IN SILICO STUDIES OF NULL GRASP55 AND PHOSPHORYLATED-GRASP55 INTERACTIONS WITH MATRIX METALLOPROTEINASE 2 (MMP2) and INTERLEUKIN-1β (IL-1β)

The combination of experimental and in silico approaches makes it possible to unravel complex biological processes and disease mechanisms of proteins, favoring personalized medicine. In this context, the Golgi Reassembly and Stacking Proteins 55kda (GRASP55) protein is a protein with a central participation in the Unconventional Protein Secretion (UPS) III and IV pathways, being an important target. GRASP55 interacts with charge proteins, directing them to unconventional secretion. Because of this, we studied the in silico interactions between GRASP55 and pro Matrix Metalloproteinase 2 (proMMP2) and Interleukin-1β (IL-1β), to elucidate cellular mechanisms and identify relevant therapeutic targets. In silico analysis, using AlphaFold, was performed for GRASP55 (phosphorylated and non-phosphorylated) in interaction with proMMP2 and IL-1β. All predictions indicated an interaction between GRASP55 and its phosphorylated models with both charge proteins. This suggests that GRASP55 phosphorylation primarily regulates its subcellular localization and participation in UPS, but not its binding affinity with the charge proteins. Previous data from the group also indicated that phosphorylation reduces GRASP55's ability to form molecular condensates. Given the hypothesis that GRASP55 forms condensates for unconventional secretion, these results reinforce the probability of direct interaction between GRASP55 and its load partners, with a propensity to form molecular aggregates. This work allows us to analyze in detail the molecular interactions of GRASP55 with MMP2 and IL-1β, providing a new insight into the mechanisms of unconventional secretion. Understanding these mechanisms can serve as a basis for the development of targeted therapies, the identification of biomarkers, and the understanding of the pathogenesis of diseases associated with dysfunction of protein secretion and aggregation.