Scientists Find New Cellular Pathway Defect in Cystinosis

Scientists at The Scripps Research Institute (TSRI) in La Jolla, California, have identified a new cellular pathway that is affected in cystinosis, a rare genetic disorder that can result in eye and kidney damage. The findings, published recently by the journal EMBO Molecular Medicine, could eventually lead to new drug treatments for reducing or preventing the onset of renal failure in patients. “Life expectancy for infantile and juvenile forms of the disease is only 20 to 30 years, even in treated patients,” said Dr. Sergio Catz, an Associate Professor at TSRI. “Clearly, there is a need for additional treatment approaches.” Cystinosis is a so-called lysosomal storage disease, a class of genetically inherited disorders. These conditions are caused by dysfunction of lysosomes, sacs within cells that digest old or unused proteins and other macromolecules. Dr. Catz notes that lysosomes are the recycling centers of cells; when they don’t work properly, a toxic buildup of undigested material can result, and eventually lead to cell degeneration. Patients with cystinosis lack a protein called cystinosin, which is necessary for transporting the amino acid cystine out of the lysosome. Cystine accumulation leads to the formation of crystals in cells that can damage tissues and organs, especially the eyes and kidneys. Cystinosis is normally treated with a drug called cysteamine, which reacts with cystine to form other molecules that can be moved out of the lysosome via other transporter proteins. Doctors have long noticed, however, that while cysteamine successfully reduces cystine buildup in cells, it only lessens kidney damage in some, but not all, patients. This has led researchers to suspect that the disease disrupts more than one crucial cellular pathway.
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