Structural insights into human ABCA7-mediated lipid transport

Area of Science:

• Biochemistry
• Structural Biology
• Neuroscience

Background:

• The ATP-binding cassette transporter ABCA7 is implicated in apolipoprotein E lipidation.
• Apolipoprotein E is a known risk factor for Alzheimer's disease (AD).
• The precise role of ABCA7 in AD molecular pathogenesis is not well understood.

Purpose of the Study:

• To elucidate the structural basis of ABCA7 function in lipid binding and transport.
• To investigate the interaction between ABCA7 and apolipoprotein E.
• To understand the biochemical link between ABCA7 variants and Alzheimer's disease.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine ABCA7 structures.
• Biochemical activity assays to assess lipid binding and transport.
• Pull-down assays to confirm protein-protein interactions.

Main Results:

• Determined cryo-EM structures of ABCA7 in apo and substrate-bound states.
• Identified specific residues responsible for binding two phosphatidylserine (PS) molecules in a tail-to-tail orientation.
• Confirmed direct interaction between ApoE and ABCA7, enhancing ABCA7's ATPase and lipid transport activities.
• Assessed the activity of familial AD and protective ABCA7 variants.

Conclusions:

• Provided structural insights into ABCA7-mediated phosphatidylserine translocation.
• Established the first biochemical evidence linking ABCA7 to Alzheimer's disease through lipid transfer to apolipoprotein E.