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

Abstract

NBP (nitrogen-containing bisphosphonate) drugs protect against excessive osteoclast-mediated bone resorption. After binding to bone mineral, they are taken up selectively by the osteoclasts and inhibit the essential enzyme FDPS (farnesyl diphosphate synthase). NBPs inhibit also growth of amoebae of Dictyostelium discoideum in which their target is again FDPS. A fusion protein between FDPS and GFP (green fluorescent protein) was found, in D. discoideum, to localize to peroxisomes and to confer resistance to the NBP alendronate. GFP was also directed to peroxisomes by a fragment of FDPS comprising amino acids 1–22. This contains a sequence of nine amino acids that closely resembles the nonapeptide PTS2 (peroxisomal targeting signal type 2): there is only a single amino acid mismatch between the two sequences. Mutation analysis confirmed that the atypical PTS2 directs FDPS into peroxisomes. Furthermore, expression of the D. discoideum FDPS–GFP fusion protein in strains of Saccharomyces cerevisiae defective in peroxisomal protein import demonstrated that import of FDPS into peroxisomes was blocked in a strain lacking the PTS2-dependent import pathway. The peroxisomal location of FDPS in D. discoideum indicates that NBPs have to cross the peroxisomal membrane before they can bind to their target.

Physiologic Activity of Bisphosphonates – Recent Advances

“…The soil-dwelling amoeba Dictyostelium discoideum is known for its remarkable life cycle, which makes it an ideal model organism to study a range of biological problems, such as the mechanisms of action of both first generation [171,172] and nitrogen-containing bisphosphonates [173]. These studies indicate that bisphosphonates are able to cross peroxisomal membranes before they can exert inhibitory action.…”

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

“…In Dictyostelium, two peroxisomal enzymes, the multifunctional enzyme MFE1 (Matsuoka et al, 2003) and citrate synthase CshA (Huang et al, 2004), have been well characterized, which have a C-terminal PTS-1 and an N-terminal PTS-2, respectively. Recently, Nuttall et al (2012) reported that Dictyostelium farnesyl diphosphate synthase possesses a nonapeptide closely related to that of PTS-2 and that it is a peroxisomal enzyme imported through the PTS-2 pathway. It has also been reported that fatty-acyl-CoA synthase B (FcsB) is transported to peroxisomes by mPTS (the targeting signal for peroxisomal membrane proteins) through the Pex19 machinery via the endoplasmic reticulum (ER) (Paschke et al, 2012).…”

Single Low Dose Bisphosphonate Treatment Enhances Osteogenesis in hMSCs By Exerting Epigenetic Changes

“…5,6 Bisphosphonates (BPs) are a class of drugs that are used to treat resorptive bone diseases like osteoporosis. 7 They mainly inhibit osteoclast action by different ways. They also have effect on other cells like osteoblasts, keratinocytes, fibroblasts and stem cells.…”