Kindlin Regulates Mechanosensitive Activation and Adhesion Assembly of Integrin beta6

Area of Science:

• Cell Biology
• Biochemistry
• Biophysics

Background:

• Integrin activation, crucial for cell adhesion and motility, involves both inside-out and outside-in signaling pathways.
• While integrin β1 and β3 mechanisms are known, the regulation of integrin β6 remains poorly understood.
• Mechanosensitive regulation of integrin β6 is critical for understanding cell behavior on compliant substrates.

Purpose of the Study:

• To elucidate the mechanosensitive regulation of integrin β6 activation and its role in cell migration.
• To identify the key molecular players involved in the inside-out signaling of integrin β6.
• To investigate how integrin β6 clustering and activation influence cell adhesion on soft materials.

Main Methods:

• Utilized a traction force-free RGD-membrane model system to observe integrin β6 behavior.
• Employed domain-swapping approaches to investigate the role of integrin cytoplasmic tails.
• Conducted in vitro pulldown and microscale thermophoresis assays to identify protein interactions.
• Assessed cell migration of AsPC-1 cells on soft polydimethylsiloxane (PDMS) substrates.

Main Results:

• Integrin β6 and RGD ligands initially colocalized, forming clusters that later dissipated, indicating dynamic regulation.
• A chimera of integrin β6 with integrin β1's cytoplasmic tail showed persistent clustering, suggesting inside-out signaling involvement.
• Kindlin2 was identified as a key cytoplasmic adapter specifically associating with integrin β6.
• Kindlin2 deficiency impaired integrin β6 activation and cell migration, which was rescued by additional kindlin2 or PIPK1.
• Strengthening the kindlin2-integrin β6 interaction stabilized active integrin β6 and promoted cell migration on soft PDMS.

Conclusions:

• Kindlin2-mediated inside-out activation of integrin β6 bypasses extracellular force-dependent signaling.
• This pathway regulates mechanosensitive adhesion assembly and cell migration on compliant substrates.
• The findings reveal a novel mechanism for integrin β6 regulation, distinct from force-dependent outside-in signaling.