Description
Dbl3 is an apical guanine nucleotide exchange factor that promotes polarised Cdc42 activation to stimulate the apical effectors MRCKβ and the Par3/6/aPKC polarity complex, and, thereby, organisation of the apical actomyosin cytoskeleton. Its overexpression also rescues apical phagocytosis in diseased retinal pigment epithelial (RPE) cells. Polarisation of epithelia is accompanied by transcriptional changes and the acquisition of cell-type-specific functions. Here, we asked if and how apical Dbl3 signalling regulates such transcriptional changes. Gain- and loss-of-function approaches using the kidney epithelial cell line MDCK and RPE cells (ARPE-19 and RPE cells differentiated from iPSC) were combined with RNA sequencing, assays for specific transcriptional pathways and morphological/cytoskeletal responses. RNA sequencing of iPSC-derived RPE cells treated with either Dbl3- or MRCKβ-targeting siRNAs or, alternatively, an MRCK inhibitor indicated deregulation of genes associated with the differentiated phenotype and genes regulating polarisation, adhesion, cell proliferation, morphological changes, and genes indicative of deregulation of inflammatory signalling and YAP/TAZ activity. Gene reporter assays, immunofluorescence, and immunoblotting confirmed the regulation of YAP/TAZ, NFkB, and STAT3 signalling by the Dbl3/MRCKβ pathway. Our data thus suggest that Dbl3–MRCKβ signalling links epithelial apical polarisation to regulation of transcription, suggesting that approaches to stimulate Dbl3 function in malfunctioning epithelia may be beneficial in disease beyond the rescue of specific apical processes by regulating genes imported for epithelial integrity and function.
Lay Abstract
The back of the eye contains a layer of cells called the retinal pigment epithelium (RPE). The RPE plays a crucial role in maintaining healthy vision. In diseases such as age-related macular degeneration (AMD), these cells gradually lose their structure and function, leading to vision loss.
Our research focuses on a protein called Dbl3, which helps cells maintain their shape, organisation, and internal structure. These physical properties are important because they influence how cells behave and function, and which genes they turn on or off.
We found that Dbl3 helps keep RPE cells organised and regulates specific molecular mechanisms that control gene expression. When Dbl3 was disrupted, cells lost their structure and showed signs of increased stress and inflammation, which are linked to disease.
Understanding how cell structure controls these processes could open up new ways to protect the eye and slow down diseases like AMD.
| Lay Title | How cell shape and structure help protect the eye from disease |
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| Role | PhD Student |