Kar2p availability defines distinct forms of endoplasmic reticulum stress in living cells

The endoplasmic reticulum (ER) unfolded protein response (UPR) is correlated with changes in unfolded secretory levels. A novel fluorescence biosensor now reports changes in the unfolded protein burden. This reporter reveals a form of ER stress—inositol withdrawal—that stimulates the UPR without changes in unfolded protein levels.

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