UC San Diego

The endoplasmic reticulum (ER) is the site of lipid biosynthesis and secretory protein folding, which must be adjusted to accommodate the physiological needs and stresses of the cell. Since ER cannot be made de novo, it must be inherited faithfully. During decreased ER function cortical ER and cell cycle progression are delayed by the ER surveillance (ERSU) pathway, which is mediated by the MAP kinase Slt2. We have identified the mechanism through which the accumulation of unfolded proteins, ER stress, activates Slt2. This response is separate from the canonical ER stress response, the unfolded protein response (UPR). Furthermore, this mechanism is distinct from the cell wall integrity (CWI) pathway, the canonical Slt2 activation pathway. Activated Slt2 has many cytoplasmic and nuclear targets, including the transcription factor Rlm1. We find that Rlm1 aids in cell survival during conditions of decreased ER function, but does not play a role in the ERSU pathway