Differential Subcellular Distribution and Translocation of Seven 14-3-3 Isoforms in Response to EGF and During the Cell Cycle

• Published in: International journal of molecular sciences Vol. 21; no. 1; p. 318
• Main Authors: Abdrabou, Abdalla, Brandwein, Daniel, Wang, Zhixiang
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 02.01.2020; MDPI
• Subjects: 14-3-3 protein; 14-3-3 proteins; Actin; actin fibers; and microtubules; Antibodies; Cancer; Cell cycle; Cell growth; centrosome; Cyclin-dependent kinases; Cytoplasm; Fractionation; Fractions; Immunoblotting; Immunofluorescence; Isoforms; Kinases; Localization; Mammalian cells; Microtubules; Mitochondria; Mitosis; Molecular weight; Nuclei (cytology); nucleus; Organelles; Peptides; Phosphorylation; Prostate; Proteins; subcellular localization; 14-3-3 proteins; and microtubules; subcellular localization; actin fibers; mitochondria; isoforms; nucleus; centrosome
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms21010318

Multiple isoforms of 14-3-3 proteins exist in different organisms. In mammalian cells, 14-3-3 protein has seven isoforms (α/β, ε, η, γ, σ, θ/τ, and δ/ζ), with α and δ representing the phosphorylated versions of β and ζ, respectively. While the existence of multiple isoforms may represent one more level of regulation in 14-3-3 signaling, our knowledge regarding the isoform-specific functions of 14-3-3 proteins is very limited. Determination of the subcellular localization of the different 14-3-3 isoforms could give us important clues of their specific functions. In this study, by using indirect immunofluorescence, subcellular fractionation, and immunoblotting, we studied the subcellular localization of the total 14-3-3 protein and each of the seven 14-3-3 isoforms; their redistribution throughout the cell cycle; and their translocation in response to EGF in Cos-7 cells. We showed that 14-3-3 proteins are broadly distributed throughout the cell and associated with many subcellular structures/organelles, including the plasma membrane (PM), mitochondria, ER, nucleus, microtubules, and actin fibers. This broad distribution underlines the multiple functions identified for 14-3-3 proteins. The different isoforms of 14-3-3 proteins have distinctive subcellular localizations, which suggest their distinctive cellular functions. Most notably, 14-3-3ƞ is almost exclusively localized to the mitochondria, 14-3-3γ is only localized to the nucleus, and 14-3-3σ strongly and specifically associated with the centrosome during mitosis. We also examined the subcellular localization of the seven 14-3-3 isoforms in other cells, including HEK-293, MDA-MB-231, and MCF-7 cells, which largely confirmed our findings with Cos-7 cells.