Roles of Layilin in Regulation of Low-Density Lipoprotein Receptor in Malignant Glioma Cells

Objective: Layilin is a type I transmembrane protein that possesses a C-type lectin motif in its extracellular domain, and whose functions have not yet been completely understood. Previously, we reported that layilin was highly expressed in malignant glioma cells. In this study, we investigated whether layilin was functionally related to low-density lipoprotein receptor (LDLR) in malignant glioma cells because one of the characteristics of malignant glioma cells is the high expression of LDLR.Methods: Under layilin-knockdown (KD) conditions in A172 cells, a malignant glioma cell line, we measured LDLR mRNA and protein levels by quantitative polymerase chain reaction and western blotting, respectively. Furthermore, we measured LDL uptake in layilin-KD cells by LDL uptake assay.Results: Even though the amounts of mRNA for LDLR were unaffected by layilin-KD, the amounts of LDLR protein were significantly increased by layilin-KD 48 h after transfection with small interfering RNAs for layilin (p<0.05). Accordingly, LDL uptake was increased by layilin-KD (p<0.05).Conclusion: Our data suggest a novel function of layilin, that is, down-regulation of LDLR at the protein level.