Beta‑catenin Forms Protein Aggregation at High Concentrations in HEK293TCells

Background: The canonical Wnt signal transduction (or the Wnt/β‑catenin pathway) plays a crucial role in the development of animals and in carcinogenesis. Beta‑catenin is the central component of this signaling pathway. The activation of Wnt/β‑catenin signaling results in the cytoplasmic and nuclear accumulation of β‑catenin. In the nucleus, β‑catenin interacts with the TCF/LEF transcription factors and, therefore, participates in the upregulation or downregulation of some important genes involved in diverse cellular activities. In addition, β‑catenin is a critical component of the cadherin‑mediated cell adherens junction. We had previously noticed that very high cellular concentrations of β‑catenin had a negative effect on the transcriptional activity of this protein and, therefore, the aim of this study was to find a mechanism for this negative interaction. Methods: Cell fractionation, western blotting, and immunofluorescence microscopy experiments were performed to measure β‑catenin protein levels and β‑catenin cellular localization in HEK293Tcells transfected with various amounts of a β‑catenin‑encoding plasmid. Also, total RNA was extracted from the cells and used for reverse transcriptase‑PCR experiments to measure the expression of the β‑catenin target genes. SPSS, version 16, was used to analyze the results statistically. Results: We demonstrated that overexpression of β‑catenin led to the formation of rod‑shaped protein aggregates. The aggregate structures were mainly formed in the cell nucleus and were heavy enough to be isolated by centrifugation. Beta‑catenin aggregate formation was accompanied by a decrease in the expression of theβ‑catenin target genes used in this study. Conclusion: Since deregulation of β‑catenin function occurs in several human diseases, including cancer and neurological disorders, the results of this paper further support the possible biological and clinical significance of β‑catenin aggregate formation.