scholarly journals Phosphoinositide Signaling Pathways in Nuclei Are Associated with Nuclear Speckles Containing Pre-mRNA Processing Factors

1998 ◽  
Vol 9 (12) ◽  
pp. 3547-3560 ◽  
Author(s):  
Igor V. Boronenkov ◽  
Joost C. Loijens ◽  
Masato Umeda ◽  
Richard A. Anderson
Keyword(s):  
Signaling Pathways ◽  
Mammalian Cells ◽  
Second Messengers ◽  
Mrna Processing ◽  
Type I ◽  
Nuclear Speckles ◽  
Phosphoinositide Signaling ◽  
Antibody Staining ◽  
Phosphatidylinositol 4 ◽  
Processing Factors

Phosphoinositide signal transduction pathways in nuclei use enzymes that are indistinguishable from their cytosolic analogues. We demonstrate that distinct phosphatidylinositol phosphate kinases (PIPKs), the type I and type II isoforms, are concentrated in nuclei of mammalian cells. The cytosolic and nuclear PIPKs display comparable activities toward the substrates phosphatidylinositol 4-phosphate and phosphatidylinositol 3-phosphate. Indirect immunofluorescence revealed that these kinases were associated with distinct subnuclear domains, identified as “nuclear speckles,” which also contained pre-mRNA processing factors. A pool of nuclear phosphatidylinositol bisphosphate (PIP2), the product of these kinases, was also detected at these same sites by monoclonal antibody staining. The localization of PIPKs and PIP2 to speckles is dynamic in that both PIPKs and PIP2 reorganize along with other speckle components upon inhibition of mRNA transcription. Because PIPKs have roles in the production of most phosphatidylinositol second messengers, these findings demonstrate that phosphatidylinositol signaling pathways are localized at nuclear speckles. Surprisingly, the PIPKs and PIP2 are not associated with invaginations of the nuclear envelope or any nuclear membrane structure. The putative absence of membranes at these sites suggests novel mechanisms for the generation of phosphoinositides within these structures.

scholarly journals Multiple Aspects of PIP2 Involvement in C. elegans Gametogenesis

2018 ◽  
Vol 19 (9) ◽  
pp. 2679 ◽  
Author(s):  
Livia Ulicna ◽  
Jana Rohozkova ◽  
Pavel Hozak
Keyword(s):  
Mammalian Cells ◽  
Chromosome Structure ◽  
Type I ◽  
Nuclear Speckles ◽  
C Elegans ◽  
Meiotic Progression ◽  
Prophase I ◽  
Binding Partners ◽  
Ubiquitin Proteasome ◽  
Proteasome Pathway

One of the most studied phosphoinositides is phosphatidylinositol 4,5-bisphosphate (PIP2), which localizes to the plasma membrane, nuclear speckles, small foci in the nucleoplasm, and to the nucleolus in mammalian cells. Here, we show that PIP2 also localizes to the nucleus in prophase I, during the gametogenesis of C. elegans hermaphrodite. The depletion of PIP2 by type I PIP kinase (PPK-1) kinase RNA interference results in an altered chromosome structure and leads to various defects during meiotic progression. We observed a decreased brood size and aneuploidy in progeny, defects in synapsis, and crossover formation. The altered chromosome structure is reflected in the increased transcription activity of a tightly regulated process in prophase I. To elucidate the involvement of PIP2 in the processes during the C. elegans development, we identified the PIP2-binding partners, leucine-rich repeat (LRR-1) protein and proteasome subunit beta 4 (PBS-4), pointing to its involvement in the ubiquitin–proteasome pathway.

scholarly journals Phosphatidylinositol 4-phosphate is a major source of GPCR-stimulated phosphoinositide production

2018 ◽  
Vol 11 (547) ◽  
pp. eaan1210 ◽  
Author(s):  
Rafael Gil de Rubio ◽  
Richard F. Ransom ◽  
Sundeep Malik ◽  
David I. Yule ◽  
Arun Anantharam ◽  
...  
Keyword(s):  
Mammalian Cells ◽  
Inositol Phosphate ◽  
Second Messengers ◽  
Receptor Activation ◽  
Cardiac Cells ◽  
Phosphoinositide Hydrolysis ◽  
General Mechanism ◽  
Gpcr Activation ◽  
Almost All ◽  
Phosphatidylinositol 4

Phospholipase C (PLC) enzymes hydrolyze the plasma membrane (PM) lipid phosphatidylinositol 4,5-bisphosphate (PI4,5P2) to generate the second messengers inositol trisphosphate (IP3) and diacylglycerol (DAG) in response to receptor activation in almost all mammalian cells. We previously found that stimulation of G protein–coupled receptors (GPCRs) in cardiac cells leads to the PLC-dependent hydrolysis of phosphatidylinositol 4-phosphate (PI4P) at the Golgi, a process required for the activation of nuclear protein kinase D (PKD) during cardiac hypertrophy. We hypothesized that GPCR-stimulated PLC activation leading to direct PI4P hydrolysis may be a general mechanism for DAG production. We measured GPCR activation–dependent changes in PM and Golgi PI4P pools in various cells using GFP-based detection of PI4P. Stimulation with various agonists caused a time-dependent reduction in PI4P-associated, but not PI4,5P2-associated, fluorescence at the Golgi and PM. Targeted depletion of PI4,5P2 from the PM before GPCR stimulation had no effect on the depletion of PM or Golgi PI4P, total inositol phosphate (IP) production, or PKD activation. In contrast, acute depletion of PI4P specifically at the PM completely blocked the GPCR-dependent production of IPs and activation of PKD but did not change the abundance of PI4,5P2. Acute depletion of Golgi PI4P had no effect on these processes. These data suggest that most of the PM PI4,5P2 pool is not involved in GPCR-stimulated phosphoinositide hydrolysis and that PI4P at the PM is responsible for the bulk of receptor-stimulated phosphoinositide hydrolysis and DAG production.

scholarly journals Son Is Essential for Nuclear Speckle Organization and Cell Cycle Progression

2010 ◽  
Vol 21 (4) ◽  
pp. 650-663 ◽  
Author(s):  
Alok Sharma ◽  
Hideaki Takata ◽  
Kei-ichi Shibahara ◽  
Athanasios Bubulya ◽  
Paula A. Bubulya
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Mrna Processing ◽  
Mrna Splicing ◽  
Scaffolding Protein ◽  
Splicing Factors ◽  
Nuclear Speckles ◽  
Intact Cells ◽  
Cycle Progression ◽  
Processing Factors

Subnuclear organization and spatiotemporal regulation of pre-mRNA processing factors is essential for the production of mature protein-coding mRNAs. We have discovered that a large protein called Son has a novel role in maintaining proper nuclear organization of pre-mRNA processing factors in nuclear speckles. The primary sequence of Son contains a concentrated region of multiple unique tandem repeat motifs that may support a role for Son as a scaffolding protein for RNA processing factors in nuclear speckles. We used RNA interference (RNAi) approaches and high-resolution microscopy techniques to study the functions of Son in the context of intact cells. Although Son precisely colocalizes with pre-mRNA splicing factors in nuclear speckles, its depletion by RNAi leads to cell cycle arrest in metaphase and causes dramatic disorganization of small nuclear ribonuclear protein and serine-arginine rich protein splicing factors during interphase. Here, we propose that Son is essential for appropriate subnuclear organization of pre-mRNA splicing factors and for promoting normal cell cycle progression.

scholarly journals SRSF1 regulates the assembly of pre-mRNA processing factors in nuclear speckles

2012 ◽  
Vol 23 (18) ◽  
pp. 3694-3706 ◽  
Author(s):  
Vidisha Tripathi ◽  
David Y. Song ◽  
Xinying Zong ◽  
Sergey P. Shevtsov ◽  
Stephen Hearn ◽  
...  
Keyword(s):  
Gene Expression ◽  
Rna Polymerase Ii ◽  
Cell Nucleus ◽  
Interphase Nucleus ◽  
Sr Proteins ◽  
Mrna Processing ◽  
Splicing Factors ◽  
Nuclear Speckles ◽  
Nuclear Speckle ◽  
Processing Factors

The mammalian cell nucleus is compartmentalized into nonmembranous subnuclear domains that regulate key nuclear functions. Nuclear speckles are subnuclear domains that contain pre-mRNA processing factors and noncoding RNAs. Many of the nuclear speckle constituents work in concert to coordinate multiple steps of gene expression, including transcription, pre-mRNA processing and mRNA transport. The mechanism that regulates the formation and maintenance of nuclear speckles in the interphase nucleus is poorly understood. In the present study, we provide evidence for the involvement of nuclear speckle resident proteins and RNA components in the organization of nuclear speckles. SR-family splicing factors and their binding partner, long noncoding metastasis-associated lung adenocarcinoma transcript 1 RNA, can nucleate the assembly of nuclear speckles in the interphase nucleus. Depletion of SRSF1 in human cells compromises the association of splicing factors to nuclear speckles and influences the levels and activity of other SR proteins. Furthermore, on a stably integrated reporter gene locus, we demonstrate the role of SRSF1 in RNA polymerase II–mediated transcription. Our results suggest that SR proteins mediate the assembly of nuclear speckles and regulate gene expression by influencing both transcriptional and posttranscriptional activities within the cell nucleus.

scholarly journals Modulation of phosphatidylinositol 4-phosphate levels by CaBP7 controls cytokinesis in mammalian cells

2015 ◽  
Vol 26 (8) ◽  
pp. 1428-1439 ◽  
Author(s):  
Dayani Rajamanoharan ◽  
Hannah V. McCue ◽  
Robert D. Burgoyne ◽  
Lee P. Haynes
Keyword(s):  
Cell Division ◽  
Hela Cells ◽  
Calcium Binding ◽  
Mammalian Cells ◽  
Calcium Binding Protein ◽  
Model Systems ◽  
Intercellular Bridge ◽  
Phosphoinositide Signaling ◽  
Novel Association ◽  
Phosphatidylinositol 4

Calcium and phosphoinositide signaling regulate cell division in model systems, but their significance in mammalian cells is unclear. Calcium-binding protein-7 (CaBP7) is a phosphatidylinositol 4-kinaseIIIβ (PI4KIIIβ) inhibitor required during cytokinesis in mammalian cells, hinting at a link between these pathways. Here we characterize a novel association of CaBP7 with lysosomes that cluster at the intercellular bridge during cytokinesis in HeLa cells. We show that CaBP7 regulates lysosome clustering and that PI4KIIIβ is essential for normal cytokinesis. CaBP7 depletion induces lysosome mislocalization, extension of intercellular bridge lifetime, and cytokinesis failure. These data connect phosphoinositide and calcium pathways to lysosome localization and normal cytokinesis in mammalian cells.

Hyperactivation of RAP1 and JAK/STAT Signaling Pathways Contributes to Fibrosis during the Formation of Nasal Capsular Contraction

2021 ◽  
pp. 1-12
Author(s):  
Meng Wu ◽  
Ming Li ◽  
Hong-Ju Xie ◽  
Hong-Wei Liu
Keyword(s):  
Signaling Pathways ◽  
Type I Collagen ◽  
Ex Vivo ◽  
Capsular Contracture ◽  
Silicone Implant ◽  
Type I ◽  
Loss Of Function ◽  
Sequencing Data ◽  
Functional Changes ◽  
Stat Signaling

Silicone implant-based augmentation rhinoplasty or mammoplasty induces capsular contracture, which has been acknowledged as a process that develops an abnormal fibrotic capsule associated with the immune response to allogeneic materials. However, the signaling pathways leading to the nasal fibrosis remain poorly investigated. We aimed to explore the molecular mechanism underlying the pathogenesis of nasal capsular contracture, with a specific research interest in the signaling pathways involved in fibrotic development at the advanced stage of contracture. By examining our recently obtained RNA sequencing data and global gene expression profiling between grade II and grade IV nasal capsular tissues, we found that both the RAP1 and JAK/STAT signaling pathways were hyperactive in the contracted capsules. This was verified on quantitative real-time PCR which demonstrated upregulation of most of the representative component signatures in these pathways. Loss-of-function assays through siRNA-mediated Rap1 silencing and/or small molecule-directed inhibition of JAK/STAT pathway in ex vivo primary nasal fibroblasts caused a series of dramatic behavioral and functional changes, including decreased cell viability, increased apoptosis, reduced secretion of proinflammatory cytokines, and synthesis of type I collagen, compared to control cells, and indicating the essential role of the RAP1 and JAK/STAT signaling pathways in nasal capsular fibrosis. Our results sheds light on targeting downstream signaling pathways for the prevention and therapy of silicone implant-induced nasal capsular contracture.

scholarly journals The methyltransferase SETD2 couples transcription and splicing by engaging mRNA processing factors through its SHI domain

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Saikat Bhattacharya ◽  
Michaella J. Levy ◽  
Ning Zhang ◽  
Hua Li ◽  
Laurence Florens ◽  
...  
Keyword(s):  
Rna Splicing ◽  
Rna Binding ◽  
Mrna Processing ◽  
Key Factors ◽  
Pol Ii ◽  
Mrna Transcripts ◽  
Hnrnp Protein ◽  
Processing Factors

AbstractHeterogeneous ribonucleoproteins (hnRNPs) are RNA binding molecules that are involved in key processes such as RNA splicing and transcription. One such hnRNP protein, hnRNP L, regulates alternative splicing (AS) by binding to pre-mRNA transcripts. However, it is unclear what factors contribute to hnRNP L-regulated AS events. Using proteomic approaches, we identified several key factors that co-purify with hnRNP L. We demonstrate that one such factor, the histone methyltransferase SETD2, specifically interacts with hnRNP L in vitro and in vivo. This interaction occurs through a previously uncharacterized domain in SETD2, the SETD2-hnRNP Interaction (SHI) domain, the deletion of which, leads to a reduced H3K36me3 deposition. Functionally, SETD2 regulates a subset of hnRNP L-targeted AS events. Our findings demonstrate that SETD2, by interacting with Pol II as well as hnRNP L, can mediate the crosstalk between the transcription and the splicing machinery.

scholarly journals The intersection of COVID-19 and cancer: signaling pathways and treatment implications

2021 ◽  
Vol 20 (1) ◽  
Author(s):  
Zhi Zong ◽  
Yujun Wei ◽  
Jiang Ren ◽  
Long Zhang ◽  
Fangfang Zhou
Keyword(s):  
Signaling Pathways ◽  
Health Concern ◽  
Type I ◽  
The Novel ◽  
Checkpoint Signaling ◽  
Patients With Cancer ◽  
Advantages And Disadvantages ◽  
Anticancer Treatment ◽  
Severe Infections ◽  
Novel Coronavirus

AbstractThe outbreak of the novel coronavirus disease 2019 (COVID-19) caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has emerged as a serious public health concern. Patients with cancer have been disproportionately affected by this pandemic. Increasing evidence has documented that patients with malignancies are highly susceptible to severe infections and mortality from COVID-19. Recent studies have also elucidated the molecular relationship between the two diseases, which may not only help optimize cancer care during the pandemic but also expand the treatment for COVID-19. In this review, we highlight the clinical and molecular similarities between cancer and COVID-19 and summarize the four major signaling pathways at the intersection of COVID-19 and cancer, namely, cytokine, type I interferon (IFN-I), androgen receptor (AR), and immune checkpoint signaling. In addition, we discuss the advantages and disadvantages of repurposing anticancer treatment for the treatment of COVID-19.

Compartmentalization of RNA Processing Factors within Nuclear Speckles

2000 ◽  
Vol 129 (2-3) ◽  
pp. 241-251 ◽  
Author(s):  
Paul J. Mintz ◽  
David L. Spector
Keyword(s):  
Rna Processing ◽  
Nuclear Speckles ◽  
Processing Factors
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