Signature of N-terminal domain (NTD) structural re-orientation in NPC1 for proper alignment of cholesterol transport: Molecular dynamics study with mutation

Abstract

Synopsis: modeling study of cholesterol binding protein NPC1 AbstractThe lysosomal membrane protein NPC1 (Niemann-Pick type C1) and NPC2 (Niemann-Pick type C2) are main players of cholesterol control in lysosome and it is known that mutation on these proteins leads to cholesterol trafficking related disease, called Niemann-Pick disease type C (NPC) disease. The mutation R518W or R518Q on NPC1 is one of such disease-related mutations, causing reduced cholesterol transport by half, resulting in accumulation of cholesterol and lipids in late endosomal/lysosomal region of the cell. Even though there has been significant progress in understanding cholesterol transport by NPC1 in combination with NPC2, especially after the structural determination of full length NPC1 in 2016, many details such as interaction of full length NPC1 with NPC2, molecular motions responsible for cholesterol transport during and after this interaction, and structure and function relations of many mutations are still not well understood.We report the extensive molecular dynamics simulations to gain insight into the structure and motions of NPC1 lumenal domain for cholesterol transport and disease behind the mutation (R518W). It is found that the mutation induces structural shift of NTD (N-terminal domain), toward the loop region in MLD (middle lumenal domain), which is believed to play central role in interaction with NPC2 protein, such that the interaction with NPC2 protein might be less favorable compare to wild NPC1. Also, the simulation indicates the possible re-orientation of the NTD, aligning to form an internal tunnel, after receiving the cholesterol from NPC2 with wild NPC1 unlike the mutated one, a possible pose for further action in cholesterol trafficking.We believe the current study can provide better understanding on the cholesterol transport by NPC1, especially the role of NTD of NPC1, in combination with NPC2 interaction.