Vitamin D-Regulated, ATP-Dependent Calcium Transport by Intestinal Golgi Vesicles during Maturation in the Rat

Arab, Noushin

doi:10.1203/00006450-198907000-00017

Cited by 3 publications

(4 citation statements)

References 14 publications

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“…These results are similar to those reported for ATP-dependent calcium uptake by the Golgi in Sprague-Dawley rats (19). The requirement for the hydrolysis of ATP was shown by the lack of stimulation of calcium uptake in the presence of AMP-PCP, a nonhydrolyzable ATP analogue.…”

Section: Discussionsupporting

confidence: 80%

“…Calcium sequestration within the cytosol occurs by equilibrium binding to high affinity sites on cytosolic membrane or soluble protein (28,29) or by active transport to subcellular organelles (19,30,31 Our studies demonstrate that the time course of calcium uptake in the presence of ATP was stimulated several-fold compared with that in the absence of ATP in SHR and WKY. These results are similar to those reported for ATP-dependent calcium uptake by the Golgi in Sprague-Dawley rats (19).…”

Section: Discussionmentioning

confidence: 83%

“…To our knowledge, there are no studies to address the cytosolic movement of calcium within the enterocytes. Because the Golgi apparatus plays a major role in intracellular calcium handling (19,20) and abnormalities in intracellular calcium handling have been reported in tissues of SHR (2 I), we postulated that calcium uptake by Golgi apparatus might be abnormal.Therefore, our studies were designed to characterize calcium transport by intestinal Golgi of the SHR and their genetically matched control, WKY. Furthermore, calcium uptake was studied before (3-wk-old rats) and after development of hypertensive state (1 2-wk-old).…”

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confidence: 99%

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Ontogeny of Calcium Transport By Intestinal Golgi in Spontaneously Hypertensive Rats and Genetically Matched WKY Rats

Shibata

1990

Pediatr Res

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ABSTRACT. Our studies were designed to characterize calcium transport by intestinal Golgi vesicles in spontaneously hypertensive rats (SHR) and their genetically matched control, Wistar-Kyoto rats (WKY). The biochemical purity of the intestinal Golgi in SHR and WKY was validated by marker enzyme studies. Calcium uptake by Golgi vesicles represented transport into the intravesicular space as evidenced by temperature dependency and by calcium ionophore A23187-induced calcium efflux experiments. ATP-driven calcium uptake was stimulated severalfold compared with uptake in the absence of ATP and adenylyl-(/3-7-rnethylendiphosphate) (nonhydrolyzable ATP) in both SHR and WKY. ATP-dependent calcium uptake was significantly higher in WKY compared with SHR at early times points, 15 s-5 min ( p < 0.05-0.01). The initial rate of calcium uptake was linear up to 60 s. Epidemiologic studies suggested an inverse relationship between blood pressure and dietary calcium intake (1-5). Oral calcium supplementation in humans resulted in reduction in blood pressure (6). Furthermore, low serum level of ionized calcium has been described in humans with essential hyperten- Supported by Grant no. NIH HL3796 1. sion (7). These studies suggest an alteration of calcium homeostasis in humans with essential hypertension.The SHR is the most widely used animal model of human essential hypertension (8). Calcium metabolism in SHR has been shown by several studies to be abnormal. These abnormalities include reduced serum ionized calcium, increased serum parathormone levels, hypercalciuria, and abnormal vitamin D metabolism (9-16). Studies on calcium transport using in vivo and in vitro techniques, in general, have shown decreased calcium uptake by the small intestine of the SHR when compared with WKY (12,15,16,17,18). Calcium transport across the enterocyte, however, represents three steps that include: entry across brush border membrane, cytosolic movement, and exit of the basolateral membrane. To our knowledge, there are no studies to address the cytosolic movement of calcium within the enterocytes. Because the Golgi apparatus plays a major role in intracellular calcium handling (19,20) and abnormalities in intracellular calcium handling have been reported in tissues of SHR (2 I), we postulated that calcium uptake by Golgi apparatus might be abnormal.Therefore, our studies were designed to characterize calcium transport by intestinal Golgi of the SHR and their genetically matched control, WKY. Furthermore, calcium uptake was studied before (3-wk-old rats) and after development of hypertensive state (1 2-wk-old). MATERIALS AND METHODS Animals and materials.Both SHR and WKY were obtained from Taconic Farms (Germantown, NY). Adult rats (12-14 wk old) and weanling rats (21 + 1 d old) were used to prepare the intestinal Golgi vesicles. Adult and weanling rats were fed a regular diet that contained 1.2% calcium, 0.8 phosphate, and 1700 U/ 100 g of ergocalciferol (Teklad Diets, Madison, WI). 45Ca (0.37-1.5 GBq/mg) was obtained from New England Nuclear C...

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Section: Discussionsupporting

confidence: 80%

Section: Discussionmentioning

confidence: 83%

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confidence: 99%

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confidence: 99%

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Ontogeny of Calcium Transport By Intestinal Golgi in Spontaneously Hypertensive Rats and Genetically Matched WKY Rats

Shibata

1990

Pediatr Res

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PMR1, a Ca2+-ATPase in Yeast Golgi, Has Properties Distinct from Sarco/endoplasmic Reticulum and Plasma Membrane Calcium Pumps

Sorin

Rosas

Rao

1997

Journal of Biological Chemistry

238

246

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PMR1, a P-type ATPase cloned from the yeast Saccharomyces cerevisiae, was previously localized to the Golgi, and shown to be required for normal secretory processes (Antebi, A., and Fink, G.R. (1992) Mol. Biol. Cell 3, 633-654). We provide biochemical evidence that PMR1 is a Ca 2؉ -transporting ATPase in the Golgi, a hitherto unusual location for a Ca 2؉ pump. As a starting point for structure-function analysis using a mutagenic approach, we used the strong and inducible heat shock promoter to direct high level expression of PMR1 from a multicopy plasmid. Yeast lysates were separated on sucrose density gradients, and fractions assayed for organellar markers. PMR1 is found in fractions containing the Golgi marker guanosine diphosphatase, and is associated with an ATP-dependent, protonophore-insensitive 45 Ca 2؉ uptake activity. This activity is virtually abolished in the absence of the expression plasmid. Furthermore, replacement of the active site aspartate within the phosphorylation domain had the expected effect of abolishing Ca 2؉ transport activity entirely. Interestingly, the mutant enzymes (Asp-371 3 Glu and Asp-371 3 Asn) demonstrated proper targeting to the Golgi, unlike analogous mutations in the related yeast H ؉ -ATPase. Detailed characterization of calcium transport by PMR1 showed that sensitivity to inhibitors (vanadate, thapsigargin, and cyclopiazonic acid) and affinity for substrates (MgATP and Ca 2؉ ) were different from the previously characterized sarco/endoplasmic reticulum and plasma membrane Ca 2؉ -ATPases. PMR1 therefore represents a new and distinct P-type Ca 2؉ -ATPase. Because close homologs of PMR1 have been cloned from rat and other organisms, we suggest that Ca 2؉ -ATPases in the Golgi will form a discrete subgroup that are important for functioning of the secretory pathway.In eukaryotic cells, the vast bulk of cellular calcium is sequestered within intracellular calcium stores, which maintain cytoplasmic calcium ion concentrations at submicromolar levels and release calcium in response to physiological signals. A major intracellular calcium pool is the endoplasmic reticulum, which is well known for its prominent role in inositol 1,4,5-trisphosphate-and caffeine-mediated calcium release (2). Filling of this store is accomplished by a thapsigargin-sensitive Ca 2ϩ -ATPase, a member of the ubiquitous family of P-type ion pumps, and best characterized by the isoform in skeletal muscle sarcoplasmic reticulum (SERCA1 1 ; Refs. 3 and 4). There are data supporting the existence of another ionomycin-sensitive pool of intracellular calcium that is unresponsive to both inositol 1,4,5-trisphosphate and caffeine, is non-mitochondrial, and appears to be loaded by a thapsigargin-insensitive Ca 2ϩ

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Developmental Expression of Calcitriol Receptors, 9-Kilodalton Calcium-Binding Protein, and Calcidiol 24-Hydroxylase in Human Intestine

et al. 1996

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Human intestinal mucosa consists of highly active epithelial cells in continual renewal and differentiation processes located at different portions of the villi. The crypt contains abundant replicating cells which, upon reaching the villus tip, acquire their fully differentiated state. Besides its well recognized role in bone cell homeostasis, calcitriol has been attributed a role in cellular differentiation and proliferation in normal leukocytes and myeloid leukemia cells. We have previously documented the presence and the distribution of specific calcitriol receptors in the cells of the small and large intestine from 13-20-wk-old human fetuses and that calcitriol was able to promote human intestinal epithelium proliferation or differentiation, in organ culture, depending upon fetal age. We now show that, whereas transcripts for calcitriol receptors are abundant from duodenum to colon, those for the 9-kD calcium-binding protein are present mainly in the duodenum and the jejunum and to a lesser extent in the ileum and the colon. Transcripts for 25-hydroxycholecalciferol-24-hydroxylase could not be detected in any of the intestine segments despite a prolonged exposition of the gels. Immunofluorescence staining for the 9-kD calcium-binding protein was exclusively observed in the epithelial cells of the small intestine and colon, the subepithelial layers being always negative. The 9-kD calcium-binding protein distribution along the crypt-villus axis appeared as a gradient, increasing from the developing crypt to the tip of the villus in the duodenum, jejunum, and ileum. Based on the present observations and on the fact that calcitriol promotes human fetal proliferation and differentiation, the presence of transcripts for calcitriol receptors and 9-kD calcium-binding protein in the intestinal cell opens interesting possibilities as of their role in the in utero human gut development and the control of colorectal cancers.

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Vitamin D-Regulated, ATP-Dependent Calcium Transport by Intestinal Golgi Vesicles during Maturation in the Rat

Cited by 3 publications

References 14 publications

Ontogeny of Calcium Transport By Intestinal Golgi in Spontaneously Hypertensive Rats and Genetically Matched WKY Rats

Ontogeny of Calcium Transport By Intestinal Golgi in Spontaneously Hypertensive Rats and Genetically Matched WKY Rats

PMR1, a Ca2+-ATPase in Yeast Golgi, Has Properties Distinct from Sarco/endoplasmic Reticulum and Plasma Membrane Calcium Pumps

Developmental Expression of Calcitriol Receptors, 9-Kilodalton Calcium-Binding Protein, and Calcidiol 24-Hydroxylase in Human Intestine

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