VCA nanobodies target N-WASp to reduce invadopodium formation and functioning.

Invasive cancer cells develop small actin-based protrusions called invadopodia, which perform a primordial role in metastasis and extracellular matrix remodelling. Neural Wiskott-Aldrich syndrome protein (N-WASp) is a scaffold protein which can directly bind to actin monomers and Arp2/3 and is a crucial player in the formation of an invadopodium precursor. Expression modulation has pointed to an important role for N-WASp in invadopodium formation but the role of its C-terminal VCA domain in this process remains unknown. In this study, we generated alpaca nanobodies against the N-WASp VCA domain and investigated if these nanobodies affect invadopodium formation. By using this approach, we were able to study functions of a selected functional/structural N-WASp protein domain in living cells, without requiring overexpression, dominant negative mutants or siRNAs which target the gene, and hence the entire protein. When expressed as intrabodies, the VCA nanobodies significantly reduced invadopodium formation in both MDA-MB-231 breast cancer and HNSCC61 head and neck squamous cancer cells. Furthermore, expression of distinct VCA Nbs (VCA Nb7 and VCA Nb14) in PC-3 prostate cancer cells resulted in reduced overall matrix degradation without affecting MMP9 secretion/activation or MT1-MMP localisation at invadopodial membranes. From these results, we conclude that we have generated nanobodies targeting N-WASp which reduce invadopodium formation and functioning, most likely via regulation of N-WASp-Arp2/3 complex interaction, indicating that this region of N-WASp plays an important role in these processes.

NKG2D- and CD28-mediated costimulation regulate CD8+ T cell chemotaxis through different mechanisms: the role of Cdc42/N-WASp.

The activating receptor NKG2D is mainly expressed in NK cells and CD8(+) T cells. NKG2D and CD28 recruit the p85 subunit of PI3K to propagate their signals through the YXXM signaling motif. The function of CD28 as a costimulatory molecule is well-established in T cells. Ligation of NKG2D on T cells costimulates TCR signaling, although the intracellular signaling pathways triggered by the two receptors may not be identical. In this study, we analyzed the function of the NKG2D receptor in human CD8(+) T cell chemotaxis toward a CXCL12 gradient. We found that costimulation of the TCR together with CD28 or NKG2D impairs cell migration, although the signaling pathways responsible for this effect differ. Whereas the Rho GTPase Rac1 is activated upon TCR and costimulation via CD28 and NKG2D, the activity of Cdc42 is increased only upon CD3/NKG2D activation. Moreover, knockdown of N-WASp expression with siRNA rescues migration rates after NKG2D-mediated costimulation but not after CD3/CD28 activation. CD28- and NKG2D-mediated costimulation induces cofilin activation by dephosphorylation. Inhibition of N-WASp by wiskostatin further decreases phosphorylation levels of cofilin, although this effect is especially severe upon CD3/NKG2D activation. Thus, our findings reveal new differences in the signaling pathways between CD28- and NKG2D-mediated costimulation in the regulation of cell chemotaxis in human CD8(+) T cells.