Identification and characterization of a novel follistatin-like protein as a binding protein for the TGF-beta family.
Follistatin is an activin-binding protein that prevents activin from binding to its receptors and neutralizes its activity. Follistatin also binds bone morphogenetic proteins (BMPs). In this study, we report the identification of a novel follistatin-like protein from mouse. The mouse cDNA encodes a 256-residue precursor and most likely a mouse homologue of human FLRG, which was found at the breakpoint of the chromosomal rearrangement in a B-cell line. Whereas follistatin has three follistatin domains, which are presumed to be growth factor binding motifs, FLRG possesses only two follistatin domains. Northern blotting revealed that mRNAs for FLRG were abundantly expressed in heart, lung, kidney, and testis in mouse. The recombinant mouse FLRG proteins were found to have binding activity for both activin and bone morphogenetic protein-2. Like follistatin, FLRG has higher affinity for activin than for BMP-2. The FLRG protein inhibited activin-induced and BMP-2-induced transcriptional responses in a dose-dependent manner. Glutathione S-transferase fusion proteins encoding various regions of FLRG were produced and studied. Ligand blotting using (125)I-activin revealed that the COOH-terminal region containing the second follistatin domain was able to bind activin. Our finding implies that cellular signaling by activin and BMPs is tightly regulated by multiple members of the follistatin family.
Tsuchida
K
K
Institute for Enzyme Research, University of Tokushima, 3-18-15 Kuramoto, Tokushima 770-8503, Japan. tsuchida@ier.tokushima-u.ac.jp
Arai
K Y
KY
Kuramoto
Y
Y
Yamakawa
N
N
Hasegawa
Y
Y
Sugino
H
H
D028341:Activins; D000818:Animals; D001665:Binding Sites; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins / Q000378:metabolism* / Q000494:pharmacology; D002352:Carrier Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000502:physiology; D003001:Cloning, Molecular; D004305:Dose-Response Relationship, Drug; D038702:Follistatin-Related Proteins; D006367:HeLa Cells; D006801:Humans; D007265:Inhibins / Q000378:metabolism*; D051379:Mice; D011506:Proteins / Q000737:chemistry / Q000302:isolation & purification* / Q000502:physiology; D012333:RNA, Messenger / Q000032:analysis; D011994:Recombinant Proteins; D014158:Transcription, Genetic / Q000187:drug effects; D016212:Transforming Growth Factor beta
C525718:BMP2 protein, human; C525719:Bmp2 protein, mouse; D055396:Bone Morphogenetic Protein 2; D019485:Bone Morphogenetic Proteins; D002352:Carrier Proteins; D038702:Follistatin-Related Proteins; C498620:Fstl3 protein, mouse; D011506:Proteins; D012333:RNA, Messenger; D011994:Recombinant Proteins; D016212:Transforming Growth Factor beta; C499469:recombinant human bone morphogenetic protein-2; D028341:Activins; D007265:Inhibins