Astrocytes, the most abundant glial cells, are morphologically plastic cells of the central nervous system. Growing evidence indicates that noradrenaline (NA) plays an important role in regulating changes in their morphology, such as the formation of cellular processes, which are directly associated with cytoskeletal reorganization and, consequently, with the mechanical properties of the cells. GPR27 is an orphan G protein-coupled receptor whose role in astrocytes remains unclear. In this master's thesis, we investigated the effects of GPR27 and NA on cytoskeletal organization and the mechanical properties of mouse astrocytes. Using high-resolution STED microscopy and Airyscan microscopy, we analysed organisation and spatial occupancy of actin filaments, microtubules, and intermediate filaments of fixed cells, while atomic force microscopy (AFM) was used to determine the Young’s modulus of living cells, reflecting their stiffness or elasticity. NA induced reorganization of all three cytoskeletal networks; however, the dependence of these responses on GPR27 differed among the networks. The most pronounced effect of GPR27 was observed in the actin cytoskeleton. In wild-type astrocytes, NA increased the parallelness and density of the actin network, as well as its spatial occupancy at the whole-cell level and in the peripheral region, whereas no comparable response was observed in GPR27 KO astrocytes, and the change in parallelness was in the opposite direction. The density of both the microtubule and intermediate filament networks increased following NA treatment independently of genotype. In the microtubule network, treatment with NA also increased spatial occupancy across the whole cell and in both the perinuclear and peripheral regions, whereas in the intermediate filament network, a genotype-dependent change was observed primarily in the perinuclear region. For some parameters, differences between the genotypes were already present before stimulation. These results suggest that GPR27 primarily modulates actin plasticity in astrocytes during adrenergic stimulation. Despite the cytoskeletal changes, we found no evidence that GPR27 or NA affected the mechanical properties of the cells. Young’s modulus did not differ with either genotype or treatment, while it was significantly higher at the cell periphery than above the nucleus in all cells.
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