Neurosecretory Protein GL Induces Fat Accumulation in Chicks.

We recently found a previously unidentified cDNA in chicken hypothalamus which encodes the precursor for neurosecretory protein GL (NPGL). A previous study showed that intracerebroventricular (i.c.v.) infusion of NPGL caused body mass gain in chicks. However, it was not clear which part(s) of the body gained mass. In the present study, we investigated which tissues increased in mass after chronic i.c.v. infusion of NPGL in chicks. We found that NPGL increased the masses of the liver, abdominal fat, and subcutaneous fat, while NPGL did not affect the masses of muscles, including pectoralis major, pectoralis minor, and biceps femoris. Oil Red O staining revealed that fat deposition had occurred in the liver. In addition, the size of the lipid droplets in the abdominal fat increased. Furthermore, we found an upregulation of lipogenesis and downregulation of lipolysis in the abdominal fat, but not in the liver. These results indicate that NPGL is involved in fat storage in chicks

Localization and function of neurosecretory protein GM, a novel small secretory protein, in the chicken hypothalamus.

Recently, we discovered a novel cDNA encoding the precursor of a small secretory protein, neurosecretory protein GL (NPGL), in the hypothalamic infundibulum of chickens. NPGL plays an important role in the regulation of growth and feeding. A database search indicated that the NPGL gene has a paralogous gene: neurosecretory protein GM (NPGM), also in chickens. We identified cDNA encoding the NPGM precursor in chickens. Morphological analysis showed that NPGM-containing cells are specifically localized in the medial mammillary nucleus (MM) and infundibular nucleus (IN) in the hypothalamus. In addition, we found that NPGM and NPGL are co-localized, especially in the MM. The expression levels of NPGM mRNA gradually decreased during post-hatch development, in contrast to those of NPGL mRNA. Moreover, we investigated the relationship between NPGM and other known factors. NPGM was found to be produced in histaminergic neurons in the MM. NPGM and histidine decarboxylase, a histamine-producing enzyme, displayed similar expression patterns during post-hatch development. Acute intracerebroventricular injection of NPGM decreased food intake, similar to the effect of histamine. To our knowledge, this is the first report of the localization and function of NPGM in the brain of vertebrates. These results will further advance the understanding mechanisms underlying energy homeostasis

The transcription factor XBP-1 is essential for the development and survival of dendritic cells

Dendritic cells (DCs) play a critical role in the initiation, maintenance, and resolution of an immune response. DC survival is tightly controlled by extracellular stimuli such as cytokines and Toll-like receptor (TLR) signaling, but the intracellular events that translate such extracellular stimuli into life or death for the DC remain poorly understood. The endoplasmic reticulum (ER) stress, or unfolded protein response (UPR), is a signaling pathway that is activated when unfolded proteins accumulate in the ER. The most conserved arm of the UPR involves IRE1α, an ER transmembrane kinase and endoribonuclease that activates the transcription factor XBP-1 to maintain ER homeostasis and prevent activation of cell death pathways caused by sustained ER stress. We report that XBP-1 is essential for DC development and survival. Lymphoid chimeras lacking XBP-1 possessed decreased numbers of both conventional and plasmacytoid DCs with reduced survival both at baseline and in response to TLR signaling. Overexpression of XBP-1 in hematopoietic progenitors rescued and enhanced DC development. Remarkably, in contrast to other cell types we have examined, the XBP-1 pathway was constitutively activated in immature DCs

It's a Good Year for Blimp-1 (and Plasma Cells)

AbstractImmunoglobulin secreting plasma cells are critical mediators of an effective humoral immune response. In this issue of Immunity, an article by Shapiro-Shelef et al. defines an essential role for the transcription factor Blimp-1 in plasma cell differentiation and preplasma memory B cell formation

Production and characterization of neurosecretory protein GM using Escherichia coli and Chinese Hamster Ovary cells

AbstractNeurosecretory protein GL (NPGL) and neurosecretory protein GM (NPGM) are paralogs recently discovered in birds and in mammals. The post-translational products of NPGL and of NPGM genes include a signal peptide sequence, a glycine amidation signal, and a dibasic amino acid cleavage site. This suggests that the mature forms of NPGL and of NPGM are small proteins secreted in the hypothalamus and containing an amidated C-terminus. However, endogenous NPGL and NPGM have not yet been identified. Chicken NPGL and NPGM have two highly conserved Cys residues that are likely to form a disulfide bond, while mammalian NPGM has one additional Cys residue located between the two conserved Cys residues and the correct disulfide bond pattern is unclear. In this study, we prepared rat NPGM to elucidate the structure of its mature form. We first expressed the predicted mature NPGM, containing an extra C-terminal Gly, in Escherichia coli SHuffle cells, which are engineered to promote the formation of native disulfide bridges in recombinant proteins. We observed the presence of a disulfide bond between the N-terminal Cys residue and the second Cys residue, while the C-terminal Cys residue was free. Secondly, we transfected a construct containing the entire NPGM open reading frame into Chinese Hamster Ovary cells, and observed that NPGM was cleaved immediately after the signal peptide and that it was secreted into the medium. Furthermore, the protein presented a disulfide bond at the same location observed in recombinant NPGM

Neurosecretory protein GL stimulates food intake, de novo lipogenesis, and onset of obesity.

Mechanisms underlying the central regulation of food intake and fat accumulation are not fully understood. We found that neurosecretory protein GL (NPGL), a newly-identified neuropeptide, increased food intake and white adipose tissue (WAT) in rats. NPGL-precursor gene overexpression in the hypothalamus caused increases in food intake, WAT, body mass, and circulating insulin when fed a high calorie diet. Intracerebroventricular administration of NPGL induced de novo lipogenesis in WAT, increased insulin, and it selectively induced carbohydrate intake. Neutralizing antibody administration decreased the size of lipid droplets in WAT. Npgl mRNA expression was upregulated by fasting and low insulin levels. Additionally, NPGL-producing cells were responsive to insulin. These results point to NPGL as a novel neuronal regulator that drives food intake and fat deposition through de novo lipogenesis and acts to maintain steady-state fat level in concert with insulin. Dysregulation of NPGL may be a root cause of obesity

NG peptides: A novel family of neurophysin-associated neuropeptides

NOTICE: this is the author’s version of a work that was accepted for publication in GENE. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in GENE, [VOL 458, ISSUE 1-2, (2010)] DOI: 10.1016/j.gene.2010.03.00

XBP-1 specifically promotes IgM synthesis and secretion, but is dispensable for degradation of glycoproteins in primary B cells

Differentiation of B cells into plasma cells requires X-box binding protein–1 (XBP-1). In the absence of XBP-1, B cells develop normally, but very little immunoglobulin is secreted. XBP-1 controls the expression of a large set of genes whose products participate in expansion of the endoplasmic reticulum (ER) and in protein trafficking. We define a new role for XBP-1 in exerting selective translational control over high and sustained levels of immunoglobulin M (IgM) synthesis. XBP-1−/− and XBP-1+/+ primary B cells synthesize IgM at comparable levels at the onset of stimulation with lipopolysaccharide or CpG. However, later there is a profound depression in synthesis of IgM in XBP-1−/− B cells, notwithstanding similar levels of μmRNA. In marked contrast, lack of XBP-1 does not affect synthesis and trafficking of other glycoproteins, or of immunoglobulin light chains. Contrary to expectation, degradation of proteins from the ER, using TCRα or US11-mediated degradation of class I major histocompatibility complex molecules as substrates, is normal in XBP-1−/− B cells. Furthermore, degradation of membrane μ was unaffected by enforced expression of XBP-1. We conclude that in primary B cells, the XBP-1 pathway promotes synthesis and secretion of IgM, but does not seem to be involved in the degradation of ER proteins, including that of μ chains themselves