Characterization, localization and axial distribution of Ca2+ signalling receptors in the rat submandibular salivary gland ducts.

Xu, Xin; Diaz, Julie; Zhao, Hong; Muallem, Shmuel

doi:10.1113/jphysiol.1996.sp021246

Cited by 57 publications

(60 citation statements)

References 30 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The sections were plated on polylysine-coated slides, dried, and kept at Ϫ20°C until use. A mixture of acini and duct fragments from all glands were prepared by published procedures (4,10,20). The cells were kept suspended in cold PSA until use.…”

Section: Methodsmentioning

confidence: 99%

See 1 more Smart Citation

Polarized Expression of Ca2+ Channels in Pancreatic and Salivary Gland Cells

Lee¹,

Xu²,

Zeng³

et al. 1997

Journal of Biological Chemistry

267

200

View full text Add to dashboard Cite

In polarized epithelial cells [Ca 2؉ ] i waves are initiated in discrete regions and propagate through the cytosol. The structural basis for these compartmentalized and coordinated events are not well understood. In the present study we used a combination of [Ca 2؉ ] i imaging at high temporal resolution, recording of Ca 2؉ -activated Cl ؊ current, and immunolocalization by confocal microscopy to study the correlation between initiation and propagation of [Ca 2؉ ] i waves and localization of Ca 2؉ release channels in pancreatic acini and submandibular acinar and duct cells. In all cells Ca 2؉ waves are initiated in the luminal pole and propagate through the cell periphery to the basal pole. All three cell types express the three known inositol 1,4,5-trisphosphate receptors (IP 3 Rs). Expression of IP 3 Rs was confined to the area just underneath the luminal and lateral membranes, with no detectable receptors in the basal pole or other regions of the cells. In pancreatic acini and SMG ducts IP 3 R3 was also found in the nuclear envelope. Expression of ryanodine receptor was detected in submandibular salivary gland cells but not pancreatic acini. Accordingly, cyclic ADP ribose was very effective in mobilizing Ca 2؉ from internal stores of submandibular salivary gland but not pancreatic acinar cells. Measurement of [Ca 2؉ ] i and localization of IP 3 Rs in the same cells suggests that only a small part of IP 3 Rs participate in the initiation of the Ca 2؉ wave, whereas most receptors in the cell periphery probably facilitate the propagation of the Ca 2؉ wave. The combined results together with our previous studies on this subject lead us to conclude that the internal Ca 2؉ pool is highly compartmentalized and that compartmentalization is achieved in part by polarized expression of Ca 2؉ channels.

show abstract

Section: Methodsmentioning

confidence: 99%

“…2 shows WB analysis of the different IP 3 R in pancreatic acini and SMG duct and acinar cells. For this we took advantage of our technique for separation between SMG acinar and duct cells, which yield better than 95% pure duct and acinar preparations (20). IP 3 Rs in all cells were sensitive to proteolysis.…”

Section: Properties Of [Ca 2ϩ ] I Waves In Smg Cellsmentioning

confidence: 99%

Polarized Expression of Ca2+ Channels in Pancreatic and Salivary Gland Cells

Lee¹,

Xu²,

Zeng³

et al. 1997

Journal of Biological Chemistry

267

200

View full text Add to dashboard Cite

show abstract

“…As in many cell types, Tg and other inhibitors of SERCA pumps release Ca 2ϩ from internal stores of pancreatic acinar and SMG cells (8,12). Again, the use of isolated endoplasmic reticulum vesicles shows the presence of Tg-sensitive Ca 2ϩ pumping activity in pancreatic acinar cells (10,13).…”

mentioning

confidence: 99%

“…However, a recent study in which external [Ca 2ϩ ] was measured suggested that Ca 2ϩ pumping across the luminal membrane dominates Ca 2ϩ efflux in stimulated acinar cells (11). This predicts that the luminal membrane expresses high levels of PMCA.As in many cell types, Tg and other inhibitors of SERCA pumps release Ca 2ϩ from internal stores of pancreatic acinar and SMG cells (8,12). Again, the use of isolated endoplasmic reticulum vesicles shows the presence of Tg-sensitive Ca 2ϩ pumping activity in pancreatic acinar cells (10, 13).…”

mentioning

confidence: 99%

Polarized Expression of Ca2+ Pumps in Pancreatic and Salivary Gland Cells

Lee¹,

Xu²,

Zeng³

et al. 1997

Journal of Biological Chemistry

180

139

View full text Add to dashboard Cite

The present study was aimed at localization of plasma membrane (PMCA) and intracellular (SERCA) Ca 2؉ pumps and characterizing their role in initiation and propagation of Ca 2؉ waves. Specific and polarized expression of Ca 2؉ pumps was observed in all epithelial cells examined. Immunolocalization revealed expression of PMCA in both the basolateral and luminal membranes of all cell types. SERCA2a appeared to be expressed in the luminal pole, whereas SERCA2b was expressed in the basal pole and the nuclear envelope of pancreatic acini. Interestingly, SERCA2b was found in the luminal pole of submandibular salivary gland acinar and duct cells. These cells expressed SERCA3 in the basal pole. To examine the significance of the polarized expression of SERCA and perhaps PMCA pumps in secretory cells, we compared the effect of inhibition of SERCA pumps with thapsigargine and partial Ca 2؉ release with ionomycin on Ca 2؉ release evoked by agonists and Ca 2؉ uptake induced by antagonists. Despite their polarized expression, Ca 2؉ uptake by SERCA pumps and Ca 2؉ efflux by PMCA resulted in uniform reduction in [Ca 2؉ ] i . Surprisingly, inhibition of the SERCA pumps, but not Ca 2؉ release by ionomycin, eliminated the distinct initiation sites and propagated Ca 2؉ waves, leading to a uniform increase in [Ca 2؉ ] i . In addition, inhibition of SERCA pumps reduced the rate of Ca 2؉ release from internal stores. The implication of these findings to rates of Ca 2؉ diffusion in the cytosol, compartmentalization of Ca 2؉ signaling complexes, and mechanism of Ca 2؉ wave propagation are discussed.The agonist-evoked Ca 2ϩ signal is governed by the coordinated action of Ca 2ϩ channels and Ca 2ϩ pumps (1). In recent years it has become clear that [Ca 2ϩ ] i changes occur in the form of elemental events emanating in specialized microdomains and propagating as Ca 2ϩ waves (see reviews in Ref. 2). Such behavior was also described in pancreatic acinar cells (3-6) in which the [Ca 2ϩ ] i wave is initiated in the luminal pole (LP) 1 and propagates to the basal pole. In the preceding manuscript (7) we showed similar phenomena in SMG acinar and duct cells. Characterization and localization of Ca 2ϩ release channels in the three cell types (7) suggests that the channels determine the initiation site and pattern of the [Ca 2ϩ ] i waves. Thus, the cells express all three types of IP 3 R and the SMG cells also express the ryanodine receptor. Expression of the receptors appears to be confined to the area just underneath the luminal and lateral membranes (7).The type of Ca 2ϩ pumps expressed in each cell type and their role in control of the [Ca 2ϩ ] i wave is not known. Functional studies showed the presence of PMCA in pancreatic acini (8, 9), which is activated by agonist stimulation (8). In several studies isolated membranes and vesicles were used to localize the PMCA in the basolateral membrane of these cells (10). However, a recent study in which external [Ca 2ϩ ] was measured suggested that Ca 2ϩ pumping across the luminal membrane dominat...

show abstract

“…Several G s -coupled receptors can activate dual signaling cascades. For example, increases in both cAMP and [Ca 2ϩ ] i have been observed by histamine acting on H 2 receptors in parietal cells (5), parathyroid hormone acting on osteoblasts (6), and isoprenaline acting on cardiac myocytes (7) or salivary gland cells (8,9). In contrast to the simple paradigm that each receptor molecule can activate a single class of G protein (10), activation of more than one signaling cascade could be due to coupling of one receptor type to two classes of G proteins.…”

mentioning

confidence: 99%