzopyran-8-carboxaldehyde

4μ8C (14003-96-4) is a selective inhibitor of IRE1α ribonuclease (RNase) activity (IC50= 60 nM). Covalently binds to lysine 907 in the IRE1 endonuclease domain, blocking substrate access to the active site of IRE1α and inactivating both XBP1 splicing and IRE1α-mediated mRNA degradation but not IRE1 kinase activity.1Inhibits IRE1α in response to hypoxia or other ER stress-inducing agents but has no effect on proliferation or clonogenic survival of hypoxic cells.2Blocks production of IL-4, IL-5 and IL-13 production in T cells.34μ8C prevents the splicing of the XBP1 mRNA in response to ER stress caused by mutant proinsulin production in pancreatic β-cells.4

8-Formyl-4-methylumbelliferone is an inhibitor that blocks substrate access to the active site of IRE1 and selectively inactivates both Xbp1 splicing and IRE1-mediated mRNA degradation.

A cell-permeable coumarin o-hydroxyaldehyde compound that inhibits IRE1 RNase activity in a time- and dose-dependent manner (IC₅₀ = 550, 230, 180, 100, and 45 nM, respectively, with 0, 2, 4, 8, 16, min drug preincubation in FRET-based RNA cleavage assays) by covalently targeting IRE1 Lys907 via Schiff base formation, effectively preventing ER stress-induced site-specific mRNA splicing as well as RIDD (Regulated IRE1-Dependent Degradation) mRNA degradation (IC₅₀ = 6.9 and 4.1 μM, respectively, against Xbp1 splicing and Scara3 degradation) in MEF cultures following Tunicamycin (Cat. No. 654380) treatment. Also demonstrated to inhibit ER capacity expansion (Effective conc. 32 μM) and amylase secretion (IC₅₀<2 μM) upon stress induction by Dexamethasone (Cat. No. 265005) treatment in rat AR42J tumoral acinar pancreatic cells. Structural analysis reveals that the reduced water accessibility to Lys907 in IRE1 native conformation accounts for the unusual stability of Lys907 Schiff base formation and forms the basis of selective IRE1 RNase inhibition by 4μ8C and STF083010 (Cat. No. 412510). Although 4μ8C, but not STF083010, is also shown to inhibit IRE1 autophosphorylation by Schiff base formation with IRE1 Lys599 in the absence of ADP, cellular nucleotide prevents 4μ8C from targeting IRE1 Lys599 and inhibiting IRE1 kinase activity intracellularly.

Cell permeable: yes

Store at -20°C

[1] BENEDICT C S CROSS. The molecular basis for selective inhibition of unconventional mRNA splicing by an IRE1-binding small molecule.[J]. Proceedings of the National Academy of Sciences of the United States of America, 2012: E869-78. DOI:10.1073/pnas.1115623109
[2] DAN COJOCARI . New small molecule inhibitors of UPR activation demonstrate that PERK, but not IRE1α signaling is essential for promoting adaptation and survival to hypoxia[J]. Radiotherapy and Oncology, 2013, 108 3: Pages 541-547. DOI:10.1016/j.radonc.2013.06.005
[3] KYEORDA L KEMP. The serine-threonine kinase inositol-requiring enzyme 1α (IRE1α) promotes IL-4 production in T helper cells.[J]. The Journal of Biological Chemistry, 2013: 33272-33282. DOI:10.1074/jbc.m113.493171
[4] LILING ZHANG. IRE1 inhibition perturbs the unfolded protein response in a pancreatic β-cell line expressing mutant proinsulin, but does not sensitize the cells to apoptosis.[J]. BMC Cell Biology, 2014, 15: 29. DOI:10.1186/1471-2121-15-29