Neuronal precursor cell-expressed developmentally down-regulated 4-1 (NEDD4-1) plays a great role in tumor cell growth, but its function and mechanism in cell invasive behavior are totally unknown. Here we report that NEDD4-1 regulates migration and invasion of malignant glioma cells via triggering ubiquitination of cyclic nucleotide Ras guanine nucleotide exchange factor (CNrasGEF) using cultured glioma cells. NEDD4-1 overexpression promoted cell migration and invasion, while its downregulation specifically inhibited them. However, NEDD4-1 did not affect the proliferation and apoptosis of glioma cells. NEDD4-1 physically interacted with CNrasGEF and promoted its poly-ubiquitination and degradation. Contrary to the effect of NEDD4-1, CNrasGEF downregulation promoted cell migration and invasion, while its overexpression inhibited them. Importantly, downregulation of CNrasGEF facilitated the effect of NEDD4-1-induced cell migration and invasion. Interestingly, aberrant up-regulated NEDD4-1 showed reverse correlation with CNrasGEF protein level but not with its mRNA level in glioma tissues. Combined with the in vitro results, the result of glioma tissues indicated post-translationally modification effect of NEDD4-1 on CNrasGEF. Our study suggests that NEDD4-1 regulates cell migration and invasion through ubiquitination of CNrasGEF in vitro.

Glioblastoma (GBM) is a malignant tumor prone to recurrence and resistant to conventional therapies. GBM cells show high autophagy activity, contributing to its rapid progression. Casein kinase 1 family, such as Casein kinase 1α (CK1α), has shown its effect on autophagy by binding to the hypoxia-inducible factor-1α (HIF-1α). This study investigates the expression of CK1α and HIF-1α in healthy and GBM tissues and its relations with autophagy-related genes and GBM cell viability. The expressions of CK1α, HIF-1α, and autophagy-related proteins in normal tissues, GBM tissues, and GBM cell lines (U87MG, U251, U118-MG, LN229, SHG44) were analyzed by qRT-PCR and Western blotting. In vitro, the U87MG cell line was transfected with pcDNA3.1-CK1α to enhance the expression of CK1α or both pcDNA3.1-CK1α and siRNA-HIF-1α. The expression of CK1α, HIF-1α, and autophagy-related proteins in GBM brain tissues and cell lines was higher than in normal brain tissues. In U87MG cells, enhanced CK1α expression upregulated the expression of HIF-1α and autophagy-related proteins and promoted cell proliferation. Inhibiting the expression of HIF-1α reduced the expression of autophagy-related proteins and decreased U87MG cell viability. Overexpressed CK1α positively regulates autophagy activity through the HIF-1α pathway. Inhibition of CK1α might be a potential therapeutic approach for glioblastoma therapy.