Phosphorylation of Yeast Hexokinase 2 Regulates Its Nucleocytoplasmic Shuttling

Nucleocytoplasmic shuttling of Hxk2 induced by glucose levels has been reported recently. Here we present evidence that indicates that Hxk2 nucleocytoplasmic traffic is regulated by phosphorylation and dephosphorylation at serine 14. Moreover, we identified the protein kinase Snf1 and the protein phosphatase Glc7-Reg1 as novel regulatory partners for the nucleocytoplasmic shuttling of Hxk2. Functional studies revealed that, in contrast to the wild-type protein, the dephosphorylation-mimicking mutant of Hxk2 retains its nuclear localization in low glucose conditions, and the phosphomimetic mutant of Hxk2 retains its cytoplasmic localization in high glucose conditions. Interaction experiments of Hxk2 with Kap60 and Xpo1 indicated that nuclear import of the S14D mutant of Hxk2 is severely decreased but that the export is significantly enhanced. Conversely, nuclear import of the S14A mutant of Hxk2 was significantly enhanced, although the export was severely decreased. The interaction of Hxk2 with Kap60 and Xpo1 was found to occur in the dephosphorylated and phosphorylated states of the protein, respectively. In addition, we found that Hxk2 is a substrate for Snf1. Mutational analysis indicated that serine 14 is a major in vitro and in vivo phosphorylation site for Snf1. We also provide evidence that dephosphorylation of Hxk2 at serine 14 is a protein phosphatase Glc7-Reg1-dependent process. Taken together, this study establishes a functional link between Hxk2, Reg1, and Snf1 signaling, which involves the regulation of Hxk2 nucleocytoplasmic shuttling by phosphorylation-dephosphorylation of serine 14.     

IGF and myostatin pathways are respectively induced during the earlier and the later stages of skeletal muscle hypertrophy induced by clenbuterol,a β2‐adrenergic agonist

Clenbuterol, a β₂‐adrenergic agonist, increases the hypertrophy of skeletal muscle. Insulin‐like growth factor (IGF) is reported to work as a potent positive regulator in the clenbuterol‐induced hypertrophy of skeletal muscles. However, the precise regulatory mechanism for the hypertrophy of skeletal muscle induced by clenbuterol is unknown. Myostatin, a member of the TGFβ super family, is a negative regulator of muscle growth. The aim of the present study is to elucidate the function of myostatin and IGF in the hypertrophy of rat masseter muscle induced by clenbuterol. To investigate the function of myostatin and IGF in regulatory mechanism for the clenbuterol‐induced hypertrophy of skeletal muscles, we analysed the expression of myostatin and phosphorylation levels of myostatin and IGF signaling components in the masseter muscle of rat to which clenbuterol was orally administered for 21 days. Hypertrophy of the rat masseter muscle was induced between 3 and 14 days of oral administration of clenbuterol and was terminated at 21 days. The expression of myostatin and the phosphorylation of smad2/3 were elevated at 21 days. The phosphorylation of IGF receptor 1 (IGFR1) and akt1 was elevated at 3 and 7 days. These results suggest that myostatin functions as a negative regulator in the later stages in the hypertrophy of rat masseter muscle induced by clenbuterol, whereas IGF works as a positive regulator in the earlier stages. Copyright © 2012 John Wiley & Sons, Ltd.     

Role of melatonin in the oxidative damage prevention at different times of hepatic regeneration

The process of regenerating liver is the result of a balance between stimulating factors and inhibitors of hepatocyte proliferation. Melatonin and its metabolites have been found to protect tissues against oxidative damage generated by a variety of toxic agents and metabolic processes. Furthermore, studies in liver of rats showed a decrease in the liver mitochondrial hydroxylation of drugs returning to the normal state after the administration of antioxidants. This study was designed to determine, in experimental animals, whether the administration of an antioxidant agent such as melatonin could prevent cells events leading to tissue injury and hepatic dysfunction after partial hepatectomy (PH). Biliary flow (BF), oxidative stress in hepatic tissue and Na⁺/K⁺ATPase activities in whole plasma membrane were determined. PH decreased the Na⁺/K⁺ATPase activity. PH significantly reduced the BF (36%) and promoted oxidative stress with an increase of lipoperoxidation and decrease of glutathione peroxidase and catalase activities. Treatment with melatonin prevented the decrease of BF in rats with hepatectomy and normalized the Na⁺/K⁺ATPase activity. Moreover, melatonin markedly attenuated oxidative stress produced by PH. This may be the results of the higher efficacy of melatonin in scavenging various free radicals and also because of its ability in stimulating the antioxidant enzymes. We suggest that oxidative stress before and during liver regeneration has a crucial role in cholestasis, apoptotic/necrotic hepatocellular damage and the impairment in liver transport function induced by PH and that melatonin could modulate the degree of oxidative stress and through it prevent the alterations in liver function carrier. Copyright © 2012 John Wiley & Sons, Ltd.     

Folivory by a tropical tanager: species of plants used and the relationship between leaf consumption and fruit abundance

ABSTRACT Folivory, or eating leaves, is unusual for small passerines. Puerto Rican Spindalises (Spindalis portoricensis, Thraupidae), tanagers endemic to the island of Puerto Rico, are known to feed on leaves, but little is known about the possible importance of leaves in their diet. Our objectives were to determine the different species of leaves eaten, the percentage of their diet consisting of leaves, and the relationship between leaf consumption and fruit abundance. We used data from previous studies where the foraging activity of Puerto Rican Spindalises was systematically sampled, and from additional observations made throughout the island. We documented 160 records of folivory, with spindalises feeding on 44 plant species in 25 plant families, including monocots, dicots, gymnosperms, and pteridophytes. Spindalises fed on young leaves of 26 plant species, and mature leaves of 19 plant species. Spindalises were primarly frugivorous (83.9% of diet), but leaves were the second most frequent food item in their diets (8.9% of diet). We also found that leaf consumption was negatively correlated with the abundance of ripe fruit, suggesting that leaves were particularly important food items when less fruit was available. The frequency of folivory by spindalises in our study was less than reported for other folivorous passerines such as plantcutters (Phytotoma spp.) and saltators (Saltator spp.). Nonetheless, folivory may help spindalises cope with human‐dominated landscapes and other environmental changes on small islands.     

Numbered neck collars for long‐distance identification of parakeets

ABSTRACT Most parakeets, parrots, and cockatoos are difficult to mark because of their strong beaks and ability to manipulate items with their feet. We developed a marking method that consists of a numbered tag hung on a neck collar. We used this method to successfully monitor Monk Parakeets (Myiopsitta monachus) and Ring‐necked Parakeets (Psittacula krameri) in Barcelona, Spain, from 2003 to 2009. We marked 881 Monk Parakeets and 88 Ring‐necked Parakeets with collars. Fifteen tags placed on adult Monk Parakeets in 2003 (N= 57) lasted until 2008 and nine until 2009. Three of 12 Ring‐necked Parakeets marked in 2003 were resighted in 2008. We estimated that 4.5% of Monk Parakeets and 5.8% of Ring‐necked Parakeets lost their tags, with median intervals between attachment and tag loss of 347 and 370 d, respectively. Behavioral observations revealed no differences in the time budgets of marked and unmarked Monk Parakeets. In addition, the mass of marked Monk Parakeets did not change between successive recaptures. These results suggest that neck collars had no adverse effects on the birds. Neck collars may also be a suitable marking method for other psittacines, with stronger, more durable components likely needed for larger species.     

Pyrenean Pastoralists’ Ecological Knowledge: Documentation and Application to Natural Resource Management and Adaptation

Pastoral production systems in the Spanish Pyrenees have changed dramatically in recent decades, leading to the loss of traditional ecological knowledge (TEK). We documented TEK of pastoralists from two valleys in the western Central Pyrenees of Aragón and explored its potential applications to resource management and adaptation. Pyrenean pastoralists possess extensive knowledge of relationships between terrain, climate, vegetation and animal nutrition and behavior. TEK could contribute to sustainable stewardship and facilitate adaptation by informing pasture monitoring; providing traditional practices to manage mountain vegetation; and preserving knowledge of extensive livestock production strategies, such as transhumance. Institutional barriers to applying TEK include weak economic cooperation among stockmen, their dependence on EU subsidies, and lack of voice in regional government decisions about local resources. A more collaborative, place-based stewardship of the Central Pyrenees might begin with direct involvement of pastoralists in designing monitoring of pasture conditions and vegetation type changes.