Influence of serum-free culture conditions on subcellular localization of steroid 5alpha-reductase in rat C6 glioma cells

5alpha-dihydroprogesterone promotes proliferation and migration of human glioblastoma cells

Glioblastomas (GBMs) are the most common and deadliest intracranial tumors. Steroid hormones, such as progesterone (P4), at physiological concentrations, promote proliferation, and migration of human GBM cells in vivo and in vitro. Neuronal and glial cells, but also GBMs, metabolize P4 and synthesize different active metabolites such as 5α-dihydroprogesterone (5α-DHP). However, their contribution to GBM malignancy remains unknown. Here, we determined the 5α-DHP effects on the number of cells, proliferation, and migration of the U87 and U251 human GBM-derived cell lines. Of the tested concentrations (1 nM-1 µM), 5α-DHP 10 nM significantly increased the number of U87 and U251 cells from day 2 of treatment, and proliferation (at day 3) in a similar manner as P4 (10 nM). The treatment with the progesterone receptor (PR) antagonist RU486 (mifepristone), blocked the effects of 5α-DHP on the number of cells and proliferation. Besides, in U251 and LN229 GBM cells, 5α-DHP promoted cell migration (from 12 to 24 h). We also determined that GBM cells expressed the 3α-hydroxysteroid oxidoreductases (3α-HSOR), which reversibly reduce 5α-DHP to allopregnanolone (3α-THP). These data indicate that 5α-DHP induces proliferation and migration of human GBM through the activation of PR.

Subcellular localization of the five members of the human steroid 5α-reductase family

In humans the steroid 5α-reductase (SRD5A) family comprises five integral membrane enzymes that carry out reduction of a double bond in lipidic substrates: Δ⁴-3-keto steroids, polyprenol and trans-enoyl CoA. The best-characterized reaction is the conversion of testosterone into the more potent dihydrotestosterone carried out by SRD5A1-2. Some controversy exists on their possible nuclear or endoplasmic reticulum localization.

We report the cloning and transient expression in HeLa cells of the five members of the human steroid 5α-reductase family as both N- and C-terminus green fluorescent protein tagged protein constructs. Following the intrinsic fluorescence of the tag, we have determined that the subcellular localization of these enzymes is in the endoplasmic reticulum, upon expression in HeLa cells. The presence of the tag at either end of the polypeptide chain can affect protein expression and, in the case of trans enoyl-CoA reductase, it induces the formation of protein aggregates.

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All members of human testosterone 5α-reductase family were expressed in HeLa cells.

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Subcellular localization of SRD5A proteins in the endoplasmic reticulum is reported.

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The effect of GFP tagging at N- or C-term on SRD5A proteins expression was assessed.

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The TECRL gene is expressed for the first time and its product localizes in the ER.

Interleukin-1β and Interleukin-6 Stimulate Matrix Metalloproteinase-9 Secretion in Cultured Myenteric Glia

Western blotting of culture media of myenteric glia stained positive for GFAP revealed increased secretion of matrix metalloproteinase-9 (MMP-9) in interleukin-1beta (IL-1beta) stimulated cells (10 ng/mL) versus control (142 +/- 19 versus 42 +/- 19, P < 0.05). Interleukin-6 (IL-6) stimulated cells also showed increased expression of MMP-9 (10 ng/mL) versus control (69 +/- 14 versus 4 +/- 2, P < 0.01). Control and cytokine-stimulated cells secreted MMP-2 constituitively. Gelatin zymography demonstrated that products were biologically active. Cytoplasmic staining for MMP-9 was detected in IL-1beta and IL-6-stimulated cells but was negligible in controls. Cultured myenteric glia are responsive to IL-1beta and IL-6 stimulation by secreting MMPs into the extracellular environment.

Influence of serum-free culture conditions on steroid 5alpha-reductase mRNA expression in rat C6 glioma cells

Immunocytochemical studies previously showed that serum deprivation resulted in the appearance of steroid 5alpha-reductase (5alpha-R) in the cytoplasm of rat C6 glioma cells. To determine whether this increase in cytoplasmic 5alpha-R was due to changes in 5alpha-R gene expression, the effect of serum deprivation on 5alpha-R mRNA expression was examined. No significant change in the mRNA levels was observed in cells grown in serum-free culture medium. Therefore, the appearance of 5alpha-R immunoreactivity in the cell cytoplasm observed under serum-free conditions is probably not due to changes in 5alpha-R gene expression.