A.
Niemann-Pick type-C (NPC) disease is an inherited defect in lipid storage. In this disorder, cholesterol is not transported out of the lysosomes and instead accumulates in lysosomes of liver, brain, and lung, bringing about early death.
B.
NPC is the result of a mutation in either of two genes, NPC1 and NPC2 , essential to moving cholesterol out of the lysosome and into the cytosol, where it can be further metabolized.
C.
NPC1 encodes a transmembrane lysosomal protein, and NPC2 encodes a soluble protein.
D.
These proteins act in tandem to transfer cholesterol out of the lysosome and into the cytosol for further processing or metabolism.