Mercoledì del PRIN n.10: Benny Danilo Belviso – Rosanna Rizzi/Giovanna Papadopoulos
PCSK9 interactions: towards new tools for hypercholesterolemia therapy
Dr. Benny Danilo Belviso
Hypercholesterolemia is a pathological status related to high cholesterol level. Such disease is a form of hyperlipidemia and dyslipidemia associated to high-mortality rate complications, such as cardiovascular diseases and heart failure. European Society of Cardiology and Food and Drug Administration guidelines suggest to monitor hypercholesterolemia closely, especially in the case of high-risk patients, whose number is increasing year–by-year due to population aging. Today, available drugs to treat hypercholesterolemia include statins and antibodies that, particularly in the case of high-risk patients, are administered to reduce cholesterol by at least 50%. However, statins show side effects such as diabetes, myopathy, serious kidney problems, and are not recommended during pregnancy, whilst antibodies require parenteral administration and act on proteins involved in cholesterol homeostasis at extracellular level only. PCSK9 protein is a convertase whose level is directly related to cholesterol concentration in the blood and forms protein-protein complexes that are considered potential anti-hypercholesterolemia drug targets. However, till now, structure-based rational drug-design campaigns have relied only on the very poor structural information available for such complexes. This project aims to provide such structural information by combining X-ray based techniques, such as protein crystallography and small angle X-ray scattering, molecular dynamics and state-of-art deep learning protein-modelling techniques. Particularly, it will be investigated the promising interaction between PCSK9 and the N-terminal region of the LDLr, as well as between PCSK9 and selected proteins involved in its secretion, maturation, and degradation. Moreover, by considering that PCSK9 variants are strictly related to hypercholesterolemia onset, selected and already known loss- and gain-of-function PCSK9 variants will be investigated to assess the effect of the carried mutations on protein folding, as well as on the ability of the convertase to form protein-protein complexes associated to cholesterol homeostasis. In silico methods will be exploited to identify conserved residues involved in mutations and potentially related to hypercholesterolemia. Structural information on PCSK9-involving complexes will be exploited to outlines the topology of the molecular contacts, as well as the presence of candidate binding pockets to be screened by virtual screening techniques against drug libraries. Finally, based on such information, a drug-design campaign will be attempted to translate our results in new potential cholesterol lowering molecules.
Keywords: Cholesterol, structural biology, drug design, protein-protein ineraction, PCSK9, LDLr
Pharmacological Chaperon Therapy for Type I Mucopolysaccharidosis
Dr. Rosanna Rizzi/Giovanna Papadopoulos
Mucopolysaccharidosis type I (MPS I) is a rare autosomal recessive lysosomal storage disorder caused by mutations in the IDUA gene, which encodes α-L-iduronidase. This enzyme degrades glycosaminoglycans (GAGs) like dermatan and heparan sulfate. Enzymatic deficiency leads to GAG accumulation in lysosomes, disrupting cellular function and causing multisystemic damage with clinical severity ranging from mild to severe.
MPS I is classified into three phenotypes: Hurler syndrome (severe), Hurler-Scheie syndrome (intermediate), and Scheie syndrome (attenuated). Severe forms involve early neurodegeneration, skeletal abnormalities, and early mortality, while attenuated forms present later with milder symptoms like joint stiffness, corneal clouding, and cardiac issues, allowing longer life expectancy.
Among pathogenic IDUA variants, L490P and P533R are commonly linked to attenuated forms (Hurler-Scheie and Scheie). These mutations retain partial α-L-iduronidase activity, reducing systemic severity but still causing subtle neurological impairments, such as cognitive delays and attention deficits, due to GAG accumulation in the central nervous system (CNS).
Current treatments, including enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT), manage somatic symptoms but are less effective for CNS involvement due to limited enzyme penetration across the blood-brain barrier (BBB). Emerging therapies like improved ERT and gene therapy (GT) offer promise but remain expensive and require further validation for MPS I.
We employed molecular docking calculations on the catalytic site of the protein to guide medicinal chemists into synthesizing weak inhibitors that would act as 1st generation pharmacological chaperons (PC). We are also investigating the conformational changes of L490P and P533R mutants via molecular dynamics (MD) simulations.
Keywords: IDUA, MPS I, docking, MD simulations
