Actin isoforms play an important role in the biology of normal and tumor cells. Down-regulation of β-actin/γ-actin overexpression promotes activation of the tumor cells migration and dissemination, while suppression of γ-actin leads to deceleration of these processes. Recent data indicate the importance of the nucleus as an active cell compartment responding to cell deformation and contributes to the cell's decision to change the type of migration. The plasticity of cell migration is one of the basic characteristics of a tumor cell. The work is devoted to the search and study of the previously unknown functions of β- and γ-cytoplasmic actins associated with the cell nucleus.
We used lentiviral genetically engineered constructs to change target actin isoform’s genes expression in human cell lines: lung carcinoma A549 (ATCC® CCL-185™) and breast cancer MDA-MB-231 (ATCC® HTB-26™). Immunofluorescence analysis (IF and N-SIM), flow cytometry, RT-PCR, western-blotting and different in vitro assays were performed.
β-actin overexpression or γ-actin suppression decreased cancer cells invasiveness and proliferation potential. IF search carried out for nuclear targets affected by changes in expression of actin isoforms. Immunocytochemical and morphological differences in nuclei and nuclear structures were identified: changes in the morphology of the nucleus and chromatin, accumulation of lamin B in the nuclear envelope. The morphology/distribution of nuclear bodies and the level of expression and accumulation of nucleolar proteins were investigated. Possible functions of β-actin were revealed: the nuclear size control, ploidy and packing of chromatin; maintaining the stability of the nuclear envelope. On the contrary, the possible functions of γ-actin consist in chromatin decompaction and decreasing the stability of the nuclear envelope.
Changes in the expression of β- and γ-actins affects the nuclear structure: down-regulation of β-actin entails nuclear changes that are characteristic of cancer cells, which is important for carcinogenesis progression; at γ-actin down-regulation, nuclear transformations occur characteristic of normal epithelial cells.
Legal entity responsible for the study
Russian Science Foundation (RSCF), grant No. 20-15-00321.
All authors have declared no conflicts of interest.