Aquaporin‐1 plays important role in proliferation by affecting cell cycle progression

Abstract

Aquaporin-1 (AQP1) has been associated with tumor development. Here, we investigated how AQP1 may affect cell proliferation. The proliferative rate of adult carotid body (CB) cells, known to proliferate under chronic hypoxia, was analyzed in wild-type (AQP1(+/+) ) and knock out (AQP1(-/-) ) mice, maintained in normoxia or exposed to hypoxia while BrdU was administered. Fewer numbers of total BrdU(+) and TH-BrdU(+) cells were observed in AQP1(-/-) mice, indicating a role for AQP1 in CB proliferation. Then, by flow cytometry, cell cycle state and proliferation of cells overexpressing AQP1 were compared to those of wild-type cells. In the AQP1-overexpressing cells, we observed higher cell proliferation and percentages of cells in phases S and G2/M and fewer apoptotic cells after nocodazole treatment were detected by annexin V staining. Also in these cells, proteomic assays showed higher expression of cyclin D1 and E1 and microarray analysis revealed changes in many cell proliferation-related molecules, including, Zeb 2, Jun, NF-kβ, Cxcl9, Cxcl10, TNF, and the TNF receptor. Overall, our results indicate that the presence of AQP1 modifies the expression of key cell cycle proteins apparently related to increases in cell proliferation. This contributes to explaining the presence of AQP1 in many different tumors.

Role of aquaporins in cell proliferation: What else beyond water permeability?

“…88 Looking for a direct connection between the expression levels of AQPs and the cell cycle pattern, that might explain the higher proliferation rates observed when using a cell line with stable overexpression of either AQP1 or AQP3, we performed a long series of experiments that led us to propose an important role of AQPs in proliferation. 13,24 Analysis of the asynchronous cell cycle pattern in cells overexpressing AQP1 and AQP3 (Fig. 1) revealed a higher percentage of cells in the most proliferative phases, S and G2/M, with a consequent reduction in the percentage of cells in the G0/G1 phases, compared to the distribution in control cells that did not express AQPs.…”

“…Considering these modifications of the cell cycle together with the cell count and BrdU incorporation data, both showing higher numbers of cells, we concluded that overexpression of AQPs promotes the progression of cells through the cell cycle increasing their cell proliferation rate. According to these, cells that overexpressed AQP1 and AQP3 also had higher levels of cyclins D1 and E1 13,24 (Fig. 2), two cell cycle regulatory proteins crucial for phase transition during cell cycle progression, [89][90][91] while levels of cyclin B were unchanged, indicating that cells were not arrested in S and G2/M phases; on the contrary, they potentially progress faster through the cycle.…”

“…[25][26][27] In fact, factors that affect cell volume also have an effect on mechanisms that control cell proliferation. 28,29 Recently, we have shown 13,24 that cells with AQP1 and AQP3 overexpression have a constitutively larger cell volume and complexity. These results are in agreement with the well-accepted hypothesis that, during progression through the cell cycle, cell volume increases as a result of the accumulation of diverse substrates, protein synthesis, and DNA duplication.…”

“…The higher expression in these cells of cyclin E1, which regulates the checkpoint for G1-S transition, [89][90][91] could support this response to butyrate treatment. 24 More recently, we studied the cell cycle after nocodazole treatment to synchronize cells in the mitotic prophase. The analysis again showed clearly less synchronization in the G2/M phase for cells overexpressing AQP1 and AQP3, 13,24 indicating that AQP overexpression made cells resistant to cell cycle arrest, probably by a mechanism that accelerates cell cycle progression and ultimately increases cell proliferation.…”

“…[13][14][15][16][17][18] Additionally, various studies have demonstrated that AQP expression is modified over the course of the cell cycle [19][20][21][22][23] and, more recently, we have shown that overexpression of AQP1 and AQP3 alters the levels of essential checkpoint proteins (cyclins) relevant for cell cycle progression, in addition to modifying the levels of transcription factors, and cytokines. 13,24 In this review, we have sought to gather the most relevant evidence associating AQPs with cell proliferation and we will discuss whether the canonical function of water permeation of these proteins would be always essential for this process or the role in proliferation might be independent of this function.…”