Enhanced selectivity for sulfatide by engineered human glycolipid transfer protein

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Medicine

Background:

• Human glycolipid transfer protein (GLTP) possesses a unique fold for lipid binding and transfer.
• Glycosphingolipids (GSLs) are crucial regulators of cellular processes including growth, division, adhesion, and neurodevelopment.

Purpose of the Study:

• To perform structure-guided engineering of GLTP to modify its lipid-binding properties.
• To investigate the molecular mechanisms underlying GLTP's selective lipid binding and translocation.

Main Methods:

• X-ray crystallography was used to determine the structures of wild-type GLTP, GLTP mutants, and GLTP-lipid complexes.
• Site-directed mutagenesis was employed to alter specific residues at the GLTP portal entrance.
• Analysis of crystal structures revealed conformational changes associated with lipid binding and encapsulation.

Main Results:

• Crystal structures of GLTP mutants (D48V and A47D‖D48V) bound to N-nervonoyl-sulfatide elucidated the basis for selective sulfatide anchoring.
• Mutations at residues A47 and D48 were shown to regulate sphingosine access to the hydrophobic pocket, potentially via homodimerization.
• Conformational changes involving phenylalanines within the hydrophobic pocket were observed during lipid encapsulation, as seen in apo-GLTP and GLTP-N-oleoyl-glucosylceramide complexes.

Conclusions:

• Engineered GLTP variants exhibit enhanced specificity for particular GSLs.
• Understanding GLTP's structure-function relationship provides a foundation for developing novel therapeutics targeting GSL-mediated diseases.