Context-dependent interactions among afadin, ZO-1, and actin filaments

Area of Science:

• Cell biology
• Molecular biology
• Biochemistry

Background:

• Afadin and ZO-1 are actin-binding scaffold proteins crucial for cell-cell junctions.
• Their binding partners are tightly regulated within cells, despite possessing multiple protein-binding motifs.

Purpose of the Study:

• To investigate the interactions among afadin, ZO-1, and actin filaments.
• To understand the regulation of these interactions in cells lacking typical cell-cell junctions.

Main Methods:

• Utilized EL and F9 non-epithelial cells lacking cellular junctions.
• Performed gene disruption analyses to study protein aggregation.
• Investigated protein colocalization using microscopy.
• Identified binding partners through co-localization studies and gene disruption.

Main Results:

• Afadin and ZO-1 colocalized independently with actin filaments in EL cells.
• Afadin and ZO-1 formed aggregates in F9 cells, independent of the cadherin-catenin complex.
• Nectin-2 localized to afadin aggregates, while JAM-C was identified as a ZO-1 binding partner.
• E-cadherin's extracellular domain inhibited aggregate formation; nectin-2 disruption showed JAM-C-bound ZO-1 preferentially interacts with afadin.

Conclusions:

• Afadin, ZO-1, and actin filament interactions are strictly regulated by cellular context.
• Specific membrane proteins (nectin-2, JAM-C) and cadherin-catenin complex influence afadin and ZO-1 aggregation.
• These findings elucidate the complex regulatory mechanisms governing scaffold protein interactions at cell junctions.