Yeast cells sense alterations in the plasma membrane (PM) lipid asymmetry and external alkalization by the sensor protein Rim21, which functions in the Rim101 pathway. Rim101 signaling is initiated at the PM by the recruitment of the Rim101 signaling complex. The PM physically associates with the cortical endoplasmic reticulum (ER) to form ER–PM contact sites, where several signaling events, lipid exchange, and ion transport take place. In the present study, we investigated the spatial relationship between ER–PM contact sites and the sites of Rim101 signaling. Rim101 signaling mostly proceeds outside ER–PM contact sites in the PM and did not require intact ER–PM contact for its activation. Rather, the Rim101 pathway was constitutively activated by ER–PM contact site disruption, which is known to cause ER stress. ER stress induced by tunicamycin treatment activated the Rim101 pathway. Furthermore, the sensitivity of cells to tunicamycin without ER–PM contact was considerably elevated by the deletion of RIM21. These results suggest that the Rim101 pathway is important for the adaptation to ER stress by compensating for alterations in PM lipid asymmetry induced by ER stress.
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Cover Image
Cover Image
Structure of the molybdenum insertase Cnx1E domain from the higher plant Arabidopsis thaliana. The structure was solved in complex with molybdate and magnesium ions by X-ray crystallography. Mutational studies identifi ed Cnx1E dimer formation to be essential for substrate binding and hence for the reaction of adenylated molybdopterin (left) and molybdate (center) to molybdenum cofactor (right). For more information see see pp. 163–178 in this issue. Image provided by J. Krausze, W. A. Sassen and T. Kruse
The Rim101 pathway contributes to ER stress adaptation through sensing the state of plasma membrane
Keisuke Obara, Akio Kihara; The Rim101 pathway contributes to ER stress adaptation through sensing the state of plasma membrane. Biochem J 1 January 2017; 474 (1): 51–63. doi: https://doi.org/10.1042/BCJ20160580
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