Abnormal expression of CUX1 influences autophagy activation in paroxysmal nocturnal hemoglobinuria

Abstract The mechanism underlying autophagy in paroxysmal nocturnal hemoglobinuria (PNH) remains largely unknown. We previously sequenced the entire genome exon of the CD59– cells from 13 patients with PNH and found genes such as CUX1 encoding Cut-like homeobox 1. Peripheral blood samples from nine patients with PNH and seven healthy controls were obtained to measure CUX1 expression. The correlation between CUX1 mRNA expression and PNH clinical indicators was analyzed. To simulate CUX1 expression in patients with PNH, we generated a panel of PNH cell lines by knocking out PIGA in K562 cell lines and transfected lentivirus with CUX1. CCK-8 and EDU assay assessed cell proliferation. Western blotting was used to detect Beclin1, LC3A, LC3B, ULK1, PI3K, AKT, p-AKT, mTOR, and p-mTOR protein levels. Autophagosomes were observed with transmission electron microscopy. Chloroquine was used to observe CUX1 expression in PNH after autophagy inhibition. Leukocytes from patients with PNH had lower levels of CUX1 mRNA expression and protein content than healthy controls. The lactose dehydrogenase level and the percentage of PNH clones were negatively correlated with CUX1 relative expression. We reduced CUX1 expression in a PIGA-knockout K562 cell line, leading to increased cell proliferation. Levels of autophagy markers Beclin1, LC3B, LC3A and ULK1 increased, and autophagosomes increased. Furthermore, PI3K/AKT/mTOR protein phosphorylation levels were lower. CUX1 expression did not change and cell proliferation decreased in CUX1 knocked down PNH cells after inhibition of autophagy by chloroquine. In brief, CUX1 loss-of-function mutation resulted in stronger autophagy in PNH.