Structure of a mammalian sperm cation channel complex

Area of Science:

• Sperm biology
• Ion channel structure
• Molecular and Cellular Biology

Background:

• The cation channel of sperm (CatSper) is vital for sperm motility and male fertility.
• CatSper is a complex of pore-forming proteins (CATSPER1-4) and auxiliary subunits.

Purpose of the Study:

• To determine the cryo-electron microscopy (cryo-EM) structure of the mouse CatSper complex.
• To elucidate the assembly and organization of the CatSper complex and associated proteins.

Main Methods:

• Cryo-electron microscopy (cryo-EM) was used to obtain the structure of the CatSper complex from mouse sperm.
• Analysis of the EM map to identify protein components and their arrangement.

Main Results:

• The structure reveals a counterclockwise arrangement of CATSPER1-4, consistent with voltage-gated ion channels.
• Auxiliary subunits (CATSPERβ, γ, δ, ε) form a pavilion-like structure stabilizing the complex.
• The organic anion transporter SLCO6C1 was identified as a component, forming an ultracomplex named CatSpermasome.

Conclusions:

• The determined CatSpermasome structure provides unprecedented detail on its assembly and organization.
• This structural insight is foundational for developing targeted treatments for male infertility.
• The findings pave the way for novel non-hormonal contraceptive strategies.