Paxillin Phosphorylation Controls Invadopodia/Podosomes Spatiotemporal Organization

Abstract

In Rous sarcoma virus (RSV)-transformed baby hamster kidney (BHK) cells, invadopodia can self-organize into rings and belts, similarly to podosome distribution during osteoclast differentiation. The composition of individual invadopodia is spatiotemporally regulated and depends on invadopodia localization along the ring section: the actin core assembly precedes the recruitment of surrounding integrins and integrin-linked proteins, whereas the loss of the actin core was a prerequisite to invadopodia disassembly. We have shown that invadopodia ring expansion is controlled by paxillin phosphorylations on tyrosine 31 and 118, which allows invadopodia disassembly. In BHK-RSV cells, ectopic expression of the paxillin mutant Y31F-Y118F induces a delay in invadopodia disassembly and impairs their self-organization. A similar mechanism is unraveled in osteoclasts by using paxillin knockdown. Lack of paxillin phosphorylation, calpain or extracellular signal-regulated kinase inhibition, resulted in similar phenotype, suggesting that these proteins belong to the same regulatory pathways. Indeed, we have shown that paxillin phosphorylation promotes Erk activation that in turn activates calpain. Finally, we observed that invadopodia/podosomes ring expansion is required for efficient extracellular matrix degradation both in BHK-RSV cells and primary osteoclasts, and for transmigration through a cell monolayer.

Podosome-type adhesions and focal adhesions, so alike yet so different

“…Indeed, Src is also a main regulator of the disassembly of focal adhesions and podosomes ( ; Destaing , 2008et al Webb , 2004 ). A similar pattern has been observed in case of knock-down of many components of Luxenburg , 2006et al Destaing , 2008 podosome ring such as paxillin ( ), meaning that the incapacity to form ring or belt is the signature of a defect in Badowski , 2008 et al podosome type adhesion dynamics. Similarly to podosome distribution during osteoclast differentiation, in RSV-transformed BHK cells, invadopodia can also self-organize into rosettes and belts, under the control of tyrosine phosphorylation whereas in carcinoma cells invadopodia remain as individual structures.…”

“…The lack of paxillin phosphorylation, or calpain or Erk inhibition result in similar phenotype, suggesting that these proteins belong to the same regulatory pathways ( ). Surprisingly, this mechanism Badowski , 2008 et al seems to be quite similar in focal adhesions where paxillin also plays a major role in their disassembly ( ). Indeed, Zaidel-Bar , 2007 et al recent studies have demonstrated that the calpain family has a regulatory function in cell motility, partly through the capacity to down regulate integrin-mediated adhesion complexes ( ; ; ; ).…”

The Novel Adaptor Protein Tks4 (SH3PXD2B) Is Required for Functional Podosome Formation

“…And Src is also required for invadopodia formation in human breast cancer cells (Artym et al, 2006;Cortesio et al, 2008). In keeping with a role for Src in podosome/invadopodia formation, many Src substrates are obligate podosome components, including cortactin, AFAP110, paxillin, p130Cas, ASAP1, and dynamin (Baldassarre et al, 2003;Brabek et al, 2004;Gatesman et al, 2004;Webb et al, 2006;Bharti et al, 2007;Clark et al, 2007;Badowski et al, 2008).…”

EMT, the cytoskeleton, and cancer cell invasion

“…Both Src and cortactin are essential for invadopodia formation and their increased activity can be used as a potential marker for the onset of invadopodia formation [204,205]. Downstream targets of activated Src which are known to be essential for invadopodia formation and maintenance include cortactin, N-WASP, ArfGAPs like AMAP1/AMAP2, paxillin and Tks5/Fish [197,[206][207][208][209].…”