Glioma Cell Proliferation Controlled by ERK Activity-Dependent Surface Expression of PDGFRA

Abstract

Increased PDGFRA signaling is an essential pathogenic factor in many subtypes of gliomas. In this context the cell surface expression of PDGFRA is an important determinant of ligand sensing in the glioma microenvironment. However, the regulation of spatial distribution of PDGFRA in glioma cells remains poorly characterized. Here, we report that cell surface PDGFRA expression in gliomas is negatively regulated by an ERK-dependent mechanism, resulting in reduced proliferation of glioma cells. Glioma tumor tissues and their corresponding cell lines were isolated from 14 patients and analyzed by single-cell imaging and flow cytometry. In both cell lines and their corresponding tumor samples, glioma cell proliferation correlated with the extent of surface expression of PDGFRA. High levels of surface PDGFRA also correlated to high tubulin expression in glioma tumor tissue in vivo. In glioma cell lines, surface PDGFRA declined following treatment with inhibitors of tubulin, actin and dynamin. Screening of a panel of small molecule compounds identified the MEK inhibitor U0126 as a potent inhibitor of surface PDGFRA expression. Importantly, U0126 inhibited surface expression in a reversible, dose- and time-dependent manner, without affecting general PDGFRA expression. Treatment with U0126 resulted in reduced co-localization between PDGFRA and intracellular trafficking molecules e.g. clathrin, RAB11 and early endosomal antigen-1, in parallel with enhanced co-localization between PDGFRA and the Golgi cisternae maker, Giantin, suggesting a deviation of PDGFRA from the endosomal trafficking and recycling compartment, to the Golgi network. Furthermore, U0126 treatment in glioma cells induced an initial inhibition of ERK1/2 phosphorylation, followed by up-regulated ERK1/2 phosphorylation concomitant with diminished surface expression of PDGFRA. Finally, down-regulation of surface PDGFRA expression by U0126 is concordant with reduced glioma cell proliferation. These findings suggest that manipulation of spatial expression of PDGFRA can potentially be used to combat gliomas.

Platelet‐derived growth factor (PDGF) signalling in cancer: rapidly emerging signalling landscape

“…Initially, a decline was noted in phosphorylated levels of ERK; however, phospho-ERK levels were notably enhanced between 3 and 18 h of U0126 treatment in the glioma cell lines. 12,13 Downstream of kinase 1 (DOK1) is overexpressed in different glioma cancer cell lines and has been shown to undergo tyrosine phosphorylation in PDGF-BB-treated glioma cells. Detailed mechanistic insights revealed that phosphorylation of p130Cas at tyrosine residues and activation of Rap1 were impaired in DOK1-silenced or DOK1 mutant expressing glioma cells.…”

“…36 There is an exciting piece of evidence suggesting that miR-34a negatively regulates PDGFRβ in cultured rat mesangial cells. 12,13 Likewise, NSCLC cells have downregulated miR-34a/c and upregulated PDGFRα/β that impaired TRAIL-mediated apoptosis. It was further suggested that gene silencing of PDGFRα/β or overexpression of miR-34a/c in NSCLC cells restored TRAIL-induced apoptosis.…”

“…miR‐34a‐mediated repression of PDGFR and MET considerably reduced pAkt levels in AGS cells . There is an exciting piece of evidence suggesting that miR‐34a negatively regulates PDGFR β in cultured rat mesangial cells . Likewise, NSCLC cells have downregulated miR‐34a/c and upregulated PDGFR α / β that impaired TRAIL‐mediated apoptosis.…”

“…MAPK/ERK kinase (MEK) inhibitor U0126 has been reported to potently inhibit cell surface expression of PDGFR‐A time dependently. Initially, a decline was noted in phosphorylated levels of ERK; however, phospho‐ERK levels were notably enhanced between 3 and 18 h of U0126 treatment in the glioma cell lines . Downstream of kinase 1 (DOK1) is overexpressed in different glioma cancer cell lines and has been shown to undergo tyrosine phosphorylation in PDGF‐BB‐treated glioma cells.…”

Selective Aptamer‐Based Control of Intraneuronal Signaling

“…In the central nervous system (CNS), Erk1/2 are essential for different forms of synaptic long‐term plasticity, which is referred to as the molecular mechanism proposed to underlie learning and memory. Aberrant Erk1/2 activity is also thought to contribute importantly to CNS disorders, such as epilepsy, Alzheimer's disease, stroke, and cancer . In all these disorders, the availability of selective and potent Erk1/2 inhibitors will be indispensable for the functional investigation of the individual role of Erk1/2 in neuronal signaling in both, the normal and diseased CNS.…”