Endoplasmic reticulum Ca2+-ATPase pump is up-regulated in calcium-transporting dental enamel cells: a non-housekeeping role for SERCA2b

Franklin, Isobel; Winz, Robert A.; Hubbard, Michael J.

doi:10.1042/bj3580217

Cited by 31 publications

(30 citation statements)

References 40 publications

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“…During PDGF-induced SMC proliferation, SERCA2a expression was up-regulated while SERCA2b expression was unchanged (6). However, the concept of a exclusive housekeeping role of SERCA2b has recently been questioned as it has become clear that SERCA2b could be the only SERCA isoform expressed by highly differentiated cells (31). Recent results from our laboratory support this new standpoint: the thyrocyte is similar to enamel cells in that it is a highly differentiated cell expressing almost exclusively SERCA2b (20).…”

Section: Discussionsupporting

confidence: 66%

“…Total RNA (20 mg) was analyzed by electrophoresis on a 1.2% formaldehyde agarose gel and blotted onto nitrocellulose membranes (BioRad, Hercules, CA, USA). Filters were washed twice in 10 ml 2 £ SSPE (0.3 M NaCl, 0.02 M NaH 2 PO 4 and 0.002 M EDTA), incubated for 5 h at 42 8C in 10 ml pre-hybridization buffer (50% formamide, 5 £ SSPE, 2 £ Denhardt's, 0.2% SDS and 100 mg/ml sonicated denaturated salmon sperm DNA) and then for 16 h in 10 ml of the same buffer with 1 £ 10 7 c.p.m./ml of a [ 32 P]-dATPlabeled specific probe encompassing bp 2074-2590 of rat SERCA2b cDNA (31). After the hybridization step, filters were washed twice at room temperature in 10 ml 2 £ SSPE and 0.2% SDS and once at 42 8C in the same washing buffer.…”

Section: Rna Extraction and Northern Blot Experimentsmentioning

confidence: 99%

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TSH/cAMP up-regulate sarco/endoplasmic reticulum Ca2+-ATPases expression and activity in PC Cl3 thyroid cells

Ulianich¹,

Secondo

Micheli

et al. 2004

European Journal of Endocrinology

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Objective: We recently reported that the sarco/endoplasmic reticulum Ca 2þ -ATPase (SERCA) 2b is the SERCA form preferentially expressed in rat thyroid. Moreover, SERCA2b expression dramatically decreases in virally transformed, highly tumorigenic, PC Cl3 thyroid cells. These results suggest that, in the thyroid, SERCA2b, in addition to its housekeeping role, is linked to differentiation and is a regulated gene. We therefore sought to study the effect of TSH, the main regulator of thyroid function, on SERCA2b expression and activity. Methods: PC Cl3 cells were hormone starved in low-serum medium and stimulated for long (48 h) or short (1, 2 and 4 h) times. SERCA2b expression and activity were evaluated by Northern and Western blots, Ca 2þ -ATPase activity and Ca 2þ store content. Results: In PC Cl3 cells, SERCA2b mRNA and protein were induced twofold by a 48-h long treatment with TSH. Long-term elevation (48 h) of intracellular cAMP levels, by forskolin or 8-Br-cAMP, had similar effects on SERCA2b mRNA and protein. We also measured Ca 2þ -ATPase activity and Ca 2þ store content. Both long (48 h) and short (0.5-1 h) treatments with TSH, forskolin or 8-Br-cAMP induced a marked increase of SERCA2b activity. This effect was completely abolished by H89, a specific inhibitor of cAMP-dependent protein kinase A (PKA). TSH and 8-Br-cAMP increased Ca 2þ store content after both long (48 h) and short (1 -2 h) treatments. Conclusions: These data suggested that TSH/cAMP acts as an important regulator of both SERCA2b expression and activity in the thyroid system, through PKA activation.European Journal of Endocrinology 150 851-861

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Section: Discussionsupporting

confidence: 66%

Section: Rna Extraction and Northern Blot Experimentsmentioning

confidence: 99%

TSH/cAMP up-regulate sarco/endoplasmic reticulum Ca2+-ATPases expression and activity in PC Cl3 thyroid cells

Ulianich¹,

Secondo

Micheli

et al. 2004

European Journal of Endocrinology

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“…Here, it is shown that SERCA 2b activity is stimulated by P2-purinergic agonists through the PLC-PKC pathway. These results strengthen the concept that SERCA 2b, in highly differentiated cells, such as thyroid (Pacifico et al 2003) or enamel cells (Franklin et al 2001), is regulated by various signal transduction pathways. This new standpoint extends our understanding of SERCA 2b function, considered until recently housekeeping at variance with that of SERCA 3 that varies with differentiation in several systems (Papp et al 1993, Gelebart et al 2002.…”

Section: Discussionsupporting

confidence: 72%

The sarcoplasmic–endoplasmic reticulum Ca2+ ATPase 2b regulates the Ca2+ transients elicited by P2Y2 activation in PC Cl3 thyroid cells

Ulianich¹,

Elia

Treglia

et al. 2006

Journal of Endocrinology

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In PC Cl3 cells, a continuous, fully differentiated rat thyroid cell line, P2Y 2 purinoceptor activation provoked a transient increase of [Ca 2C ] i , followed by a decreasing sustained phase. The a and b1 protein kinase C (PKC) inhibitor Gö 6976 decreased the rate of decrement to the basal [Ca 2C ] i level and increased the peak of Ca 2C entry of the P2Y 2 -provoked Ca 2C transients. These effects of Gö 6976 were not caused by an increased permeability of the plasma membrane, since the Mn 2C and Ba 2C uptake were not changed by Gö 6976. Similarly, the Na C /Ca 2C exchanger was not implicated, since the rate of decrement to the basal [Ca 2C ] i level was equally decreased in physiological and Na C -free buffers, in the presence of Gö 6976. On the contrary, the activity of the sarcoplasmic-endoplasmic reticulum Ca 2C ATPase (SERCA) 2b was profoundly affected by Gö 6976 since the drug was able to completely inhibit the stimulation of the SERCA 2b activity elicited by P2-purinergic agonists. Finally, the PKC activator phorbol myristate acetate had effects opposite to Gö 6976, in that it markedly increased the rate of decrement to the basal [Ca 2C ] i level after P2Y 2 stimulation and also increased the activity of SERCA 2b. These results suggest that SERCA 2b plays a role in regulating the sustained phase of Ca 2C transients caused by P2Y 2 stimulation.

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“…On the other hand, the 3-fold increased transport rate at maturation, quantified here for the first time (Fig. 3), closely matches the up-regulation of ER/Ca 2ϩ store machinery (12,14) and associated capacity for sequestering 45 Ca. 3 Collectively, the results of this study warrant further investigation of the calcium transcytosis paradigm in enamel cells.…”

Section: Discussionmentioning

confidence: 81%

“…Unexpectedly, however, proteome analysis revealed that calbindin 28kDa was down-regulated during maturation, whereas calcium-handling proteins from the endoplasmic reticulum (ER/Ca 2ϩ stores) 1 were elevated in parallel with calcium transport. These and other findings led us to postulate a "calcium transcytosis" mechanism whereby the ER serves as a transcellular pipeline for calcium (1,(12)(13)(14). Null mutant mice completely lacking calbindin 28kDa (15) constitute a powerful tool to pursue this stimulating possibility further.…”

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confidence: 99%

Calbindin Independence of Calcium Transport in Developing Teeth Contradicts the Calcium Ferry Dogma

Turnbull

Looi

Mangum

et al. 2004

Journal of Biological Chemistry

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Cytosolic calcium-binding proteins termed calbindins are widely regarded as a key component of the machinery used to transport calcium safely across cells. Acting as mobile buffers, calbindins are thought to ferry calcium in bulk and simultaneously protect against its potentially cytotoxic effects. Here, we contradict this dogma by showing that teeth and bones were produced normally in null mutant mice lacking calbindin 28kDa . Structural analysis of dental enamel, the development of which depends critically on active calcium transport, showed that mineralization was unaffected in calbindin 28kDa -null mutants. An unchanged rate of calcium transport was verified by measurements of 45 Ca incorporation into developing teeth in vivo. In enamelforming cells, the absence of calbindin 28kDa was not compensated by other cytosolic calcium-binding proteins as detectable by 45 Ca overlay, two-dimensional gel, and equilibrium binding analyses. Despite a 33% decrease in cytosolic buffer capacity, cytotoxicity was not evident in either the null mutant enamel or its formative cells. This is the first definitive evidence that calbindins are not required for active calcium transport, either as ferries or as facilitative buffers. Moreover, in challenging the broader notion of a cytosolic route for calcium, the findings support an alternative paradigm involving passage via calcium-tolerant organelles.The active transport of calcium across cells holds widespread importance in medicine and biology, yet the underlying mechanisms remain unclear. Operating in many places (e.g. gut, kidney, placenta, teeth, bones, oviduct, lung, inner ear), active transport is used to control the amount of calcium in body fluids and so impacts on nutrition, biomineralization, fertility, respiration, and hearing (1, 2). Superior control is achieved by passaging calcium actively through cells rather than passively between them, but this comes at the risk of cytotoxicity should the ability to regulate intracellular calcium be overburdened.Mechanistically, active transport is considered in three steps: the entry of calcium to the cell, transit across it, and extrusion at the other side. The transit step has received the most attention over several decades, being considered rate-limiting and having key molecular players defined. However, recent molecular characterization of calcium entry channels has transformed the field by providing a new mechanistic focus for vitamin D-restricted transport (3, 4). With these advances reigniting interest in therapeutic applications, it is important to revisit what happens following calcium entry.The 30-year-old paradigm that calcium is ferried through cytosol by mobile calcium-binding proteins (calbindins) remains widely accepted (3-9). Calbindins are thought to facilitate the naturally poor diffusion of calcium in cytosol and simultaneously buffer calcium at safe concentrations. Comprehensively supporting this view, tight correlations between calbindin expression and vitamin D-dependent transport were found in intestine...

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Endoplasmic reticulum Ca2+-ATPase pump is up-regulated in calcium-transporting dental enamel cells: a non-housekeeping role for SERCA2b

Cited by 31 publications

References 40 publications

TSH/cAMP up-regulate sarco/endoplasmic reticulum Ca2+-ATPases expression and activity in PC Cl3 thyroid cells

TSH/cAMP up-regulate sarco/endoplasmic reticulum Ca2+-ATPases expression and activity in PC Cl3 thyroid cells

The sarcoplasmic–endoplasmic reticulum Ca2+ ATPase 2b regulates the Ca2+ transients elicited by P2Y2 activation in PC Cl3 thyroid cells

Calbindin Independence of Calcium Transport in Developing Teeth Contradicts the Calcium Ferry Dogma

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