The Adaptor Protein AMOT Promotes the Proliferation of Mammary Epithelial Cells via the Prolonged Activation of the Extracellular Signal-Regulated Kinases

Abstract

The asymmetric organization of epithelial cells is a basic counter to cellular proliferation. However, the mechanisms whereby pro-growth pathways are modulated by intracellular factors that control cell shape are not well understood. This study demonstrates that the adaptor protein Amot, in addition to its established role in regulating cellular asymmetry, also promotes ERK1/2 dependent proliferation of mammary cells. Specifically, expression of Amot80, but not a mutant lacking its polarity protein interaction domain, enhances ERK1/2 dependent proliferation of MCF7 cells. Further, expression of Amot80 induces non-transformed MCF10A cells to overgrow as disorganized cellular aggregates in Matrigel. Conversely, Amot expression is required for proliferation of breast cancer cells in specific micro-environmental contexts that require ERK1/2 signaling. Thus, Amot is proposed to coordinate the dysregulation of cell polarity with the induction of neoplastic growth in mammary cells.

Amot130 Adapts Atrophin-1 Interacting Protein 4 to Inhibit Yes-associated Protein Signaling and Cell Growth

“…Inactivation of murine Amot results in early embryonic lethality from a lack of cell growth and migration of cells in the anterior visceral endoderm (4). Consistently, knockdown of Amot in zebrafish produces defects in endothelial migration (5) as well as reduced rates of cell proliferation in cultured epithelial cells (6,7) that have been attributed to loss of Amot80 (6). In contrast, Amot130 strongly inhibits the progrowth transcriptional co-activators YAP 2 and TAZ (transcriptional co-activator with PDZ-binding motif) (8,9).…”

Serum deprivation inhibits the transcriptional co-activator YAP and cell growth via phosphorylation of the 130-kDa isoform of Angiomotin by the LATS1/2 protein kinases

“…MCF10A cells were cultured in lrECM (Matrigel, 7.5 mg/mL or greater protein; BD Biosciences; 354230). Cell growth in three dimensions was carried out after plating 200 thousand MDA-MB-468 cells or 300 thousand MCF10A cells onto Matrigel, and colonies or acini were imaged with a stereomicroscope or confocal microscope as previously described (24). Cells were serumstarved in all cases with Opti-MEM Reduced Serum Medium (Gibco).…”

“…Amot associates with cell junctions and binds apical polarity proteins, which underlie its ability to control cell shape and migration (20)(21)(22)(23). The 130 kDa isoform of Amot (Amot130), unlike the 80-kDa isoform (Amot80) that promotes cell growth (24), binds and inhibits YAP through cytosolic sequestration (17,18) and by facilitating its degradation (25) in a manner that can be independent of YAP phosphorylation by LATS1/2 at residue Ser-127 (17,18).…”

The Amotl2 Gene Inhibits Wnt/β-Catenin Signaling and Regulates Embryonic Development in Zebrafish

“…These proteins have been demonstrated to play important roles in angiogenesis, cell mobility, cell polarity, and cell-cell junctions by regulating distinct signaling pathways (15)(16)(17)(18)(19)(20)(21)(22)(23)(24). Interestingly, it appears that each Motin family member in human and mice has two isoforms, long and short isoform (14), which function differently in physiological processes (17,(25)(26)(27)(28).…”