Skip to main content
. 2009 Nov 16;187(4):525–536. doi: 10.1083/jcb.200907074

Figure 7.

Figure 7.

ER membrane expansion alleviates stress as a result of increased ER size rather than altered ER shape. (A) Rtn1 levels are unchanged by ER stress or activation of Ino2/4. Western blot of Cherry tag from Rtn1-Cherry–expressing wild-type cells treated with DTT for up to 4 h and from untreated Rtn1-Cherry–expressing wild-type, opi1Δ, and ino2(L119A) cells (SSY421, SSY478, and SSY473). Pgk1 served as a loading control. (B) Quantification of Western blots shown in A with values normalized to Pgk1. (C) Overexpression of Rtn1 converts sheets (arrows) into tubules (arrowheads). Untreated wild-type and opi1Δ cells expressing dsRed-HDEL and Rtn1-GFP were used to mark the entire ER lumen and ER tubules, respectively, and carrying an empty vector or an expression plasmid encoding untagged Rtn1 (SSY523, SSY531, and SSY532). (D) ER expansion is unaffected by Rtn1 overexpression. Quantification of ER expansion from images of untreated wild-type, opi1Δ, and Rtn1-overexpressing opi1Δ cells (SSY523, SSY531, and SSY532). Statistical significance compared with wild-type cells of P ≤ 10−6 (***) is shown. Error bars indicate SEM. (E) Rtn1 overexpression does not affect sensitivity to ER stress. Tunicamycin sensitivity of wild-type, hac1Δ, and hac1Δ opi1Δ cells carrying empty vectors and hac1Δ opi1Δ cells carrying an expression plasmid encoding untagged Rtn1 (SSY510, SSY533, SSY535, and SSY536) as assessed by plating dilution series of cells onto solid SC medium (without uracil) containing 0.05 µg/ml tunicamycin. Series represent fivefold dilutions from one step to the next. Bar, 2 µm.