scholarly journals A novel neuronal-specific splice variant of Type I phosphatidylinositol 4-phosphate 5-kinase isoform gamma

2004 ◽  
Vol 379 (2) ◽  
pp. 489-496 ◽  
Author(s):  
Maria-Luisa GIUDICI ◽  
Piers C. EMSON ◽  
Robin F. IRVINE
Keyword(s):  
Splice Variant ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Splice Variants ◽  
Type I ◽  
Cellular Processes ◽  
C Terminus ◽  
Neuronal Processes ◽  
Phosphatidylinositol 4

Type I PIPkins (phosphatidylinositol 4-phosphate 5-kinases) are the enzymes that catalyse the major cellular route of synthesis of PtdIns(4,5)P2, and three isoforms (α, β and γ) with several splice variants have been found to date. In the present paper, we describe the discovery of a novel splice variant of the γ isoform, which we call PIPkin Iγc, and which is characterized by the inclusion of a 26-amino-acid insert near the C-terminus. Its transcript appears to be selectively expressed in brain, where it locates in the neurons of restricted regions, such as cerebellum, hippocampus, cortex and olfactory bulb, as indicated by in situ hybridization studies. Overexpression of two different catalytically inactive constructs of PIPkin Iγc in rat cerebellar granule cells causes a progressive loss of their neuronal processes, whereas equivalent kinase-dead versions of PIPkin Iγa did not induce any such effect, suggesting the possible existence of a specific PtdIns(4,5)P2 pool synthesized by PIPkin Iγc, which is involved in the maintenance of some neuronal cellular processes.

scholarly journals Type I phosphatidylinositol 4-phosphate 5-kinase controls neutrophil polarity and directional movement

2007 ◽  
Vol 179 (7) ◽  
pp. 1539-1553 ◽  
Author(s):  
Rosa Ana Lacalle ◽  
Rosa M. Peregil ◽  
Juan Pablo Albar ◽  
Ernesto Merino ◽  
Carlos Martínez-A ◽  
...  
Keyword(s):  
Actin Polymerization ◽  
Cell Movement ◽  
Leading Edge ◽  
Cell Polarization ◽  
Type I ◽  
Lipid Kinase ◽  
Erm Proteins ◽  
Chemical Gradients ◽  
C Terminus ◽  
Phosphatidylinositol 4

Directional cell movement in response to external chemical gradients requires establishment of front–rear asymmetry, which distinguishes an up-gradient protrusive leading edge, where Rac-induced F-actin polymerization takes place, and a down-gradient retractile tail (uropod in leukocytes), where RhoA-mediated actomyosin contraction occurs. The signals that govern this spatial and functional asymmetry are not entirely understood. We show that the human type I phosphatidylinositol 4-phosphate 5-kinase isoform β (PIPKIβ) has a role in organizing signaling at the cell rear. We found that PIPKIβ polarized at the uropod of neutrophil-differentiated HL60 cells. PIPKIβ localization was independent of its lipid kinase activity, but required the 83 C-terminal amino acids, which are not homologous to other PIPKI isoforms. The PIPKIβ C terminus interacted with EBP50 (4.1-ezrin-radixin-moesin (ERM)-binding phosphoprotein 50), which enabled further interactions with ERM proteins and the Rho-GDP dissociation inhibitor (RhoGDI). Knockdown of PIPKIβ with siRNA inhibited cell polarization and impaired cell directionality during dHL60 chemotaxis, suggesting a role for PIPKIβ in these processes.

scholarly journals Evolutionary Emergence of a Novel Splice Variant with an Opposite Effect on the Cell Cycle

2015 ◽  
Vol 35 (12) ◽  
pp. 2203-2214 ◽  
Author(s):  
Muhammad Sohail ◽  
Jiuyong Xie
Keyword(s):  
Cell Cycle ◽  
Splice Variant ◽  
Splice Variants ◽  
Exon Skipping ◽  
Regulatory Elements ◽  
Cellular Processes ◽  
Human Genes ◽  
Splicing Regulatory Elements ◽  
Evolutionary Emergence ◽  
Nuclear Ribonucleoprotein

Alternative splicing contributes greatly to the diversification of mammalian proteomes, but the molecular basis for the evolutionary emergence of splice variants remains poorly understood. We have recently found a novel class of splicing regulatory elements between the polypyrimidine tract (Py) and 3′ AG (REPA) at intron ends in many human genes, including the multifunctionalPRMT5(for protein arginine methyltransferase 5) gene. The PRMT5 element is comprised of two G tracts that arise in most mammals and accompany significant exon skipping in human transcripts. The G tracts inhibit splicing by recruiting heterogeneous nuclear ribonucleoprotein (hnRNP) H and F (H/F) to reduce U2AF65 binding to the Py, causing exon skipping. The resulting novel shorter variant PRMT5S exhibits a histone H4R3 methylation effect similar to that seen with the original longer PRMT5L isoform but exhibits a distinct localization and preferential control of critical genes for cell cycle arrest at interphase in comparison to PRMT5L. This report thus provides a molecular mechanism for the evolutionary emergence of a novel splice variant with an opposite function in a fundamental cell process. The presence of REPA elements in a large group of genes implies their wider impact on different cellular processes for increased protein diversity in humans.

scholarly journals Two novel phosphatidylinositol-4-phosphate 5-kinase type Iγ splice variants expressed in human cells display distinctive cellular targeting

2009 ◽  
Vol 422 (3) ◽  
pp. 473-482 ◽  
Author(s):  
Nicholas J. Schill ◽  
Richard A. Anderson
Keyword(s):  
Amino Acids ◽  
Splice Variant ◽  
Protein Targeting ◽  
Splice Variants ◽  
Human Cells ◽  
Subcellular Targeting ◽  
Splice Isoforms ◽  
Messenger Molecules ◽  
Phosphatidylinositol 4

The generation of various phosphoinositide messenger molecules at distinct locations within the cell is mediated via the specific targeting of different isoforms and splice variants of phosphoinositide kinases. The lipid messenger PtdIns(4,5)P2 is generated by several of these enzymes when targeted to distinct cellular compartments. Several splice variants of the type Iγ isoform of PIPK (PtdIns4P 5-kinase), which generate PtdIns(4,5)P2, have been identified, and each splice variant is thought to serve a unique functional role within cells. Here, we have identified two novel C-terminal splice variants of PIPKIγ in human cells consisting of 700 and 707 amino acids. These two splice variants are expressed in multiple tissue types and display PIPK activity in vitro. Interestingly, both of these novel splice variants display distinct subcellular targeting. With the addition of these two new splice isoforms, there are minimally five PIPKIγ splice variants that have been identified in mammals. Therefore, we propose the use of the HUGO (Human Genome Organization) nomenclature in the naming of the splice isoforms. PIPKIγ_i4 (700 amino acids) is present in the nucleus, a targeting pattern that has not been previously observed in any PIPKIγ splice variant. PIPKIγ_i5 (707 amino acids) is targeted to intracellular vesicle-like structures, where it co-localizes with markers of several types of endosomal compartments. As occurs with other PIPKIγ splice variants, the distinctive C-terminal sequences of PIPKIγ_i4 and PIPKIγ_i5 may facilitate association with unique protein targeting factors, thereby localizing the kinases to their appropriate cellular subdomains for the site-specific generation of PtdIns(4,5)P2.

Expression of fibronectin mRNA splice variants by rabbit lung in vivo and by alveolar type II cells in vitro

1996 ◽  
Vol 271 (6) ◽  
pp. L972-L980
Author(s):  
W. M. Maniscalco ◽  
R. H. Watkins ◽  
M. H. Campbell
Keyword(s):  
Gene Transcription ◽  
Splice Variant ◽  
Splice Variants ◽  
Alveolar Type ◽  
Type I ◽  
Type Ii Cells ◽  
Type Ii ◽  
Alveolar Type Ii Cells ◽  
Injured Lung

Fibronectin (FN) is a multidomain glycoprotein with putative functions in tissue development and repair. In repair of alveolar injury, FN may promote the transition of type II epithelial cells to type I epithelial cells. Alternative splicing of FN mRNA, including the EIIIA and EIIIB exons, results in protein isoforms that have cell, tissue, and developmental specificity. The present work found that FN mRNA with the EIIIA exon was in fetal, adult, and oxidant-injured lung. The EIIIB splice variant, however, was restricted to fetal lung and adult lung recovering from oxidant injury. Because alveolar type II cells in vitro express FN, we examined the splice variants in two conditions that induce FN [transforming growth factor-beta 1 (TGF-beta 1) treatment and time in culture]. TGF-beta 1 increased both EIIIA and EIIIB mRNA abundance by 10-fold. Increased EIIIA isoform immunostaining was also noted. Type II cells that spontaneously express FN at 72 h in vitro had increased EIIIA and EIIIB mRNA and increased immunostaining for EIIIA. Nuclear runoff showed induction of FN gene transcription at 72 h in vitro. Together, these data show differential FN splice variant expression in lung, with EIIIB mRNA restricted to fetal and recovering oxidant-injured lung. Furthermore, the transition of type II cells to a type I-like cell is accompanied by increased FN gene transcription and induction of both EIIIA and EIIIB mRNA.

scholarly journals Fbxo2VHC mouse and embryonic stem cell reporter lines delineate in vitro-generated inner ear sensory epithelia cells and enable otic lineage selection and Cre-recombination

2018 ◽  
Author(s):  
Byron H. Hartman ◽  
Robert Böscke ◽  
Daniel C. Ellwanger ◽  
Sawa Keymeulen ◽  
Mirko Scheibinger ◽  
...  
Keyword(s):  
Inner Ear ◽  
Granule Cells ◽  
Cerebellar Granule Cells ◽  
Es Cells ◽  
Embryonic Stem ◽  
Cellular Heterogeneity ◽  
Type I ◽  
Vestibular Hair Cells ◽  
Sensory Epithelia

ABSTRACTWhile the mouse has been a productive model for inner ear studies, the lack of highly specific genes and tools have presented challenges, specifically for in vitro studies of otic development, where innate cellular heterogeneity and disorganization increase the reliance on lineage-specific markers. To address this challenge in mice and embryonic stem (ES) cells, we targeted the lineage-specific otic gene Fbxo2 with a multicistronic reporter cassette (Venus/Hygro/CreER = VHC). In otic organoids derived from ES cells, Fbxo2VHC specifically delineates otic progenitors and inner ear sensory epithelia. In mice, Venus expression and CreER activity reveal a cochlear developmental gradient, label the prosensory lineage, show enrichment in a subset of type I vestibular hair cells, and expose strong expression in adult cerebellar granule cells. We provide a toolbox of multiple spectrally distinct reporter combinations to the community for studies that require use of fluorescent reporters, hygromycin selection, and conditional Cre-mediated recombination.SUMMARY STATEMENTA multifunctional Fbxo2-targeted reporter in mice and stem cells was developed and characterized as a resource for inner ear studies, along with a toolbox of plasmids to facilitate the use of this technique for other users.

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