The effect of the RACK1 signalling protein on the regulation of cell adhesion and cell contact guidance on nanometric grooves

Abstract: A wide variety of different cell types have been shown to respond to nanofabricated growth surfaces via the process of contact guidance, however little is known about the intracellular mechanisms that control these events. In the present study we have identified the multi-functional signalling adaptor protein, RACK1, as a novel negative regulator of contact guidance on custom-engineered nanometric grooves. We found that over-expression of RACK1 in human breast cancer cells leads to a pro-adherent morphology characterised by the formation of stress fibres and focal adhesions. Enforced expression of RACK1 also limits the response of cells to contact guidance on nanometric grooves. In contrast, ablation of RACK1 protein with specific anti-sense oligonucleotides led to a dramatic enhancement of bi-directional extension of cells on nanometrically deep grooved surfaces, with a corresponding loss of focal adhesions and stress fibres. RACK1 therefore exerts a tonic inhibitory effect on cell contact guidance, while positively promoting an adhesive phenotype. This is the first example of an intracellular signalling molecule involved in the regulation of cell contact guidance on nanometric growth surfaces

Nucleus alignment and cell signaling in fibroblasts: response to a micro-grooved topography

Cellular response to scaffold materials is of great importance in cellular and tissue engineering, and it is perhaps the initial cell contact with the scaffold that determines development of new tissue. Material surface morphology has strong effects on cell cytoskeleton and morphology, and it is thought that cells may react to the topography of collagen and surrounding cells during tissue embryology. A poorly understood area is, however, gene-level responses to topography. Thus, this paper used microarray to probe for consistent gene changes in response to lithographically produced topography (12.5 × 2-μm grooves) with time. The results showed many initial gene changes and also down-regulation of gene response with time. Cell and nucleus morphology were also considered, with nuclear deformation linked to cell signaling

Corrigendum to "Metformin suppresses adipogenesis through both AMP-activated protein kinase (AMPK)-dependent and AMPK-independent mechanisms" [Mol. Cell. Endocrinol. 440 15 January 2017 57-68]

No abstract available

RACK1 Regulates Integrin-mediated Adhesion, Protrusion, and Chemotactic Cell Migration via Its Src-binding Site

Mammalian cDNA expression cloning was used to identify novel regulators of integrin-mediated cell-substratum adhesions. Using a focal adhesion morphology screen, we identified a cDNA with homology to a receptor for activated protein kinase C (RACK1) that induced a loss of central focal adhesions and stress fibers in CHO-K1 cells. The identified cDNA was a C-terminal truncated form of RACK1 that had one of the putative protein kinase C binding sites but lacked the region proposed to bind the β integrin cytoplasmic domain and the tyrosine kinase Src. To investigate the role of RACK1 during cell spreading and migration, we tagged RACK1, a C-terminal truncated RACK1 and a point mutant that does not bind Src (RACK Y246F) with green fluorescent protein and expressed them in CHO-K1 cells. We found that RACK1 regulates the organization of focal adhesions and that it localizes to a subset of nascent focal complexes in areas of protrusion that contain paxillin but not vinculin. We also found that RACK1 regulates cell protrusion and chemotactic migration through its Src binding site. Together, these findings suggest that RACK1 regulates adhesion, protrusion, and chemotactic migration through its interaction with Src