Stretching single talin rod molecules activates vinculin binding. in vitro, only the sequence from abp140 reduced binding of PA to a cross receptor. The actin binding regions of ANTXR1 and abp140, but not the WH2 domain name, 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. strong class=”kwd-title” Keywords: ANTXR1, anthrax toxin, cytoskeleton, protective antigen Anthrax toxin has wide-ranging effects around the host that contribute to the pathogenesis of Bacillus anthracis (1, 2). These pleiotropic responses to the toxin result from two enzymatic components that exert unique activities, each of which has Gastrodenol a substantial impact on cellular processes. Edema factor is an adenylate cyclase that produces the second messenger cAMP (3); lethal factor is usually a protease that disables three mitogen activated protein kinase (MAPK) signaling pathways (4, 5). The ability of anthrax toxin to broadly affect host physiology also results from its third component, protective antigen (PA), targeting two widely-expressed receptors, ANTXR1 and ANTXR2, which facilitates delivery of the harmful enzymes into the cytosol of most, if not all, cell types (6, 7). ANTXR1 and ANTXR2 are Type 1 membrane proteins that have comparable domain name businesses. The ectodomains consist of a von Willebrand Factor type A (VWA) domain name (also known as an I domain name), which binds PA (8, 9), and an immunoglobulin-like domain name positioned proximally to the membrane (10). Both receptors have a Gastrodenol single leucine-rich transmembrane domain name that contains an oligomerization motif; only the ANTXR1 transmembrane domain name has been studied, however, and shown to self-associate in vitro (11). The cytosolic tails of the receptors appear to lack structured domains, although they do have sequences that influence trafficking and a conserved region that binds actin (12, 13). Similarities between the receptors suggest related physiological functions. ANTXR1 was originally identified as a gene upregulated in tumor endothelial cells (originally named tumor endothelial marker 8, or TEM8) and ANTXR2 was shown to exhibit increased expression in cells undergoing capillary tube formation (capillary morphogenesis gene 2, or CMG2) (14, 15). This implied functions in angiogenic processes, athough neither ANTXR1-null nor ANTXR2-null mice appear to have gross vascular defects (16, 17). ANTXR1-null mice accumulate excessive amounts of extracellular matrix (ECM) components in several tissues, which is usually reminiscent of what is usually observed in patients with the ANTXR2 related diseases juvenile hyaline fibromatosis and infantile systemic hyalinosis (18). The receptors may, therefore, be involved in ECM homeostasis: ANTXR1 binds collagen I and VI, while ANTXR2 binds collagen IV and laminin (15, 19, 20). Finally, ANTXR1 has been implicated in cell adhesion and distributing by providing a link between collagen I and the actin cytoskeleton (21). The ANTXR1-actin conversation also influences the ability of ANTXR1 to bind PA C more PA binds cells that express an actin-binding deficient mutant of ANTXR1 compared to cells that express wild-type ANTXR1 (22). One explanation for this result is usually that wild-type ANTXR1 adopts both high affinity and low affinity ligand-binding conformations, whereas actin-binding deficient receptors adopt only the high affinity conformation. Consistent with this notion, a recent study used monoclonal antibodies to demonstrate the presence of two structurally unique populations of ANTXR1 around the cell surface that are regulated by the cytoskeleton: one monoclonal antibody acknowledged an epitope on one population and a second antibody acknowledged an epitope present on both populations (23). That this epitopes for the monoclonal antibodies map to the VWA domain name is perhaps not surprising because these domains are known Rabbit Polyclonal to GPR82 to undergo conformational changes that alter their ligand-binding properties. Ramey and colleagues launched Gastrodenol a mutation into the ANTXR1 VWA domain name that is known to lock certain VWA domains into a high affinity conformation and found that it overrode the effect of the.