Abstract
Anterior gradient (AG) proteins have a thioredoxin fold and are targeted to the secretory pathway where they may act in the ER, as well as after secretion into the extracellular space. A newt member of the family (nAG) was previously identified as interacting with the GPI-anchored salamander-specific three-finger protein called Prod1. Expression of nAG has been implicated in the nerve dependence of limb regeneration in salamanders, and nAG acted as a growth factor for cultured newt limb blastemal (progenitor) cells, but the mechanism of action was not understood. Here we show that addition of a peptide antibody to Prod1 specifically inhibit the proliferation of blastema cells, suggesting that Prod1 acts as a cell surface receptor for secreted nAG, leading to S phase entry. Mutation of the single cysteine residue in the canonical active site of nAG to alanine or serine leads to protein degradation, but addition of residues at the C terminus stabilises the secreted protein. The mutation of the cysteine residue led to no detectable activity on S phase entry in cultured newt limb blastemal cells. In addition, our phylogenetic analyses have identified a new Caudata AG protein called AG4. A comparison of the AG proteins in a cell culture assay indicates that nAG secretion is significantly higher than AGR2 or AG4, suggesting that this property may vary in different members of the family.
Highlights
The first member of the anterior gradient protein family, referred to as XAG2, was identified as a marker of anterior non-neural development in Xenopus [1]
In order to investigate the activity of recombinant nAG, mammalian Cos7 cells were transfected with plasmids expressing either nAG or red fluorescent protein (RFP) as control
These results are consistent with the hypothesis that the stimulatory activity of nAG on the newt blastemal cells is mediated by interaction with its binding partner Prod1
Summary
The first member of the anterior gradient protein family, referred to as XAG2, was identified as a marker of anterior non-neural development in Xenopus [1]. The ectopic expression of this protein in embryos induced a supernumerary cement gland, a mucous-secreting element that expresses XAG2 [2]. It has recently been implicated as a critical secreted signal in Xenopus telencephalon formation [3]. Another amphibian AG protein was encountered in the context of salamander limb regeneration [4]. The newt protein nAG was identified as a binding partner of the salamander-specific protein Prod, a member of the three-finger protein (TFP)
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
