Farnesyl diphosphate synthase, the target for nitrogen-containing bisphosphonate drugs, is a peroxisomal enzyme in the model system Dictyostelium discoideum

Insights about the structure of farnesyl diphosphate synthase (FPPS) and the activity of bisphosphonates on the proliferation and ultrastructure of Leishmania and Giardia

Background

The enzyme farnesyl diphosphate synthase (FPPS) is positioned in the intersection of different sterol biosynthesis pathways such as those producing isoprenoids, dolichols and ergosterol. FPPS is ubiquitous in eukaryotes and is inhibited by nitrogen-containing bisphosphonates (N-BP). N-BP activity and the mechanisms of cell death as well as damage to the ultrastructure due to N-BP has not yet been investigated in Leishmania infantum and Giardia. Thus, we evaluated the effect of N-BP on cell viability and ultrastructure and then performed structural modelling and phylogenetic analysis on the FPPS enzymes of Leishmania and Giardia.

Methods

We performed multiple sequence alignment with MAFFT, phylogenetic analysis with MEGA7, and 3D structural modelling for FPPS with Modeller 9.18 and on I-Tasser server. We performed concentration curves with N-BP in Leishmania promastigotes and Giardia trophozoites to estimate the IC₅₀via the MTS/PMS viability method. The ultrastructure was evaluated by transmission electron microscopy, and the mechanism of cell death by flow cytometry.

Results

The nitrogen-containing bisphosphonate risedronate had stronger anti-proliferative activity in Leishmania compared to other N-BPs with an IC₅₀ of 13.8 µM, followed by ibandronate and alendronate with IC₅₀ values of 85.1 µM and 112.2 µM, respectively. The effect of N-BPs was much lower on trophozoites of Giardia than Leishmania (IC₅₀ of 311 µM for risedronate). Giardia treated with N-BP displayed concentric membranes around the nucleus and nuclear pyknosis. Leishmania had mitochondrial swelling, myelin figures, double membranes, and plasma membrane blebbing. The same population labelled with annexin-V and 7-AAD had a loss of membrane potential (TMRE), indicative of apoptosis. Multiple sequence alignments and structural alignments of FPPS proteins showed that Giardia and Leishmania FPPS display low amino acid identity but possess the conserved aspartate-rich motifs.

Conclusions

Giardia and Leishmania FPPS enzymes are phylogenetically distant but display conserved protein signatures. The N-BPs effect on FPPS was more pronounced in Leishmania than Giardia. This might be due to general differences in metabolism and differences in the FPPS catalytic site.

Identifying a combined biomarker for bisphosphonate-related osteonecrosis of the jaw

BACKGROUND

For this study, the aim was to identify combined biomarkers associated with bisphosphonate-related osteonecrosis of the jaw (BRONJ).

MATERIALS AND METHODS

Microarray data for GSE7116 were downloaded from the Gene Expression Omnibus database, which contains 26 samples, including without ONJ, and 5 healthy volunteers. The combined biomarkers were identified using principal component analysis, and the pathway enrichment analyses were performed using the DAVID online tool.

RESULTS

Two hundred differently expressed genes between groups were detected according to the significances. From functional annotation, Y-box binding protein 1 and heterogeneous nuclear ribonucleoprotein C were found to be included in the most significant 10 pathways. Ten combined gene sets were identified that were effective in classifying multiple myeloma (MM) with ONJ and MM without ONJ.

CONCLUSION

Identifying combined gene expression profiles is expected to contribute to more personalized management of BRONJ and to improve existing therapies, and it will be helpful in finding new therapies by identifying more predictive biomarkers.

Regulation of local bone remodeling mediated by hybrid multilayer coating embedded with hyaluronan-alendronate/BMP-2 nanoparticles on Ti6Al7Nb implants

Osteoporosis, a common bone disease, has been identified as a major obstacle for successful implantation. Therefore, the promotion of early mechanical fixation between implants and the surrounding bone can strongly increase the success rate of orthopedic operation in osteoporosis patients. In this study, functional hyaluronan-alendronate/BMP-2 (HA-Aln/BMP-2) nanoparticles were embedded into the Gel/Chi multilayers on Ti6Al7Nb surfaces (namely Ti6Al7Nb/LBL/NP) to endow the Ti6Al7Nb-based implant with local anti-osteoporosis properties. The release test showed that the loaded BMP-2 only slowly released along with the degradation of multilayers, and no burst release emerged at the early stage. In vitro cell experiments, including cell morphology, viability, alkaline phosphatase (ALP) activity, mineralization capacity and tartrate-resistant acid phosphatase (TRAP), demonstrated that the prepared Ti6Al7Nb/LBL/NP implants not only improved the proliferation and differentiation of osteoblasts but also inhibited the maturity of osteoclasts. Moreover, the in vivo tests of the push-out test, micro-CT and histological stains further verified that the Ti6Al7Nb/LBL/NP implant was more beneficial to promoting the local osseointegration between the natural bone and the implant when compared to those of the control groups after implantation for 3 months in osteoporotic rabbits. The study demonstrated a flexible method for effectively enhancing the early osseointegration between the implant and the native osteoporotic bone.

Physiologic Activity of Bisphosphonates – Recent Advances

Background:

Bisphosphonates are drugs commonly used for the medication and prevention of diseases caused by decreased mineral density. Despite such important medicinal use, they display a variety of physiologic activities, which make them promising anti-cancer, anti-protozoal, antibacterial and antiviral agents.

Objective:

To review physiological activity of bisphosphonates with special emphasis on their ongoing and potential applications in medicine and agriculture.

Method:

Critical review of recent literature data.

Results:

Comprehensive review of activities revealed by bisphosphonates.

Conclusion:

although bisphosphonates are mostly recognized by their profound effects on bone physiology their medicinal potential has not been fully evaluated yet. Literature data considering enzyme inhibition suggest possibilities of far more wide application of these compounds. These applications are, however, limited by their low bioavailability and therefore intensive search for new chemical entities overcoming this shortage are carried out.

Dictyostelium acetoacetyl-CoA thiolase is a dual-localizing enzyme that localizes to peroxisomes, mitochondria and the cytosol

Acetoacetyl-CoA thiolase is an enzyme that catalyses both the CoA-dependent thiolytic cleavage of acetoacetyl-CoA and the reverse condensation reaction. In Dictyostelium discoideum, acetoacetyl-CoA thiolase (DdAcat) is encoded by a single acat gene. The aim of this study was to assess the localization of DdAcat and to determine the mechanism of its cellular localization. Subcellular localization of DdAcat was investigated using a fusion protein with GFP, and it was found to be localized to peroxisomes. The findings showed that the targeting signal of DdAcat to peroxisomes is a unique nonapeptide sequence (15RMYTTAKNL23) similar to the conserved peroxisomal targeting signal-2 (PTS-2). Cell fractionation experiments revealed that DdAcat also exists in the cytosol. Distribution to the cytosol was caused by translational initiation from the second Met codon at position 16. The first 18 N-terminal residues also exhibited function as a mitochondrial targeting signal (MTS). These results indicate that DdAcat is a dual-localizing enzyme that localizes to peroxisomes, mitochondria and the cytosol using both PTS-2 and MTS signals, which overlap each other near the N-terminus, and the alternative utilization of start codons.

Genetic investigation of bisphosphonate-related osteonecrosis of jaw (BRONJ) via whole exome sequencing and bioinformatics

Complications associated with the use of bisphosphonate (BP) have risen over the years due to an increase in the prescription of BP. BP-related osteonecrosis of jaw (BRONJ), one of the complications linked to the consumption of BP, greatly affects patients with minor dental trauma, incurring a long healing period. While BRONJ afflicts only a minority of patients prescribed with BP, BRONJ is a multigenic disease affected both by environmental and genetic factors having a distinctive phenotype. This study aims to discover genetic biomarkers associated with BRONJ via whole exome sequencing (WES) followed by statistical analysis. Sixteen individuals who had been prescribed with bisphosphonate medication and diagnosed as BRONJ were chosen and each individual’s saliva sample was collected for WES. 126 randomized subsamples from the GSK project representing 109 male and 17 female Koreans were used as a control data set. Fisher’s exact test was carried out to assess the significance of genetic variants in BRONJ patients. Gene set enrichment analysis (GSEA) (DAVID Bioinformatics Resource 6.7) was used to perform a cluster analysis of variants found from Fisher‘s exact test. The results from this study suggest that BRONJ-inducing factors are genetically associated and BRONJ occurs due to the malfunctioning of post-translational modification in osteoclast leading to the impairment of cell morphology and adhesion.