A Crucial Role for RACK1 in the Regulation of Glucose-Stimulated IRE1α Activation in Pancreatic β Cells

Yifu Qiu, Ting Mao, Yongliang Zhang, Mengle Shao, Jia You, Qiurong Ding, Yan Chen, Dongmei Wu, Dong Xie, Xu Lin, Xiang Gao, Randal J. Kaufman, Wenjun Li,* Yong Liu*

*To whom correspondence should be addressed. E-mail: liuy{at}sibs.ac.cn (Y.L.) and wjli{at}sibs.ac.cn (W.L.)

This PDF file includes:

• Materials and Methods
• Fig. S1. RACK1 associates with IRE1α in transfected HEK 293T cells.
• Fig. S2. High glucose stimulation does not trigger typical ER stress–activated UPR pathways.
• Fig. S3. Glucose-stimulated phosphorylation does not cause an electrophoretic shift of the IRE1α protein.
• Fig. S4. Palmitate and insulin do not affect IRE1α phosphorylation.
• Fig. S5. Glucose metabolism and intracellular calcium mobilization are required for glucose stimulation of IRE1α phosphorylation and IRE1α-RACK1 interaction in β cells.
• Fig. S6. The structural requirements for the interaction of IRE1α with RACK1.
• Fig. S7. Physical IRE1α-RACK1 interaction requires the linker region of IRE1α.
• Fig. S8. Effects of RACK1 on ER stress–induced IRE1α phosphorylation and Xbp1 splicing in β cells.
• Fig. S9. Prolonged exposure to high glucose, like ER stress, reduces the abundance of Insulin mRNA in β cells.
• Fig. S10. Quantification of IRE1α phosphorylation in INS-1 cells and primary islets.
• Fig. S11. Autophosphorylation of overexpressed IRE1α, RACK1 overexpression, or RACK1 knockdown does not affect Insulin mRNA abundance in INS-1 β cells.
• Fig. S12. Effects of adenoviral overexpression of IRE1α or RACK1 or knockdown of RACK1 on glucose-stimulated insulin secretion in INS-1 β cells.
• Fig. S13. Decreased Rack1 mRNA abundance and the effect of RACK1 overexpression on Insulin mRNA abundance in islets from db/db mice.
• Fig. S14. Increased IRE1α phosphorylation, decreased RACK1 abundance, and enhanced activation of the IRE1α arm of the UPR in db/db islets.
• Fig. S15. Analysis of the effect of adenoviral infections on the viability of INS-1 β cells.
• References

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