Roscovitine (Rosc) and purvalanol (Pur) are competitive inhibitors of cyclin-dependent kinases (CDKs) by targeting their ATP-binding pockets. Both drugs are shown to be effective to decrease cell viability and dysregulate the ratio of pro- and anti-apoptotic Bcl-2 family members, which finally led to apoptotic cell death in different cancer cell lines in vitro. It was well established that Bcl-2 family members have distinct roles in the regulation of other cellular processes such as endoplasmic reticulum (ER) stress. The induction of ER stress has been shown to play critical role in cell death/survival decision via autophagy or apoptosis. In this study, our aim was to investigate the molecular targets of CDK inhibitors on ER stress mechanism related to distinct cell death types in time-dependent manner in HeLa cervical cancer cells. Our results showed that Rosc and Pur decreased the cell viability, cell growth and colony formation, induced ER stress-mediated autophagy or apoptosis in time-dependent manner. Thus, we conclude that exposure of cells to CDK inhibitors induces unfolded protein response and ER stress leading to autophagy and apoptosis processes in HeLa cervical cancer cells.

Microtubule-severing protein Spastin has been shown to co-localize with actin in migratory glioblastoma cells and is linked to glioblastomas’ migration and invasion capacity. However, the effectiveness of Spastin in glioblastoma migration and the molecular mechanism underpinning the orientation of Spastin towards actin filaments remain unknown. Here, we demonstrated that Spastin plays an active role in glioblastoma migration by showing a reduced migratory potential of T98G glioblastoma cells using real-time cell analysis (RTCA) in Spastin-depleted cells. Pull-down assays revealed that a cis–trans isomerase Pin1 interacts with Spastin through binding to the phosphorylated Pin1 recognition motifs in the microtubule-binding domain (MBD), and immunocytochemistry analysis showed that interaction with Pin1 directs Spastin to actin filaments in extended cell regions. Consequently, by utilizing RTCA, we proved that the migration and invasion capacity of T98G glioblastoma cells significantly increased with the overexpression of Spastin, of which the Pin1 recognition motifs in MBD are constitutively phosphorylated, while the overexpression of phospho-mutant form did not have a significant effect on migration and invasion of T98G glioblastoma cells. These findings demonstrate that Pin1 is a novel interaction partner of Spastin, and their interaction drives Spastin to actin filaments, allowing Spastin to contribute to the glioblastomas’ migration and invasion abilities.

Glioblastoma multiforme (GBM) is one of the most common forms of brain tumor. As an excessively invasive tumor type, GBM cannot be fully cured due to its invasion ability into healthy brain tissues. Therefore, molecular mechanisms behind GBM migration and invasion need to be deeply investigated for the development of effective GBM treatments. Cellular motility and invasion are strictly associated with the cytoskeleton, especially with actins and tubulins. Palladin, an actin‐binding protein, tightly bundles actins during initial invadopodia and contraction fiber formations, which are essential for cellular motility. Spastin, a microtubule‐binding protein, cuts microtubules into small pieces and acts on invadopodia elongation and cellular trafficking of invadopodia‐associated proteins. Regulation of proteins such as spastin and palladin involved in dynamic reorganization of the cytoskeleton, are rapidly carried out by microRNAs at the posttranscriptional level. Therefore, determining possible regulatory miRNAs of spastin and palladin is critical to elucidate GBM motility. miR96 and miR182 down‐regulate SPAST and PALLD at both transcript and protein levels. Over‐expression of miR96 and miR182 resulted in inhibition of the motility. However, over‐expression of spastin and palladin induced the motility. Spastin and palladin rescue of miR96‐ or miR182‐transfected U251 MG cells resulted in diminished effects of the miRNAs and rescued the motility. Our results demonstrate that miR96 and miR182 over‐expressions inhibit GBM motility by regulating cytoskeleton through spastin and palladin. These findings suggest that miR96 and miR182 should be investigated in more detail for their potential use in GBM therapy.

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