Engineering overexpressing SYNGR1 inhibited the progression of GBM cells by suppressing the intracellular FGF1-mediated LDs accumulation and cytoskeleton remodeling.

BACKGROUND

Glioblastoma (GBM) is the most common and aggressive glioma subtype in adults, characterized by disrupted lipid homeostasis. The accumulation of lipid droplets (LDs) is involved in the actin cytoskeleton remodeling in different types of cells, the intracellular fibroblast growth factor 1 (FGF1) plays an important role in this process. The stability of cytoskeleton is crucial for the proliferation, invasion and other malignant behavior of GBM. The synaptic gyrus protein 1 (synaptogyrin 1, SYNGR1) is closely correlated with the progression of various tumours, but there have been no reports of research in the field of glioma. This research was conducted to investigate whether the overexpression of SYNGR1 was involved in regulating the malignant biological behaviour of GBM cells and its potential regulatory mechanism, especially whether the LDs accumulation is involved in the remodeling of the actin cytoskeleton in GBM cells.

METHODS

The UCSC Xena database and GEPIA database were used to analyze the correlation between the expression level of SYNGR1 and the survival time of glioma patients. Engineering Lentiviruses were used to establish cells with stable overexpression of SYNGR1, FGF1, or both. The proliferation, invasion, and cytoskeleton of glioma cells (U251, LN229, U118) were detected by cell counting kit-8 (CCK8), 5-ethynyl-2'-deoxyuridine (EdU), immunofluorescence(IF), colony formation, adhesion, and transwell assays. Intracellular LDs were detected by the lipid droplet red fluorescence assay with Nile red. The cell cycle distribution and apoptosis rate of the cells were assessed using flow cytometry analysis. Bioinformatics analysis, IF, RNA sequencing, and western blot analysis were used to measure the expression levels of target proteins. The protein from HA and HT22 cell lines served as control was detected by western blot analysis. The Gl261 cell line and C57BL/6 mouse were used to construct C57BL/6 mouse glioblastoma model. Animal MRI was used to examine tumor size.

RESULTS

SYNGR1 expression was significantly reduced in GBM. Overexpression of SYNGR1 significantly inhibited the LDs accumulation, proliferation, invasion, adhesion, and other malignant processes in GBM cells in vitro. Moreover, SYNGRI overexpression inhibited the growth of intracranial gliomas in vivo and prolonged survival of C57BL/6 model mice. Mechanistic exploration revealed that the overexpression of SYNGR1 had an antiglioma effect by inhibiting the LDs accumulation and remodeling the cytoskeleton via the downregulation of the intracellular FGF1, while FGF1 overexpression could reverse the antiglioma effect of SYNGR1.

CONCLUSIONS

The intracellular FGF1 played an important role in maintaining the homeostasis of LDs and the actin cytoskeleton, which promoted the malignant progression of GBM cells. Engineering overexpressing SYNGR1 could effectively inhibit the malignant biological behaviors, such as the proliferation, adhesion, and invasion, as well as promote the apoptosis of glioma cells by suppressing the intracellular FGF1-mediated LDs accumulation and cytoskeleton remodeling.