α-Actinin-4 enhances colorectal cancer cell invasion by suppressing focal adhesion maturation

Area of Science:

• Cell Biology
• Biochemistry
• Cancer Research

Background:

• Alpha-actinins (ACTNs) crosslink actin filaments in focal adhesions during cell migration.
• While ACTN1 and ACTN4 are ubiquitous isoforms, ACTN4 is implicated in enhancing cancer cell motility, invasion, and metastasis.
• The precise mechanism of ACTN4's role in cancer progression is not fully understood.

Purpose of the Study:

• To elucidate the mechanism by which ACTN4 enhances cancer cell motility and invasion.
• To investigate the differential roles of ACTN1 and ACTN4 in focal adhesion dynamics and maturation.
• To determine the interaction between ACTN4, ACTN1, and zyxin (ZYX) in regulating cell invasion.

Main Methods:

• Comparative analysis of focal adhesion formation and turnover in DLD-1 cells expressing ACTN1 versus ACTN4.
• Assessment of zyxin (ZYX) and paxillin (PAX) recruitment to focal adhesions.
• Biochemical assays using purified recombinant proteins to evaluate ZYX binding to ACTN1 and ACTN4.
• Functional assays involving Matrigel invasion of SW480 cells with altered ACTN expression.

Main Results:

• ACTN4 expression induced immature focal adhesions with rapid turnover in DLD-1 cells, unlike ACTN1.
• ZYX recruitment to focal adhesions was impaired in ACTN4-expressing cells, while PAX recruitment remained normal.
• Purified ACTN4 showed defective binding to ZYX compared to ACTN1.
• Ectopic ACTN1 expression inhibited Matrigel invasion in SW480 cells with high endogenous ACTN4.

Conclusions:

• ACTN4 impairs focal adhesion maturation by inhibiting ZYX recruitment, leading to enhanced cell motility and invasion.
• The defective binding of ZYX to ACTN4, as opposed to ACTN1, is a key mechanism driving malignant phenotypes.
• Targeting ACTN4 or promoting ACTN1 function may offer therapeutic strategies against cancer metastasis.