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Results for “Nuclear Envelope”

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PubMed1984

Analysis of pore-rich areas on the nuclear envelope of spermatocytes.

Serial sections analysis of spermatocytes of the rodent Phyllotis darwini, reveal a persistent positional relationship between nucleolar material and centrioles. Pore rich areas interposed between these nucleocytoplasmic components, are represented graphically. Centriole replication takes place during the pachytene stage. Pore rich areas could be the result of a preferential aggregational process which insures the exchange of information between nuclear and cytoplasmic regions.

Animals↗
PubMed2004

Drosophila klarsicht has distinct subcellular localization domains for nuclear envelope and microtubule localization in the eye.

The Drosophila klarsicht (klar) gene is required for developmentally regulated migrations of photoreceptor cell nuclei in the eye. klar encodes a large ( approximately 250 kD) protein with only one recognizable amino acid sequence motif, a KASH (Klar, Anc-1, Syne-1 homology) domain, at its C terminus. It has been proposed that Klar facilitates nuclear migration by linking the nucleus to the microtubule organizing center (MTOC). Here we perform genetic and immunohistochemical experiments that provide a critical test of this model. We analyze mutants in the endogenous klar gene and also flies that express deleted forms of Klar protein from transgenes. We find that the KASH domain of Klar is critical for perinuclear localization and for function. In addition, we find that the N-terminal portion of Klar is also important for function and contains a domain that localizes the protein to microtubules apical to the nucleus. These results provide strong support for a model in which Klar links the nucleus to the MTOC.

Amino Acid Sequence↗
PubMed2001

Single-channel recordings of recombinant inositol trisphosphate receptors in mammalian nuclear envelope.

Inositol 1,4,5-trisphosphate (InsP(3)) receptors (InsP(3)Rs) are intracellular Ca(2+) channels gated by the second messenger InsP(3). Here we describe a novel approach for recording single-channel currents through recombinant InsP(3)Rs in mammalian cells that applies patch-clamp electrophysiology to nuclei isolated from COS-7 cells transiently transfected with the neuronal (SII(+)) and peripheral (SII(-)) alternatively-spliced variants of the rat type 1 InsP(3)R. Single channels that were activated by InsP(3) and inhibited by heparin were observed in 45% of patches from nuclei prepared from transfected cells overexpressing recombinant InsP(3)Rs. In contrast, nuclei from cells transfected with the vector alone had InsP(3)-dependent channel activity in only 1.5% of patches. With K(+) (140 mM) as the permeant ion, recombinant SII(+) and SII(-) channels had slope conductances of 370 pS and 390 pS, respectively. The recombinant channels were 4-fold more selective for Ca(2+) over K(+), and their open probabilities were biphasically regulated by cytoplasmic [Ca(2+)]. This approach provides a powerful new methodology to study the permeation and gating properties of recombinant mammalian InsP(3)Rs in a native mammalian membrane environment at the single-channel level.

Alternative Splicing↗
PubMed1996

Regulation of nuclear envelope assembly/disassembly by MAP kinase.

Mouse eggs arrested in metaphase II display high levels of cdc2/cyclin B1 and MAP protein kinase activities. Following fertilization there is a time-dependent decrease in the activity of each of these protein kinases. The decline in cdc2/cyclin B1 protein kinase correlates with the resumption of meiosis and the emission of the second polar body and precedes the decline in MAP kinase activity, which correlates temporally with the formation of the male and female pronuclear envelopes. These results suggest that high levels of MAP kinase activity are incompatible with the presence of a pronuclear envelope. To test this possibility, we expressed in mouse eggs a constitutively active form of MAP kinase kinase (MEK) whose only known target is p42/p44 MAP kinase. We show that following fertilization cdc2/cyclin B1 kinase activity declines and a second polar body is emitted. The endogenous MAP kinase remains active, however, and no pronuclear envelopes form. Thus, high levels of MAP kinase activity by itself in mouse eggs appear incompatible with the presence of a pronuclear envelope.

Animals↗
PubMed2006

The human cytomegalovirus glycoprotein UL16 traffics through the plasma membrane and the nuclear envelope.

The human cytomegalovirus (HCMV) UL16 gene encodes a glycoprotein that interferes with the immune response to the virus-infected cell. In vitro, UL16 interacts with MICB and ULBPs that are ligands for the stimulatory receptor NKG2D, expressed on NK cells and CD8(+)T cells. UL16 expression has been shown to promote intracellular accumulation of MICB, ULBP1 and 2 and thus, interfere with the immune response to HCMV-infected cells. The mechanism that has been suggested for UL16-mediated MICB downmodulation is retention in the ER. Here, we studied the intracellular localization and maturation of UL16 and MICB in HCMV-infected cells and transfectant systems. UL16 trafficked through the ER, TGN and progressed to the plasma membrane, after which the protein was internalized. Strikingly, UL16 was also observed in the inner nuclear membrane. MICB was also localized in the TGN in HCMV-infected cells. These data suggest that MICB trafficking might be affected after its transit through the ER.

Cell Line↗