The structure, catalytic mechanism and regulation of adenylyl cyclase

The recent structure determinations of the mammalian effector enzyme adenylyl cyclase reveal the structure of its catalytic core, provide new insights into its catalytic mechanism and suggest how diverse signaling molecules regulate its activity.     

Evaluating distributional shifts in home range estimates

A variety of methods are commonly used to quantify animal home ranges using location data acquired with telemetry. High‐volume location data from global positioning system (GPS) technology provide researchers the opportunity to identify various intensities of use within home ranges, typically quantified through utilization distributions (UDs). However, the wide range of variability evident within UDs constructed with modern home range estimators is often overlooked or ignored during home range comparisons, and challenges may arise when summarizing distributional shifts among multiple UDs. We describe an approach to gain additional insight into home range changes by comparing UDs across isopleths and summarizing comparisons into meaningful results. To demonstrate the efficacy of this approach, we used GPS location data from 16 bighorn sheep (Ovis canadensis) to identify distributional changes before and after habitat alterations, and we discuss advantages in its application when comparing home range size, overlap, and joint‐space use. We found a consistent increase in bighorn sheep home range size when measured across home range levels, but that home range overlap and similarity values decreased when examined at increasing core levels. Our results highlight the benefit of conducting multiscale assessments when comparing distributions, and we encourage researchers to expand comparative home range analyses to gain a more comprehensive evaluation of distributional changes and to evaluate comparisons across home range levels.     

Association of 25-Hydroxyvitamin D status and genetic variation in the vitamin D metabolic pathway with FEV1 in the Framingham Heart Study

Background

Vitamin D is associated with lung function in cross-sectional studies, and vitamin D inadequacy is hypothesized to play a role in the pathogenesis of chronic obstructive pulmonary disease. Further data are needed to clarify the relation between vitamin D status, genetic variation in vitamin D metabolic genes, and cross-sectional and longitudinal changes in lung function in healthy adults.

Methods

We estimated the association between serum 25-hydroxyvitamin D [25(OH)D] and cross-sectional forced expiratory volume in the first second (FEV₁) in Framingham Heart Study (FHS) Offspring and Third Generation participants and the association between serum 25(OH)D and longitudinal change in FEV₁ in Third Generation participants using linear mixed-effects models. Using a gene-based approach, we investigated the association between 241 SNPs in 6 select vitamin D metabolic genes in relation to longitudinal change in FEV₁ in Offspring participants and pursued replication of these findings in a meta-analyzed set of 4 independent cohorts.

Results

We found a positive cross-sectional association between 25(OH)D and FEV₁ in FHS Offspring and Third Generation participants (P = 0.004). There was little or no association between 25(OH)D and longitudinal change in FEV₁ in Third Generation participants (P = 0.97). In Offspring participants, the CYP2R1 gene, hypothesized to influence usual serum 25(OH)D status, was associated with longitudinal change in FEV₁ (gene-based P < 0.05). The most significantly associated SNP from CYP2R1 had a consistent direction of association with FEV₁ in the meta-analyzed set of replication cohorts, but the association did not reach statistical significance thresholds (P = 0.09).

Conclusions

Serum 25(OH)D status was associated with cross-sectional FEV₁, but not longitudinal change in FEV₁. The inconsistent associations may be driven by differences in the groups studied. CYP2R1 demonstrated a gene-based association with longitudinal change in FEV₁ and is a promising candidate gene for further studies.

Electronic supplementary material

The online version of this article (doi:10.1186/s12931-015-0238-y) contains supplementary material, which is available to authorized users.     

Prolactin and vasoinhibins: Endogenous players in diabetic retinopathy

Diabetic retinopathy is a disease of the retinal microvasculature that develops as a complication of diabetes mellitus and constitutes a major cause of blindness in adults of all ages. Diabetic retinopathy is characterized by the loss of capillary cells leading to increased vasopermeability, ischemia, and hypoxia that trigger the excessive formation of new blood vessels in the retina. The influence of the pituitary gland in the pathophysiology of diabetic retinopathy was recognized nearly six decades ago, but the contribution of pituitary hormones to this disease remains unclear. Recent studies have shown that the pituitary hormone prolactin is proteolytically cleaved to vasoinhibins, a family of peptides with potent antivasopermeability, vasoconstrictive, and antiangiogenic actions that can protect the eye against the deleterious effects of the diabetic state. In this review, we summarize what is known about the changes in the circulating levels of prolactin and vasoinhibins during diabetes and diabetic retinopathy as well as the implications of these changes for the development and progression of the disease with particular attention to hyperprolactinemia in pregnancy and postpartum. We discuss the effects of prolactin and vasoinhibins that may impact diabetic retinopathy and suggest these hormones as important targets for therapeutic interventions.     

Nf1 and Gmcsf interact in myeloid leukemogenesis

The NF1 tumor suppressor gene encodes neurofibromin, a GTPase-activating protein (GAP) for p21ras (Ras). Children with NF1 are predisposed to juvenile myelomonocytic leukemia (JMML). Some heterozygous Nf1 mutant mice develop a similar myeloproliferative disorder (MPD), and adoptive transfer of Nf1-deficient fetal liver cells consistently induces this MPD. Human JMML and murine Nf1-deficient cells are hypersensitive to granulocyte-macrophage colony-stimulating factor (GM-CSF) in methylcellulose cultures. We generated hematopoietic cells deficient in both Nf1 and Gmcsf to test whether GM-CSF is required to drive excessive proliferation of Nf1-/- cells in vivo. Here we show that GM-CSF play a central role in establishing and maintaining the MPD and that recipients engrafted with Nf1-/- Gmcsf-/- hematopoietic cells are hypersensitive to exogenous GM-CSF.     

Ubiquitination of Neuronal Nitric-oxide Synthase in the Calmodulin-binding Site Triggers Proteasomal Degradation of the Protein

Nitric-oxide synthase, a cytochrome P450-like hemoprotein enzyme, catalyzes the synthesis of nitric oxide, a critical signaling molecule in a variety of physiological processes. Our laboratory has discovered that certain drugs suicide-inactivate neuronal nitric-oxide synthase (nNOS) and lead to the preferential ubiquitination of the inactivated nNOS by an Hsp70- and CHIP (C terminus of Hsc70-interacting protein)-dependent process. To further understand the process by which altered nNOS is recognized, ubiquitinated, and proteasomally degraded, we examined the sites of ubiquitination on nNOS. We utilized an in vitro ubiquitination system containing purified E1, E2 (UbcH5a), Hsp70, and CHIP that recapitulates the ability of the cells to selectively recognize and ubiquitinate the altered forms of nNOS. LC-MS/MS analysis of the tryptic peptides obtained from the in vitro ubiquitinated nNOS identified 12 ubiquitination sites. Nine of the sites were within the oxygenase domain and two were in the calmodulin-binding site, which links the oxygenase and reductase domains, and one site was in the reductase domain. Mutational analysis of the lysines in the calmodulin-binding site revealed that Lys-739 is a major site for poly-ubiquitination of nNOS in vitro and regulates, in large part, the CHIP-dependent degradation of nNOS in HEK293 cells, as well as in in vitro studies with fraction II. Elucidating the exact site of ubiquitination is an important step in understanding how chaperones recognize and trigger degradation of nNOS.     

14-3-3 Protects against stress-induced apoptosis

Expression of human Bax, a cardinal regulator of mitochondrial membrane permeabilization, causes death in yeast. We screened a human cDNA library for suppressors of Bax-mediated yeast death and identified human 14-3-3β/α, a protein whose paralogs have numerous chaperone-like functions. Here, we show that, yeast cells expressing human 14-3-3β/α are able to complement deletion of the endogenous yeast 14-3-3 and confer resistance to a variety of different stresses including cadmium and cycloheximide. The expression of 14-3-3β/α also conferred resistance to death induced by the target of rapamycin inhibitor rapamycin and by starvation for the amino acid leucine, conditions that induce autophagy. Cell death in response to these autophagic stimuli was also observed in the macroautophagic-deficient atg1Δ and atg7Δ mutants. Furthermore, 14-3-3β/α retained its ability to protect against the autophagic stimuli in these autophagic-deficient mutants arguing against so called ‘autophagic death''. In line, analysis of cell death markers including the accumulation of reactive oxygen species, membrane integrity and cell surface exposure of phosphatidylserine indicated that 14-3-3β/α serves as a specific inhibitor of apoptosis. Finally, we demonstrate functional conservation of these phenotypes using the yeast homolog of 14-3-3: Bmh1. In sum, cell death in response to multiple stresses can be counteracted by 14-3-3 proteins.