Structure and mechanism of a eukaryotic ceramide synthase complex

Area of Science:

• Biochemistry
• Structural Biology
• Molecular Biology

Background:

• Ceramide synthases (CerS) are crucial enzymes for synthesizing ceramides, vital lipids involved in numerous cellular processes.
• Dysregulation of ceramide metabolism is implicated in various metabolic diseases and cancers, making CerS attractive therapeutic targets.

Purpose of the Study:

• To elucidate the structural basis of eukaryotic ceramide synthase function.
• To provide a structural template for the rational design of CerS modulators.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was employed to determine the structure of the yeast CerS complex.
• The structure was solved for the complex comprising the catalytic Lac1 subunit and regulatory Lip1 subunit in the presence of the C26-CoA substrate.

Main Results:

• The yeast CerS holoenzyme was revealed to be a dimer of Lac1-Lip1 heterodimers.
• The structure identified a hydrophilic reaction chamber and a hydrophobic tunnel within Lac1 for substrate binding.
• Lip1 was shown to stabilize the acyl chain binding tunnel by interacting with Lac1's transmembrane region and luminal loop.
• A lateral opening on Lac1 was identified as a potential entry point for the sphingoid base.

Conclusions:

• The determined structure provides unprecedented insight into the mechanism of eukaryotic ceramide synthases.
• This structural information can guide the development of novel therapeutic agents targeting CerS for metabolic diseases and cancer treatment.