Browsing pathways

Zellweger syndrome (Cerebrohepatorenal syndrome; Cerebro-hepato-renal syndrome) phenotype is caused by mutations in any of several different genes involved in peroxisome biogenesis, Peroxins (PEX proteins, peroxisomal transport proteins) proteins 1,2,3,5,6,12,14, and 26. Peroxin proteins serve several functions including the recognition of cytoplasmic proteins that contain peroxisomal targeting signals (PTS) that tag them for transport by peroxismnal proteins to the peroxisome. Zellweger syndrome is characterized by accumulation of cholesterol in plasma, tissues and cerebrospinal fluid, decreased chenodeoxycholic acid and increased concentration of bile alcohols and their glyconjugates. Increased concentrations of cholestanol and apolipoprotein B are also observed in spinal fluid. Symptoms include dementia, psychiatric disturbances, pyramidal and/or cerebellar signs, and seizures.

The action of zoledronate on bone tissue is based partly on its affinity for hydroxyapatite, which is part of the mineral matrix of bone. Zoledronate also targets farnesyl pyrophosphate (FPP) synthase. Nitrogen-containing bisphosphonates such as zoledronate appear to act as analogues of isoprenoid diphosphate lipids, thereby inhibiting FPP synthase, an enzyme in the mevalonate pathway. Inhibition of this enzyme in osteoclasts prevents the biosynthesis of isoprenoid lipids (FPP and GGPP) that are essential for the post-translational farnesylation and geranylgeranylation of small GTPase signalling proteins. This activity inhibits osteoclast activity and reduces bone resorption and turnover. In postmenopausal women, it reduces the elevated rate of bone turnover, leading to, on average, a net gain in bone mass.