Estudo computacional dos mecanismos moleculares associados a via de sinalização da miostatina humana

Abstract

This work consists of a modeling process of the proteins presents on the human myostatin (MSTN) signaling pathway, a negative regulator of skeletal muscle system growth. The project objective was to elucidate the extracellular activation process of MSTN and its binding modes with cellular receptors and the endogenous inhibitor (follistatin) after its activation, in view of assist the design of new drugs. The protocol employed molecular dynamics simulations (Amber24 software) with production times of 500 ns, in replicas. The stability and affinity of the complexes were quantified by the MM-GBSA method, allowing the identification of critical residues (hot spots) and the comparison of the free energy interaction between different systems. The results revealed that MSTN activation requires a specific conformational rearrangement in the "wrist helix" region (residues E314–A330), essential to release access to the receptorbinding site. Furthermore, it was observed that during the activation cascade, the gradual loss of the arm and forearm domains destabilized the precursor, facilitating the transition to the active form of the protein. Regarding transmembrane receptors, the study demonstrated a thermodynamic preference of MSTN for AcvR2B over AcvR2A, with an affinity approximately two times higher and a more robust network of interactions (12 hot spots). In the complexes of MSTN associated with type II and I activin receptors, the systems formed with AcvR2B proved to be about 40 kcal mol-1 more stable than the complexes with AcvR2A. This apparent phenomenon of "instability propagation" indicates that AcvR2B functions as a determining factor for the integrity of the final signaling complex. In addition, the presence of AcvR2B tends to homogenize the binding energy of ALKs, suggesting that the preference between receptors in the cell may be dictated by kinetic factors and protein availability. Regarding the development of inhibitors, the forearm region stood out as a promising template. The analysis showed that the α1 sub-region (nonpolar) blocks the type I site, while α2 (amphipathic) inhibits the type II site. With this, it was possible to propose pharmacophoric models for the design of small molecules capable of mimicking these natural interactions.