Palladin promotes assembly of non-contractile dorsal stress fibers through VASP recruitment

Abstract

BSTRACTStress fibers are major contractile actin structures in non-muscle cells where they have an important role in adhesion, morphogenesis and mechanotransduction. Palladin is a multidomain protein, which associates with stress fibers in a variety of cell types. However, the exact role of palladin in stress fiber assembly and maintenance has remained obscure, and whether it functions as an actin filament crosslinker or scaffolding protein was unknown. We demonstrate that palladin is specifically required for the assembly of non-contractile dorsal stress fibers, and is, consequently, essential for the generation of stress fiber networks and the regulation of cell morphogenesis in osteosarcoma cells migrating in a three-dimensional collagen matrix. Importantly, we reveal that palladin is necessary for the recruitment of vasodilator stimulated phosphoprotein (VASP) to dorsal stress fibers and that it promotes stress fiber assembly through VASP. Both palladin and VASP display similar rapid dynamics at dorsal stress fibers, suggesting that they associate with stress fibers as a complex. Thus, palladin functions as a dynamic scaffolding protein that promotes the assembly of dorsal stress fibers by recruiting VASP to these structures.

Actin-associated protein palladin promotes tumor cell invasion by linking extracellular matrix degradation to cell cytoskeleton

“…Because palladin is a cancer-associated scaffolding protein with considerably faster turnover than actin or α-actinin in membrane ruffles and FAs, the interaction identified here provides cells with a more dynamic mechanism for invadopodial MT1-MMP targeting (Endlich et al. , 2009; Gateva et al. , 2014).…”

“…Because palladin is a dynamic scaffold protein, with even 30-fold faster turnover than actin or α-actinin in filamentous actin (F-actin)–containing membrane structures, the identified interaction provides cells with a unique mechanism to endorse mesenchymal tumor cell invasion by dynamic coordination between ECM proteolysis and the cytoskeleton (Endlich et al. , 2009; Gateva et al. , 2014).…”

Bidirectional Interplay between Vimentin Intermediate Filaments and Contractile Actin Stress Fibers

“…Tm4 depletion inhibits myosin II recruitment to arc precursors and thus specifically disrupts arcs without affecting dorsal stress fibers, whereas palladin is required for dorsal stress fiber elongation (Tojkander et al, 2011;Gateva et al, 2014). Endogenous vimentin filaments concentrated at the perinuclear region in control cells as well as in palladin knockdown cells, which did not display dorsal stress fibers but contained ventral stress fibers and arcs.…”

The inner workings of stress fibers − from contractile machinery to focal adhesions and back

“…1A). Dorsal stress fibers are long, linear and non-contractile bundles of actin crosslinked by α-actinin, and composed of palladin and vasodilator-stimulated phosphoprotein (VASP) (Burnette et al, 2014;Gateva et al, 2014). They appear to be attached solely to the ventral membrane through focal adhesions at a single, discrete end, usually near the cell edges.…”