Abstract
Recent studies have revealed that newly emerging RasV12-transformed cells are often apically extruded from the epithelial layer. During this cancer preventive process, cytoskeletal proteins plectin and Epithelial Protein Lost In Neoplasm (EPLIN) are accumulated in RasV12 cells that are surrounded by normal cells, which positively regulate the apical elimination of transformed cells. However, the downstream regulators of the plectin-EPLIN complex remain to be identified. In this study, we have found that paxillin binds to EPLIN specifically in the mix culture of normal and RasV12-transformed cells. In addition, paxillin is accumulated in RasV12 cells surrounded by normal cells. Paxillin, plectin and EPLIN mutually influence their non-cell-autonomous accumulation, and paxillin plays a crucial role in apical extrusion of RasV12 cells. We also demonstrate that in RasV12 cells surrounded by normal cells, acetylated tubulin is accumulated. Furthermore, acetylation of tubulin is promoted by paxillin that suppresses the activity of histone deacetylase (HDAC) 6. Collectively, these results indicate that in concert with plectin and EPLIN, paxillin positively regulates apical extrusion of RasV12-transformed cells by promoting microtubule acetylation. This study shed light on the unexplored events occurring at the initial stage of carcinogenesis and would potentially lead to a novel type of cancer preventive medicine.
Highlights
At the initial stage of carcinogenesis, an oncogenic mutation occurs in single cells within the epithelium
We have reported that cytoskeletal proteins plectin and Epithelial Protein Lost In Neoplasm (EPLIN) are accumulated in RasV12 cells when they are surrounded by normal cells[14,15]
By immunofluorescence, we demonstrated that paxillin was accumulated and partially co-localized with EPLIN in RasV12 cells that were surrounded by normal cells, but not in RasV12 cells cultured alone (Figs 1b,c, 2a and 3a)
Summary
At the initial stage of carcinogenesis, an oncogenic mutation occurs in single cells within the epithelium. In the cell competition between normal and RasV12-transformed epithelial cells, the presence of normal cells profoundly influences various cellular processes and signalling pathways in the neighbouring transformed cells, which positively regulate their apical extrusion. This process plays a crucial role in the apical extrusion of RasV12 cells, the molecular mechanism of how plectin and EPLIN regulate the organization of microtubules remains unknown. We have found that paxillin is a vital regulator of apical extrusion of RasV12-transformed cells by linking the plectin-EPLIN complex and acetylation of microtubules
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