The Unfolded Protein Response Sensor PERK Mediates Stiffness-Dependent Adaptation in Glioblastoma Cells

Abstract

Glioblastoma multiforme (GBM) is the most aggressive brain tumor in adults. In addition to genetic causes, the tumor microenvironment (TME), including stiffening of the extracellular matrix (ECM), is a main driver of GBM progression. Mechano-transduction and the unfolded protein response (UPR) are essential for tumor-cell adaptation to harsh TME conditions. Here, we studied the effect of a variable stiff ECM on the morphology and malignant properties of GBM stem cells (GSCs) and, moreover, examined the possible involvement of the UPR sensor PERK herein. For this, stiffness-tunable human blood plasma (HBP)/alginate hydrogels were generated to mimic ECM stiffening. GSCs showed stiffness-dependent adaptation characterized by elongated morphology, increased proliferation, and motility which was accompanied by F-Actin cytoskeletal remodeling. Interestingly, in PERK-deficient GSCs, stiffness adaptation was severely impaired, which was evidenced by low F-Actin levels, the absence of F-Actin remodeling, and decreased cell proliferation and migration. This impairment could be linked with Filamin-A (FLN-A) expression, a known interactor of PERK, which was strongly reduced in PERK-deficient GSCs. In conclusion, we identified a novel PERK/FLNA/F-Actin mechano-adaptive mechanism and found a new function for PERK in the cellular adaptation to ECM stiffening.

The Unfolded Protein Response Sensor PERK Mediates Mechanical Stress-induced Maturation of Focal Adhesion Complexes in Glioblastoma Cells

“…On the other hand, disruption of F-Actin polymerization by Latrunculin B treatment also impaired stiffness dependent adaptation of GG16-WT cells, and strongly reduced GFAP expression thus mimicking the PERK-KO phenotype (Supplementary Figure S1). As controls, stiffness dependent increases of FLNA and F-Actin seen in WT cells was disrupted in PERK deficient cells (Supplementary Figure S2 and S3), in agreement with our earlier findings [35].…”

“…Recently, we reported that the endoplasmic reticulum (ER) stress and unfolded protein response (UPR) sensor PKR-like ER kinase (PERK) mediates an adaptive cellular response in GSCs towards increasing substrate/ECM stiffness mimicked by stiffness tunable hydrogels [35]. PERK is known to have both a kinase function and a protein scaffold function by which it regulates a number of cellular processes that have been related either to restoring proteostasis, or to regulate F-Actin remodeling in order to facilitate ER – cell membrane interaction for maintaining calcium homeostasis [36,37].…”

“…PERK is known to have both a kinase function and a protein scaffold function by which it regulates a number of cellular processes that have been related either to restoring proteostasis, or to regulate F-Actin remodeling in order to facilitate ER – cell membrane interaction for maintaining calcium homeostasis [36,37]. The latter involves PERK-FLNA interactions, FLNA being a regulator of F-Actin remodeling, a mechanism which we recently identified to be involved in stiffness dependent increases in F-Actin polymerization in GSCs, which was associated with cell elongation and increased cell proliferation and migration [35,36]. However, the potential involvement of PERK in sensing alterations in ECM stiffening by GSCs remains unknown.…”

“…Here, we examined if PERK is connected to FAC formation and thus in sensing and mediating cellular responses to alterations in ECM stiffness. Human blood plasma/alginate hydrogels with tunable stiffness were used to mimic brain ECM stiffening in GB [35]. The expression of different components of the FAC in patient-derived GSCs was studied in relation to substrate stiffness.…”

Classification related to immunogenic cell death predicts prognosis, immune microenvironment characteristics, and response to immunotherapy in lower-grade gliomas

“…Nevertheless, in certain circumstances, GBM may experience immune flight through not rendering neoplastic antigens or MHC-1, thereby blocking recognition by CD8-positive T-cells ( 42 , 43 ). EIF2AK3, best known as PERK, was reported to promote glioma cell viability, migration, and anti-apoptosis in vitro ( 44 , 45 ). Our in vitro experiments also confirmed that the expression level of EIF2AK3 elevated with an increase in tumor grade, and EIF2AK3 enhances the abilities of tumor cell proliferation and migration.…”