Effects of GTP on Ca2+ movements across endoplasmic reticulum membranes

Dawson, Alan P.; Comerford, J G

doi:10.1016/0143-4160(89)90060-2

Cited by 43 publications

(16 citation statements)

References 45 publications

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“…Furthermore, a physical interaction between this Ca 2+ pool and the Ins(1,4,5)P3-sensitive Ca 2+ pool was mediated by GTP. The latter observation supports previous findings in different cell types that GTP mediates the transfer of Ca 2+ from an Ins(1,4,5)P3-insensitive to an Ins(1,4,5)P3-sensitive Ca 2+ pool, thereby enlarging the Ins(1,4,5)P3-sensitive Ca 2+ pool and resulting in an enhanced Ca 2+ release following Ins(1,4,5)P3 stimulation [17][18][19][20]. The GTP evoked Ca 2+ release is probably an artifact due to the fact that the cells were permeabilized.…”

supporting

confidence: 79%

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca²⁺ from distinct intracellular pools in permeabilized lacrimal acinar cells

1995

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In permeabilized lacrimal acinar cells, cyclic ADPribose (cADP-ribose) and inositol 1,4,5-trisphosphate (Ins(1,4,5)P3) release Ca 2+ in a dose dependent manner from distinct tbapsigargin-sensitive Ca 2+ pools. Ryanodine specifically blocks the Ca 2+ response to cADP-ribose, whereas heparin strongly reduces the response to Ins(1,4,5)P3 application. GTP causes a rapid Ca z+ release by a ryanodine-and heparin-insensitire mechanism and potentiates Ins(1,4,5)P 3 but not cADP-ribose evoked Ca 2+ release. It is estimated that cADP-ribose can release 16/xmol Ca2+/l cells, whereas Ins(1,4,5)P3 can mobilize 55/xmol Ca2+/l cells. The results suggest that cADP-ribose and Ins(1,4,5)P3 release Ca 2+ from distinct internal stores and that a third Ca 2+ pool exists which can selectively interact with the Ins(1,4,5)P3-sensitive Ca z+ store by a GTP-mediated process.

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supporting

confidence: 79%

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca²⁺ from distinct intracellular pools in permeabilized lacrimal acinar cells

1995

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“…Previous studies by our group and others using GTP or nonhydrolyzable GTP analogs such as GTP␥S have suggested a potential role for GTPases in the fusion of mammalian ER membranes (12,15,16). To define the GTP requirement for ER assembly, we first examined whether the GTP-dependent step required a membrane-associated or cytosolic component.…”

Section: Resultsmentioning

confidence: 99%

“…Previous observations using GTP and/or GTP analogs have implicated the involvement of a GTPase(s) in the homotypic assembly of the mammalian ER membranes (12,15,16). We eliminated the possibility that Sar1, ARF1, and Rab1 are involved in ER fusion as trans-dominant inhibitory forms of these proteins, which inhibit ER to Glogi transport, had no effect on ER fusion in vitro.…”

Section: Fig 2 Er Fusion Is Mediated By a Rab Gtpasementioning

confidence: 95%

“…To study homotypic fusion, cell-free assays have been developed that measure the fusion of endosomes (5), mitotic Golgi fragments (6,7), yeast vacuoles (8 -10), and ER 1 microsomes (11)(12)(13)(14)(15)(16). In yeast, homotypic fusion of ER microsomes has been suggested to require the luminal molecular chaperone KAR2 (the yeast homolog of mammalian BiP) (11) and Cdc48p (17), the latter being a member of a larger gene family of N-ethylmaleimide (NEM)-sensitive AAA ATPases, which includes the intra-Golgi targeting/fusion factor NSF (reviewed in Refs.…”

Section: From the Departments Of Cell And Molecular Biology The Scrimentioning

confidence: 99%

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A Rab GTPase Is Required for Homotypic Assembly of the Endoplasmic Reticulum

Turner

Plutner

Balch

1997

Journal of Biological Chemistry

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To define the requirements for the homotypic fusion of mammalian endoplasmic reticulum (ER) membranes, we have developed a quantitative in vitro enzyme-linked immunosorbent assay. This assay measures the formation of IgG (H 2 L 2 ) following the fusion of ER microsomes containing either the heavy or light chain subunits. Guanine nucleotide dissociation inhibitor (GDI), a protein that extracts Rab GTPases in the GDP-bound form from membranes, potently inhibits fusion. Inhibition was not observed using GDI mutants defective in Rab binding. Kinetic analysis of the inhibitory effects of GDI revealed that Rab activation is required immediately preceding or coincident with fusion and that this step is preceded by a priming event requiring a member of the AAA ATPase family. Our results suggest that homotypic fusion of ER membranes requires Rab and that Rab activation is a transient event necessary for the formation of a fusion pore leading to the mixing of luminal contents of ER microsomes.Regulated fusion is a critical feature of heterotypic membrane interactions involved in vesicular transport of cargo through the exocytic and endocytic pathways (reviewed in Ref.

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“…The exact nature of the InsP,-sensitive organelle($ is not known. There is evidence for InsP3insensitive as well as -sensitive stores with different loading characteristics (Thevenod et al, 1989;Missiaen et al, 1991a1, which may become dynamically interconnected by GTP-dependent interactions (Dawson and Comerford, 1989;Gill et al, 1989). Another unique property of the InsP,-sensitive Ca2+ store is the phenomenon of "quantal" Ca2+ release.…”

mentioning

confidence: 99%

Ca²⁺ dependence of inositol 1,4,5‐trisphosphate‐induced Ca²⁺ release in renal epithelial LLC‐PK₁ cells

Tshipamba

Smedt

Missiaen

et al. 1993

Journal Cellular Physiology

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We have studied arginine vasopressin (AVP)-, thapsigargin- and inositol 1,4,5-trisphosphate (InsP3)-mediated Ca2+ release in renal epithelial LLC-PK1 cells. AVP-induced changes in the intracellular free calcium concentration ([Ca2+]i) were studied in indo-1 loaded single cells by confocal laser cytometry. AVP-mediated Ca2+ mobilization was also observed in the absence of extracellular Ca2+, but was completely abolished after depletion of the intracellular Ca2+ stores by 2 microM thapsigargin. Using 45Ca2+ fluxes in saponin-permeabilized cell monolayers, we have analysed how InsP3 affected the Ca2+ content of non-mitochondrial Ca2+ pools in different loading and release conditions. Less than 10% of the Ca2+ was taken up in a thapsigargin-insensitive pool when loading was performed in a medium containing 0.1 microM Ca2+. The thapsigargin-insensitive compartment amounted to 35% in the presence of 110 microM Ca2+, but Ca2+ sequestered in this pool could not be released by InsP3. The thapsigargin-sensitive Ca2+ pool, in contrast, was nearly completely InsP3 sensitive. A submaximal [InsP3], however, released only a fraction of the sequestered Ca2+. This fraction was dependent on the cytosolic as well as on the luminal [Ca2+]. The cytosolic free [Ca2+] affected the InsP3-induced Ca2+ release in a biphasic way. Maximal sensitivity toward InsP3 was found at a free cytosolic [Ca2+] between 0.1 and 0.5 microM, whereas higher cytosolic [Ca2+] decreased the InsP3 sensitivity. Other divalent cations or La3+ did not provoke similar inhibitory effects on InsP3-induced Ca2+ release. The luminal free [Ca2+] was manipulated by varying the time of incubation of Ca(2+)-loaded cells in an EGTA-containing medium. Reduction of the Ca2+ content to one-third of its initial value resulted in a fivefold decrease in the InsP3 sensitivity of the Ca2+ release.

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Effects of GTP on Ca2+ movements across endoplasmic reticulum membranes

Cited by 43 publications

References 45 publications

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca²⁺ from distinct intracellular pools in permeabilized lacrimal acinar cells

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca²⁺ from distinct intracellular pools in permeabilized lacrimal acinar cells

A Rab GTPase Is Required for Homotypic Assembly of the Endoplasmic Reticulum

Ca²⁺ dependence of inositol 1,4,5‐trisphosphate‐induced Ca²⁺ release in renal epithelial LLC‐PK₁ cells

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Effects of GTP on Ca2+ movements across endoplasmic reticulum membranes

Cited by 43 publications

References 45 publications

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca2+ from distinct intracellular pools in permeabilized lacrimal acinar cells

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca2+ from distinct intracellular pools in permeabilized lacrimal acinar cells

A Rab GTPase Is Required for Homotypic Assembly of the Endoplasmic Reticulum

Ca2+ dependence of inositol 1,4,5‐trisphosphate‐induced Ca2+ release in renal epithelial LLC‐PK1 cells

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Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca²⁺ from distinct intracellular pools in permeabilized lacrimal acinar cells

Cyclic ADP‐ribose and inositol 1,4,5‐trisphosphate mobilizes Ca²⁺ from distinct intracellular pools in permeabilized lacrimal acinar cells

Ca²⁺ dependence of inositol 1,4,5‐trisphosphate‐induced Ca²⁺ release in renal epithelial LLC‐PK₁ cells