Thus we tested whether manipulation of ML204 cellular cholesterol levels that control SREBPs activation could alter the expression level of Pdro. Cholesterol loading was achieved by incubating cells with acetylated LDL in the presence of lipoprotein-deficient serum. We found that Pdro mRNA levels, monitored by real time RT-PCR, declined after LDLcholesterol loading. Pdro protein expression levels were also decreased upon LDL-cholesterol loading. Cholesterol depletion was achieved by metabolic inhibition of cholesterol synthesis in the absence of supplemental sterol, using compactin. Under these conditions, Pdro mRNA was slightly increased, whereas its protein expression was more clearly upregulated. This suggests that Pdro expression is further regulated at translational or post-translational level upon cholesterol depletion. Together, these results indicate that Pdro expression is regulated by cellular cholesterol levels. Precise understanding of the role of SREBPs in the regulation of C11orf59 expression is currently under investigation. The rodent orthologue of Pdro has been involved in controlling LE/LY dynamics, which in turn may affect LDL-derived cholesterol egress, as suggested in NPC disease. In this disease, the increased cellular free cholesterol content results form a lysosomal accumulation of LDL-derived cholesterol that causes the formation of abnormal lysosomal storage Ganciclovir organelles. Thus, we undertook confocal microscopy analysis of cellular filipin staining to investigate whether Pdro depletion has altered cellular free cholesterol distribution. In control cells, filipin staining was detected predominantly on perinuclear vesicular/granular network and on plasma membrane projections such as lamellipodia. Visualization of cell surface membranous structures is likely facilitated by membrane convolution that generates an increase in fluorescence intensity. This staining is consistent with the expected normal free cholesterol distribution, which includes enrichment in the plasma membrane, certain endosomes and part of the Golgi complex.