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PubMed1990

Vinculin is a permanent component of the membrane skeleton and is incorporated into the (re)organising cytoskeleton upon platelet activation.

Vinculin, a 130-kDa protein discovered in chicken gizzard smooth-muscle cells and subsequently also described in platelets, is believed to be involved in membrane-cytoskeleton interactions. In this study we investigated vinculin distribution in human blood platelets. Two skeletal fractions and a remaining cytosolic fraction were prepared with a recently described Triton X-100 lysis buffer causing minimal post-lysis breakdown by proteolysis. The presence of vinculin was demonstrated in the membrane skeleton and cytosol of resting and thrombin-activated human platelets. Upon thrombin stimulation vinculin also appeared in the cytoskeleton. this cytoskeletal incorporation was completed during the early stages of platelet aggregation and secretion, when the uptake of myosin, actin-binding protein and talin was still not maximal. We conclude therefore, that vinculin may play an important role in the structural (re)organisation of the human platelet cytoskeleton upon platelet activation.

Blood Platelets↗
PubMed1991

Multiple alpha-tubulin isoforms in cilia and cytoskeleton of Tetrahymena pyriformis generated by post-translational modifications. Studies during reciliation.

alpha-Tubulin microheterogeneity was studied in Tetrahymena pyriformis. Using two-dimensional electrophoretic analysis, we found between five and seven alpha-tubulin and four beta-tubulin isoforms in cilia and four or five alpha-tubulins and two beta-tubulins in cytoskeleton. Immunoblotting assay with anti-(acetyl alpha-tubulin) monoclonal antibody 6-11B-1 and [3H]acetate labelling revealed that the alpha-tubulin isoforms are post-translationally modified by acetylation. Our results also show that tubulins in the soluble cytoplasmic fraction are not acetylated. Nevertheless, a slight reaction with the antibody 6-11 B-1 can be observed in the taxol and vinblastine-treated cytoplasmic pool. Pulse/chase experiments using [35S]methionine during cell reciliation have demonstrated that the basic alpha-tubulin isoforms are converted into acidic isoforms in the absence of protein synthesis, suggesting that the basic alpha-tubulin is the precursor of the acidic forms which are found in cilia and cytoskeleton. In-vivo-translation selection demonstrated the existence of a single precursor molecule which corresponded to the most basic alpha-tubulin. Taken together, our results provide evidence for the existence of post-translational modifications, namely acetylation. Nevertheless, other post-translational mechanisms involved in the biosynthesis of microtubules of cilia and cytoskeleton are required to explain the whole alpha-tubulin heterogeneity.

Acetates↗
PubMed1999

Insulin stimulation of rat ventricular K+ currents depends on the integrity of the cytoskeleton.

1. The effect of insulin on K+ currents was studied with enzymatically dispersed ventricular myocytes from insulin-deficient (type I) diabetic rats. Diabetic conditions were induced by a single intravenous injection of streptozotocin (100 mg kg-1) given 8-13 days before the experiments. Measurements of plasma glucose and insulin levels confirmed the diabetic status of the animals. 2. A Ca2+-independent transient outward K+ current, It, and a slowly inactivating, quasi-steady-state current, Iss, which are depressed in diabetic myocytes, could be restored by exposure to 1, 10 or 100 nM insulin. This was only observed after a delay of 5-6 h, although an insulin exposure of only 1 h was sufficient to initiate its stimulatory action on It and Iss. The stimulatory effect of insulin on these K+ currents was prevented by 2 microM cycloheximide, which in itself had no direct effect on these currents. 3. Disruption of the actin microfilament network with 1 microM cytochalasin D (CD) also prevented the stimulatory effect of 100 nM insulin on both It and Iss. Since CD was added 1 h after insulin, inhibitory effects on insulin signalling were ruled out. Adding CD (1 microM) 5-9 h after insulin, when currents were already augmented, had no effect (up to 50 min exposure). Incubating control cells for 6-10 h with 1 microM CD had no effect on any of the currents measured. 4. Stabilization of the actin network by pre-exposure to 2.5 microM phalloidin restored the stimulatory effect of insulin, in the continued presence of CD, ruling out any effects of CD on components other than the cytoskeleton. 5. The stimulatory effect of insulin was also prevented by incubating cells with insulin in the presence of the microtubule-disrupting agent colchicine (5 microM). 6. These results suggest that the insulin-mediated augmentation of K+ currents in diabetic myocytes requires protein synthesis, possibly of K+ channels, as well as an intact cytoskeleton. The possibility that newly formed channels translocate to the plasma membrane in a process dependent on different elements of the cytoskeleton is discussed.

Actins↗
PubMed2000

The actin cytoskeleton in store-mediated calcium entry.

Store-mediated Ca2+ entry is the main pathway for Ca2+ influx in platelets and many other cells. Several hypotheses have considered both direct and indirect coupling mechanisms between the endoplasmic reticulum and the plasma membrane. Here we pay particular attention to new insights into the regulation of store-mediated Ca2+ entry: the role of the cytoskeleton in a secretion-like coupling model. In this model, Ca2+ entry may be mediated by a reversible trafficking and coupling of the endoplasmic reticulum with the plasma membrane, that shows close parallels to the events mediating secretion. As with secretion, the actin cytoskeleton plays an inhibitory role in the activation of Ca2+ entry by preventing the approach and coupling of the endoplasmic reticulum with the plasma membrane, making cytoskeletal remodelling a key event in the activation of Ca2+ entry. We also review recent advances investigating the regulation of store-mediated Ca2+ entry by small GTPases and phosphoinositides, which might be involved in the store-mediated Ca2+ entry pathway through roles in the remodelling of the cytoskeleton.

Actins↗
PubMed2006

Ethanol suppresses LPS-induced Toll-like receptor 4 clustering, reorganization of the actin cytoskeleton, and associated TNF-alpha production.

BACKGROUND: Ethanol (EtOH) suppresses cytokine responses induced through most Toll-like receptors (TLRs), but the mechanism of action is unclear. We recently found that acute EtOH alters lipopolysaccharide (LPS)-induced partitioning of CD14, a critical component of the LPS receptor complex, within lipid raft fractions in the macrophage-like cell line RAW264.7. METHODS: Here we investigated the role of receptor clustering in alteration of the responses of cells to LPS caused by EtOH both in vitro and in vivo. The cellular distribution of CD14, TLR4, actin cytoskeleton, and tumor necrosis factor-alpha (TNF-alpha) were studied by confocal microscopy following exposure of cells to LPS with or without EtOH. TLR4 and CD14 were clustered into highly colocalized patches on the cell membrane accompanied by the reorganization of the actin cytoskeleton in some of the RAW264.7 cells as well as peritoneal cells following LPS treatment. RESULTS: Addition of EtOH reduced the number of cells that had LPS-induced receptor patches and in which this reorganization occurred. Cells on which CD14 and TLR4 formed clusters or caps had substantially higher levels of membrane-bound TNF-alpha compared with cells without clustering or capping of these molecules. Interference with the actin cytoskeleton by cytochalasin D suppressed the production of TNF-alpha and receptor clustering, as EtOH did. CONCLUSIONS: These data confirm our previous observations, suggest a novel mechanism of EtOH action that involves interference with receptor clustering, and indicate a potential role of actin filaments in the formation of receptor patches, subsequent activation of macrophages by LPS, and production of TNF-alpha.

Actins↗
PubMed1995

Cytoskeleton and PCH-induced pigment aggregation in Macrobrachium potiuna erythrophores.

Herein we report the effects of microtubule- and actin-like filament disrupting drugs, as well as the microtubule stabilizer taxol, on PCH-induced pigment granule aggregation within erythrophores of the freshwater crustacean Macrobrachium potiuna. Dose-response curves (DRCs) to the pigment-concentrating hormone PCH were determined under control and experimental conditions to evaluate the effects elicited by the cytoskeleton-affecting drugs. Colchicine, at temperatures 22 degrees C and 4 degrees C, and vinblastine significantly inhibited the aggregating response to PCH and affected the dynamics of the process, as shown by the change in the slope of the regression curve calculated from the DRCs. Lumicolchicine, a colchicine analogue with no affinity for tubulin, also inhibited pigment migration, though no change in the slope of the regression curve was observed. The inhibitory effects of lumicolchicine demonstrate that changes in sites other than cytoskeleton, such as membrane permeability, may also cause a decrease in the PCH-induced aggregating responses and that the colchicine effects may result from its action on cellular sites additional to the cytoskeleton. Taxol, a microtubule stabilizer, did not affect the DRC to PCH, and DMSO improved the PCH-evoked responses, pointing out to the maintenance of tubulin in the polymerized state as the appropriate condition for aggregation. Cytochalasin B, an actin-like filament disrupter, diminished the aggregating responses to the hormone, with no change in the slope of the regression curve, indicating that these elements take part in the process and that cytosolic calcium rise, sol/gel transformations and endoplasmic reticulum motility may well play an important role in granule migration. It is suggested that microtubules are steadily polymerized as a requirement for pigment aggregation and that process is biphasic, the initial phase being dependent on the microtubule integrity.

Animals↗
PubMed2001

A new model for in vitro clot formation that considers the mode of the fibrin(ogen) contacts to platelets and the arrangement of the platelet cytoskeleton.

The constitution of platelet-fibrin(ogen) contacts, the separation of the platelets initially aggregated, and the rearrangement of the platelet cytoskeleton during clot formation (0.5 to 60 minutes after thrombin stimulation) were investigated using ultrastructural and immunocytochemical techniques. After aggregation, fibrin polymerizing within focal contacts and from degranulating secretory granules contributed to the fibers. The initially formed focal contacts with fibrin obviously persisted during clot formation. The physiological branching of the fibers enabled separation of platelets. The contact associated cytoskeleton formed a constricting and fiber internalizing sphere, but later stress fiber like bundles. As retraction progressed, the cytoskeleton changed to stress fiber connecting focal contacts with fibers. A model of clot formation in vitro is presented that reflects both the contributions of platelets (fibrin fiber internalization and retraction) and of fibers (branching) enabling the retraction.

Blood Platelets↗
PubMed2003

Partitioning of cortical and deep cytoskeleton responses from transient magnetic bead twisting.

We attempted to estimate in living adherent epithelial alveolar cells, the degree of structural and mechanical heterogeneity by considering two individualized cytoskeleton components, i.e., a submembranous "cortical" cytoskeleton and a "deep" cytoskeleton (CSK). F-actin structure characterizing each CSK component was visualized from spatial reconstructions at low and high density, respectively, especially in a 10-microm-cubic neighborhood including the bead. Specific mechanical properties (Young elastic and viscous modulus E and n) were revealed after partitioning the magnetic twisting cytometry response using a double viscoelastic "solid" model with asymmetric plastic relaxation. Results show that the cortical CSK response is a faster (tau1 < or = 0.7 s), softer (E1: 63-109 Pa), moderately viscous (n1: 7- 18 Pas), slightly tensed, and easily damaged structure compared to the deep CSK structure which appears slower (tau2 approximately 1/2 min), stiffer (E2: 95-204 Pa), highly viscous (n2: 760-1967 Pa s), more tensed, and fully elastic, while exhibiting a larger stress hardening behavior. Adding drug depolymerizing actin filaments decreased predominantly the deep CSK stiffness. By contrast, an agent altering cell-matrix interactions affected essentially the cortical CSK stiffness. We concluded that partitioning the CSK within cortical and deep structures is largely consistent with their respective functional activities.

Actins↗
PubMed2005

Finite-element analysis of the adhesion-cytoskeleton-nucleus mechanotransduction pathway during endothelial cell rounding: axisymmetric model.

Endothelial cells possess a mechanical network connecting adhesions on the basal surface, the cytoskeleton, and the nucleus. Transmission of force at adhesions via this pathway can deform the nucleus, ultimately resulting in an alteration of gene expression and other cellular changes (mechanotransduction). Previously, we measured cell adhesion area and apparent nuclear stretch during endothelial cell rounding. Here, we reconstruct the stress map of the nucleus from the observed strains using finite-element modeling. To simulate the disruption of adhesions, we prescribe displacement boundary conditions at the basal surface of the axisymmetric model cell. We consider different scenarios of the cytoskeletal arrangement, and represent the cytoskeleton as either discrete fibers or as an effective homogeneous layer When the nucleus is in the initial (spread) state, cytoskeletal tension holds the nucleus in an elongated, ellipsoidal configuration. Loss of cytoskeletal tension during cell rounding is represented by reactive forces acting on the nucleus in the model. In our simulations of cell rounding, we found that, for both representations of the cytoskeleton, the loss of cytoskeletal tension contributed more to the observed nuclear deformation than passive properties. Since the simulations make no assumption about the heterogeneity of the nucleus, the stress components both within and on the surface of the nucleus were calculated. The nuclear stress map showed that the nucleus experiences stress on the order of magnitude that can be significant for the function of DNA molecules and chromatin fibers. This study of endothelial cell mechanobiology suggests the possibility that mechanotransduction could result, in part, from nuclear deformation, and may be relevant to angiogenesis, wound healing, and endothelial barrier dysfunction.

Animals↗
PubMedDate not supplied

Classifying structural alterations of the cytoskeleton by spectrum enhancement and descriptor fusion.

A classifier capable of ranking structural alterations of the cytoskeleton is developed. Images of cytoskeletal microtubules obtained from the epifluorescence microscopy of primary culture rat hepatocytes are analyzed. Morphological descriptors are extracted by contour and mass fractal analysis, direct methods, and spectrum enhancement. All methods are designed and tuned to make the extracted morphological descriptors insensitive to absolute fluorescence intensities. Spectrum enhancement is a nonlinear filter that involves spatial differentiation of the gray-scale image followed by conversion of power spectral density to the logarithmic scale and averaging over arcs in the reciprocal domain. Enhanced spectra exhibit local maxima that correspond to the structured microtubule bundles of a normal cytoskeleton. Descriptor fusion for classification is achieved by means of multivariate analysis. The classifier is trained by image sets representing normal ("negative control") microtubules and those altered by exposure to a fungicide at the highest dose of the experiment design. Some sensitivity and validation tests, including discriminant functions analysis, are applied to the classifier. The latter is applied to recognize images of microtubules not used in the training stage and comes from treatments at lower concentrations and shorter times. As a result, structural alterations are ranked and structural recovery after treatment is quantified. The method has potential use in quantitative, morphology-based tests on the cytoskeleton treated either by anticancer drugs or by cytotoxic agents.

Algorithms↗
PubMed2003

Evidence that nuclear factor-kappa B activation is critical in oxidant-induced disruption of the microtubule cytoskeleton and barrier integrity and that its inactivation is essential in epidermal growth factor-mediated protection of the monolayers of intestinal epithelia.

Using monolayers of intestinal (Caco-2) cells, we showed that oxidants disrupt the microtubule cytoskeleton and barrier integrity; epidermal growth factor (EGF) was protective via stabilization of the microtubules. Because proinflammatory conditions activate nuclear factor-kappaB (NF-kappaB), we hypothesized that oxidants disrupt barrier integrity through activation of NF-kappaB and that EGF protects by suppressing NF-kappaB. Parental cells were pretreated with EGF or NF-kappaB or inhibitory kappaBalpha (I-kappaBalpha) modulators. Other cells were stably transfected with varying levels of a dominant negative mutant for the NF-kappaB inhibitor I-kappaBalpha. Both types of cells were grown as monolayers and then exposed to oxidant (H2O2). We then monitored monolayer barrier integrity (permeability), stability of the microtubule cytoskeleton (confocal microscopy, immunoblotting), intracellular levels of the I-kappaBalpha (immunoblotting), translocation, and activity of NF-kappaB (immunoblotting, sensitive enzyme-linked immunosorbent assay). Monolayers were also fractionated and processed to assess alterations in 1) polymerized tubulin (S2; an index of cytoskeletal integrity) and 2) monomeric tubulin (S1; an index of disassembly) (polyacrylamide gel electrophoresis fractionation and immunoblotting). We found the following: 1) Oxidants caused I-kappaBalpha degradation, NF-kappaB translocation, NF-kappaB (p50 and p65 subunits) activation, tubulin disassembly ( upward arrow S1, downward arrow S2), microtubule architectural instability, and barrier disruption. I-kappaBalpha stabilizers and NF-kappaB inhibitors [e.g., carbobenzyloxy-leuleu-leucinol (MG-132), lactacystin] suppressed oxidants injurious effects. 2) EGF (10 ng/ml) stabilized I-kappaBalpha and prevented both NF-kappaB translocation and activation while protecting monolayers against oxidants. 3) In stably transfected cells, transfection-induced stabilization of I-kappaBalpha by itself led to EGF-like protective effects. In these mutant cells, protection was not potentiated by EGF (10 ng/ml). Conclusions are 1) oxidants induce disruption of the cytoskeleton and intestinal barrier integrity, in part, through I-kappaBalpha degradation and subsequent NF-kappaB activation, 2) I-kappaBalpha stabilization is by itself protective, mimicking EGF, and 3) EGF protects cell monolayers through I-kappaBalpha stabilization and NF-kappaB inactivation. To our knowledge, this is the first report that NF-kappaB can affect the dynamics of cytoskeletal assembly and intestinal barrier integrity.

Biological Transport↗
PubMed2002

Mechanotransduction: all signals point to cytoskeleton, matrix, and integrins.

Mechanical stresses modulate cell function by either activating or tuning signal transduction pathways. Mechanotransduction, the process by which cells convert mechanical stimuli into a chemical response, occurs both in cells specialized for sensing mechanical cues and in parenchymal cells whose primary function is not mechanosensory. However, common among the various responses to mechanical stress is the importance of direct or indirect connections between the internal cytoskeleton, the extracellular matrix (ECM), and traditional signal transducing molecules. In many instances, these elements converge at focal adhesions, sites of structural attachment between the cytoskeleton and ECM that are anchored by cell surface integrin receptors. Alenghat and Ingber discuss the accumulating evidence for the central role of cytoskeleton, ECM, and integrin-anchored focal adhesions in several mechanotransduction pathways.

Animals↗
PubMed1998

Coxiella burnetii induces reorganization of the actin cytoskeleton in human monocytes.

Coxiella burnetii, an obligate intracellular bacterium which survives in myeloid cells, causes Q fever in humans. We previously demonstrated that virulent C. burnetii organisms are poorly internalized by monocytes compared to avirulent variants. We hypothesized that a differential mobilization of the actin cytoskeleton may account for this distinct phagocytic behavior. Scanning electron microscopy demonstrated that virulent C. burnetii stimulated profound and polymorphic changes in the morphology of THP-1 monocytes, consisting of membrane protrusions and polarized projections. These changes were transient, requiring 5 min to reach their maximum extent and vanishing after 60 min of incubation. In contrast, avirulent variants of C. burnetii did not induce any significant changes in cell morphology. The distribution of filamentous actin (F-actin) was then studied with a specific probe, bodipy phallacidin. Virulent C. burnetii induced a profound and transient reorganization of F-actin, accompanied by an increase in the F-actin content of THP-1 cells. F-actin was colocalized with myosin in cell protrusions, suggesting that actin polymerization and the tension of actin-myosin filaments play a role in C. burnetii-induced morphological changes. In addition, contact between the cell and the bacterium seems to be necessary to induce cytoskeleton reorganization. Bacterial supernatants did not stimulate actin remodeling, and virulent C. burnetii organisms were found in close apposition with F-actin protrusions. The manipulation of the actin cytoskeleton by C. burnetii may therefore play a critical role in the internalization strategy of this bacterium.

Actins↗
PubMed2004

Differential effects of actin cytoskeleton dynamics on equine infectious anemia virus particle production.

Retrovirus assembly and budding involve a highly dynamic and concerted interaction of viral and cellular proteins. Previous studies have shown that retroviral Gag proteins interact with actin filaments, but the significance of these interactions remains to be defined. Using equine infectious anemia virus (EIAV), we now demonstrate differential effects of cellular actin dynamics at distinct stages of retrovirus assembly and budding. First, virion production was reduced when EIAV-infected cells were treated with phallacidin, a cell-permeable reagent that stabilizes actin filaments by slowing down their depolymerization. Confocal microscopy confirmed that the inhibition of EIAV production correlated temporally over several days with the incorporation dynamics of phallacidin into the actin cytoskeleton. Although the overall structure of the actin cytoskeleton and expression of viral protein appeared to be unaffected, phallacidin treatment dramatically reduced the amount of full-length Gag protein associated with the actin cytoskeleton. These data suggest that an association of full-length Gag proteins with de novo actin filaments might contribute to Gag assembly and budding. On the other hand, virion production was enhanced when EIAV-infected cells were incubated briefly (2 h) with the actin-depolymerizing drugs cytochalasin D and latrunculin B. Interestingly, the enhanced virion production induced by cytochalasin D required a functional late (L) domain, either the EIAV YPDL L-domain or the proline-rich L domains derived from human immunodeficiency virus type 1 or Rous sarcoma virus, respectively. Thus, depolymerization of actin filaments may be a common function mediated by retrovirus L domains during late stages of viral budding. Taken together, these observations indicate that dynamic actin polymerization and depolymerization may be associated with different stages of viral production.

Actins↗
PubMed1999

Rho3 of Saccharomyces cerevisiae, which regulates the actin cytoskeleton and exocytosis, is a GTPase which interacts with Myo2 and Exo70.

The Rho3 protein plays a critical role in the budding yeast Saccharomyces cerevisiae by directing proper cell growth. Rho3 appears to influence cell growth by regulating polarized secretion and the actin cytoskeleton, since rho3 mutants exhibit large rounded cells with an aberrant actin cytoskeleton. To gain insights into how Rho3 influences these events, we have carried out a yeast two-hybrid screen using an S. cerevisiae cDNA library to identify proteins interacting with Rho3. Two proteins, Exo70 and Myo2, were identified in this screen. Interactions with these two proteins are greatly reduced or abolished when mutations are introduced into the Rho3 effector domain. In addition, a type of mutation known to produce dominant negative mutants of Rho proteins abolished the interaction with both of these proteins. In contrast, Rho3 did not interact with protein kinase C (Pkc1), an effector of another Rho family protein, Rho1, nor did Rho1 interact with Exo70 or Myo2. Rho3 did interact with Bni1, another effector of Rho1, but less efficiently than with Rho1. The interaction between Rho3 and Exo70 and between Rho3 and Myo2 was also demonstrated with purified proteins. The interaction between Exo70 and Rho3 in vitro was dependent on the presence of GTP, since Rho3 complexed with guanosine 5'-O-(3-thiotriphosphate) interacted more efficiently with Exo70 than Rho3 complexed with guanosine 5'-O-(3-thiodiphosphate). Overlapping subcellular localization of the Rho3 and Exo70 proteins was demonstrated by indirect immunofluorescence. In addition, patterns of localization of both Exo70 and Rho3 were altered when a dominant active allele of RHO3, RHO3(E129,A131), which causes a morphological abnormality, was expressed. These results provide a direct molecular basis for the action of Rho3 on exocytosis and the actin cytoskeleton.

Actins↗
PubMed2006

Modulation of prion formation, aggregation, and toxicity by the actin cytoskeleton in yeast.

Self-perpetuating protein aggregates transmit prion diseases in mammals and heritable traits in yeast. De novo prion formation can be induced by transient overproduction of the corresponding prion-forming protein or its prion domain. Here, we demonstrate that the yeast prion protein Sup35 interacts with various proteins of the actin cortical cytoskeleton that are involved in endocytosis. Sup35-derived aggregates, generated in the process of prion induction, are associated with the components of the endocytic/vacuolar pathway. Mutational alterations of the cortical actin cytoskeleton decrease aggregation of overproduced Sup35 and de novo prion induction and increase prion-related toxicity in yeast. Deletion of the gene coding for the actin assembly protein Sla2 is lethal in cells containing the prion isoforms of both Sup35 and Rnq1 proteins simultaneously. Our data are consistent with a model in which cytoskeletal structures provide a scaffold for generation of large aggregates, resembling mammalian aggresomes. These aggregates promote prion formation. Moreover, it appears that the actin cytoskeleton also plays a certain role in counteracting the toxicity of the overproduced potentially aggregating proteins.

Actins↗
PubMed2000

Immune reaction against the cytoskeleton in coeliac disease.

BACKGROUND: The cytoskeleton actin network of intestinal microvilli has been found to be rapidly impaired after gluten challenge in coeliac disease (CD). The aim of this study was to investigate the presence of an immune reaction towards cytoskeleton structures such as actin filaments in CD. METHODS: Eighty three antiendomysial antibody positive CD patients (52 children and 31 adults) were studied at our outpatient clinics from 1996 to 1998 using indirect immunofluorescence, ELISA, and western blotting for antiactin (AAA) and antitissue transglutaminase (TGA) antibodies before and after a gluten free diet (GFD). Sixteen patients with smooth muscle antibody positive autoimmune hepatitis, 21 with inflammatory bowel diseases, seven with small bowel bacterial overgrowth, and 60 healthy subjects were studied as controls. RESULTS: Fifty nine of 83 CD patients (28/31 adults (90.3%); 31/52 children (59.6%)) were positive for IgA and/or IgG AAA. Seventy seven (92.7%) were positive for IgA TGA. IgA AAA were strongly correlated with more severe degrees of intestinal villous atrophy (p<0.0001; relative risk 86.17). After a GFD, AAA became undetectable within five months. CONCLUSIONS: Apart from the immune reaction against the extracellular matrix, we have described an immune reaction against the cytoskeleton in both children and adults with CD. As AAA are strongly associated with more severe degrees of villous atrophy, they may represent a useful serological marker of severe intestinal atrophy in CD.

Adolescent↗
PubMed2001

Arginine induced acute pancreatitis alters the actin cytoskeleton and increases heat shock protein expression in rat pancreatic acinar cells.

Arginine induced acute pancreatitis was evaluated as a novel and distinct form of experimental pancreatitis with particular attention to the actin cytoskeleton and expression of heat shock or stress proteins. Arginine induced a dose related necrotising pancreatitis in rats, as shown by histological evaluation, and an increase in serum amylase. Severe pancreatitis induced by 4.5 g/kg arginine was accompanied by dramatic changes in the actin cytoskeleton, as visualised with rhodamine phallodin. Intermediate filaments were also disrupted, as visualised by cytokeratin 8/18 immunocytochemistry. Arginine pancreatitis was accompanied by a stress response with a large increase in the small heat shock protein HSP27, as well as HSP70, peaking at 24 hours and localised to acinar cells. There was a lower increase in HSP60 and HSP90 and no effect on GRP78. HSP27 was also shifted to phosphorylated forms during pancreatitis. A lower dose of arginine (3.0 g/kg) induced less pancreatitis but a larger increase in HSP70 and HSP27 expression and phosphorylation of HSP27. Thus HSP expression can be overwhelmed by severe damage. The present work in conjunction with earlier work on caerulein induced pancreatitis indicates that changes in the actin cytoskeleton are an early component in experimental pancreatitis.

Actin Cytoskeleton↗