A protein mutated in the rare human genetic disease, nephropathic intermediate cystinosis,[2][3] also called cystinosin (TC# 2.A.43.1.1), is encoded by the CTNS gene.
In cystinotic renal proximal tubules (RPTs), diminished cystinosin function appears to result in reduced reabsorption of solutes by other secondary transporters such as the Na+/Phosphate cotransporter, due to decreased expression of these other transport proteins.
[1][4] Evidence suggests that cystinosin transports cystine out of lysosomes in a pmf-dependent process.
[8] Both of these suppressors, when overexpressed, have been reported to influence retention of lumenal endoplasmic reticular proteins as well as glycosylation in the Golgi apparatus.
The Lec15 and Lec35 mutations are characterized by inefficient synthesis and utilization, respectively, of mannose-P-dolichol for glycolipid biosynthesis.