Enigma Protein Research Articles

Regulatory and Interacting Partners of PDLIM7 in Thyroid Cancer.

Enigma protein, encoded by the PDLIM7 gene, is overexpressed in thyroid cancer in a stage-dependent manner, suggesting a potential involvement in the initiation and progression of thyroid cancer. The Enigma interacts with several cellular pathways, including PI3K/AKT, MDM2, and BMP-1. The Enigma is regulated by microRNAs. Specifically, we showed that the Enigma protein upregulation corresponds to the downregulation of Let-7 family genes. There is limited research on the interactions and regulation of the Enigma with other proteins/genes in thyroid cancer tissues, indicating a gap in current knowledge. Our aim is to establish the Enigma as a biomarker. We also aim to study the interacting partners of the Enigma signaling pathways and their probable miRNA regulation in thyroid cancer progression. Using Western blotting, densitometric analysis, immunoprecipitation (IP), and reverse IP, we detected the protein expression and protein-protein interactions in the corresponding papillary thyroid carcinomas (PTCs). Utilizing real-time qPCR assay and Pearson's correlation test, we highlighted the correlation between PDLIM7 and Let-7g gene expression in the same tissues. The results showed the differential upregulations of the Enigma protein in different stages of PTCs compared to benign tissues along with AKT, VDR, BMP-1, and MDM2 proteins. Loss of DBP was observed in a subset of PTCs. Strong interactions of the Enigma with PI3K/AKT and MDM2 were noted, along with a weaker BMP-1 interaction. Pearson's correlation coefficient analysis between PDLIM7 and let-7g gene expression was significant (p < 0.05); however, there was a weak inverse correlation (r = -0.27). The study suggests the potential utility of the PDLIM7-qPCR assay as a biomarker for thyroid cancer. The Enigma's interactions with key signaling pathways may provide valuable insights into the development of thyroid cancer. The study contributes to understanding the molecular mechanisms involving the Enigma protein in thyroid cancer and highlights its potential as a biomarker.

Analysis of Enigma Gene-Signaling Pathways in Thyroid Cancer

Fine-needle aspiration (FNA) is one of the most accurate modes of obtaining thyroid nodule biopsies, however, up to 25% of biopsies still yield indeterminate results. There is an increasing number of thyroidectomies due to indeterminate nodules by FNA alone. Therefore, more accurate and time efficient diagnostic approaches for analyzing indeterminate thyroid nodules is required. Recent studies showed that Enigma is associated with different cancer types, including thyroid cancer progression and calcification through its interaction with bone morphogenic protein-1 (BMP-1) and tyrosine kinases linked to mitogen-activated protein kinase (MAPK) signaling pathway. Our published data on Enigma protein analysis with immunohistochemistry showed promising findings to discriminate malignant versus benign nodules. We also showed a thyroid cancer stage-dependent enhancement of Enigma protein expression. In this study, we are investigating Enigma at a gene expression level by quantitative reverse transcription polymerase chain reaction (RT-qPCR), which is more time-efficient, quantitative, and requires less tissue than immunohistochemistry. We extracted mRNA/DNA/proteins from fresh malignant and benign thyroid nodules using a Qiagen AllPrep DNA/RNA/Protein Mini Kit. After verification of the quantity and purity by NanoDrop, isolated mRNA was then run through Enigma-RT-qPCR. MAPK assay was done by western blotting using MAPK-antibody. Our initial results found that Enigma-mRNA expression level was 3-fold higher in malignant compared to benign thyroid tissues. This finding supports our previous protein expression data with a relative quantitative difference in Enigma-mRNA expression level between malignant and benign thyroid nodules. MAPK expression was upregulated in thyroid cancer compared to benign nodules. We conclude that Enigma-RT-qPCR can be used effectively in FNA samples derived from thyroid nodules, which could potentially enhance the diagnostic accuracy of indeterminate nodules and decrease unnecessary thyroidectomies. Furthermore, both Enigma and MAPK were highly expressed in advanced tumor in the same tissues. Future study is needed to establish the functional interaction of Enigma-MAPK activity in thyroid cancer cells.

Evolutionarily diverse LIM domain-containing proteins bind stressed actin filaments through a conserved mechanism

The actin cytoskeleton assembles into diverse load-bearing networks, including stress fibers (SFs), muscle sarcomeres, and the cytokinetic ring to both generate and sense mechanical forces. The LIM (Lin11, Isl- 1, and Mec-3) domain family is functionally diverse, but most members can associate with the actin cytoskeleton with apparent force sensitivity. Zyxin rapidly localizes via its LIM domains to failing SFs in cells, known as strain sites, to initiate SF repair and maintain mechanical homeostasis. The mechanism by which these LIM domains associate with stress fiber strain sites (SFSS) is not known. Additionally, it is unknown how widespread strain sensing is within the LIM protein family. We identify that the LIM domain-containing region of 18 proteins from the Zyxin, Paxillin, Tes, and Enigma proteins accumulate to SFSS. Moreover, the LIM domain region from the fission yeast protein paxillin like 1 (Pxl1) also localizes to SFSS in mammalian cells, suggesting that the strain sensing mechanism is ancient and highly conserved. We then used sequence and domain analysis to demonstrate that tandem LIM domains contribute additively, for SFSS localization. Employing in vitro reconstitution, we show that the LIM domain-containing region from mammalian zyxin and fission yeast Pxl1 binds to mechanically stressed F-actin networks but does not associate with relaxed actin filaments. We propose that tandem LIM domains recognize an F-actin conformation that is rare in the relaxed state but is enriched in the presence of mechanical stress.

Enigma proteins control YAP1 related mechano-transduction in hepatic stellate cells

Enigma proteins control YAP1 related mechano-transduction in hepatic stellate cells

MON-516 Quantitative Analysis of Differential Enigma/PDLIM7 Gene Expression in Thyroid Cancer vs. Benign Nodules

Thyroid cancer incidence is rising worldwide. Although fine-needle aspiration biopsy (FNAB) is an accurate modality for evaluating thyroid nodules, up to 25% of FNABs still yield indeterminate results. There is a considerable number of diagnostic thyroidectomies for benign disease as a result of indeterminate FNAB. A more accurate and time-efficient diagnostic approach for analyzing indeterminate thyroid nodules may reduce diagnostic thyroidectomy. Recently, the osteogenic protein, Enigma, has been associated with different cancer types, including thyroid cancer progression and calcification through its interaction with bone morphogenic protein-1 (BMP-1), and tyrosine kinases linked to mitogenic signaling pathways [1, 2]. Our published data on Enigma protein analysis with immunohistochemistry showed promising results in discriminating between malignant versus benign thyroid nodules and demonstrated a correlation with thyroid cancer staging [3]. In this study, we are investigating Enigma at a gene expression level by real-time (RT-qPCR), which is a quantitative and more time-efficient method that requires smaller samples (FNA) than immunohistochemistry. We analyzed Enigma mRNA expression levels to determine if Enigma-qPCR could be used as a diagnostic tool to improve the accuracy of FNAB in both malignant and benign thyroid tissues. We extracted mRNA/DNA/proteins from fresh malignant and benign thyroid nodules using a QIAGEN DNA/RNA/Protein Kit. We ran isolated pure mRNA through Enigma-qPCR. The results showed that the Enigma-mRNA expression was 3-fold higher in malignant as compared to benign thyroid tissues. This finding supports our previous Enigma immunohistochemistry data and shows a relative quantitative difference in Enigma-mRNA expression level between malignant and benign thyroid nodules. We conclude that Enigma-RT-qPCR can be used to effectively determine malignancies in FNAB samples derived from thyroid nodules. This method could potentially enhance the diagnostic accuracy of indeterminate nodules and decrease diagnostic thyroidectomies and associated morbidity.[1] C.R. Jung, J.H. Lim, Y. Choi, D.G. Kim, K.J. Kang, S.M. Noh, D.S. Im, Enigma negatively regulates p53 through MDM2 and promotes tumor cell survival in mice, The Journal of clinical investigation 120(12) (2010) 4493-506.[2] Y.J. Kim, H.J. Hwang, J.G. Kang, C.S. Kim, S.H. Ihm, M.G. Choi, S.J. Lee, Enigma Plays Roles in Survival of Thyroid Carcinoma Cells through PI3K/AKT Signaling and Survivin, Anticancer research 38(6) (2018) 3515-3525.[3] A.A. Firek, M.C. Perez, A. Gonda, L. Lei, I. Munir, A.A. Simental, F.E. Carr, B.J. Becerra, M. De Leon, S. Khan, Pathologic significance of a novel oncoprotein in thyroid cancer progression, Head & neck 39(12) (2017) 2459-2469.

First person – Ahmed Elbediwy

ABSTRACT First Person is a series of interviews with the first authors of a selection of papers published in Journal of Cell Science, helping early-career researchers promote themselves alongside their papers. Ahmed Elbediwy is the first author on ‘Enigma proteins regulate YAP mechanotransduction’, published in Journal of Cell Science. Ahmed is a postdoctoral fellow in the lab of Barry Thompson at The Francis Crick Institute, London, UK, investigating the cytoskeleton, RhoGTPases and the regulation of YAP/TAZ oncoproteins.

Enigma proteins regulate YAP mechanotransduction.

ABSTRACTHuman cells can sense mechanical stress acting upon integrin adhesions and respond by sending the YAP (also known as YAP1) and TAZ (also known as WWTR1) transcriptional co-activators to the nucleus to drive TEAD-dependent transcription of target genes. How integrin signaling activates YAP remains unclear. Here, we show that integrin-mediated mechanotransduction requires the Enigma and Enigma-like proteins (PDLIM7 and PDLIM5, respectively; denoted for the family of PDZ and LIM domain-containing proteins). YAP binds to PDLIM5 and PDLIM7 (hereafter PDLIM5/7) via its C-terminal PDZ-binding motif (PBM), which is essential for full nuclear localization and activity of YAP. Accordingly, silencing of PDLIM5/7 expression reduces YAP nuclear localization, tyrosine phosphorylation and transcriptional activity. The PDLIM5/7 proteins are recruited from the cytoplasm to integrin adhesions and F-actin stress fibers in response to force by binding directly to the key stress fiber component α-actinin. Thus, forces acting on integrins recruit Enigma family proteins to trigger YAP activation during mechanotransduction.This article has an associated First Person interview with the first author of the paper.

Identification of target muscle-proteins using Western blotting and high-resolution mass spectrometry as early quality indicators of nutrient supply practices in rainbow trout (Oncorhynchus mykiss)

Using Western blotting and mass spectrometry we investigated the changes in trout muscle proteins as affected by pre-slaughter nutrient supply practices, including starvation and feed restriction, in comparison to full feeding. A number of fillet quality attributes were also analyzed. During cold storage, fillet firmness was not influenced by the feeding practices, while the initial pH was higher in the treated trout. The early appearance of an alpha-actin 26 kDa-fragment and the detection of enigma protein were both signs of impaired muscle integrity, observed only in the restricted conditions, where water holding capacity was initially lower. The detection of reticulon involved in authophagy and the early finding of apolipoprotein A-I-1 fragments in these restricted samples was consistent with their early degradation in comparison to full ration controls. Since specific protein changes reflected differences in feed management, the use of selected muscle proteins as sensitive indicators of fillet quality is proposed.

The C. elegans BRCA2-ALP/Enigma Complex Regulates Axon Regeneration via a Rho GTPase-ROCK-MLC Phosphorylation Pathway

The ability of specific neurons to regenerate their axons after injury is governed by cell-intrinsic regeneration pathways. However, the mechanisms regulating axon regeneration are not well understood. Here, we identify the brc-2 gene encoding a homolog of the mammalian BRCA2 tumor suppressor as a regulator of axon regeneration in Caenorhabditis elegans motor neurons. We show that the RHO-1/Rho GTPase-LET-502/ROCK (Rho-associated coiled-coil kinase)-regulatory non-muscle myosin light-chain (MLC-4/MLC) phosphorylation signaling pathway regulates axon regeneration. BRC-2 functions between RHO-1 and LET-502, suggesting that BRC-2 is required for the activation of LET-502 by RHO-1-GTP. We also find that one component that interacts with BRC-2, the ALP (α-actinin-associated LIM protein)/Enigma protein ALP-1, is required for regeneration and acts between LET-502 and MLC-4 phosphorylation. Furthermore, we demonstrate that ALP-1 associates with LET-502 and MLC-4. Thus, ALP-1 serves as a platform to activate MLC-4 phosphorylation mediated by the RHO-1-LET-502 signaling pathway.

Enigma Plays Roles in Survival of Thyroid Carcinoma Cells through PI3K/AKT Signaling and Survivin.

The aim of the present study was to assess the role of enigma protein in survival of thyroid carcinoma cells. BCPAP and 8505C human thyroid carcinoma cells were used. Cell viability using CCK-8 assay, the percentage of dead cells using trypan blue assay, cytotoxic activity using cytotoxicity assay, cell growth rate and cell migration using wound-healing assay were performed. In enigma siRNA-transfected cells, cell viability, and the protein levels of AKT and survivin decreased. The percentage of dead cells, cytotoxic activity and cleaved poly (ADP-ribose) polymerase (PARP) protein levels increased. After transfection of p110α plasmid, the alterations in cell viability, the percentage of dead cells, cytotoxic activity, and protein levels of AKT, survivin and cleaved PARP were abrogated. Cell growth rate and cell migration were reduced with reduction of matrix metalloproteinase-2 (MMP-2) and matrix metalloproteinase-9 (MMP-9) protein levels, as well as increased p53 and p21 protein levels. Enigma affects cell survival through modulation of phosphatidylinositol-3 kinase/AKT signaling and survivin, and regulates cell proliferation and migration via involvement of MMP-2, MMP-9, p53 and p21 in thyroid carcinoma cells.

CLP36 interacts with palladin in dorsal root ganglion neurons

CLP36, a member of the alpha-actinin-associated LIM protein (ALP)/enigma protein family, plays a role in neurite outgrowth in the peripheral nervous system. However, the underlying molecular mechanisms are not known. In this study, we performed yeast two-hybrid screening of an E18 mouse whole-body cDNA library with CLP36 as the bait and isolated palladin as a CLP36-binding protein. Palladin is an actin-binding protein and it was shown to have a role in the extension of cortical neurons. A coimmunoprecipitation study showed that CLP36 and palladin formed a complex in the dorsal root ganglion (DRG). In addition, CLP36 and palladin were colocalized in the neurites and cell bodies of primary DRG neurons. Furthermore, sciatic nerve transection increased the expression of both CLP36 and palladin mRNAs in DRG neurons, with the increase in CLP36 mRNA being more prominent. This implies that CLP36 has a more specific role in nerve regeneration than palladin. Our results suggest that CLP36 may interact with palladin to influence neurite outgrowth during sciatic nerve regeneration.

ALP/Enigma PDZ-LIM Domain Proteins in the Heart

Actinin-associated LIM protein (ALP) and Enigma are two subfamilies of Postsynaptic density 95, discs large and zonula occludens-1 (PDZ)-Lin-11, Isl1 and Mec-3 (LIM) domain containing proteins. ALP family members have one PDZ and one LIM domain, whereas Enigma proteins contain one PDZ and three LIM domains. Four ALP and three Enigma proteins have been identified in mammals, each having multiple splice variants and unique expression patterns. Functionally, these proteins bind through their PDZ domains to alpha-actinin and bind through their LIM domains or other internal protein interaction domains to other proteins, including signaling molecules. ALP and Enigma proteins have been implicated in cardiac and skeletal muscle structure, function and disease, neuronal function, bipolar disorder, tumor growth, platelet and epithelial cell motility and bone formation. This review will focus on recent advances in the biological roles of ALP/Enigma PDZ-LIM domain proteins in cardiac muscle and provide insights into mechanisms by which mutations in these proteins are related to human cardiac disease.

Differential interaction of Enigma protein with the two RET isoforms

The receptor tyrosine kinase RET, with a known role in embryonic development and in human pathologies, is alternatively spliced to yield at least two functional isoforms, which differ only in their carboxyl terminal. Enigma protein is a member of the PDZ–LIM family and is known to interact with the short isoform of RET/PTC2, a chimeric oncoprotein isolated from papillary thyroid carcinoma. Here, we show that Enigma also interacts in intact cells with the short isoform of RET-wt and of its pathologic mutants associated to MEN2 syndromes, RET-C634R and RET-M918T. In contrast, Enigma binds all the corresponding RET long isoforms very poorly and colocalizes with short but not long RET/PTC2 isoforms. The RET docking tyrosine for Enigma is the last but one before the divergence between the two isoforms and we demonstrated that short-isoform-specific amino acid residues +2 to +4 to this tyrosine are required for the interaction of RET/PTC2 with Enigma.

Elfin is expressed during early heart development.

Elfin (previously named CLIM1) is a protein that possesses an N-terminal PDZ domain and a C-terminal LIM domain. It belongs to the family of Enigma proteins. Enigma proteins are a family of cytoplasmic proteins that contain an N-terminal PDZ domain and a series of C-terminal LIM domains. By virtue of these two protein interacting domains, Enigma proteins are capable of protein-protein interactions. It has been proposed that Enigma proteins may act as adapters between kinases and the cytoskeleton. We have previously shown that Elfin is most abundantly expressed in the heart and it colocalizes with alpha-actinin 2 at the Z-disks of the myocardium. In this report, Elfin was shown to localize at the actin stress fibers of myoblasts, as revealed by green fluorescent protein (GFP) tagging. In situ hybridization and immunostaining showed that Elfin expression begins at an early stage in mouse development and is present throughout the developing heart. Taken together, our experimental results suggest that Elfin may play an important role in myofibrillogenesis and heart development.

Oracle, a novel PDZ-LIM domain protein expressed in heart and skeletal muscle

In order to identify novel genes enriched in adult heart, we performed a subtractive hybridization for genes expressed in mouse heart but not in skeletal muscle. We identified two alternative splicing variants of a novel PDZ-LIM domain protein, which we named Oracle. Both variants contain a PDZ domain at the amino-terminus and three LIM domains at the carboxy-terminus. Highest homology of Oracle was found with the human and rat enigma proteins in the PDZ domain (62 and 61%, respectively) and in the LIM domains (60 and 69%, respectively). By Northern hybridization analysis, we showed that expression is highest in adult mouse heart, low in skeletal muscle and undetectable in other adult mouse tissues. In situ hybridization in mouse embryos confirmed and extended these data by showing high expression of Oracle mRNA in atrial and ventricular myocardial cells from E8.5. From E9.5 low expression of Oracle mRNA was detectable in myotomes. These data suggest a role for Oracle in the early development and function of heart and skeletal muscle.

Interaction of hCLIM1, an enigma family protein, with alpha-actinin 2.

Enigma proteins are proteins that possess a PDZ domain at the amino terminal and one to three LIM domains at the carboxyl terminal. They are cytoplasmic proteins that are involved with the cytoskeleton and signal transduction pathway. By virtue of the two protein interacting domains, they are capable of protein-protein interactions. Here we report a study on a human Enigma protein hCLIM1, in particular. Our study describes the interaction of the human 36 kDa carboxyl terminal LIM domain protein (hCLIM1), the human homologue of CLP36 in rat, with alpha-actinin 2, the skeletal muscle isoform of alpha-actinin. hCLIM1 protein was shown to interact with alpha-actinin 2 by yeast two-hybrid screening and immunochemical analyses. Yeast two-hybrid analyses also demonstrated that the LIM domain of hCLIM1 binds to the EF-hand region of alpha-actinin 2, defining a new mode of LIM domain interactions. Immunofluorescent study demonstrates that hCLIM1 colocalizes with alpha-actinin at the Z-disks in human myocardium. Taken together, our experimental results suggest that hCLIM1is a novel cytoskeletal protein and may act as an adapter that brings other proteins to the cytoskeleton.