Binding of Filamentous Actin to Anthrax Toxin Receptor 1 Decreases Its Association with Protective Antigen

Abstract

ANTXR1 is a Type I membrane protein that binds the protective antigen (PA) component of anthrax toxin. The cytosolic domain of ANTXR1 has a novel actin-binding region that influences the interaction of the ectodomain with PA. Here, we have investigated features of the cytosolic domain of ANTXR1 that reduce the association of the receptor with PA. We mutated a stretch of conserved acidic amino acids adjacent to the actin-binding region and found that the mutation increased the affinity for monomeric actin in vitro. ANTXR1 bearing this mutation exhibited increased association with the cytoskeleton and bound less PA compared to the wild-type receptor, confirming the inverse correlation between the two interactions. To determine whether binding of actin is sufficient to regulate the ectodomain, we replaced the actin-binding region of ANTXR1 with that from the yeast protein abp140 and with the WH2 domain of WAVE2. Although both of these domains bound monomeric actin in vitro, only the sequence from abp140 reduced binding of PA to a hybrid receptor. The actin binding regions of ANTXR1 and abp140, but not the WH2 domain, colocalized with actin stress fibres, which suggested that filamentous actin regulates ANTXR1. Consistent with this notion, disruption of actin filaments using latrunculin A increased the amount of PA bound to cells. This work provides evidence that cytoskeletal dynamics regulate ANTXR1 function.

Cell autonomous ANTXR1-mediated regulation of extracellular matrix components in primary fibroblasts

“…The generation of pcDNA3-ANTXR1-sv1-HA (sv1) plasmid has been described previously [25]. First, by quantifying western blots we confirmed 70% efficiency of sv1 transfection (normalized to β–actin, relative levels of expression of ANTXR1 and sv1 are 1.41 and 0.98, respectively) (Fig.…”

“…Previous studies provided evidence for direct interaction between ANTXR1 and the actin cytoskeleton and demonstrated a dramatic effect of ANTXR1 loss on cytoskeletal organization [2, 25]. Moreover, a study by Go and colleagues suggested that cytoskeletal dynamics regulates ANTXR1 function and its association with the extracellular matrix [26].…”

Bacillus cereus Certhrax ADP-ribosylates Vinculin to Disrupt Focal Adhesion Complexes and Cell Adhesion

“…However, because Certhrax also promotes toxicity in macrophages (17), Certhrax may also have a general cytopathogenic role in G9241 pathogenesis. Decreased association of actin with ANTXR-1 increases the affinity of PA for ANTXR-1 (65,66). Thus, Certhrax may enhance the potency of G9241 anthrax toxin through disruption of the actin cytoskeleton (E).…”

Therapeutic potential of capillary morphogenesis gene 2 extracellular vWA domain in tumour-related angiogenesis

“…CMG2 and TEM-8 share 60% sequence identity in their vWA domains, which contain a typical metal ion-dependent adhesion site (MIDAS) motif responsible for PA binding (39). The cytosolic tail of the TEM-8 can bind to filamentous actin which leads to a reduced association of the extracellular domain with PA (40).…”