The structural and functional role of the three tryptophan residues in Pin1

A structure-based approach to discover a potential isomerase Pin1 inhibitor for cancer therapy using computational simulation and biological studies

Peptidyl-prolyl cis/trans isomerase Pin1 occupies a prominent role in preventing the development of certain malignant tumors. Pin1 is considered a target for the treatment of related malignant tumors, so the identification of novel Pin1 inhibitors is particularly urgent. In this study, we preliminarily predicted eight candidates from FDA-approved drug database as the potential Pin1 inhibitors through virtual screening combined with empirical screening. Therefore, we selected these eight candidates and tested their binding affinity and inhibitory activity against Pin1 using fluorescence titration and PPIase activity assays, respectively. Subsequently, we found that four FDA-approved drugs showed good binding affinities and inhibition effects. In addition, we also observed that bexarotene can reduce cell viability in a dose-dependent and time-dependent manner and induce apoptosis. Finally, we inferred that residues K63, R68 and R69 are important in the binding process between bexarotene and Pin1. All in all, repurposing of FDA-approved drugs to inhibit Pin1 may provide a promising insight into the identification and development of new treatments for certain malignant tumors.

Spectroscopic and computational studies on the binding interaction between gallic acid and Pin1

Gallic acid (GA) is a natural ingredient in functional foods, which has various health-promoting and antitumour effects. Peptidyl-prolyl cis/trans isomerase Pin1 plays an important role in preventing the development of some malignant tumours. However, whether there was an interaction between Pin1 and GA remains unknown. In this work, the binding information of GA and Pin1 was investigated systematically using multiple spectral and computational methods. GA bound to Pin1 directly with moderate binding affinity in the order of 10⁴  mol/L, therefore decreasing the activity of Pin1. Also, the binding process of GA to Pin1 was driven through weak van der Waals forces, hydrogen bonds, and electrostatic forces. In addition, the important residues Lys63, Arg68, and Arg69 played a significant role in maintaining the binding stability between Pin1 and GA. Interestingly, GA reduced the activity of Pin1 by affecting its conformational characteristics. Our present work showed that GA binds to Pin1 and inhibits its activity, affecting its structural and functional properties, which may contribute to the therapy of Pin1-related diseases.

Rational design of PIN1 inhibitors for cancer treatment based on conformational diversity analysis and docking based virtual screening

The parvulin PIN1 (peptidyl-prolyl cis-trans isomerase NIMA-interacting 1), is the only enzyme capable of isomerizing prolines of phospho-Serine/Threonine-Proline motifs. PIN1 binds to a subset of proteins and plays an essential role in regulating protein function post-phosphorylation control. Furthermore, the activity of PIN1 regulates the outcome of the signalling of proline-directed kinases (e.g. MAPK, CDK, or GSK3) and thus regulates cell proliferation and cell survival. For these reasons, PIN1 inhibitors are interesting since they may have therapeutic implications for cancer. Several authors have already reported that the non-structural point mutation Trp34Ala prevents PIN1 from interacting with its downstream effector proteins. In this work, we characterized PIN1 structurally, intending to explore new inhibition targets for the rational design of pharmacological activity compounds. Through a conformational diversity analysis of PIN1, we identified and characterized a highly specific druggable pocket around the residue Trp34. This pocket was used in a high-throughput docking screening of 450,000 drug-like compounds, and the top 10 were selected for re-docking studies on the previously used conformers. Finally, we evaluated the binding of each compound by thermal shift assay and found four molecules with a high affinity for PIN1 and potential inhibitory activity. Through this strategy, we achieved novel drug candidates with the ability to interfere with the phosphorylation-dependent actions of PIN1 and with potential applications in the treatment of cancer.Communicated by Ramaswamy H. Sarma.

The association of rs2233679 in the PIN1 gene promoter with the risk of Coronary Artery Disease in Chinese female individuals

BACKGROUNDS

Vascular atherosclerosis leads to various cardiovascular and cerebrovascular diseases. Nitric oxide (NO) promotes vasodilatation and prevents Coronary Artery Disease (CAD). Pin1 suppresses NO production by down-regulating the activity of endothelial nitric oxide synthase (eNOS). Whether the genetic polymorphisms of the PIN1 gene (encoding Pin1) are implicated in CAD deserves investigations in human beings.

METHODS

A total of 210 CAD patients and control individuals (all females) were enrolled, and their genotypes of rs2233679 (-667C/T, a key SNP in the promoter of PIN1 gene) were sequenced. T-test, chi-square test, odds ratio (OR) and 95% confidence interval (95% CI) were calculated to evaluate Hardy-Weinberg equilibrium, varied genetic distribution and relative CAD risk.

RESULTS

The differences in age, BMI, triglyceride, total cholesterol, low-density and high density cholesterol between the CAD and control groups were not significant (all P>0.05), and Hardy-Weinberg equilibrium was observed in the two groups (both P>0.05). The frequency of -667T allele in the CAD group was higher than that in the control group. The genotype -667TT elicited a higher hazardous risk of CAD compared to the genotype -667CC (OR=1.85, 95% CI: 0.75-4.53) as well as the genotypes CC+CT (OR=1.97, 95% CI: 0.86-4.49).

CONCLUSIONS

We firstly show that the allele -667T in the PIN1 promoter may elicit a higher CAD-risk than -667C, and the -667TT genotype of PIN1 may be a new genetic biomarker for increased incidence of CAD. These novel observations put forward a new understanding of the PIN1-CAD genetic relationship in humans, potentially contributing to both cardiovascular and cerebrovascular disorders.

Insight into the structural stability of wild-type and histidine mutants in Pin1 by experimental and computational methods

Pin1, a polypeptide proline isomerase parvulin, plays a key role in Alzheimer's disease (AD), common tumors and cancers. Two conservative histidine residues, His59 and His157, are important for maintaining the stability of the PPIase domain. Hence multiple spectral and computational techniques were performed to investigate the potential mechanism of two histidine residues. Thermal denaturation indicated that both residues His59 and His157 are not sensitive to the lower temperatures, while residue His59 is more sensitive to the higher temperatures than residue His157. Acidic denaturation suggested that influences of both residues His59 and His157 to acidic stability were the difference from Pin1-WT. ANS and RLS spectra hinted that there was no significant effect on hydrophobic change and aggregation by histidine mutations. The GndHCl-induced denaturation implied that residues His59 and His157 contributed the most to the chemical stability. MD simulations revealed that residues His59 and His157 mutations resulted in that the hydrogen bond network of the dual histidine motif was destroyed wholly. In summary, these histidine residues play an important role in maintaining the structural stability of the PPIase domain.

Interaction between Pin1 and its natural product inhibitor epigallocatechin-3-gallate by spectroscopy and molecular dynamics simulations

The binding of epigallocatechin-3-gallate (EGCG) to wild type Pin1 in solution was studied by spectroscopic methods and molecular dynamics simulations in this research to explore the binding mode and inhibition mechanism. The binding constants and number of binding sites per Pin1 for EGCG were calculated through the Stern-Volmer equation. The values of binding free energy and thermodynamic parameters were calculated and indicated that hydrogen bonds, electrostatic interaction and Van der Waals interaction played the major role in the binding process. The alterations of Pin1 secondary structure in the presence of EGCG were confirmed by far-UV circular dichroism spectra. The binding model at atomic-level revealed that EGCG was bound to the Glu12, Lys13, Arg14, Met15 and Arg17 in WW domain. Furthermore, EGCG could also interact with Arg69, Asp112, Cys113 and Ser114 in PPIase domain.