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Query: UNIPROT:P06889 (Mol)
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The regulation of morphological changes in eukaryotic cells is a complex process involving major components of the cytoskeleton including actin microfilaments, microtubules, and intermediate filaments (IFs). The putative effector of RhoA, RhoA-binding kinase alpha (ROKalpha), is a serine/threonine kinase that has been implicated in the reorganization of actin filaments and in myosin contractility. Here, we show that ROKalpha also directly affects the structural integrity of IFs. Overexpression of active ROKalpha, like that of RhoA, caused the collapse of filamentous vimentin, a type III IF. A RhoA-binding-deficient, kinase-inactive ROKalpha inhibited the collapse of vimentin IFs induced by RhoA in HeLa cells. In vitro, ROKalpha bound and phosphorylated vimentin at its head-rod domain, thereby inhibiting the assembly of vimentin. ROKalpha colocalized predominantly with the filamentous vimentin network, which remained intact in serum-starved cells. Treatment of cells with vinblastine, a microtubule-disrupting agent, also resulted in filamentous vimentin collapse and concomitant ROKalpha translocation to the cell periphery. ROKalpha translocation did not occur when the vimentin network remained intact in vinblastine-treated cells at 4 degreesC or in the presence of the dominant-negative RhoAN19 mutant. Transient translocation of ROKalpha was also observed in cells subjected to heat shock, which caused the disassembly of the vimentin network. Thus, the translocation of ROKalpha to the cell periphery upon overexpression of RhoAV14 or growth factor treatment is associated with disassembly of vimentin IFs. These results indicate that Rho effectors known to act on microfilaments may be involved in regulating the assembly of IFs. Vimentin when phosphorylated also exhibits reduced affinity for the inactive ROKalpha. The translocation of ROKalpha from IFs to the cell periphery upon action by activated RhoA and ROKalpha suggests that ROKalpha may initiate its own cascade of activation.
Mol Cell Biol 1998 Nov
PMID:RhoA-binding kinase alpha translocation is facilitated by the collapse of the vimentin intermediate filament network. 977 49

We have determined the mass-per-length (MPL) composition of distinct early assembly products of recombinant intermediate filament (IF) proteins from the four cytoplasmic sequence homology classes, and compared these values with those of the corresponding mature filaments. After two seconds under standard assembly conditions (i.e. 25 mM Tris-HCl (pH 7.5), 50 mM NaCl, 37 degrees C), vimentin, desmin and the neurofilament triplet protein NF-L aggregated into similar types of "unit-length filaments" (ULFs), whereas cytokeratins (CKs) 8/18 already yielded long IFs at this time point, so the ionic strength had to be reduced. The number of molecules per filament cross-section, as deduced from the MPL values, was lowest for CK8/18, i.e. 16 and 25 at two seconds compared to 16 and 21 at one hour. NF-L exhibited corresponding values of 26 and 30. Vimentin ULFs yielded a pronounced heterogeneity, with major peak values of 32 and 45 at two seconds and 30, 37 and 44 after one hour. Desmin formed filaments of distinctly higher mass with 47 molecules per cross-section, at two seconds and after one hour of assembly. This indicates that individual types of IF proteins generate filaments with distinctly different numbers of molecules per cross-section. Also, the observed significant reduction of apparent filament diameter of ULFs compared to the corresponding mature IFs is the result of a "conservative" radial compaction-type reorganization within the filament, as concluded from the fact that both the immature and mature filaments contain very similar numbers of subunits per cross-section. Moreover, the MPL composition of filaments is strikingly dependent on the assembly conditions employed. For example, vimentin fibers formed in 0.7 mM phosphate (pH 7.5), 2.5 mM MgCl2, yield a significantly increased number of molecules per cross-section (56 and 84) compared to assembly under standard conditions. Temperature also strongly influences assembly: above a certain threshold temperature "pathological" ULFs form that are arrested in this state, indicating that the system is forced into strong but unproductive interactions between subunits. Similar "dead-end" structures were obtained with vimentins mutated to introduce principal alterations in subdomains presumed to be of general structural importance, indicating that these sequence changes led to new modes of intermolecular interactions.
J Mol Biol 1999 Mar 12
PMID:Characterization of distinct early assembly units of different intermediate filament proteins. 1006 6

Vimentin is an intermediate filament protein normally expressed in cells of mesenchymal origin. The promoter of the human vimentin gene was previously reported to contain two positive-acting regions, separated by a negative region (Rittling, S.R., Baserga, R., 1987. Functional analysis and growth factor regulation of the human vimentin promoter. Mol. Cell. Biol. 7, 3908-3915). Here, detailed studies reveal two additional regulatory elements, a new positive transcriptional element located between -717 and -757, and a new repressor element at -780 to -821. In transient transfections, the positive-acting element is able to completely override the effect of different silencer elements when fused to a heterologous promoter. However, this element does not enhance gene activity when the silencer element is absent and thus cannot be viewed as a true enhancer. Since it appears to overcome the effect of a silencer element, we refer to it as an antisilencer element. Gel mobility shift assays, UV-cross-linking experiments, and Southwestern blots reveal that a 105-kDa protein specifically binds to this region.
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PMID:An antisilencer element is involved in the transcriptional regulation of the human vimentin gene. 1019 80

Vimentin is an intermediate filament protein normally expressed in cells of mesenchymal origin. The promoter of the human vimentin gene (-1416 to +73) was shown to contain two positive-acting regions, separated by a negative region, and at least eight GC-boxes as determined by sequence homology (Rittling, S.R., Baserga, R., 1987. Mol. Cell. Biol. 7, 3908-3915). We have analyzed the region -900 to +41 for protein binding by in vivo footprinting experiments using ligation-mediated PCR. For the various GC-boxes, we detect protein binding only to that GC-box (at position -64 and -55) closest to the transcriptional start site. Transient transfection assays of various vimentin 5'-end fragments and mutations thereof fused to the reporter gene cat indicate that this sequence is indispensable for promoter function regardless of the inclusion of upstream DNA sequences. In vitro binding studies confirm that this region binds protein specifically. We suggest that this GC-box and its binding factor are required for regulated expression of the human vimentin gene.
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PMID:A GC-box is required for expression of the human vimentin gene. 1041 34

Until recently, the accepted model held that p53 degradation occurs exclusively on cytoplasmic proteasomes and, hence, has an absolute requirement for nuclear export of p53 via the CRM1 pathway. However, proteasomes are abundant in both cytosol and nucleus. We recently analyzed HDM2-mediated degradation of endogenous p53 in the presence of various CRM1 blockers. We found that significant HDM2-mediated degradation takes place despite nuclear export blockade, indicating that endogenous p53 degradation occurs locally in the nucleus, in parallel to cytoplasmic degradation. Here, we describe how subcellular fractionation can be used to monitor nuclear and cytoplasmic degradation of endogenous wild-type p53 during the recovery phase after a stress stimulus. The fractions are then analyzed by immunoblotting in a time-dependent fashion. Vimentin and lamin A proteins are used to monitor the purity of the cytosolic and nuclear fractions, respectively, and to control for equal loading.
Methods Mol Biol 2003
PMID:Analysis of nuclear and cytoplasmic degradation of p53 in cells after stress. 1282 34

During mammalian vascular development, endothelial cells form a complex array of vessels that differ markedly in structure and function, but the molecular basis for this vascular complexity is poorly understood. Recent insights into endothelial diversity have come from the identification of molecular markers expressed on distinct endothelial cell populations. One such marker, the PAL-E antibody, has been used for almost 20 years to distinguish blood and lymphatic vessels, but the identity of the protein recognized by PAL-E has been unknown. In the present study we have used protein purification and tandem mass spectrometry analysis of tryptic peptides to identify the PAL-E antigen as a secreted form of vimentin. Vimentin has been well characterized as an intracellular intermediate filament protein expressed broadly in mesenchymal cells. In contrast, PAL-E-reactive vimentin is secreted extracellularly, its synthesis is restricted to a distinct population of blood endothelial cells and activated macrophages, and PAL-E-reactive vimentin is found in circulating human blood. PAL-E-reactive vimentin does not arise from an endothelial cell-specific mRNA transcript but is the product of cell-specific posttranslational modification. The PAL-E antibody therefore defines secretion of vimentin as a molecular distinction among endothelial cells and exposes a novel, extracellular role for vimentin in the blood vasculature.
Mol Cell Biol 2004 Oct
PMID:The endothelial cell-specific antibody PAL-E identifies a secreted form of vimentin in the blood vasculature. 1545 90

The ideal prosthesis to replace the diseased human aortic valve is not yet available. We have previously shown that porcine acellular aortic-valve conduits, obtained by detergent-enzymatic method, display hemodynamic performances similar to those of their native counterparts. Hence, it seemed worthwhile to ascertain whether these tissue-engineered prostheses can be successfully xenotransplanted. Porcine acellular conduits, which immunocytochemistry demonstrated to lack MHC class I and II antigens, were implanted in the thoracic aorta of 9 sheep. Two animals died just after surgery, and the other 7 sheep were sacrificed 1 or 5 months after transplantation. A rather favorable outcome of the implant was observed in 4 sheep. In these animals, aortic valves remained pliable and coaptive, and the luminal surface of the conduits was endothelized just after one month from surgery. An intense inflammatory response was present at 1 month, and, although attennuated, it persisted for 5 months, located mainly between the tunica intima and media and at the border of the implant. Vimentin-positive and smooth muscle actin-positive myofibroblasts proliferated within tunica media and adventitia, and an obvious thickening of the tunica intima was also observed. Small vessels were seen in the adventitia, and elastic fibers were well-preserved in both the aorta wall and valve leaflets. In the cases of unfavorable outcome (3 of 7 survived sheep), implants were detached from the aorta recipient and surrounded by a connective mass that almost completely obstructed their lumen. These masses were composed of a fibromyxoid background where proliferating cells, resembling those occurring in human reactive myofibroblastic lesions (proliferative fascitis), were embedded. Collectively, these rather disappointing findings indicate that acellular valve conduits, obtained by the detergent-enzymatic method, are presently not suitable for clinical applications because of the persistent inflammatory response, which conceivably triggers overgrowth mechanisms that lead to implant failure.
Int J Mol Med 2004 Dec
PMID:Biological fate of tissue-engineered porcine valvular conduits xenotransplanted in the sheep thoracic aorta. 1554 71

Vimentin is an intermediate filament that regulates cell attachment and subcellular organization. In this study, vimentin filaments were morphologically altered, and its soluble subunits were rapidly reduced via cadmium chloride treatment. Cadmium chloride stimulated three major mitogen-activated protein kinases (MAPKs): extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK), and p38, and led apoptotic pathway via caspase-9 and caspase-3 activations. In order to determine whether MAPKs were involved in this cadmium-induced soluble vimentin disappearance, we applied MAPK-specific inhibitors (PD98059, SP600125, SB203580). These inhibitors did not abolish the cadmium-induced soluble vimentin disappearance. Caspase and proteosome degradation pathway were also not involved in soluble vimentin disappearance. When we observed vimentin levels in soluble and insoluble fractions, soluble vimentin subunits shifted to an insoluble fraction. As we discovered that heat-shock protein 27 (HSP27) was colocalized and physically associated with vimentin in unstressed cells, the roles of HSP27 with regard to vimentin were assessed. HSP27-overexpressing cells prevented morphological alterations of the vimentin filaments, as well as reductions of soluble vimentin, in the cadmium-treated cells. Moreover, HSP27 antisense oligonucleotide augmented these cadmium-induced changes in vimentin. These findings indicate that HSP27 prevents disruption of the vimentin intermediate filament networks and soluble vimentin disappearance, by virtue of its physical interaction with vimentin in cadmium-treated SK-N-SH cells.
Exp Mol Med 2005 Oct 31
PMID:Heat shock protein 27 interacts with vimentin and prevents insolubilization of vimentin subunits induced by cadmium. 1626 67

The aim of this study was to characterize by immunohistochemistry the histogenesis of cysts in acquired cystic kidney disease (ACKD). Thirty renal tissues fixed in 10% formalin and embedded in paraffin from 20 cases of ACKD were studied. Vimentin was used to stain the Bowman's capsule epithelium, Lotus tetragonolobus agglutinin (LTA) and Leu M1 (CD15) for proximal tubules; Tamm-Horsfall protein (THP) for distal tubules; epithelial membrane antigen (EMA), cytokeratin 19 (CK19), Arachis hypogea agglutinin (PNA), and Glycine maximum agglutinin (SBA) for distal tubules and collecting ducts; and Ulex europaeus agglutinin (UEA-I) and Dolichos biflorus agglutinin (DBA) for collecting ducts. A histologically normal kidney, free of cystic disease, was used as a control for all the markers. Most of the cysts showed strong reactivity to LTA and CD15, an immunophenotype more characteristic of proximal tubules.
Appl Immunohistochem Mol Morphol 2006 Sep
PMID:Histogenesis of the acquired cystic kidney disease: an immunohistochemical study. 1693 28

The intermediate filament protein vimentin has been shown to be required for smooth muscle contraction. The adapter protein p130 Crk-associated substrate (CAS) participates in the signaling processes that regulate force development in smooth muscle. However, the interaction of vimentin filaments with CAS has not been well elucidated. In the present study, ACh stimulation of tracheal smooth muscle strips increased the ratio of soluble to insoluble vimentin (an index of vimentin disassembly) in association with force development. ACh activation also induced vimentin phosphorylation at Ser(56) as assessed by immunoblot analysis. More importantly, CAS was found in the cytoskeletal vimentin fraction, and the amount of CAS in cytoskeletal vimentin was reduced in smooth muscle strips on contractile stimulation. CAS redistributed from the myoplasm to the periphery during ACh activation of smooth muscle cells. The ACh-elicited decrease in CAS distribution in cytoskeletal vimentin was attenuated by the downregulation of p21-activated kinase (PAK) 1 with antisense oligodeoxynucleotides. Vimentin phosphorylation at this residue, the ratio of soluble to insoluble vimentin, and active force in smooth muscle strips induced by ACh were also reduced in PAK-depleted tissues. These results suggest that PAK may regulate CAS release from the vimentin intermediate filaments by mediating vimentin phosphorylation at Ser(56) and the transition of cytoskeletal vimentin to soluble vimentin. The PAK-mediated dissociation of CAS from the vimentin network may participate in the cellular processes that affect active force development during ACh activation of tracheal smooth muscle tissues.
Am J Physiol Lung Cell Mol Physiol 2007 Jan
PMID:Dissociation of Crk-associated substrate from the vimentin network is regulated by p21-activated kinase on ACh activation of airway smooth muscle. 1699 82


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