Subcellular localization of aquaporin 3 in prostate cancer is regulated by RalA

Abstract

We previously found that in normal epithelia of the prostate, localization of AQP3 is limited to the cell membranes; however, the expression of AQP3 protein in cancer epithelia is distributed to the plasma. Yet, the detailed mechanism remains unclear. In the present study, PC‑3 cell derivatives with stable knockdown of RAS like proto‑oncogene A (RalA) and overexpression of E‑cadherin were established. We found that overexpression of E‑cadherin and knockdown of RaLA resulted in an increase in AQP3 in prostate cancer cell plasma membranes. In order to investigate the functions caused by of the AQP3 redistribution in prostate cancer cells, the growth function of AQP3 redistribution was detected with clonogenic, MTT and MTS assays. In regards to the effect on apoptosis, flow cytometric analysis and DNA Ladder TUNEL assay were utilized. The results showed that AQP3 redistribution in PC‑3 cells significantly inhibited the proliferation of cells and enhanced cell apoptosis compared with these parameters in the control. Wound healing assay and Matrigel assays determined that knockout of RalA inhibited the motility and invasion capability of PC‑3 cells. To investigate the molecular mechanism involved in AQP3 redistribution in PC‑3 cells, the level of cAMP in PC‑3 cells was examined, and the results showed that AQP3 distribution was regulated through cAMP/PKA/RalA signal pathways. In conclusion, these studies suggest a novel function of AQP3, and provide a creative view for RalA-directed therapies.

AQP3 and AQP5—Potential Regulators of Redox Status in Breast Cancer

“…Trafficking may depend on the phosphorylation of monomers, AQP2 needs phosphorylation of at least three monomers to determine its position in the plasma membrane [ 33 ]. In prostate cancer cells, PC-3, AQP3 is translocated from the cytoplasm to the cell membrane after silencing of RAS like proto-oncogene A (RalA) [ 34 ]. Regulation of the flux through the channel is referred to as gating and is regulated by pH, phosphorylation, temperature, membrane tension, solvent gradient, and pressure [ 24 , 35 , 36 ].…”

Aquaporins as Prognostic Biomarker in Prostate Cancer

“…Nejsum and Nelson, (2007) confirmed that AQP3 co-localizes with E-cadherin during the early stages of cell-cell contact formation [82]. AQP3-E-cadherin co-localization depends upon the level of E-cadherin and increased E-cadherin levels simultaneously increase AQP3 expression in the plasma membranes of prostate epithelial cells [83]. Another study reported that the knockdown of RAS such as proto-oncogene A (RalA) facilitates increased AQP3 expression onto the plasma membrane [83].…”

Targeting Aquaporins in Novel Therapies for Male and Female Breast and Reproductive Cancers

“…Genetic knockdown of AQP1 in rat granulosa and Chinese hamster ovary cells was associated with protection from cell shrinkage and apoptosis [86]. AQP3, located in plasma membranes of human prostate tissue and benign tumors, was found to be internalized in prostate cancer cells, again consistent with a reduction in AQP functionality promoting resistance to apoptosis [87]. In contrast, other cases involving AQP1 and AQP5 have yielded opposite outcomes, in that the presence of the functional channel was protective, and loss of function promoted cell death.…”