Chain-specific heparin-binding sequences in the laminin alpha chain LG45 modules

Area of Science:

• Biochemistry
• Cell Biology
• Molecular Biology

Background:

• Laminin alpha chains possess C-terminal globular modules (LG1-5).
• The LG45 module is crucial for binding heparin/heparan sulfate, mediating biological functions.

Purpose of the Study:

• To investigate the chain-specific heparin-binding affinity of laminin alpha chain LG45 modules.
• To identify and characterize heparin-binding sequences within the LG45 module, particularly of the alpha5 chain.

Main Methods:

• Assessed relative heparin-binding affinity of recombinant laminin alpha chain LG45 proteins.
• Screened heparin-binding sequences using recombinant alpha5LG45 protein and synthetic peptides.
• Utilized solid-phase assays to evaluate peptide heparin-binding activity.

Main Results:

• The heparin-binding affinity order was determined as alpha5 > alpha4 > alpha1 > alpha2 and alpha3.
• The alpha5 chain LG45 module demonstrated the strongest cell attachment.
• Four synthetic peptides (A5G71, A5G77, A5G81, A5G94) inhibited alpha5LG45 heparin-binding and showed dose-dependent heparin-binding activity.
• The alpha5 chain LG45 module contains four heparin-binding sequences, more than other alpha chains (alpha2/alpha3: one, alpha1/alpha4: two).
• Heparin-binding sequences are predominantly located in the N-terminal loop regions of the LG4 module.

Conclusions:

• The alpha5 chain LG45 module has the highest heparin-binding affinity and promotes cell attachment.
• Identified synthetic peptides represent functional heparin-binding sequences within the LG45 module.
• The N-terminal loop regions of the LG4 module are critical for heparin/heparan sulfate-mediated biological functions.