Ricerc@Sapienza

PDIA3 is a member of the protein disulfide isomerase family mainly found in the endoplasmic reticulum. Here, it modulates the folding of newly synthesized glycoproteins by means of its redox and chaperon activity promoting proper disulfide bond formation [1]. PDIA3 is ubiquitously expressed in all tissues although with different concentrations for each of them and it has distinct sub-cellular localizations. PDIA3 dysregulation is involved in several human pathologies including neurodegenerative and metabolic diseases, as well as in different types of cancer, in platelet aggregation and musculoskeletal disorders [2]. Considering PDIA3 flexible binding sites able to interact with a series of small ligands, e.g. flavonoids, I would characterize thermodynamic parameters, binding constants and effects on enzymatic activity of the interaction between PDIA3 and a flavonoids range [3]. So far, two flavonoids, silibinin and punicalagin, showed the ability to bind and modify PDIA3 properties in the micromolar range of concentration [4,5]. To verify if silibinin and punicalagin binding effects are only PDIA3­specific, it will be performed a comparative study between PDIA1 and PDIA3. Flavonoids binding and the effects on both proteins will be evaluated by quenching analysis of the protein intrinsic fluorescence, differential scanning calorimetry (DSC) and isothermal titration calorimetry (ITC) assays, whereas the disulfide-reductase activity will be assayed using dieosin glutathione disulfide. From preliminary studies the two flavonoids exhibit different behaviours on both PDIAs suggesting that the PDIA/flavonoid interactions involve different binding sites. Dynamic studies could elucidate the complex PDIA/flavonoid interplay. Silibinin and punicalagin ability to modulate PDIAs could be used in the treatment of diseases in which PDIAs are overexpressed or play important roles, and as adjuvant in chemotherapy promoting endoplasmic reticulum stress and apoptosis.