Cells are impressive machines: they are highly coordinated, extremely efficient, and very clean in their modus operandi. To perform the highly ordered molecular processes, all components of the cell must be under tight control and no substructure is allowed to waste energy. There appears to be a teleological pathway in cell evolution, but the phenomenon itself is not completely unveiled, and thus we are tempted to speculate about the cells’ past and future. Important concerns include costly mistakes in the coordination of cell activities (which can lead to cancer) and cell decay.
Evolution has selected several intricate and fine-tuned mechanisms to turn cells into the building blocks of every living being and in the case of unicellular organisms, to create a unique energy producing machine to spread genes. Among these mechanisms is an essential task provided by specialized proteins, the chaperones, which help other proteins to complete their work. These proteins are conserved classes of polypeptides that were initially associated with heat shock stress, and are now generically designated as heat shock proteins (HSPs) (Tissières et al. 1974). Since their initial discovery, dozens of HSPs have been identified and characterized, and functional activities such as activation, translocation and degradation of proteins have been assigned to them in many organisms (Finka et al. 2016). All of these activities have in common the characteristic feature of a molecular chaperone which is to assist the proper folding and assembly of other proteins. Without theHSPs, the cell would loose its capacity to keep some of those ordered and essential processes.
Parasites constitute another interesting piece of this phenomenon. As organisms that depend on others to survive, we might be tempted to think that in parasites, molecular chaperones should perform activities aligned with this main purpose of a parasitic cell. But evolution does not discard a structure that was fine-tuned to deal with the adaptative requirements of the fittest one. A typical molecular chaperone in a protozoa parasite will be working similarly to an auxiliary protein in any other cell from a free living organism.
It is strange to think about altruistic behavior for molecules, considering that altruism is more of a human concept and perception than a physical fact of nature. But if we assume that assisting others (be it a molecule, a wild animal or a human being) to get their work done is the precondition to altruism, then this happens in the parasitic cell. But what is a parasite? It is another human definition, and in the realm of organisms competing for survival, it does not matter if an organized structure is feeding directly on others, forcing others to feed them, or cooperating with others to survive together. All of these are just looking for the means to get their information (inheritable coded instructions for survival) transmitted to their offspring. We, humans, have decided that some organisms will be parasitic, others predators, others symbionts, and others collaborators. Categorization, while quite logical for the human mind, is irrelevant for molecules, genes and processes in general.
To focus on the particular details of the unicellular parasites, some clever methods are used. We are witnessing the beginning of a true revolution in the basic analysis of genomes and their biological functions: the CRISPR – cas9, a rather simple and powerful tool to edit genome composition through a system borrowed from prokaryotes (Jinek et al. 2012). While we wait for the development of specifically tailored editing methods for the trypanosomatid genomes, transfection through engineered plasmids are still used for analysis of these parasites. An example of the use of this methodology can be seen in the July 2016 issue of the Memorias do Instituto Oswaldo Cruz: HSP70 of Leishmania amazonensis alters resistance to different stresses and mitochondrial bioenergetics, by Codonho et al. Several features of Leishmania sp. are demonstrated to be under the control of HSP 70, aggregating more activities to this very busy class of molecules.
What else might be revealed in the realm of molecular chaperones from protozoan parasites? Well, wait for the next season of results from the CRISPR-Cas9 research...
Adeilton Alves Brandão | Editor
Codonho BS, Costa SS, Peloso EF, Joazeiro PP, Gadelha FR, Giorgio S. HSP70 of Leishmania amazonensis alters resistance to different stresses and mitochondrial bioenergetics (2016). Mem Inst Oswaldo Cruz, 111 (7), DOI: 10.1590/0074-02760160087
Tissières A, Mitchell HK, Tracy UM. (1974). Protein synthesis in salivary glands of Drosophila melanogaster: relation to chromosome puffs. J Mol Biol. 84:389-98.
Finka A, Mattoo RU, Goloubinoff P. (2016). Experimental Milestones in the Discovery of Molecular Chaperones as Polypeptide Unfolding Enzymes. Annu Rev Biochem. 85:715-42. doi: 10.1146/annurev-biochem-060815-014124.
Jinek M, Chylinski K, Fonfara I, Hauer M, Doudna JA, Charpentier E. (2012). A programmable dual-RNA-guided DNA endonuclease in adaptive bacterial immunity. Science., 337:816-21. doi: 10.1126/science.1225829