|
| ||
|
|
||
Aberrant Localization (aberrant + localization)
Selected AbstractsPlectin deposition at podosome rings requires myosin contractilityCYTOSKELETON, Issue 8 2008Annica Gad Abstract Metalloproteinase-dependent tissue invasion requires the formation of podosomes and invadopodia for localized matrix degradation. Actin cytoskeleton remodeling via Arp2/3-mediated actin polymerization is essential for podosome formation, and dynamic microtubules have an important role in maintaining podosome turnover in macrophages and osteoclasts. Little is known, however, about the involvement of the intermediate filament cytoskeleton in formation, stabilization, and turnover of podosomes. Here we show that vimentin intermediate filaments colocalize with the early sites of podosome formation at the stress fiber - focal adhesion interface in cultured vascular smooth muscle cells, but do not directly contribute to podosome formation, or stabilization. In unstimulated A7r5 cells the cytolinker protein plectin poorly colocalized with vimentin and the microdomains, but following induction by phorbol ester accumulated in the rings that surround the podosomes. In plectin-deficient A7r5 cells actin stress fiber remodelling is reduced in response to PDBu, and small podosomes remain localized at stable actin stress fibres. Pharmacological inhibition of actomyosin contractility by blebbistatin leads to an aberrant localization of podosomes away from the cell periphery and induces failure of plectin to surround the outer perimeter of these invasive adhesions. Taken together, we conclude that plectin is involved in growth and maturation of podosomes by reducing focal adhesion and stress fiber turnover, and that actomyosin-dependent contractility is required for the peripheral localization and specific deposition of plectin at the podosome rings. Cell Motil. Cytoskeleton 2008. © 2008 Wiley-Liss, Inc. [source] Myosin-mediated cytoskeleton contraction and Rho GTPases regulate laminin-5 matrix assemblyCYTOSKELETON, Issue 2 2004Gregory W. deHart Abstract Laminin-5 is a major structural element of epithelial tissue basement membranes. In the matrix of cultured epithelial cells, laminin-5 is arranged into intricate patterns. Here we tested a hypothesis that myosin II-mediated actin contraction is necessary for the proper assembly of a laminin-5 matrix by cultured SCC12 epithelial cells. To do so, the cells were treated with ML-7, a myosin II light chain kinase inhibitor, or Y-27632, an inhibitor of Rho-kinase (ROCK), both of which block actomyosin contraction. Under these conditions, laminin-5 shows an aberrant localization in dense patches at the cell periphery. Since ROCK activity is regulated by the small GTPase Rho, this suggests that members of the Rho family of GTPases may also be important for laminin-5 matrix assembly by SCC12 cells. We confirmed this hypothesis since SCC12 cells expressing mutant proteins that inhibit RhoA, Rac, and Cdc42 assemble the same aberrant laminin-5 protein arrays as drug-treated cells. We have also evaluated the organization of the laminin-5 receptors ,3,1 and ,6,4 integrin and hemidesmosome proteins in ML-7- and Y-27632-treated cells or in cells in which RhoA, Rac, and Cdc42 activity were inhibited. In all instances, ,3,1 and ,6,4 integrin heterodimers, as well as hemidesmosome proteins, localize precisely with laminin-5 in the matrix of the cells. In summary, our results provide evidence that myosin II-mediated actin contraction and the activity of Rho GTPases are necessary for the proper organization of a laminin-5 matrix and localization of hemidesmosome protein arrays in epithelial cells. Cell Motil. Cytoskeleton 57:107,117, 2004. © 2004 Wiley-Liss, Inc. [source] The zebrafish ennui behavioral mutation disrupts acetylcholine receptor localization and motor axon stabilityDEVELOPMENTAL NEUROBIOLOGY, Issue 1 2008Louis Saint-Amant Abstract The zebrafish ennui mutation was identified from a mutagenesis screen for defects in early behavior. Homozygous ennui embryos swam more slowly than wild-type siblings but normal swimming recovered during larval stages and homozygous mutants survived until adulthood. Electrophysiological recordings from motoneurons and muscles suggested that the motor output of the CNS following mechanosensory stimulation was normal in ennui, but the synaptic currents at the neuromuscular junction were significantly reduced. Analysis of acetylcholine receptors (AChRs) in ennui muscles showed a marked reduction in the size of synaptic clusters and their aberrant localization at the myotome segment borders of fast twitch muscle. Prepatterned, nerve-independent AChR clusters appeared normal in mutant embryos and dispersed upon outgrowth of motor axons onto the muscles. Genetic mosaic analysis showed that ennui is required cell autonomously in muscle fibers for normal synaptic localization of AChRs. Furthermore, exogenous agrin failed to induce AChR aggregation, suggesting that ennui is crucial for agrin function. Finally, motor axons branched more extensively in ennui fast twitch muscles especially in the region of the myotome borders. These results suggest that ennui is important for nerve-dependent AChR clustering and the stability of axon growth. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2008 [source] Nucleophosmin (NPM1) mutations in adult and childhood acute myeloid leukaemia: towards definition of a new leukaemia entity,HEMATOLOGICAL ONCOLOGY, Issue 4 2009Rachel Rau Abstract Nucleophosmin (NPM) is a ubiquitously expressed chaperone protein that shuttles rapidly between the nucleus and cytoplasm, but predominantly resides in the nucleolus. It plays key roles in ribosome biogenesis, centrosome duplication, genomic stability, cell cycle progression and apoptosis. Somatic mutations in exon 12 of the NPM gene (NPM1) are the most frequent genetic abnormality in adult acute myeloid leukaemia (AML), found in approximately 35% of all cases and up to 60% of patients with normal karyotype (NK) AML. In children, NPM1 mutations are far less frequent, occurring in 8,10% of all AML cases, and in approximately 25% of those with a NK. NPM1 mutations lead to aberrant localization of the NPM protein into the cytoplasm, thus the designation, NPMc+ AML. NPMc+ AML is seen predominantly in patients with a NK and is essentially mutually exclusive of recurrent chromosomal translocations. Patients with NPM1 mutations are twice as likely as those who lack an NPM1 mutation to also have a FMS-like tyrosine kinase (FLT3) internal tandem duplication (ITD) mutation. NPMc+ AML is also characterized by a unique gene expression signature and microRNA signature. NPMc+ AML has important prognostic significance, as NPMc+ AML, in the absence of a coexisting FLT3-ITD mutation, is associated with a favourable outcome. NPM1 mutations have also shown great stability during disease evolution, and therefore represent a possible marker for minimal residual disease detection. Given its distinctive biologic and clinical features and its clear clinical relevance, NPMc+ AML is included as a provisional entity in the 2008 WHO classifications. There is still much to be learned about this genetic alteration, including its exact role in leukaemogenesis, how it interacts with other mutations and why it confers a more favourable prognosis. Further, it represents a potential therapeutic target warranting research aimed at identifying novel small molecules with activity in NPMc+ AML. Copyright © 2009 John Wiley & Sons, Ltd. [source] Alteration of subcellular and cellular expression patterns of cyclin B1 in renal cell carcinoma is significantly related to clinical progression and survival of patientsINTERNATIONAL JOURNAL OF CANCER, Issue 4 2006Stephen O. Ikuerowo Abstract Cyclin B1, identified as a regulator of late cell cycle, is involved in the development and progression of a variety of human malignancies. To clarify the role of cyclin B1 in the pathogenesis and prognosis of renal cell carcinoma (RCC), protein expression was compared with clinicopathological characteristics of patients as well as the long-term survival after surgical therapy. Expression analysis was carried out by immunohistochemistry and tissue microarray analysis. The microarrays that represented the primary tumors, their invasion front and normal peritumoral renal parenchyma contained 753 tissue cores obtained from 251 randomly selected nephrectomy specimens. Immunopositivity within the primary tumors was significantly associated with tumor stage (pT) (p < 0.01), lymph node status (pN) (p < 0.01) as well as the presence of systemic metastatic disease (p = 0.01). Subcellular expression in the cytoplasm of tumor cells significantly correlated with pT (p = 0.02) and pN (p = 0.03). When peritumoral tissue samples exhibited a relative amount of <10% of positively reacting epithelial cells, cyclin B positivity was identified to predict long-term survival of patients in univariate analysis (p < 0.01) whereas borderline significance was observed in multivariate statistical analysis (p = 0.05). Increased intratumoral cyclin B1 positivity and aberrant localization of signals within the cytoplasm of tumor cells is positively correlated with the tendency towards tumor progression, indicating the significant role of cyclin B1 in the development and pathogenesis of RCC. The result of uni- and multivariate statistical analysis suggests the prognostic value of cyclin B1 for RCC patients. © 2006 Wiley-Liss, Inc. [source] | |||||||||||||