The alternatively spliced LRRFIP1 Isoform-1 is a key regulator of the Wnt/β-catenin transcription pathway.
The GC-rich Binding Factor 2/Leucine Rich Repeat in the Flightless 1 Interaction Protein 1 gene (GCF2/LRRFIP1) is predicted to be alternatively spliced in five different isoforms. Although important peptide sequence differences are expected to result from this alternative splicing, to date, only the gene transcription regulator properties of LRRFIP1-Iso5 were unveiled. Based on molecular, cellular and biochemical data, we show here that the five isoforms define two molecular entities with different expression profiles in human tissues, subcellular localizations, oligomerization properties and transcription enhancer properties of the canonical Wnt pathway. We demonstrated that LRRFIP1-Iso3, -4 and -5, which share over 80% sequence identity, are primarily located in the cell cytoplasm and form homo and hetero-multimers between each other. In contrast, LRRFIP1-Iso1 and -2 are primarily located in the cell nucleus in part thanks to their shared C-terminal domain. Furthermore, we showed that LRRFIP1-Iso1 is preferentially expressed in the myocardium and skeletal muscle. Using the in vitro Topflash reporter assay we revealed that among LRRFIP1 isoforms, LRRFIP1-Iso1 is the strongest enhancer of the β-catenin Wnt canonical transcription pathway thanks to a specific N-terminal domain harboring two critical tryptophan residues (W76, 82). In addition, we showed that the Wnt enhancer properties of LRRFIP1-Iso1 depend on its homo-dimerisation which is governed by its specific coiled coil domain. Together our study identified LRRFIP1-Iso1 as a critical regulator of the Wnt canonical pathway with a potential role in myocyte differentiation and myogenesis.
l'institut du thorax, INSERM, CNRS, UNIV Nantes, Nantes, France.
Pauline
P
Labbé
Aix Marseille Univ, INSERM, GMGF, Marseille, France.
Emilie
E
Faure
CHU Nantes, Nantes, France.
Simon
S
Lecointe
l'institut du thorax, INSERM, CNRS, UNIV Nantes, Nantes, France.
Solena
S
Le Scouarnec
CHU Nantes, Nantes, France.
Florence
F
Kyndt
CHU Nantes, Nantes, France.
Marie
M
Marrec
CHU Nantes, Nantes, France.
Thierry
T
Le Tourneau
UMR CNRS 6286, UNIV Nantes, Nantes, France.
Bernard
B
Offmann
INSERM, Biology of Cardiovascular Diseases, U1034, F-33600 Pessac, France.
Cécile
C
Duplaà
Aix Marseille Univ, INSERM, GMGF, Marseille, France.
Stéphane
S
Zaffran
l'institut du thorax, INSERM, CNRS, UNIV Nantes, Nantes, France; CHU Nantes, Nantes, France.
Jean Jacques
JJ
Schott
l'institut du thorax, INSERM, CNRS, UNIV Nantes, Nantes, France. Electronic address: jean.merot@univ-nantes.fr.
Jean
J
Merot
D017398:Alternative Splicing; D000818:Animals; D002478:Cells, Cultured; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D051379:Mice; D018482:Muscle, Skeletal / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism; D000072417:Protein Domains; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D051153:Wnt Proteins / Q000235:genetics / Q000378:metabolism; D060449:Wnt Signaling Pathway; D051176:beta Catenin / Q000235:genetics / Q000378:metabolism
C583985:LRRFIP1 protein, rat; D020033:Protein Isoforms; D016601:RNA-Binding Proteins; D051153:Wnt Proteins; D051176:beta Catenin
Coiled coil domain; LEF-TCF; Leucine rich repeat; Muscle differentiation; Wnt catenin transcription