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EF-hand domains of MCFD2 mediate interactions with both LMAN1 and coagulation factor V or VIII

Chunlei Zheng1, Hui-hui Liu, Jiahai Zhou

  • 1Genomic Medicine Institute, Lerner Research Institute, Cleveland Clinic Foundation, OH 44195, USA.

Blood
|December 17, 2009
PubMed

Insights

Mutations in MCFD2 cause a bleeding disorder by disrupting the LMAN1-MCFD2 cargo receptor. The EF-hand domains of MCFD2 bind LMAN1 and factor V/VIII, crucial for protein transport.

Area of Science:

  • Molecular Biology
  • Biochemistry
  • Genetics

Background:

  • Combined deficiency of factor V and factor VIII (F5F8D) is a rare bleeding disorder.
  • Mutations in LMAN1 or MCFD2 genes cause F5F8D.
  • LMAN1 and MCFD2 form a calcium-dependent cargo receptor essential for FV/FVIII transport.

Purpose of the Study:

  • To investigate the structural and functional domains of MCFD2 involved in LMAN1 and FV/FVIII binding.
  • To elucidate the role of calcium-induced folding in MCFD2-LMAN1 interactions.
  • To understand the mechanism of cargo receptor formation and loading in the ER.

Main Methods:

  • Site-directed mutagenesis of MCFD2.
  • Analysis of LMAN1-binding and FV/FVIII-binding activities.
  • Circular dichroism spectroscopy to study protein folding and calcium-induced conformational changes.

Main Results:

  • The C-terminal EF-hand domains of MCFD2 are necessary and sufficient for LMAN1 interaction.
  • Calcium-induced folding of EF-hand domains is critical for LMAN1 binding.
  • MCFD2 binds FV/FVIII independently of calcium-induced folding, suggesting distinct binding sites.
  • Mutations disrupting LMAN1 binding do not affect FV/FVIII binding.

Conclusions:

  • MCFD2 EF-hand domains possess separate binding sites for LMAN1 and FV/FVIII.
  • These distinct sites are crucial for cargo receptor assembly and efficient FV/FVIII ER-to-Golgi transport.
  • Understanding these interactions may inform therapeutic strategies for F5F8D.

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