The p185 erbB2 protein is localized on cell organelles involved in cell motility

Abstract

In a previous paper, we have shown that the c-erbB-2-encoded protein p185erbB2 is localized on the brush border of the proximal tubule kidney cells. In invasive duct cell carcinomas, the labeling was most obvious on the villous plasma membrane protrusions. From these observations the hypothesis was raised that p185erbB2 could play a role in motility. To test this hypothesis, we quantified its distribution on the microvilli and plasma membrane protrusions and on the straight parts of the cell membrane after immunoelectron microscopy. These findings were compared with the localization on p185erbB2 overexpressing SK-BR-3 human breast cancer cells before and after stimulation of motility by treatment with conditioned medium from COLO-16 cells (CM), which is also able to induce chemotaxis of these cells in a Boyden chamber assay. In the invasive duct cell carcinomas, the number of gold particles was nine times higher at the plasma membrane protrusions than at the straight parts of the cell membrane. In untreated SK-BR-3 cells, p185erbB2 was similarly concentrated on the membrane of small microvilli and plasma membrane protrusions. Treatment of SK-BR-3 cells with CM leads to cell spreading, enlargement of the microvilli, formation of pseudopodia and chemotaxis. Aggregation of p185erbB2 at the plasma membrane protrusions and pseudopodia is observed on immunofluorescence light microscopy. The concentration of p185erbB2 is several times higher on these membrane extensions than on the straight parts after immunogold labeling. It is concluded that p185erbB2 is localized on cell organelles involved in motility, and it is suggested that the molecule plays a role in cell movement, providing the capacity of tumor cells to spread and metastasize.

Endocytosis and Sorting of ErbB2 and the Site of Action of Cancer Therapeutics Trastuzumab and Geldanamycin

“…To address this question and characterize trastuzumab and ErbB2 localization more precisely, we performed 1) quantitative immunoelectron microscopy using antibodies to detect either trastuzumab or the cytoplasmic tail of ErbB2 or to improve sensitivity in single labeling experiments, and 2) silver enhancement of 1 nm NG-trastuzumab. Surface-bound trastuzumab, like ErbB2 (see below) and in line with previous observations (De Potter and Quatacker, 1993;Hommelgaard et al, 2004), was enriched on microvillus-like protrusions, was found occasionally within clathrin-coated pits, and was absent from noncoated plasma membrane invaginations (Figure 8, A Figure 5B). Internalized trastuzumab was found mainly on small (Յ60 nm) tubules and vesicles adjacent to endosomal vacuoles and dispersed in the cytoplasm (Figure 8, C-E, and Table 1).…”

Association of the Ras to Mitogen-activated Protein Kinase Signal Transduction Pathway with Microfilaments

“…neu /ErbB2, which has been implicated in tumor cell metastasis, is proposed to play a role in the regulation of cell structure and motility (6). The receptor is concentrated on microvilli in SK-BR-3 breast cancer cells.…”

“…The receptor is concentrated on microvilli in SK-BR-3 breast cancer cells. Activation of its phosphorylation leads to cell spreading, enlargement of microvilli, formation of pseudopodia, and aggregation of the p185 at the plasma membrane protrusions and pseudopodia (6). A specific role for p185 neu /ErbB2 in these microfilament-dependent processes known to enhance metastatic capability of tumor cells was shown in p185 neuoverexpressing transfectants of NCI-H460 lung carcinoma cells (7).…”

Regulation of Breast Cancer Cell Repression and Differentiation by ErbB2 Ligand.

“…The association between the erbB2 receptor and motility in the SKBR-3 cell line has also been demonstrated in previous studies. A 50 kd protein isolated from COLO-16 cells, which has not been characterized but has been suggested to be a member of the heregulin family, stimulated motility of SKBR-3 cells (57) and aggregation of phosphorylated erbB2 receptor in pseudopodia and membrane ruffles (58). EGF has also been shown to induce formation of lamellopodia and act as a chemotactic agent for a metastatic mammary adenocarcinoma cell line derived from the rat (59).…”