Cadena Del Castillo Carla E, Deniz Onur, van Geest Femke, Rosseels Lore, Stockmans Ingrid, Robciuc Marius, Carpentier Sebastien, Wölnerhanssen Bettina K, Meyer-Gerspach Anne Christin, Peterli Ralph, Hietakangas Ville, Shimobayashi Mitsugu
Clinical and Experimental Endocrinology, Department of Chronic Diseases and Metabolism, KU Leuven, Leuven, Belgium.
Faculty of Biological and Environmental Sciences, University of Helsinki, Helsinki, Finland.
Sci Adv. 2025 Mar 14;11(11):eadt4548. doi: 10.1126/sciadv.adt4548. Epub 2025 Mar 12.
Carbohydrate-responsive element binding protein (ChREBP) and Max-like protein X (MLX) form a heterodimeric transcription factor complex that couples intracellular sugar levels to carbohydrate and lipid metabolism. To promote the expression of target genes, two ChREBP-MLX heterodimers form a heterotetramer to bind a tandem element with two adjacent E-boxes, called carbohydrate-responsive element (ChoRE). How the ChREBP-MLX hetero-tetramerization is achieved and regulated remains poorly understood. Here, we show that MLX phosphorylation on an evolutionarily conserved motif is necessary for the heterotetramer formation on the ChoRE and the transcriptional activity of the ChREBP-MLX complex. We identified casein kinase 2 (CK2) and glycogen synthase kinase 3 (GSK3) as MLX kinases. High intracellular glucose-6-phosphate accumulation inhibits MLX phosphorylation and heterotetramer formation on the ChoRE, impairing ChREBP-MLX activity. Physiologically, MLX phosphorylation is necessary in to maintain sugar tolerance and lipid homeostasis. Our findings suggest that MLX phosphorylation is a key mechanism for the ChREBP-MLX heterotetramer formation to regulate carbohydrate and lipid metabolism.
碳水化合物反应元件结合蛋白（ChREBP）和Max样蛋白X（MLX）形成一种异二聚体转录因子复合物，该复合物将细胞内糖水平与碳水化合物和脂质代谢联系起来。为了促进靶基因的表达，两个ChREBP-MLX异二聚体形成一个异四聚体，以结合具有两个相邻E盒的串联元件，即碳水化合物反应元件（ChoRE）。ChREBP-MLX异四聚化是如何实现和调控的，目前仍知之甚少。在此，我们表明，在一个进化保守基序上的MLX磷酸化对于在ChoRE上形成异四聚体以及ChREBP-MLX复合物的转录活性是必需的。我们鉴定出酪蛋白激酶2（CK2）和糖原合酶激酶3（GSK3）为MLX激酶。细胞内高葡萄糖-6-磷酸积累会抑制MLX磷酸化以及在ChoRE上的异四聚体形成，从而损害ChREBP-MLX活性。在生理上，MLX磷酸化对于维持糖耐量和脂质稳态是必需的。我们的研究结果表明，MLX磷酸化是ChREBP-MLX异四聚体形成以调节碳水化合物和脂质代谢的关键机制。
