Progesterone in the uterus. VI. On the question of the in vitro progesterone metabolism in human endometrium and myometrium

Human endometrial and myometrial tissue pieces were incubated with radioactively labeled progesterone in nutrient medium for 20 min., 1 hr and 2 hrs. The only compound extracted from the tissue pieces and the nutrient fluids was identified to be progesterone by TLC, chemical reactions and crystallization experiments. Radiometabolites could not be detected in the tissue pieces and in the nutrient fluids under the experimental conditions applied ( 10^?7 M 1,2-³H-progesterone in the incubation medium). This result is comparable with recent findings on the in vitro progesterone metabolism by rat uterine tissue.     

Plant biodiversity and ethnobotany of Borana pastoralists in Southern Oromia, Ethiopia

A survey of plant biodiversity and ethnobotanical studies was conducted in southern Ethiopia using an integrated approach of botanical collections, group discussions, interviews and questionnaires. Species richness, growth forms and uses of native wild plants are described. Borana pastoralists distinguished and named 86% of the plant species identified. A total of 327 plant species distributed among 197 genera and 69 families are documented: 40% are trees/shrubs, 30% forbs (non-woody plants other than grasses and sedges), 16% grasses, 10% climbers, 2% sedges and 2% succulents. Based on richness of species and usefulness, the most important families are Poaceae, Fabaceae, Lamiaceae and Asteraceae. Two hundred forty-eight species (76%) are used by Borana pastoralists, out of which 42% have multiple uses. Indigenous knowledge of pastoralists on use and management of their plant resources is a valuable source of information for conservation and sustainable utilization of the plant biodiversity and, hence, conservation based on indigenous knowledge is recommended.     

Carotenoid Crystal Formation in Arabidopsis and Carrot Roots Caused by Increased Phytoene Synthase Protein Levels

Background

As the first pathway-specific enzyme in carotenoid biosynthesis, phytoene synthase (PSY) is a prime regulatory target. This includes a number of biotechnological approaches that have successfully increased the carotenoid content in agronomically relevant non-green plant tissues through tissue-specific PSY overexpression. We investigated the differential effects of constitutive AtPSY overexpression in green and non-green cells of transgenic Arabidopsis lines. This revealed striking similarities to the situation found in orange carrot roots with respect to carotenoid amounts and sequestration mechanism.

Methology/Principal Findings

In Arabidopsis seedlings, carotenoid content remained unaffected by increased AtPSY levels although the protein was almost quantitatively imported into plastids, as shown by western blot analyses. In contrast, non-photosynthetic calli and roots overexpressing AtPSY accumulated carotenoids 10 and 100-fold above the corresponding wild-type tissues and contained 1800 and 500 µg carotenoids per g dry weight, respectively. This increase coincided with a change of the pattern of accumulated carotenoids, as xanthophylls decreased relative to β-carotene and carotene intermediates accumulated. As shown by polarization microscopy, carotenoids were found deposited in crystals, similar to crystalline-type chromoplasts of non-green tissues present in several other taxa. In fact, orange-colored carrots showed a similar situation with increased PSY protein as well as carotenoid levels and accumulation patterns whereas wild white-rooted carrots were similar to Arabidopsis wild type roots in this respect. Initiation of carotenoid crystal formation by increased PSY protein amounts was further confirmed by overexpressing crtB, a bacterial PSY gene, in white carrots, resulting in increased carotenoid amounts deposited in crystals.

Conclusions

The sequestration of carotenoids into crystals can be driven by the functional overexpression of one biosynthetic enzyme in non-green plastids not requiring a chromoplast developmental program as this does not exist in Arabidopsis. Thus, PSY expression plays a major, rate-limiting role in the transition from white to orange-colored carrots.     

Regulation of VEGF-induced endothelial cell migration by mitochondrial reactive oxygen species

Endothelial migration is a crucial aspect of a variety of physiologic and pathologic conditions including atherosclerosis and vascular repair. Reactive oxygen species (ROS) function as second messengers during endothelial migration. Multiple intracellular sources of ROS are regulated by cellular context, external stimulus, and the microenvironment. However, the predominant source of ROS during endothelial cell (EC) migration and the mechanisms by which ROS regulate cell migration are incompletely understood. In this study, we tested the hypothesis that mitochondria-derived ROS (mtROS) regulate EC migration. In cultured human umbilical vein endothelial cells, VEGF increased mitochondrial metabolism, promoted mtROS production, and induced cell migration. Either the targeted mitochondrial delivery of the antioxidant, vitamin E (Mito-Vit-E), or the depletion of mitochondrial DNA abrogated VEGF-mediated mtROS production. Overexpression of mitochondrial catalase also inhibited VEGF-induced mitochondrial metabolism, Rac activation, and cell migration. Furthermore, these interventions suppressed VEGF-stimulated EC migration and blocked Rac1 activation in endothelial cells. Constitutively active Rac1 reversed Mito-Vit-E-induced inhibition of EC migration. Mito-Vit-E also attenuated carotid artery reendothelialization in vivo. These results provide strong evidence that mtROS regulate EC migration through Rac-1.     

Bioinformatic survey for new physiological substrates of Cyclin-dependent kinase 5

Cyclin-dependent kinase 5 (Cdk5) is a proline-directed serine/threonine kinase predominantly active in the nervous system where it regulates several processes such as neuronal migration, cytoskeletal dynamics, axonal guidance, and neurotransmission.We constructed a position specific scoring matrix (PSSM) based on a dataset of sites shown to be phosphorylated both in vivo and in vitro by Cdk5. This dataset was curated manually through an exhaustive search of published experimental data. We then used this PSSM to perform a search in the mouse proteome through Scansite, a web-based tool for matching sequence patterns in large databases. Considering a stringent cut-off score of 0.5, we identified 354 new putative sites present in 291 proteins. In order to assess the robustness of our results, ten random subsets (of 80 sites each) of the original dataset were used to construct new PSSMs, which were then used as input for a new Scansite search, leading to the recovery of 81% of the 354 sites by at least 5 PSSMs.In order to reduce the number of false positives in our sequence-based approach, we evaluated which of these predicted sites were phosphorylated in vivo as determined by multiple phosphoproteomics studies carried out through mass spectrometry and available in the PhosphoSitePlus database. This step resulted in a very promising list of 132 putative phosphorylation sites for Cdk5, of which, 51 are specifically phosphorylated in brain tissue, and some are involved in functions regulated by Cdk5 such as axonal growth, synaptic plasticity and neurotransmission. Other phosphorylation sites in our list suggest that Cdk5 might regulate processes through mechanisms not previously recognized such as the control of mRNA splicing.     

Cdk5 regulates Rap1 activity

Rap1 signaling is important for migration, differentiation, axonal growth, and during neuronal polarity. Rap1 can be activated by external stimuli, which in turn regulates specific guanine nucleotide exchange factors such as C3G, among others. Cdk5 functions are also important to neuronal migration and differentiation. Since we found that pharmacological inhibition of Cdk5 by using roscovitine reduced Rap1 protein levels in COS-7 cells and also C3G contains three putative phosphorylation sites for Cdk5, we examined whether the Cdk5-dependent phosphorylation of C3G could affect Rap1 expression and activity. We co-transfected C3G and tet-OFF system for p35 over-expression, an activator of Cdk5 activity into COS-7 cells, and then we evaluated phosphorylation in serine residues in C3G by immunoprecipitation and Western blot. We found that p35 over-expression increased C3G-serine-phosphorylation while inhibition of p35 expression by tetracycline or inhibition of Cdk5 activity with roscovitine decreased it. Interestingly, we found that MG-132, a proteasome inhibitor, rescue Rap1 protein levels in the presence of roscovitine. Besides, C3G-serine-phosphorylation and Rap1 protein levels were reduced in brain from Cdk5^−/− as compared with the Cdk5^+/+ brain. Finally, we found that p35 over-expression increased Rap1 activity while inhibition of p35 expression by tetracycline or roscovitine decreased Rap1 activity. These results suggest that Cdk5-mediated serine-phosphorylation of C3G may control Rap1 stability and activity, and this may potentially impact various neuronal functions such as migration, differentiation, and polarity.