Characterization of local calcium signals in tubular networks of endoplasmic reticulum

Cell Calcium ◽  
2007 ◽  
Vol 42 (3) ◽  
pp. 245-260 ◽  
Author(s):  
Irina Baran
Keyword(s):  
Endoplasmic Reticulum ◽  
Calcium Signals

A characterization of heam uptake and intracellular distribution by isolated hepatocytes

1985 ◽  
Vol 5 (7) ◽  
pp. 609-614 ◽  
Author(s):  
A. Lodola
Keyword(s):  
Endoplasmic Reticulum ◽  
Specific Binding ◽  
Isolated Hepatocytes ◽  
Intracellular Distribution ◽  
Distribution Data ◽  
Temperature Dependent ◽  
Rat Hepatocyte ◽  
Isolated Rat ◽  
Endoplasmic Reticulum Fraction

The uptake and intracellular distribution of haem by isolated rat hepatocyte suspensions was studied. An increase in cell haem content occurred after a challenge with 5, 10 or 20 μM haem, supplied as methaemalbumin. The rate of haem uptake was temperature dependent; no non-specific binding occurred. Intracellular haem distribution data are consistent with a rapid association of haem with the endoplasmic reticulum fraction prior to its accumulation in the cytosol and at the mitochondrion.

Cloning and characterization of sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA) from crayfish axial muscle. Sarco/Endoplasmic Reticulum Ca(2+)-ATPase

2000 ◽  
Vol 203 (22) ◽  
pp. 3411-3423 ◽  
Author(s):  
Z. Zhang ◽  
D. Chen ◽  
M.G. Wheatly
Keyword(s):  
Endoplasmic Reticulum ◽  
Amino Acid ◽  
Procambarus Clarkii ◽  
Muscle Growth ◽  
Abdominal Muscle ◽  
Northern Analysis ◽  
Specific Expression ◽  
Loop Region ◽  
Moulting Cycle

The discontinuous pattern of muscle growth during the moulting cycle of a freshwater crustacean (the crayfish Procambarus clarkii) was used as a model system to examine the regulation of the expression of Sarco/Endoplasmic Reticulum Ca(2+)-ATPase (SERCA). We describe the cloning, sequencing and characterization of a novel SERCA cDNA (3856 bp) obtained from crayfish axial abdominal muscle by reverse transcription/polymerase chain reaction (RT-PCR) followed by rapid amplification of cDNA ends (RACE). This complete sequence contains a 145 base pair (bp) noncoding region at the 5′ end, a 3006 bp open reading frame coding for 1002 amino acid residues with a molecular mass of 110 kDa and 705 bp of untranslated region at the 3′ end. This enzyme contains all the conserved domains found in ‘P’-type ATPases, and the hydropathy profile suggests a transmembrane organization typical of other SERCAs. It exhibits 80% amino acid identity with Drosophila melanogaster SERCA, 79% identity with Artemia franciscana SERCA, 72% identity with rabbit fast-twitch muscle neonatal isoform SERCA1b, 71% identity with slow-twitch muscle isoform SERCA2 and 67% identity with SERCA3. Sequence alignment revealed that regions anchoring the cytoplasmic domain in the membrane were highly conserved and that most differences were in the NH(2) terminus, the central loop region and the COOH terminus. Northern analysis of total RNA from crayfish tissues probed with the 460 bp fragment initially isolated showed four bands (7.6, 7.0, 5.8 and 4.5 kilobases) displaying tissue-specific expression. SERCA was most abundant in muscle (axial abdominal, cardiac and stomach), where it is involved in Ca(2+) resequestration during relaxation, and in eggs, where it may be implicated in early embryogenesis. The level of SERCA mRNA expression in axial abdominal muscle varied during the moulting cycle as determined by slot-blot analysis. SERCA expression was greatest during intermoult and decreased to approximately 50% of this level during pre- and postmoult. Patterns of gene expression for SERCA and other sarcomeric proteins during the crustacean moulting cycle may be regulated by ecdysteroids and/or mechanical stimulation.

scholarly journals Comparative biosynthesis, covalent post-translational modifications and efficiency of prosegment cleavage of the prohormone convertases PC1 and PC2: glycosylation, sulphation and identification of the intracellular site of prosegment cleavage of PC1 and PC2

1993 ◽  
Vol 294 (3) ◽  
pp. 735-743 ◽  
Author(s):  
S Benjannet ◽  
N Rondeau ◽  
L Paquet ◽  
A Boudreault ◽  
C Lazure ◽  
...  
Keyword(s):  
Endoplasmic Reticulum ◽  
Brefeldin A ◽  
Pulse Labelling ◽  
Prohormone Convertases ◽  
Post Translational Modifications ◽  
Intracellular Degradation ◽  
Golgi Compartment ◽  
Carbonyl Cyanide ◽  
Insulinoma Cells

We present herein the pulse-chase analysis of the biosynthesis of the prohormone convertases PC1 and PC2 in the endocrine GH4C1 cells infected with vaccinia virus recombinants expressing these convertases. Characterization of the pulse-labelled enzymes demonstrated that pro-PC1 (88 kDa) is cleaved into PC1 (83 kDa) and pro-PC2 (75 kDa) into PC2 (68 kDa). Secretion of glycosylated and sulphated PC1 (84 kDa) occurs about 30 min after the onset of biosynthesis, whereas glycosylated and sulphated PC2 (68 kDa) is detected in the medium after between 1 and 2 h. Furthermore, in the case of pro-PC2 only, we observed that a fraction of this precursor escapes glycosylation. A small proportion (about 5%) of the intracellular glycosylated pro-PC2 (75 kDa) is sulphated, and it is this glycosylated and sulphated precursor that is cleaved into the secretable 68 kDa form of PC2. Major differences in the carbohydrate structures of PC1 and PC2 are demonstrated by the resistance of the secreted PC1 to endoglycosidase H digestion and sensitivity of the secreted PC2 to this enzyme. Inhibition of N-glycosylation with tunicamycin caused a dramatic intracellular degradation of these convertases within the endoplasmic reticulum, with the net effect of a reduction in the available activity of PC1 and PC2. These results emphasize the importance of N-glycosylation in the folding and stability of PC1 and PC2. Pulse-labelling experiments in uninfected mouse beta TC3 and rat Rin m5F insulinoma cells, which endogenously synthesize PC2, showed that, as in infected GH4C1 cells, pro-PC2 predominates intracellularly. In order to define the site of prosegment cleavage, pulse-chase analysis was performed at low temperature (15 degrees C) or after treatment of GH4C1 cells with either brefeldin A or carbonyl cyanide m-chlorophenylhydrazone. These results demonstrated that the onset of the conversions of pro-PC1 into PC1 and non-glycosylated pro-PC2 into PC2 (65 kDa) occur in a pre-Golgi compartment, presumably within the endoplasmic reticulum. In contrast, pulse labelling in the presence of Na(2)35SO4 demonstrated that the processing of glycosylated and sulphated pro-PC2 occurs within the Golgi apparatus. In order to test the possibility that zymogen processing is performed by furin, we co-expressed this convertase with either pro-PC1 or pro-PC2. The data demonstrated the inability of furin to cleave either proenzyme.

scholarly journals Cloning and Characterization of a Mouse Endoplasmic Reticulum Alkaline Ceramidase

2003 ◽  
Vol 278 (33) ◽  
pp. 31184-31191 ◽  
Author(s):  
Cungui Mao ◽  
Ruijuan Xu ◽  
Zdzislaw M. Szulc ◽  
Jacek Bielawski ◽  
Kevin P. Becker ◽  
...  
Keyword(s):  
Endoplasmic Reticulum

Identification and functional characterization of a novel human protein highly related to the yeast dynamin-like GTPase Vps1p

1998 ◽  
Vol 111 (10) ◽  
pp. 1341-1349 ◽  
Author(s):  
M. Imoto ◽  
I. Tachibana ◽  
R. Urrutia
Keyword(s):  
Endoplasmic Reticulum ◽  
Cho Cells ◽  
Mammalian Cells ◽  
Functional Characterization ◽  
Luciferase Reporter ◽  
Pleckstrin Homology ◽  
Rich Region ◽  
Gtpase Domain ◽  
Proline Rich Region

Dynamin proteins containing a GTPase domain, a pleckstrin homology motif and a proline-rich tail participate in receptor-mediated endocytosis in organisms ranging from insects to vertebrates. In addition, dynamin-related GTPases, such as the yeast Golgi protein Vps1p, which lack both the pleckstrin homology motif and the proline-rich region, participate in vesicular transport within the secretory pathway in lower eukaryotes. However, no data is available on the existence of Vps1p-like proteins in mammalian cells. In this study, we report the identification and characterization of a novel gene encoding a human dynamin-related protein, DRP1, displaying high similarity to the Golgi dynamin-like protein Vps1p from yeast and to a Caenorhabditis elegans protein deposited in the databank. These proteins are highly conserved in their N-terminal tripartite GTPase domain but lack the pleckstrin homology motif and proline-rich region. Northern blot analysis reveals that the DRP1 mRNA is detected at high levels in human muscle, heart, kidney and brain. Immunolocalization studies in Chinese hamster ovary (CHO) cells using an epitope-tagged form of DRP1 and confocal microscopy show that this protein is concentrated in a perinuclear region that labels with the endoplasmic reticulum marker DiOC6(3) and the Golgi marker C5-DMB-Cer. In addition, the localization of DRP1 is highly similar to the localization of the endoplasmic reticulum and cis-Golgi GTPase Rab1A, but not to the staining for the trans-Golgi GTPase Rab6. Furthermore, overexpression of a cDNA encoding a GTP binding site mutant of DRP1 (DRP1(K38E)) in CHO cells decreases the amount of a secreted luciferase reporter protein, whereas the overexpression of wild-type DRP1 increases the secretion of this marker. Together, these results constitute the first structural and functional characterization of a mammalian protein similar to the yeast dynamin-related GTPase Vps1p and indicate that the participation of these proteins in secretion has been conserved throughout evolution.

Ultrastructural characterization of the basidiomycete septum of Polyporus biennis

1972 ◽  
Vol 50 (12) ◽  
pp. 2463-2469 ◽  
Author(s):  
Royall T. Moore ◽  
Roger Marchant
Keyword(s):  
Endoplasmic Reticulum ◽  
Matrix Material ◽  
Terminal Portion ◽  
Ultrastructural Characterization

The septal apparatus of Polyporus biennis comprises a swollen dolipore, a pair of occluding plugs, and perforate parenthesomes differentiated from the wall endoplasmic reticulum. The pore occlusions have an opaque terminal portion and a translucent stem inserted in the pore. The domain between the parenthesome and the dolipore is traversed by microfilaments which may serve to bind the septal apparatus together. Matrix material is present between the parenthesome membranes, producing a lamellar appearance. This unique septum is typical for most basidiomycetes.

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