Role of Palladin Phosphorylation by Extracellular Signal-Regulated Kinase in Cell Migration

Phosphorylation of actin-binding proteins plays a pivotal role in the remodeling of the actin cytoskeleton to regulate cell migration. Palladin is an actin-binding protein that is phosphorylated by growth factor stimulation; however, the identity of the involved protein kinases remains elusive. In this study, we report that palladin is a novel substrate of extracellular signal-regulated kinase (ERK). Suppression of ERK activation by a chemical inhibitor reduced palladin phosphorylation, and expression of active MEK alone was sufficient for phosphorylation. In addition, an in vitro kinase assay demonstrated direct palladin phosphorylation by ERK. We found that Ser77 and Ser197 are essential residues for phosphorylation. Although the phosphorylation of these residues was not required for actin cytoskeletal organization, we found that expression of non-phosphorylated palladin enhanced cell migration. Finally, we show that phosphorylation inhibits the palladin association with Abl tyrosine kinase. Taken together, our results indicate that palladin phosphorylation by ERK has an anti-migratory function, possibly by modulating interactions with molecules that regulate cell migration

FAM98A associates with DDX1-C14orf166-FAM98B in a novel complex involved in colorectal cancer progression

Protein Arginine Methyl Transferase 1 (PRMT1) is deemed to be a potential oncogenic protein considering its overexpression in several malignancies including colorectal cancer. However, the molecular pathogenesis regarding PRMT1 overexpression and overall poor patient survival involved in this devastating and life threatening cancer remains obscured. In our previous study, we have identified FAM98A as a novel substrate of PRMT1 and also identified its role in ovarian cancer progression. Here, we showed that the two structural homologs FAM98A and FAM98B included in a novel complex with DDX1 and C14orf166 are required for PRMT1 expression. Analysis of the data from The Cancer Genome Atlas (TCGA) database and clinical colorectal cancer specimens also demonstrated a strong positive correlation and co-occurrence of PRMT1, FAM98A and FAM98B. These findings provide a mechanistic insight into how knockdown of FAM98A or FAM98B can suppress the malignant characteristics of cancer cells. Besides, we showed that FAM98A and FAM98B are working in the same axis as knockdown of both proteins together does not cause additional reduction in the cellular proliferation and colony formation of colorectal cancer cells

Special AT-rich sequence-binding protein 2 suppresses invadopodia formation in HCT116 cells via palladin inhibition

Invadopodia are specialized actin-based microdomains of the plasma membrane that combine adhesive properties with matrix degrading activities. Proper functioning of the bone, immune, and vascular systems depend on these organelles, and their relevance in cancer cells is linked to tumor metastasis. The elucidation of the mechanisms driving invadopodia formation is a prerequisite to understanding their role and ultimately to controlling their functions. Special AT-rich sequence-binding protein 2 (SATB2) was reported to suppress tumor cell migration and metastasis. However, the mechanism of action of SATB2 is unknown. Here, we show that SATB2 inhibits invadopodia formation in HCT116 cells and that the molecular scaffold palladin is inhibited by exogenous expression of SATB2. To confirm this association, we elucidated the function of palladin in HCT116 using a knock down strategy. Palladin knock down reduced cell migration and invasion and inhibited invadopodia formation. This phenotype was confirmed by a rescue experiment. We then demonstrated that palladin expression in SATB2-expressing cells restored invasion and invadopodia formation. Our results showed that SATB2 action is mediated by palladin inhibition and the SATB2/palladin pathway is associated with invadopodia formation in colorectal cancer cells

FAM98A is a novel substrate of PRMT1 required for tumor cell migration, invasion, and colony formation

Protein arginine methylation, which is mediated by a family of protein arginine methyltransferases (PRMTs), is associated with numerous fundamental cellular processes. Accumulating studies have revealed that the expression of multiple PRMTs promotes cancer progression. In this study, we examined the role of PRMT1 in ovarian cancer cells. PRMT1 is expressed in multiple ovarian cancer cells, and the depletion of its expression suppressed colony formation, in vivo proliferation, migration, and invasion. To gain insight into PRMT1-mediated cancer progression, we searched for novel substrates of PRMT1. We found that FAM98A, whose physiological function is unknown, was arginine-methylated by PRMT1. FAM98A is expressed in numerous ovarian cancer cell lines and is important for the malignant characteristics of ovarian cancer cells. Our results indicate the possible role of the PRMT1-FAM98A pathway in cancer progression

UBE2S is associated with malignant characteristics of breast cancer cells

Ubiquitination is essential for various biological processes, such as signal transduction, intracellular trafficking, and protein degradation. Accumulating evidence has demonstrated that ubiquitination plays a crucial role in cancer development. In this report, we examine the expression and function of ubiquitin-conjugating enzyme E2S (UBE2S) in breast cancer. Immunohistochemical analysis revealed that UBE2S is highly expressed in breast cancer. The depletion of UBE2S by siRNA induced disruption of the actin cytoskeleton and focal adhesions. Interestingly, phosphorylation of FAK at Tyr397, which is important for the transduction of integrin-mediated signaling, was significantly reduced by UBE2S knockdown. We also show that UBE2S knockdown suppressed the malignant characteristics of breast cancer cells, such as migration, invasion, and anchorage-independent growth. Our results indicate that UBE2S could be a potential target for breast cancer treatment

EML4 promotes the loading of NUDC to the spindle for mitotic progression

<div><p>Echinoderm microtubule-associated protein (EMAP)-like (EML) family proteins are microtubule-associated proteins that have a conserved hydrophobic EMAP-like protein (HELP) domain and multiple WD40 domains. In this study, we examined the role of EML4, which is a member of the EML family, in cell division. Time-lapse microscopy analysis demonstrated that EML4 depletion induced chromosome misalignment during metaphase and delayed anaphase initiation. Further analysis by immunofluorescence showed that EML4 was required for the organization of the mitotic spindle and for the proper attachment of kinetochores to microtubules. We searched for EML4-associating proteins by mass spectrometry analysis and found that the nuclear distribution gene C (NUDC) protein, which is a critical factor for the progression of mitosis, was associated with EML4. This interaction was mediated by the WD40 repeat of EML4 and by the C-terminus of NUDC. In the absence of EML4, NUDC was no longer able to localize to the mitotic spindle, whereas NUDC was dispensable for EML4 localization. Our results show that EML4 is critical for the loading of NUDC onto the mitotic spindle for mitotic progression.</p></div

Flow cytometry-based quantification of genome editing efficiency in human cell lines using the L1CAM gene.

CRISPR/Cas9 is a powerful genome editing system that has remarkably facilitated gene knockout and targeted knock-in. To accelerate the practical use of CRISPR/Cas9, however, it remains crucial to improve the efficiency, precision, and specificity of genome editing, particularly targeted knock-in, achieved with this system. To improve genome editing efficiency, researchers should first have a molecular assay that allows sensitive monitoring of genome editing events with simple procedures. In the current study, we demonstrate that genome editing events occurring in L1CAM, an X-chromosome gene encoding a cell surface protein, can be readily monitored using flow cytometry (FCM) in multiple human cell lines including neuroblastoma cell lines. The abrogation of L1CAM was efficiently achieved using Cas9 nucleases which disrupt exons encoding the L1CAM extracellular domain, and was easily detected by FCM using anti-L1CAM antibodies. Notably, L1CAM-abrogated cells could be quantified by FCM in four days after transfection with a Cas9 nuclease, which is much faster than an established assay based on the PIGA gene. In addition, the L1CAM-based assay allowed us to measure the efficiency of targeted knock-in (correction of L1CAM mutations) accomplished through different strategies, including a Cas9 nuclease-mediated method, tandem paired nicking, and prime editing. Our L1CAM-based assay using FCM enables rapid and sensitive quantification of genome editing efficiencies and will thereby help researchers improve genome editing technologies

SHCBP1 is required for midbody organization and cytokinesis completion

<div><p>The centralspindlin complex, which is composed of MKLP1 and MgcRacGAP, is one of the crucial factors involved in cytokinesis initiation. Centralspindlin is localized at the middle of the central spindle during anaphase and then concentrates at the midbody to control abscission. A number of proteins that associate with centralspindlin have been identified. These associating factors regulate furrowing and abscission in coordination with centralspindlin. A recent study identified a novel centralspindlin partner, called Nessun Dorma, which is essential for germ cell cytokinesis in <i>Drosophila melanogaster</i>. SHCBP1 is a human ortholog of Nessun Dorma that associates with human centralspindlin. In this report, we analyzed the interaction of SHCBP1 with centralspindlin in detail and determined the regions that are required for the interaction. In addition, we demonstrate that the central region is necessary for the SHCBP1 dimerization. Both MgcRacGAP and MKLP1 are degraded once cells exit mitosis. Similarly, endogenous and exogenous SHCBP1 were degraded with mitosis progression. Interestingly, SHCBP1 expression was significantly reduced in the absence of centralspindlin, whereas centralspindlin expression was not affected by SHCBP1 knockdown. Finally, we demonstrate that SHCBP1 depletion promotes midbody structure disruption and inhibits abscission, a final stage of cytokinesis. Our study gives novel insight into the role of SHCBP in cytokinesis completion.</p></div

Near-diploid male cell lines highly expressing <i>L1CAM</i>, besides SK-N-BE(2), may serve as platforms for the <i>L1CAM</i> assay.

(A) Representative dot plots obtained in this analysis. The CHP-134, LA-N-5, and TGW neuroblastoma cell lines and the HCT116 colon cancer cell line were transfected with ex26-1 or ex26-2 nuclease, a vector control, or none. The cells were then stained as indicated at the top of the panels and analyzed applying FCM settings noted along the X- and Y-axes of dot plots. Percentages of Alexa Fluor 488-negative cells are denoted in the plots. (B) Graphical summary of the experimental results, with representatives shown in (A). The results of FCM analyses conducted without staining cells are omitted from the graphs. Data represent the mean and SEM values from three independent experiments.</p