The non-redundant role of N-WASP in podosome-mediated matrix degradation in macrophages.
Wiskott-Aldrich Syndrome Protein (WASP) is a hematopoietic cell-specific regulator of Arp2/3-dependent actin polymerization. Despite the presence of the highly homologous N-WASP (neural-WASP), macrophages from WAS patients are devoid of podosomes, adhesion structures in cells of the monocytic lineage capable of matrix degradation via matrix metalloproteases (MMPs), suggesting that WASP and N-WASP play unique roles in macrophages. To determine whether N-WASP also plays a unique role in macrophage function, N-WASP expression was reduced using silencing RNA in a sub-line of RAW 264.7 macrophages (RAW/LR5). Similar to reduction in WASP levels, cells with reduced N-WASP levels were rounder and less polarized. Interestingly, podosomes still formed when N-WASP was reduced but they were unable to perform matrix degradation. This defect was rescued by re-expression of N-WASP, but not by over-expression of WASP, indicating that these proteins play distinct roles in podosome function. Additionally, reducing N-WASP levels mistargets the metalloprotease MT1-MMP and it no longer localizes to podosomes. However, N-WASP was only found to co-localize with MT1-MMP positive vesicles at podosomes, suggesting that N-WASP may play a role on the targeting or fusion of MMP-containing vesicles to podosomes in macrophage-like cells.
Nusblat
Leora M
LM
Anatomy and Structural Biology, Albert Einstein College of Medicine, Bronx, NY 10461, USA.
Dovas
Athanassios
A
Cox
Dianne
D
D000818:Animals; D022081:Cell Surface Extensions / Q000378:metabolism*; D003598:Cytoskeletal Proteins / Q000378:metabolism; D003599:Cytoskeleton / Q000378:metabolism*; D006801:Humans; D008264:Macrophages / Q000166:cytology / Q000378:metabolism*; D051379:Mice; D014162:Transfection; D051316:Wiskott-Aldrich Syndrome Protein / Q000235:genetics* / Q000378:metabolism*
D003598:Cytoskeletal Proteins; D051316:Wiskott-Aldrich Syndrome Protein