A molecular switch that controls cell spreading and retraction

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Integrin signaling controls cell adhesion, migration, and proliferation, crucial for various physiological and pathological processes.
• The mechanisms by which integrin outside-in signaling dictates opposing cellular behaviors like spreading and retraction remain unclear.

Purpose of the Study:

• To elucidate the role of calpain cleavage of integrin beta(3) in regulating cell spreading and retraction.
• To identify the molecular players involved in switching integrin signaling outcomes.

Main Methods:

• Utilized mutant forms of integrin beta(3) (cleavage-resistant and constitutively cleaved) in Chinese hamster ovary cells.
• Investigated the impact of these mutants on cell spreading, clot retraction, and RhoA signaling.
• Assessed the binding of c-Src to integrin beta(3) and its effect on RhoA activity.

Main Results:

• Calpain cleavage of integrin beta(3) at Tyr(759) promotes cell retraction and inhibits cell spreading.
• A cleavage-resistant beta(3) mutant enhanced cell spreading but impaired clot retraction and RhoA signaling.
• A constitutively cleaved beta(3) mutant failed to mediate cell spreading, an effect rescued by RhoA pathway inhibition.
• Cleaved beta(3) did not bind c-Src, which is essential for integrin-induced cell spreading by inhibiting RhoA.

Conclusions:

• Calpain cleavage of integrin beta(3) at Tyr(759) acts as a critical switch, shifting integrin signaling from promoting cell spreading to inducing cell retraction.
• This cleavage releases c-Src-mediated inhibition of RhoA, thereby activating the RhoA pathway and driving cell retraction.
• Findings provide novel insights into the regulation of cell adhesion dynamics and have implications for diseases involving cell migration.