Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells

The nuclear pore complex (NPC) mediates communication between the cytoplasm and nucleus in eukaryotic cells. Active transport of large polypeptides as well as passive diffusion of smaller (≈10 kD) macromolecules through the NPC can be inhibited by depletion of intracellular Ca2+ stores. However, the...

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Main Authors:	Strübing, Carsten, Clapham, David E.
Format:	Online
Language:	English
Published:	The Rockefeller University Press 1999
Online Access:	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2223372/

id	pubmed-2223372
recordtype	oai_dc
spelling	pubmed-22233722008-04-21 Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells Strübing, Carsten Clapham, David E. Article The nuclear pore complex (NPC) mediates communication between the cytoplasm and nucleus in eukaryotic cells. Active transport of large polypeptides as well as passive diffusion of smaller (≈10 kD) macromolecules through the NPC can be inhibited by depletion of intracellular Ca2+ stores. However, the physiological relevance of this process for the regulation of nucleocytoplasmic trafficking is not yet clear. We expressed green fluorescent protein (GFP)–tagged glucocorticoid receptor (GR) and mitogen-activated protein (MAP) kinase–activated protein kinase 2 (MK2) to study the effect of Ca2+ store depletion on active transport in HM1 cells, a human embryonic kidney cell line stably transfected with the muscarinic M1 receptor. Dexamethasone-induced nuclear import of GR-GFP and anisomycin-induced nuclear export of GFP-MK2 was monitored by confocal microscopy. We found that store depletion by carbachol, thapsigargin or ionomycin had no effect on GR-GFP import, whereas pretreatment with 1,2-bis-(o-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid–acetoxymethyl ester (BAPTA-AM) attenuated import significantly. Export of GFP-MK2 was not influenced by any pretreatment. Moreover, carbachol stimulated GFP-MK2 translocation to the cytoplasm in the absence of anisomycin. These results demonstrate that Ca2+ store depletion in intact HM1 cells is not directly linked to the inhibition of active protein transport through the NPC. The inhibition of GR-GFP import but not GFP-MK2 export by BAPTA-AM presumably involves a depletion-independent mechanism that interferes with components of the nuclear import pathway. The Rockefeller University Press 1999-02-01 /pmc/articles/PMC2223372/ /pubmed/9925822 Text en This article is distributed under the terms of an Attribution–Noncommercial–Share Alike–No Mirror Sites license for the first six months after the publication date (see http://www.rupress.org/terms). After six months it is available under a Creative Commons License (Attribution–Noncommercial–Share Alike 4.0 Unported license, as described at http://creativecommons.org/licenses/by-nc-sa/4.0/).
repository_type	Open Access Journal
institution_category	Foreign Institution
institution	US National Center for Biotechnology Information
building	NCBI PubMed
collection	Online Access
language	English
format	Online
author	Strübing, Carsten Clapham, David E.
spellingShingle	Strübing, Carsten Clapham, David E. Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells
author_facet	Strübing, Carsten Clapham, David E.
author_sort	Strübing, Carsten
title	Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells
title_short	Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells
title_full	Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells
title_fullStr	Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells
title_full_unstemmed	Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells
title_sort	active nuclear import and export is independent of lumenal ca2+ stores in intact mammalian cells
description	The nuclear pore complex (NPC) mediates communication between the cytoplasm and nucleus in eukaryotic cells. Active transport of large polypeptides as well as passive diffusion of smaller (≈10 kD) macromolecules through the NPC can be inhibited by depletion of intracellular Ca2+ stores. However, the physiological relevance of this process for the regulation of nucleocytoplasmic trafficking is not yet clear. We expressed green fluorescent protein (GFP)–tagged glucocorticoid receptor (GR) and mitogen-activated protein (MAP) kinase–activated protein kinase 2 (MK2) to study the effect of Ca2+ store depletion on active transport in HM1 cells, a human embryonic kidney cell line stably transfected with the muscarinic M1 receptor. Dexamethasone-induced nuclear import of GR-GFP and anisomycin-induced nuclear export of GFP-MK2 was monitored by confocal microscopy. We found that store depletion by carbachol, thapsigargin or ionomycin had no effect on GR-GFP import, whereas pretreatment with 1,2-bis-(o-aminophenoxy) ethane-N,N,N′,N′-tetraacetic acid–acetoxymethyl ester (BAPTA-AM) attenuated import significantly. Export of GFP-MK2 was not influenced by any pretreatment. Moreover, carbachol stimulated GFP-MK2 translocation to the cytoplasm in the absence of anisomycin. These results demonstrate that Ca2+ store depletion in intact HM1 cells is not directly linked to the inhibition of active protein transport through the NPC. The inhibition of GR-GFP import but not GFP-MK2 export by BAPTA-AM presumably involves a depletion-independent mechanism that interferes with components of the nuclear import pathway.
publisher	The Rockefeller University Press
publishDate	1999
url	https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2223372/
_version_	1611436050531483648

Active Nuclear Import and Export Is Independent of Lumenal Ca2+ Stores in Intact Mammalian Cells

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