Differential subcellular distributions and trafficking functions of hnRNP A2/B1 spliceoforms.
Trafficking of mRNA molecules from the nucleus to distal processes in neural cells is mediated by heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 trans-acting factors. Although hnRNP A2/B1 is alternatively spliced to generate four isoforms, most functional studies have not distinguished between these isoforms. Here, we show, using isoform-specific antibodies and isoform-specific green fluorescent protein (GFP)-fusion expression constructs, that A2b is the predominant cytoplasmic isoform in neural cells, suggesting that it may play a key role in mRNA trafficking. The differential subcellular distribution patterns of the individual isoforms are determined by the presence or absence of alternative exons that also affect their dynamic behavior in different cellular compartments, as measured by fluorescence correlation spectroscopy. Expression of A2b is also differentially regulated with age, species and cellular development. Furthermore, coinjection of isoform-specific antibodies and labeled RNA into live oligodendrocytes shows that the assembly of RNA granules is impaired by blockade of A2b function. These findings suggest that neural cells modulate mRNA trafficking by regulating alternative splicing of hnRNP A2/B1 and controlling expression levels of A2b, which may be the predominant mediator of cytoplasmic-trafficking functions. These findings highlight the importance of considering isoform-specific functions for alternatively spliced proteins.
Han
Siew Ping
SP
School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland 4072, Australia.
Friend
Lexie R
LR
Carson
John H
JH
Korza
George
G
Barbarese
Elisa
E
Maggipinto
Michael
M
Hatfield
Jodie T
JT
Rothnagel
Joseph A
JA
Smith
Ross
R
D017398:Alternative Splicing; D000818:Animals; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D003593:Cytoplasm / Q000235:genetics / Q000378:metabolism; D003594:Cytoplasmic Granules / Q000235:genetics / Q000378:metabolism; D005091:Exons; D049452:Green Fluorescent Proteins / Q000378:metabolism; D006367:HeLa Cells; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins / Q000235:genetics / Q000378:metabolism*; D006624:Hippocampus / Q000166:cytology; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism / Q000473:pathology; D009474:Neurons / Q000378:metabolism; D009836:Oligodendroglia / Q000378:metabolism; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D021381:Protein Transport / Q000235:genetics / Q000502:physiology; D012313:RNA / Q000235:genetics / Q000378:metabolism; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013347:Subcellular Fractions / Q000378:metabolism; D015534:Trans-Activators / Q000235:genetics / Q000378:metabolism
D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D034441:Heterogeneous-Nuclear Ribonucleoproteins; D020033:Protein Isoforms; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D049452:Green Fluorescent Proteins; D012313:RNA
FEBS Lett. 2001 Jun 8;498(2-3):157-63
11412848
Gene. 2005 Jan 3;344:1-20
15656968
Nat Rev Neurosci. 2007 Nov;8(11):819-31
17895907
J Cell Sci. 2005 Jul 15;118(Pt 14):3173-83
16014382
J Biol Chem. 2000 Dec 8;275(49):38286-95
11024030
Cell. 1996 Sep 20;86(6):985-94
8808633
J Biol Chem. 2002 May 17;277(20):18010-20
11886857
Curr Opin Cell Biol. 1999 Jun;11(3):363-71
10395553
Proc Natl Acad Sci U S A. 1989 Dec;86(24):9788-92
2557628
Biochim Biophys Acta. 2008 Oct;1783(10):1972-80
18588922
Lung Cancer. 2005 Apr;48(1):77-83
15777973
Neuron. 2004 Aug 19;43(4):513-25
15312650
Dev Cell. 2004 May;6(5):625-35
15130488
J Cell Biol. 1999 Oct 18;147(2):247-56
10525532
J Cell Biol. 1993 Oct;123(2):431-41
7691830
J Neurosci. 2006 Jul 5;26(27):7131-4
16822966
Exp Cell Res. 2002 Oct 1;279(2):310-20
12243756
Traffic. 2006 Dec;7(12):1581-9
17054760
J Neurosci. 2003 Oct 1;23(26):8859-66
14523087
J Cell Sci. 1995 Feb;108 ( Pt 2):545-55
7769000
J Neurosci Res. 2004 Mar 1;75(5):614-23
14991837
Mol Biol Cell. 2008 May;19(5):2311-27
18305102
Mol Biol Cell. 2005 Apr;16(4):1938-47
15703215
Immunol Lett. 2001 Feb 1;76(1):49-54
11222913
Int J Biol Macromol. 1991 Jun;13(3):130-9
1716976
Neurosci Lett. 2005 Sep 30;386(2):111-5
15993539
Gene. 2002 Jul 24;295(1):33-42
12242009
Cell Mol Life Sci. 2009 Apr;66(7):1239-56
19099192
J Biol Chem. 1999 Nov 26;274(48):34389-95
10567417
Cancer Res. 1999 Apr 1;59(7):1404-7
10197602
Nat Rev Mol Cell Biol. 2002 Mar;3(3):195-205
11994740
Nucleic Acids Res. 2005 Jan 19;33(2):486-96
15659580
Lung Cancer. 2003 Aug;41(2):179-86
12871781
Exp Cell Res. 1999 Feb 1;246(2):399-411
9925756