The Actin-Bundling Protein Palladin Is an Akt1-Specific Substrate that Regulates Breast Cancer Cell Migration

Department of Pathology, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA 02215, USA.
Molecular cell (Impact Factor: 14.02). 05/2010; 38(3):333-44. DOI: 10.1016/j.molcel.2010.02.031
Source: PubMed


The phosphatidylinositol 3-kinase (PI3K) signaling pathway is frequently deregulated in cancer. Downstream of PI3K, Akt1 and Akt2 have opposing roles in breast cancer invasive migration, leading to metastatic dissemination. Here, we identify palladin, an actin-associated protein, as an Akt1-specific substrate that modulates breast cancer cell invasive migration. Akt1, but not Akt2, phosphorylates palladin at Ser507 in a domain that is critical for F-actin bundling. Downregulation of palladin enhances migration and invasion of breast cancer cells and induces abnormal branching morphogenesis in 3D cultures. Palladin phosphorylation at Ser507 is required for Akt1-mediated inhibition of breast cancer cell migration and also for F-actin bundling, leading to the maintenance of an organized actin cytoskeleton. These findings identify palladin as an Akt1-specific substrate that regulates cell motility and provide a molecular mechanism that accounts for the functional distinction between Akt isoforms in breast cancer cell signaling to cell migration.

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    • "In this study, we found that the Akt2 isoform was activated to a greater degree by the Lifeguard β-isoform than by Lifeguard (Fig. 3B). Several downstream Akt targets have been shown to contribute to the differential functions of these two isoforms in motility, including palladin, nuclear factor of activated T cells, tuberous sclerosis complex 2 and β1 integrins (27–30). "
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    ABSTRACT: In the last century there has been great progress in the treatment of breast cancer by improving drug and radiation therapy as well as surgical techniques. Despite this development, breast cancer remains a major cause of death among women in Europe and the US. The cause of breast cancer at the cellular level is still not fully understood. In the present study, we investigated the expression of the Lifeguard β-isoform in breast cancer tissues. In contrast to Lifeguard, the β‑isoform has one transmembrane domain less, which is the last of seven (99 bp), and due to this we suspect that the Lifeguard β-isoform exhibits a different function. We determined the expression and function of the β-isoform of Lifeguard in breast cancer cell lines (MCF-7 and MDA-MB-231), a human breast epithelial cell line (MCF10A) and in breast tumour tissue sections. Western blotting, PCR arrays and immunofluorescence were used to investigate the expression of Lifeguard and its β-isoform. Moreover, we investigated the ability of Lifeguard β-isoform expression to inhibit apoptosis induced by Fas. Our results indicated that Lifeguard β-isoform is strongly expressed in breast tumour tissues. More notably, we demonstrated that Fas sensitivity was reduced in the MCF10A breast cells expressing the Lifeguard β-isoform. Taken together, our findings indicate the role of the Lifeguard β-isoform as an anti‑apoptotic protein and provide further evidence of the potential of the Lifeguard β-isoform as a target for the development of novel therapeutic strategies.
    Oncology Reports 07/2014; 32(4). DOI:10.3892/or.2014.3363 · 2.30 Impact Factor
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    • "Mitogen-activated protein kinases (MAPKs) are a family of serine/threonine protein kinases involved in the early apoptosis that regulate important cellular processes such as cell survival and adaptation by phosphorylating numerous cytoplasmic and nuclear targets [5-8]. There are at least four distinct subgroups of MAPKs, of which the P38 mitogen-activated protein kinases (p38 MAPKs), c-Jun N-terminal kinases (JNKs), extracellular signal-regulated kinases (ERKs) and protein kinase B (PKB or AKTs) have been extensively described. "
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    ABSTRACT: Background Dillenia suffruticosa root dichloromethane extract (DCM-DS) has been reported to exhibit strong cytotoxicity towards breast cancer cells. The present study was designed to investigate the cell cycle profile, mode of cell death and signalling pathways of DCM-DS-treated human caspase-3 deficient MCF-7 breast cancer cells. Methods Dillenia suffruticosa root was extracted by sequential solvent extraction. The anti-proliferative activity of DCM-DS was determined by using MTT assay. The mode of cell death was evaluated by using inverted light microscope and Annexin-V/PI-flow cytometry analysis. Cell cycle analysis and measurement of intracellular reactive oxygen species (ROS) were performed by using flow cytometry. MCF-7 cells were co-treated with antioxidants α-tocopherol and ascorbic acid to evaluate whether the cell death was mainly due to oxidative stress. GeXP-based multiplex system was employed to investigate the expression of apoptotic, growth and survival genes in MCF-7 cells. Western blot analysis was performed to confirm the expression of the genes. Results DCM-DS was cytotoxic to the MCF-7 cells in a time-and dose-dependent manner. The IC50 values of DCM-DS at 24, 48 and 72 hours were 20.3 ± 2.8, 17.8 ± 1.5 and 15.5 ± 0.5 μg/mL, respectively. Cell cycle analysis revealed that DCM-DS induced G0/G1 and G2/M phase cell cycle arrest in MCF-7 cells at low concentration (12.5 and 25 μg/mL) and high concentration (50 μg/mL), respectively. Although Annexin-V/PI-flow cytometry analysis has confirmed that DCM-DS induced apoptosis in MCF-7 cells, the distinct characteristics of apoptosis such as membrane blebbing, chromatin condensation, nuclear fragmentation and formation of apoptotic bodies were not observed under microscope. DCM-DS induced formation of ROS in MCF-7 cells. Nevertheless, co-treatment with antioxidants did not attenuate the cell death at low concentration of DCM-DS. The pro-apoptotic gene JNK was up-regulated whereby anti-apoptotic genes AKT1 and ERK1/2 were down-regulated in a dose-dependent manner. Western blot analysis has confirmed that DCM-DS significantly up-regulated the expression of pro-apoptotic JNK1, pJNK and down-regulated anti-apoptotic AKT1, ERK1 in MCF-7 cells. Conclusion DCM-DS induced cell cycle arrest and apoptosis in MCF-7 cells via multiple signalling pathways. It shows the potential of DCM-DS to be developed to target the cancer cells with mutant caspase-3.
    BMC Complementary and Alternative Medicine 06/2014; 14(1):197. DOI:10.1186/1472-6882-14-197 · 2.02 Impact Factor
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    • "Moreover , our results demonstrated that PldA/B can interact with Akt1 and Akt2, but not Akt3. Akt1/2 has been proven to play a role in the regulation of palladin activity, which modulates actin cytoskeletal organization (Chin and Toker, 2010a, 2010b). As protrusion formation following actin rearrangement was considered to benefit bacterial entry of epithelial cells (Engel and Eran, 2011), we therefore proposed a model in which PLD-induced Akt activation results in actin rearrangement and membrane protrusion on the apical surface which facilitates P. aeruginosa internalization (Figure 7). "
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    ABSTRACT: Widely found in animal and plant-associated proteobacteria, type VI secretion systems (T6SSs) are potentially capable of facilitating diverse interactions with eukaryotes and/or other bacteria. Pseudomonas aeruginosa encodes three distinct T6SS haemolysin coregulated protein (Hcp) secretion islands (H1, H2, and H3-T6SS), each involved in different aspects of the bacterium's interaction with other organisms. Here we describe the characterization of a P. aeruginosa H3-T6SS-dependent phospholipase D effector, PldB, and its three tightly linked cognate immunity proteins. PldB targets the periplasm of prokaryotic cells and exerts an antibacterial activity. Surprisingly, PldB also facilitates intracellular invasion of host eukaryotic cells by activation of the PI3K/Akt pathway, revealing it to be a trans-kingdom effector. Our findings imply a potentially widespread T6SS-mediated mechanism, which deploys a single phospholipase effector to influence both prokaryotic cells and eukaryotic hosts.
    Cell host & microbe 05/2014; 15(5):600-10. DOI:10.1016/j.chom.2014.04.010 · 12.33 Impact Factor
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