A serum factor that activates the phosphatidylinositol phosphate signaling system in Xenopus oocytes.

Tigyi, Gábor; Dyer, David L.; Matute, Carlos; Miledi, Ricardo

doi:10.1073/pnas.87.4.1521

Cited by 80 publications

(63 citation statements)

References 32 publications

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“…Considering different species, possible variations among different charges etc, the IK(ACb)- data from one representative cell activating principle in serum seems to be entirely associated with albumin. This observation, and the finding that delipidation of albumin removes the IK(Acb)-activating principle, point to analogous findings with Xenopus oocytes, where a serum-component triggers an inositol 1,4,5-trisphosphate (InsP 3) response, normally controlled by a muscarinic receptor [26], and with pe12 cells, in which Ca 2 + signals and growth responses can be evoked by a serum factor [7,8]. These authors managed to identify the active principle as lyosphosphatidic acids (LPA) that are frrmly bound to albumin [25,27], see also [6].…”

Section: Resultssupporting

confidence: 65%

Membrane-delimited activation of muscarinic K current by an albumin-associated factor in guinea-pig atrial myocytes

Bünemann

Pott

1993

Pfl�gers Arch

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Abstract. Atrial myocytes obtained by enzymatic perfusion of hearts from adult guinea,-pigs and cultured for 0-14 days were studied using different configurations of the patch-clamp technique. Activation of muscarinic K current [IK(Ach)l in whole-cell voltage-clamp mode by strongly diluted sera from various sources could be mimicked by corresponding concentrations of albumin, but not by delipidated ("fatty-acid-free") samples of albumin. In cell-attached membrane patches activity of IK(ACb) channels was significantly higher than basal IK1.ACb) channel activity, if the pipette contained serum, whereas application of serum-containing solution to the cell outside the patch did not affect channel activity. In isolated inside-out membrane patches, strong IK(ACh) activation by internal guanosine triphosphate (GTP, 5 IlM) was observed if the pipette contained serum. If no activator was presented to the outer face of the membrane, only weak opening activity was observed during bath application of GTP. These results demonstrate that the serum factor which causes activation of IK(ACb) is associated with albumin. Furthennore activation of IK(ACh) by that factor proceeds analogous to ACh or adenosine, i. e. via a membrane-delimited receptor, G-protein, channel interaction.

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Section: Resultssupporting

confidence: 65%

Membrane-delimited activation of muscarinic K current by an albumin-associated factor in guinea-pig atrial myocytes

Bünemann

Pott

1993

Pfl�gers Arch

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“…5). Indeed, this current has been a useful tool for monitoring and amplifying the intracellular Ca 2ϩ at the subplasmalemmal region of the oocyte because plasma membrane of these cells contains numerous Ca 2ϩ -activated chloride channels (26,29,40,53). We found that the serum-elicited I Cl(Ca) in uninjected oocytes was dramatically increased by KB-R7943 in a concentration dependent and reversible manner.…”

Section: Discussionmentioning

confidence: 99%

“…Because follicular cells and the oocyte are closely coupled by gap junction channels, which allow free ionic communication between both cell types, the possibility exists that blocking NCX in follicular cells with KB-R7943 might be responsible for the increasing response to serum. However, there are several arguments that rule out this possibility: 1) the response to serum is obtained only in defolliculated oocytes (26), 2) RT-PCRs performed on defolliculated oocytes and on follicular cells (Fig. 1) amplified different NCX isoforms, and 3) immunolabeling of NCX1 by a specific antibody is clearly distinguishable in follicle-enclosed oocytes and in denuded oocytes (Fig.…”

Section: Native Na ϩ /Ca 2ϩ Exchanger In Xenopus Oocytesmentioning

confidence: 99%

“…5A). The serum-induced currents were caused by movement of Cl Ϫ ions through Ca 2ϩ -activated chloride channels endogenously expressed in the oocyte (26). These channels are opened by Ca 2ϩ released from the InsP 3 -sensitive internal stores when a serum factor activates specific membrane receptors coupled to the phosphatidylinositol phosphate signaling pathway.…”

Section: Fig 1 Rt-pcr Amplification and Sequencing Of The Ncx Isofomentioning

confidence: 99%

“…Therefore, it can be inferred that if oocytes possess an active plasmalemmal NCX mechanism, the stimuli that promote Ca 2ϩ mobilization from InsP 3 -sensitive internal stores and the consequent [Ca 2ϩ ] i rise at the inner oocyte surface membrane in the vicinity of the exchanger would activate Ca 2ϩ extrusion via NCX. If this hypothesis is true, rabbit serum, which mobilizes intracellular Ca 2ϩ by activating the phosphatidylinositol phosphate signaling pathway in these cells (26), would be an excellent candidate to explore the "Ca 2ϩ efflux" mode activity of a putative NCX endogenously expressed by the oocytes.…”

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confidence: 99%

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Cross-talk between Native Plasmalemmal Na+/Ca2+ Exchanger and Inositol 1,4,5-Trisphosphate-sensitive Ca2+ Internal Store in Xenopus Oocytes

Solís-Garrido

Pintado

Andrés-Mateos

et al. 2004

Journal of Biological Chemistry

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Because the presence of a native plasmalemmal Na ؉ / Ca 2؉ exchange (NCX) activity in Xenopus laevis oocytes remains controversial, its possible functional role in these cells is poorly understood. Here, in experiments on control oocytes and oocytes overexpressing a cloned NCX1 cardiac protein, confocal microscopy combined with electrophysiological techniques reveal that these cells express an endogenous NCX protein forming a functional microdomain with inositol 1,4,5-trisphosphate receptors (InsP 3 R) that controls intracellular Ca 2؉ in a restricted subplasmalemmal space. The following data obtained in control denuded oocytes are consistent with this view: (i) reverse transcription-PCR revealed that the oocyte expresses two transcripts for the NCX1 and NCX3 isoforms; (ii) immunofluorescence experiments showed that native NCX1 and InsP 3 Rs are largely codistributed in discrete areas of the plasma membrane in close apposition to the cortical endoplasmic reticulum shell; (iii) when stimulated by rabbit serum, which elevates intracellular Ca 2؉ mediated by InsP 3 , voltage-clamped oocytes display a large and transient inward Ca 2؉ -activated chloride current, I Cl(Ca) , as a result of the Ca 2؉ rise at the inner surface membrane; (iv) this current is significantly enhanced by KB-R7943 and by an extracellular sodium-depleted medium, two maneuvers that prevent "Ca 2؉ extrusion" via NCX; and (v) blocking NCX enhanced the I Cl(Ca) elicited by InsP 3 but not by Ca 2؉ photolysis in oocytes injected with the respective caged compounds. Moreover, overexpression of cardiac NCX1, confirmed by confocal microscopy, has functional consequences for the "Ca 2؉ influx" but not for the serum-elicited "Ca 2؉ efflux" mode of basal exchange activity and does not alter the number of endogenous NCX/InsP 3 Rs colocalization sites. Our results suggest that native NCX, because of its strategic position, may regulate InsP 3 -mediated Ca 2؉ signaling during the early phases of oocyte maturation and/or fertilization, and furthermore foreign cardiac protein is excluded from the Ca 2؉ microdomains surrounding the native NCX/InsP 3 Rs complex in the oocyte.

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Effects of serum on calcium mobilization in the submandibular cell line A253

et al. 1999

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The effects of serum on inositol 1,4,5-trisphosphate (IP3) formation and Ca2+ mobilization in the human submandibular cell line A253 were studied. Exposure of A253 cells to fetal bovine serum (FBS) elicited a 3.3-fold increase in IP3 formation and a concentration-dependent transient increase in cytosolic free Ca2+ concentration ([Ca2+]i), which was similar in Ca2+-containing and Ca2+-free media. Newborn bovine serum (NBS), but not bovine serum albumin (BSA), induced a similar response. The Ca2+ release triggered by FBS was significantly (88%) reduced by the phospholipase C inhibitor U73122, indicating that Ca2+ release induced by FBS is through the PLC pathway. Pretreatment with the tyrosine kinase inhibitor genistein abolished the FBS- and NBS-induced Ca2+ release, suggesting that tyrosine kinase plays an important role in mediating the Ca2+ release. Pre-exposure to ATP or thapsigargin (TG) significantly reduced the FBS-induced [Ca2+]i increase, indicating that Ca2+ release caused by FBS is from the TG- or ATP-sensitive Ca2+ store. While FBS exposure elicited a large Ca2+ release, it reduced Ca2+ influx. Furthermore, FBS significantly inhibited the Ca2+ influx activated by the depletion of intracellular stores by ATP or TG. These results suggest that (1) serum elicits Ca2+ release from ATP- and TG-sensitive stores, which is mediated by IP3; (2) the serum-induced Ca2+ release may be modulated by a tyrosine kinase-associated process; and (3) serum strongly inhibits Ca2+ influxes including the store depletion-activated Ca2+ influx.

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A serum factor that activates the phosphatidylinositol phosphate signaling system in Xenopus oocytes.

Cited by 80 publications

References 32 publications

Membrane-delimited activation of muscarinic K current by an albumin-associated factor in guinea-pig atrial myocytes

Membrane-delimited activation of muscarinic K current by an albumin-associated factor in guinea-pig atrial myocytes

Cross-talk between Native Plasmalemmal Na+/Ca2+ Exchanger and Inositol 1,4,5-Trisphosphate-sensitive Ca2+ Internal Store in Xenopus Oocytes

Effects of serum on calcium mobilization in the submandibular cell line A253

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