Keratins regulate protein biosynthesis through localization of GLUT1 and -3 upstream of AMP kinase and Raptor

Removal of the entire keratin family of intermediate filament proteins from embryonic epithelia has surprising implications for mTOR signaling

Functional testosterone receptors in plasma membranes of T cells

T cells are considered to be unresponsive to testosterone due to the absence of androgen receptors (AR). Here, we demonstrate the testosterone responsiveness of murine splenic T cells in vitro as well as the presence of unconventional cell surface receptors for testosterone and classical intracellular AR. Binding sites for testosterone on the surface of both CD4(+) and CD8(+) subsets of T cells are directly revealed with the impeded ligand testosterone-BSA-FITC by confocal laser scanning microscopy (CLSM) and flow cytometry, respectively. Binding of the plasma membrane impermeable testosterone-BSA conjugate induces a rapid rise (<5 s) in [Ca2+]i of Fura-2-loaded T cells. This rise reflects influx of extracellular Ca2+ through non-voltage-gated and Ni2+-blockable Ca2+ channels of the plasma membrane. The testosterone-BSA-induced Ca2+ import is not affected by cyproterone, a blocker of the AR. In addition, AR are not detectable on the surface of intact T cells when using anti-AR antibodies directed against the amino and carboxy terminus of the AR, although T cells contain AR, as revealed by reverse transcription-polymerase chain reactions and Western blotting. AR can be visualized with the anti-AR antibodies in the cytoplasm of permeabilized T cells by using CLSM, though AR are not detectable in cytosol fractions when using the charcoal binding assay with 3H-R1881 as ligand. Cytoplasmic AR do not translocate to the nucleus of T cells in the presence of testosterone, in contrast to cytoplasmic AR in human cancer LNCaP cells. These findings suggest that the classical AR present in splenic T cells are not active in the genomic pathway. By contrast, the cell surface receptors for testosterone are in a functionally active state, enabling T cells a nongenomic response to testosterone

Testosterone signaling in T cells and macrophages

This review summarizes data about non-genomic actions of testosterone on murine malaria, T cells and macrophages produced by our group during the last 15 years. In C578L/10 mice, testosterone induces a lethal outcome of blood stage infections with Plasmodium chabaudi which normally takes a self-healing course controlled by genes of the H-2 complex and the non-H-2 background. This suppressive effect of testosterone is mediated neither via the classic intracellular androgen receptor (AR) response nor, after conversion of testosterone to estradiol, via the estrogen receptor. Testosterone acts non-genomically, i.e. through surface receptors, on murine T cells and macrophages, which becomes evident as a rapid rise in the intracellular free Ca₂₊ concentration ([Ca₂₊]i). In T cells, this rise reflects predominantly influx of extracellular Ca₂₊, while it is predominantly due to release of Ca₂₊ from intracellular Ca₂₊-stores in macrophages. The testosterone- induced rise in [Ca₂₊]i) of both macrophages and T cells is not inhibited by the AR-blocker cyproterone, and it is also inducible by the plasma membrane impermeable ligand testosterone-BSA. The surface receptors initiate a transcription-independent signaling pathway of testosterone. Currently, we are trying to isolate testosterone surface receptors and to investigate a possible cross-talk of non-genomic testosterone signaling with other genotropic signaling pathways