Resumen de Protein dissection approach as a powerful tool to identify new potential drugs
Protein-protein interactions (PPIs) play essential roles in biological processes: often proteins interact with each other to exert their functions creating a network of PPIs crucial in metabolism, as well as signaling mechanisms (interaction of messenger molecules, hormones, neurotransmitters and their cognate receptors) and gene expression (protein-DNA interactions). Alterations of these interactions are often at the basis of several pathologies, thus the identification of molecules able to modulate, inhibit or promote PPIs represents a powerful therapeutic approach. Furthermore, small protein domains or secondary structure motifs are often investigated to gain insights into global structure or/and to modulate interactions with external partners. In the last years, synthetic peptides capable to interfere with PPIs are receiving increasing attention. This study is focused on the design, functional and structural characterization of peptides covering active protein fragments that are employed as template to design peptidomimetics with improved drug-like properties. During this thesis, these topics were applied to two projects: i) the miniaturization of the multidomain protein Nucleophosmin 1 (NPM1) to unveil structural determinants of mutations associated with acute myeloid leukemia (AML) disease and ii) the development of new anti-inflammatory compounds as mimetics of suppressors of cytokine signaling (SOCS) proteins involved in the Janus kinase (JAK)/signal of activation (STAT) pathway.
NPM1 is a multifunctional protein involved in the pathogenesis of several human malignancies with peculiar mutations in AML. Its C-terminal domain (CTD) is endowed with a three-helix bundle in its wt form instead it is unfolded in AML mutated forms where the loss of NoLS (Nucleolar Localization Signal) causes an aberrant translocation of NPM1 to the cytosol (NPMc+). On the basis of previous investigations that unexpectedly exhibited a strong amyloid-aggregation propensity of several protein regions of the AML mutated CTD herein, to deepen the molecular mechanisms associated with AML misfolding and the leukemogenic potentials of AML mutations, biophysical features of several protein regions, were investigated. In detail the smallest amyloidogenic stretch of the entire NPM1 sequence encompassing region 264-272 demonstrated able to form amyloid aggregates through helical intermediate and a direct link between AML mutations and amyloidogenicity was assessed in the characterization of peptides covering the 3rd helix of the bundle in its AML mutated sequences. Amyloidogenic hot-spots, differently located into the entire protein, exhibited cooperative aggregative mechanism when included in the polypeptide deriving from the connection of H2 and H3 in the type A mutated variant, H2MutA.
The employment of protein domains as template for the design of peptidomimetics as potential drugs was carried out in the design and characterization of mimetics compounds of SOCS proteins. In detail, for SOCS1 several analogues of the lead compound named PS5 were designed, structurally and functionally investigated both in vitro and in vivo. In this study some restricted cyclic peptides, bearing non-natural amino acids, revealed able to mimic SOCS1’s biological functions. For SOCS3, the lack of previous studies prompted toward the investigation of linear peptides covering flat protein regions and chimeric sequences connecting not contiguous regions. The in vitro and cellular characterization of these compounds revealed, for the first time, that mimetics of SOCS3 can have powerful therapeutic application and pave the way to design macrocycles to inhibit the formation of JAK2/SOCS3 complex. Some of the designed compounds show promise as potential therapeutics, given their anticancer, anti-atherogenic and anti-inflammatory properties.
