Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “ACTIN”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 325 records · Page 18
All sourcesNASA NTRSDOE OSTI
NASA NTRS1994

Comparative assessment of the polypeptide profiles from lateral and primary roots of Phaseolus vulgaris L

In Phaseolus vulgaris, primary roots show gravitational sensitivity soon after emerging from the seed. In contrast, lateral roots are agravitropic during early development, and become gravitropic after several cm growth. Primary and lateral root tissues were examined by polyacrylamide gel electrophoresis, coupled with western blotting techniques, to compare proteins which may contribute to the acquisition of gravitational sensitivity. Root tips and zones of cell elongation were compared for each root type, using immunological probes for calmodulin, alpha-actin, alpha-tubulin, and proteins of the plastid envelope. Lateral roots contained qualitatively less calmodulin, and showed a slightly different pattern of actin-related epitope proteins, than did primary root tissues, suggesting that polypeptide differences may contribute to the gravitational sensitivity which these root types express.

Non-NASA Center↗
NASA NTRS2001

Analysis of the myosins encoded in the recently completed Arabidopsis thaliana genome sequence

BACKGROUND: Three types of molecular motors play an important role in the organization, dynamics and transport processes associated with the cytoskeleton. The myosin family of molecular motors move cargo on actin filaments, whereas kinesin and dynein motors move cargo along microtubules. These motors have been highly characterized in non-plant systems and information is becoming available about plant motors. The actin cytoskeleton in plants has been shown to be involved in processes such as transportation, signaling, cell division, cytoplasmic streaming and morphogenesis. The role of myosin in these processes has been established in a few cases but many questions remain to be answered about the number, types and roles of myosins in plants. RESULTS: Using the motor domain of an Arabidopsis myosin we identified 17 myosin sequences in the Arabidopsis genome. Phylogenetic analysis of the Arabidopsis myosins with non-plant and plant myosins revealed that all the Arabidopsis myosins and other plant myosins fall into two groups - class VIII and class XI. These groups contain exclusively plant or algal myosins with no animal or fungal myosins. Exon/intron data suggest that the myosins are highly conserved and that some may be a result of gene duplication. CONCLUSIONS: Plant myosins are unlike myosins from any other organisms except algae. As a percentage of the total gene number, the number of myosins is small overall in Arabidopsis compared with the other sequenced eukaryotic genomes. There are, however, a large number of class XI myosins. The function of each myosin has yet to be determined.

NASA Discipline Plant Biology↗
NASA NTRS2001

Molecular motors and their functions in plants

Molecular motors that hydrolyze ATP and use the derived energy to generate force are involved in a variety of diverse cellular functions. Genetic, biochemical, and cellular localization data have implicated motors in a variety of functions such as vesicle and organelle transport, cytoskeleton dynamics, morphogenesis, polarized growth, cell movements, spindle formation, chromosome movement, nuclear fusion, and signal transduction. In non-plant systems three families of molecular motors (kinesins, dyneins, and myosins) have been well characterized. These motors use microtubules (in the case of kinesines and dyneins) or actin filaments (in the case of myosins) as tracks to transport cargo materials intracellularly. During the last decade tremendous progress has been made in understanding the structure and function of various motors in animals. These studies are yielding interesting insights into the functions of molecular motors and the origin of different families of motors. Furthermore, the paradigm that motors bind cargo and move along cytoskeletal tracks does not explain the functions of some of the motors. Relatively little is known about the molecular motors and their roles in plants. In recent years, by using biochemical, cell biological, molecular, and genetic approaches a few molecular motors have been isolated and characterized from plants. These studies indicate that some of the motors in plants have novel features and regulatory mechanisms. The role of molecular motors in plant cell division, cell expansion, cytoplasmic streaming, cell-to-cell communication, membrane trafficking, and morphogenesis is beginning to be understood. Analyses of the Arabidopsis genome sequence database (51% of genome) with conserved motor domains of kinesin and myosin families indicates the presence of a large number (about 40) of molecular motors and the functions of many of these motors remain to be discovered. It is likely that many more motors with novel regulatory mechanisms that perform plant-specific functions are yet to be discovered. Although the identification of motors in plants, especially in Arabidopsis, is progressing at a rapid pace because of the ongoing plant genome sequencing projects, only a few plant motors have been characterized in any detail. Elucidation of function and regulation of this multitude of motors in a given species is going to be a challenging and exciting area of research in plant cell biology. Structural features of some plant motors suggest calcium, through calmodulin, is likely to play a key role in regulating the function of both microtubule- and actin-based motors in plants.

Non-NASA Center↗
NASA NTRS2000

Plant nuclei can contain extensive grooves and invaginations

Plant cells can exhibit highly complex nuclear organization. Through dye-labeling experiments in untransformed onion epidermal and tobacco culture cells and through the expression of green fluorescent protein targeted to either the nucleus or the lumen of the endoplasmic reticulum/nuclear envelope in these cells, we have visualized deep grooves and invaginations into the large nuclei of these cells. In onion, these structures, which are similar to invaginations seen in some animal cells, form tubular or planelike infoldings of the nuclear envelope. Both grooves and invaginations are stable structures, and both have cytoplasmic cores containing actin bundles that can support cytoplasmic streaming. In dividing tobacco cells, invaginations seem to form during cell division, possibly from strands of the endoplasmic reticulum trapped in the reforming nucleus. The substantial increase in nuclear surface area resulting from these grooves and invaginations, their apparent preference for association with nucleoli, and the presence in them of actin bundles that support vesicle motility suggest that the structures might function both in mRNA export from the nucleus and in protein import from the cytoplasm to the nucleus.

Non-NASA Center↗
NASA NTRS2000

Ca(2+) regulates fluid shear-induced cytoskeletal reorganization and gene expression in osteoblasts

Osteoblasts subjected to fluid shear increase the expression of the early response gene, c-fos, and the inducible isoform of cyclooxygenase, COX-2, two proteins linked to the anabolic response of bone to mechanical stimulation, in vivo. These increases in gene expression are dependent on shear-induced actin stress fiber formation. Here, we demonstrate that MC3T3-E1 osteoblast-like cells respond to shear with a rapid increase in intracellular Ca(2+) concentration ([Ca(2+)](i)) that we postulate is important to subsequent cellular responses to shear. To test this hypothesis, MC3T3-E1 cells were grown on glass slides coated with fibronectin and subjected to laminar fluid flow (12 dyn/cm(2)). Before application of shear, cells were treated with two Ca(2+) channel inhibitors or various blockers of intracellular Ca(2+) release for 0. 5-1 h. Although gadolinium, a mechanosensitive channel blocker, significantly reduced the [Ca(2+)](i) response, neither gadolinium nor nifedipine, an L-type channel Ca(2+) channel blocker, were able to block shear-induced stress fiber formation and increase in c-fos and COX-2 in MC3T3-E1 cells. However, 1, 2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid-AM, an intracellular Ca(2+) chelator, or thapsigargin, which empties intracellular Ca(2+) stores, completely inhibited stress fiber formation and c-fos/COX-2 production in sheared osteoblasts. Neomycin or U-73122 inhibition of phospholipase C, which mediates D-myo-inositol 1,4,5-trisphosphate (IP(3))-induced intracellular Ca(2+) release, also completely suppressed actin reorganization and c-fos/COX-2 production. Pretreatment of MC3T3-E1 cells with U-73343, the inactive isoform of U-73122, did not inhibit these shear-induced responses. These results suggest that IP(3)-mediated intracellular Ca(2+) release is required for modulating flow-induced responses in MC3T3-E1 cells.

Non-NASA Center↗
NASA NTRS1997

Demonstration of mechanical connections between integrins, cytoskeletal filaments, and nucleoplasm that stabilize nuclear structure

We report here that living cells and nuclei are hard-wired such that a mechanical tug on cell surface receptors can immediately change the organization of molecular assemblies in the cytoplasm and nucleus. When integrins were pulled by micromanipulating bound microbeads or micropipettes, cytoskeletal filaments reoriented, nuclei distorted, and nucleoli redistributed along the axis of the applied tension field. These effects were specific for integrins, independent of cortical membrane distortion, and were mediated by direct linkages between the cytoskeleton and nucleus. Actin microfilaments mediated force transfer to the nucleus at low strain; however, tearing of the actin gel resulted with greater distortion. In contrast, intermediate filaments effectively mediated force transfer to the nucleus under both conditions. These filament systems also acted as molecular guy wires to mechanically stiffen the nucleus and anchor it in place, whereas microtubules acted to hold open the intermediate filament lattice and to stabilize the nucleus against lateral compression. Molecular connections between integrins, cytoskeletal filaments, and nuclear scaffolds may therefore provide a discrete path for mechanical signal transfer through cells as well as a mechanism for producing integrated changes in cell and nuclear structure in response to changes in extracellular matrix adhesivity or mechanics.

NASA Discipline Cell Biology↗
NASA NTRS2004

Experiments with osteoblasts cultured under hypergravity conditions

To understand further the role of gravity in osteoblast attachment, osteoblasts were subjected to hypergravity conditions in vitro. Scanning electron microscopy of all confluent coverslips from FPA units show that the number of attached osteoblasts was similar among gravitational levels and growth durations (~90 cells/microscopic field). Specifically, confluent 1.0 G control cultures contained an average of 91 +/- 8 cells/field, 3.3 G samples had 88 +/- 8 cells/field, and 4.0 G cultures averaged 90 +/- 7 cells/field. The sparsely plated cultures assessed by immunohistochemistry also had similar numbers of cells at each time point (l.0 G was similar to 3.3 and 4.0 G), but cell number changed from one time point to the next as those cells proliferated. Immunohistochemistry of centrifuged samples showed an increase in number (up to 160% increase) and thickness (up to 49% increase) of actin fibers, a decrease in intensity of fibronectin fluorescence (18-23% decrease) and an increase in number of vinculin bulbs (202-374% increase in number of vinculin bulbs/area). While hypergravity exposure did not alter the number of attached osteoblasts, it did result in altered actin, fibronectin, and vinculin elements, changing some aspects of osteoblast- substrate adhesion.

NASA Program Fundamental Space Biology↗
NASA NTRS2008

Calculations of Solar Shortwave Heating Rates due to Black Carbon and Ozone Absorption Using in Situ Measurements

Results for the solar heating rates in ambient air due to absorption by black-carbon (BC) containing particles and ozone are presented as calculated from airborne observations made in the tropical tropopause layer (TTL) in January-February 2006. The method uses airborne in situ observations of BC particles, ozone and actinic flux. Total BC mass is obtained along the flight track by summing the masses of individually detected BC particles in the range 90 to 600-nm volume-equivalent diameter, which includes most of the BC mass. Ozone mixing ratios and upwelling and partial downwelling solar actinic fluxes were measured concurrently with BC mass. Two estimates used for the BC wavelength-dependent absorption cross section yielded similar heating rates. For mean altitudes of 16.5, 17.5, and 18.5 km (0.5 km) in the tropics, average BC heating rates were near 0.0002 K/d. Observed BC coatings on individual particles approximately double derived BC heating rates. Ozone heating rates exceeded BC heating rates by approximately a factor of 100 on average and at least a factor of 4, suggesting that BC heating rates in this region are negligible in comparison.

Gao, R. S.↗
DOE OSTI2014

Unfurling of the band 4.1, ezrin, radixin, moesin (FERM) domain of the merlin tumor suppressor

The merlin-1 tumor suppressor is encoded by the Neurofibromatosis-2 (Nf2) gene and loss-of-function Nf2 mutations lead to nervous system tumors in man and to several tumor types in mice. Merlin is an ERM (ezrin, radixin, moesin) family cytoskeletal protein that interacts with other ERM proteins and with components of cell-cell adherens junctions (AJs). Merlin stabilizes the links of AJs to the actin cytoskeleton. Thus, its loss destabilizes AJs, promoting cell migration and invasion, which in Nf2{sup +/-} mice leads to highly metastatic tumors. Paradoxically, the 'closed' conformation of merlin-1, where its N-terminal four-point-one, ezrin, radixin, moesin (FERM) domain binds to its C-terminal tail domain, directs its tumor suppressor functions. Here we report the crystal structure of the human merlin-1 head domain when crystallized in the presence of its tail domain. Remarkably, unlike other ERM head-tail interactions, this structure suggests that binding of the tail provokes dimerization and dynamic movement and unfurling of the F2 motif of the FERM domain. We conclude the 'closed' tumor suppressor conformer of merlin-1 is in fact an 'open' dimer whose functions are disabled by Nf2 mutations that disrupt this architecture.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2013

Is a Swine Model of Arteriovenous Malformation Suitable for Human Extracranial Arteriovenous Malformation? A Preliminary Study

Objective: A chronic arteriovenous malformation (AVM) model using the swine retia mirabilia (RMB) was developed and compared with the human extracranial AVM (EAVM) both in hemodynamics and pathology, to see if this brain AVM model can be used as an EAVM model. Methods: We created an arteriovenous fistula between the common carotid artery and the external jugular vein in eight animals by using end-to-end anastomosis. All animals were sacrificed 1 month after surgery, and the bilateral retia were obtained at autopsy and performed hematoxylin and eosin staining and immunohistochemistry. Pre- and postsurgical hemodynamic evaluations also were conducted. Then, the blood flow and histological changes of the animal model were compared with human EAVM. Results: The angiography after operation showed that the blood flow, like human EAVM, flowed from the feeding artery, via the nidus, drained to the draining vein. Microscopic examination showed dilated lumina and disrupted internal elastic lamina in both RMB of model and nidus of human EAVM, but the thickness of vessel wall had significant difference. Immunohistochemical reactivity for smooth muscle actin, angiopoietin 1, and angiopoietin 2 were similar in chronic model nidus microvessels and human EAVM, whereas vascular endothelial growth factor was significant difference between human EAVM and RMB of model. Conclusions: The AVM model described here is similar to human EAVM in hemodynamics and immunohistochemical features, but there are still some differences in anatomy and pathogenetic mechanism. Further study is needed to evaluate the applicability and efficacy of this model.

62 RADIOLOGY AND NUCLEAR MEDICINE↗
DOE OSTI2013

Redundant control of migration and adhesion by ERM proteins in vascular smooth muscle cells

Highlights: •The three ERM proteins are expressed in vascular smooth muscle cell. •ERM depletion inhibited PDGF-evoked migration redundantly. •ERM depletion increased cell adhesion redundantly. •ERM depletion did not affect PDGF-evoked Ca signal, Rac1 activation, proliferation. •ERM proteins control PDGF-induced migration by regulating adhesion. -- Abstract: Ezrin, radixin, and moesin possess a very similar structure with a C-terminal actin-binding domain and a N-terminal FERM interacting domain. They are known to be involved in cytoskeleton organization in several cell types but their function in vascular smooth muscle cells (VSMC) is still unknown. The aim of this study was to investigate the role of ERM proteins in cell migration induced by PDGF, a growth factor involved in pathophysiological processes like angiogenesis or atherosclerosis. We used primary cultured VSMC obtained from rat aorta, which express the three ERM proteins. Simultaneous depletion of the three ERM proteins with specific siRNAs abolished the effects of PDGF on cell architecture and migration and markedly increased cell adhesion and focal adhesion size, while these parameters were only slightly affected by depletion of ezrin, radixin or moesin alone. Rac1 activation, cell proliferation, and Ca{sup 2+} signal in response to PDGF were unaffected by ERM depletion. These results indicate that ERM proteins exert a redundant control on PDGF-induced VSMC migration by regulating focal adhesion turn-over and cell adhesion to substrate.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2013

The small GTPase Rab5 homologue Ypt5 regulates cell morphology, sexual development, ion-stress response and vacuolar formation in fission yeast

Highlights: •Multiple functions of Rab5 GTPase in fission yeast were found. •Roles of Rab5 in fission yeast were discussed. •Relation between Rab5 and actin cytoskeleton were discussed. -- Abstract: Inner-membrane transport is critical to cell function. Rab family GTPases play an important role in vesicle transport. In mammalian cells, Rab5 is reported to be involved in the regulation of endosome formation, phagocytosis and chromosome alignment. Here, we examined the role of the fission yeast Rab5 homologue Ypt5 using a point mutant allele. Mutant cells displayed abnormal cell morphology, mating, sporulation, endocytosis, vacuole fusion and responses to ion stress. Our data strongly suggest that fission yeast Rab5 is involved in the regulation of various types of cellular functions.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Overexpression of Snail in retinal pigment epithelial triggered epithelial–mesenchymal transition

Highlights: • First reported overexpression of Snail in RPE cells could directly trigger EMT. • Further confirmed the regulator role of Snail in RPE cells EMT in vitro. • Snail may be a potential therapeutic target to prevent the fibrosis of PVR. - Abstract: Snail transcription factor has been implicated as an important regulator in epithelial–mesenchymal transition (EMT) during tumourigenesis and fibrogenesis. Our previous work showed that Snail transcription factor was activated in transforming growth factor β1 (TGF-β1) induced EMT in retinal pigment epithelial (RPE) cells and may contribute to the development of retinal fibrotic disease such as proliferative vitreoretinopathy (PVR). However, whether Snail alone has a direct role on retinal pigment epithelial–mesenchymal transition has not been investigated. Here, we analyzed the capacity of Snail to drive EMT in human RPE cells. A vector encoding Snail gene or an empty vector were transfected into human RPE cell lines ARPE-19 respectively. Snail overexpression in ARPE-19 cells resulted in EMT, which was characterized by the expected phenotypic transition from a typical epithelial morphology to mesenchymal spindle-shaped. The expression of epithelial markers E-cadherin and Zona occludin-1 (ZO-1) were down-regulated, whereas mesenchymal markers a-smooth muscle actin (a-SMA) and fibronectin were up-regulated in Snail expression vector transfected cells. In addition, ectopic expression of Snail significantly enhanced ARPE-19 cell motility and migration. The present data suggest that overexpression of Snail in ARPE-19 cells could directly trigger EMT. These results may provide novel insight into understanding the regulator role of Snail in the development of retinal pigment epithelial–mesenchymal transition.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Isorhynchophylline protects against pulmonary arterial hypertension and suppresses PASMCs proliferation

Highlights: • We focus on PASMCs proliferation in the pathogenesis of PAH. • Isorhynchophylline inhibited PASMCs proliferation and alleviated PAH. • IRN blocked PDGF-Rβ phosphorylation and its downstream signal transduction. • IRN regulated cyclins and CDKs to arrest cell cycle in the G0/G1 phase. • We reported IRN has the potential to be a candidate for PAH treatment. - Abstract: Increased pulmonary arterial smooth muscle cells (PASMCs) proliferation is a key pathophysiological component of pulmonary vascular remodeling in pulmonary arterial hypertension (PAH). Isorhynchophylline (IRN) is a tetracyclic oxindole alkaloid isolated from the Chinese herbal medicine Uncaria rhynchophylla. It has long been used clinically for treatment of cardiovascular and cerebrovascular diseases. However, very little is known about whether IRN can influence the development of PAH. Here we examined the effect of IRN on monocrotaline (MCT) induced PAH in rats. Our data demonstrated that IRN prevented MCT induced PAH in rats, as assessed by right ventricular (RV) pressure, the weight ratio of RV to (left ventricular + septum) and RV hypertrophy. IRN significantly attenuated the percentage of fully muscularized small arterioles, the medial wall thickness, and the expression of smooth muscle α-actin (α-SMA) and proliferating cell nuclear antigen (PCNA). In vitro studies, IRN concentration-dependently inhibited the platelet-derived growth factor (PDGF)-BB-induced proliferation of PASMCs. Fluorescence-activated cell-sorting analysis showed that IRN caused G0/G1 phase cell cycle arrest. IRN-induced growth inhibition was associated with downregulation of Cyclin D1 and CDK6 as well as an increase in p27Kip1 levels in PDGF-BB-stimulated PASMCs. Moreover, IRN negatively modulated PDGF-BB-induced phosphorylation of PDGF-Rβ, ERK1/2, Akt/GSK3β, and signal transducers and activators of transcription 3 (STAT3). These results demonstrate that IRN could inhibit PASMCs proliferation and attenuate pulmonary vascular remodeling after MCT induction. These beneficial effects were at least through the inhibition of PDGF-Rβ phosphorylation and its downstream signaling pathways. Therefore, IRN might be a potential candidate for the treatment of PAH.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2014

Expression of high mobility group box 1 in inflamed dental pulp and its chemotactic effect on dental pulp cells

Highlights: • HMGB1 translocated from nucleus to cytoplasm during dental pulp inflammation. • HMGB1and its receptor RAGE were up-regulated in hDPCs under LPS stimulation. • HMGB1 enhanced hDPCs migration and induces cytoskeleton reorganization. • HMGB1 may play a critical role in dental pulp repair during inflamed state. - Abstract: High mobility group box 1 protein (HMGB1) is a chromatin protein which can be released extracellularly, eliciting a pro-inflammatory response and promoting tissue repair process. This study aimed to examine the expression and distribution of HMGB1 and its receptor RAGE in inflamed dental pulp tissues, and to assess its effects on proliferation, migration and cytoskeleton of cultured human dental pulp cells (DPCs). Our data demonstrated that cytoplasmic expression of HMGB1 was observed in inflamed pulp tissues, while HMGB1 expression was confined in the nuclei in healthy dental pulp. The mRNA expression of HMGB1 and RAGE were significantly increased in inflamed pulps. In in vitro cultured DPCs, expression of HMGB1 in both protein and mRNA level was up-regulated after treated with lipopolysaccharide (LPS). Exogenous HMGB1 enhanced DPCs migration in a dose-dependent manner and induced the reorganization of f-actin in DPCs. Our results suggests that HMGB1 are not only involved in the process of dental pulp inflammation, but also play an important role in the recruitment of dental pulp stem cells, promoting pulp repair and regeneration.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Imp2, the PSTPIP homolog in fission yeast, affects sensitivity to the immunosuppressant FK506 and membrane trafficking in fission yeast

Cytokinesis is a highly ordered process that divides one cell into two cells, which is functionally linked to the dynamic remodeling of the plasma membrane coordinately with various events such as membrane trafficking. Calcineurin is a highly conserved serine/threonine protein phosphatase, which regulates multiple biological functions, such as membrane trafficking and cytokinesis. Here, we isolated imp2-c3, a mutant allele of the imp2{sup +} gene, encoding a homolog of the mouse PSTPIP1 (proline-serine-threonine phosphatase interacting protein 1), using a genetic screen for mutations that are synthetically lethal with calcineurin deletion in fission yeast. The imp2-c3 mutants showed a defect in cytokinesis with multi-septated phenotypes, which was further enhanced upon treatment with the calcineurin inhibitor FK506. Notably, electron micrographs revealed that the imp2-c3 mutant cells accumulated aberrant multi-lamella Golgi structures and putative post-Golgi secretory vesicles, and exhibited fragmented vacuoles in addition to thickened septa. Consistently, imp2-c3 mutants showed a reduced secretion of acid phosphatase and defects in vacuole fusion. The imp2-c3 mutant cells exhibited a weakened cell wall, similar to the membrane trafficking mutants identified in the same genetic screen such as ypt3-i5. These findings implicate the PSTPIP1 homolog Imp2 in Golgi/vacuole function, thereby affecting various cellular processes, including cytokinesis and cell integrity. - Highlights: • We isolated imp2-c3, in a synthetic lethal screen with calcineurin in fission yeast. • The imp2{sup +} gene encodes a component of the actin contractile ring similar to Cdc15. • The imp2-c3 mutants showed defects in cytokinesis, which were exacerbated by FK506. • The imp2-c3 mutants were defective in membrane trafficking and cell wall integrity. • Our study revealed a novel role for Imp2 in the Golgi/vacuolar membrane trafficking.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2015

Platelet-derived growth factor-D modulates extracellular matrix homeostasis and remodeling through TIMP-1 induction and attenuation of MMP-2 and MMP-9 gelatinase activities

Platelet-derived growth factor-D (PDGF-D) is a more recent recognized growth factor involved in the regulation of several cellular processes, including cell proliferation, transformation, invasion, and angiogenesis by binding to and activating its cognate receptor PDGFR-β. After bile duct ligation or in the carbon tetrachloride-induced hepatic fibrosis model{sub ,} PDGF-D showed upregulation comparable to PDGF-B. Moreover, adenoviral PDGF-D gene transfer induced hepatic stellate cell proliferation and liver fibrosis. We here investigated the molecular mechanism of PDGF-D involvement in liver fibrogenesis. Therefore, the GRX mouse cell line was stimulated with PDGF-D and evaluated for fibrotic markers and PDGF-D signaling pathways in comparison to the other PDGF isoforms. We found that PDGF-D failed to enhance Col I and α-smooth muscle actin (α-SMA) production but has capacity to upregulate expression of the tissue inhibitor of metalloprotease 1 (TIMP-1) resulting in attenuation of MMP-2 and MMP-9 gelatinase activity as indicated by gelatinase zymography. This phenomenon was restored through application of a PDGF-D neutralizing antibody. Unexpectedly, PDGF-D incubation decreased both PDGFR-α and -β in mRNA and protein levels, and PDGF-D phosphorylated typrosines specific for PDGFR-α and -β. We conclude that PDGF-D intensifies fibrogenesis by interfering with the fibrolytic activity of the TIMP-1/MMP system and that PDGF-D signaling is mediated through both PDGF-α and -β receptors. - Highlights: • PDGF-D signals through PDGF receptor type α and β. • PDGF-D modulates extracellular matrix homeostasis and remodeling. • Like PDGF-B, PDGF-D triggers phosphorylation of PLC-γ, Akt/PKB, JNK, ERK1/2, and p38. • PDGF-D induces TIMP-1 expression through ERK and p38 MAPK. • PDGF-D attenuates MMP-2 and MMP-9 gelatinase activities.

60 APPLIED LIFE SCIENCES↗