K1K1 AND K1K1-GS: CHARACTERIZATION AND OPTIMIZATION OF EXPRESSION FOR INDUSTRIAL PRODUCTION

Therapeutic proteins obtained through recombinant DNA techniques allows the treatment of a wide range of human diseases, from metabolic disorder to cancer and play a significant role in regenerative medicine. Regenerative medicine allows the replacement or regeneration human cells, tissues and organs to reestablish physiological functions after damages due to trauma, pathologies or aging. In this field, growth factors and their receptors are ideal targets since they act important roles in many cellular processes. One of the most relevant growth factor involved in mitogenic, motogenic and morphogenic processes related to epithelial tissue regeneration is Hepatocyte Growth Factor/Scatter Factor (HGF/SF), a multi-domain cytokine of 80 kDa. It interacts with the tyrosine kinase receptor Met, inducing its dimerization and consequent activation of the downstream pathways. It can potentially be used as therapeutic molecule but there are many disadvantages related to its poor tissue distribution, instability and high production cost, which represent a major obstacle for clinical applications. To overcome these obstacles, K1K1, a potent receptor agonist based on two HGF/SF kringle 1 domains has been developed. This protein is smaller (20 kDa), easier to produce, and has superior stability compared to HGF/SF. Moreover, in vitro K1K1 shows potency equal or superior to HGF/SF in promoting cell survival and cell migration. However, the ease of production of this protein is linked to prokaryotic organisms, which synthesize the protein and store it into the so-called non-classical inclusion bodies (ncIB). The extraction of the protein from ncIB is based on the usage of large quantities of L-arginine, an aspect incompatible with industrial scale up. Therefore, one of the most important perspectives is finding an expression system able to secrete the protein in the culture media from which the protein can be recovered by fast and economic downstream processes facilitating the large-scale production of the molecule. One of the most important eukaryotic expression system is represented by Pichia pastoris, a yeast characterized by high growth rate, ability to grow into inexpensive medium, and suitable for both small and large-scale production. The aims of my work are 1) investigating the activity of K1K1-GS, a mutant of K1K1 in which the linker between the two kringle domains has been replaced with a poly-glycine sequence (G-S-G-G-S) to understand if a different linker of the same length can affect the properties of the protein, the expression, the purification, and the activity in vitro, 2) expressing the protein in the yeast P. pastoris.