Laminin carbohydrates are implicated in cell signaling

Area of Science:

• Cell Biology
• Biochemistry
• Glycobiology

Background:

• Laminin is crucial for cell adhesion, but its role in subsequent cellular responses like spreading and neurite outgrowth is less understood.
• Previous studies indicated that unglycosylated laminin supports cell adhesion but fails to promote cell spreading or neurite outgrowth.

Purpose of the Study:

• To investigate the specific role of laminin carbohydrates in promoting cell spreading and neurite outgrowth.
• To determine if cellular responses could be restored using modified laminin structures.

Main Methods:

• Reconstitution experiments using mixtures of glycosylated and unglycosylated laminin.
• Enzymatic digestion (pronase) of laminin to isolate carbohydrate effects.
• Utilizing glycosylation inhibitors (swainsonine, castanospermine) to produce laminins with immature oligosaccharides.

Main Results:

• Cell spreading was restored when at least 30% glycosylated laminin was present, with maximal response at 65%.
• Pronase digests of glycosylated laminin, but not unglycosylated laminin, restored cell spreading, highlighting the role of carbohydrates.
• Laminins with immature oligosaccharides were as effective as fully processed laminins in promoting cell spreading and neurite outgrowth.

Conclusions:

• Laminin carbohydrates, rather than polypeptide sequences, are essential for cell spreading and neurite outgrowth.
• Substrate attachment of carbohydrate moieties is not required for these cellular responses.
• Laminin carbohydrates provide critical information for cells to transition from adhesion to spreading or neurite extension.