Focal adhesion assembly and cell migration require myoferlin in PDAC cell lines

Pancreatic ductal adenocarcinoma (PDAC) has a dire prognosis due to late diagnosis and ineffective treatments. Myoferlin, a transmembrane protein, is overexpressed in PDAC and correlates with poor patient survival, making it a potential therapeutic target. Several reports indicated that myoferlin depletion in cancer cells reduced migration or metastatic dissemination, but they failed to provide a consistent mechanism. Understanding the biology behind the dissemination of PDAC is of outmost importance, as this disease is often diagnosed at an advanced stage. This study aims to further elucidate myoferlin's role in cell migration. Myoferlin expression in PDAC patients correlated with gene sets related to the actin cytoskeleton, and myoferlin knockdown in PDAC cell lines similarly affected these gene sets. Electron microscopy revealed that myoferlin depletion altered cytoskeleton ultrastructure. Immunofluorescence confirmed that myoferlin knockdown disorganized microfilaments, despite not altering β-actin abundance. Functionally, myoferlin depletion significantly reduced PDAC cell migration. While core machinery for actin polymerization/depolymerization and EMT markers remained unaffected, myoferlin knockdown increased the abundance of focal adhesion components. However, immunofluorescence showed a decrease in the number of functional focal adhesions, with paxillin accumulating in the cytosol. Cell migration relies on the dynamics of focal adhesions. The reduction in functional focal adhesions indicates that the cell has fewer points of attachment for migration. We suggest this impairment was linked to a significant decrease in clathrin heavy chain abundance and pointed to a disrupted clathrin-mediated endocytosis. This study highlights a novel role for myoferlin in focal adhesion recycling in PDAC and provides a consistent mechanism explaining how myoferlin contributes to PDAC cell migration, a significant event in metastatic dissemination, and reinforce its potential as a therapeutic target.