Fig. 7: XBP1s promotes LIPT1 ubiquitination and alters glycolysis and mitochondrial respiration. | Cell Death & Disease

Fig. 7: XBP1s promotes LIPT1 ubiquitination and alters glycolysis and mitochondrial respiration.

From: Endoplasmic reticulum stress related super-enhancers suppress cuproptosis via glycolysis reprogramming in lung adenocarcinoma

Fig. 7

A Volcano plot showing differential protein expression profiles in A549 cells overexpressing XBP1s (XBP1s-OE) compared to the expression vector (EV) control after treatment with 40 nM ES. Red and green dots represent significantly upregulated and downregulated proteins, respectively (log2FC > 1.5, -log10 p-value > 1.3). Notably, LIPT1 is significantly downregulated. B KEGG pathway enrichment analysis of significantly altered proteins, highlighting activated glycolysis, ubiquitin-mediated proteolysis, and pyruvate metabolism pathways. C Western blot (WB) and quantitative PCR (qPCR) analyses of LIPT1 and XBP1s expression in LUAD cells with XBP1s overexpression (OE) compared to EV. LIPT1 protein levels are reduced in XBP1s-OE cells, while mRNA levels remain unchanged. β-actin was used as a loading control. D Immunoprecipitation (IP) assay demonstrating enhanced ubiquitination of LIPT1 in the presence of XBP1s in LUAD cells. Cells were treated with MG132 to inhibit proteasomal degradation. Flag-LIPT1, Myc-XBP1s, and HA-Ub were co-expressed, and ubiquitinated LIPT1 was detected using anti-HA antibodies. E Lactic acid and pyruvic acid levels in LUAD cells overexpressing LIPT1. Overexpression of LIPT1 reduces both metabolites (n = 3). F Lactic acid and pyruvic acid levels in LUAD cells with XBP1s overexpression (OE) or rescue of LIPT1 expression (Rescue). XBP1s-OE increases glycolysis metabolites, while LIPT1 rescue reduces their levels (n = 3). Data are shown as mean ± SD, *P < 0.05, **P < 0.01, ***P < 0.001, ***P < 0.0001, ns not significant. G Extracellular acidification rate (ECAR) measurements in LUAD cells. XBP1s-OE enhances glycolysis, while LIPT1 rescue reverses the effect. Shaded areas indicate glycolytic function after oligomycin addition. Data are presented as mean ± SD. H Oxygen consumption rate (OCR) analysis of mitochondrial respiration in LUAD cells. XBP1s-OE suppresses mitochondrial respiration, while LIPT1 rescue restores respiration levels. OCR values after sequential addition of oligomycin, FCCP, and antimycin A/rotenone are shown. Data are presented as mean ± SD.

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