Vasoinhibin comprises a three-helix bundle and its antiangiogenic domain is located within the first 79 residues

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Vasoinhibin is an angiogenesis inhibitor derived from prolactin (PRL) via proteolytic cleavage.
• The antiangiogenic activity arises from conformational changes in PRL, but vasoinhibin's structure and bioactive domain remain undefined.
• Understanding vasoinhibin's structure is crucial for developing novel antiangiogenic therapies.

Purpose of the Study:

• To elucidate the solution structure of vasoinhibin and identify its bioactive domain.
• To investigate the structural basis for vasoinhibin's antiangiogenic properties.
• To explore the potential of smaller vasoinhibin variants in therapeutic applications.

Main Methods:

• Molecular dynamic (MD) simulations were employed to model vasoinhibin's structure.
• Recombinant proteins representing key structural domains were synthesized.
• In vitro assays assessed endothelial cell proliferation, migration, and gene expression.

Main Results:

• MD simulations revealed that loss of PRL's H4 helix induces molecular compression into a three-helix bundle, burying the hydrophobic core.
• This compression involves loop 1 (L1) interacting with α-helix 1 (H1), forming a distinct bioactive domain.
• A recombinant 79-amino acid protein (H1-L1) demonstrated significant antiangiogenic activity, comparable to full-length vasoinhibin.
• This smaller variant upregulated vasoinhibin target genes IL1A and ICAM1.

Conclusions:

• Vasoinhibin's structure is characterized by a compressed three-helix bundle formed after H4 removal.
• The N-terminal region (H1-L1) constitutes a novel, smaller bioactive domain with antiangiogenic properties.
• These findings expand the vasoinhibin family and offer insights for developing targeted antiangiogenic drugs.