Role of phosphoinositides in stimulus-secretion coupling

Schulz, Irene; Schnefel, Susanne; Banfíƈ, Hrvoje

doi:10.1007/bf00487883

Cited by 1 publication

(5 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Furthermore, it was shown that GTP[S] inhibited the GTP-triggered Ca2" release [12]. In agreement with previous results [22], GTP [S] augmented, rather than inhibited, the hormone-evoked Ca2" release from permeabilized pancreatic acini (Fig. 7).…”

Section: Discussionsupporting

confidence: 92%

“…It was also shown that PLC is a GTP-dependent enzyme where GTP stimulates PLC-mediated hydrolysis of Ptd-Ins(4,5)P2 [11,[19][20][21][22]. Thus, one mechanism by which GTP can activate intracellular Ca2+ pumps is through the activation of PLC.…”

Section: Discussionmentioning

confidence: 99%

“…Indeed, GTP and GTP[S] were shown to stimulate the release of [3H1Ins(1,4,5)P3 from permeabilized pancreatic acinar cells. labelled with [3H]inositol [22]. The increased levels of DAG should result in activation of PKC.…”

Section: Discussionmentioning

confidence: 99%

“…It was previously shown that Ca2"-mobilizing hormones, GTP and GTP[S] can stimulate the production of Ins(l ,4,5)P3 by permeabilized pancreatic acinar cells [22]. We therefore reason that our ability to measure pump stimulation is due to a rapid hydrolysis of Ins(1,4,5)P3 which is generated during the incubation of the acini with hormones, GTP or GTP[S].…”

Section: Shows the Fraction Of V042--inhibitablementioning

confidence: 98%

“…In the present studies we used this cell system to evaluate the contribution of Ins(1,4,5)P3 and protein kinase C (PKC) by phorbol esters results in stimulation of an intracellular Ca2" pump thought to be located in the membrane of the endoplasmic reticulum [18]. Stimulation of PKC requires the action of phospholipase C (PLC), a GTP-activated enzyme [19][20][21][22]. Hence it is possible that GTP and its analogues could indirectly stimulate the intracellular Ca2" pump through the activation of PLC.…”

Section: Introductionmentioning

confidence: 99%

See 4 more Smart Citations

Relationship between hormonal, GTP and Ins(1,4,5)P3-stimulated Ca2+ uptake and release in pancreatic acinar cells

Muallem¹,

Beeker

1989

Biochemical Journal

View full text Add to dashboard Cite

Electrically permeabilized rat pancreatic acini were used to evaluate the contributions of GTP and Ins(1,4,5) P3 to hormone-stimulated Ca2+ uptake and release from intracellular pools. Treatment of permeabilized acini with Ca2+-mobilizing hormones, GTP or GTP[S] resulted in stimulation of an ATP-dependent, VO4(2-)-sensitive Ca2+ uptake into a non-mitochondrial intracellular pool. GTP and GTP[S] also augmented the hormone-mediated stimulation of Ca2+ uptake. Including oxalate in the uptake medium increased Ca2+ uptake into this pool but did not modify the stimulation of Ca2+ uptake induced by hormones or GTP. Ins(1,4,5)P3 released all the extra Ca2+ accumulated as a result of hormone, GTP or GTP[S] stimulation. Hence, these stimuli activated the Ca2+ pump localized in the membrane of the hormone and Ins(1,4,5)P3-sensitive Ca2+ pool. Including 2,3-diphosphoglyceric acid (PGA) [an inhibitor of Ins(1,4,5)P3 hydrolysis] in the incubation medium blunted the GTP and GTP[S]-stimulated Ca2+ uptake. In the presence of PGA, the hormones inhibited Ca2+ accumulation, and GTP and GTP[S] augmented this effect. Accordingly, PGA stabilized the Ins(1,4,5)P3-evoked Ca2+ release from intracellular pools. Only in the presence of PGA was it possible to demonstrate hormonally-evoked Ca2+ release from permeabilized cells. GTP, and more importantly GTP[S], augmented the hormone-evoked Ca2+ release. Hormones and Ins(1,4,5)P3 in the presence or absence of GTP or GTP[S] released Ca2+ from the same intracellular pool. The extent of Ca2+ release caused by the combination of hormones and GTP or GTP[S] was similar to that evoked by Ins(1,4,5)P3 alone. Taken together, these results suggest that GTP or GTP[S] facilitates stimulation of phospholipase C by hormones. Such stimulation results in stimulation of protein kinase C and increased levels of Ins(1,4,5)P3 and is sufficient to explain the effects of GTP and GTP[S] on Ca2+ uptake and release from pancreatic acinar cells.

show abstract

Section: Discussionsupporting

confidence: 92%