Role for LAMP-2 in endosomal cholesterol transport.
Bottom Line: These results point to a critical role for LAMP-2 in endosomal/lysosomal cholesterol export.The LAMP-2 luminal domain, the membrane-proximal half in particular, was necessary and sufficient for the rescue effect.Taken together, our results suggest that LAMP-2, its luminal domain in particular, plays a critical role in endosomal cholesterol transport and that this is distinct from the chaperone-mediated autophagy function of LAMP-2.
Affiliation: Institute of Biochemistry, University of Kiel, Kiel, Germany.Show MeSH
Mentions: We showed previously that, in LAMP−/− MEFs, the filipin staining (detecting free cholesterol) was increased and the level of total cholesterol was approximately twofold higher than in wild-type MEFs . In LAMP-2 single deficient MEFs, the filipin staining intensity and cholesterol level were intermediate to wild-type and LAMP−/− MEFs. In order to test whether this phenotype would be observed in LAMP-2 deficient tissue, we investigated cholesterol levels in the liver of mice deficient in LAMP-1 or LAMP-2. Quantitative cholesterol assay showed that the level of total cholesterol was approximately twofold in the LAMP-2 deficient liver compared to the wild-type liver, whereas the level of LAMP-1 deficient liver was not different from the wild-type (Fig. 4A). Filipin, which only stains unesterified cholesterol, was used to check whether free cholesterol was increased in LAMP-2 deficient liver. Filipin staining of liver sections showed that LAMP-2 deficient liver accumulated unesterified cholesterol (Fig. 4A). The results indicate that, similar to LAMP-2 single deficient and LAMP double deficient MEFs, LAMP-2 deficiency leads to an accumulation of free cholesterol and increase in total cholesterol also in liver tissue. This finding suggests that LAMP-2 is more critical than LAMP-1 for the liver cholesterol homeostasis..
Affiliation: Institute of Biochemistry, University of Kiel, Kiel, Germany.