Jung Jae Woo, Ahn Chihoon, Shim Sun Young, Gray Peter C, Kwiatkowski Witek, Choe Senyon
Joint Center for BiosciencesSongdo Global University Campus, 187 Songdo-dong, Yeonsu-gu, Incheon 406-840, KoreaStructural Biology LaboratoryClayton Foundation Laboratories for Peptide BiologyThe Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
Joint Center for BiosciencesSongdo Global University Campus, 187 Songdo-dong, Yeonsu-gu, Incheon 406-840, KoreaStructural Biology LaboratoryClayton Foundation Laboratories for Peptide BiologyThe Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA Joint Center for BiosciencesSongdo Global University Campus, 187 Songdo-dong, Yeonsu-gu, Incheon 406-840, KoreaStructural Biology LaboratoryClayton Foundation Laboratories for Peptide BiologyThe Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, California 92037, USA.
J Endocrinol. 2014 Oct;223(1):35-45. doi: 10.1530/JOE-14-0317. Epub 2014 Aug 6.
Activins and bone morphogenetic proteins (BMPs) share activin type 2 signaling receptors but utilize different type 1 receptors and Smads. We designed AB215, a potent BMP2-like Activin A/BMP2 chimera incorporating the high-affinity type 2 receptor-binding epitope of Activin A. In this study, we compare the signaling properties of AB215 and BMP2 in HEK293T cells and gonadotroph LβT2 cells in which Activin A and BMP2 synergistically induce FSHβ. In HEK293T cells, AB215 is more potent than BMP2 and competitively blocks Activin A signaling, while BMP2 has a partial blocking activity. Activin A signaling is insensitive to BMP pathway antagonism in HEK293T cells but is strongly inhibited by constitutively active (CA) BMP type 1 receptors. By contrast, the potencies of AB215 and BMP2 are indistinguishable in LβT2 cells and although AB215 blocks Activin A signaling, BMP2 has no inhibitory effect. Unlike HEK293T, Activin A signaling is strongly inhibited by BMP pathway antagonism in LβT2 cells but is largely unaffected by CA BMP type 1 receptors. BMP2 increases phospho-Smad3 levels in LβT2 cells, in both the absence and the presence of Activin A treatment, and augments Activin A-induced FSHβ. AB215 has the opposite effect and sharply decreases basal phospho-Smad3 levels and blocks Smad2 phosphorylation and FSHβ induction resulting from Activin A treatment. These findings together demonstrate that while AB215 activates the BMP pathway, it has opposing effects to those of BMP2 on FSHβ induction in LβT2 cells apparently due to its ability to block Activin A signaling.
激活素和骨形态发生蛋白（BMP）共享激活素2型信号受体，但利用不同的1型受体和Smad蛋白。我们设计了AB215，这是一种强效的BMP2样激活素A/BMP2嵌合体，它整合了激活素A的高亲和力2型受体结合表位。在本研究中，我们比较了AB215和BMP2在HEK293T细胞和促性腺激素细胞LβT2细胞中的信号传导特性，其中激活素A和BMP2协同诱导促卵泡激素β（FSHβ）。在HEK293T细胞中，AB215比BMP2更有效，并竞争性阻断激活素A信号传导，而BMP2具有部分阻断活性。在HEK293T细胞中，激活素A信号传导对BMP途径拮抗不敏感，但被组成型激活（CA）的BMP 1型受体强烈抑制。相比之下，AB215和BMP2在LβT2细胞中的效力无法区分，尽管AB215阻断激活素A信号传导，但BMP2没有抑制作用。与HEK293T不同，在LβT2细胞中，激活素A信号传导被BMP途径拮抗强烈抑制，但在很大程度上不受CA BMP 1型受体的影响。在有无激活素A处理的情况下，BMP2均可增加LβT2细胞中磷酸化Smad3的水平，并增强激活素A诱导的FSHβ。AB215则具有相反的作用，它会大幅降低基础磷酸化Smad3水平，并阻断激活素A处理导致的Smad2磷酸化和FSHβ诱导。这些发现共同表明，虽然AB215激活BMP途径，但它在LβT2细胞中对FSHβ诱导的作用与BMP2相反，这显然是由于它能够阻断激活素A信号传导。
