Presence of Zinc and Calcium Permeant Channels in the Inner Membrane of the Nuclear Envelope

Longin, Anne-Sophie; Mézin, P.; Favier, Alain; Verdetti, Jean

doi:10.1006/bbrc.1997.6752

Cited by 22 publications

(10 citation statements)

References 26 publications

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“…It also indicates that the nuclear reticulum is a site for Ca 2+ deposition. Calcium channels have recently been identified in isolated patches of the inner nuclear envelope (Longin et al 1997). Since calcium has been implicated in the control of secretion (Read et al 1992), the impregnation with zinc osmate is an indication that the nuclear reticulum might function in controlling secretion from these placental cells in L. regale.…”

Section: Discussionmentioning

confidence: 99%

The nuclear reticulum in placental cells ofLilium regale is a part of the endomembrane system

1998

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Summary. Placental cells line the ovarian transmitting tract in Lili-um regale and produce exudates for secretion. Sections through the highly lobed nuclei of these cells reveal the presence of membrane profiles which form vesicles with varying dimensions in cross section. Computer reconstruction of the nucleus reveals that the vesicle profiles form a complex reticulum of tubular cisternae, which spans the whole nucleus, enclosing a maze of continuous lumen space. Connections between the vesicles and the inner nuclear envelope are visible at various points along the nuclear envelope. This complex network of tubules which constitutes the reticulum arises from the inner nuclear membrane. The nuclear reticulum dramatically increases the inner-envelope surface area, comprising 82% of the total membrane perimeter of inner nuclear envelope and nuclear reticulum. The inner nuclear envelope invaginates into the nucleus forming the nuclear reticulum and the outer nuclear envelope evaginates into the endoplasmic reticulum (ER), indicating that there is a continuity between the lumens of the nuclear reticulum and the ER. The nuclear reticulum is labelled with zinc iodide-osmium tetroxide, a staining pattern identical to that seen in the ER. Positive reaction to the zinc iodide-osmium tetroxide indicates that the nuclear reticulum is a site for Ca 2+ deposition. The nuclear reticulum forms an extension of the endomembrane system which reaches deep into the nucleoplasm. The lumenal continuity of this system means that there is a channel for communication from the cytoplasm into the nucleoplasm, and that this channel sequesters calcium.Keywords: Endomembrane system; Lilium regale; Nucleus; Placental cell; Transfer cell; Transmitting tissue.Abbreviations: ER endoplasmic reticulum; TEM transmission electron microscope; ZIO zinc iodide-osmium tetroxide.

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Section: Discussionmentioning

confidence: 99%

The nuclear reticulum in placental cells ofLilium regale is a part of the endomembrane system

1998

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“…A variety of ER͞SR and nuclear channels that may contribute to regulate [Ca 2ϩ ] n and other ion species have been reported (13,32,(39)(40)(41)(42)(43)(44). An important feature is that several ER͞SR and nuclear channels are voltage-sensitive.…”

Section: Blockade Of Nkatp Channels Elicits Ca 2؉ Signals In Isolatedmentioning

confidence: 99%

Nuclear K _ATP channels trigger nuclear Ca ²⁺ transients that modulate nuclear function

Quesada

Rovira

Martı́n

et al. 2002

Proc. Natl. Acad. Sci. U.S.A.

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Glucose, the principal regulator of endocrine pancreas, has several effects on pancreatic beta cells, including the regulation of insulin release, cell proliferation, apoptosis, differentiation, and gene expression. Although the sequence of events linking glycemia with insulin release is well described, the mechanism whereby glucose regulates nuclear function is still largely unknown. Here, we have shown that an ATP-sensitive K ؉ channel (KATP) with similar properties to that found on the plasma membrane is also present on the nuclear envelope of pancreatic beta cells. In isolated nuclei, blockade of the KATP channel with tolbutamide or diadenosine polyphosphates triggers nuclear Ca 2؉ transients and induces phosphorylation of the transcription factor cAMP response element binding protein. In whole cells, fluorescence in situ hybridization revealed that these Ca 2؉ signals may trigger c-myc expression. These results demonstrate a functional KATP channel in nuclei linking glucose metabolism, nuclear Ca 2؉ signals, and nuclear function. Pancreatic beta cells play a critical role in maintaining a steady-state level of glucose in the blood and tissues. Increased levels of glucose stimulate beta cells to secrete insulin closing a well established feedback loop. Malfunction of beta cells causes the widespread pathology, diabetes mellitus. The signal transduction mechanism leading to insulin release involves the closure of plasma membrane K ATP channels as a result of glucose metabolism by increasing both the intracellular ATP͞ ADP ratio and diadenosine polyphosphates (DPs; refs. 1 and 2). Channel closure leads to membrane depolarization and the opening of voltage-activated Ca 2ϩ channels (3). The subsequent cytosolic Ca 2ϩ signal, which is oscillatory (4), triggers a pulsatile insulin secretion. In most cells, a single second messenger as Ca 2ϩ is able to provoke different responses depending on its route of entry, its localization, and a code of amplitude or frequency of Ca 2ϩ oscillations (4, 5). In pancreatic beta cells, Ca 2ϩ mediates not only insulin secretion but also a broad range of other processes such as gene expression (6, 7). Although it is well established that the nucleoplasmic concentration of free Ca 2ϩ regulates nuclear function (5), the mechanism whereby nuclear Ca 2ϩ signals are generated is still unclear. Here, we report confocal measurements of nuclear Ca 2ϩ concentration ([Ca 2ϩ ] n ) in intact beta cells exposed to glucose. Experiments in isolated nuclei revealed a K ATP channel present on the nuclear envelope whose blockade results in a [Ca 2ϩ ] n rise. This increased [Ca 2ϩ ] n induces phosphorylation of the transcription factor cAMP response element binding protein (CREB). We further demonstrate that [Ca 2ϩ ] n elevation may result in c-myc expression in whole cells. Materials and MethodsCell Isolation, Culture, and Permeabilization. Islets from adult (8-10 weeks old) Swiss albino male mice (OF1) killed by cervical dislocation were isolated and then dispersed into single cells after a publ...

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“…Most reports refer to channels in the ONM, while, to our knowledge, only few channels have been reported to date at INM. Marchenko et al [21] describe the inositol 1,4,5-trisphosphate (InsP 3 ) receptor, Longin et al [22] a zinc and a calcium channel, Rousseau et al [23] report two chloride conductances and a non-selective cation channel, and Fedorenko et al, describe a large conductance non-selective cation channel in both the ONM and the INM [24]; among all of them, only the InsP 3 receptor has an identified molecular identity.…”

Section: Introductionmentioning

confidence: 99%

Functional KV10.1 Channels Localize to the Inner Nuclear Membrane

et al. 2011

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Ectopically expressed human KV10.1 channels are relevant players in tumor biology. However, their function as ion channels at the plasma membrane does not totally explain their crucial role in tumors. Both in native and heterologous systems, it has been observed that a majority of KV10.1 channels remain at intracellular locations. In this study we investigated the localization and possible roles of perinuclear KV10.1. We show that KV10.1 is expressed at the inner nuclear membrane in both human and rat models; it co-purifies with established inner nuclear membrane markers, shows resistance to detergent extraction and restricted mobility, all of them typical features of proteins at the inner nuclear membrane. KV10.1 channels at the inner nuclear membrane are not all transported directly from the ER but rather have been exposed to the extracellular milieu. Patch clamp experiments on nuclei devoid of external nuclear membrane reveal the existence of channel activity compatible with KV10.1. We hypothesize that KV10.1 channels at the nuclear envelope might participate in the homeostasis of nuclear K+, or indirectly interact with heterochromatin, both factors known to affect gene expression.

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Presence of Zinc and Calcium Permeant Channels in the Inner Membrane of the Nuclear Envelope

Cited by 22 publications

References 26 publications

The nuclear reticulum in placental cells ofLilium regale is a part of the endomembrane system

The nuclear reticulum in placental cells ofLilium regale is a part of the endomembrane system

Nuclear K _ATP channels trigger nuclear Ca ²⁺ transients that modulate nuclear function

Functional KV10.1 Channels Localize to the Inner Nuclear Membrane

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Presence of Zinc and Calcium Permeant Channels in the Inner Membrane of the Nuclear Envelope

Cited by 22 publications

References 26 publications

The nuclear reticulum in placental cells ofLilium regale is a part of the endomembrane system

The nuclear reticulum in placental cells ofLilium regale is a part of the endomembrane system

Nuclear K ATP channels trigger nuclear Ca 2+ transients that modulate nuclear function

Functional KV10.1 Channels Localize to the Inner Nuclear Membrane

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Nuclear K _ATP channels trigger nuclear Ca ²⁺ transients that modulate nuclear function