The α₁ integrin cytoplasmic tail interacts with phosphoinositides and interferes with Akt activation

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Integrin α1β1 is a key adhesion receptor binding collagen and laminin.
• It plays crucial roles in cell adhesion, cytoskeletal organization, and migration.
• The α1 integrin cytoplasmic tail (α1CT) has a unique structure with six lysine residues.

Purpose of the Study:

• To investigate the interaction between the α1CT and phosphoinositides.
• To identify the specific motif and residues involved in this interaction.
• To elucidate the role of this interaction in regulating α1β1 integrin activity.

Main Methods:

• Peptide-lipid interaction studies using the α1CT and phosphoinositides.
• Site-directed mutagenesis of the KIGFFKR motif within the α1CT.
• Analysis of cell adhesion, F-actin cytoskeleton formation, and integrin activation.
• Assessment of focal adhesion formation and kinase phosphorylation (FAK, AKT).

Main Results:

• The α1CT directly associates with phosphoinositides, notably phosphatidylinositol 3,4,5-trisphosphate (PI(3,4,5)P3).
• This ionic interaction is mediated by the KIGFFKR motif, particularly lysine 1171.
• Mutations in the KIGFFKR motif enhanced integrin-specific adhesion and F-actin assembly.
• Mutation of lysine 1171 increased cell surface α1β1 integrin levels and focal adhesion kinase phosphorylation, while decreasing AKT phosphorylation.

Conclusions:

• The KIGFFKR motif, especially lysine 1171, is critical for the dynamic regulation of α1β1 integrin.
• The interaction of α1CT with phosphoinositides contributes to regulating integrin activity.
• This interaction influences cell adhesion, cytoskeletal organization, and signaling pathways.