RESUMO
Leukoencephalopathy with vanishing white matter (VWM) is one of the most prevalent inherited white matter disorders in childhood, and it's the only known hereditary human disease due to the direct defects in protein synthesis process, with the gene defects in EIF2B1-5, encoding the five subunits of eukaryotic translation initiation factor (eIF2B alpha, beta, gamma, delta and epsilon ) respectively. eIF2B is essential for the protein translation initiation process, and its action is realized via eukaryotic translation initiation factor2 (eIF2). Phosphorylation of eIF2alpha and eIF2Bepsilon is an important way to regulate eIF2B function, and thus play a key role in control of the protein translation level under physiological condition. Mutant eIF2B results in functional defects and decrease of the overall protein translation in cells, but in increase the translation of proteins with multiple upstream open reading frames, such as activating transcription factor 4 (AFT4), which leads to the susceptibility to unfolded protein response under stress, and the following apoptosis. The exact pathogenic mechanisms of VWM are far from well understood. It's suggested that level of AFT4 in cells with eIF2B mutations is higher than in wild type cells under physiological condition, which makes the mutant cells more susceptible to endoplasmic reticulum (ER) stress and unfolded protein response (UPR). Under stress, the defect eIF2B leads to a vicious cycle of UPR activation, which may underlie the neurological aggravation in VWM patients after minor stress, a specific clinical feature of VWM. Elucidating the pathogenesis of VWM will be helpful to further understand the protein translation process in eukaryotic cells, and provide a clue for possible therapeutic targets and treatment strategies in the future.
