Stratifying fascin and cortactin function in invadopodium formation using inhibitory nanobodies and targeted subcellular delocalization

Invadopodia are actin-rich protrusions arising through the orchestrated regulation of precursor assembly, stabilization, and maturation, endowing cancer cells with invasive properties. Using nanobodies (antigen-binding domains of Camelid heavy-chain antibodies) as perturbators of intracellular functions and/or protein domains at the level of the endogenous protein, we examined the specific contribution of fascin and cortactin during invadopodium formation in MDA-MB-231 breast and PC-3 prostate cancer cells. A nanobody (K-d similar to 35 nM, 1:1 stoichiometry) that disrupts fascin F-actin bundling emphasizes the importance of stable actin bundles in invadopodium array organization and turnover, matrix degradation, and cancer cell invasion. Cortactin-SH3 dependent WIP recruitment toward the plasma membrane was specifically inhibited by a cortactin nanobody (K-d similar to 75 nM, 1:1 stoichiometry). This functional domain is shown to be important for formation of properly organized invadopodia, MMP-9 secretion, matrix degradation, and cancer cell invasion. Notably, using a subcellular delocalization strategy to trigger protein loss of function, we uncovered a fascin-bundling-independent role in MMP-9 secretion. Hence, we demonstrate that nanobodies enable high resolution protein function mapping in cells.-Van Audenhove, I., Boucherie, C., Pieters, L., Zwaenepoel, O., Vanloo, B., Martens, E., Verbrugge, C., Hassanzadeh-Ghassabeh, G., Vandekerckhove, J., Cornelissen, M., De Ganck, A., Gettemans, J. Stratifying fascin and cortactin function in invadopodium formation using inhibitory nanobodies and targeted subcellular delocalization.