Talin2 mediates secretion and trafficking of matrix metallopeptidase 9 during invadopodium formation

Talin2 plays an important role in transduction of mechanical signals between extracellular matrix and actin cytoskeleton. Recent studies showed that talin2 is localized to invadopodia and regulates their maturation, subsequently cancer cell invasion and metastasis. However, the molecular mechanism whereby talin2 mediates invadopodium maturation is unknown. Here we show that ablation of talin2 in MDA-MB-231 cells inhibited the secretion of matrix metallopeptidase 9 (MMP9), a proteinase involved in extracellular matrix degradation in invadopodium maturation and metastasis. Furthermore, re-expression of talin2^WT in talin2-KO cells rescued MMP9 secretion, but talin2^S339C, a mutant with reduced β-integrin binding, did not, indicating that the talin2-β-integrin interaction is involved in the MMP9 secretion. Moreover, ablation of talin2 caused an accumulation of enlarged MMP9 vesicles. These vesicles co-localized with enlarged early, late endosomes and autophagosomes, suggesting talin2 controls MMP9 trafficking process. Therefore, these data suggest that talin2 regulates extracellular matrix degradation and invadopodium maturation by mediating MMP9 secretion.