Calponin

asb5a/asb5b Double Knockout Affects Zebrafish Cardiac Contractile Function

Ankyrin repeat and suppression-of-cytokine-signaling box (Asb) proteins, a subset of ubiquitin ligase E3, include Asb5 with six ankyrin-repeat domains. Zebrafish harbor two asb5 gene isoforms, asb5a and asb5b. Currently, the effects of asb5 gene inactivation on zebrafish embryonic development and heart function are unknown. Using CRISPR/Cas9, we generated asb5a-knockout zebrafish, revealing no abnormal phenotypes at 48 h post-fertilization (hpf). In situ hybridization showed similar asb5a and asb5b expression patterns, indicating the functional redundancy of these isoforms. Morpholino interference was used to target asb5b in wild-type and asb5a-knockout zebrafish. Knocking down asb5b in the wild-type had no phenotypic impact, but simultaneous asb5b knockdown in asb5a-knockout homozygotes led to severe pericardial cavity enlargement and atrial dilation. RNA-seq and cluster analyses identified significantly enriched cardiac muscle contraction genes in the double-knockout at 48 hpf. Moreover, semi-automatic heartbeat analysis demonstrated significant changes in various heart function indicators. STRING database/Cytoscape analyses confirmed that 11 cardiac-contraction-related hub genes exhibited disrupted expression, with three modules containing these genes potentially regulating cardiac contractile function through calcium ion channels. This study reveals functional redundancy in asb5a and asb5b, with simultaneous knockout significantly impacting zebrafish early heart development and contraction, providing key insights into asb5's mechanism.

Quantitative proteomics and in-cell cross-linking reveal cellular reorganisation during early neuronal differentiation of SH-SY5Y cells

The neuroblastoma cell line SH-SY5Y is commonly employed to study neuronal function and disease. This includes cells grown under standard conditions or differentiated to neuron-like cells by administration of chemical reagents such as retinoic acid (RA) or phorbol-12-myristate-13-acetate (PMA). Even though SH-SY5Y cells are widely explored, a complete description of the resulting proteomes and cellular reorganisation during differentiation is still missing. Here, we relatively quantify the proteomes of cells grown under standard conditions and obtained from two differentiation protocols employing RA or a combination of RA and PMA. Relative quantification and KEGG pathway analysis of the proteins reveals the presence of early differentiating cells and provides a list of marker proteins for undifferentiated and differentiated cells. For characterisation of neuronal sub-types, we analyse expression of marker genes and find that RA-differentiated cells are acetylcholinergic and cholinergic, while RA/PMA-differentiated cells show high expression of acetylcholinergic and dopaminergic marker genes. In-cell cross-linking further allows capturing protein interactions in different cellular organelles. Specifically, we observe structural reorganisation upon differentiation involving regulating protein factors of the actin cytoskeleton.

Quantitative proteomic analyses are employed to explore the changes in the proteome that occur upon neuronal differentiation in the SH-SY5Y cell line.

Identification of Somatic Proteins in Haemonchus Contortus Infective Larvae (L3) and Adults

Haemonchus contortus is considered the most pathogenic nematode in sheep production systems based on grazing. Comparing infective larvae (L₃) with adult parasites can lead to the identification of proteins that play an important role in parasite-host interactions. In this study, we report a list of H. contortus somatic proteins and made a comparative analysis of somatic proteins of L₃ and adult worms. L₃ and adult parasites were subjected to protein extraction and subsequently to peptide fractionation. Peptides were analysed by mass spectrometry and LC-MS/MS data analysis. Data analysis and search on SEQUEST and MASCOT against H. contortus from the WormBase ParaSite database resulted in the identification of 775 unique peptide sequences corresponding to 227 proteins at 1 % FDR. From these, 18 proteins were specific to L₃ and 63 to adult parasites. The gene ontology (GO) enrichment analysis of the proteins specific to L₃ and adult worms to gain insight into cellular components, molecular functions and biological processes that affect the parasite-host interaction showed some differences between the two parasite stages. The list of proteins found provides a database to identify target proteins that could be useful as biomarkers of the infection or in the generation of anthelmintic drugs that inhibit proteins essential for the establishment of the infection and the survival of adult parasites. They can also serve as new candidates for vaccine research.

Differential expression of Acanthamoeba castellanii proteins during amoebic keratitis in rats

Amoebic keratitis (AK) is a sight-threatening infection characterized by a severe inflammation of the cornea, caused by the free-living protozoan of the genus Acanthamoeba. Identification of amoebic proteins involved in AK pathogenesis may help to elucidate molecular mechanisms of infection and contribute to indicate diagnostic and therapeutic targets. In this study, we evaluated changes in the expression profile of Acanthamoeba proteins triggered by the invasive process, using an approach involving two-dimensional polyacrylamide gel electrophoresis (2DE PAGE), followed by mass spectrometry identification (ESI-IT-TOF LC-MSn). AK was induced by intrastromal inoculation in Wistar rats, using trophozoites from a T4 genotype, human case-derived A. castellanii strain under prolonged axenic culture. Cultures re-isolated from the lesions after two successive passages in the animals were used as biological triplicate for proteomic experiments. Analysis of the protein profile comparing long-term and re-isolated cultures indicated 62 significant spots, from which 27 proteins could be identified in the Acanthamoeba proteome database. Five of them (Serpin, Carboxypeptidase A1, Hypothetical protein, Calponin domain-containing protein, aldo/keto reductase) were exclusively found in the re-isolated trophozoites. Our analysis also revealed that a concerted modulation of several biochemical pathways is triggered when A. castellanii switches from a free-living style to a parasitic mode, including energetic metabolism, proteolytic activity, control of gene expression, protein degradation and methylation of DNA, which may be also involved in gain of virulence in an animal model of AK.

Calponin-Like Protein from Mussel Smooth Muscle Is a Competitive Inhibitor of Actomyosin ATPase

The goal of this work was to elucidate the mechanism of inhibition of the actin-activated ATPase of myosin subfragment-1 (S1) by the calponin-like protein from mussel bivalve muscle. The calponin-like protein (Cap) is a 40-kDa actin-binding protein from the bivalve muscle of the mussel Crenomytilus grayanus. Kinetic parameters Vmax and KATPase of actomyosin ATPase in the absence and the presence of Cap were determined to investigate the mechanism of inhibition. It was found that Cap mainly causes increase in KATPase value and to a lesser extent the decrease in Vmax, which indicates that it is most likely a competitive inhibitor of actomyosin ATPase. Analysis of Vmax and KATPase parameters in the presence of tropomyosin revealed that the latter is a noncompetitive inhibitor of the actomyosin ATPase.

TGFβ2 differentially modulates smooth muscle cell proliferation and migration in electrospun gelatin-fibrinogen constructs

A main goal of tissue engineering is the development of scaffolds that replace, restore and improve injured tissue. These scaffolds have to mimic natural tissue, constituted by an extracellular matrix (ECM) support, cells attached to the ECM, and signaling molecules such as growth factors that regulate cell function. In this study we created electrospun flat sheet scaffolds using different compositions of gelatin and fibrinogen. Smooth muscle cells (SMCs) were seeded on the scaffolds, and proliferation and infiltration were evaluated. Additionally, different concentrations of Transforming Growth Factor-beta2 (TGFβ2) were added to the medium with the aim of elucidating its effect on cell proliferation, migration and collagen production. Our results demonstrated that a scaffold with a composition of 80% gelatin-20% fibrinogen is suitable for tissue engineering applications since it promotes cell growth and migration. The addition of TGFβ2 at low concentrations (≤ 1 ng/ml) to the culture medium resulted in an increase in SMC proliferation and scaffold infiltration, and in the reduction of collagen production. In contrast, TGFβ2 at concentrations >1 ng/ml inhibited cell proliferation and migration while stimulating collagen production. According to our results TGFβ2 concentration has a differential effect on SMC function and thus can be used as a biochemical modulator that can be beneficial for tissue engineering applications.

Proteomics indicators of the rapidly shifting physiology from whole mountain pine beetle, Dendroctonus ponderosae (Coleoptera: Curculionidae), adults during early host colonization

We developed proteome profiles for host colonizing mountain pine beetle adults, Dendroctonus ponderosae Hopkins (Coleoptera: Curculionidae). Adult insects were fed in pairs on fresh host lodgepole pine, Pinus contorta Dougl. ex Loud, phloem tissue. The proteomes of fed individuals were monitored using iTRAQ and compared to those of starved beetles, revealing 757 and 739 expressed proteins in females and males, respectively, for which quantitative information was obtained. Overall functional category distributions were similar for males and females, with the majority of proteins falling under carbohydrate metabolism (glycolysis, gluconeogenesis, citric acid cycle), structure (cuticle, muscle, cytoskeleton), and protein and amino acid metabolism. Females had 23 proteins with levels that changed significantly with feeding (p<0.05, FDR<0.20), including chaperones and enzymes required for vitellogenesis. In males, levels of 29 proteins changed significantly with feeding (p<0.05, FDR<0.20), including chaperones as well as motor proteins. Only two proteins, both chaperones, exhibited a significant change in both females and males with feeding. Proteins with differential accumulation patterns in females exhibited higher fold changes with feeding than did those in males. This difference may be due to major and rapid physiological changes occurring in females upon finding a host tree during the physiological shift from dispersal to reproduction. The significant accumulation of chaperone proteins, a cytochrome P450, and a glutathione S-transferase, indicate secondary metabolite-induced stress physiology related to chemical detoxification during early host colonization. The females' activation of vitellogenin only after encountering a host indicates deliberate partitioning of resources and a balancing of the needs of dispersal and reproduction.

A 24-48 h fed Amblyomma americanum tick saliva immuno-proteome

BACKGROUND

Multiple tick saliva proteins, the majority of which are unknown, confer tick resistance in repeatedly infested animals. The objective of this study was to identify the 24-48 h fed Amblyomma americanum tick saliva immuno-proteome. The 24-48 h tick-feeding phase is critical to tick parasitism as it precedes important events in tick biology, blood meal feeding and disease agent transmission. Fed male, 24 and 96 h fed female phage display cDNA expression libraries were biopanned using rabbit antibodies to 24 and 48 h fed A. americanum female tick saliva proteins. Biopanned immuno-cDNA libraries were subjected to next generation sequencing, de novo assembly, and bioinformatic analysis.

RESULTS

More than 800 transcripts that code for 24-48 h fed A. americanum immuno-proteins are described. Of the 895 immuno-proteins, 52% (464/895) were provisionally identified based on matches in GenBank. Of these, ~19% (86/464) show high level of identity to other tick hypothetical proteins, and the rest include putative proteases (serine, cysteine, leukotriene A-4 hydrolase, carboxypeptidases, and metalloproteases), protease inhibitors (serine and cysteine protease inhibitors, tick carboxypeptidase inhibitor), and transporters and/or ligand binding proteins (histamine binding/lipocalin, fatty acid binding, calreticulin, hemelipoprotein, IgG binding protein, ferritin, insulin-like growth factor binding proteins, and evasin). Others include enzymes (glutathione transferase, cytochrome oxidase, protein disulfide isomerase), ribosomal proteins, and those of miscellaneous functions (histamine release factor, selenoproteins, tetraspanin, defensin, heat shock proteins).

CONCLUSIONS

Data here demonstrate that A. americanum secretes a complex cocktail of immunogenic tick saliva proteins during the first 24-48 h of feeding. Of significance, previously validated immunogenic tick saliva proteins including AV422 protein, calreticulin, histamine release factor, histamine binding/lipocalins, selenoproteins, and paramyosin were identified in this screen, supporting the specificity of the approach in this study. While descriptive, this study opens opportunities for in-depth tick feeding physiology studies.

Isolation and culture of smooth muscle cells from human acute type A aortic dissection

BACKGROUND

Acute type A aortic dissection (TAAD) is a life-threatening vascular disease. Smooth muscle cells (SMCs) are the main composition of aortic media and dysfunction of SMCs may lead to acute TAAD. The aim of this work was to investigate whether the SMCs of acute TAAD could be isolated and cultured for further research.

METHODS

TAAD tissues were obtained from acute TAAD patients who underwent emergent surgical treatment. A simple and economical technique of collagenase digestion method was used to isolate and culture human SMCs. Confocal laser scanning microscopy was applied to identify SMC phenotypes. Purity of isolated and cultured SMCs was analyzed with flow cytometry and fluorescence microscopy respectively.

RESULTS

The purity of isolated SMCs was 78.2%, including α-smooth muscle cell actin positive 13.9%, calponin positive 35.0% and double positive 29.3%. For cultured SMCs, abundant expression of α-smooth muscle cell actin was observed universally under fluorescence microscope. Confocal laser scanning microscope testified that cultured cells were double positive of α-smooth muscle actin and calponin.

CONCLUSIONS

This is the first report of successful culture of SMCs isolated from human acute TAAD tissues. Living human SMCs of acute TAAD provides us with a new method for studying formation of acute TAAD.

Thrombopoietin improved ventricular function and regulated remodeling genes in a rat model of myocardial infarction

BACKGROUND

Thrombopoietin (TPO) protects against heart damages by doxorubicin-induced cardiomyopathy in animal models. We aimed to investigate the therapeutic efficacy of TPO for treatment of myocardial infarction (MI) in a rat model and explored the mechanisms in terms of the genome-wide transcriptional profile, TPO downstream protein signals, and bone marrow endothelial progenitor cells (EPCs).

METHODS

Sprague-Dawley rats were divided into 3 groups: Sham-operated, MI (permanent ligation of the left coronary artery) and MI+TPO. Three doses of TPO were administered weekly for 2 weeks, and outcomes were assessed at 4 or 8 weeks post-injury.

RESULTS AND CONCLUSIONS

TPO treatment significantly improved left ventricular function, hemodynamic parameters, myocardium morphology, neovascularization and infarct size. MI damage upregulated a large cohort of gene expressions in the infarct border zone, including those functioned in cytoskeleton organization, vascular and matrix remodeling, muscle development, cell cycling and ion transport. TPO treatment significantly reversed these modulations. While phosphorylation of janus kinase 2 (JAK2), signal transducer and activator of transcription 3 (STAT3) and protein kinase B (AKT) was modified in MI animals, TPO treatment regulated phosphorylation of STAT3 and extracellular signal-regulated kinases (ERK), and bone morphogenetic protein 1 (BMP1) protein level. TPO also increased EPC colonies in the bone marrow of MI animals. Our data showed that TPO alleviated damages of heart tissues from MI insults, possibly mediated by multi-factorial mechanisms including suppression of over-reacted ventricular remodeling, regulation of TPO downstream signals and mobilization of endothelial progenitor cells. TPO could be developed for treatment of cardiac damages.

Evaluating smooth muscle cells from CaCl2-induced rat aortal expansions as a surrogate culture model for study of elastogenic induction of human aneurysmal cells

Regression of abdominal aortic aneurysms (AAAs) via regeneration of new elastic matrix is constrained by poor elastin synthesis by adult vascular cells and absence of methods to stimulate the same. We recently showed hyaluronan oligomers (HA-o) and TGF-β1 (termed elastogenic factors) to enhance elastin synthesis and matrix formation by healthy rat aortic smooth muscle cells (RASMCs). We also determined that these factors could likewise elastogenically induce aneurysmal RASMCs isolated from periadventitial CaCl(2)-injury induced rat AAAs (aRASMCs). However, the factor doses should be increased for these diseased cell types, as even when induced, elastic matrix amounts are roughly one order of magnitude lower than those produced by healthy RASMCs. We presently investigate the dose-specific elastogenic effects of HA-o (0-20  μg/mL) and TGF-β1 (0-10  ng/mL) factors on aRASMCs and compare their phenotype and elastogenic responses to those of human AAA-derived SMCs (aHASMCs); we seek to determine whether aRASMCs are appropriate surrogate cell types to study in the context of inducing elastic matrix regeneration within human AAAs. The periadventitial CaCl(2)-injury model of AAAs exhibits many of the pathological characteristics of human AAAs, including similarities in terms of decreased SMC contractile activity, enhanced proliferation, and reduced elastogenic capacity of aneurysmal SMCs (relative to healthy SMCs) when isolated and expanded in culture. Both aRASMCs and aHASMCs can be elastogenically stimulated by HA-o and TGF-β1 and show broadly similar trends in their dose-specific responses to these factors. However, compared with aHASMCs, aRASMCs appear to be far less elastogenically inducible. This may be due to differences in maturity of the AAAs studied, with the CaCl(2)-injury induced aortal expansion barely qualifying as an aneurysm and the human AAA representing a more well-developed condition. Further study of SMCs from stage-matched CaCl(2)-injury induced rat aortal expansions and human AAAs will be necessary to more rigorously evaluate their basal and induced elastogenic responses.

The effects of combined cyclic stretch and pressure on the aortic valve interstitial cell phenotype

Aortic valve interstitial cells (VIC) can exhibit phenotypic characteristics of fibroblasts, myofibroblasts, and smooth muscle cells. Others have proposed that valve cells become activated and exhibit myofibroblast or fibroblast characteristics during disease initiation and progression; however, the cues that modulate this phenotypic change remain unclear. We hypothesize that the mechanical forces experienced by the valve play a role in regulating the native phenotype of the valve and that altered mechanical forces result in an activated phenotype. Using a novel ex vivo cyclic stretch and pressure bioreactor, we subjected porcine aortic valve (AV) leaflets to combinations of normal and pathological stretch and pressure magnitudes. The myofibroblast markers α-SMA and Vimentin, along with the smooth muscle markers Calponin and Caldesmon, were analyzed using immunohistochemistry and immunoblotting. Tissue structure was analyzed using Movat's pentachrome staining. We report that pathological stretch and pressure inhibited the contractile and possibly myofibroblast phenotypes as indicated by downregulation of the proteins α-SMA, Vimentin, and Calponin. In particular, Calponin downregulation implies depolymerization of actin filaments and possible conversion to a more synthetic (non-contractile) phenotype. This agreed well with the increase in spongiosa and fibrosa thickness observed under elevated pressure and stretch that are typically indicative of increased matrix synthesis. Our study therefore demonstrates how cyclic stretch and pressure may possibly act together to modulate the AVIC phenotype.

Elastogenic inductability of smooth muscle cells from a rat model of late stage abdominal aortic aneurysms

Although abdominal aortic aneurysms (AAA) can be potentially stabilized by inhibiting inflammatory cell recruitment and their release of proteolytic enzymes, active AAA regression is not possible without regeneration of new elastic matrix structures. Unfortunately, postneonatal vascular smooth muscle cells (SMCs), healthy, and likely more so, diseased cells, poorly synthesize or remodel elastic fibers, impeding any effort directed at regenerative AAA treatment. Previously, we determined the eleastogenic benefits of oligomers (HA-o; 4-6 mers) of the glycosaminoglycan, hyaluronan (HA) and transforming growth factor-β1 (TGF-β1) to healthy SMCs. Since AAAs are often diagnosed only late in development when matrix disruption is severe, we now determine if elastogenic upregulation of SMCs from late-stage AAAs (>100% diameter increase) is possible. AAAs were induced by perfusion of rat infrarenal aortae with porcine pancreatic elastase. Elastic matrix degradation, vessel expansion (∼120%), inflammatory cell infiltration, and enhanced activity of matrix-metalloproteases (MMPs) 2 and 9 resulted, paralleling human AAAs. Aneurysmal SMCs (EaRASMCs) maintained a diseased phenotype in 2D cell culture and exhibited patterns of gene expression different from healthy rat aortic SMCs (RASMCs). Relative to passage-matched healthy RASMCs, unstimulated EaRASMCs produced far less tropoelastin and matrix elastin. Exogenous TGF-β and HA-o (termed "factors") significantly decreased EaRASMC proliferation and enhanced tropoelastin synthesis, though only at the highest provided dose combination (20 mg/mL of HA-o, 10 ng/mL of TGF-β); despite such enhancement, tropoelastin amounts were only ∼40% of amounts synthesized by healthy RASMC cultures. Differently, elastic matrix synthesis was enhanced beyond amounts synthesized by healthy RASMCs (112%), even at lower doses of factors (2 mg/mL of HA-o and 5 ng/mL of TGF-β). The factors also enhanced elastic fiber deposition over untreated EaRASMC cultures and restored several genes whose expression was altered in EaRASMC cultures back to levels expressed by healthy RASMCs. However, the activity of MMPs 2 and 9 generated by EaRASMC cultures was unaffected by the factors/factor dose. The study confirms that SMCs from advanced AAAs can be elastogenically induced, although much higher doses of elastogenic factors are required for induction relative to healthy SMCs. Also, the factors do not appear to inhibit MMP activity, vital to preserve existing elastic matrix structures that serve as nucleation sites for new elastic fiber deposition. Thus, to enhance net accumulation of newly regenerated elastic matrix, toward possibly regressing AAAs, codelivery of MMP inhibitors may be necessitated.

Isolation, culture, and characterization of smooth muscle cells from human intracranial aneurysms

BACKGROUND

Smooth muscle cells (SMCs) play a critical role in the vascular wall and also participate in vascular repair mechanisms. Dysfunction of SMCs may also contribute to the formation of intracranial aneurysms (IAs) causing subarachnoid hemorrhage. Our aim was to investigate the possibility of using cultured SMCs as an in vitro model for the study of aneurysmal SMCs.

METHODS

IA tissue was obtained during microsurgical ligation of IAs. By using the explant method, cell cultures were established from the aneurysmal tissue. The phenotype of cultured cells from passage to passage was studied using immunoperoxidase staining and Western blotting. Eight cell lines could be established from 29 IA samples. Four lines showing most rigorous growth were investigated more thoroughly.

RESULTS

Abundant expression of SMC markers, α-smooth muscle cell actin and calponin, as well as of prolyl-4-hydroxylases, a key enzyme family in the synthesis of collagens, was observed in all of them. Aneurysmal SMCs in culture maintained their phenotype and SMC characteristics through the early passages of growth.

CONCLUSION

This is the first documented successful culture of SMCs from human IAs. An access to living human cells of aneurysmal origin gives us a new tool in our research of the formation, growth, and rupture of IAs.

Calponin gene expression in Chironomus riparius exposed to di(2-ethylhexyl) phthalate

Di(2-ethylhexyl) phthalate, which is a ubiquitous environmental contaminant because of its extensive use as a plasticizer, is a potential nongenotoxic carcinogen. To assess the effects of DEHP exposure on the cytoskeleton of Chironomus, we characterized full-length cDNA sequences of the calponin gene from Chironomus riparius. The expression of the calponin gene was analyzed during different life-history stages and under various DEHP concentrations for short and long periods. A phylogenetic investigation was then conducted to compare different orders of insects using sequence database analysis. The complete cDNA sequence of the calponin gene was found to be 555 bp in length. The results of phylogenetic analysis revealed that C. riparius calponin is most closely related to that of beetles. The basal level of calponin mRNA was highly expressed during different life-history stages. In addition, calponin gene expression decreased within 1 h of short-term exposure to DEHP, regardless of the concentration. We also investigated expression of the calponin gene following long-term exposure (10 days). Calponin gene expression was found to decrease significantly in C. riparius that were exposed to a low dose of DEHP, and this response was found to occur in a dose-dependent manner. Taken together, these results suggest that DEHP affects the functions of Ca(2+) binding muscle proteins such as calponin in Chironomus species.

Calponin control of cerebrovascular reactivity: therapeutic implications in brain trauma

Calponin (Cp) is an actin-binding protein first characterized in chicken gizzard smooth muscle (SM). This review discusses the role of Cp in mediating SM contraction, the biochemical process by which Cp facilitates SM contraction and the function of Cp in the brain. Recent work on the role of Cp in pathological states with emphasis on traumatic brain injury is also discussed. Based on past and present data, the case is presented for targeting Cp for novel genetic and pharmacological therapies aimed at improving outcome following traumatic brain injury (TBI).

HIV-1-infected astrocytes and the microglial proteome

The human immunodeficiency virus (HIV) invades the central nervous system early after viral exposure but causes progressive cognitive, behavior, and motor impairments years later with the onset of immune deficiency. Although in the brain, HIV preferentially replicates productively in cells of mononuclear phagocyte (MP; blood borne macrophage and microglia), astrocytes also can be infected, at low and variable frequency, particularly in patients with encephalitis. Among their many functions, astrocytes network with microglia to provide the first line of defense against microbial infection; however, very little is known about astrocytes' consequences on MP. Here, we addressed this question using co-culture systems of HIV-infected mouse astrocytes and microglia. Pseudotyped vesicular stomatis virus/HIV was used to circumvent the absence of viral receptors and ensure cell genotypic uniformity for studies of intercellular communication. The study demonstrated that infected astrocytes show modest changes in protein elements compared to uninfected cells. In contrast, infected astrocytes induce robust changes in the proteome of HIV-1-infected microglia. Accelerated cell death and redox proteins, among others, were produced in abundance. The observations confirmed the potential of astrocytes to influence the neuropathogenesis of HIV-1 infection by specifically altering the neurotoxic potential of infected microglia and regulating viral maturation.

Calponin is expressed by subpopulations of connective tissue cells but not olfactory ensheathing cells in the neonatal olfactory mucosa

BACKGROUND

Debate has been ongoing on the relative merits of olfactory ensheathing cells (OECs) and Schwann cells as candidates for transplant-mediate repair of CNS lesions. Both glial cells exhibit similar molecular and cellular properties and to date there has been no antigenic marker identified that can clearly distinguish the two cell types. This inability to distinguish between the two cells types prevents confirmation of a controversial statement that cultures of OECs are contaminated with Schwann cells. Recently, proteomic analysis of foetal OECs and adult Schwann cells identified an actin-binding protein, calponin, as a specific marker for OECs. However, at the same time a recent report suggested that adult OECs do not express calponin. It was not clear if this discrepancy was due to methodology, as cells had to be treated with proteinase K to maximize calponin staining or developmental differences with only foetal/neonatal OECs expressing calponin. For this reason we have examined calponin expression in the peripheral olfactory system of embryonic and neonatal rats in vivo and from cells in vitro to assess if calponin is expressed in a developmental manner.

RESULTS

In this study we show that: i) proteinase K pretreatment had no effect on calponin staining in both OECs and Schwann cells. ii) calponin immunoreactivity was not expressed by embryonic or neonatal OECs in vitro and in vivo although connective tissue from the olfactory mucosa was strongly positive in neonatal rats but not embryonic rats, iii) calponin expression in the olfactory mucosa was heterogeneous, defining subpopulations of connective tissue cells iv) using functional confrontation assays between OECs or Schwann cells with astrocytes, calponin was expressed heterogeneously by astrocytes.

CONCLUSION

It is concluded that calponin is heterogeneously expressed by neonatal mucosal connective tissue but not expressed by neonatal OECs, embryonic OECs, and neonatal Schwann cells. Furthermore, we propose that calponin is not a specific marker for OECs generated from any developmental age.

Calponins: adaptable modular regulators of the actin cytoskeleton

Over 20 years ago Katsuhito Takahashi isolated a heat stable, calmodulin and actin binding protein from chicken gizzard smooth muscle. Considered initially as a mainly structural component of the vertebrate smooth muscle contractile machinery, the 34-kDa calcium- and calmodulin-binding troponin T-like protein, calponin quickly appeared to also be involved in a number of regulatory and signal transduction events in the actin cytoskeleton. Calponins regulate actomyosin contraction, and reduce metastatic cell motility and tissue invasion. From these various cellular functions the biological role of calponin is now slowly emerging, namely that of an actin filament-stabilizing molecule that contributes to physiological thin filament turnover rates in different cell types.

Calponin is expressed by fibroblasts and meningeal cells but not olfactory ensheathing cells in the adult peripheral olfactory system

Olfactory ensheathing cells (OECs), the principal glial cells of the peripheral olfactory system, have many phenotypic similarities with Schwann cells of the peripheral nervous system. This makes reliably distinguishing these two cells types difficult, especially following transplantation into areas of injury in the central nervous system. In an attempt to identify markers by which these two cells types can be distinguished, a recent proteomic analysis of fetal OECs and adult Schwann cells identified the actin-binding protein calponin as a potential marker expressed by OECs but not Schwann cells. Since many studies designed with the translational goal of autologous transplantation in mind have used adult OECs, this study examined the expression of calponin by adult OECs, both in vivo within the peripheral olfactory system and in vitro. Calponin colocalized with strongly fibronectin positive fibroblasts in the olfactory mucosa (OM) and meningeal cells in the olfactory bulb (OB) but not with S100beta or neuropeptide-Y positive OECs. In tissue culture, calponin was strongly expressed by fibronectin-expressing fibroblasts from OM, sciatic nerve and skin and by meningeal cells from the OB, but not by p75(NTR)- and S100beta-expressing OECs. These data, supported by Western blotting, indicate that calponin can not be used to distinguish adult OECs and Schwann cells.

Calponin binds G-actin and F-actin with similar affinity

Calponins are actin-binding proteins that are implicated in the regulation of actomyosin. Calponin binds filamentous actin (F-actin) through two distinct sites ABS1 and ABS2, with an affinity in the low micromolar range. We report that smooth muscle calponin binds monomeric actin with a similar affinity (K(d) of 0.15 microM). We show that the arrangement of binding is similar to that of F-actin by a number of criteria, most notably that the distance between Cys273 on calponin and Cys374 of actin is 29A when measured by fluorescent resonance energy transfer, the same distance as previously reported for F-actin.

Myoepithelial cell markers in salivary gland neoplasms

We compared the immunoexpression of 5 myoepithelial cell (MEC) markers (alpha-smooth-muscle actin, calponin, h-caldesmon, vimentin, and S-100-protein) using 16 pleomorphic adenomas (PA), 15 adenoid cystic carcinomas (ACC), and 3 epithelial-myoepithelial carcinomas (EMC) of salivary glands. The alpha-smooth-muscle actin was useful for identification of MECs, especially in cribriform and tubular ACC, followed by EMC. Calponin was similar to alpha-smooth-muscle actin, except for polygonal and plasmacytoid cells of PA and for solid ACC, which showed alpha-smooth-muscle actin negative and calponin positive. H-caldesmon was negative. Vimentin immunostained all MEC types, and was negative in luminal cells. S-100 protein was expressed both in the nuclei and cytoplasm of MECs and luminal cells, especially in PA. The best way to identify MEC is using alpha-smooth-muscle actin or calponin, plus vimentin, since in tumors MECs are hardly ever fully differentiated.

Study of the alteration of gene expression in adipose tissue of diet-induced obese mice by microarray and reverse transcription-polymerase chain reaction analyses

In the present study we developed a model of diet-induced obesity (DIO) in male C57 BL/6J mice using an 8-wk high fat diet. This model should better reflect the physiology of the majority of the human obese patients than mouse genetic models of obesity with defects in leptin or leptin signaling. At the end of the diet, DIO mice displayed an increased weight (20%) and higher leptin, insulin, glucose, and corticosterone plasma levels compared with mice fed a standard diet during the same period. Moreover, they became resistant to the central effect of peripheral administration of leptin. Oligonucleotide microarray studies were conducted in adipose tissue. They showed that a great number of genes are differentially expressed. The majority of these genes (69%) are down-regulated in DIO mice. Among those are genes encoding enzymes of the lipid metabolism or markers of adipocyte differentiation, enzymes involved in detoxification processes, as well as structural components of the cytoskeleton. Some other groups of genes displayed increased expression, such as those encoding inflammatory markers. The results of the microarray analysis were confirmed by semiquantitative RT-PCR studies run on a selected number of genes that were differentially expressed or not modified.

Expression of muscle-related genes and two MyoD genes during amphioxus notochord development

The notochord is one of the diagnostic features of the phylum Chordata. Despite the similarities in the early morphogenetic patterns of the notochords of various chordates, they are strikingly distinct from one another at the histological level. The amphioxus notochord is one example of an evolutionary novelty because it is made up of muscle cells. Our previous expressed sequence tag analysis, targeting messenger RNAs expressed in the adult amphioxus notochord, demonstrated that many muscle-related genes are expressed there. To characterize amphioxus notochord cells and to gain insights into the myogenic program in the notochord, we determined the spatial and temporal expre-ssion patterns of these muscle-related genes during amphioxus development. We found that BbNA1 (notochord actin), Amphi-Trop I (troponin I), Amphi-TPmyosin (tropo-myosin), Amphi-MHC2 (myosin heavy chain), Amphi-nMRLC (notochord-specific myosin regulatory light chain), Amphi-nTitin/MLCK (notochord-specific titin/myosin light chain kinase), Amphi-MLP/CRP3 (muscle LIM protein), and Amphi-nCalponin (notochord-specific calponin) are expres-sed with characteristic patterns in notochord cells, including the central cells, dorsally located cells, and ventrally located cells, suggesting that each notochord cell has a unique molecular architecture that may reflect its function. In addition, we characterized two MyoD genes (Amphi-MyoD1 and Amphi-MyoD2) to gain insight into the genetic circuitry governing the formation of the notochord muscle. One of the MyoD genes (Amphi-MyoD2) is expressed in the central notochord cells, and the coexistence of Amphi-MyoD2 transcripts along with the Amphi-MLP/CRP3 transcripts implies the participation of Amphi-MyoD2 in the myogenic program in the notochord muscle.

Immunocytochemistry of myoepithelial cells in the salivary glands

MECs are distributed on the basal aspect of the intercalated duct and acinus of human and rat salivary glands. However, they do not occur in the acinus of rat parotid glands, and sometimes occur in the striated duct of human salivary glands. MECs, as the name implies, have structural features of both epithelial and smooth muscle cells. They contract by autonomic nervous stimulation, and are thought to assist the secretion by compressing and/or reinforcing the underlying parenchyma. MECs can be best observed by immunocytochemistry. There are three types of immunocytochemical markers of MECs in salivary glands. The first type includes smooth muscle protein markers such as alpha-SMA, SMMHC, h-caldesmon and basic calponin, and these are expressed by MECs and the mesenchymal vasculature. The second type is expressed by MECs and the duct cells and includes keratins 14, 5 and 17, alpha 1 beta 1 integrin, and metallothionein. Vimentin is the third type and, in addition to MECs, is expressed by the mesenchymal cells and some duct cells. The same three types of markers are used for studying the developing gland. Development of MECs starts after the establishment of an extensively branched system of cellular cords each of which terminates as a spherical cell mass, a terminal bud. The pluripotent stem cell generates the acinar progenitor in the terminal bud and the ductal progenitor in the cellular cord. The acinar progenitor differentiates into MECs, acinar cells and intercalated duct cells, whereas the ductal progenitor differentiates into the striated and excretory duct cells. Both in the terminal bud and in the cellular cord, the immediate precursors of all types of the epithelial cells appear to express vimentin. The first identifiable MECs are seen at the periphery of the terminal bud or the immature acinus (the direct progeny of the terminal bud) as somewhat flattened cells with a single cilium projecting toward them. They express vimentin and later alpha-SMA and basic calponin. At the next developmental stage, MECs acquire cytoplasmic microfilaments and plasmalemmal caveolae but not as much as in the mature cell. They express SMMHC and, inconsistently, K14. This protein is consistently expressed in the mature cell. K14 is expressed by duct cells, and vimentin is expressed by both mesenchymal and epithelial cells. After development, the acinar progenitor and the ductal progenitor appear to reside in the acinus/intercalated duct and the larger ducts, respectively, and to contribute to the tissue homeostasis. Under unusual conditions such as massive parenchymal destruction, the acinar progenitor contributes to the maintenance of the larger ducts that result in the occurrence of striated ducts with MECs. The acinar progenitor is the origin of salivary gland tumors containing MECs. MECs in salivary gland tumors are best identified by immunocytochemistry for alpha-SMA. There are significant numbers of cells related to luminal tumor cells in the non-luminal tumor cells that have been believed to be neoplastic MECs.

Random walks with thin filaments: application of in vitro motility assay to the study of actomyosin regulation

The in vitro motility devised by Kron and Spudich (Kron and Spudich, 1986; Kron et al., 1991) has proved a very valuable technique for studying the motor properties of myosin of all kinds but it is equally useful for the study of the thin filaments of muscle and their regulation. The movement of a population of thin filaments over immobilised myosin appears to be random but it does in fact yield a large amount of information about contractility and its regulation. The key to extracting useful information from in vitro motility assay experiments is the logical and comprehensive analysis of filament movements.

Adhesion, migration, transcriptional, interferon-inducible, and other signaling molecules newly implicated in cancer susceptibility and resistance of JB6 cells by cDNA microarray analyses

Relative expression levels of 9500 genes were determined by cDNA microarray analyses in mouse skin JB6 cells susceptible (P+) and resistant (P-) to 12-O-tetradecanoyl phorbol-13 acetate (TPA)-induced neoplastic transformation. Seventy-four genes in 6 functional classes were differentially expressed: (I) extracellular matrix (ECM) and basement membrane (BM) proteins (20 genes). P+ cells express higher levels than P- cells of several collagens and proteases, and lower levels of protease inhibitors. Multiple genes encoding adhesion molecules are expressed preferentially in P- cells, including six genes implicated in axon guidance and adhesion. (II) Cytoskeletal proteins (13 genes). These include actin isoforms and regulatory proteins, almost all preferentially expressed in P- cells. (III) Signal transduction proteins (12 genes). Among these are Ras-GTPase activating protein (Ras-GAP), the deleted in oral cancer-1 and SLIT2 tumor suppressors, and connexin 43 (Cx43) gap junctional protein, all expressed preferentially in P- cells. (IV) Interferon-inducible proteins (3 genes). These include interferon-inducible protein (IFI)-16, an Sp1 transcriptional regulator expressed preferentially in P- cells. (V) Other transcription factors (4 genes). Paired related homeobox gene 2 (Prx2)/S8 homeobox, and retinoic acid (RA)-regulated nur77 and cellular retinoic acid-binding protein II (CRABPII) transcription factors are expressed preferentially in P- cells. The RIN-ZF Sp-transcriptional suppressor exhibits preferential P+ expression. (VI) Genes of unknown functions (22 sequences). Numerous mesenchymal markers are expressed in both cell types. Data for multiple genes were confirmed by real-time PCR. Overall, 26 genes were newly implicated in cancer. Detailed analyses of the functions of the genes and their interrelationships provided converging evidence for their possible roles in implementing genetic programs mediating cancer susceptibility and resistance. These results, in conjunction with cell wounding and phalloidin staining data, indicated that concerted genetic programs were implemented that were conducive to cell adhesion and tumor suppression in P- cells and that favored matrix turnover, cell motility, and abrogation of tumor suppression in P+ cells. Such genetic programs may in part be orchestrated by Sp-, RA-, and Hox-transcriptional regulatory pathways implicated in this study.

Angiotensin II modulates calponin gene expression in rat vascular smooth muscle cells in vivo

OBJECTIVES

It has been shown that angiotensin II (Ang II) induces the expression of calponin, a 34 kD actin-binding protein, in vascular smooth muscle cells in vitro. The aim of this study was to investigate whether Ang II can modulate calponin gene expression in rat aorta in vivo.

DESIGN

Aortic calponin gene expression was studied after chronic exogenous Ang II administration and in Goldblatt hypertension.

METHODS

To investigate the effect of Ang II administration, Sprague Dawley rats were treated for 6 days with a continuous infusion of Ang II (200 ng/kg per min) or saline by osmotic minipumps. The effect of endogenous Ang II on aortic calponin mRNA expression was studied in Goldblatt hypertensive rats with (2K1C model), or without (1K1C model) activation of the renin-angiotensin system. In particular, calponin gene expression in 2K1C rats was studied both at 1 week (2K1C-HR, high renin) and 4 weeks after the onset of hypertension, when plasma renin activity (PRA) was returned to normal values (2K1C-NR, normal renin). Systolic blood pressure (SBP) was measured twice a week. At the end of the experimental period, PRA was measured by radioimmunoassay, and aortic calponin gene expression was measured by Northern hybridization.

RESULTS

SBP was significantly higher (P < 0.01), whereas PRA was suppressed (P < 0.01), in Ang II versus saline-treated rats. Northern hybridization showed that the aortic calponin gene expression significantly increased (2.5-fold) in Ang II-treated rats (P = 0.01). In Goldblatt hypertensive rats, SBP was significantly higher in 2K1C-HR (P < 0.01), 2K1C-NR (P < 0.01) and 1K1C (P < 0.01) rats compared with the corresponding sham-treated rats. Activation of the renin-angiotensin system was present only in 2K1C-HR rats (P < 0.01), and Northern analysis showed that aortic calponin mRNA expression was significantly increased (2.2-fold) in this group of rats only (P < 0.01).

CONCLUSIONS

Our data demonstrate that both exogenous and endogenous Ang II increase calponin gene expression in aortic smooth muscle cells, independently of the hemodynamic effect of Ang II.

Angiotensin II increases calponin expression in cultured rat vascular smooth muscle cells

Angiotensin II (Ang II) action on vascular smooth muscle cells is not limited to contraction, but includes long term effects such as hypertrophy and hyperplasia. This implies a complex pattern of gene modulation, which remains largely unknown. We used the mRNA differential display method to screen rat aortic smooth muscle cells cultured with or without Ang II. We demonstrated that Ang II induces the expression of calponin, a 34-kD protein, which has been shown to regulate smooth muscle cell contraction and to be a marker of smooth muscle cell differentiation. We demonstrated this induction both at gene and protein level in vascular smooth muscle cells. Calponin mRNA was dose-dependently induced by Ang II, with an effect still evident at 5 x 10(-9)M, and it did not require active protein synthesis, since cycloheximide treatment did not suppress this induction. Calponin gene expression was maximal at 3 h, while protein expression was maximal at 8 h. Calponin expression was completely abolished by the AT1 receptor antagonist, losartan, at 1 x 10(-6)M. Our data demonstrate that Ang II increases calponin gene expression and protein level in rat aortic smooth muscle cells in vitro.

Actin and the smooth muscle regulatory proteins: a structural perspective

The structural details of the smooth muscle acto-myosin interaction and its functional implications have been much discussed in recent years, however other, smooth muscle specific, actin-binding proteins have received much less attention. With increasing technical advances in structural biology a great deal of structural information is now coming to light, information that can provide useful insight into the mechanism of action for many important nonmotor actin-binding proteins. The purpose of the review is to instill the current knowledge on the structure, and interaction sites on F-actin, of the major, non-motor actin-binding proteins from smooth muscle, proposed to have a role in regulation. In the light of the recent structural studies the probable roles of the various actin-binding proteins will be discussed with particular reference to structure function relationships.

Contraction kinetics of isolated human myometrium during menstrual cycle and pregnancy

OBJECTIVE

To investigate the interaction between actin and myosin in the myometrium by studying the contraction kinetics of isolated samples of human myometrium.

DESIGN

Experimental and observational cross-sectional study.

SETTING

Eppendorf University Hospital, Hamburg.

SAMPLES

Myometrium samples were taken from women in the follicular phase (n = 6) or luteal phase (n = 6) of the menstrual cycle and during pregnancy at term (n = 25).

METHODS

The frequency, extent and rate of force development were determined in spontaneously active myometrial preparations. From a resting force of 2 mN, sustained tonic contractions were induced by K+-depolarisation (124 mM), or by protein kinase C activation (19 x 9 microM indolactam). The steady force was reversibly interrupted by rapid length changes (100 Hz sinus vibrations lasting 1 s, 5% of muscle length). Extent (steady plateau), as well as rate of force increase after cessation of vibrations, were derived from bi-exponential functions fitted to the time course of force recovery.

RESULTS

Frequency of spontaneous contractions was higher in the follicular phase [mean (SD) 18 x 3 contractions/hour (1 x 0)] than in the luteal phase [13 x 4 contractions/hour (8 x 1)] or in pregnancy at term [8 x 8 contractions/hour (7 x 6)]. During indolactam treatment, steady force in pregnancy at term was significantly increased [8 x 8 mN (4 x 0)], compared with the follicular phase [3 x 7 mN (0 x 9)]. Force recovery was distinctly slower in pregnancy at term during indolactam treatment [time constant 99 x 2 s (57 x 9); P < 0 x 005] than during K+-depolarisation [time constant 29 x 1 s (5 x 9)], whereas in the follicular phase the rate of force recovery was faster with indolactam [16 x 8 s (7 x 1)] than with K+ depolarisation [24 x 4 s (5 x 9); P < 0 x 005].

CONCLUSIONS

The responses of human myometrium to contraction stimuli differ according to the reproductive state. Membrane depolarisation causes similar responses in all myometrial strips. In contrast, near term stimulation of protein kinase C generates a large tonic force and slow contraction kinetics, whereas early in the menstrual cycle contraction kinetics are fast.

Localization of calponin binding sites in the structure of 90 kDa heat shock protein (Hsp90)

The structure of rabbit liver Hsp90 was reevaluated by limited trypsinolysis, N-terminal sequencing and determination of the site that is phosphorylated by casein kinase II. Limited proteolysis results in formation of four groups of large peptides with M(r) in the range of 26-41 kDa. Peptides with M(r) 39-41 kDa were represented by large N-terminal and central peptides starting at residue 283 of the alpha-isoform of Hsp90. All sites phosphorylated by casein kinase II were located in the large 39-41 kDa peptides. Peptides with M(r) 26-27 kDa were represented by short N-terminal and central peptides starting at Glu-400 of the alpha-isoform of Hsp90. The data of affinity chromatography and light scattering indicate that smooth muscle calponin interacts with Hsp90. The calponin binding sites are located in the large (37-41 kDa) N-terminal and in a short (26-27 kDa) central peptide starting at Glu-400 of the alpha-isoform of Hsp90. Phosphorylation by casein kinase II up to 2 mol of phosphate per mol of Hsp90 does not affect interaction of Hsp90 with calponin.

The C. elegans cell death specification gene ces-1 encodes a snail family zinc finger protein

The ces-1 and ces-2 genes of C. elegans control the programmed deaths of specific neurons. Genetic evidence suggests that ces-2 functions to kill these neurons by negatively regulating the protective activity of ces-1, ces-2 encodes a protein closely related to the vertebrate PAR family of bZIP transcription factors, and a ces-2/ces-1-like pathway may play a role in regulating programmed cell death in mammalian lymphocytes. Here we show that ces-1 encodes a Snail family zinc finger protein, most similar in sequence to the Drosophila neuronal differentiation protein Scratch. We define an element important for ces-1 regulation and provide evidence that CES-2 can bind to a site within this element and thus may directly repress ces-1 transcription. Our results suggest that a transcriptional cascade controls the deaths of specific cells in C. elegans.

Excitation-contraction coupling in gastrointestinal and other smooth muscles

The main contributors to increases in [Ca2+]i and tension are the entry of Ca2+ through voltage-dependent channels opened by depolarization or during action potential (AP) or slow-wave discharge, and Ca2+ release from store sites in the cell by the action of IP3 or by Ca(2+)-induced Ca(2+)-release (CICR). The entry of Ca2+ during an AP triggers CICR from up to 20 or more subplasmalemmal store sites (seen as hot spots, using fluorescent indicators); Ca2+ waves then spread from these hot spots, which results in a rise in [Ca2+]i throughout the cell. Spontaneous transient releases of store Ca2+, previously detected as spontaneous transient outward currents (STOCs), are seen as sparks when fluorescent indicators are used. Sparks occur at certain preferred locations--frequent discharge sites (FDSs)--and these and hot spots may represent aggregations of sarcoplasmic reticulum scattered throughout the cytoplasm. Activation of receptors for excitatory signal molecules generally depolarizes the cell while it increases the production of IP3 (causing calcium store release) and diacylglycerols (which activate protein kinases). Activation of receptors for inhibitory signal molecules increases the activity of protein kinases through increases in cAMP or cGMP and often hyperpolarizes the cell. Other receptors link to tyrosine kinases, which trigger signal cascades interacting with trimeric G-protein systems.

3-D image reconstruction of reconstituted smooth muscle thin filaments containing calponin: visualization of interactions between F-actin and calponin

Calponin is a putative thin filament regulatory protein of smooth muscle that inhibits actomyosin ATPase in vitro. We have used electron microscopy and three-dimensional reconstruction to elucidate the structural organization of calponin on actin and actin-tropomyosin filaments. Calponin density was clearly delineated in the reconstructions and found to occur peripherally along the long-pitch actin-helix. The main calponin mass was located over sub-domain 2 of actin, and connected axially adjacent actin monomers by binding to the "upper" and "lower" edges of sub-domains 1 of each actin. When the reconstructions were fitted to the atomic model of F-actin, calponin appeared to contact actin near the N terminus and at residues 349 to 352 close to the C terminus of sub-domain 1 on one monomer. It also touched residues 92 to 95 of sub-domain 1 on the axially neighboring actin and continued up the side of this monomer as far as residues 43 to 48 of sub-domain 2. These positions are consensus binding sites for a number of actin-associated proteins and are also near to sites of weak myosin interaction. Calponin did not appear to block strong myosin binding sites on actin. In contrast to the calponin mass which appeared monomeric in reconstructions, tropomyosin formed a continuous strand of added density along F-actin. When added to tropomyosin-containing filaments, calponin caused a shift of tropomyosin away from sub-domain 1 towards sub-domain 3 of actin, exposing strong myosin-binding sites that were previously covered by tropomyosin. This structural effect is unlike that of troponin and therefore inhibition of actomyosin ATPase by calponin and troponin cannot be strictly analogous. The location of calponin would allow it to directly compete or interact with a number of actin-binding proteins.