Expression of Gp78/Autocrine Motility Factor Receptor and Endocytosis of Autocrine Motility Factor in Human Thyroid Cancer Cells.

Gp78/autocrine motility factor receptor (Gp78/AMFR) is a cancer-associated endoplasmic reticulum-localized E3 ubiquitin ligase and also the cell surface receptor for autocrine motility factor (AMF). The study objective was to determine the association between Gp78/AMFR and AMF endocytosis in thyroid cancer cells. Gp78/AMFR expression and AMF internalization were measured in differentiated thyroid cancer (DTC) and anaplastic thyroid cancer (ATC) cell lines and in freshly resected human papillary thyroid cancers (PTC) relative to benign thyroid tissue.

Prognostic significance of autocrine motility factor receptor expression by colorectal cancer and lymph node metastases.

Background: Autocrine motility factor receptor (AMFR) has been linked to metastasis and tumorigenicity. The aim of this study was to evaluate expression and prognostic significance of AMFR in colorectal carcinoma.

Methods: AMFR expression was evaluated in 127 colon cancer specimens, 131 rectal cancer specimens, and 47 colonic and 25 rectal corresponding lymph node metastases.

Raft endocytosis of AMF regulates mitochondrial dynamics through Rac1 signaling and the Gp78 ubiquitin ligase.

Gp78 is a cell surface receptor that also functions as an E3 ubiquitin ligase in the endoplasmic reticulum (ER)-associated degradation (ERAD) pathway. The Gp78 ligand, the glycolytic enzyme phosphoglucose isomerase (PGI; also called autocrine motility factor, AMF), functions as a cytokine upon secretion by tumor cells. AMF is internalized through a PI3K- and dynamin-dependent raft endocytic pathway to the smooth ER; however, the relationship between AMF and Gp78 ubiquitin ligase activity remains unclear.

Cell type-dependent internalization of the Escherichia coli STb enterotoxin.

Previous studies have suggested that internalization of the Escherichia coli STb enterotoxin in human and rat intestinal epithelial cells is involved in STb pathogenesis, but toxin uptake in porcine jejunum epithelium, the in vivo target tissue, still remains elusive. Using flow cytometry, we studied the internalization of fluorescein isothiocyanate-labelled STb in porcine intestinal epithelial IPEC-J2 and murine fibroblast NIH-3T3 cell lines. In contrast to the selective pronase resistance of STb in NIH-3T3 cells at 37 °C, but not at 4 °C, indicative of toxin internalization, most of the toxin was pronase-sensitive at both temperatures in IPEC-J2 cells, indicating reduced uptake, but significant cell surface binding.

Caveolin-1 regulation of dynamin-dependent, raft-mediated endocytosis of cholera toxin-B sub-unit occurs independently of caveolae.

Ganglioside GM1-bound cholera toxin-B sub-unit (CT-b) enters the cell via clathrin-coated pits and dynamin-independent non-caveolar raft-dependent endocytosis. Caveolin-1 (Cav1), associated with caveolae formation, is a negative regulator of non-caveolar raft-dependent endocytosis. In mammary epithelial tumour cells deficient for Mgat5, Cav1 is stably expressed at levels below the threshold for caveolae formation, forming stable oligomerized Cav1 microdomains or scaffolds that were shown to suppress EGFR signalling and reduce the plasma membrane diffusion rate of both EGFR and CT-b.

Raft-dependent endocytosis of autocrine motility factor/phosphoglucose isomerase: a potential drug delivery route for tumor cells.

Background: Autocrine motility factor/phosphoglucose isomerase (AMF/PGI) is the extracellular ligand for the gp78/AMFR receptor overexpressed in a variety of human cancers. We showed previously that raft-dependent internalization of AMF/PGI is elevated in metastatic MDA-435 cells, but not metastatic, caveolin-1-expressing MDA-231 cells, relative to non-metastatic MCF7 and dysplastic MCF10A cells suggesting that it might represent a tumor cell-specific endocytic pathway.

Methodology/principal Findings: Similarly, using flow cytometry, we demonstrate that raft-dependent endocytosis of AMF/PGI is increased in metastatic HT29 cancer cells expressing low levels of caveolin-1 relative to metastatic, caveolin-1-expressing, HCT116 colon cells and non-metastatic Caco-2 cells.

Phosphorylated caveolin-1 regulates Rho/ROCK-dependent focal adhesion dynamics and tumor cell migration and invasion.

Rho/ROCK signaling and caveolin-1 (Cav1) are implicated in tumor cell migration and metastasis; however, the underlying molecular mechanisms remain poorly defined. Cav1 was found here to be an independent predictor of decreased survival in breast and rectal cancer and significantly associated with the presence of distant metastasis for colon cancer patients. Rho/ROCK signaling promotes tumor cell migration by regulating focal adhesion (FA) dynamics through tyrosine (Y14) phosphorylation of Cav1.

Concerted regulation of focal adhesion dynamics by galectin-3 and tyrosine-phosphorylated caveolin-1.

Both tyrosine-phosphorylated caveolin-1 (pY14Cav1) and GlcNAc-transferase V (Mgat5) are linked with focal adhesions (FAs); however, their function in this context is unknown. Here, we show that galectin-3 binding to Mgat5-modified N-glycans functions together with pY14Cav1 to stabilize focal adhesion kinase (FAK) within FAs, and thereby promotes FA disassembly and turnover. Expression of the Mgat5/galectin lattice alone induces FAs and cell spreading.

Raft-dependent endocytosis of autocrine motility factor is phosphatidylinositol 3-kinase-dependent in breast carcinoma cells.

Autocrine motility factor (AMF) is internalized via a receptor-mediated, dynamin-dependent, cholesterol-sensitive raft pathway to the smooth endoplasmic reticulum that is negatively regulated by caveolin-1. Expression of AMF and its receptor (AMFR) is associated with tumor progression and malignancy; however, the extent to which the raft-dependent uptake of AMF is tumor cell-specific has yet to be addressed. By Western blot and cell surface fluorescence-activated cell sorter (FACS) analysis, AMFR expression is increased in tumorigenic MCF7 and metastatic MDA-231 and MDA-435 breast cancer cell lines relative to dysplastic MCF10A mammary epithelial cells.