GPIb-IX complex is sensitive to ER stress. (A) Western blot for indicated proteins in primary megakaryocytes from WT and KO mice. (B) Effect of ER stress on the expression level of cell-surface GPIb-IX complex. Flow cytometry for GPIbα (AK2) expression after Ib9-IX cells were treated with the ER stressors thapsigargin (THAPS), antimycin A (ANT), brefeldin A (BFA), or tunicamycin (TUN) or left untreated. Isotype staining is shown. Numbers represents mean fluorescence intensity. Data are representative of 2 independent experiments. (C) Western blot for GPIbα, GPIbβ, and GPIX expression in Ib9-IX cells after indicated treatments. (D) GPIX is degraded in response to ER stress. Western blot analysis for GPIX subunit expression in thapsigargin-exposed Ib9-IX cells after cotreatment with kifunensine (KIFU) and chloroquine (CLQ). Vertical lines have been inserted to indicate a repositioned gel lane. Data are representative of 2 independent experiments.