Expression of Panza, an α2-macroglobulin, in a restricted dorsal domain of the primitive gut in Xenopus laevis

Abstract

Abstractα2-macroglobulin is a major serum protein with diverse functions, including inhibition of protease activity and binding of growth factors, cytokines, and disease factors. We have cloned and characterized Panza, a new Xenopus laevis α2-macroglobulin. Panza has 56-60% amino acid similarity with previously identified Xenopus, mouse, rat and human α2-macroglobulins, indicating that Panza is a new member of the α2-macroglobulin family. Panza mRNA is first detected at the beginning of neurulation in the dorsal endoderm lining the primitive gut (archenteron roof). At the completion of neurulation and continuing through the late tadpole stage, Panza is restricted to a dorsal domain of the gut endoderm adjacent to the notochord and extending along the entire anteriorposterior axis. With outgrowth of the tailbud, Panza expression persists in the chordaneural hinge at the posterior end of the differentiating notochord and extends into the floor plate of the posterior neural tube. As gut coiling commences, Panza expression is initiated in the liver, and the dorsal domain of Panza expression becomes limited to the midgut and hindgut. With further gut coiling, strong Panza expression persists in the liver, but is lost from other regions of the gut. The expression of Panza in endodermal cells adjacent to the notochord points to a potential role for Panza in signal modulation and/or morphogenesis of the primitive gut. KeywordsXenopus laevis; α2-macroglobulin; endoderm; gut; digestive tract; liver Results and Discussionα2-macroglobulin (α 2 M) is an abundant plasma protein of vertebrates and arthropods that has a remarkable capacity to bind numerous and diverse ligands. α 2 M was first identified as a "panprotease inhibitor" capable of binding nearly all extracellular proteases, leading to clearance and degradation of α 2 M-protease complexes. Binding of protease to native α 2 M results in cleavage and activation of α 2 M, causing a conformational change that entraps protease and exposes binding sites for the α 2 M receptor. The α 2 M-protease complex binds to low density lipoprotein receptor-related protein (LRP), the major cell surface receptor for α 2 M, and the receptor bound complex is internalized by endocytosis, and targeted for lysosomal degradation (reviewed in Borth, 1992).* Author for correspondence Email:kesslerd@mail.med.upenn.edu, Tel: 215-898-1478, Fax: 215-573-7601 The conformational change that occurs with α 2 M activation also exposes binding sites for nonprotease ligands, including PDGF (Huang et al., 1984), FGF (Mathew et al., 2003), TGFβ1 (Huang et al., 1988;Stouffer et al., 1993;Feige et al., 1996;Arandjelovic et al., 2003), Activin A (Niemuller et al., 1995;Mather, 1996;Phillips, 2000), NGF (Ronne et al., 1979), TNF (James et al., 1992) and multiple Interleukins (Borth and Luger, 1989;Borth et al., 1990;Garber et al., 2000;Kurdowska et al., 2000). In complex with these ligands, α 2 M can serve either as a carrier that stabilizes ligand in circulation, a clearance factor for ligand degradation, or ...

FoxH1 mediates a Grg4 and Smad2 dependent transcriptional switch in Nodal signaling during Xenopus mesoderm development

“…For whole-mount in situ hybridization, embryos were fixed and hybridized with antisense digoxygenin-labeled RNA probes as previously described (Bae et al, 2011; Pineda-Salgado et al, 2005). Templates for in situ probes were pBSSK-Xnr5 and pBSSK-Xnr6 (Takahashi et al, 2000), pCS2-Chd (Sasai et al, 1994), and pGEM-Xbra (Wilson and Melton, 1994).…”

Cloning, distribution and primary immune characteristics of amphioxus alpha-2 macroglobulin

“…According to Armstrong (2006) [39], the diversity of the bait region sequences in a 2 Ms make them ideal scavengers for the diverse array of protease produced by the broad spectrum of pathogens that might attack during the lifetime of any given animal. Fourth, like most vertebrate (zebrafish, chicken, carp, frog and mouse) a 2 Ms [40,8,41,12,34], Bja 2 M also lacks the KPTVK motif in the receptor-binding region, which is present in some mammalian (including humans) a 2 Ms [42]. This suggests that the KPTVK motif in the receptor-binding region may be a novelty to mammalian a 2 Ms during chordate evolution.…”

“…The thiol ester bond is cleaved when a 2 M experiences proteolytic attack on the bait domain, thereby exposing the cysteinyl thiol and the carbonyl of glutamic acid, which can be cross-linked to the target proteinase. a 2 M presents widely in various animals including mammals [7], birds [8,9], reptiles [10], amphibians [11,12], fishes [13,14] and invertebrates such as shrimp [15,16], crab [17,18] and scallop [19]. As a broad-spectrum inhibitor to either harmful endogenous proteases or exogenous ones from invading pathogens, a 2 M is regarded to comprise an evolutionarily conserved arm of the innate immune system, playing an important role in defense reactions [20].…”

Alpha2 Macroglobulin-Like Is Essential for Liver Development in Zebrafish

“…Complete A2M deficiency has not been reported in humans, but mice with targeted mutations in the A2M or the related murinoglobulin gene are viable and fertile, with susceptibility to acute pancreatitis as the most apparent phenotype [10], [11]. In Xenopus laevis, the A2M-related genes endodermin ( EDD ) and Panza are expressed in liver and in other endodermal derivatives [12], [13], but developmental aspects of A2M family function in liver development have not been reported in this or any other species. Here we report the isolation of the zebrafish alpha-2 macroglobulin-like (A2ML ) gene, and show that it has a role in liver development in this organism.…”