Injection of tunicamycin induces platelet ER stress in ERp5 CKO mice. Detection of P-IRE1, IRE1, P-JNK, JNK, and XBP1s (A); (B) P-eIF2a, eIF2a, CHOP, and caspase 3 (B); and ATF6 and PDI (C) in platelets isolated from control (ERp5^fl/fl) and CKO (Pf4Cre⁺/ERp5^fl/fl) mice 24 hours after injection with DMSO (control) or tunicamycin (TN). Representative immunoblots are shown. Band densitometry of P-IRE1; P-JNK expressed as a ratio to total protein. XBP1s is expressed as a ratio to actin. P-eIF2a is expressed as a ratio to total eIF2a. CHOP, caspase 3, ATF6, and PDI are expressed as ratios to actin in control (gray) and KO (red) platelets after injection of DMSO (light box) and TN (dark box). Ratios are presented as fold change over DMSO-treated controls. n = 3 to 4 mice per genotype, mean ± SEM, 1-way ANOVA with Dunn post hoc analysis. ∗∗P < .005, ∗P < .05.