1,721,055 research outputs found
Aggresome formation by anti-Ras intracellular scFv fragments. The fate of the antigen-antibody complex
Full text linkDiverting the antigen from its normal intracellular location to other compartments in an antibody-mediated way represents a mode of action for intracellular antibodies [Cardinale, A., Lener, M., Messina, S., Cattaneo, A. & Biocca, S. (1998) FEBS Lett., 439, 197-202; Lener, M., Horn, I.R., Cardinale, A., Messina, S., Nielsen, U.B., Rybak, S.M., Hoogenboom, H.R., Cattaneo, A. & Biocca, S. (2000) Eur J Biochem. 267, 1196-205]. In the case of p21Ras, the sequestration of the antigen in aggregated structures in the cytoplasm of transfected cells leads to the inhibition of its biological function. We have further investigated the intracellular fate of the antigen-antibody complex by analyzing the effect of proteasome inhibitors on the formation and the intracellular localization of the aggregates. Overexpression of anti-Ras scFv fragments or inhibition of proteasomes activity leads to the formation of large perinuclear aggresomes formed of ubiquitinated-scFv fragments in which p21Ras is sequestered and degraded in an antibody-mediated way. Disruption of microtubules by nocodazole completely abrogates the accumulation of scFv fragments in a single aggresome and induces the dispersion of these structures in the periphery of the cell. Cotransfection of the GFP-scFv with a myc-tagged ubiquitin and colocalization with specific anti-proteasome antibodies indicate the recruitment of exogenous ubiquitin and proteasomes to the newly formed aggresomes. Taken together these results suggest that the intracellular antigen-antibody complex is naturally addressed to the ubiquitin-proteasome pathway and that the mechanism of ubiquitination does not inhibit the antibody binding properties and the capacity to block the antigen function
Evidence for proteasome dysfunction in cytotoxicity mediated by anti-Ras intracellular antibodies
Full text linkAnti-Ras intracellular antibodies inhibit cell proliferation in vivo by sequestering the antigen and diverting it from its physiological location [Lener, M., Horn, I. R., Cardinale, A., Messina, S., Nielsen, U.B., Rybak, S.M., Hoogenboom, H.R., Cattaneo, A., Biocca, S. (2000) Eur. J. Biochem.267, 1196-1205]. Here we demonstrate that strongly aggregating single-chain antibody fragments (scFv), binding to Ras, induce apoptosis, and this effect is strictly related to the antibody-mediated aggregation of p21Ras. Proteasomes are quickly recruited to the newly formed aggregates, and their activity is strongly inhibited. This leads to the formation of aggresome-like structures, which become evident in the vast majority of apoptotic cells. A combination of anti-Ras scFv fragments with a nontoxic concentration of the proteasome inhibitor, lactacystin, markedly increases proteasome dysfunction and apoptosis. The dominant-negative H-ras (N17-H-ras), which is mostly soluble and does not induce aggresome formation or inhibit proteasome activity, only affects cell viability slightly. Together, these observations suggest a mechanism linking antibody-mediated Ras aggregation, impairment of the ubiquitin-proteasome system, and cytotoxicity
The selection of intracellular antibodies
No full textThe intracellular expression of antibodies in mammalian cells is a strategy to inhibit the in vivo function of selected molecules but is limited by the unpredictable behaviour of antibodies when intracellularly expressed. Recent advances in the field of antibody expression in Escherichia coli show that the introduction of mutations can improve the properties of some antibody domains, but the general applicability of this approach to intracellular antibodies remains to be proved. As a complement to rational approaches, we describe selection schemes in which antibodies are selected on the basis of their performance in vivo as intracellular antibodies
Intracellular Antibodies
No full textRecent advances in the field of recombinant antibodies have permitted the manipulation of genes encoding specific antibodies, thus allowing their ectopic expression in a wide variety of non-lymphoid cells. This volume describes how the ectopic expression of antibodies, as secreted or as intracellularly retargeted molecules, can be exploited to block biological functions or to confer new phenotypic traits (e.g. resistance to a virus). This is the first book describing this emerging technology, which is receiving increasing attention for application in many different fields and biological systems - from human gene therapy to plant biotechnology
Combating protein misfolding and aggregation by intracellular antibodies
No full textConformational or misfolding diseases are a large class of devastating human disorders associated with protein misfolding and aggregation. Most conformational diseases are caused by a combination of genetic and environmental factors, suggesting that spontaneous events can destabilize the protein involved in the pathology or impair the clearance mechanisms of misfolded aggregates. Aging is one of the risk factors associated to these events, and the clinical relevance of conformational disorders is growing dramatically, as they begin to reach epidemic proportions due to increases in mean lifespan. Currently, there are no effective strategies to slow or prevent these diseases. Intrabodies are promising therapeutic agents for the treatment of misfolding diseases, because of their virtually infinite ability to specifically recognize the different conformations of a protein, including pathological isoforms, and because they can be tarqeted to the potential sites of aggregation (both intra- and extracellular sites). These molecules can work as neutralizing agents bgainst amyloidogenic proteins by preventing their aggregation, and/or as molecular shunters of intracellular traffic by rerouting the protein from its potential aggregation site. The fast-developing field of recombinant antibody technology provides intrabodies with enhanced binding specificity and stability, together with lower immunogenicity, for use in a clinical setting. This review provides an update on the applications of intrabodies in misfolding diseases, with particular emphasis on an evaluation of their multipie and feasible modes of action. © 2008 Bentham Science Publishers Ltd
The potential of intracellular antibodies for therapeutic targeting of protein-misfolding diseases
No full textMisfolding diseases are a wide group of devastating disorders characterized by the accumulation of pathological protein aggregates. Although these disorders still lack an effective treatment, new antibody-based strategies are emerging and entering clinical trials. The intrabody approach is a gene-based technology developed to neutralize or modify the function of intracellular and extracellular target antigens. Because intrabodies can potentially target all the different isoforms of a misfolding-prone protein, including pathological conformations, they are emerging as therapeutic molecules for the treatment of misfolding diseases, including Alzheimer's, Parkinson's, Huntington's and prion diseases. This review will provide a description of the intrabody approach, an update of preclinical studies on misfolding diseases and an outlook on the intrabody delivery issue for therapeutic purposes. © 2008 Elsevier Ltd. All rights reserved
Can intrabodies targeted to the secretory compartment interact with a cytosolic protein? A comment on the article by Sawahata et al. "Cytoplasmic expression and specific binding of the VH/VL single domain intrabodies in transfected NIH3T3 cells",
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