Proteins Modulating Cellular Functions
Human gene therapy is a useful and valuable approach to introduce new genetic material into the cells of an individual with the objective of enhancing a therapeutic benefit. A number of human diseases have been recognized to be genetic in origins, such as Huntington's chorea and cystic fibrosis. In reality, except for trauma, all diseases are associated with a hereditary component. Hence, using gene therapy to treat severe diseases by replacing defective genes with a normal healthy gene offers a potential therapeutic opportunity for patients who suffer from these disorders.
Therapeutic Agents of Nucleic Acids
Nucleic acids (DNA, RNA) are one of the most significant resources not only for the understanding of fundamental mechanisms of human life but also for the development of a novel introduction of therapeutics. One of the extraordinary advantages of DNA-based pharmaceuticals is their selective recognition of molecular targets, conferring huge specificity of action.
DNA-based therapeutics involves oligonucleotides for antisense and antigene applications, plasmids, DNA aptamers, and DNAzymes. In gene therapy, gene transfer technologies are DNA delivery systems of nucleic acid-related treatments. Dozens of RNA-based pharmaceuticals are currently under clinical investigation for diseases covering genetic disorders and many cancers. These emerging drugs, including therapeutic aptamers, ribozymes, and small interfering RNAs (siRNAs), illustrate the unprecedented versatility of RNA molecules.
Figure 1. Therapeutic nucleic acids. (Giacca, 2010)
Proteins Modulating Cellular Functions
Recent advances in biological targets and medicines have expanded the scope of therapeutic agents for a diversity of human diseases. The intention of several gene therapies is not to supply a missing cellular function, but to express proteins for normal cell behavior. The approaches used are very variegated. For instance, in the field of cancer gene therapy, some assays take advantage of the feasibility to induce arrest of cell proliferation by cyclin-dependent kinase (CDK) inhibitors (e.g., p21 or p27), or checkpoint proteins (e.g., p53). Again in this field, another interesting type of protein is those that improve the therapeutic index of chemotherapy. On several occasions, myeloid toxicity restrains the dosage of antineoplastic drugs that can be administered to patients with a solid tumor. In such cases, it's possible to impart resistance to CD34+ hematopoietic precursors by transferring into these cells a gene coding for a membrane transporter (e.g., MDR gene), responsible for preventing the intracellular accumulation of a vast series of anticancer drug.
Other examples of proteins modulating cellular functions are those situations for gene therapy of viral infections, blocking the activity of certain viral proteins and impairing viral infection. Among these proteins, RevM10 is a mutated format of the HIV-1 Rev protein, working as a transdominant negative mutation. When this protein is present in CD4+ T lymphocytes, it inhibits wild-type Rev function and then prevents viral replication. Finally, the immune response against cancer cells can be promoted by expressing, in these cells, the genes coding for co-stimulatory proteins, such as B7, LFA-3, or ICAM-1 or which are usually downregulated in tumors as a basic mechanism of immune escape and however are necessary for antigenic presentation to cytotoxic T lymphocytes.
Proteins and Gene Expression
It has been undergoing a period to study the impact of proteins on genes or other proteins. A proper way is to see what happens in the cells when the protein of interest isn't present. For this, several model systems are used, including cell culture or whole organisms, wherein they're able to test the function of specific proteins or genes by mutating, knocking, or modifying them. The expression level of a gene can be estimated by measuring the transcribed mRNA (Northern Blot), the expressed protein (Western Blot), or directly staining the protein when it's still in the cells. The latest techniques have changed the tool to study gene expression, such as DNA microarrays, high-throughput sequencing, and serial analysis of gene expression (SAGE) allows larger screens of multiple molecules simultaneously. To analyze enormous datasets and explore networks of molecules interact, a discipline named systems biology establishes the framework for more integrated understandings of regulatory networks.
Intriguingly, proteins are not the only subject for gene regulators. RNA is also a class of regulatory molecules and acts on other nucleic acids by influencing or disrupting them. Ultimately, results from different studies have fundamental relevance, from normal cell function, such as cell growth, division, and differentiation, to informing unique approaches for treating diseases. In reality, some human diseases can simply arise from a defect in a protein's three-dimensional (3D) structure. Through the research of proteins and gene expression, it's easy to find how minute changes at the molecular level have an obvious reverberating reaction.
Reference
- Giacca, M. Therapeutic nucleic acids. (2010). Gene Therapy. Chaper2: 9-45.
