The effects of free [Ca2+] on the cytosolic face of the inositol (1,4,5)-trisphosphate receptor at the single channel level

Thrower, C. Edwin; Lea, J. A. Edward; Dawson, P. Alan

doi:10.1042/bj3300559

Cited by 27 publications

(23 citation statements)

References 26 publications

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“…This would account for the common properties in the mechanisms of Ca# + inhibition of Ca# + flux and InsP $ binding. It is also consistent with the observation by Thrower et al [44] of Ca# + flux inhibiton at high InsP $ concentration, because the free Ca# + concentrations used in this study were high enough to convert the InsP $ R into this state. The negative interaction between InsP $ and Ca# + described here might be specific to InsP $ R1.…”

Section: [$H]inspsupporting

confidence: 93%

“…Two of the Ca# + -binding regions identified in the cytoplasmic part of InsP $ R1 are located in the InsP $ -binding domain [25], making these sites reasonable candidates for the mediation of the competitive inhibitory effects of Ca# + described here. Recently, biphasic dependence on Ca# + of InsP $ R channel activity was found to occur with cerebellar receptor isolated and reconstituted in lipid bilayers, suggesting direct effects of Ca# + on this protein [44]. However, accessory factors might also be involved in the regulation of these Ca# + effects.…”

Section: [$H]inspmentioning

confidence: 99%

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Regulation of cerebellar Ins(1,4,5)P3 receptor by interaction between Ins(1,4,5)P3 and Ca2+

Coquil

Picard

Mauger

1999

Biochemical Journal

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We have characterized in detail the Ca# + -dependent inhibition of [$H]Ins(1,4,5)P $ ([$H]InsP $ ) binding to sheep cerebellar microsomes, over a short duration (3 s), with the use of a perfusion protocol. This procedure prevented artifacts previously identified in studies of this Ca# + effect. In a cytosol-like medium at pH 7.1 and 20 mC, a maximal inhibition of approx. 50 % was measured. Both inhibition and its reversal were complete within 3 s. Ca# + decreased the affinity of the receptor for InsP $ by approx. 50 % (K d 146p24 nM at pCa 9 and 321p56 nM at pCa 5.3), without changing the total number of binding sites. Conversely, increasing the [$H]InsP $ concentration from 30 to 400 nM tripled the IC &! for Ca# + and decreased the maximal inhibition by 63 %. This is similar to a partial competitive inhibition between InsP $ binding and inhibitory Ca# + binding and is consistent with InsP $ and

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Section: [$H]inspsupporting

confidence: 93%

Section: [$H]inspmentioning

confidence: 99%

Regulation of cerebellar Ins(1,4,5)P3 receptor by interaction between Ins(1,4,5)P3 and Ca2+

Coquil

Picard

Mauger

1999

Biochemical Journal

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“…5b, expanded section). This lack of inhibition by free Ca 2ϩ has been observed previously for purified receptor (28,29) and contrasts to the inhibition seen with microsomes (30). Repetition of this experiment, with the addition of CGA to the trans compartment, produced dramatic increases in channel activity (Fig.…”

Section: Effect Of Cga On Ca 2ϩ Dependence For Insp 3 R-thementioning

confidence: 51%

Activation of the Inositol 1,4,5-Trisphosphate Receptor by the Calcium Storage Protein Chromogranin A

Thrower

Park

et al. 2002

Journal of Biological Chemistry

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CGA1 is a member of the granin protein family and is stored in high concentrations in the large dense core secretory granules of most endocrine and neuroendocrine cells as well as in many nerve cells in the periphery and brain (1, 2). CGA, the first member of the granin family to be discovered (3-5), has a wide variety of functions, both extracellular and intracellular.As one of its extracellular functions, CGA acts as a prohormone, a protein that contains numerous sites for proteolytic processing. Following secretion, extracellular proteases cleave CGA, generating several peptide fragments with biological activity, including pancreastatin (6, 7), vasostatins I and II (8 -10), parastatin (11), catestatin (12), and chromacin (13). In healthy individuals, CGA and its peptide fragments are present in the circulatory system in low nanomolar quantities. However, in patients suffering from pheochromocytoma and other neuroendocrine tumors, concentrations are significantly higher (14). Elevated plasma levels of CGA are associated with a number of pathological conditions making the protein an ideal marker not only for neuroendocrine tumors but also for chronic heart failure and brain disorders such as Parkinson's and Alzheimer's diseases (15).Among its intracellular roles, CGA has been shown to interact with ATP, catecholamines, and Ca 2ϩ (16,17), to acidify the intravesicular medium and to sort proteins for the regulated secretory pathway via a range of protein-protein interactions (15). These sorting functions include aggregation with chromogranin B, complexing with dopamine ␤-hydroxylase, t-plasminogen activator, and binding secretory granule membrane constituents such as the InsP 3 R (15).In recent years, secretory granules of neuroendocrine cells have been identified as inositol (1,4,5)-trisphosphate (InsP 3 )-sensitive Ca 2ϩ stores (18 -20). In the granules CGA forms a tetramer and appears to bind four molecules of the intraluminal loop of the InsP 3 R at the intravesicular pH 5.5 (21-23). In vitro studies show that purified InsP 3 R interact directly with CGA at this pH and dissociate from it at pH 7.5, a pH encountered when exocytosis occurs (24). Co-transfection of InsP 3 R and CGA into COS-7 cells followed by co-immunoprecipitation demonstrates that these two proteins form a complex in vivo (24).We have investigated the functional aspect of this coupling via InsP 3 -mediated Ca 2ϩ release studies using InsP 3 R-reconstituted liposomes in the presence and absence of CGA. We have further characterized the molecular basis of this phenomenon at the single channel level using planar lipid bilayer studies. In the presence of CGA the open probability and mean open time of the InsP 3 R channel increases significantly. Hence, modulation of InsP 3 R channel activity by CGA appears to be an essential component in the control of intracellular Ca 2ϩ concentration in secretory granules. MATERIALS AND METHODS Purification of the InsP 3 ReceptorFor Flux Studies-The type I InsP 3 receptor was isolated from bovine cerebella as d...

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“…In each case, the single-channel open probability (P o ) of IP 3 -activated channels displayed a bell-shaped dependence on cytosolic Ca 2þ concentration. Evidence that purified IP 3 R1 could be stimulated, but not inhibited, by cytosolic Ca 2þ (Thrower et al 1998;Michikawa et al 1999) raised the possibility that Ca 2þ inhibition might be mediated by an accessory protein, although it has yet to be identified. The same explanation perhaps accounts for some reports, often derived from bilayer recordings, in which Ca 2þ was suggested not to inhibit IP 3 R2 or IP 3 R3 (Horne and Meyer 1995;Hagar et al 1998;Miyakawa et al 1999;Ramos-Franco et al 2000).…”

Section: Regulation Of Ip 3 Receptors By Ca 2þ and Ipmentioning

confidence: 99%

IP3 Receptors: Toward Understanding Their Activation

Taylor¹,

Tovey²

2010

Cold Spring Harbor Perspectives in Biology

260

190

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Inositol 1,4,5-trisphosphate receptors (IP 3 R) and their relatives, ryanodine receptors, are the channels that most often mediate Ca 2þ release from intracellular stores. Their regulation by Ca 2þ allows them also to propagate cytosolic Ca 2þ signals regeneratively. This brief review addresses the structural basis of IP 3 R activation by IP 3 and Ca 2þ . IP 3 initiates IP 3 R activation by promoting Ca 2þ binding to a stimulatory Ca 2þ -binding site, the identity of which is unresolved. We suggest that interactions of critical phosphate groups in IP 3 with opposite sides of the clam-like IP 3 -binding core cause it to close and propagate a conformational change toward the pore via the adjacent N-terminal suppressor domain. The pore, assembled from the last pair of transmembrane domains and the intervening pore loop from each of the four IP 3 R subunits, forms a structure in which a luminal selectivity filter and a gate at the cytosolic end of the pore control cation fluxes through the IP 3 R.

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The effects of free [Ca2+] on the cytosolic face of the inositol (1,4,5)-trisphosphate receptor at the single channel level

Cited by 27 publications

References 26 publications

Regulation of cerebellar Ins(1,4,5)P3 receptor by interaction between Ins(1,4,5)P3 and Ca2+

Regulation of cerebellar Ins(1,4,5)P3 receptor by interaction between Ins(1,4,5)P3 and Ca2+

Activation of the Inositol 1,4,5-Trisphosphate Receptor by the Calcium Storage Protein Chromogranin A

IP3 Receptors: Toward Understanding Their Activation

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