Expression animal cells

Intermediate filaments are present in most animal cells. They are composed of more than 50 proteins which are expressed in a cell-type specific manner. Their diameter is about 10 nm and thus between those of the larger microtubules and the smaller F-actin. They form scaffolds and networks in the cyto- and nucleoplasm. 

Mammalian cells Get export of proteins Get desired post-translational modifications and products not likely to be immunogenic to humans Good expression systems available Large-scale growth of animal cells costly Great care needed to avoid contamination of cultures... 

Plant-based production systems are now being used commercially for the synthesis of foreign proteins [1-3]. Post-translational modification in plant cells is similar to that carried out by animal cells plant cells are also able to fold multimeric proteins correctly. The sites of glycosylation on plant-produced mammalian proteins are the same as on the native protein however, processing of N-linked glycans in the secretory pathway of plant cells results in a more diverse array of glycoforms than is produced in animal expression systems [4]. Glycoprotein activity is retained in plant-derived mammalian proteins. 

When sufficiently high levels of expression and protein accumulation are achieved, efficient downstream processing protocols must be developed to insure product quality and the economic feasibility of production. As the demand for safe, recombinant pharmaceutical proteins continues to expand, the market potential of plant-produced recombinant proteins is considerable. Molecular farming can produce recombinant proteins at a lower cost than traditional expression systems based on microbial or animal cell culture, and without the risk of contamination with human pathogens. 

One of the most obvious benefits of plants is the potential for production scale up, leading to the production of virtually limitless amounts of recombinant antibody at minimal cost Plants are easy to grow, and unlike bacteria or animal cells their cultivation is straightforward and does not require specialist media, equipment or toxic chemicals. It has been estimated that plantibodies could be produced at a yield of 10-20 kg per acre at a fraction of the cost associated with production in mammalian cells [2,18] The use of plants also avoids many of the potential safety issues associated with other expression systems, such as contaminating mammalian viruses or prions, as well as ethical considerations involving the use of animals. 

The desired gene/cDNA is normally amplified, sequenced and then introduced into an expression vector that facilitates its introduction and expression (transcription and translation) in an appropriate producer cell type. All recombinant therapeutic proteins approved to date are produced in E. coli, S. cerevisiae or in animal cell lines (mainly CHO or BHK cells). The general... 

Animal cell culture (particularly CHO and BHK cell lines) Transgenic animals (focus thus far is upon sheep and goats) Plant-based expression systems (various)... 

Expression of recombinant proteins in animal cell culture systems... 

Although capable of glycosylating heterologous human proteins, the glycosylation pattern usually varies from the pattern observed on the native glycoprotein (when isolated from its natural source, or when expressed in recombinant animal cell culture systems). 

Functional in vitro assays can be whole-cell assays or animal tissue assays. For in vitro cell-based assays, recombinant molecular targets can be expressed in cell lines and linked to second-messenger systems to measure functional responses. Examples of functional... 

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