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Mammalian target of rapamycin (m TOR) is a central regulator of cell proliferation and survival. There is limited evidence that m TOR influences hair follicles ( HFs), which undergo cycles of quiescence (telogen), growth (anagen) and regression (catagen). We sought to investigate whether m TOR, in particular m TOR complex 1 (m TORC1), regulates the hair growth cycle by employing biochemical, immunohistochemical and functional approaches in vivo. Here, we demonstrate that quantitative analysis of m TORC1 kinase activity shows phase-dependent changes, and phosphorylated m TOR at S2448 (p-m TOR) was localized in certain sites of HFs in a phase-dependent manner. These results were indicative of m TOR's role in hair growth initiation. Finally, in a pharmacological challenge in vivo using the specific m TORC1 inhibitor, rapamycin, hair cycle initiation was delayed, suggesting a functional relevance of m TORC1 in anagen entry. Based on our findings, we propose that m TORC1 may participate in hair cycle regulation, namely the timing of anagen initiation. [ABSTRACT FROM AUTHOR]

Stress elicits a synchronized response of the endocrine, sympathetic, and central nervous systems to preserve homeostasis and well-being. Glucagon-like peptide-1 (GLP-1), a primary posttranslational product of the preproglucagon (PPG) gene, activates both physical and psychological stress responses. The current study examined mechanisms regulating expression of PPG gene products in the hindbrain. Our results indicate that PPG mRNA decreases rapidly after exposure to acute stressors of multiple modalities. Reduced mRNA levels are accompanied by reduced GLP-1 immunoreactivity in the paraventricular nucleus of hypothalamus, suggesting release at PPG terminals. Stress-induced decrements in PPG mRNA were attenuated in adrenalectomized-corticosterone-replaced rats, suggesting that mRNA down-regulation is due at least in part to glucocorticoid secretion. In contrast, acute stress increased levels of PPG heteronuclear RNA (hnRNA) in a glucocorticoid-dependent manner, suggesting that decreases in PPG mRNA are due to increased degradation rather than reduced transcription. Glucocorticoid administration to unstressed rats is sufficient to cause decrements in PPG mRNA and increments in PPG hnRNA. These findings suggest that glucocorticoids deplete the pool of transcribed PPG mRNA and concurrently stimulate PPG gene transcription, with the latter allowing a mechanism for replenishment of PPG mRNA after stress cessation. The combination of rapid PPG mRNA depletion and initiation of PPG transcription within 30 min is consistent with a rapid action of glucocorticoids on GLP-1 bioavailability, resulting in a transient reduction in the capacity for neuropeptidergic excitation of stress responses. [ABSTRACT FROM AUTHOR]

Heparan sulfate proteoglycans (HSPG) have been implicated in regulating the signalling activities of secreted morphogen molecules including Wingless (Wg), Hedgehog (Hh) and Decapentaplegic (Dpp). HSPG consists of a protein core to which heparan sulfate (HS) glycosaminoglycan (GAG) chains are attached. The formation of HS GAG chains is catalyzed by glycosyltransferases encoded by members of the EXT family of putative tumor suppressors linked to hereditary multiple exostoses. Previous studies in Drosophila demonstrated that tout-velu (ttv), the Drosophila EXT1, is required for Hh movement. However, the functions of other EXT family members are unknown. We have identified and isolated the other two members of the Drosophila EXT family genes, which are named sister of tout-vela (sots) and brother of tout-velu (botv), and encode Drosophila homologues of vertebrate EXT2 and EXT like 3 (EXTL3), respectively. We show that both Hh and Dpp signalling activities, as well as their morphogen distributions, are defective in cells mutant for ttv, sots or botv in the wing disc. Surprisingly, although Wg morphogen distribution is abnormal in ttv, sots and botv, Wg signalling is only defective in botv mutants or ttv-sotv double mutants, and not in ttv nor sots alone, suggesting that Ttv and Sotv are redundant in Wg signalling. We demonstrate further that Ttv and Sotv form a complex and are co-localized in vivo. Our results, along with previous studies on Ttv, provide evidence that all three Drosophila EXT proteins are required for the biosynthesis of HSPGs, and for the gradient formation of the Wg, Hh and Dpp morphogens. Our results also suggest that HSPGs have two distinct roles in Wg morphogen distribution and signalling. [ABSTRACT FROM AUTHOR]

Heparan sulfate proteoglycans (HSPG) have been implicated in regulating the signalling activities of secreted morphogen molecules including Wingless (Wg), Hedgehog (Hh) and Decapentaplegic (Dpp). HSPG consists of a protein core to which heparan sulfate (HS) glycosaminoglycan (GAG) chains are attached. The formation of HS GAG chains is catalyzed by glycosyltransferases encoded by members of the EXT family of putative tumor suppressors linked to hereditary multiple exostoses. Previous studies in Drosophila demonstrated that tout-velu (ttv), the Drosophila EXT1, is required for Hh movement. However, the functions of other EXT family members are unknown. We have identified and isolated the other two members of the Drosophila EXT family genes, which are named sister of tout-velu (sotv) and brother of tout-velu (botv), and encode Drosophila homologues of vertebrate EXT2 and EXT-like 3 (EXTL3), respectively. We show that both Hh and Dpp signalling activities, as well as their morphogen distributions, are defective in cells mutant for ttv, sotv or botv in the wing disc. Surprisingly, although Wg morphogen distribution is abnormal in ttv, sotv and botv, Wg signalling is only defective in botv mutants or ttv-sotv double mutants, and not in ttv nor sotv alone, suggesting that Ttv and Sotv are redundant in Wg signalling. We demonstrate further that Ttv and Sotv form a complex and are co-localized in vivo. Our results, along with previous studies on Ttv, provide evidence that all three Drosophila EXT proteins are required for the biosynthesis of HSPGs, and for the gradient formation of the Wg, Hh and Dpp morphogens. Our results also suggest that HSPGs have two distinct roles in Wg morphogen distribution and signalling.