Silencing GFAP isoforms in astrocytoma cells disturbs laminin‐dependent motility and cell adhesion

Abstract

Glial fibrillary acidic protein (GFAP) is an intermediate filament protein expressed in astrocytes and neural stem cells. The GFAP gene is alternatively spliced, and expression of GFAP is highly regulated during development, on brain damage, and in neurodegenerative diseases. GFAPα is the canonical splice variant and is expressed in all GFAP-positive cells. In the human brain, the alternatively spliced transcript GFAPδ marks specialized astrocyte populations, such as subpial astrocytes and the neurogenic astrocytes in the human subventricular zone. We here show that shifting the GFAP isoform ratio in favor of GFAPδ in astrocytoma cells, by selectively silencing the canonical isoform GFAPα with short hairpin RNAs, induced a change in integrins, a decrease in plectin, and an increase in expression of the extracellular matrix component laminin. Together, this did not affect cell proliferation but resulted in a significantly decreased motility of astrocytoma cells. In contrast, a down-regulation of all GFAP isoforms led to less cell spreading, increased integrin expression, and a >100-fold difference in the adhesion of astrocytoma cells to laminin. In summary, isoform-specific silencing of GFAP revealed distinct roles of a specialized GFAP network in regulating the interaction of astrocytoma cells with the extracellular matrix through laminin.-Moeton, M., Kanski, R., Stassen, O. M. J. A., Sluijs, J. A., Geerts, D., van Tijn, P., Wiche, G., van Strien, M. E., Hol, E. M. Silencing GFAP isoforms in astrocytoma cells disturbs laminin dependent motility and cell adhesion.

Networking and anchoring through plectin: a key to IF functionality and mechanotransduction

“…A symbiotic relation between invadopodia and exosome secretion resulting in increased invasion of cancer cells has recently been identified [40]. Plectin has also been implicated in the migratory potential of astrocytoma cells [41].…”

Roles and Potential Clinical Applications of Intermediate Filament Proteins in Brain Tumors

“…59,60 GFAPδ is also found in astrocytomas, where its expression level correlates with high malignancy. 51,52 A recent investigation by Moeton et al 61 evaluated the effect of GFAP isoforms on astrocytoma cell motility. shRNA-mediated GFAPα downregulation in glioblastoma cells caused an induction of GFAPδ isoform, which impaired astrocytoma cell motility.…”

“…These cells also had increased laminin expression, which contributed to their enhanced adhesive properties. 61 Thus, taking into account GFAP isoforms provides another dimension to the potential function and role of GFAP in the malignancy of high-grade gliomas.…”

Histone acetylation in astrocytes suppresses GFAP and stimulates a re-organization of the intermediate filament network

“…After 72 hours, cells were collected in Trizol for mRNA analysis or fixed with 4% formalin for 10 minutes at room temperature for immunofluorescent staining. Lentiviral production and in vitro transduction were performed as described previously (Moeton et al, 2014).…”