Beyond structure: do intermediate filaments modulate cell signalling?

Transcriptome and computational approaches highlighting the molecular regulation of Zacco platypus induced by mesocosm exposure to common disinfectant chlorine

Chlorine (Cl₂) is a disinfectant often used in swimming pools and water treatment facilities. However, it is released into aquatic ecosystems, where it may harm non-targeted organisms. Here, we performed a mesocosm experiment exposing Zacco platypus (Z. platypus) to biocide Cl₂ for 30 days (30 d) at two days' time points 15 days (15 d) and 30 d samples were collected. Here, Z. platypus was exposed to a sublethal concentration (0.1 mg/L) of Cl₂, and comparative transcriptomics analyses were performed to determine their response mechanisms at the molecular level. According to RNA sequencing of the whole-body transcriptome, 860 and 1189 differentially expressed genes (DEGs) were identified from the 15 d and 30 d responses to Cl₂, respectively. After enrichment analysis of GO (Gene Ontology) functions and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathways, identified DEGs were demonstrated to be associated with a variety of functions, including "ion binding and transmembrane transporters". Cl₂ also induced oxidative stress in Z. platypus by increasing the levels of reactive oxygen species (ROS) while decreasing the catalase (CAT) content and the levels of solute carrier family 22 member 11 (slc22a11), Caspase-8 (casp-8), inducible nitric oxide synthase (NOS2), cytosolic phospholipase A2 gamma (PLA2G4). However, Z. platypus still allows recovery during stress suspension by increasing the expression levels of solute carrier family proteins. The GO and KEGG annotation results revealed that the expression of DEGs were related to the detoxification process, immune response, and antioxidant mechanism. Additionally, protein-protein interaction networks (PPI) and cytoHubba analyses identified sixteen hub genes and their interaction. These findings elucidate the regulation of various DEGs and signaling pathways in response to Cl₂ exposure, which will improve our knowledge and laid foundation for further investigation of the toxicity of Cl₂ to Z. platypus.

ARID2 suppression promotes tumor progression and upregulates cytokeratin 8, 18 and β-4 integrin expression in TP53-mutated tobacco-related oral cancer and has prognostic implications

Mutations in ARID2 and TP53 genes are found to be implicated in the tobacco related tumorigeneses. However, the effect of loss of ARID2 in the TP53 mutated background in tobacco related cancer including oral cancer has not been investigated yet. Hence, in this study we knockdown ARID2 using shRNA mediated knockdown strategy in TP53 mutated oral squamous cell carcinoma (OSCC) cell line and studied its tumorigenic role. Our study revealed that suppression of ARID2 in TP53 mutated oral cancer cells increases cell motility and invasion, induces drastic morphological changes and leads to a marked increase in the expression levels of cytokeratins, and integrins, CK8, CK18 and β4-Integrin, markers of cell migration/invasion in oral cancer. ARID2 suppression also showed early onset and increased tumorigenicity in-vivo. Interestingly, transcriptome profiling revealed differentially expressed genes associated with migration and invasion in oral cancer cells including AKR1C2, NCAM2, NOS1, ADAM23 and genes of S100A family in ARID2 knockdown TP53 mutated oral cancer cells. Pathway analysis of differentially regulated genes identified "cancer pathways" and "PI3K/AKT Pathway" to be significantly dysregulated upon suppression of ARID2 in TP53 mutated OSCC cells. Notably, decreased ARID2 expression and increased CK8, CK18 expression leads to poor prognosis in Head and Neck cancer (HNSC) patients as revealed by Pan-Cancer TCGA data analysis. To conclude, our study is the first to demonstrate tumor suppressor role of ARID2 in TP53 mutated background indicating their cooperative role in OSCC, and also highlights its prognostic implications suggesting ARID2 as an important therapeutic target in OSCC.

Changes in cardiac proteome and metabolome following exposure to the PAHs retene and fluoranthene and their mixture in developing rainbow trout alevins

Exposure to polycyclic aromatic hydrocarbons (PAHs) is known to affect developing organisms. Utilization of different omics-based technologies and approaches could therefore provide a base for the discovery of novel mechanisms of PAH induced development of toxicity. To this aim, we investigated how exposure towards two PAHs with different toxicity mechanisms: retene (an aryl hydrocarbon receptor 2 (Ahr2) agonist), and fluoranthene (a weak Ahr2 agonist and cytochrome P450 inhibitor (Cyp1a)), either alone or as a mixture, affected the cardiac proteome and metabolome in newly hatched rainbow trout alevins (Oncorhynchus mykiss). In total, we identified 65 and 82 differently expressed proteins (DEPs) across all treatments compared to control (DMSO) after 7 and 14 days of exposure. Exposure to fluoranthene altered the expression of 11 and 19 proteins, retene 29 and 23, while the mixture affected 44 and 82 DEPs by Days 7 and 14, respectively. In contrast, only 5 significantly affected metabolites were identified. Pathway over-representation analysis identified exposure-specific activation of phase II metabolic processes, which were accompanied with exposure-specific body burden profiles. The proteomic data highlights that exposure to the mixture increased oxidative stress, altered iron metabolism and impaired coagulation capacity. Additionally, depletion of several mini-chromosome maintenance components, in combination with depletion of several intermediate filaments and microtubules, among alevins exposed to the mixture, suggests compromised cellular integrity and reduced rate of mitosis, whereby affecting heart growth and development. Furthermore, the combination of proteomic and metabolomic data indicates altered energy metabolism, as per amino acid catabolism among mixture exposed alevins; plausibly compensatory mechanisms as to counteract reduced absorption and consumption of yolk. When considered as a whole, proteomic and metabolomic data, in relation to apical effects on the whole organism, provides additional insight into PAH toxicity and the effects of exposure on heart structure and molecular processes.

Nucleobindin-2 consists of two structural components: The Zn2+-sensitive N-terminal half, consisting of nesfatin-1 and -2, and the Ca2+-sensitive C-terminal half, consisting of nesfatin-3

Nucleobindin-2 (Nucb2) is a protein that has been suggested to play roles in a variety of biological processes. Nucb2 contains two Ca2+/Mg2+-binding EF-hand domains separated by an acidic amino acid residue-rich region and a leucine zipper. All of these domains are located within the C-terminal half of the protein. At the N-terminal half, Nucb2 also possesses a putative Zn2+-binding motif. In our recent studies, we observed that Nucb2 underwent Ca2+-dependent compaction and formed a mosaic-like structure consisting of intertwined disordered and ordered regions at its C-terminal half. The aim of this study was to investigate the impact of two other potential ligands: Mg2+, which possesses chemical properties similar to those of Ca2+, and Zn2+, for which a putative binding motif was identified. In this study, we demonstrated that the binding of Mg2+ led to oligomerization state changes with no significant secondary or tertiary structural alterations of Nucb2. In contrast, Zn2+ binding had a more pronounced effect on the structure of Nucb2, leading to the local destabilization of its N-terminal half while also inducing changes within its C-terminal half. These structural rearrangements resulted in the oligomerization and/or aggregation of Nucb2 molecules. Taken together, the results of our previous and current research help to elucidate the structure of the Nucb2, which can be divided into two parts: the Zn2+-sensitive N-terminal half (consisting of nesfatin-1 and -2) and the Ca2+-sensitive C-terminal half (consisting of nesfatin-3). These results may also help to open a new discussion regarding the diverse roles that metal cations play in regulating the structure of Nucb2 and the various physiological functions of this protein.

Effects of Diabetes Mellitus on Sperm Quality in the Db/Db Mouse Model and the Role of the FoxO1 Pathway

Background

Studies have shown that diabetes mellitus (DM) has a negative impact on male reproductive function, which may lead to changes in the testis and epididymis and a decline in semen quality.

Material/Methods

We performed animal experiments with 6 diabetic db/db mice as the model group (group B) and 6 C57BL/6J mice as the control group (group A). After adaptive feeding for 7 days, the sperm quality of each group was measured. Concurrently, the morphology of the mouse testis was observed by hematoxylin-eosin (H&E) staining. The expression of the PI3K, Akt, FoxO1, FasL, IL-6, and Stat3 proteins and mRNAs in the testicular tissue was detected by western blotting and RT-qPCR.

Results

The number of spermatozoa and sperm motility of group A was significantly higher than that of group B (P<0.05). H&E staining of the testicular tissue showed the seminiferous tubules in group B mice were damaged to varying degrees and the seminiferous tubules were sparsely arranged. Compared with those of group A, the expression levels of PI3K, Akt, and Stat3 proteins and mRNAs in group B were significantly lower (P<0.05), while the expression levels of FoxO1, FasL, and IL-6 proteins and mRNAs in group B mice were significantly higher (P<0.05).

Conclusions

This study demonstrated that DM inhibited the expression of PI3K, Akt, and Stat3 proteins and mRNAs in the FoxO1 pathway and promoted the expression of FoxO1, FasL, and IL-6 proteins and mRNAs, leading to abnormal apoptosis of testicular tissue cells and functional damage, and eventually spermatogenic dysfunction.

Mechanical and Non-Mechanical Functions of Filamentous and Non-Filamentous Vimentin

Intermediate filaments (IFs) formed by vimentin are less understood than their cytoskeletal partners, microtubules and F-actin, but the unique physical properties of IFs, especially their resistance to large deformations, initially suggest a mechanical function. Indeed, vimentin IFs help regulate cell mechanics and contractility, and in crowded 3D environments they protect the nucleus during cell migration. Recently, a multitude of studies, often using genetic or proteomic screenings show that vimentin has many non-mechanical functions within and outside of cells. These include signaling roles in wound healing, lipogenesis, sterol processing, and various functions related to extracellular and cell surface vimentin. Extracellular vimentin is implicated in marking circulating tumor cells, promoting neural repair, and mediating the invasion of host cells by viruses, including SARS-CoV, or bacteria such as Listeria and Streptococcus. These findings underscore the fundamental role of vimentin in not only cell mechanics but also a range of physiological functions. Also see the video abstract here https://youtu.be/YPfoddqvz-g.

Intermediate filaments in developing neurons: Beyond structure

Neuronal development relies on a highly choreographed progression of dynamic cellular processes by which newborn neurons migrate, extend axons and dendrites, innervate their targets, and make functional synapses. Many of these dynamic processes require coordinated changes in morphology, powered by the cell's cytoskeleton. Intermediate filaments (IFs) are the third major cytoskeletal elements in vertebrate cells, but are rarely considered when it comes to understanding axon and dendrite growth, pathfinding and synapse formation. In this review, we first introduce the many new and exciting concepts of IF function, discovered mostly in non-neuronal cells. These roles include dynamic rearrangements, crosstalk with microtubules and actin filaments, mechano-sensing and -transduction, and regulation of signaling cascades. We then discuss the understudied roles of neuronally expressed IFs, with a particular focus on IFs expressed during development, such as nestin, vimentin and α-internexin. Lastly, we illustrate how signaling modulation by the unconventional IF nestin shapes neuronal morphogenesis in unexpected and novel ways. Even though the first IF knockout mice were made over 20 years ago, the study of the cell biological functions of IFs in the brain still has much room for exciting new discoveries.

Plasticity of endometrial epithelial and stromal cells-A new approach towards the pathogenesis of equine endometrosis

Equine endometrosis, a frequent cause of subfertility, is characterized by periglandular fibrosis, and no treatment exists. Endometrial biopsies not only contain diseased glands, but also contain healthy glands and stroma. Myoepithelial (ME) and myofibroblastic (MF) markers are calponin, smooth muscle actin (SMA), desmin and glial fibrillary acidic protein (GFAP). Epithelial vimentin expression indicates epithelial to mesenchymal transition (EMT). The aim of this immunohistochemical study was to investigate whether biopsies with endometrosis express MF and ME markers and vimentin. Compared to healthy areas, significantly higher percentages of endometrotic glands were lined by calponin- and vimentin-positive epithelial cells, whereas periglandular fibrosis contained significantly higher percentages of stromal cells positive for vimentin, desmin and SMA and significantly less calponin-positive stromal cells. The rare GFAP expression was restricted to endometrotic glands. Of these, the most frequent features of endometrotic glands were higher percentages of SMA- and vimentin-positive stromal cells and the prominent epithelial calponin staining that occurred in 100%, 93% and 95% of examined biopsies. Results indicate plasticity of equine endometrial epithelial and stromal cells. Particularly, endometrotic glands show evidence for ME differentiation and EMT. The different expression of MF markers between stromal cells from healthy and endometrotic areas suggests functional differences. The characteristic changes in the expression of SMA, vimentin and calponin between endometrotic glands and healthy areas can be helpful to confirm early stages of endometrosis. The characterization of cellular differentiation may help to decipher the pathogenesis of endometrosis and could lead to therapeutic strategies.

Significance of Cytokeratin-1 Single-Nucleotide Polymorphism and Protein Level in Susceptibility to Vocal Leukoplakia and Laryngeal Squamous Cell Carcinoma

OBJECTIVE

To investigate the association between the cytokeratin (CK)-1 single-nucleotide polymorphism (SNP), the protein level of CK-1 and the risk of vocal leukoplakia and laryngeal squamous cell carcinoma (LSCC).

METHODS

In this case-control study, 155 patients with vocal leukoplakia, 323 patients with LSCC, and 266 healthy controls were genotyped for the CK-1 (SNP RS14024) gene using pyrosequencing. The protein expression level of CK-1 was analyzed in vocal leukoplakia, LSCC, and vocal polyp patients by immunohistochemistry (IHC).

RESULTS

Of the CK-1 RS14024 polymorphism, the heterozygote AG and homozygote GG genotype exhibited a significantly increased risk of LSCC (AG: OR = 2.16, p = 0.014; GG: OR = 2.15, p = 0.018) compared to normal controls. A higher protein expression level of CK-1 was detected in patients with LSCC compared to vocal leukoplakia and polyps (both p < 0.001), and a significant increasing trend of CK-1 protein expression level from mild-moderate dysplasia to moderate-severe dysplasia in vocal leukoplakia patients was also observed (p = 0.006).

CONCLUSIONS

This study demonstrates that the CK-1 SNP and high protein expression levels are associated with vocal leukoplakia and LSCC and promote the transformation from vocal leukoplakia to LSCC in a Chinese Han population.

Anti-vimentin antibodies in transplant and disease

Non-HLA antibodies are recognized as a potential source of antibody mediated rejection following transplantation. The epitopes which lead to production of these antibodies are a result of tissue disruption, specifically endothelium, secondary to inflammation and injury. Vimentin is a cytoskeletal protein involved in many aspects of cellular organization, signaling, and proliferation. Recently, antivimentin antibodies have been shown to be important not only for rheumatological autoimmune diseases, but also cardiac and renal transplant dysfunction. In cardiac transplant recipients, antivimentin antibodies are associated with coronary artery vasculopathy and chronic graft loss. In renal transplantation, antivimentin antibodies are detected prior to transplantation and are also correlated with chronic graft dysfunction. In renal transplant recipients, antivimentin antibodies seen prior to transplantation are thought to be secondary to chronic endothelial injury during hemodialysis and therefore more prevalent prior to renal transplant than cardiac transplantation. In this review, we will examine the generation and pathogenesis of antivimentin antibodies. Given that these antibodies appear to be associated with both post-cardiac and -renal transplant dysfunction, developing standard detection paradigms may be important for risk stratification prior to transplantation. Finally, understanding the pathogenesis of antivimentin antibodies may lead to the development potential therapies in order to improve long-term survival.

Cytoplasmic Intermediate Filaments in Cell Biology

Intermediate filaments (IFs) are one of the three major elements of the cytoskeleton. Their stability, intrinsic mechanical properties, and cell type-specific expression patterns distinguish them from actin and microtubules. By providing mechanical support, IFs protect cells from external forces and participate in cell adhesion and tissue integrity. IFs form an extensive and elaborate network that connects the cell cortex to intracellular organelles. They act as a molecular scaffold that controls intracellular organization. However, IFs have been revealed as much more than just rigid structures. Their dynamics is regulated by multiple signaling cascades and appears to contribute to signaling events in response to cell stress and to dynamic cellular functions such as mitosis, apoptosis, and migration.

Vimentin expression is required for the development of EMT-related renal fibrosis following unilateral ureteral obstruction in mice

Most renal transplants ultimately fail secondary to chronic allograft nephropathy (CAN). Vimentin (vim) is a member of the intermediate filament family of proteins and has been shown to be important in the development of CAN. One of the pathways leading to chronic renal fibrosis after transplant is thought to be epithelial to mesenchymal transition (EMT). Even though vim expression is one of the main steps of EMT, it is unknown whether vim expression is required for EMT leading to renal fibrosis and allograft loss. To this end, the role of vim in renal fibrosis was determined via unilateral ureteral obstruction (UUO) in vim knockout mice (129 svs6 vim -/-). Following UUO, kidneys were recovered and analyzed via Western blotting, immunofluorescence, and transcriptomics. Cultured human proximal renal tubular (HK-2) cells were subjected to lentiviral-driven inhibition of vim expression and then treated with transforming growth factor (TGF)-β to undergo EMT. Immunoblotting as well as wound healing assays were used to determine development of EMT. Western blotting analyses of mice undergoing UUO reveal increased levels of vim soon after UUO. As expected, interstitial collagen deposition increased in control mice following UUO but decreased in vim -/- kidneys. Immunofluorescence analyses also revealed altered localization of β-catenin in vim -/- mice undergoing UUO without significant changes in mRNA levels. However, RNA sequencing revealed a decrease in β-catenin-dependent genes in vim -/- kidneys. Finally, vim-silenced HK-2 cell lines undergoing EMT were shown to have decreased cellular migration during wound healing. We conclude that vim inhibition decreases fibrosis following UUO by possibly altering β-catenin localization and downstream signaling.

Absence of synemin in mice causes structural and functional abnormalities in heart

Cardiomyopathies have been linked to changes in structural proteins, including intermediate filament (IF) proteins located in the cytoskeleton. IFs associate with the contractile machinery and costameres of striated muscle and with intercalated disks in the heart. Synemin is a large IF protein that mediates the association of desmin with Z-disks and stabilizes intercalated disks. It also acts as an A-kinase anchoring protein (AKAP). In murine skeletal muscle, the absence of synemin causes a mild myopathy. Here, we report that the genetic silencing of synemin in mice (synm -/-) causes left ventricular systolic dysfunction at 3months and 12-16months of age, and left ventricular hypertrophy and dilatation at 12-16months of age. Isolated cardiomyocytes showed alterations in calcium handling that indicate defects intrinsic to the heart. Although contractile and costameric proteins remained unchanged in the old synm -/- hearts, we identified alterations in several signaling proteins (PKA-RII, ERK and p70S6K) critical to cardiomyocyte function. Our data suggest that synemin plays an important regulatory role in the heart and that the consequences of its absence are profound.

STK33 Promotes Growth and Progression of Pancreatic Cancer as a Critical Downstream Mediator of HIF1α

The serine/threonine kinase STK33 has been implicated in cancer cell proliferation. Here, we provide evidence of a critical role for STK33 in the pathogenesis and metastatic progression of pancreatic ductal adenocarcinoma (PDAC). STK33 expression in PDAC was regulated by the hypoxia-inducible transcription factor HIF1α. In human PDAC specimens, STK33 was overexpressed and associated with poor prognosis. Enforced STK33 expression promoted PDAC proliferation, migration, invasion, and tumor growth, whereas STK33 depletion exerted opposing effects. Mechanistic investigations showed that HIF1α regulated STK33 via direct binding to a hypoxia response element in its promoter. In showing that dysregulated HIF1α/STK33 signaling promotes PDAC growth and progression, our results suggest STK33 as a candidate therapeutic target to improve PDAC treatment. Cancer Res; 77(24); 6851-62. ©2017 AACR.

Molecular Regulation of Sprouting Angiogenesis

The term angiogenesis arose in the 18th century. Several studies over the next 100 years laid the groundwork for initial studies performed by the Folkman laboratory, which were at first met with some opposition. Once overcome, the angiogenesis field has flourished due to studies on tumor angiogenesis and various developmental models that can be genetically manipulated, including mice and zebrafish. In addition, new discoveries have been aided by the ability to isolate primary endothelial cells, which has allowed dissection of various steps within angiogenesis. This review will summarize the molecular events that control angiogenesis downstream of biochemical factors such as growth factors, cytokines, chemokines, hypoxia-inducible factors (HIFs), and lipids. These and other stimuli have been linked to regulation of junctional molecules and cell surface receptors. In addition, the contribution of cytoskeletal elements and regulatory proteins has revealed an intricate role for mobilization of actin, microtubules, and intermediate filaments in response to cues that activate the endothelium. Activating stimuli also affect various focal adhesion proteins, scaffold proteins, intracellular kinases, and second messengers. Finally, metalloproteinases, which facilitate matrix degradation and the formation of new blood vessels, are discussed, along with our knowledge of crosstalk between the various subclasses of these molecules throughout the text. Compr Physiol 8:153-235, 2018.

Phthalocyanine-BODIPY dye: synthesis, characterization, and utilization for pattern recognition of CYFRA 21-1 in whole blood samples

Phthalocyanine-BODIPY dye (BODIPY = boron dipyrromethene) was synthesized, fully characterized, and used for molecular recognition of CYFRA 21-1, a lung cancer biomarker, from whole blood samples. Thin films of three magnesium oxides ((MgO) _n , where n = 8, 9, or 10)) were deposited on a paper substrate, and they were immersed in a solution of phthalocyanine-BODIPY dye (1.17 × 10^-3 mol/L) for the design of stochastic sensors. Limits of determination of picograms per milliliter magnitude order were recorded for the proposed stochastic sensors. CYFRA 21-1 was reliably identified and determined with recoveries higher than 95% and RSD lower than 1% in whole blood samples.

Anti-vimentin Antibodies Present at the Time of Transplantation May Predict Early Development of Interstitial Fibrosis/Tubular Atrophy

BACKGROUND

Anti-vimentin (a cytoskeletal protein) autoantibodies in renal transplant recipients have been correlated with interstitial fibrosis/tubular atrophy (IFTA). In this study, we examine the association between pretransplantation anti-vimentin antibodies and the subsequent development of IFTA.

METHODS

Sera obtained before renal transplantation from 97 transplant recipients were analyzed for the presence of anti-vimentin antibodies via Luminex assays to determine the concentration of anti-vimentin antibodies. Results were correlated with findings of IFTA on biopsy as well as graft function and patient and graft survival.

RESULTS

In our patient population, 56 of 97 patients were diagnosed by biopsy with IFTA 2.9 (±2.1) years after renal transplantation. Patients with IFTA on biopsy had higher mean concentration of anti-vimentin antibodies when compared to patients without IFTA (32.2 μg/mL [3.97-269.12 μg/mL] vs 14.57 μg/mL [4.71-87.81 μg/mL]). The risk of developing IFTA with a concentration of anti-vimentin antibody >15 μg/mL before transplantation was 1.96 (95% CI = 1.38-2.79, P = .011). Patients with elevated anti-vimentin antibody concentrations (>15 μg/mL) at the time of transplantation also had a higher risk of developing IFTA (81.4% vs 41.2%; P < .05). In addition, graft function was worse at 1, 3, and 5 years posttransplantation in patients with elevated concentrations of pretransplantation anti-vimentin antibody. Although there were more graft losses in the IFTA groups (49.12% vs 25.64%, P = .021) and the IFTA patients loss their grafts earlier (4.3 years vs 3.6 years), there was no statistical difference in graft loss rates.

CONCLUSIONS

Pretransplantation anti-vimentin antibody concentrations >15 μg/mL may be a risk factor for IFTA.

Deficiency of the intermediate filament synemin reduces bone mass in vivo

While the type IV intermediate filament protein, synemin, has been shown to play a role in striated muscle and neuronal tissue, its presence and function have not been described in skeletal tissue. Here, we report that genetic ablation of synemin in 14-wk-old male mice results in osteopenia that includes a more than 2-fold reduction in the trabecular bone fraction in the distal femur and a reduction in the cross-sectional area at the femoral middiaphysis due to an attendant reduction in both the periosteal and endosteal perimeter. Analysis of serum markers of bone formation and static histomorphometry revealed a statistically significant defect in osteoblast activity and osteoblast number in vivo. Interestingly, primary osteoblasts isolated from synemin-null mice demonstrate markedly enhanced osteogenic capacity with a concomitant reduction in cyclin D1 mRNA expression, which may explain the loss of osteoblast number observed in vivo. In total, these data suggest an important, previously unknown role for synemin in bone physiology.

Gene Expression Architecture of Mouse Dorsal and Tail Skin Reveals Functional Differences in Inflammation and Cancer

Inherited germline polymorphisms can cause gene expression levels in normal tissues to differ substantially between individuals. We present an analysis of the genetic architecture of normal adult skin from 470 genetically unique mice, demonstrating the effect of germline variants, skin tissue location, and perturbation by exogenous inflammation or tumorigenesis on gene signaling pathways. Gene networks related to specific cell types and signaling pathways, including sonic hedgehog (Shh), Wnt, Lgr family stem cell markers, and keratins, differed at these tissue sites, suggesting mechanisms for the differential susceptibility of dorsal and tail skin to development of skin diseases and tumorigenesis. The Pten tumor suppressor gene network is rewired in premalignant tumors compared to normal tissue, but this response to perturbation is lost during malignant progression. We present a software package for expression quantitative trait loci (eQTL) network analysis and demonstrate how network analysis of whole tissues provides insights into interactions between cell compartments and signaling molecules.

Cytokeratin and protein expression patterns in squamous cell carcinoma of the oral cavity provide evidence for two distinct pathogenetic pathways

Squamous cell carcinoma (SCC) of the oral cavity is a morphological heterogeneous disease. Various cytokeratin (CK) expression patterns with different prognostic values have been described, but little is known concerning the underlying biological cell mechanisms. Therefore, the present study investigated 193 cases of oral SCCs using immunohistochemistry for α/β/γ-catenin, glucose transporter 1, caspase-3, X-linked inhibitor of apoptosis protein, hypoxia inducible factor-1α, carbonic anhydrase 9, heat shock protein (hsp) 70, mast/stem cell growth factor receptor, p21, p27, p16, p53, B-cell lymphoma 6, epidermal growth factor receptor, cyclin D1 and CK1, 5/6, 8/18, 10, 14 and 19. Expression patterns were analyzed with biomathematical permutation analysis. The present results revealed a significant association between the expression of low-molecular weight CK8/18 and 19 and a high-tumor grade, β and γ-catenin expression, deregulated cell cycle proteins and a predominant localization of the tumor on the floor of the mouth. By contrast, expression of high-molecular weight CK1, 5/6, 10 and 14 was significantly associated with the expression of p21 and hsp70. In conclusion, the current study presents evidence for the existence of two parallel pathogenetic pathways in oral SCCs, characterized by the expression of low- and high-molecular weight CKs. Additional studies are required to demonstrate the extent that these results may be used to improve therapeutic regimens.

Zearalenone impairs the male reproductive system functions via inducing structural and functional alterations of sertoli cells

The aim of this study was to investigate the effects of ZEA on the cytoskeletal structure, and factors specifically expressed by Sertoli cells. Primary Sertoli cells from rats aged 18-21 days were exposed to increasing ZEA concentrations (0, 5, 10, 20 μg mL(-1)) for 24 h. The results of immunofluorescence showed disruption of α-tubulin filaments and F-actin bundles, and damage to the nucleus of Sertoli cells on exposure to ZEA. In the control group, the protein level expression of androgen-binding protein (ABP), transferrin, vimentin, N-cadherin, and follicle-stimulating hormone receptor (FSHR) were decreased significantly (p<0.05, p<0.01). The mRNA levels of ABP, transferrin, vimentin, N-cadherin, and FSHR varied significantly in the experimental group (p<0.05). The results of enzyme-linked immunosorbent assay indicated a significant decrease in the levels of inhibin-β and transferrin in the cultural supernatants (p<0.05). Additionally, the ultrastructural analysis indicated the absence of mitochondria and Golgi apparatus, and presence of vacuoles in the cytoplasm. These findings showed that ZEA treatment can damage the cytoskeletal structure and affect specific secretory functions of Sertoli cells, which may be an underlying cause of ZEA-induced reproductive toxicity.

Downregulation of cytokeratin 18 is associated with paclitaxel‑resistance and tumor aggressiveness in prostate cancer

Paclitaxel frequently serves as the first-line chemotherapeutic agent for castration-resistant prostate cancer (PCa) patients. However, acquired paclitaxel-resistance almost always occurs after initial responses, and the mechanisms by which this occurs remain largely unknown. The goal of the present study was to identify differentially expressed protein(s) associated with paclitaxel-resistance and further explore the potential mechanisms involved in drug resistance. By comparing the nuclear matrix protein (NMP) patterns of DU145-TxR cells, the previously established stable paclitaxel-resistant PCa cells, with that of the parental DU145 cells using two-dimensional electrophoresis, we found that cytokeratin 18 (CK18) is downregulated in DU145-TxR cells. The downregulation of CK18 in DU145-TxR cells at mRNA, NMP and total cellular protein levels was validated by real-time RT-PCR, immunoblotting and immunofluorescence, indicating that the downregulation of CK18 was a global effect in DU145-TxR cells due to paclitaxel-resistance. Furthermore, in vivo assay of xenograft transplantation confirmed the higher tumorigenicity of DU145-TxR cells, suggesting that these paclitaxel-resistant PCa cells possessed potent cancer stem cell (CSC)-like properties and eventually developed paclitaxel-resistance. Moreover, we determined by immunohistochemistry that CK18 expression in PCa tissues was inversely correlated with tumor grade in a statistically significant fashion, indicating a potential association of the downregulation of CK18 with tumor aggressiveness. Therefore, further study to define the potential role of CK18 may lead to novel therapy strategies as well as clinically useful biomarker for PCa patients.

Vimentin filament organization and stress sensing depend on its single cysteine residue and zinc binding

The vimentin filament network plays a key role in cell architecture and signalling, as well as in epithelial-mesenchymal transition. Vimentin C328 is targeted by various oxidative modifications, but its role in vimentin organization is not known. Here we show that C328 is essential for vimentin network reorganization in response to oxidants and electrophiles, and is required for optimal vimentin performance in network expansion, lysosomal distribution and aggresome formation. C328 may fulfil these roles through interaction with zinc. In vitro, micromolar zinc protects vimentin from iodoacetamide modification and elicits vimentin polymerization into optically detectable structures; in cells, zinc closely associates with vimentin and its depletion causes reversible filament disassembly. Finally, zinc transport-deficient human fibroblasts show increased vimentin solubility and susceptibility to disruption, which are restored by zinc supplementation. These results unveil a critical role of C328 in vimentin organization and open new perspectives for the regulation of intermediate filaments by zinc.

Serum cytokeratin-19 fragment (Cyfra 21-1) is a prognostic indicator for epithelial ovarian cancer

OBJECTIVES

Cytokeratin 19 is significant for indicating cancer cells, and Cyfra 21-1 is a fragment of cytokeratin 19. This retrospective study was designed to define the prognostic value of serum Cyfra 21-1 in epithelial ovarian cancers (EOC).

MATERIALS AND METHODS

Serum Cyfra 21-1 concentration was obtained from 42 patients with EOC prior to treatment. Various prognostic aspects were examined using univariable and multivariable analyses. The standard serum marker cancer antigen 125 was measured simultaneously and compared in this analysis.

RESULTS

Serum levels of both Cyfra 21-1 and cancer antigen 125 were associated with positive retroperitoneal lymph nodes and platinum resistance; higher levels of Cyfra 21-1 (3.0 ng/mL as the cut-off) were associated with shorter disease-free survival (16 months vs. 28 months, p = 0.001) and overall survival (29 months vs. 41 months, p = 0.007) than lower levels. Further univariable analysis showed that Cyfra 21-1, poor differentiation, and retroperitoneal lymph node metastasis were related to platinum resistance and mortality. Multivariable analysis indicated retroperitoneal lymph node metastasis and serum Cyfra 21-1 were independent risk factors for both disease-free survival and overall survival.

CONCLUSION

The pretreatment level of serum Cyfra 21-1 had remarkable prognostic significance for EOC, indicating poor survival when it was elevated above 3.0 ng/mL.

Vimentin as an integral regulator of cell adhesion and endothelial sprouting

Angiogenesis is a multistep process that requires intricate changes in cell shape to generate new blood vessels. IF are a large family of proteins that play an important structural and functional role in forming and regulating the cytoskeleton. Vimentin, a major type III intermediate filament protein is expressed in endothelial and other mesenchymal cells. The structure of vimentin is conserved in mammals and shows dynamic expression profiles in various cell types and different developmental stages. Although initial studies with vimentin-deficient mice demonstrated a virtually normal phenotype, subsequent studies have revealed several defects in cell attachment, migration, signaling, neurite extension, and vascularization. Regulation of vimentin is highly complex and is driven by posttranslational modifications such as phosphorylation and cleavage by intracellular proteases. This review discusses various novel functions which are now known to be mediated by vimentin, summarizing structure, regulation and roles of vimentin in cell adhesion, migration, angiogenesis, neurite extension, and cancer. We specifically highlight a pathway involving growth factor-mediated calpain activation, vimentin cleavage, and MT1-MMP membrane translocation that is required for endothelial cell invasion in 3D environments. This pathway may also regulate the analogous processes of neurite extension and tumor cell invasion.

Myopathic changes in murine skeletal muscle lacking synemin

Diseases of striated muscle linked to intermediate filament (IF) proteins are associated with defects in the organization of the contractile apparatus and its links to costameres, which connect the sarcomeres to the cell membrane. Here we study the role in skeletal muscle of synemin, a type IV IF protein, by examining mice null for synemin (synm-null). Synm-null mice have a mild skeletal muscle phenotype. Tibialis anterior (TA) muscles show a significant decrease in mean fiber diameter, a decrease in twitch and tetanic force, and an increase in susceptibility to injury caused by lengthening contractions. Organization of proteins associated with the contractile apparatus and costameres is not significantly altered in the synm-null. Elastimetry of the sarcolemma and associated contractile apparatus in extensor digitorum longus myofibers reveals a reduction in tension consistent with an increase in sarcolemmal deformability. Although fatigue after repeated isometric contractions is more marked in TA muscles of synm-null mice, the ability of the mice to run uphill on a treadmill is similar to controls. Our results suggest that synemin contributes to linkage between costameres and the contractile apparatus and that the absence of synemin results in decreased fiber size and increased sarcolemmal deformability and susceptibility to injury. Thus synemin plays a moderate but distinct role in fast twitch skeletal muscle.

A novel highly reactive Fab antibody for breast cancer tissue diagnostics and staging also discriminates a subset of good prognostic triple-negative breast cancers

The discovery of novel markers for breast cancer (BC) has been recently relied on antibody combinatorial libraries and selection through phage display. We constructed a recombinant Fab library, and after selections against BC tissues, the FabC4 clone was thoroughly investigated by immunohistochemistry in 232 patients with long-term follow-up. The FabC4 ligand was determined by mass spectrometry. The FabC4 expression was associated with younger age, lack of progesterone receptor, higher histological grades and non-luminal subtypes, and it also identified a subset of good prognostic triple-negative BCs, possibly targeting a conformational epitope of Cytokeratin-10 (CK10). This new CK10-epitope specific antibody may open new possibilities in diagnostic and therapeutic strategies.

Co-localization of serine/threonine kinase 33 (Stk33) and vimentin in the hypothalamus

We investigate the immunoreactivity of serine/threonine kinase 33 (Stk33) and of vimentin in the brain of mouse, rat and hamster. Using a Stk33-specific polyclonal antibody, we show by immunofluorescence staining that Stk33 is present in a variety of brain regions. We found a strong staining in the ependymal lining of all cerebral ventricles and the central canal of the spinal cord as well as in hypothalamic tanycytes. Stk33 immunoreactivity was also found in circumventricular organs such as the area postrema, subfornical organ and pituitary and pineal glands. Double-immunostaining experiments with antibodies against Stk33 and vimentin showed a striking colocalization of Stk33 and vimentin. As shown previously, Stk33 phosphorylates recombinant vimentin in vitro. Co-immunoprecipitation experiments and co-sedimentation assays indicate that Stk33 and vimentin are associated in vivo and that this association does not depend on further interacting partners (Brauksiepe et al. in BMC Biochem 9:25, 2008). This indicates that Stk33 is involved in the dynamics of vimentin polymerization/depolymerization. Since in tanycytes the vimentin expression is regulated by the photoperiod (Kameda et al. in Cell Tissue Res 314:251-262, 2003), we determine whether this also holds true for Stk33. We study hypothalamic sections from adult Djungarian hamsters (Phodopus sungorus) held under either long photoperiods (L:D 16:8 h) or short photoperiods (L:D 8:16 h) for 2 months. In addition, we examine whether age-dependent changes in Stk33 protein content exist. Our results show that Stk33 in tanycytes is regulated by the photoperiod as is the case for vimentin. Stk33 may participate in photoperiodic regulation of the endocrine system.

Parkin induces upregulation of 40S ribosomal protein SA and posttranslational modification of cytokeratins 8 and 18 in human cervical cancer cells

Parkin was originally identified as a protein associated with Parkinson's disease. Recently, numerous research studies have suggested that parkin acts as a tumor suppressor. In accordance with these studies, we previously reported that overexpression of parkin in HeLa cells induced growth inhibition. To elucidate possible mechanisms by which parkin may inhibit cell growth, HeLa cells were infected with adenoviruses expressing either the parkin gene or adenovirus alone for 72 h and a total proteomic analysis was performed using 2-D gel electrophoresis followed by LC-MS/MS. We identified three proteins whose expression changed between the two groups: the 40S ribosomal protein SA (RPSA) was downregulated in parkin virus-infected cells, and cytokeratins 8 and 18 exhibited an acid shift in pI value without a change in molecular weight, suggesting that these proteins became phosphorylated in parkin virus-infected cells. The changes in these three proteins were first observed at 60 h postinfection and were most dramatic at 72 h postinfection. Because upregulation of RPSA and dephosphorylation of cytokeratins 8/18 have been linked with tumor progression, these data suggest that parkin may inhibit cell growth, at least in part, by decreasing RPSA expression and inducing phosphorylation of cytokeratin 8/18.

Understanding the role of keratins 8 and 18 in neoplastic potential of breast cancer derived cell lines

Background

Breast cancer is a complex disease which cannot be defined merely by clinical parameters like lymph node involvement and histological grade, or by routinely used biomarkers like estrogen receptor (ER), progesterone receptor (PGR) and epidermal growth factor receptor 2 (HER2) in diagnosis and prognosis. Breast cancer originates from the epithelial cells. Keratins (K) are cytoplasmic intermediate filament proteins of epithelial cells and changes in the expression pattern of keratins have been seen during malignant transformation in the breast. Expression of the K8/18 pair is seen in the luminal cells of the breast epithelium, and its role in prognostication of breast cancer is not well understood.

Methodology/Principal Findings

In this study, we have modulated K8 expression to understand the role of the K8/18 pair in three different breast epithelium derived cell lines: non-transformed MCF10A, transformed but poorly invasive MDA MB 468 and highly invasive MDA MB 435. The up-regulation of K8 in the invasive MDA MB 435 cell line resulted in a significant decrease in proliferation, motility, in-vitro invasion, tumor volume and lung metastasis. The down-regulation of K8 in MDA MB 468 resulted in a significant increase in transformation potential, motility and invasion in-vitro, while MCF10A did not show any changes in cell transformation assays.

Conclusions/Significance

These results indicate the role of K8/18 in modulating invasion in breast cancer -its presence correlating with less invasive phenotype and absence correlating with highly invasive, dedifferentiated phenotype. These data may have important implications for prognostication of breast cancer.

Understanding the role of keratins 8 and 18 in neoplastic potential of breast cancer derived cell lines

BACKGROUND

Breast cancer is a complex disease which cannot be defined merely by clinical parameters like lymph node involvement and histological grade, or by routinely used biomarkers like estrogen receptor (ER), progesterone receptor (PGR) and epidermal growth factor receptor 2 (HER2) in diagnosis and prognosis. Breast cancer originates from the epithelial cells. Keratins (K) are cytoplasmic intermediate filament proteins of epithelial cells and changes in the expression pattern of keratins have been seen during malignant transformation in the breast. Expression of the K8/18 pair is seen in the luminal cells of the breast epithelium, and its role in prognostication of breast cancer is not well understood.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we have modulated K8 expression to understand the role of the K8/18 pair in three different breast epithelium derived cell lines: non-transformed MCF10A, transformed but poorly invasive MDA MB 468 and highly invasive MDA MB 435. The up-regulation of K8 in the invasive MDA MB 435 cell line resulted in a significant decrease in proliferation, motility, in-vitro invasion, tumor volume and lung metastasis. The down-regulation of K8 in MDA MB 468 resulted in a significant increase in transformation potential, motility and invasion in-vitro, while MCF10A did not show any changes in cell transformation assays.

CONCLUSIONS/SIGNIFICANCE

These results indicate the role of K8/18 in modulating invasion in breast cancer -its presence correlating with less invasive phenotype and absence correlating with highly invasive, dedifferentiated phenotype. These data may have important implications for prognostication of breast cancer.

Keratins in colorectal epithelial function and disease

Keratins are the largest subgroup of intermediate filament proteins, which are an important constituent of the cellular cytoskeleton. The principally expressed keratins (K) of the intestinal epithelium are K8, K18 and K19. The specific keratin profile of a particular epithelium provides it with strength and integrity. In the colon, keratins have been shown to regulate electrolyte transport, likely by targeting ion transporters to their correct location in the colonocytes. Keratins are highly dynamic and are subject to post-translational modifications including phosphorylation, acetylation and glycosylation. These affect the filament dynamics and hence solubility of keratins and may contribute to protection against degradation. Keratin null mice (K8(-/-) ) develop colitis, and abnormal keratin mutations have been shown to be associated with inflammatory bowel disease (IBD). Abnormal expression of K7 and K20 has been noted in colitis-associated dysplasia and cancers. In sporadic colorectal cancers (CRCs) may be useful in predicting tumour prognosis; a low K20 expression is noted in CRCs with high microsatellite instability; and keratins have been noted as dysregulated in peri-adenomatous fields. Caspase-cleaved fragment of K18 (M30) in the serum of patients with CRC has been used as a marker of cancer load and to assess response to therapy. These data suggest an emerging importance of keratins in maintaining normal function of the gastrointestinal epithelium as well as being a marker of various colorectal diseases. This review will primarily focus on the biology of these proteins, physiological functions and alterations in IBD and CRCs.

Keratin K18 increases cystic fibrosis transmembrane conductance regulator (CFTR) surface expression by binding to its C-terminal hydrophobic patch

BACKGROUND

CFTR function is tightly regulated by many interacting proteins.

RESULTS

Intermediate filament protein keratin 18 increases the cell surface expression of CFTR by interacting with the C-terminal hydrophobic patch of CFTR.

CONCLUSION

K18 controls the function of CFTR.

SIGNIFICANCE

These findings offer novel insights into the regulation of CFTR and suggest that K18 and its dimerization partner, K8, may be modifier genes in cystic fibrosis. Malfunction of the cystic fibrosis transmembrane conductance regulator (CFTR) leads to cystic fibrosis, but the regulation of CFTR is not fully understood. Here, we identified the intermediate filament protein keratin K18 (K18) as a CFTR-binding protein by various approaches. We mapped a highly conserved "hydrophobic patch" ((1413)FLVI(1416)) in the CFTR C-terminus, known to determine plasmalemmal CFTR stability, as the K18-binding site. On the other hand, the C-terminal tail of K18 was found to be a critical determinant for binding CFTR. Overexpression of K18 in cells robustly increased the surface expression of wild-type CFTR, whereas depletion of K18 through RNA interference specifically diminished it. K18 binding increased the surface expression of CFTR by accelerating its apical recycling rate without altering CFTR biosynthesis, maturation, or internalization. Importantly, CFTR surface expression was markedly reduced in duodenal and gallbladder epithelia of K18(-/-) mice. Taken together, our results suggest that K18 increases the cell surface expression of CFTR by interacting with the CFTR C-terminal hydrophobic patch. These findings offer novel insights into the regulation of CFTR and suggest that K18 and its dimerization partner, K8, may be modifier genes in cystic fibrosis.

Calpain-mediated vimentin cleavage occurs upstream of MT1-MMP membrane translocation to facilitate endothelial sprout initiation

Endothelial cells normally line the vasculature and remain quiescent. However, these cells can be rapidly stimulated to undergo morphogenesis and initiate new blood vessel formation given the proper cues. This study reports a new mechanism for initiating angiogenic sprout formation that involves vimentin, the major intermediate filament protein in endothelial cells. Initial studies confirmed vimentin was required for sphingosine 1-phosphate (S1P)- and growth factor (GF)-induced endothelial cell invasion, and vimentin was cleaved by calpains during invasion. Calpains were predominantly activated by GF and were required for sprout initiation. Because others have reported membrane type 1-matrix metalloproteinase (MT1-MMP) is required for endothelial sprouting responses, we tested whether vimentin and calpain acted upstream of MT1-MMP. Both calpain and vimentin were required for successful MT1-MMP membrane translocation, which was stimulated by S1P. In addition, vimentin complexed with MT1-MMP in a manner that required both the cytoplasmic domain of MT1-MMP and calpain activation, which increased the soluble pool of vimentin in endothelial cells. Altogether, these data indicate that pro-angiogenic signals converge to activate calpain-dependent vimentin cleavage and increase vimentin solubility, which act upstream to facilitate MT1-MMP membrane translocation, resulting in successful endothelial sprout formation in three-dimensional collagen matrices. These findings help explain why S1P and GF synergize to stimulate robust sprouting in 3D collagen matrices.

Protective effects of ginsenosides against Bisphenol A-induced cytotoxicity in 15P-1 Sertoli cells via extracellular signal-regulated kinase 1/2 signalling and antioxidant mechanisms

Numerous studies have demonstrated that Bisphenol A (BPA) can cause reproductive toxicity. Ginseng has wide range of pharmacological actions and, more importantly, has proven its worth with respect to reproductive function in several reports. We have suggested that ginsenosides, the main active components of ginseng, may protect against BPA-induced cell damage. Therefore, an in vitro culture model of 15P-1 Sertoli cells was employed to investigate whether ginsenosides have protective effects on BPA-stimulated 15P-1 Sertoli cells. The results revealed that ginsenosides (75 μg/ml) significantly inhibited BPA-induced decreases in cell viability and increases in apoptosis. Immunofluorescence staining showed that BPA exposure-induced collapse of vimentin intermediate filaments was prevented by the application of ginsenosides. Ginsenosides also inhibited extracellular signal-regulated kinase (ERK1/2) phosphorylation and BPA-induced alterations of Bcl-2 and Bax protein expression in 15P-1 Sertoli cells. Furthermore, the alterations of T-AOC, superoxide dismutase, glutathione peroxidase, glutathione reductase, glutathione and malondialdehyde levels in BPA-stimulated cells were partially prevented with pre-treatment with ginsenosides. Taken together, these results suggest that ginsenosides have protective effects against BPA-induced cell damage and that these effects are mediated by preventing ERK1/2 phosphorylation and through the enhancement of cellular antioxidant capacity. Ginsenosides may therefore be beneficial in the prevention of environmental BPA-induced, reproduction-related toxicity.

Cross-immunoreactivity between the LH1 antibody and cytokeratin epitopes in the differentiating epidermis of embryos of the grass snake Natrix natrix L. during the end stages of embryogenesis

The monoclonal anti-cytokeratin 1/10 (LH1) antibody recognizing K1/K10 keratin epitopes that characterizes a keratinized epidermis of mammals cross-reacts with the beta and Oberhäutchen layers covering the scales and gastrosteges of grass snake embryos during the final period of epidermis differentiation. The immunolocalization of the anti-cytokeratin 1/10 (LH1) antibody appears in the beta layer of the epidermis, covering the outer surface of the gastrosteges at the beginning of developmental stage XI, and in the beta layer of the epidermis, covering the outer surface of the scales at the end of developmental stage XI. This antibody cross-reacts with the Oberhäutchen layers in the epidermis covering the outer surface of both scales and gastrosteges at developmental stages XI and XII just before its fusion with the beta layers. After fusion of the Oberhäutchen and beta layers, LH1 immunolabeling is weaker than before. This might suggest that alpha-keratins in these layers of the epidermis are masked by beta-keratins, modified, or degraded. The anti-cytokeratin 1/10 (LH1) antibody stains the Oberhäutchen layer in the epidermis covering the inner surface of the gastrosteges and the hinge regions between gastrosteges at the end of developmental stage XI. However, the Oberhäutchen of the epidermis covering the inner surfaces of the scales and the hinge regions between scales does not show cytokeratin 1/10 (LH1) immunolabeling until hatching. This cross-reactivity suggests that the beta and Oberhäutchen layers probably contain some alpha-keratins that react with the LH1 antibody. It is possible that these alpha-keratins create specific scaffolding for the latest beta-keratin deposition. It is also possible that the LH1 antibody cross-reacts with other epidermal proteins such as filament-associated proteins, i.e., filaggrin-like. The anti-cytokeratin 1/10 (LH1) antibody does not stain the alpha and mesos layers until hatching. We suppose that the differentiation of these layers will begin just after the first postnatal sloughing.

Loss of desmin triggers mechanosensitivity and up-regulation of Ankrd1 expression through Akt-NF-κB signaling pathway in smooth muscle cells

Muscle cells, including human airway smooth muscle cells (HASMCs) express ankyrin repeat protein 1 (Ankrd1), a member of ankyrin repeat protein family. Ankrd1 efficiently interacts with the type III intermediate filament desmin. Our earlier study showed that desmin is an intracellular load-bearing protein that influences airway compliance, lung recoil, and airway contractile responsiveness. These results suggest that Ankrd1 and desmin may play important roles on ASMC homeostasis. Here we show that small interfering (si)RNA-mediated knockdown of the desmin gene in HASMCs, recombinant HASMCs (reHASMCs), up-regulates Ankrd1 expression. Moreover, loss of desmin in HASMCs increases the phosphorylation of Akt, inhibitor of κB kinase (IKK)-α, and inhibitor of κB (IκB)-α proteins, leading to NF-κB activation. Treatment of reHASMCs with Akt, IKKα, IκBα, or NF-κB inhibitor inhibits the loss of desmin-induced Ankrd1 up-regulation, suggesting Akt/NF-κB-mediated Ankrd1 regulation. Transfection of reHASMCs with siRNA specific for p50 or p65 corroborates the NF-κB-mediated Ankrd1 regulation. Luciferase reporter assays show that NF-κB directly binds on Ankrd1 promoter and up-regulates Ankrd1 levels. Overall, our data provide a new link between desmin and Ankrd1 regulation, which may be important for ASMC homeostasis.

Signaling mechanisms downstream of quinolinic acid targeting the cytoskeleton of rat striatal neurons and astrocytes

The studies of signaling mechanisms involved in the disruption of the cytoskeleton homeostasis were performed in a model of quinolinic acid (QUIN) neurotoxicity in vitro. This investigation focused on the phosphorylation level of intermediate filament (IF) subunits of astrocytes (glial fibrillary acidic protein - GFAP) and neurons (low, medium and high molecular weight neurofilament subunits - NFL, NFM and NFH, respectively). The activity of the phosphorylating system associated with the IFs was investigated in striatal slices of rat exposed to QUIN or treated simultaneously with QUIN plus glutamate receptor antagonists, calcium channel blockers or kinase inhibitors. Results showed that in astrocytes, the action of 100 μM QUIN was mainly due to increased Ca(2+) influx through NMDA and L-type voltage-dependent Ca(2+) channels (L-VDCC). In neuronal cells QUIN acted through metabotropic glutamate receptor (mGluR) activation and influx of Ca(2+) through NMDA receptors and L-VDCC, as well as Ca(2+) release from intracellular stores. These mechanisms then set off a cascade of events including activation of PKA, PKCaMII and PKC, which phosphorylate head domain sites on GFAP and NFL. Also, Cdk5 was activated downstream of mGluR5, phosphorylating the KSP repeats on NFM and NFH. mGluR1 was upstream of phospholipase C (PLC) which, in turn, produced diacylglycerol (DAG) and inositol 3,4,5 triphosphate (IP3). DAG is important to activate PKC and phosphorylate NFL, while IP(3) contributed to Ca(2+) release from internal stores promoting hyperphosphorylation of KSP repeats on the tail domain of NFM and NFH. The present study supports the concept of glutamate and Ca(2+) contribution in excitotoxic neuronal damage provoked by QUIN associated to dysfunction of the cytoskeleton homeostasis and highlights the differential signaling mechanisms elicited in striatal astrocytes and neurons.

Novel function of keratins 5 and 14 in proliferation and differentiation of stratified epithelial cells

Keratin expression in stratified epithelia is tightly regulated during squamous cell differentiation. Keratins 5 and 14 are expressed in mitotically active basal layer cells, but their function is not well defined. Reported here is the possible role of K14 in regulation of cell proliferation/differentiation in stratified epithelial cells.

Keratins are cytoplasmic intermediate filament proteins preferentially expressed by epithelial tissues in a site-specific and differentiation-dependent manner. The complex network of keratin filaments in stratified epithelia is tightly regulated during squamous cell differentiation. Keratin 14 (K14) is expressed in mitotically active basal layer cells, along with its partner keratin 5 (K5), and their expression is down-regulated as cells differentiate. Apart from the cytoprotective functions of K14, very little is known about K14 regulatory functions, since the K14 knockout mice show postnatal lethality. In this study, K14 expression was inhibited using RNA interference in cell lines derived from stratified epithelia to study the K14 functions in epithelial homeostasis. The K14 knockdown clones demonstrated substantial decreases in the levels of the K14 partner K5. These cells showed reduction in cell proliferation and delay in cell cycle progression, along with decreased phosphorylated Akt levels. K14 knockdown cells also exhibited enhanced levels of activated Notch1, involucrin, and K1. In addition, K14 knockdown AW13516 cells showed significant reduction in tumorigenicity. Our results suggest that K5 and K14 may have a role in maintenance of cell proliferation potential in the basal layer of stratified epithelia, modulating phosphatidylinositol 3-kinase/Akt–mediated cell proliferation and/or Notch1-dependent cell differentiation.

Loss of keratins 8 and 18 leads to alterations in α6β4-integrin-mediated signalling and decreased neoplastic progression in an oral-tumour-derived cell line

Keratins 8 and 18 (K8 and K18) are predominantly expressed in simple epithelial tissues and perform both mechanical and regulatory functions. Aberrant expression of K8 and K18 is associated with neoplastic progression and invasion in squamous cell carcinomas (SCCs). To understand the molecular basis by which K8 promotes neoplastic progression in oral SCC (OSCC), K8 expression was inhibited in AW13516 cells. The K8-knockdown clones showed a significant reduction in tumorigenic potential, which was accompanied by a reduction in cell motility, cell invasion, decreased fascin levels, alterations in the organization of the actin cytoskeleton and changes in cell shape. Furthermore, K8 knockdown led to a decrease in α6β4 integrin levels and α6β4-integrin-dependent signalling events, which have been reported to play an important role in neoplastic progression in epithelial tissues. Therefore, modulation of α6β4 integrin signalling might be one of the mechanisms by which K8 and K18 promote malignant transformation and/or progression in OSCCs.

Membrane-initiated actions of thyroid hormones on the male reproductive system

The presence of specific nuclear receptors to thyroid hormones, described in prepubertal Sertoli cells, implies the existence of an early and critical influence of these hormones on testis development. Although the mechanism of action thyroid hormones has been classically established as a genomic action regulating testis development, our research group has demonstrated that these hormones exert several effects in Sertoli cells lacking nuclear receptor activation. These findings led to the identification of non-classical thyroid hormone binding elements in the plasma membrane of testicular cells. Through binding to these sites, thyroid hormones could exert nongenomic effects, including those on ion fluxes at the plasma membrane, on signal transduction via kinase pathways, on amino acid accumulation, on modulation of extracellular nucleotide levels and on vimentin cytoskeleton. The evidence of the participation of different K(+), Ca(2+) and Cl(-) channels in the mechanism of action of thyroid hormones, characterizes the plasma membrane as an important microenvironment able to coordinate strategic signal transduction pathways in rat testis. The physiological responses of the Sertoli cells to hormones are dependent on continuous cross-talking of different signal transduction pathways. Apparently, the choice of the signaling pathways to be activated after the interaction of the hormone with cell surface binding sites is directly related to the physiological action to be accomplished. Yet, the enormous complexity of the nongenomic actions of thyroid hormones implies that different specific binding sites located on the plasma membrane or in the cytosol are believed to initiate specific cell responses.

Role of the cytoskeleton in formation and maintenance of angiogenic sprouts

Angiogenesis is the formation of new blood vessels from pre-existing structures, and is a key step in tissue and organ development, wound healing and pathological events. Changes in cell shape orchestrated by the cytoskeleton are integral to accomplishing the various steps of angiogenesis, and an intact cytoskeleton is also critical for maintaining newly formed structures. This review focuses on how the 3 main cytoskeletal elements--microfilaments, microtubules, and intermediate filaments--regulate the formation and maintenance of angiogenic sprouts. Multiple classes of compounds target microtubules and microfilaments, revealing much about the role of actin and tubulin and their associated molecules in angiogenic sprout formation and maintenance. In contrast, intermediate filaments are much less studied, yet intriguing evidence suggests a vital, but unresolved, role in angiogenic sprouting. This review discusses evidence for regulatory molecules and pharmacological compounds that affect actin, microtubule and intermediate filament dynamics to alter various steps of angiogenesis, including endothelial sprout formation and maintenance.