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.

Nm23-h1 binds to gelsolin and inactivates its actin-severing capacity to promote tumor cell motility and metastasis

Nm23-H1 has been identified as a metastasis suppressor gene, but its protein interactions have yet to be understood with any mechanistic clarity. In this study, we evaluated the proteomic spectrum of interactions made by Nm23-H1 in 4T1 murine breast cancer cells derived from tissue culture, primary mammary tumors, and pulmonary metastases. By this approach, we identified the actin-severing protein Gelsolin as binding partner for Nm23-H1, verifying their interaction by coimmunoprecipitation in 4T1 cells as well as in human MCF7, MDA-MB-231T, and MDA-MB-435 breast cancer cells. In Gelsolin-transfected cells, coexpression of Nm23-H1 abrogated the actin-severing activity of Gelsolin. Conversely, actin severing by Gelsolin was abrogated by RNA interference-mediated silencing of endogenous Nm23-H1. Tumor cell motility was negatively affected in parallel with Gelsolin activity, suggesting that Nm23-H1 binding inactivated the actin-depolymerizing function of Gelsolin to inhibit cell motility. Using indirect immunoflourescence to monitor complexes formed by Gelsolin and Nm23-H1 in living cells, we observed their colocalization in a perinuclear cytoplasmic compartment that was associated with the presence of disrupted actin stress fibers. In vivo analyses revealed that Gelsolin overexpression increased the metastasis of orthotopically implanted 4T1 or tail vein-injected MDA-MB-231T cells (P = 0.001 and 0.04, respectively), along with the proportion of mice with diffuse liver metastases, an effect ablated by coexpression of Nm23-H1. We observed no variation in proliferation among lung metastases. Our findings suggest a new actin-based mechanism that can suppress tumor metastasis.

Nm23-h1 binds to gelsolin and inactivates its actin-severing capacity to promote tumor cell motility and metastasis

Nm23-H1 has been identified as a metastasis suppressor gene, but its protein interactions have yet to be understood with any mechanistic clarity. In this study, we evaluated the proteomic spectrum of interactions made by Nm23-H1 in 4T1 murine breast cancer cells derived from tissue culture, primary mammary tumors, and pulmonary metastases. By this approach, we identified the actin-severing protein Gelsolin as binding partner for Nm23-H1, verifying their interaction by coimmunoprecipitation in 4T1 cells as well as in human MCF7, MDA-MB-231T, and MDA-MB-435 breast cancer cells. In Gelsolin-transfected cells, coexpression of Nm23-H1 abrogated the actin-severing activity of Gelsolin. Conversely, actin severing by Gelsolin was abrogated by RNA interference-mediated silencing of endogenous Nm23-H1. Tumor cell motility was negatively affected in parallel with Gelsolin activity, suggesting that Nm23-H1 binding inactivated the actin-depolymerizing function of Gelsolin to inhibit cell motility. Using indirect immunoflourescence to monitor complexes formed by Gelsolin and Nm23-H1 in living cells, we observed their colocalization in a perinuclear cytoplasmic compartment that was associated with the presence of disrupted actin stress fibers. In vivo analyses revealed that Gelsolin overexpression increased the metastasis of orthotopically implanted 4T1 or tail vein-injected MDA-MB-231T cells (P = 0.001 and 0.04, respectively), along with the proportion of mice with diffuse liver metastases, an effect ablated by coexpression of Nm23-H1. We observed no variation in proliferation among lung metastases. Our findings suggest a new actin-based mechanism that can suppress tumor metastasis.

Coordinated waves of actomyosin flow and apical cell constriction immediately after wounding

Epithelial wound healing relies on tissue movements and cell shape changes. Our work shows that, immediately after wounding, there was a dramatic cytoskeleton remodeling consisting of a pulse of actomyosin filaments that assembled in cells around the wound edge and flowed from cell to cell toward the margin of the wound. We show that this actomyosin flow was regulated by Diaphanous and ROCK and that it elicited a wave of apical cell constriction that culminated in the formation of the leading edge actomyosin cable, a structure that is essential for wound closure. Calcium signaling played an important role in this process, as its intracellular concentration increased dramatically immediately after wounding, and down-regulation of transient receptor potential channel M, a stress-activated calcium channel, also impaired the actomyosin flow. Lowering the activity of Gelsolin, a known calcium-activated actin filament-severing protein, also impaired the wound response, indicating that cleaving the existing actin filament network is an important part of the cytoskeleton remodeling process.

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.

Treponema denticola major outer sheath protein impairs the cellular phosphoinositide balance that regulates neutrophil chemotaxis

The major outer sheath protein (Msp) of Treponema denticola inhibits neutrophil polarization and directed chemotaxis together with actin dynamics in vitro in response to the chemoattractant N-formyl-methionine-leucine-phenylanine (fMLP). Msp disorients chemotaxis through inhibition of a Rac1-dependent signaling pathway, but the upstream mechanisms are unknown. We challenged murine bone marrow neutrophils with enriched native Msp to determine the role of phospholipid modifying enzymes in chemotaxis and actin assembly downstream of fMLP-stimulation. Msp modulated cellular phosphoinositide levels through inhibition of phosphatidylinositol 3-kinase (PI3-kinase) together with activation of the lipid phosphatase, phosphatase and tensin homolog deleted on chromosome 10 (PTEN). Impaired phosphatidylinositol[(3,4,5)]-triphosphate (PIP3) levels prevented recruitment and activation of the downstream mediator Akt. Release of the actin capping proteins gelsolin and CapZ in response to fMLP was also inhibited by Msp exposure. Chemical inhibition of PTEN restored PIP3 signaling, as measured by Akt activation, Rac1 activation, actin uncapping, neutrophil polarization and chemotaxis in response to fMLP-stimulation, even in the presence of Msp. Transduction with active Rac1 also restored fMLP-mediated actin uncapping, suggesting that Msp acts at the level of PIP3 in the hierarchical feedback loop of PIP3 and Rac1 activation. Taken together, Msp alters the phosphoinositide balance in neutrophils, impairing the cell “compass”, which leads to inhibition of downstream chemotactic events.

ATF3 suppresses metastasis of bladder cancer by regulating gelsolin-mediated remodeling of the actin cytoskeleton

Bladder cancer is associated with high recurrence and mortality rates due to metastasis. The elucidation of metastasis suppressors may offer therapeutic opportunities if their mechanisms of action can be elucidated and tractably exploited. In this study, we investigated the clinical and functional significance of the transcription factor activating transcription factor 3 (ATF3) in bladder cancer metastasis. Gene expression analysis revealed that decreased ATF3 was associated with bladder cancer progression and reduced survival of patients with bladder cancer. Correspondingly, ATF3 overexpression in highly metastatic bladder cancer cells decreased migration in vitro and experimental metastasis in vivo. Conversely, ATF3 silencing increased the migration of bladder cancer cells with limited metastatic capability in the absence of any effect on proliferation. In keeping with their increased motility, metastatic bladder cancer cells had increased numbers of actin filaments. Moreover, ATF3 expression correlated with expression of the actin filament severing protein gelsolin (GSN). Mechanistic studies revealed that ATF3 upregulated GSN, whereas ATF3 silencing reduced GSN levels, concomitant with alterations in the actin cytoskeleton. We identified six ATF3 regulatory elements in the first intron of the GSN gene confirmed by chromatin immunoprecipitation analysis. Critically, GSN expression reversed the metastatic capacity of bladder cancer cells with diminished levels of ATF3. Taken together, our results indicate that ATF3 suppresses metastasis of bladder cancer cells, at least in part through the upregulation of GSN-mediated actin remodeling. These findings suggest ATF3 coupled with GSN as prognostic markers for bladder cancer metastasis.

[Amyloid polyneuropathies--biochemical and genetic aspects]

Familial amyloid polyneuropathies (FAP) are among the most frequent hereditary amyloidoses. These are serious, most often fatal diseases with autosomal dominant inheritance. FAP can be caused by mutations in four genes, namely those encoding transthyretin, Al-apoliprotein, gelsolin, and beta-2 microglobulin. Transthyretin is a tetramer composed of four identical subunits linked by non covalent bonds and bearing binding sites for thyroxine (T4) and retinol-binding protein (RBP). More than 120 transthyretin gene sequence variations have been characterized, of which only 80% seem to be pathogenic. Gene mutations can induce tetramer destabilization, thereby generating misfolded monomers that aggregate into insoluble amyloidfibrils. The mutation spectrum is highly variable across countries. For example, while the Val30Met mutation is found in 95% of the Portuguese and Swedish patient populations, high mutational heterogeneity is observed in France. Age of onset and clinical signs are influenced by numerous factors, especially the mutation type and the country, but the mechanisms underlying this variability are not fully clear. The three-dimensional structure of the normal transthyretin protein and a dozen mutants is now known, providing insights into the deleterious effects of mutations. A better understanding of the mechanisms involved in amyloid fibril formation has led to the development of drugs that inhibit transthyretin tetramer destabilization. It is hoped that, within afew years, such drugs will replace liver transplantation, which is currently the only curative treatment.

[Familial amyloidotic polyneuropathies]

Transthyretin familial amyloid polyneuropathy (TTRFAP) is an autosomal dominant neuropathy that is fatal within about 10 years after symptom onset. TTRFAP is observed worldwide, albeit with a higher frequency of the most common variant, Val30met, in Portugal, Sweden and Japan. Various phenotypic differences are observed. TTRFAP should be considered in patients with a progressive axonal polyneuropathy of unknown origin, especially when associated with autonomic nervous system dysfunction. A positive family history is found in most cases when onset begins around 30 years of age, while late-onset FAP is often sporadic and may be confused with chronic inflammatory demyelinating polyneuropathy. Nerve biopsy is often used to confirm the presence of extracellular amyloid deposits in interstitial tissue of the endoneurial space, although amyloid can also befound in muscle, salivary gland and abdominal fat. It is important to stress that biopsy negativity does not rule out amyloidosis. Genetic testing for TTR gene mutations should be performed in case of progressive length-dependent axonal polyneuropathy predominantly involving small nerve fibers.

Gelsolin induces colorectal tumor cell invasion via modulation of the urokinase-type plasminogen activator cascade

Gelsolin is a cytoskeletal protein which participates in actin filament dynamics and promotes cell motility and plasticity. Although initially regarded as a tumor suppressor, gelsolin expression in certain tumors correlates with poor prognosis and therapy-resistance. In vitro, gelsolin has anti-apoptotic and pro-migratory functions and is critical for invasion of some types of tumor cells. We found that gelsolin was highly expressed at tumor borders infiltrating into adjacent liver tissues, as examined by immunohistochemistry. Although gelsolin contributes to lamellipodia formation in migrating cells, the mechanisms by which it induces tumor invasion are unclear. Gelsolin's influence on the invasive activity of colorectal cancer cells was investigated using overexpression and small interfering RNA knockdown. We show that gelsolin is required for invasion of colorectal cancer cells through matrigel. Microarray analysis and quantitative PCR indicate that gelsolin overexpression induces the upregulation of invasion-promoting genes in colorectal cancer cells, including the matrix-degrading urokinase-type plasminogen activator (uPA). Conversely, gelsolin knockdown reduces uPA levels, as well as uPA secretion. The enhanced invasiveness of gelsolin-overexpressing cells was attenuated by treatment with function-blocking antibodies to either uPA or its receptor uPAR, indicating that uPA/uPAR activity is crucial for gelsolin-dependent invasion. In summary, our data reveals novel functions of gelsolin in colorectal tumor cell invasion through its modulation of the uPA/uPAR cascade, with potentially important roles in colorectal tumor dissemination to metastatic sites.

Visual insight into how low pH alone can induce actin-severing ability in gelsolin under calcium-free conditions

Gelsolin is a key actin cytoskeleton-modulating protein primarily regulated by calcium and phosphoinositides. In addition, low pH has also been suggested to activate gelsolin in the absence of Ca(2+) ions, although no structural insight on this pathway is available except for a reported decrement in its diffusion coefficient at low pH. We also observed ~1.6-fold decrease in the molecular mobility of recombinant gelsolin when buffer pH was lowered from 9 to 5. Analysis of the small angle x-ray scattering data collected over the same pH range indicated that the radius of gyration and maximum linear dimension of gelsolin molecules increased from 30.3 to 34.1 Å and from 100 to 125 Å, respectively. Models generated for each dataset indicated that similar to the Ca(2+)-induced process, low pH also promotes unwinding of this six-domain protein but only partially. It appeared that pH is able to induce extension of the G1 domain from the rest of the five domains, whereas the Ca(2+)-sensitive latch between G2 and G6 domains remains closed. Interestingly, increasing the free Ca(2+) level to merely ~40 nM, the partially open pH 5 shape "sprung open" to a shape seen earlier for this protein at pH 8 and 1 mm free Ca(2+). Also, pH alone could induce a shape where the g3-g4 linker of gelsolin was open when we truncated the C-tail latch from this protein. Our results provide insight into how under physiological conditions, a drop in pH can fully activate the F-actin-severing shape of gelsolin with micromolar levels of Ca(2+) available.

Proteomic evaluation and validation of cathepsin D regulated proteins in macrophages exposed to Streptococcus pneumoniae

Macrophages are central effectors of innate immune responses to bacteria. We have investigated how activation of the abundant macrophage lysosomal protease, cathepsin D, regulates the macrophage proteome during killing of Streptococcus pneumoniae. Using the cathepsin D inhibitor pepstatin A, we demonstrate that cathepsin D differentially regulates multiple targets out of 679 proteins identified and quantified by eight-plex isobaric tag for relative and absolute quantitation. Our statistical analysis identified 18 differentially expressed proteins that passed all paired t-tests (α = 0.05). This dataset was enriched for proteins regulating the mitochondrial pathway of apoptosis or inhibiting competing death programs. Five proteins were selected for further analysis. Western blotting, followed by pharmacological inhibition or genetic manipulation of cathepsin D, verified cathepsin D-dependent regulation of these proteins, after exposure to S. pneumoniae. Superoxide dismutase-2 up-regulation was temporally related to increased reactive oxygen species generation. Gelsolin, a known regulator of mitochondrial outer membrane permeabilization, was down-regulated in association with cytochrome c release from mitochondria. Eukaryotic elongation factor (eEF2), a regulator of protein translation, was also down-regulated by cathepsin D. Using absence of the negative regulator of eEF2, eEF2 kinase, we confirm that eEF2 function is required to maintain expression of the anti-apoptotic protein Mcl-1, delaying macrophage apoptosis and confirm using a murine model that maintaining eEF2 function is associated with impaired macrophage apoptosis-associated killing of Streptococcus pneumoniae. These findings demonstrate that cathepsin D regulates multiple proteins controlling the mitochondrial pathway of macrophage apoptosis or competing death processes, facilitating intracellular bacterial killing.

Inhibition of androgen receptor functions by gelsolin FxxFF peptide delivered by transfection, cell-penetrating peptides, and lentiviral infection

BACKGROUND

Prostate cancer (PC) growth is dependent on the androgen-androgen receptor (AR) axis. Because current androgen ablation therapies of PC lead to resistance, novel approaches to block AR activity are urgently needed.

METHODS

We inhibited AR function beyond the level of hormone binding by blockade of the coactivator groove in the ligand-binding domain (LBD) using a high-affinity gelsolin FxxFF peptide. Following peptide selection, the effect of the gelsolin FxxFF peptide on AR functions was determined in Hep3B cells that were transiently transfected with pM-peptide expression vectors or were incubated with synthetic gelsolin FxxFF peptide coupled to the TAT cell-penetrating peptide. Lentiviruses expressing the gelsolin FxxFF peptide were used to study endogenous AR target gene expression in LNCaP cells.

RESULTS

pM-Gelsolin FxxFF efficiently interfered with AR N/C interaction and specifically inhibited AR-regulated reporter gene activity. The peptide did not inhibit progesterone receptor (PR) and glucocorticoid receptor (GR) activity, nor constitutively active gene promoters. The peptide also specifically blocked in vitro interactions of AR LBD with peptides. Like the gelsolin FxxFF peptide expressed by an expression vector, synthetic TAT-gelsolin FxxFF peptide efficiently blocked AR N/C interaction and inhibited full-length AR-regulated reporter gene activity. It hardly affected PR and GR activity, but the effect on constitutively active promoters was variable. Lentiviral gelsolin FxxFF peptide inhibited expression of KLK2 and NDRG1, but hardly affected PSA and TMPRSS2.

CONCLUSIONS

Our results show that the AR coactivator groove may function as a target to overcome therapeutic failure that arises during current androgen ablation therapies.

Gelsolin plays a role in the actin polymerization complex of hair cell stereocilia

A complex of proteins scaffolded by the PDZ protein, whirlin, reside at the stereocilia tip and are critical for stereocilia development and elongation. We have shown that in outer hair cells (OHCs) whirlin is part of a larger complex involving the MAGUK protein, p55, and protein 4.1R. Whirlin interacts with p55 which is expressed exclusively in outer hair cells (OHC) in both the long stereocilia that make up the stereocilia bundle proper as well as surrounding shorter microvilli that will eventually regress. In erythrocytes, p55 forms a tripartite complex with protein 4.1R and glycophorin C promoting the assembly of actin filaments and the interaction of whirlin with p55 indicates that it plays a similar role in OHC stereocilia. However, the components directly involved in actin filament regulation in stereocilia are unknown. We have investigated additional components of the whirlin interactome by identifying interacting partners to p55. We show that the actin capping and severing protein, gelsolin, is a part of the whirlin complex. Gelsolin is detected in OHC where it localizes to the tips of the shorter rows but not to the longest row of stereocilia and the pattern of localisation at the apical hair cell surface is strikingly similar to p55. Like p55, gelsolin is ablated in the whirler and shaker2 mutants. Moreover, in a gelsolin mutant, stereocilia in the apex of the cochlea become long and straggly indicating defects in the regulation of stereocilia elongation. The identification of gelsolin provides for the first time a link between the whirlin scaffolding protein complex involved in stereocilia elongation and a known actin regulatory molecule.

A llama-derived gelsolin single-domain antibody blocks gelsolin-G-actin interaction

RNA interference has tremendously advanced our understanding of gene function but recent reports have exposed undesirable side-effects. Recombinant Camelid single-domain antibodies (VHHs) provide an attractive means for studying protein function without affecting gene expression. We raised VHHs against gelsolin (GsnVHHs), a multifunctional actin-binding protein that controls cellular actin organization and migration. GsnVHH-induced delocalization of gelsolin to mitochondria or the nucleus in mammalian cells reveals distinct subpopulations including free gelsolin and actin-bound gelsolin complexes. GsnVHH 13 specifically recognizes Ca(2+)-activated gelsolin (K (d) approximately 10 nM) while GsnVHH 11 binds gelsolin irrespective of Ca(2+) (K (d) approximately 5 nM) but completely blocks its interaction with G-actin. Both GsnVHHs trace gelsolin in membrane ruffles of EGF-stimulated MCF-7 cells and delay cell migration without affecting F-actin severing/capping or actin nucleation activities by gelsolin. We conclude that VHHs represent a potent way of blocking structural proteins and that actin nucleation by gelsolin is more complex than previously anticipated.

[Hereditary gelsolin amyloidosis--40 years of Meretoja disease]

Hereditary gelsolin amyloidosis is an autosomally dominantly inherited systemic disease, first described in 1969 by the Finnish ophthalmologist Jouko Meretoja. The estimated number of disease carriers in Finland is almost 1 000, and the disease has subsequently been found in many other countries as well. It's typical initial manifestation is lattice corneal dystrophy, detected at biomicroscopic examination of the eye by the age of 25 to 30 years, followed by slowly progressing cranial neuropathy with bilateral facial palsy, polyneuropathy and generalized cutis laxa. Meretoja's disease is caused by mutations of the gelsolin gene, leading to the production and aberrant processing of variant gelsolin and deposition of its fragments in various tissues in the form of amyloid fibrils.

Lattice corneal dystrophy, gelsolin type (Meretoja's syndrome)

PURPOSE

This paper reviews current knowledge about the pathogenesis, clinical manifestations and treatment of lattice corneal dystrophy, gelsolin type (LCD2, Meretoja's syndrome).

METHODS

Material is derived from literature searches, a case study of a Finnish patient living in Sweden, and interviews in Helsinki with Professor Ahti Tarkkanen and Dr Sari Kiuru-Enari, both of whom have extensive first-hand experience in treating patients with the disease.

RESULTS

The disease is now reported from several countries in Europe, as well as Japan, the USA and Iran. Treatment is symptomatic and is based on eye lubrication combined with rigorous monitoring of intraocular pressure to reduce corneal haze and postpone the need for keratoplasty. When systemic symptoms occur, the ophthalmologist should consult other specialists.

CONCLUSIONS

The disease is probably under-reported and is almost certainly to be found in more countries, including Sweden. Every ophthalmologist should be vigilant and consider this diagnosis when discovering a corneal lattice dystrophy, especially because the disease is an inherited, lifelong chronic condition with systemic symptoms.

Purification of cytoplasmic actin by affinity chromatography using the C-terminal half of gelsolin

A new rapid method of the cytoplasmic actin purification, not requiring the use of denaturants or high concentrations of salt, was developed, based on the affinity chromatography using the C-terminal half of gelsolin (G4-6), an actin filament severing and capping protein. When G4-6 expressed in Escherichia coli was added to the lysate of HeLa cells or insect cells infected with a baculovirus encoding the beta-actin gene, in the presence of Ca(2+) and incubated overnight at 4 degrees C, actin and G4-6 were both detected in the supernatant. Following the addition of Ni-Sepharose beads to the mixture, only actin was eluted from the Ni-NTA column by a Ca(2+)-chelating solution. The functionality of the cytoplasmic actins thus purified was confirmed by measuring the rate of actin polymerization, the gliding velocity of actin filaments in an in vitro motility assay on myosin V-HMM, and the ability to activate the ATPase activity of myosin V-S1.

[Genetic factors for cerebral amyloid angiopathy]

Cerebral amyloid angiopathy (CAA) is cerebrovascular amyloid deposition and is related to stroke and dementia. CAA is classified into 6 types according to the biochemical properties of amyloid proteins, and among 6 types, the sporadic CAA of amyloid beta protein (Abeta) type is most frequently found in elderly people or patients with Alzheimer's disease (AD). In sporadic CAA of the Abeta type, the epsilon4 allele of the apolipoprotein E gene is associated with increased vascular Abeta deposition, while the epsilon2 allele is associated with CAA-related intracerebral hemorrhage. We have also reported that the genetic polymorphisms of presenilin-1, neprilysin, transforming growth factor beta-1, and alpha1-antichymotrypsin are associated with CAA. In the case of hereditary CAA of the Abeta type, mutations in the genes of amyloid precursor protein (APP) and presenilins have been reported. Interestingly, the missense mutations associated with CAA are located in the middle portion of Abeta, while those associated with familial AD (FAD) are near the N- or C- terminals of Abeta. Individuals with FAD with APP duplication have been reported to present with severe CAA. Some of the FAD patients with mutations in the presenilin genes and patients with Down syndrome also show CAA as a complication. Besides sporadic or hereditary CAA of the Abeta type, hereditary CAA with cerebrovascular deposition of cystatin C, transthyretin, gelsolin, prion protein, and ABri/ADan have also been reported in association with mutations in the genes of the precursor proteins. Better understanding of the genetic factors influencing CAA will lead to identification of novel diagnostic markers and the development of preventive for CAA and CAA-related disorders.

In colon carcinogenesis, the cytoskeletal protein gelsolin is down-regulated during the transition from adenoma to carcinoma

The actin-binding protein gelsolin is involved in cell motility via the regulation of actin cytoskeleton, and its expression is modified in several human cancers. However, the potential implication of this protein in colorectal carcinogenesis is debated. By using immunohistochemistry, we studied gelsolin expression in 69 cases of colon adenocarcinomas and in 72 lesions representative of the different stages of colonic tumorigenesis. In addition, we performed Northern blot analysis of gelsolin messenger RNA in 12 paired samples of human colon cancer and normal corresponding mucosa. Gelsolin protein and messenger RNA expressions were severely down-regulated in all adenocarcinomas tested. Moreover, gelsolin protein was down-regulated in a large proportion of high-grade adenomas (14/16) before the acquisition of invasive properties but in only a small proportion of low grade adenomas and serrated adenomas (2/30) and in none of the 9 cases of nonneoplastic hyperplastic polyps tested. Our results therefore demonstrate that gelsolin down-regulation is an early and almost constant event in colon carcinogenesis and is associated with the transition from adenoma to carcinoma.

The molecular biology and clinical features of amyloid neuropathy

Neuropathy is often a major manifestation of systemic amyloidosis. It is most frequently seen in patients with hereditary transthyretin (TTR) amyloidosis, but is also present in 20% of patients with systemic immunoglobulin light chain (primary) amyloidosis. Familial amyloid polyneuropathy (FAP) is the most common form of inherited amyloidotic polyneuropathy, with clinical and electrophysiologic findings similar to neuropathies with differing etiologies (e.g., diabetes mellitus). Hereditary amyloidosis is an adult-onset autosomal-dominant disease with varying degrees of penetrance. It is caused by specific gene mutations, but demonstration that a patient has one such mutation does not confirm the diagnosis of amyloidosis. Diagnosis requires tissue biopsy with demonstration of amyloid deposits either by special histochemical stains or electron microscopy. Transthyretin amyloidosis is treated by liver transplantation, which eliminates the mutated transthyretin from the blood, but for some patients continued amyloid deposition can occur from wild-type (normal) transthyretin. Presently, a study is ongoing to determine whether amyloid deposition can be inhibited by small organic molecules that are hypothesized to affect the fibril-forming ability of transthyretin. Proposed gene therapy with antisense oligonucleotides (ASOs) to suppress hepatic transthyretin synthesis is effective in a transgenic mouse model but has not yet been tested in humans.

Induced expression of the transcription of tropomodulin 1 by Wnt5a and characterization of the tropomodulin 1 promoter

Microarray analysis was carried out to identify novel downstream target genes regulated by non-canonical Wnt signaling. We found that Tmod1, known as an actin-capping protein, is up-regulated by Wnt5a, while gelsolin, known as an actin-severing protein, is down-regulated by Wnt5a. As expected from the roles of genes regulated by Wnt5a, L929 cells expressing Wnt5a show abnormal cell shape and a reduced migration rate. Cloning and analysis of the putative promoter show that two conserved sequences, one in the 5'-end of the first exon and the other in the intron next to the first exon, are necessary for the basal promoter activity.

Concurrent down-regulation of Egr-1 and gelsolin in the majority of human breast cancer cells

A growing body of evidence suggests that early growth response-1 (Egr-1), a transcription factor, may function as a tumor suppressor. The aim of this study was to gain more evidence to support the role of Egr-1 in the suppression of cancer cell growth and to examine the potential correlation between Egr-1 and gelsolin.

MATERIALS AND METHODS

Histochemical staining coupled with breast cancer tissue arrays were used to examine the expression levels of Egr-1 and gelsolin. Reporter assays and gel shift were used to study the transcriptional activity of Egr-1 on the regulation of gelsolin.

RESULTS

Our data showed that most normal mammary tissues expressed high levels of Egr-1, while the majority of breast cancer tissues expressed very small amounts of Egr-1. The expression pattern of Egr-1 in human breast cancer tissues was highly correlated with gelsolin expression. Induction of Egr-1 by serum stimulation accompanied the increase of gelsolin expression. In cells lacking the induction of Egr-1 in response to serum stimulation, gelsolin expression remained unchanged. Furthermore, gelsolin promoter activity was profoundly reduced in Egr-1 null mouse embryonic fibroblasts compared to Egr-1 wild-type mouse embryonic fibroblasts. Gel shift experiments indicated that Egr-1 can directly bind to the gelsolin promoter.

CONCLUSION

Our results suggest that Egr-1 may be an important breast cancer marker and that an as yet uncharacterized pathway involved in Egr-1 and gelsolin expression exists which leads to breast cancer cell development.

Transgenic analysis of the anterior eye-specific enhancers of the zebrafish gelsolin-like 1 (gsnl1) gene

The anterior segment of the eye includes such structures as the cornea, lens, iris, and ciliary body and is essential for many visual and physiological functions of the eye. The zebrafish gelsolin-like 1 (gsnl1) gene encodes an actin regulatory protein and is expressed in the anterior segment of the eye. We report the transgenic analyses of the gsnl1 promoter and enhancer that are required for expression in the anterior segment of the eye. A 6.4-kb genomic fragment upstream from the translation initiation site (ATG) was capable of driving green fluorescent protein (GFP) expression in transient transgenic embryos and stable transgenic adult fish, which mimics the endogenous gsnl1 expression. The GFP expression was localized in the corneal epithelium (CE) and the annular ligament (AL) at the iridocorneal angle. A unique enhancer for each of these two tissues was identified at 3.7-kb upstream from the ATG. The 60-bp AL and 25-bp CE enhancers were separated by 100-bp and functioned independently from each other. Deletion analysis indicated that the proximal promoter was located 1.6-kb upstream from the ATG. Stable GFP transgenic lines were established for future studies of genetic regulation in the anterior segment of the fish eye.