Expression of WASP and Scar1/WAVE1 actin‐associated proteins is differentially modulated during differentiation of HL‐60 cells

Abstract

The Wiskott-Aldrich Syndrome (WAS) is a disease associated with mutations in the WAS gene and characterised by developmental defects in haematopoietic cells such as myeloid cells. The Wiskott-Aldrich Syndrome protein (WASP)-family includes Scar1 and WASP, which are key regulators of actin reorganization in motile cells. To understand the roles of Scar1 and WASP in myeloid cells and their cytoskeletal control in haematopoietic tissues, we have explored their expression during differentiation of the promyeloid cell line HL-60. Undifferentiated HL-60 cells expressed Scar1 and WASP, and differentiation to neutrophils, induced by retinoic acid or non-retinoid agent treatments, led to a decrease in the level of expression of Scar1, whereas WASP expression was unaffected. Differentiation to monocytes/macrophages, induced by phorbol ester treatment, resulted in a decreased expression of both proteins in the adherent mature cells. Vitamin D(3) treatment or cytochalasin D in combination with PMA treatment did not affect WASP expression suggesting that adhesion and cytoskeletal integrity were both essential to regulate WASP expression. Scar1 expression was regulated by differentiation, adhesion, and cytoskeletal integrity. Recently, WASP was found to colocalize with actin in the podosomes. In contrast, we show here that Scar1 did not localize with the podosomes in mature monocytes/macrophages. These observations show for the first time that modulation of Scar1 and WASP expression is a component of the differentiation program of myeloid precursors and indicate that WASP and Scar1 have different roles in mature myeloid cells.

A WAVE2-Abi1 complex mediates CSF-1-induced F-actin-rich membrane protrusions and migration in macrophages

“…Here, we found that WAVE2 was significantly expressed at the protein level in macrophages of human and mouse origin, whereas WAVE1 was detected at extremely low levels and only in the RAW/LR5 cell line. This observation is in agreement with the finding that WAVE1 protein expression was decreased upon differentiation of promyeloid cells into monocyte/macrophage-like cells (Launay et al, 2003).…”

Overexpression of human 27 kDa heat shock protein in laryngeal cancer cells confers chemoresistance associated with cell growth delay

“…5b). Considering the importance of actin Wlaments as part of the cytoskeleton for the proliferation and diVerentiation (Kubler et al 1991;Launay et al 2003;Searler et al 2004), the accumulated F-actin Wber might disturb the balance between polymerized F-actin and soluble G-actin, which can be monitored by the cytokinesis check point Fig. 5 Actin polymerization by HSP27 is related with chemoresistance.…”

N-WASP Involvement in Dorsal Ruffle Formation in Mouse Embryonic Fibroblasts

“…Antibodies were from the following sources: anti-Scar1 (Launay et al, 2003), anti-Scar2, anti-Scar3, and anti-p34Arc (Upstate Biotechnology, Lake Placid, NY), anti-N-WASP (kind gift of Pontus Aspenstrom, Uppsala, Sweden), horseradish peroxidase-conjugated secondary antibody anti-rabbit (Jackson ImmunoResearch Laboratories, West Grove, PA), goat anti-rabbit fluorescein isothiocyanate (FITC) and Alexa-488 conjugates (Invitrogen, Paisley, United Kingdom).…”