The Membrane Stress Response Buffers Lethal Effects of Lipid Disequilibrium by Reprogramming the Protein Homeostasis Network

Lipid composition can differ widely among organelles and even between leaflets of a membrane. Lipid homeostasis is critical because disequilibrium can have disease outcomes. Despite their importance, mechanisms maintaining lipid homeostasis remain poorly understood. Here, we establish a model system to study the global effects of lipid imbalance. Quantitative lipid profiling was integral to monitor changes to lipid composition and for system validation. Applying global transcriptional and proteomic analyses, a dramatically altered biochemical landscape was revealed from adaptive cells. The resulting composite regulation we term the ?membrane stress response? (MSR) confers compensation, not through restoration of lipid composition, but by remodeling the protein homeostasis network. To validate its physiological significance, we analyzed the unfolded protein response (UPR), one facet of the MSR and a key regulator of protein homeostasis. We demonstrate that the UPR maintains protein biogenesis, quality control, and membrane integrity?functions otherwise lethally compromised in lipid dysregulated cells. Genes expression from early log phase of CHO2, OPI3, and PAH1 knockout cell and untreated and DTT-treated WT cells. RNA was prepared from independent triplicate samples. Array sets performed and collected on different dates are as follows: Array 1, Day 1: WT_rep1 pah1_rep1 cho2_rep1 opi3_rep1 Array 2, Day 2: WT_rep2 WT_rep3 WT_Tm_rep1 WT_DTT_rep1 Array 3, Day 2: WT_DTT_rep2 WT_DTT_rep3 cho2_rep2 cho2_rep3 Array 4, Day 2: pah1_rep2 pah1_rep3 opi3_rep2 opi3_rep3