Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Calsequestrin”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7Linked to original sources
PubMed1991

Intracellular Ca2+ stores in chicken Purkinje neurons: differential distribution of the low affinity-high capacity Ca2+ binding protein, calsequestrin, of Ca2+ ATPase and of the ER lumenal protein, Bip.

To identify intracellular Ca2+ stores, we have mapped (by cryosection immunofluorescence and immunogold labeling) the distribution in the chicken cerebellar cortex of an essential component, the main low affinity-high capacity Ca2+ binding protein which in this tissue has been recently shown undistinguishable from muscle calsequestrin (Volpe, P., B. H. Alderson-Lang, L. Madeddu, E. Damiani, J. H. Collins, and A. Margreth. 1990. Neuron. 5:713-721). Appreciable levels of the protein were found exclusively within Purkinje neurons, distributed to the cell body, the axon, and the elaborate dendritic tree, with little labeling, however, of dendritic spines. At the EM level the protein displayed a dual localization: within the ER (rough- and smooth-surfaced cisternae, including the cisternal stacks recently shown [in the rat] to be highly enriched in receptors for inositol 1,4,5-triphosphate) and, over 10-fold more concentrated, within a population of moderately dense, membrane-bound small vacuoles and tubules, identified as calciosomes. These latter structures were widely distributed both in the cell body (approximately 1% of the cross-sectional area, particularly concentrated near the Golgi complex) and in the dendrites, up to the entrance of the spines. The distribution of calsequestrin was compared to those of another putative component of the Ca2+ stores, the membrane pump Ca2+ ATPase, and of the ER resident lumenal protein, Bip. Ca2+ ATPase was expressed by both calciosomes and regular ER cisternae, but excluded from cisternal stacks; Bip was abundant within the ER lumena (cisternae and stacks) and very low within calciosomes (average calsequestrin/Bip immunolabeling ratios were approximately 0.5 and 36.5 in the two types of structure, respectively). These results suggest that ER cisternal stacks do not represent independent Ca2+ stores, but operate coordinately with the adjacent, lumenally continuous ER cisternae. The ER and calciosomes could serve as rapidly exchanging Ca2+ stores, characterized however by different properties, in particular, by the greater Ca2+ accumulation potential of calciosomes. Hypotheses of calciosome biogenesis (directly from the ER or via the Golgi complex) are discussed.

Animals↗
PubMed2006

SERCA1 and calsequestrin storage myopathy: a new surplus protein myopathy.

We describe four patients, from four different families, affected by a mild myopathy or asymptomatic elevated serum creatine kinase levels, in whom toluidine blue-stained semithin sections of muscle specimens revealed inclusions of different size and shape. The inclusions did not stain by routine histochemical studies. The sarcoplasmic or endoplasmic reticulum calcium 1 (SERCA1) ATPase and/or calsequestrin reactivity of inclusions, by immunohistochemistry, and the SERCA1- and calsequestrin-increased expression, by immunoblot, suggested that inclusions were constituted by an excess of proteins normally present in the terminal cisternae of sarcoplasmic reticulum. Our cases, both sporadic and familial, represent a new type of surplus protein myopathy.

Adult↗
PubMed2002

Drastic reduction of calsequestrin-like proteins and impaired calcium binding in dystrophic mdx muscle.

Although the reduction in dystrophin-associated glycoproteins is the primary pathophysiological consequence of the deficiency in dystrophin, little is known about the secondary abnormalities leading to x-linked muscular dystrophy. As abnormal Ca(2+) handling may be involved in myonecrosis, we investigated the fate of key Ca(2+) regulatory membrane proteins in dystrophic mdx skeletal muscle membranes. Whereas the expression of the ryanodine receptor, the dihydropyridine receptor, the Ca(2+)-ATPase, and calsequestrin was not affected, a drastic decline in calsequestrin-like proteins of 150-220 kDa was observed in dystrophic microsomes using one-dimensional immunoblotting, two-dimensional immunoblotting with isoelectric focusing, diagonal two-dimensional blotting technique, and immunoprecipitation. In analogy, overall Ca(2+) binding was reduced in the sarcoplasmic reticulum of dystrophic muscle. The reduction in Ca(2+) binding proteins might be directly involved in triggering impaired Ca(2+) sequestration within the lumen of the sarcoplasmic reticulum. Thus disturbed sarcolemmal Ca(2+) fluxes seem to influence overall Ca(2+) homeostasis, resulting in distinct changes in the expression profile of a subset of Ca(2+) handling proteins, which might be an important factor in the progressive functional decline of dystrophic muscle fibers.

Animals↗
PubMed2002

Absence of calsequestrin 2 causes severe forms of catecholaminergic polymorphic ventricular tachycardia.

Catecholaminergic polymorphic ventricular tachycardia (CPVT) is a rare arrhythmogenic disorder characterized by syncopal events and sudden cardiac death at a young age during physical stress or emotion, in the absence of structural heart disease. We report the first nonsense mutations in the cardiac calsequestrin gene, CASQ2, in three CPVT families. The three mutations, a nonsense R33X, a splicing 532+1 G>A, and a 1-bp deletion, 62delA, are thought to induce premature stop codons. Two patients who experienced syncopes before the age of 7 years were homozygous carriers, suggesting a complete absence of calsequestrin 2. One patient was heterozygous for the stop codon and experienced syncopes from the age of 11 years. Despite the different mutations, there is little phenotypic variation of CPVT for the CASQ2 mutations. Of the 16 heterozygous carriers of these various mutations, 14 were devoid of clinical symptoms or ECG anomalies, whereas 2 of them had ventricular arrhythmias at ECG on exercise tests. In line with this, the diagnosis of the probands was difficult because of the absence of a positive family history. In conclusion, these additional three CASQ2 CPVT families suggest that CASQ2 mutations are more common than previously thought and produce a severe form of CPVT. The full text of this article is available at http://www.circresaha.org.

Adolescent↗
PubMed1991

Expression of sarcoplasmic reticulum Ca(2+)-ATPase and calsequestrin genes in rat heart during ontogenic development and aging.

Little is known concerning the molecular mechanisms responsible for changes in sarcoplasmic reticulum (SR) function during ontogenic development and aging except that the amount of SR Ca(2+)-ATPase mRNA varies in these conditions. The aim of the present work was to determine whether SR maturation requires expression of specific isoforms and synchronous accumulation of mRNAs encoding proteins located in SR. Thus, we have studied expression of SR Ca(2+)-ATPase and calsequestrin genes in the rat at different developmental stages from 14 fetal days to 24 months of age. Analysis of alternative splicing of the major Ca(2+)-ATPase gene expressed in heart by nuclease S1 mapping led us to conclude that the Ca(2+)-ATPase gene expressed in heart was not differentially spliced during ontogenic development and senescence. A single calsequestrin mRNA isoform was also detected in rat heart whatever the developmental stage. The amount of specific mRNA was then measured by dot blot and normalized to 18S ribosomal RNA or to myosin heavy chain mRNA. The amount of Ca(2+)-ATPase mRNA relative to 18S RNA increases substantially at the end of fetal life and in the early postnatal period (9.5 +/- 0.5% in the 14-15 day fetus versus 99 +/- 7% in the 4-day-old rat). A stable high level is observed during adulthood. In aged rats (24 months), Ca(2+)-ATPase mRNA represents only 44.6% the amount observed in young adults (1-2 months).(ABSTRACT TRUNCATED AT 250 WORDS)

Aging↗
PubMed1992

Expression of dihydropyridine receptor (Ca2+ channel) and calsequestrin genes in the myocardium of patients with end-stage heart failure.

Cytoplasmic free calcium ions (Ca2+) play a central role in excitation-contraction coupling of cardiac muscle. Abnormal Ca2+ handling has been implicated in systolic and diastolic dysfunction in patients with end-stage heart failure. The current study tests the hypothesis that expression of genes encoding proteins regulating myocardial Ca2+ homeostasis is altered in human heart failure. We analyzed RNA isolated from the left ventricular (LV) myocardium of 30 cardiac transplant recipients with end-stage heart failure (HF) and five organ donors (normal control), using cDNA probes specific for the cardiac dihydropyridine (DHP) receptor (the alpha 1 subunit of the DHP-sensitive Ca2+ channel) and cardiac calsequestrin of sarcoplasmic reticulum (SR). In addition, abundance of DHP binding sites was assessed by ligand binding techniques (n = 6 each for the patients and normal controls). There was no difference in the level of cardiac calsequestrin mRNA between the HF patients and normal controls. In contrast, the level of mRNA encoding the DHP receptor was decreased by 47% (P less than 0.001) in the LV myocardium from the patients with HF compared to the normal controls. The number of DHP binding sites was decreased by 35-48%. As reported previously, expression of the SR Ca(2+)-ATPase mRNA was also diminished by 50% (P less than 0.001) in the HF group. These data suggest that expression of the genes encoding the cardiac DHP receptor and SR Ca(2+)-ATPase is reduced in the LV myocardium from patients with HF. Altered expression of these genes may be related to abnormal Ca2+ handling in the failing myocardium, contributing to LV systolic and diastolic dysfunction in patients with end-stage heart failure.

Adolescent↗
PubMed2004

Modulation of sarcoplasmic reticulum calcium release by calsequestrin in cardiac myocytes.

Calsequestrin (CASQ2) is a high capacity Ca-binding protein expressed inside the sarcoplasmic reticulum (SR). Mutations in the cardiac calsequestrin gene (CASQ2) have been linked to arrhythmias and sudden death induced by exercise and emotional stress. We have studied the function of CASQ2 and the consequences of arrhythmogenic CASQ2 mutations on intracellular Ca signalling using a combination of approaches of reverse genetics and cellular physiology in adult cardiac myocytes. We have found that CASQ2 is an essential determinant of the ability of the SR to store and release Ca2+ in cardiac muscle. CASQ2 serves as a reservoir for Ca2+ that is readily accessible for Ca(2+)-induced Ca2+ release (CICR) and also as an active Ca2+ buffer that modulates the local luminal Ca-dependent closure of the SR Ca2+ release channels. At the same time, CASQ2 stabilizes the CICR process by slowing the functional recharging of SR Ca2+ stores. Abnormal restitution of the Ca2+ release channels from a luminal Ca-dependent refractory state could account for ventricular arrhythmias associated with mutations in the CASQ2 gene.

Animals↗
PubMed1992

Ca2+ stores in Purkinje neurons: endoplasmic reticulum subcompartments demonstrated by the heterogeneous distribution of the InsP3 receptor, Ca(2+)-ATPase, and calsequestrin.

The nature of second messenger-responsive intracellular Ca2+ stores in neurons remains open for discussion. Here, we demonstrate the existence in Purkinje cells (PCs) of endoplastic reticulum (ER) subcompartments characterized by an uneven distribution of three proteins involved in Ca2+ storage and release: the inositol 1,4,5-trisphosphate (InsP3) receptor, Ca(2+)-ATPase, and calsequestrin. Ca(2+)-ATPase and the InsP3 receptor have a widespread, although not identical, distribution throughout the ER. Calsequestrin is localized throughout the smooth ER and is particularly concentrated in pleiomorphic vesicles with a moderately electron-dense core, which appear to represent a subcompartment of the smooth ER. In double-labeling experiments many of these vesicles were unlabeled by InsP3 receptor antibodies. These results suggest a key role of the ER as an intracellular Ca2+ store and demonstrate a possible structural basis for distinct intracellular Ca2+ pools regulated by different second messengers.

Animals↗
PubMed1989

Four intracisternal calcium-binding glycoproteins from rat liver microsomes with high affinity for calcium. No indication for calsequestrin-like proteins in inositol 1,4,5-trisphosphate-sensitive calcium sequestering rat liver vesicles.

It has been claimed that the inositol 1,4,5-trisphosphate-sensitive calcium pool in liver and pancreatic acinar cells is located in specified organelles ("calciosomes") which are characterized by their content of the calcium-binding protein calsequestrin (Volpe, P., Krause, K. H., Hashimoto, S., Zorzato, F., Pozzan, T., Meldolesi, J., and Lew, D. P. (1988) Proc. Natl. Acad. Sci. U. S. A. 85, 1091-1095). We show here that the inositol 1,4,5-trisphosphate-sensitive compartment of rat liver does not contain calsequestrin-like material. Instead four non-membraneous calcium-binding glycoproteins with approximate molecular masses of 59, 60, 80, and 90 kDa were found. The 59-, 80-, and 90-kDa proteins were of the high mannose-rich type, the carbohydrate moiety of the 60-kDa protein was of the complex hybrid type with terminal galactoses. All four proteins had high affinity binding sites for calcium (KD between 1 and 5 microM) and from 1 to 5 binding sites/molecule. The 80- and the 90-kDa proteins had also low affinity binding sites (KD 400 and 600 microM, respectively, with 13 and 15 binding sites/molecule, respectively). A comparison of the NH2-terminal sequences revealed that the 60-kDa calcium-binding protein represents the rat liver calregulin, whereas the 90-kDa calcium-binding protein represents grp94. The sequences did not reveal any relationship of the 80-kDa protein with grp78, or of the 59-kDa protein with protein disulfide isomerase.

Amino Acid Sequence↗
PubMed1983

Staining of the Ca2+-binding proteins, calsequestrin, calmodulin, troponin C, and S-100, with the cationic carbocyanine dye "Stains-all".

The Ca2+-binding proteins, calsequestrin, calmodulin, troponin C, and S-100, have all been shown to stain dark blue or purple with the cationic carbocyanine dye "Stains-all", while most proteins stain red or pink. Stains-all staining of these Ca2+-binding proteins was 50-100% more intense than Coomassie blue staining, and the blue stained calsequestrin and troponin C could be detected in muscle extracts. Densitometric scans of Stains-all-stained gels revealed that interaction of the dye with Ca2+-binding proteins changed the absorption spectrum of the dye. The dye-protein complex absorbed maximally at 615 nm, reflecting a state that results from the binding of individual dye molecules at anionic sites. Stains-all also interacted with undenatured Ca2+-binding proteins in aqueous solution forming a complex absorbing maximally at 600 nm. A simple assay for Ca2+-binding proteins has been developed using this property. These results suggest that the interaction of the dye with anionic sites within these Ca2+-binding proteins produces the dye-protein complex which absorbs at 600-615 nm. Stains-all staining of these Ca2+-binding proteins will be useful in their identification and purification from various tissues. It might also be a valuable tool in the identification of potential Ca2+-binding proteins.

Animals↗
PubMed1996

Biochemical characterization of calsequestrin-binding 30-kDa protein in sarcoplasmic reticulum of skeletal muscle.

Calsequestrin (CSQ)-binding 30-kDa protein in the sarcoplasmic reticulum (SR) of rabbit skeletal muscle was purified from the junctional face membrane (JFM) in the SR. Analysis of proteins which bound to the affinity column conjugated with the purified 30-kDa protein was performed. As a result, in the heavy fraction of the SR (HSR), four proteins including CSQ proved to be adsorbed on the column, and in the JFM, one protein, whose molecular weight was about 25-kDa. was mainly adsorbed. Furthermore, the same 25-kDa protein was found to be adsorbed on the CSQ affinity column. This 25-kDa protein is probably the CSQ-binding 26-kDa protein (junctin) recently reported [Jones, L. R., et al. (1995) J. Biol. Chem. 270, 30787] judging from the molecular weight and the CSQ-binding property. These results suggest that three proteins, CSQ, 30-kDa protein, and 25-kDa protein, form a protein complex in the terminal cisternae of the SR.

Animals↗
PubMed2000

Site-directed mutagenesis and deletion of three phosphorylation sites of calsequestrin of skeletal muscle sarcoplasmic reticulum. Effects on intracellular targeting.

Calsequestrin (CS) is segregated to the junctional sarcoplasmic reticulum (jSR) of skeletal muscle fibers and is responsible for intraluminal Ca(2+) binding. A chimeric CS-HA1, obtained by adding the nine-amino-acid viral epitope hemagglutinin (HA1) to the carboxy-terminal of CS and shown to be correctly segregated to skeletal muscle jSR in vivo (A. Nori, K. A. Nadalini, A. Martini, R. Rizzuto, A. Villa, and P. Volpe, 1997, Am. J. Physiol. 272, C1420-C1428), is mutagenized in order to identify domains of CS involved in targeting. Since a putative targeting mechanism of CS implies phosphorylation-dependent steps in the endoplasmic reticulum (ER) and/or Golgi complex, five CS-HA1 mutants disrupting the three phosphorylation sites of CS (Thr(189), Thr(229), and Thr(353)) were engineered by either site-directed mutagenesis or deletion: CS-HA1DeltaP1 (Thr(189) --> Ile); CS-HA1DeltaP2 (Thr(229) --> Asn); CS-HA1DeltaP1,2; in which Thr(189) and Thr(229) were changed to Ile and Asn, respectively; and CS-HA1Delta14(COOH) and CS-HA1Delta49 (COOH), in which 14 residues (Glu(354)-Asp(367)) and 49 residues (Asp(319)-Asp(367)), respectively, were deleted at the carboxy-terminal. Mutant cDNAs were transiently transfected in either HeLa cells, cultured myoblasts of rat skeletal muscle, or regenerating soleus muscle fibers of adult rats. Each CS-HA1 mutant was identified by Western blot as a single polypeptide of the predicted molecular weight. The intracellular localization of CS-HA1 mutants was studied by immunofluorescence using specific antibodies against either CS or HA1. CS-HA1 mutants colocalized with ER markers, e.g., calreticulin, and partially overlapped with Golgi complex markers, e.g., alpha-mannosidase II, in HeLa cells and myotubes. CS-HA1 mutants were expressed and retained in ER and ER/SR of HeLa cells and myotubes, respectively, and correctly segregated to jSR of regenerating soleus muscle fibers. Thus, the targeting mechanism of CS in vivo is not affected by phosphorylation(s); i.e., sorting and segregation of CS appear to be independent of posttranslational phosphorylation(s).

Animals↗
PubMed1993

Postnatal development of rabbit fast-twitch skeletal muscle: accumulation, isoform transition and fibre distribution of calsequestrin.

The time-course of disappearance of slow-cardiac calsequestrin (CS) and that of appearance of the skeletal CS isoform were investigated in developing fast-twitch skeletal muscle of the rabbit between postnatal days 1 and 60, along with changes in density of the ryanodine receptor (RyR)/Ca2+ release channel. Western blot data on skeletal muscle membranes, purification of two CS isoforms by phenyl-Sepharose chromatography, and their immunolocalization in muscle fibres, all show that both CS isoforms are coexpressed in neonatal muscles. Our results, at the protein level, indicate that the turning off of synthesis of cardiac CS and its total disappearance from fast-twitch fibres take place at critical periods between two and four weeks postnatally, i.e. past changes in the respective mRNA. In contrast, the accumulation in muscle membranes of both the RyR and the skeletal CS isoform proceeds steadily up to one month, to reach adult values at about two months of age. These findings seem to argue that myogenic factors, in addition to the morphogenetic influence on the sarcoplasmic reticulum from the neural input to the muscle, may be involved in the developmental transition of CS isoforms in mammalian fast-twitch muscle fibres.

Animals↗
PubMed1986

Distribution of sarcoplasmic reticulum Ca-ATPase and of calsequestrin in rabbit and rat skeletal muscle fibers.

Muscle fibers in rabbit extensor digitorum longus (EDL), tibialis anterior (TA) and soleus, and rat soleus, were examined immunohistochemically for two proteins of the sarcoplasmic reticulum. Ca-ATPase and calsequestrin (CaS). Fibers were typed with the histochemical reaction for actomyosin ATPase. In the rabbit EDL and TA, type I fibers clearly reacted less for Ca-ATPase and CaS than type II fibers, but the difference was less with CaS than with Ca-ATPase. Although the differences were relatively small, IIB fibers consistently presented greater amounts of Ca-ATPase than IIA fibers. No type II subgroups could be recognized after incubation with anti-CaS. These findings confirm results from previous immunochemical measurements on whole muscles containing different proportions of IIA and IIB fibers (Leberer and Pette 1986). Type IIA and IIC in the rabbit and rat soleus reacted stronger for Ca-ATPase and for CaS than type I fibers. Small differences in Ca-ATPase, but not in CaS, were recognized within the type I fiber population. Therefore, type I fibers in the rabbit and rat soleus are not a homogeneous population.

Animals↗
PubMed1988

Distribution of sarcoplasmic reticulum Ca-ATPase and of calsequestrin at the polar regions of rat, rabbit and cat intrafusal fibers.

Sarcoplasmic reticulum (SR) Ca2+-pumping ATPase (Ca-ATPase) and calsequestrin (CaS) were visualized by indirect immunofluorescence at the polar regions of adult rat, rabbit and cat intrafusal fibers. The immunohistochemical reaction products were regarded as histochemical markers of the SR and as valid indicators of the distribution of the two Ca2+-sequestering proteins. Static nuclear bag2 fibers displayed lower levels of both Ca-ATPase and CaS than the other two intrafusal fiber types. Nuclear chain fibers presented the highest Ca-ATPase levels and, together with dynamic nuclear bag1 fibers, they also exhibited relatively high amounts of CaS. The level of Ca-ATPase was lower in bag 1 fibers than in nuclear chain fibers, but not as low as in bag2 fibers. The comparatively high levels of Ca-ATPase and CaS seen in nuclear chain fibers coincided with their reported faster contractile speeds compared to nuclear bag fibers.

Animals↗
PubMed1990

Coexpression of two isoforms of calsequestrin in rabbit slow-twitch muscle.

The cardiac and fast-twitch skeletal muscle forms of the Ca2(+)-binding protein calsequestrin (CS) are the products of two different genes, both of which are transcribed in slow-twitch skeletal muscle, though at much different rates (Scott et al., 1988., Fliegel et al., 1989). We have investigated this problem more closely at the protein level, on isolated terminal cisternae (TC) of the sarcoplasmic reticulum (SR) of rabbit slow-twitch muscle, and following purification of two distinct forms of CS from whole tissue by DEAE-Cellulose chromatography and CA2(+)-dependent elution from phenyl-Sepharose. Two electrophoretically (apparent molecular mass of 64 kDa and 54 kDa, respectively), and antigenically distinct forms of CS, here shown to be related to the fast-twitch skeletal muscle and to cardiac-type isoform of CS, respectively, colocalize to junctional TC of slow-twitch muscle. The cardiac-type isoform that is expressed in slow-twitch muscle accounts for about 25% of total CS present in isolated TC, it binds Ca2+ as effectively as the major CS form, using a 45Ca-overlay technique, and it shares extensive similarities with dog cardiac CS, not only in size and antigenically, but also in pl, as well as in the DEAE-elution characteristics. No difference in behaviour with phenyl-Sepharose resin were observed between the two CS isoforms from slow-twitch muscle.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acids↗
PubMed1990

Specific protein-protein interactions of calsequestrin with junctional sarcoplasmic reticulum of skeletal muscle.

Minor protein components of triads and of sarcoplasmic reticulum (SR) terminal cisternae (TC), i.e. 47 and 37 kDa peptides and 31-30 kDa and 26-25 kDa peptide doublets, were identified from their ability to bind 125I calsequestrin (CS) in the presence of EGTA. The CS-binding peptides are specifically associated with the junctional membrane of TC, since they could not be detected in junctional transverse tubules and in longitudinal SR fragments. The 31-30 kDa peptide doublet, exclusively, did not bind CS in the presence of Ca2+. Thus, different types of protein-protein interactions appear to be involved in selective binding of CS to junctional TC.

Animals↗
PubMed1990

Identification of a region of calsequestrin that binds to the junctional face membrane of sarcoplasmic reticulum.

The interaction of calsequestrin (CSQ) with the channel-containing region of the sarcoplasmic reticulum (junctional face membrane, jfm) is involved in Ca2+ release, and it seemed of interest to identify the jfm-binding region of the CSQ molecule. For this purpose, CSQ was digested with trypsin, and peptides were screened for jfm binding. Partial amino acid sequencing of selected peptides allowed us to localize a critical site for jfm binding in the stretch encompassing residues 86-191.

Amino Acid Sequence↗