Mechanisms involved in methylmercuric chloride (MeHgCl)-induced suppression of human neutrophil apoptosis

We have previously demonstrated that concentrations of 1-10 μM of methylmercuric chloride (MeHgCl) that are cytotoxic to monocytes-macrophages can curiously inhibit neutrophil apoptosis by a yet unknown mechanism. In the present study, we demonstrate that, as with the cytokine granulocyte-macrophage colony-stimulating factor (GM-CSF), a classical inhibitor of neutrophil apoptosis, treatment of cells with 5 M MeHgCl inducesde novo protein synthesis and prevents the loss of expression of the antiapoptotic Mcl-1 protein. The expression of the cytoskeletal proteins gelsolin, paxillin and vinculin was similar in MeHgCl or GM-CSF-induced suppression of apoptosis. However, MeHgCl prevents the degradation of vimentin differently than GM-CSF. Apoptosis was further confirmed by flow cytometry (FITC annexin-V), and by monitoring CD16 cell surface expression. Curiously, unlike GM-CSF, MeHgCl did not prevent CD16 shedding. We conclude that, like GM-CSF, MeHgCl can delay neutrophil apoptosis by inducing de novoprotein synthesis and by preventing the loss of the antiapoptotic Mcl-1 protein. However, unlike GM-CSF, MeHgCl induces an atypical degradation of vimentin without preventing CD16 shedding.

siRNA induces gelsolin gene transcription activation in human esophageal cancer cell

Recent studies show that targeting gene promoter or 3' terminal regions of mRNA with siRNA induces target gene transcription. However, the ability of exon-targeting siRNA to affect transcription has yet to be demonstrated. We designed and synthesized siRNA against various exons in the gelsolin gene (GSN) to knockdown GSN transcript in KYSE150 and KYSE450 cells. Surprisingly, we found that siGSN-2, targeting the GSN twelfth exon, induced GSN gene transcription detected by real time RT-PCR. An siGSN-2 co-precipitation assay was performed and H3 histone, previously shown to correlate with gene transcription, was detected in the siGSN-2 pull-down pellet. However, H3 histone was not detected in an siGSN-1-precipitated pellet, which resulted in GSN knockdown. In addition, siGSN-2 decreased stress fibers, lamellipodia and filopodia, demonstrating that siGSN-2 induced GSN transcription activation and exerted biological function. In conclusion, our finds reveal siRNA, which is derived from target gene exon, can form the complex with H3 histone to be involved in the regulation of gene expression.

Diet-induced over-expression of flightless-I protein and its relation to flightlessness in Mediterranean fruit fly, Ceratitis capitata

The Mediterranean fruit fly (medfly), Ceratitis capitata is among the most economically important pests worldwide. Understanding nutritional requirement helps rearing healthy medfly for biocontrol of its population in fields. Flight ability is a high priority criterion. Two groups of medfly larvae were reared with two identical component diets except one with fatty acids (diet A) and another without it (diet B). Adults from larvae reared on diet B demonstrated 20±8% of normal flight ability, whereas those from larvae reared on diet A displayed full flight ability of 97±1%. Proteomes were profiled to compare two groups of medfly pupae using shotgun proteomics to study dietary effects on flight ability. When proteins detected in pupae A were compared with those in pupae B, 233 and 239 proteins were, respectively, under- and over-expressed in pupae B, while 167 proteins were overlapped in both pupae A and B. Differential protein profiles indicate that nutritional deficiency induced over-expression of flightless-I protein (fli-I) in medfly. All proteins were subjected to Ingenuity Pathway Analysis (IPA) to create 13 biological networks and 17 pathways of interacting protein clusters in human ortholog. Fli-I, leucine-rich repeat (LRR)-containing G protein-coupled receptor 2, LRR protein soc-2 and protein wings apart-like were over-expressed in pupae B. Inositol-1,4,5-trisphosphate receptor, protocadherin-like wing polarity protein stan and several Wnt pathway proteins were under-expressed in pupae B. These results suggest down-regulation of the Wnt/wingless signaling pathway, which consequently may result in flightlessness in pupae B. The fli-I gene is known to be located within the Smith-Magenis syndrome (SMS) region on chromosome 17, and thus, we speculate that nutritional deficiency might induce over-expression of fli-I (or fli-I gene) and be associated with human SMS. However, more evidence would be needed to confirm our speculation.

Distinctive profile of IsomiR expression and novel microRNAs in rat heart left ventricle

MicroRNAs (miRNAs) are single-stranded non-coding RNAs that negatively regulate target gene expression through mRNA cleavage or translational repression. There is mounting evidence that they play critical roles in heart disease. The expression of known miRNAs in the heart has been studied at length by microarray and quantitative PCR but it is becoming evident that microRNA isoforms (isomiRs) are potentially physiologically important. It is well known that left ventricular (patho)physiology is influenced by transmural heterogeneity of cardiomyocyte phenotype, and this likely reflects underlying heterogeneity of gene expression. Given the significant role of miRNAs in regulating gene expression, knowledge of how the miRNA profile varies across the ventricular wall will be crucial to better understand the mechanisms governing transmural physiological heterogeneity. To determinine miRNA/isomiR expression profiles in the rat heart we investigated tissue from different locations across the left ventricular wall using deep sequencing. We detected significant quantities of 145 known rat miRNAs and 68 potential novel orthologs of known miRNAs, in mature, mature* and isomiR formation. Many isomiRs were detected at a higher frequency than their canonical sequence in miRBase and have different predicted targets. The most common miR-133a isomiR was more effective at targeting a construct containing a sequence from the gelsolin gene than was canonical miR-133a, as determined by dual-fluorescence assay. We identified a novel rat miR-1 homolog from a second miR-1 gene; and a novel rat miRNA similar to miR-676. We also cloned and sequenced the rat miR-486 gene which is not in miRBase (v18). Signalling pathways predicted to be targeted by the most highly detected miRNAs include Ubiquitin-mediated Proteolysis, Mitogen-Activated Protein Kinase, Regulation of Actin Cytoskeleton, Wnt signalling, Calcium Signalling, Gap junctions and Arrhythmogenic Right Ventricular Cardiomyopathy. Most miRNAs are not expressed in a gradient across the ventricular wall, with exceptions including miR-10b, miR-21, miR-99b and miR-486.

Downregulation of gelsolin family proteins counteracts cancer cell invasion in vitro

Gelsolin and CapG are both actin binding proteins that modulate a variety of physiological processes by interacting differently with the actin cytoskeleton. Several studies suggest that overexpression of these proteins promotes invasion in vitro. In this study we explored the contribution of these proteins in human cancer cell invasion and motility. We show that down regulation of CapG or gelsolin in several types of cancer cells, including MDA-MB 231 and PC-3 cells, significantly reduces the invasive and motile properties of cells, as well as cell aggregation. These results point to a role for CapG and gelsolin as tumor activator.

Inhibition of histone deacetylation protects wild-type but not gelsolin-deficient neurons from oxygen/glucose deprivation

Histone acetylation and deacetylation participate in the epigenetic regulation of gene expression. In this paper, we demonstrate that pre-treatment with the histone deacetylation inhibitor trichostatin A (TSA) enhances histone acetylation in primary cortical neurons and protects against oxygen/glucose deprivation, a model for ischaemic cell death in vitro. The actin-binding protein gelsolin was identified as a mediator of neuroprotection by TSA. TSA enhanced histone acetylation of the gelsolin promoter region, and up-regulated gelsolin messenger RNA and protein expression in a dose- and time-dependent manner. Double-label confocal immunocytochemistry visualized the up-regulation of gelsolin and histone acetylation within the same neuron. Together with gelsolin up-regulation, TSA pre-treatment decreased levels of filamentous actin. The neuroprotective effect of TSA was completely abolished in neurons lacking gelsolin gene expression. In conclusion, we demonstrate that the enhancement of gelsolin gene expression correlates with neuroprotection induced by the inhibition of histone deacetylation.

Regulation of pancreatic beta-cell insulin secretion by actin cytoskeleton remodelling: role of gelsolin and cooperation with the MAPK signalling pathway

We have previously isolated two MIN6 beta-cell sublines, B1, highly responsive to glucose-stimulated insulin secretion, and C3, markedly refractory (Lilla, V., Webb, G., Rickenbach, K., Maturana, A., Steiner, D. F., Halban, P. A. and Irminger, J. C. (2003) Endocrinology 144, 1368-1379). We now demonstrate that C3 cells have substantially increased amounts of F-actin stress fibres whereas B1 cells have shorter cortical F-actin. Consistent with these data, B1 cells display glucose-dependent actin remodelling whereas, in C3 cells, F-actin is refractory to this secretagogue. Furthermore, F-actin depolymerisation with latrunculin B restores glucose-stimulated insulin secretion in C3 cells. In parallel, glucose-stimulated ERK1/2 activation is greater in B1 than in C3 cells, and is potentiated in both sublines following F-actin depolymerisation. Glucose-activated phosphoERK1/2 accumulates at actin filament tips adjacent to the plasma membrane, indicating that these are the main sites of action for this kinase during insulin secretion. In addition, B1 cell expression of the calcium-dependent F-actin severing protein gelsolin is >100-fold higher than that of C3 cells. Knock-down of gelsolin reduced glucose-stimulated insulin secretion, whereas gelsolin over-expression potentiated secretion from B1 cells. Gelsolin localised along depolymerised actin fibres after glucose stimulation. Taken together, these data demonstrate that F-actin reorganization prior to insulin secretion requires gelsolin and plays a role in the glucose-dependent MAPK signal transduction that regulates beta-cell insulin secretion.

siRNA gelsolin knockdown induces epithelial-mesenchymal transition with a cadherin switch in human mammary epithelial cells

Epithelial-mesenchymal transition (EMT) describes a process occurring during development and oncogenesis by which epithelial cells obtain fibroblast-like properties and show reduced cell adhesion and increased motility. In this report, we demonstrated typical EMT in human mammary epithelial MCF10A small interfering (si)RNA gelsolin-knockdown cells. EMT was characterized by fibroblastic morphology, loss of contact inhibition and focus formation in monolayer growth, enhanced motility and invasiveness in vitro, increased actin filaments, overexpression of RAC, activation of both extracellular signal-regulated kinase and AKT, inactivation of glycogen synthase kinase-3, conversion of cadherin from the E- to N-type and induction of the transcription factor Snail. These results suggested that gelsolin functions as a switch that controls E- and N-cadherin conversion via Snail, and demonstrated that its knockdown leads to EMT in human mammary epithelial cells and possibly to the development of human mammary tumors.

Immunohistochemical expression of endothelial markers CD31, CD34, von Willebrand factor, and Fli-1 in normal human tissues

Few systematic studies have been published comparing the expression and distribution of endothelial cell (EC) markers in different vascular beds in normal human tissues. We investigated by immunohistochemistry the expression of CD31, CD34, von Willebrand factor (vWF), and Fli-1 in EC of the major organs and large vessels. Tissue samples obtained from autopsies and biopsy specimens were routinely processed and stained immunohistochemically for CD31, CD34, and vWF. Biopsy material was also stained immunohistochemically for Fli-1, D2-40, and Lyve-1. The expression pattern of the markers was heterogeneous in some of the organs studied. In the kidney, fenestrated endothelium of the glomeruli strongly expressed CD31 and CD34 but was only focally positive or completely negative for vWF. Alveolar wall capillaries of the lung strongly stained for CD31 and CD34 but were usually negative for vWF. The staining intensity for vWF increased gradually with the vessel caliber in the lung. Sinusoids of the spleen and liver were diffusely positive for CD31. They were negative for CD34 in the spleen and only expressed CD34 in the periportal area in the liver. Fli-1 was expressed in all types of EC but also in lymphocytes. D2-40 stained lymphatic endothelium only. Lyve-1 immunostaining was too variable to be applied to routinely processed tissues. The expression of EC markers CD31, CD34, and vWF in the vascular tree is heterogeneous with a specific pattern for individual vessel types and different anatomic compartments of the same organ. D2-40 labels lymphatic EC only.

Prognostic significance of gelsolin expression level and variability in non-small cell lung cancer

BACKGROUND

Gelsolin is an actin-binding protein that mediates cellular motility and maintains the integrity of cytoskeletal structure. Diminished expression of gelsolin has been observed in human cancer cell lines and tumors. Studies of the prognostic effect of gelsolin expression (GE) in non-small cell lung cancer (NSCLC) are rare and results are inconsistent to date. The present study used immunohistochemistry to evaluate the prognostic effect of gelsolin expression in 155 patients with resectable NSCLC.

METHODS

Detection of gelsolin in tumor cells was performed by immunohistochemistry, and two approaches to classification were used to describe expression: expression level (negative, reduced or high) and expression uniformity (uniform or variable). Expression level was determined by a weighted index of intensity of staining (i.e., overall tendency) in the specimen. Expression uniformity was based on the presence or absence of variability in immunostaining within the tumor section. Chi-square test, student t-test, Cox proportional hazards regression and Kaplan-Meier survival analysis were used in data analyses.

RESULTS

After controlling for covariates, high level gelsolin expression was significantly associated with poor survival compared with negative gelsolin expression in NSCLC, and this adverse prognostic effect was specific to patients with stage II tumors and for patients with squamous cell carcinomas. Similarly, variable gelsolin expression was significantly associated with poor survival compared with uniform gelsolin expression and this adverse prognostic effect was also specific to patients with stage II tumors and for patients with squamous cell carcinomas.

CONCLUSION

High level gelsolin expression and variable gelsolin expression are adverse prognostic factors for NSCLC in this study, which might manifest the high motility and heterogeneity of tumor cells, two distinguishing characteristics for tumors with potentially enhanced invasive and dissemination capabilities.

Gelsolin gene silencing involving unusual hypersensitivities to dimethylsulfate and KMnO4 in vivo footprinting on its promoter region

We previously reported that gelsolin gene expression is reduced in various tumors. In an effort to gain further insights into the mechanism of gelsolin downregulation in tumors, we examined the in vivo properties of the gelsolin promoter in urinary bladder cancer cell lines. Neither mutation nor hypermethylation was responsible for gene silencing at the promoter. After exposure to trichostatin A (TSA), a histone deacetylase inhibitor, gelsolin promoter activity was markedly enhanced in the cancer cells, not in cells derived from normal tissue. Chromatin immunoprecipitation assays revealed that both histones H3 and H4 were hypoacetylated in the promoter region of the cancer cells, and the accumulation of acetylated histones was detected by TSA treatment. In vivo footprinting analysis revealed the presence of dimethylsulfate (DMS) hypersensitive site in the untranslated region around nucleotide--35 only in the cancer cells but not in cells derived from normal tissue, and analysis of KMnO4 reactive nucleotides showed that the stem loop structure could be formed in vivo of the cancer cells. This novel stem loop structure may play a part in regulating the transcription of the gelsolin gene in the cancer cells. These results suggest that nucleosome accessibility through histone deacetylation and structural changes (DMS hypersensitivity and stem loop structure) in the promoter region form the basis of the mechanism leading to the silencing of gelsolin gene in human bladder cancer.

Cytoskeletal proteins in uterine epithelial cells only partially return to the pre-receptive state after the period of receptivity

Immunohistochemical staining of 5 cytoskeletal proteins (actin, alpha-actinin, gelsolin, plectin and plakoglobin) was used to investigate changes in distribution patterns of these proteins after the period of uterine receptivity for blastocyst implantation in the rat. Actin was found throughout the cytoplasm but it was concentrated along the apical plasma membrane on day 1 of pregnancy, decreased by day 6 and then increased again at day 9. Alpha-actinin and gelsolin were localized in distinctive bands along the apical plasma membrane at day 6 of pregnancy but became diffusely distributed at day 9. Plectin was localized along the apical and basal plasma membranes at day 6 but in higher amounts apically and at day 9, it was concentrated in apical and basal zones in the cells. Plakoglobin was found along the lateral and basal membranes with increased intensity along the apical third of the lateral plasma membrane from day 6 to day 9 of pregnancy. These results show that all 5 cytoskeletal proteins redistributed after the period of uterine receptivity: some exhibited a similar pattern of labelling to that found during the prereceptive state, whereas others only partially returned to the pre-receptive state. This change in distribution patterns may reflect differences in the epithelial barrier function before and after the period of receptivity.

Identification of a novel gelsolin truncate in the vertical and metastatic phase malignant melanomas

Examination of 38 human melanoma samples by Western blotting analysis with anti-gelsolin antibodies showed that a new 85 kDa truncated gelsolin (GSNp85), co-expressed with wild-type gelsolin, was frequently expressed in vertical growth phase melanomas (Clark level II-IV) and metastatic growth phase melanomas. The GSNp85 truncate was not expressed in radial growth phase melanomas (Clark level I), acquired naevi, other skin cancers or normal skin tissues. Peptide-sequencing analysis revealed that GSNp85 lacks the C-terminal domain of wild-type gelsolin at the region containing the caspase-8 recognition site IETD. Caspase-8 processing was detected in GSNp85-positive but not GSNp85-negative melanomas. These data suggest that GSNp85 is a cleavage product of caspase-8 and may be useful as a new marker for the vertical or metastatic growth phase of malignant melanoma.

Effects of FK228, a novel histone deacetylase inhibitor, on human lymphoma U-937 cells in vitro and in vivo

FK228 [(E)-(1S,4S,10S,21R)-7-[(Z)-ethylidene]-4,21-diisopropyl-2-oxa-12,13-dithia-5,8,20,23-tetraazabicyclo-[8,7,6]-tricos-16-ene-3,6,9,19,22-pentanone; FR901228, depsipeptide] is a novel histone deacetylase inhibitor that shows therapeutic efficacy in Phase I trials of patients with malignant lymphoma. However, its mechanism of action has not been characterized. In this study, we examined the in vitro and in vivo effects of FK228 on human lymphoma U-937 cells. FK228 very strongly inhibited the growth of U-937 cells with an IC(50) value of 5.92 nM. In a scid mouse lymphoma model, mice treated with FK228 once or twice a week survived longer than control mice, with median survival times of 30.5 (0.56 mg/kg) and 33 days (0.32 mg/kg), respectively (vs. 20 days in control mice). Remarkably, 2 out of 12 mice treated with FK228 (0.56 mg/kg once or twice a week) survived past the observation period of 60 days. The apoptotic population of U-937 cells time-dependently increased to 37.7% after 48 hr of treatment with FK228. In addition, FK228 induced G1 and G2/M arrest and the differentiation of U-937 cells to the CD11b(+)/CD14(+) phenotype. Expression of p21(WAF1/Cip1) and gelsolin mRNA increased up to 654- and 152-fold, respectively, after 24hr of treatment with FK228. FK228 caused histone acetylation in p21(WAF1/Cip1) promoter regions, including the Sp1-binding sites. In conclusion, (i) FK228 prolonged the survival time of scid mice in a lymphoma model, and (ii) the beneficial effects of FK228 on human lymphoma may be exerted through the induction of apoptosis, cell cycle arrest, and differentiation via the modulation of gene expression by histone acetylation.

Weak platelet agonists and U46619 induce apoptosis-like events in platelets, in the absence of phosphatidylserine exposure

Platelets express apoptotic markers during storage, while aging and after stimulation with strong agonists thrombin and collagen. It is unknown if the weak agonists ADP and epinephrine or U46619, a thromboxane analog, induce the expression of apoptotic markers in platelets. To answer this question, we measured phosphatidylserine exposure, gelsolin cleavage and decrease in membrane mitochondrial potential after stimulation with these agonists. No phosphatidylserine exposure was evident, however, gelsolin cleavage and a platelet population with a decreased membrane mitochondrial potential appeared, suggesting that in platelets selective agonists can induce apoptosis in the absence of phosphatidylserine exposure. Interestingly, costimulation by thrombin plus collagen together with each of the other agonists increased the phosphatidylserine exposure induced by strong agonists. These findings may be of importance in platelet activation and apoptosis under pathophysiological conditions where multiple effectors are involved.

Differential proteome analysis of replicative senescence in rat embryo fibroblasts

Normal somatic cells undergo a finite number of divisions and then cease dividing whereas cancer cells are able to proliferate indefinitely. To identify the underlying mechanisms that limit the mitotic potential, a two-dimensional differential proteome analysis of replicative senescence in serially passaged rat embryo fibroblasts was undertaken. Triplicate independent two-dimensional gels containing over 1200 spots each were run, curated, and analyzed. This revealed 49 spots whose expression was altered more than 2-fold. Of these, 42 spots yielded positive protein identification by mass spectrometry comprising a variety of cytoskeletal, heat shock, and metabolic proteins, as well as proteins involved in trafficking, differentiation, and protein synthesis, turnover, and modification. These included gelsolin, a candidate tumor suppressor for breast cancer, and alpha-glucosidase II, a member of the family of glucosidases that includes klotho; a defect in klotho expression in mice results in a syndrome that resembles human aging. Changes in expression of TUC-1, -2, -4, and -4 beta, members of the TUC family critical for neuronal differentiation, were also identified. Some of the identified changes were also shown to occur in two other models of senescence, premature senescence of REF52 cells and replicative senescence of mouse embryo fibroblasts. The majority of these candidate proteins were unrecognized previously in replicative senescence. They are now implicated in a new role.

Changes in gelsolin expression during ascidian metamorphosis

Gelsolin is an actin regulatory protein that is expressed in a wide variety of tissues and is especially abundant in muscle and blood cells. The role of gelsolin during structural reorganization of the body, such as during metamorphosis or regeneration, is poorly understood. We analyzed changes in gelsolin expression during ascidian embryogenesis and metamorphosis using nucleic acid probes and a monoclonal antibody (AS23) specific for ascidian gelsolin; our results indicated that gelsolin is maternally provided and that its de novo gene transcription is initiated during the neurula stage. In the larva, gelsolin was detectable in specific types of nerve cells, i.e. the adhesive papillae, motor neurons and epidermal sensory neurons. During metamorphosis, the expression of gelsolin changes markedly: the expression is suppressed in nerve tissues after tail resorption but is induced in mesodermal tissues. Gelsolin accumulated in mesenchyme cells until the onset of tail resorption, and following tail resorption, these cells migrated to the tunic and differentiated into tunic cells with many fine processes. Migration of the mesenchyme cells into the tunic was completely inhibited by treatment with cytochalasin B. Gelsolin was colocalized with actin in tunic cells, suggesting that it is involved in the rearrangement of actin filaments during cell locomotion or morphogenesis.

Downregulation of gelsolin correlates with the progression to breast carcinoma

The actin cytoskeleton underlies several normal cellular functions and is deranged during carcinogenesis. Gelsolin, a multifunctional actin-binding protein, is downregulated in several types of tumors and its abnormal expression is one of the most common defects noted in invasive breast carcinoma (ICA). This study utilizes immunohistochemistry to examine the expression of gelsolin in 95 ICA, 59 ductal carcinoma in situ (DCIS) and 36 benign lesions, including 17 atypical ductal hyperplasia (ADH). Cytoplasmic staining was scored as positive, reduced or negative. Gelsolin expression was then correlated with patient's age, tumor size, histologic grade and lymph node status. All unremarkable breast biopsies, 88% of ADH, 44% of DCIS and 28% of ICA were positive for gelsolin. This represents a significant difference among the groups (p = < 0.0001) and the trend towards reduced gelsolin with the progression to ICA is significantly linear (p = < 0.0001). For invasive carcinoma, patients older than 44 years were significantly more likely to have decreased expression of gelsolin than patients 44 years old and younger (p = 0.007). Bivariate analysis showed no correlation of gelsolin expression with lymph node status (p = 0.62), tumor size (p = 0.10), histologic grade (p = 0.42), estrogen receptor status (p = 1.0) or other clinicopathologic parameters. In clinical follow-up, there were 18 breast tumor related deaths within a median follow-up time of 4.2 years. Survival analysis indicated that the level of gelsolin expression may be associated with survival (p = 0.06). In summary, the frequency of gelsolin deficiency increases significantly with progression from ADH to DCIS to ICA. Additionally, gelsolin expression may be an independent marker of prognosis.

Apicidin, a histone deacetylase inhibitor, inhibits proliferation of tumor cells via induction of p21WAF1/Cip1 and gelsolin

Apicidin [cyclo(N-O-methyl-L-tryptophanyl-L-isoleucinyl-D-pipecolinyl -L-2-amino-8-oxodecanoyl)] is a fungal metabolite shown to exhibit antiparasitic activity by the inhibition of histone deacetylase (HDAC). In this study, we evaluated apicidin as a potential antiproliferative agent. Apicidin showed a broad spectrum of antiproliferative activity against various cancer cell lines, although with differential sensitivity. The antiproliferative activity of apicidin on HeLa cells was accompanied by morphological changes, cell cycle arrest at G1 phase, and accumulation of hyperacetylated histone H4 in vivo as well as inhibition of partially purified HDAC in vitro. In addition, apicidin induced selective changes in the expression of p21WAF1/Cip1 and gelsolin, which control the cell cycle and cell morphology, respectively. Consistent with increased induction of p21WAF1/Cip1, phosphorylation of Rb protein was markedly decreased, indicating the inhibition of cyclin-dependent kinases, which became bound to p21WAF1/Cip1. The effects of apicidin on cell morphology, expression of gelsolin, and HDAC1 activity in vivo and in vitro appeared to be irreversible, because withdrawal of apicidin did not reverse those effects, whereas the induction of p21WAF1/Cip1 by apicidin was reversible. Taken together, the results suggest that induction of histone hyperacetylation by apicidin is responsible for the antiproliferative activity through selective induction of genes that play important roles in the cell cycle and cell morphology.

Downregulated gelsolin expression in hyperplastic and neoplastic lesions of the prostate

BACKGROUND

Because of its role in cell motility and growth regulation, gelsolin, an actin-binding protein, has been considered a tumor suppressor and a potential prognostic marker in some neoplasias, such as breast and bladder cancer. Little is known about its immunoexpression in prostatic adenocarcinoma (PCA).

METHODS

Formalin-fixed, paraffin-embedded tissues of 72 prostatectomy specimens with adenocarcinoma and 8 nonneoplastic prostates from autopsies were stained with a gelsolin monoclonal antibody using the Avidin-biotin-peroxidase complex (ABC) method after microwave antigen retrieval. Immunoreactivity was evaluated in PCA, prostatic intraepithelial neoplasia (PIN), benign prostatic hyperplasia (BPH), and nonproliferative glandular tissue and stroma. The results were statistically analyzed.

RESULTS

Consistent gelsolin immunoreactivity was seen in prostatic stromal cells, smooth muscle, endothelia, and nerves. Variable gelsolin expression was seen in 20-100% (average (A) = 65.5%) of glandular cells in nonproliferative tissue (N = 75); 0-50% (A = 9.7%) in BPH (N = 59); 0-80% (A = 8.9%) in PIN (N = 61); and 0-90% (A = 9.3%) in PCA (N = 71). The level of gelsolin expression in nonproliferative prostatic tissue was similar between prostates with PCA (A = 63.4%) and nonneoplastic prostates (A = 67.5%). The level of gelsolin expression did not correlate with age, tumor size, Gleason score, or stage.

CONCLUSIONS

Gelsolin is decreased in PCA, PIN, and BPH in comparison to nonproliferative tissue. The role of this downregulation in the development of PCA is not clear. The similar reduction seen in PIN and BPH suggests that this event takes place indiscriminately in hyperplasia and early tumorigenesis in the prostate, which might limit its prognostic significance in PCA.

Epigenetic regulation of gelsolin expression in human breast cancer cells

Gelsolin is a multifunctional, actin-binding protein that is greatly decreased in many transformed cell lines and tumor tissues, including breast cancers. Downregulation of gelsolin RNA occurs in most breast cancers of rats, mice, and humans, but gross mutations of the gelsolin gene have not been found. Here we demonstrate by PCR and RT-PCR analysis that there are no point mutations in putative regulatory regions or the entire coding region of the cytoplasmic isoform of the gelsolin gene in human breast cancer cells (BCC). To determine if epigenetic modification is involved in downregulating gelsolin expression in MDA-MB-231 (MDA231), MCF7, and T47D BCC, we have used Southern blot analysis, 5-azacytidine (5aza) treatment, and trichostatin A (TSA) treatment. Southern blot analysis performed on genomic DNA demonstrated altered CpG methylation within intron 1 in DNA from all BCC compared to normal, mortal human mammary epithelial cells (HMEC). Treatment of the BCC with 5aza converted the DNA restriction pattern to that seen in untreated HMEC genomic DNA and caused modest increases in gelsolin RNA and protein. Incubation with TSA, an inhibitor of histone deacetylase, induced a dramatic upregulation of gelsolin RNA and protein levels which preceded apoptotic death of all BCC within 48-60 h. Our data support a role for epigenetic changes in chromatin structure leading to downregulation of gelsolin expression in human breast cancer. To our knowledge, this is the first example of a tumor suppressor gene downregulated in human breast cancer by changes in histone acetylation.

Coordinate induction of the actin cytoskeletal regulatory proteins gelsolin, vasodilator-stimulated phosphoprotein, and profilin during capillary morphogenesis in vitro

The formation of capillaries during development and tissue repair is likely to involve active reorganization of the actin cytoskeleton, although few studies have addressed this issue. Here, we have utilized an in vitro model of capillary morphogenesis whereby human umbilical vein endothelial cells are suspended within three-dimensional type I collagen gels. The cells undergo dramatic morphogenic changes to develop capillary lumens, tubes, and networks over 72 h of culture. Western blots using cell extracts of these gels over this time frame were performed using antibodies directed to various proteins associated with the actin cytoskeleton. Three proteins showed altered expression during the time course, and they were gelsolin, which increased fivefold; vasodilator-stimulated phosphoprotein (VASP), which increased twofold; and profilin, which increased threefold in expression between the 24- and the 72-h time points. Reverse transcriptase-polymerase chain reaction and Northern blot analysis revealed a similar increase in mRNA expression of the three proteins. After the onset of network formation, the differentiated endothelial cells (dECs) undergoing capillary morphogenesis were removed from collagen gels at 48 h of culture to compare their properties with untreated endothelial cells (uECs). These dECs showed two- to threefold increased spontaneous migration in Boyden chamber assays compared to uECs. The dECs also displayed a prominent spindle-shaped morphology and the novel presence of intranuclear gelsolin compared to uECs when both cell types were replated on type I collagen-coated microwells and glass coverslips. These data suggest that increased gelsolin, VASP, and profilin expression may play an important role in the regulation of capillary tube and network formation in three-dimensional extracellular matrix.

Down-regulation of gelsolin expression in human breast ductal carcinoma in situ with and without invasion

Expression of gelsolin, an actin filament regulatory protein, in human breast ductal carcinoma in situ (DCIS) was analyzed by immunohistochemistry using a monoclonal antibody. Formalin-fixed paraffin-embedded tissues from 59 pure DCIS specimens and 33 DCIS specimens with associated invasive components were evaluated for gelsolin reactivity and compared to eight normal breast cases and 76 invasive breast cancers. The proportion of cases exhibiting negative/low expression of gelsolin in the epithelium was as follows -- normal, 0%; pure DCIS, 56%; DCIS associated with invasion, 58% in the DCIS component and 66% in the invasive component; invasive carcinoma, 70%. These data demonstrate that down-regulation of gelsolin expression in breast epithelium frequently parallels progression to malignancy. Testing gelsolin expression (normal vs. negative/low levels) in the DCIS lesions for associations with patient age or any of the following histopathologic parameters revealed no significant (95% probability level) correlations -- tumor size; pathologic (Van Nuys system) grade; nuclear grade; necrosis; presence of histologic calcifications; presence or type of adjacent benign lesions; architectural histologic pattern; and mammographic extent. Gelsolin loss was more commonly associated with mammographic soft tissue lesions as compared to calcified lesions (P = 0.009). A positive trend of borderline significance (P = 0.06) found in the DCIS with invasion group was a correlation between down-regulated gelsolin expression in the DCIS component and size (< versus > or = 15 mm) of the invasive tumor. In conclusion, reduced gelsolin protein is detectable in at least half of breast lesions which have progressed to DCIS. The trend between increasing gelsolin loss and malignant progression from normal epithelium to DCIS to invasive breast cancer (P < 0.0001) suggests additional investigation is needed to determine the potential of altered gelsolin expression as a marker for prognosis and for therapeutic interventions in breast cancer.

The actin-binding proteins adseverin and gelsolin are both highly expressed but differentially localized in kidney and intestine

To understand the distinct functions of the closely related actin-severing proteins adseverin and gelsolin, we examined the expression of these proteins in detail during mouse and human development using a new highly sensitive and specific set of antibody reagents. Immunoblot analysis demonstrated that adseverin was highly expressed in mouse kidney and intestine at all stages of development and in human fetal and adult kidney. In contrast and as reported previously, gelsolin was expressed much more widely in both murine and human tissues. Immunohistochemistry on murine kidney sections revealed a predominantly differential localization of adseverin and gelsolin. Adseverin was expressed in peripolar cells, thin limbs, thick ascending limbs, and principal cells of cortical and medullary collecting ducts where it was diffusely localized in the cytoplasm. Gelsolin was expressed in the distal convoluted tubule, intercalated cells and principal cells of cortical and medullary collecting ducts, and in ureter. In the distal convoluted tubule, gelsolin showed a diffuse distribution and in principal cells of collecting ducts a localization at the basolateral pole. In intercalated cells, gelsolin localization was heterogeneous, either at the apical pole or diffusely in the cytoplasm. In human fetal and adult kidney, adseverin was expressed only in collecting ducts whereas gelsolin was expressed in thick ascending limbs and collecting ducts. In mouse and human intestine adseverin was expressed in enterocytes with a gradient of increasing expression from the duodenum to the colon, and from the crypt to the villus. The observations indicate high level expression of adseverin in specific cells of the kidney and colon, and suggest a previously unrecognized function of adseverin in epithelial cell function.

Trypanosoma cruzi: effect of protein kinase inhibitors and cytoskeletal protein organization and expression on host cell invasion by amastigotes and metacyclic trypomastigotes

Although trypomastigotes are regarded as the classic infective forms of T. cruzi, amastigotes generated extracellularly or released from infected cells during lysis may circulate and infect other cells. We have compared the infectivity of metacyclic trypomastigotes and extracellular amastigotes toward HeLa and Vero cells and observed that amastigotes were capable of invading both HeLa and Vero cells to a much higher degree than the corresponding metacyclic forms. Second, cell microfilament or microtubule disruption inhibited amastigote but not trypomastigote entry. Third, cells with altered expression in cytoskeletal components (ABP or gelsolin) internalize amastigotes and trypomastigotes with highly contrasting fashion. Fourth, protein kinase inhibitors such as genistein and staurosporine affect the internalization of amastigotes and trypomastigotes in a host-cell-dependent manner. Our results suggest that extracellular amastigotes and metacyclic trypomastigotes utilize mechanisms to invade host cells with particular features for each T. cruzi form and for each host cell. When internalized, both forms associate to lysosomes of HeLa cells.

Equus caballus gelsolin--cDNA sequence and protein structural implications

We have generated and characterized the cDNA from equine smooth muscle that encodes gelsolin, an actin-modulating protein. Overlapping cDNA clones synthesized by the reverse transcriptase/polymerase chain reaction and clones isolated from a horse genomic library provided the complete primary structure for the intracellular isoform of gelsolin, while cDNA complemented with protein sequence data produced the full-length primary transcript of the gelsolin isoform found circulating in equine plasma. The deduced amino acid sequences of the intracellular and secreted versions of equine gelsolin infer polypeptides of 731 and 755 residues with apparent molecular masses of 80.7 kDa and 83.2 kDa, respectively. Multiple sequence alignment analysis of equine, human, porcine, and murine orthologs of gelsolin demonstrates prominent similarities among all of these proteins, with the horse and human molecules exhibiting the largest degree of likeness with respect to polypeptide length and overall sequence composition. Both horse and human plasma gelsolins are comprised of 755 amino acids with 94% of the residues identical, while the degree of sequence identity in the shorter (731 residues) cytoplasmic gelsolins is 95%. Analysis of the sequences and structures of the six related domains that comprise gelsolin emphasizes the strong correlation that exists between primary structural conservation among mammalian gelsolins and maintenance of the three-dimensional domain fold characteristic of members of this protein family.

Suppression of morphological transformation by radicicol is accompanied by enhanced gelsolin expression

Radicicol, an inhibitor of Src-family protein-tyrosine kinases, causes morphological reversion of v-src- and v-Ha-ras-transformed fibroblasts and arrest of the cell cycle at both the G1 and the G2 phases. Radicicol was found to inhibit the growth of several other oncogene-transformed cell lines and human carcinoma cell lines and to revert their cell morphology to be flat. In the radicicol-treated flat cells, actin stress fiber bundles were reorganized. Since this effect of radicicol on these cell lines was inhibited by cycloheximide, de novo protein synthesis is required for the morphological reversion. Screening of cellular proteins enhanced in response to radicicol by two-dimensional gel electrophoresis suggested that the amount of gelsolin, an actin regulatory protein, was distinctly increased upon radicicol treatment. Western blot and Northern blot analyses showed that radicicol enhanced transcription of the gelsolin gene in human carcinoma cell lines, as a result of which the amount of gelsolin was increased several folds. Injection with an anti-gelsolin antibody into cells and successive treatment with radicicol resulted in approximately 80% reduction of the number of flat cells with stress fibers in comparison with controls treated with an irrelevant antibody. These results show that elevated expression of gelsolin is associated, at least in part, with the suppression of transformation and the restoration of actin stress fibers in human carcinoma cells by radicicol.

A novel gelsolin isoform expressed by oligodendrocytes in the central nervous system

Two isoforms of the Ca2+-sensitive, actin-binding protein gelsolin have been identified thus far; one is an intracellular protein, cytoplasmic gelsolin, and the other is a secretory protein called plasma gelsolin. Gelsolin expression in the mammalian CNS appears to be localized mainly to oligodendrocytes where it is presumed that the cytoplasmic isoform predominates. Here, we show that oligodendrocytes not only contain cytoplasmic gelsolin, but they also express a novel gelsolin isoform that we have named gelsolin-3. Cytoplasmic gelsolin, plasma gelsolin, and gelsolin-3 arise by alternative splicing from the same gene. The N-terminal amino acid sequence unique to gelsolin-3 is shown to be encoded by a single exon in a region previously thought to be an intron in the human gelsolin gene. In situ hybridization analysis confirmed that gelsolin-3 mRNA is localized primarily to oligodendrocytes in rat brain. In other tissues, gelsolin-3 shows a more restricted pattern of expression than cytoplasmic gelsolin. These data support the view that the gelsolin isoforms have differential roles in the regulation of the actin cytoskeleton.

Gelsolin modulates phospholipase C activity in vivo through phospholipid binding

Gelsolin and CapG are actin regulatory proteins that remodel the cytoskeleton in response to phosphatidylinositol 4,5-bisphosphate (PIP2) and Ca2+ during agonist stimulation. A physiologically relevant rise in Ca2+ increases their affinity for PIP2 and can promote significant interactions with PIP2 in activated cells. This may impact divergent PIP2- dependent signaling processes at the level of substrate availability. We found that CapG overexpression enhances PDGF-stimulated phospholipase Cgamma (PLCgamma) activity (Sun, H.-q., K. Kwiatkowska, D.C. Wooten, and H.L. Yin. 1995. J. Cell Biol. 129:147-156). In this paper, we examined the ability of gelsolin and CapG to compete with another PLC for PIP2 in live cells, in semiintact cells, and in vitro. We found that CapG and gelsolin overexpression profoundly inhibited bradykinin-stimulated PLCbeta. Inhibition occurred at or after the G protein activation step because overexpression also reduced the response to direct G protein activation with NaF. Bradykinin responsiveness was restored after cytosolic proteins, including gelsolin, leaked out of the overexpressing cells. Conversely, exogenous gelsolin added to permeabilized cells inhibited response in a dose-dependent manner. The washout and addback experiments clearly establish that excess gelsolin is the primary cause of PLC inhibition in cells. In vitro experiments showed that gelsolin and CapG stimulated as well as inhibited PLCbeta, and only gelsolin domains containing PIP2-binding sites were effective. Inhibition was mitigated by increasing PIP2 concentration in a manner consistent with competition between gelsolin and PLCbeta for PIP2. Gelsolin and CapG also had biphasic effects on tyrosine kinase- phosphorylated PLCgamma, although they inhibited PLCgamma less than PLCbeta. Our findings indicate that as PIP2 level and availability change during signaling, cross talk between PIP2-regulated proteins provides a selective mechanism for positive as well as negative regulation of the signal transduction cascade.

Temporal association between serum gelsolin levels and clinical events in a patient with severe falciparum malaria

Actin is present in high concentrations in most eukaryotic cells and can polymerize into filaments under physiological buffer conditions. As a result of tissue injury and cell lysis, large quantities of actin are released locally and may obstruct the downstream microvasculature, causing further damage to already injured organs. It has been postulated that this mechanism contributes to the development of the adult respiratory distress syndrome and to the diverse complications of falciparum malaria. Actin scavenging proteins--e.g., gelsolin--counteract the effects of extracellular actin, but the capacity of these plasma proteins can be overwhelmed by massive tissue injury. We examined the temporal relationship between serum levels of gelsolin (and tumor necrosis factor-alpha) and the clinical findings for a patient with severe falciparum malaria. The level of gelsolin decreased and then increased as the patient's status first worsened and then improved. We could not determine whether gelsolin served a biologically important function in this patient's recovery or was simply an epiphenomenon of disease activity. Gelsolin levels may be an early prognostic indicator in patients with a systemic inflammatory response syndrome. Moreover, the potential therapeutic role of recombinant human plasma gelsolin in patients with delayed organ dysfunction that commonly follows a self-limited initial insult merits investigation.

Nitric oxide-mediated cGMP synthesis in oligodendrocytes in the developing rat brain

We investigated the nature of cGMP-synthesizing cells in the developing rat forebrain using cGMP-immunocytochemistry in combination with in vitro incubation of brain slices. When brain slices of immature rats, aged between 1 and 4 weeks, were incubated with sodium nitroprusside (SNP), a nitric oxide (NO) donor compound, in the presence of the phosphodiesterase inhibitor isobutylmethylxanthine (IBMX), small round cells with a few processes in and around the corpus callosum were visualized with the cGMP-antibody. The morphology and the distribution of the cGMP-positive cells were consistent with the criteria for oligodendrocytes. Furthermore, the cGMP-positive cells expressed 2'3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) and gelsolin, which are marker proteins for oligodendrocytes. Therefore, we concluded that the cGMP-positive cells were oligodendrocytes. A subpopulation of the oligodendrocyte was found to be cGMP-immunoreactive also when slices were incubated in the absence of SNP. Furthermore, incubation of the slice in the presence of L-NAME, an inhibitor of NO synthase, but in the absence of SNP abolished cGMP immunostaining. In addition, some populations of neurons and astrocytes in restricted brain areas produced cGMP in response to the incubation with SNP as previously reported, whereas both ameboid and ramified microglial cells did not respond to the treatment. Atrial natriuretic peptide, a stimulator of particulate guanylyl cyclase, enhanced cGMP synthesis in astrocytes in some brain regions but not in oligodendrocytes. These findings indicate that oligodendrocytes in the immature rat brain express soluble guanylyl cyclase. No cGMP-positive oligodendrocytes were found in the mature rat brain, suggesting that cGMP may mediate signals related to myelinogenesis in the rat brain.

A role for gelsolin in actuating epidermal growth factor receptor-mediated cell motility

Phospholipase C-gamma (PLC gamma) is required for EGF-induced motility (Chen, P., H. Xie, M.C. Sekar, K.B. Gupta, and A. Wells. J. Cell Biol. 1994. 127:847-857); however, the molecular basis of how PLC gamma modulates the actin filament network underlying cell motility remains undetermined. We propose that one connection to the actin cytoskeleton is direct hydrolysis of PIP2 with subsequent mobilization of membrane-associated actin modifying proteins. We used signaling-restricted EGFR mutants expressed in receptor-devoid NR6 fibroblast cells to investigate whether EGFR activation of PLC causes gelsolin mobilization from the cell membrane in vivo and whether this translocation facilitates cell movement. Gelsolin anti-sense oligonucleotide (20 microM) treatment of NR6 cells expressing the motogenic full-length (WT) and truncated c'1000 EGFR decreased endogenous gelsolin by 30-60%; this resulted in preferential reduction of EGF (25 nM)-induced cell movement by > 50% with little effect on the basal motility. As 14 h of EGF stimulation of cells did not increase total cell gelsolin content, we determined whether EGF induced redistribution of gelsolin from the membrane fraction. EGF treatment decreased the gelsolin mass associated with the membrane fraction in motogenic WT and c'1000 EGFR NR6 cells but not in cells expressing the fully mitogenic, but nonmotogenic c'973 EGFR. Blocking PLC activity with the pharmacologic agent U73122 (1 microM) diminished both this mobilization of gelsolin and EGF-induced motility, suggesting that gelsolin mobilization is downstream of PLC. Concomitantly observed was reorganization of submembranous actin filaments correlating directly with PLC activation and gelsolin mobilization. In vivo expression of a peptide that is reported to compete in vitro with gelsolin in binding to PIP2 dramatically increased basal cell motility in NR6 cells expressing either motogenic (WT and c'1000) or nonmotogenic (c'973) EGFR; EGF did not further augment cell motility and gelsolin mobilization. Cells expressing this peptide demonstrated actin reorganization similar to that observed in EGF-treated control cells; the peptide-induced changes were unaffected by U73122. These data suggest that much of the EGF-induced motility and cytoskeletal alterations can be reproduced by displacement of select actin-modifying proteins from a PIP2-bound state. This provides a signaling mechanism for translating cell surface receptor-mediated biochemical reactions to the cell movement machinery.

Biphasic pattern of gelsolin expression and variations in gelsolin-actin interactions during myogenesis

During myogenesis in vitro, the amount of gelsolin in myogenic cells increased by a factor of approximately 3 from about 200 ng to a maximum of 750 ng per milligram of total protein. Gelsolin increased steadily from the myoblast state to terminally differentiated myotubes containing abundant cross-striated myofibrils. At the same time, the amount of total actin varied by only about 30%, the molar ratio of gelsolin:actin increased from 1:500 to approximately 1:150. This modulation of gelsolin expression was observed both in avian and mammalian myocultures. Once the state of terminal differentiation in myocultures was attained, the amount of gelsolin decreased again. On the other hand, gelsolin decreased continuously in the postnatal mouse muscle by a factor of approximately 5 between Day 1 and Day 12 after birth. When myogenic cells from various stages of differentiation were extracted with Triton X-100, the majority of gelsolin was soluble, whereas a minor fraction was tightly associated with the cytoskeleton. The actual amount of insoluble gelsolin depended on both the Ca2+ concentration during extraction and the degree of differentiation. Whereas at [Ca2+] > 10(-5) M about one-third of the total gelsolin was associated with the cytoskeleton at all stages of differentiation, the amount of insoluble gelsolin after Triton extraction in the presence of EGTA increased from 3 to 17% during differentiation. The amount of soluble actin decreased from 40 to 25% during the same period, independent of the Ca2+ concentration. We calculated that the amount of gelsolin associated with the cytoskeletal or myofibrillar system is approximately 20-fold higher in differentiated myotubes than in early myotubes, indicating a functional role of gelsolin for myofibrillar assembly.

Trichostatin A induces morphological changes and gelsolin expression by inhibiting histone deacetylase in human carcinoma cell lines

Trichostatin A (TSA) is a Streptomyces metabolite which specifically inhibits mammalian histone deacetylase at a nanomolar concentration and causes accumulation of highly acetylated histone molecules in mammalian cells. The effects of TSA on the morphology and the cell cycle of the human carcinoma cell lines, T24 and HeLa, were investigated. The morphology of T24 and HeLa cells dramatically changed and actin stress fibers reappeared during the treatment with TSA. The morphological change was not observed with chemically synthesized (S)-TSA and trichostatic acids, which are inactive to inhibit histone deacetylase. Cell cycle progression of these cells was blocked by TSA at G1 phase (HeLa) or G1 and G2 phases (T24). An RNA synthesis inhibitor, actinomycin D, and a protein synthesis inhibitor, cycloheximide, inhibited the morphological changes by TSA, suggesting that TSA induces expression of a new gene(s) followed by de novo protein synthesis, which is required for the actin microfilament reorganization. An approximately 7-fold (T24) or 12-fold (HeLa) increase in the intracellular level of gelsolin, an actin regulatory protein, was found in the cells treated with TSA for 24 h. These results suggest that gelsolin is one of the putative proteins necessary for the morphological changes of human carcinoma cells induced by TSA.