Granin-family proteins, including chromogranin A (CgA) and secretogranin III (SgIII), are transported to secretory granules (SGs) in neuroendocrine cells. We previously showed that SgIII binds strongly to CgA in an intragranular milieu and targets CgA to SGs in pituitary and pancreatic endocrine cells. In this study, we demonstrated that with a sucrose density gradient of rat insulinoma-derived INS-1 cell homogenates, SgIII was localized to the SG fraction and was fractionated to the SG membrane (SGM) despite lacking the transmembrane region. With depletion of cholesterol from the SGM using methyl-␤-cyclodextrin, SgIII was impaired to bind to the SGM. Both SgIII and CgA were solubilized from the SGM by Triton X-100 in contrast to the Triton X-100 insolubility of carboxypeptidase E. SgIII and carboxypeptidase E strongly bound to the SGM-type liposome in intragranular conditions, but CgA did not. Instead, CgA bound to the SGM-type liposome only in the presence of SgIII. Immunocytochemical and pulse-chase experiments revealed that SgIII deleting the N-terminal lipid-binding region missorted to the constitutive pathway in mouse corticotroph-derived AtT-20 cells. Thus, we suggest that SgIII directly binds to cholesterol components of the SGM and targets CgA to SGs in pituitary and pancreatic endocrine cells.

When hypertrophic growth is induced in neonatal rat cardiocytes by stretching, the cardiocytes express high levels of brain-type natriuretic peptide (BNP) and the proprotein-processing enzyme furin. A BNP precursor, ␥BNP, possesses a furin-cleavable Arg-X-X-Arg motif, which is cleaved when ␥BNP is processed to form BNP-45. The Arg-X-X-Arg motif is found in many precursors of growth factors and growth-related proteins. To determine if furin converts ␥BNP to BNP-45 as well as other unidentified growth-promoting protein precursors to their active form that may induce hypertrophic growth in cardiocytes, we used two protease inhibitor systems, synthetic peptidyl chloromethyl ketones (CMK) (decArg-Val-Lys-Arg-CMK and dec-Phe-Ala-Lys-Arg-CMK; where dec is decanoyl) and vaccinia vector-integrated native and variant ␣ 1 -antitrypsins. The furin-specific inhibitors, dec-Arg-Val-Lys-Arg-CMK and variant ␣ 1 -antitrypsin with the inhibitory determinant Arg-X-X-Arg, suppressed the stretch-induced hypertrophic growth of cardiocytes as well as the processing of ␥BNP to BNP-45. The other serine protease inhibitors and variant ␣ 1 -antitrypsin against elastase, or thrombin, however, neither suppressed the hypertrophic growth nor prevented the processing of ␥BNP to BNP-45. Thus, we suggest that furin catalyzes the conversion of ␥BNP to BNP-45 as well as growth-promoting proproteins to their active form, which might induce hypertrophic growth in cardiocytes.When cardiocytes undergo the stretch force, they adapt by developing cellular hypertrophy. Because cardiocytes are terminally differentiated and cannot proliferate by cell division, they exhibit hypertrophic growth, an increase in cell size and protein content. The hypertrophic growth of cardiocytes is attained through a series of multiple gene expressions (1-4) and phosphorylation reactions (4, 5) as follows: expression of immediate early genes such as c-fos, c-jun, and Egr-1; consequent protein kinase cascade of phosphorylation reactions and expression of peptide growth factors such as fibroblast growth factor and transforming growth factor-␤ (TGF-␤) 1 ; cardiac regulatory peptides such as atrial natriuretic peptide (ANP) and brain-type natriuretic peptide (BNP); the contractile proteins myosin light chain-2 and fetal-type ␤-myosin heavy chain; and probably extracellular matrix-degrading metalloproteinases at a remodeling step (6). Some these proteins are produced as precursors, including TGF-␤ (7, 8), ANP (9, 10), BNP (10), and metalloproteinases including membrane-type matrix metalloproteinase (11) and stromelysin-3 (12). The precursors are cleaved to the active forms by endoproteases. Because TGF-␤, BNP, membrane-type matrix metalloproteinase, and stromelysin-3 contain a cleavage site for the proprotein-processing endoprotease furin (7, 10 -12), we examined whether furin might be another candidate gene expressed during the hypertrophic growth of cardiocytes.Furin belongs to the yeast Kex2 endoprotease family, to which the neuroendocrine cell-specific endoproteases PC2 and P...

Photodegradation of methyl mercury (MeHg) and ethyl Hg (EtHg) in sea water was studied by sunlight or ultraviolet (UV) light exposure, and by determining inorganic Hg produced by degradation. Sea water containing 1 microM MeHg or EtHg was exposed to sunlight or UV light. N-Acetyl-L-cysteine was added to the solution for preventing Hg loss during the light exposure. MeHg and EtHg in sea water were degraded by sunlight (> 280 nm), UV light A (320-400 nm) and UV light B (280-320 nm), though the amounts of inorganic Hg produced from MeHg were 1/6th to 1/12th those from EtHg. Inorganic Hg production was greater with increasing concentration of sea water. Degradation of MeHg and EtHg by the UV light A exposure was inhibited by singlet oxygen (1O2) trappers such as NaN3, 1,4-diazabicyclo[2,2,2]octane, histidine, methionine and 2,5-dimethylfuran. On the other hand, inhibitors or scavengers of superoxide anion, hydrogen peroxide or hydroxyl radical did not inhibit the photodegradation of alkyl Hg. These results suggested that 1O2 generated from sea water exposed to sunlight, UV light A or UV light B was the reactive oxygen species mainly responsible for the degradation of MeHg and EtHg.

This systematic review summarises and critically appraises the literature on structural magnetic resonance imaging in people with a current or past eating disorder. Studies using voxel-based morphometry image analysis were included. Ten studies reported on a total of 236 people with a current or past eating disorder and 257 healthy controls. Sample heterogeneity prohibited a meta-analytic approach. The findings do not unequivocally indicate grey or white matter volume abnormalities in people with an eating disorder. Nevertheless, these preliminary data suggest that, compared with healthy controls, people with anorexia nervosa have decreased grey matter in a range of brain regions and that those with bulimia nervosa have increased grey matter volumes in frontal and ventral striatal areas. Research in the recovery phase and longitudinal studies suggest that potential brain tissue abnormalities may recover with clinical improvement. Overall, as the available data are inconclusive, further efforts in this field are warranted.

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