Paolo Paoli - Academia.edu (original) (raw)

Papers by Paolo Paoli

Marine Drugs, Sep 24, 2021

Biochemistry, May 1, 2007

Low molecular weight protein tyrosine phosphatases (LMW-PTPs) are small enzymes that are ubiquito... more Low molecular weight protein tyrosine phosphatases (LMW-PTPs) are small enzymes that are ubiquitous in many organisms. They are important in biological processes such as cell proliferation, adhesion, migration, and invasiveness. LMW-PTP is expressed in mammalian cells as two isoforms (IF1 and IF2) originating through alternative splicing. We have previously shown that IF2 targets lipid rafts called caveolae and interacts with caveolin-1, their major structural protein. Caveolae are cholesterol- and sphingolipid-rich membrane microdomains that have been implicated in a variety of cellular functions, including signal transduction events. Caveolin-1 contains a scaffolding region that contributes to the binding of the protein to the plasma membrane and mediates protein omo- and etero-oligomerization. Interaction of many signaling molecules with the scaffolding domain sequesters them into caveolae and inhibits or suppresses their activities. Caveolin-interacting proteins usually have a typical sequence motif, also present in all the LMW-PTPs, which is characterized by aromatic or large hydrophobic residues in specific positions. We have examined here the interaction of the LMW-PTP isoforms with caveolin-1 and its molecular mechanism, together with the consequences for their tyrosine phosphatase activities. We found that IF1 and IF2 are both capable of interacting with defined regions of caveolin-1 and that their putative caveolin binding sequence motif is not responsible for the association. The formation of LMW-PTP/caveolin-1 complexes is accompanied by modulation of the enzyme activities, and the inhibitory effect elicited against IF1 is stronger than that against IF2. The caveolin scaffolding domain is directly involved in the observed phenomena.

Free Radical Biology and Medicine, Apr 1, 2008

Recent data support the role of oxidative stress in the pathogenesis of Alzheimer disease (AD). I... more Recent data support the role of oxidative stress in the pathogenesis of Alzheimer disease (AD). In particular, glutathione (GSH) metabolism is altered and its levels are decreased in affected brain regions and peripheral cells from AD patients and in experimental models of AD. In the past decade, interest in the protective effects of various antioxidants aimed at increasing intracellular GSH content has been growing. Because much experimental evidence suggests a possible protective role of unsaturated fatty acids in age-related diseases, we designed the synthesis of new S-acylglutathione (acyl-SG) thioesters. S-Lauroylglutathione (lauroyl-SG) and S-palmitoleoylglutathione (palmitoleoyl-SG) were easily internalized into the cells and they significantly reduced Abeta42-induced oxidative stress in human neurotypic SH-SY5Y cells. In particular, acyl-SG thioesters can prevent the impairment of intracellular ROS scavengers, intracellular ROS accumulation, lipid peroxidation, and apoptotic pathway activation. Palmitoleoyl-SG seemed more effective in cellular protection against Abeta-induced oxidative damage than lauroyl-SG, suggesting a valuable role for the monounsaturated fatty acid. In this study, we demonstrate that acyl-SG derivatives completely avoid the sharp lipoperoxidation in primary fibroblasts from familial AD patients occurring after exposure to Abeta42 aggregates. Hence, we put forward these derivatives as new antioxidant compounds which could be excellent candidates for therapeutic treatment of AD and other oxidative stress-related diseases.

Biochimica Et Biophysica Acta - General Subjects, May 1, 2007

We mutated Trp 134 and Tyr 135 of the yeast LMW-PTP to explore their catalytic roles, demonstrati... more We mutated Trp 134 and Tyr 135 of the yeast LMW-PTP to explore their catalytic roles, demonstrating that the mutations of Trp 134 to Tyr or Ala, and Tyr 135 to Ala, all interfere with the formation of the phosphorylenzyme intermediate, a phenomenon that can be seen by the decrease in the kinetic constant of the chemical step (k 3). Furthermore, we noted that the Trp 134 to Ala mutation causes a dramatic drop in k cat /K m and a slight enhancement of the dissociation constant K s. The conservative mutant W134Y shows a k cat /K m very close to that of wild type, probably compensating the twofold decrease of k 3 with an increase in substrate affinity. The Y135A mutation enhances the substrate affinity, but reduces the enzyme phosphorylation rate. The replacement of Trp 134 with alanine interferes with the partition between phosphorylenzyme hydrolysis and phosphotransfer from the phosphorylenzyme to glycerol and abolish the enzyme activation by adenine. Finally, we found that mutation of Trp 134 to Ala causes a dramatic change in the pH-rate profile that becomes similar to that of the D132A mutant, suggesting that an aromatic residue in position 134 is necessary to assist the proper positioning of the proton donor in the transition state of the chemical step.

Molecular Carcinogenesis, Jan 16, 2019

Morin-dependent inhibition of low molecular weight protein tyrosine phosphatase (LMW-PTP) restore... more Morin-dependent inhibition of low molecular weight protein tyrosine phosphatase (LMW-PTP) restores sensitivity to apoptosis during colon carcinogenesis: studies in vitro and in vivo, in an Apc-driven model of colon cancer. †

Biochimica Et Biophysica Acta - Proteins And Proteomics, Oct 1, 2016

Originally identified as a low molecular weight acid phosphatase, LMW-PTP is actually a protein t... more Originally identified as a low molecular weight acid phosphatase, LMW-PTP is actually a protein tyrosine phosphatase that acts on many phosphotyrosine-containing cellular proteins that are primarily involved in signal transduction. Differences in sequence, structure, and substrate recognition as well as in subcellular localization in different organisms enable LMW-PTP to exert many different functions. In fact, during evolution, the LMW-PTP structure adapted to perform different catalytic actions depending on the organism type. In bacteria, this enzyme is involved in the biosynthesis of group 1 and 4 capsules, but it is also a virulence factor in pathogenic strains. In yeast, LMW-PTPs dephosphorylate immunophilin Fpr3, a peptidyl-prolyl-cis-trans isomerase member of the protein chaperone family. In humans, LMW-PTP is encoded by the ACP1 gene, which is composed of three different alleles, each encoding two active enzymes produced by alternative RNA splicing. In animals, LMW-PTP dephosphorylates a number of growth factor receptors and modulates their signalling processes. The involvement of LMW-PTP in cancer progression and in insulin receptor regulation as well as its actions as a virulence factor in a number of pathogenic bacterial strains may promote the search for potent, selective and bioavailable LMW-PTP inhibitors.

Journal of Neurochemistry, Jul 1, 2009

Cellular prion protein (PrPc) is a ubiquitous glycoprotein, whose physiological role is poorly ch... more Cellular prion protein (PrPc) is a ubiquitous glycoprotein, whose physiological role is poorly characterized. It has been suggested that PrPc participates in neuritogenesis, neuroprotection, copper metabolism, and signal transduction. In this study we detailed the intracellular events induced by PrPc antibody‐mediated cross‐linking in PC12 cells. We found a Fyn‐dependent activation of the Ras‐Raf pathway, which leads to a rapid and transient phosphorylation of extracellular regulated kinases. In addition, this activation cascade relies on the engagement of integrins, and involves focal adhesion kinase activation. We demonstrated the tyrosine phosphorylation of caveolin‐1 as a consequence of PrPc stimulation, and showed that phosphocaveolin‐1 scaffolds and coordinates protein complexes involved in PrPc‐dependent signaling. Moreover, we found that caveolin‐1 phosphorylation, is a mechanism for recruiting the C‐terminal Src kinase and inactivating Fyn, so as to terminate cell signaling. Furthermore our data support a significant role for PrPc as a response mediator in neuritogenesis and cell differentiation.

Biochimica et biophysica acta. Molecular cell research, Dec 1, 2013

Journal of Materials Chemistry B, Jun 7, 2016

To demonstrate the potential of azido-substituted carbon nanotubes for application in nanomedicin... more To demonstrate the potential of azido-substituted carbon nanotubes for application in nanomedicine, multiple-decorated oxidized multi-walled carbon nanotubes as drug delivery systems have been synthesized. These DDSs were able to carry doxorubicin inside breast MCF-7 cancer cell lines resulting in an enhanced cytotoxic effect with respect to the free drug. Decoration of the carbon nanotubes was accomplished through both covalent and non-covalent approaches: versatile click reactions and p-p interactions were exploited. To assess the internalization of the carbon nanotubes inside cells, decoration with a BODIPY fluorescent molecule was performed. Furthermore, the nanotubes were decorated with a biotin selector molecule to increase the uptake of the system by cancer cells. Comparative studies were performed on the complete drug delivery system to highlight its effect with respect to the free drug and the contribution of the selector in the internalization efficiency. Finally, preliminary in vivo tests were performed on MCF-7 inoculated mice. A net improvement in efficiency, concerning the minor growth of the tumors, has been found when using doxorubicin loaded on our drug delivery system with respect to free doxorubicin.

International Journal of Pharmaceutics, Apr 1, 2017

Batches of oxidized multiwalled carbon nanotubes differing in length were adopted to prepare two ... more Batches of oxidized multiwalled carbon nanotubes differing in length were adopted to prepare two drug delivery systems (DDS) loaded with doxorubicin. The different internalization of the two batches, verified by atomic emission spectroscopy onto cell lysates, was also confirmed by the different toxicity of the same DDS loaded with doxorubicin. In vitro experiments evidenced, after 48 h of incubation, the superior efficacy of the shortest nanotubes. However, upon prolonging the incubation time up to 72 h the difference in efficiency was minimized due to the spontaneous release of doxorubicin by the non-internalized long nanotubes.

European journal of medicinal chemistry, 2014

Insulin resistance is a complex altered metabolic condition characterized by impaired insulin sig... more Insulin resistance is a complex altered metabolic condition characterized by impaired insulin signaling and implicated in the pathogenesis of serious human diseases, such as diabetes, obesity, neurodegenerative pathologies. In pursuing our aim to identify new agents able to improve cellular insulin sensitivity, we have synthesized new 4-[(5-arylidene-4-oxo-2-phenylimino/oxothiazolidin-3-yl)methyl]benzoic acids (5, 8) and evaluated their inhibitory activity towards human protein tyrosine phosphatases PTP1B, LMW-PTP and TCPTP, enzymes which are involved in the development of insulin resistance. Compounds 5 and 8 showed from moderate to significant selectivity toward PTP1B over both the highly homologous TCPTP and the two isoforms of human LMW-PTP. In addition, most of the tested compounds selectively inhibited LMW-PTP IF1 over the isoform IF2. Docking studies into the active sites of PTP1B and LMW-PTP aided the rationalization of the observed PTP inhibitory profile. Moreover, most tested compounds were capable to induce the insulin metabolic pathway in mouse C2C12 skeletal muscle cells by remarkably stimulating both IRβ phosphorylation and 2-deoxyglucose cellular uptake.

Cancer Medicine, Mar 24, 2018

Tumor resistance to apoptosis is one the main causes of anticancer treatment failure. Previous st... more Tumor resistance to apoptosis is one the main causes of anticancer treatment failure. Previous studies showed that LMW-PTP overexpression enhances resistance of cancer cells to traditional anticancer drugs. Today, the role of LMW-PTP in inducing resistance to apoptosis in melanoma cells remains to be elucidated. Experimental setting include MTT assay, Annexin V/Pi method, and colony assay to assess whether silencing of LMW-PTP improves the sensitivity of A375 to dacarbazine, 5-FU, and radiotherapy. Pharmacological targeting of LMW-PTP was obtained using Morin, a LMW-PTP inhibitor. The ability of Morin to improve the effectiveness of anticancer drugs and radiotherapy was also studied. Moreover, PC3 cells were used as an alternative cellular model to confirm the data obtained with melanoma cells. We found that LMW-PTP silencing improves the effectiveness of dacarbazine, 5-FU, and radiotherapy. Identical results were obtained in vivo when Morin was used to target LMW-PTP. We demonstrated that Morin synergizes with dacarbazine, improving its cytotoxic activity. However, we showed that the combined treatment, Morin-anticancer drug, does not affect the viability of noncancerous cells. Knockdown of LMW-PTP sensitizes also PC3 cells to docetaxel and radiotherapy. In conclusion, we showed that LMW-PTP targeting improves effectiveness of anticancer drugs used for treatment of melanoma. Moreover, our results suggest that Morin could be used as adjuvant to improve the outcome of patients affected by metastatic melanoma.

Seminars in Oncology, Apr 1, 2014

Prostate cancer is no longer viewed mostly as a disease of abnormally proliferating epithelial ce... more Prostate cancer is no longer viewed mostly as a disease of abnormally proliferating epithelial cells, but rather as a disease affecting the complex interactions between the cells of the prostate epithelial compartment and the surrounding stromal compartment in which they live. Indeed, the microenvironment in which tumor cells evolve towards an aggressive phenotype is highly heterogeneous, as it is composed of different cell populations such as endothelial cells, fibroblasts, macrophages, and lymphocytes, either resident or trans-differentiated by bone marrow-derived mesenchymal stem cells recruited at the tumor site. Cancer-associated fibroblasts, the most abundant population within this microenvironment, exert a mandatory role in prostate cancer progression as they metabolically sustain cancer cell survival and growth, recruit inflammatory and immune cells, and promote cancer cells stemness and epithelial mesenchymal transition, thereby favoring metastatic dissemination of aggressive cancers. The interruption of this two-compartment crosstalk, together with the idea that stromal cells are mostly vulnerable, being drug-sensitive, could lead to the development of anticancer therapies that target tumor stromal elements.

Molecules, Aug 9, 2021

This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY

Organic & Biomolecular Chemistry

Towards human GCase activity enhancement by means of light responsive inhibitors.

Molecular Carcinogenesis, 2019

Chemoresistance is the primary cause of chemotherapy failure. Compelling evidence shows that micr... more Chemoresistance is the primary cause of chemotherapy failure. Compelling evidence shows that micro RNAs (miRNAs) contribute to reprogram cancer cells toward a resistant phenotype. We investigate the role of miRNAs in the response to acute treatment with 5-FU in colon cancer-resistant cells. We performed a global gene expression profile for the entire miRNA genome and found a change in the expression of four miRNAs following acute treatment with 5-FU. Among them, we focused on miR-210-3p, previously described as a key regulator of DNA damage repair mechanisms and mitochondrial metabolism. We show that miR-210-3p downregulation enables resistant cells to counteract the toxic effect of the drug increasing the expression of RAD-52 protein, responsible for DNA damage repair. Moreover, miR-210-3p downregulation enhances oxidative phosphorylation (OXPHOS), increasing the expression levels of succinate dehydrogenase subunits D, decreasing intracellular succinate levels and inhibiting HIF-1α expression. Altogether, these adaptations lead to increased cells survival following drug exposure. These evidence suggest that miR-210-3p downregulation following 5-FU sustains DNA damage repair and metabolic adaptation to counteract drug treatment.

Journal of Materials Chemistry B, 2019

A doxorubicin/metformin carrier for chemotherapy based on oxidized MWCNTs. Efficacy in vitro and ... more A doxorubicin/metformin carrier for chemotherapy based on oxidized MWCNTs. Efficacy in vitro and in vivo.

Food Chemistry, 2019

This paper investigates the phenolic composition of 17 monocultivar commercial coldpressed grape ... more This paper investigates the phenolic composition of 17 monocultivar commercial coldpressed grape seed oils. Chromatographic profiles showed the presence of more than 28 molecules, 11 of which were successfully identified by HPLC-DAD-MS-TOF and HPLC-FLD analysis. Pinoresinol, ethyl caffeate and ethyl gallate were detected for the first time in these oils. The total phenolic content ranged between 0.83 mg/kg for Viognier sample to 15.16 mg/kg for Merlot org sample. The detected ethyl esters can be suggested as markers to evaluate the intensity of fermentation in grape seeds before oil extraction, and to control the sensorial quality of the produced oils. In addition, the inhibitory power of these phenolic extracts against Protein Tyrosine Phosphatase 1B enzyme (PTP-1B), overexpressed in type-two diabetes, was investigated for the first time. Data highlighted a good correlation between total phenolic content and inhibitory power, with pinoresinol, p-coumaric acid and quercetin making the greater contributions.

Critical Reviews in Food Science and Nutrition, 2018

Regulation of glucose metabolism by bioactive phytochemicals for the management of type 2 diabete... more Regulation of glucose metabolism by bioactive phytochemicals for the management of type 2 diabetes mellitus.

Biochimica Et Biophysica Acta - General Subjects, Dec 1, 2018

Questa versione della pubblicazione è conforme a quanto richiesto dalle politiche dell'editore in... more Questa versione della pubblicazione è conforme a quanto richiesto dalle politiche dell'editore in materia di copyright. This version of the publication conforms to the publisher's copyright policies.