Structural and functional dissection of a higher-order oligomerization interface in yeast ceramide synthase

Area of Science:

• Biochemistry
• Structural Biology
• Cellular Metabolism

Background:

• Ceramide synthases (CerSs) are key enzymes in sphingolipid metabolism with therapeutic potential.
• Understanding CerS regulatory mechanisms is crucial for metabolic disorder treatments.
• The precise structural basis for CerS regulation remains largely unknown.

Purpose of the Study:

• To elucidate the structural organization and regulatory mechanism of yeast ceramide synthase (yCerS).
• To investigate the role of subunit interactions and oligomerization in controlling yCerS activity.

Main Methods:

• Cryo-electron microscopy (cryo-EM) to determine the high-resolution structure of the yCerS complex.
• Biochemical and functional assays to validate the structural findings and assess enzyme regulation.

Main Results:

• The structure reveals a 4:4 assembly of yCerS, formed by two Lac1-Lip1 subcomplexes.
• A specific interface involving twisted transmembrane helix TM8 of Lac1 sterically blocks the catalytic chamber.
• This oligomerization-dependent interface is essential for regulating ceramide output and cellular adaptation.

Conclusions:

• Yeast CerS employs a complex oligomerization-mediated regulatory mechanism.
• The 4:4 assembly and associated structural rearrangements control enzyme activity and substrate access.
• This study advances the mechanistic understanding of ceramide synthesis and its regulation.