CDB15:0001425 CRIPTO — ACVR1B
Experimentally validated in Human, Mixed species, Mouse; Orthology-inferred in Human, Mouse, Rat, Frog, Zebrafish, Macaque, Dog, Cow, Chimp, Horse, Marmoset, Sheep
Title
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Abstract
The orphan receptor ALK7 and the Activin receptor ALK4 mediate signaling by Nodal proteins during vertebrate development.
Genes & development, 2001; PubMed, Mus Musculus Cripto — Mus Musculus Acvr1b
ABSTRACT: Nodal proteins have crucial roles in mesendoderm formation and left-right patterning during vertebrate development. The molecular mechanisms of signal transduction by Nodal and related ligands, however, are not fully understood. In this paper, we present biochemical and functional evidence that the orphan type I serine/threonine kinase receptor ALK7 acts as a receptor for mouse Nodal and Xenopus Nodal-related 1 (Xnr1). Receptor reconstitution experiments indicate that ALK7 collaborates with ActRIIB to confer responsiveness to Xnr1 and Nodal. Both receptors can independently bind Xnr1. In addition, Cripto, an extracellular protein genetically implicated in Nodal signaling, can independently interact with both Xnr1 and ALK7, and its expression greatly enhances the ability of ALK7 and ActRIIB to respond to Nodal ligands. The Activin receptor ALK4 is also able to mediate Nodal signaling but only in the presence of Cripto, with which it can also interact directly. A constitutively activated form of ALK7 mimics the mesendoderm-inducing activity of Xnr1 in Xenopus embryos, whereas a dominant-negative ALK7 specifically blocks the activities of Nodal and Xnr1 but has little effect on other related ligands. In contrast, a dominant-negative ALK4 blocks all mesoderm-inducing ligands tested, including Nodal, Xnr1, Xnr2, Xnr4, and Activin. In agreement with a role in Nodal signaling, ALK7 mRNA is localized to the ectodermal and organizer regions of Xenopus gastrula embryos and is expressed during early stages of mouse embryonic development. Therefore, our results indicate that both ALK4 and ALK7 can mediate signal transduction by Nodal proteins, although ALK7 appears to be a receptor more specifically dedicated to Nodal signaling.
Cripto-1 activates nodal- and ALK4-dependent and -independent signaling pathways in mammary epithelial Cells.
Molecular and cellular biology, 2002; PubMed, Homo sapiens CRIPTO — Homo sapiens ACVR1B
ABSTRACT: Cripto-1 (CR-1), an epidermal growth factor-CFC (EGF-CFC) family member, has a demonstrated role in embryogenesis and mammary gland development and is overexpressed in several human tumors. Recently, EGF-CFC proteins were implicated as essential signaling cofactors for Nodal, a transforming growth factor beta family member whose expression has previously been defined as embryo specific. To identify a receptor for CR-1, a human brain cDNA phage display library was screened using CR-1 protein as bait. Phage inserts with identity to ALK4, a type I serine/threonine kinase receptor for Activin, were identified. CR-1 binds to cell surface ALK4 expressed on mammalian epithelial cells in fluorescence-activated cell sorter analysis, as well as by coimmunoprecipitation. Nodal is coexpressed with mouse Cr-1 in the mammary gland, and CR-1 can phosphorylate the transcription factor Smad-2 in EpH-4 mammary epithelial cells only in the presence of Nodal and ALK4. In contrast, CR-1 stimulation of mitogen-activated protein kinase and AKT in these cells is independent of Nodal and ALK4, suggesting that CR-1 may modulate different signaling pathways to mediate its different functional roles.
Structural insights into the interaction between the Cripto CFC domain and the ALK4 receptor.
Journal of peptide science : an official publication of the European Peptide Society, 2009; PubMed, Homo sapiens CRIPTO — Homo sapiens ACVR1B
ABSTRACT: The protein Cripto is the founding member of the extra-cellular EGF-CFC growth factors, which are composed of two adjacent cysteine-rich domains: the EGF-like and the CFC. Members of the EGF-CFC family play key roles in embryonic development and are also implicated in tumourigenesis. Cripto is highly over-expressed in many tumours, while it is poorly detectable in normal tissues. Although both Cripto domains are involved in its tumourigenic activity, the CFC domain appears to play a crucial role. Indeed, through this domain, Cripto interferes with the onco-suppressive activity of Activins, either by blocking the Activin receptor ALK4 or by antagonising proteins of the TGF-beta family. We have undertaken the chemical synthesis and the structural characterisation of human CFC Cripto domain. Using a combined NMR and computational approach, supported by binding studies by SPR, we have investigated the molecular basis of the interaction between h-CFC and ALK4. Binding studies indicate that the synthetic h-CFC interacts with the ALK4 receptor with a K(D) in micro M range, whereas it does not recognise the ActRIIB receptor. The NMR study shows that the h-CFC overall topology is determined by the presence of three disulfide bridges and that residues H120 and W124 are located between the first strand and the first loop with the side chains externally exposed. A model of the CFC-ALK4 complex has also been obtained by molecular docking and shows that all residues indicated by prior mutagenesis studies can contribute to the ALK4-CFC interaction at the protein-protein interface.