Spider and Bacterial Sphingomyelinases D Target Cellular Lysophosphatidic Acid Receptors by Hydrolyzing Lysophosphatidylcholine

Abstract

Bites byEnvenomation by Loxosceles spiders, endemic to temperate and (sub)tropical regions of the Americas, Africa, and Europe, can lead to local skin injury as well as to serious systemic toxicity, including thrombus formation, vascular leakage, hemolysis, and persistent inflammation (1-3). In severe cases, the hematologic complications can lead to renal failure and death, especially in children (2, 3). Treatment is difficult; antivenoms are not very effective, and the use of corticosteroids or anti-inflammatory medication is controversial (3). The toxin responsible for the local and systemic effects of Loxosceles venom is an unusual sphingomyelinase D (SMaseD) 1 that converts sphingomyelin (SM) in the outer leaflet of the plasma membrane to ceramide 1-phosphate (N-acylsphingosine 1-phosphate) (4 -7). Strikingly, while SMaseD is not found elsewhere in the animal kingdom, a similar enzyme is produced as an exotoxin by some pathogenic bacteria, notably Corynebacterium pseudotuberculosis, Corynebacterium ulcerans, and Arcanobacterium (formerly Corynebacterium) hemolyticum (8 -10). C. pseudotuberculosis causes lymphadenitis in animals but is also pathogenic for humans, while C. ulcerans and A. hemolyticum are pathogens of pharyngitis and other human infections (11); in no case is the molecular basis for virulence known (12). The SMaseD from C. pseudotuberculosis, also named SM-specific phospholipase D (PLD), is an essential virulence determinant that contributes to the persistence and spread of the bacteria within the host (13). The Loxosceles and C. pseudotuberculosis SMases D have the same molecular mass (31-32 kDa) and share about 30% sequence similarity (see "Results"). In model systems, the spider and bacterial enzymes provoke remarkably similar pathophysiological effects, including platelet aggregation, endothelial hyperpermeability, complement-dependent hemolysis, and neutrophil-dependent skin necrosis (4 -7, 9, 14 -16).Despite decades of study it remains unclear how SMaseD can elicit such a wide variety of biological effects, particularly, since ceramide 1-phosphate is not known as a signaling molecule. In contrast to ceramide, which may reorganize lipid microdomains and associated signaling complexes (17, 18), ceramide 1-phosphate is a bilayer-preferring phospholipid that is unlikely to significantly perturb membrane structure. Furthermore, mammalian cells treated with SMaseD from either Loxosceles deserta or C. pseudotuberculosis do not convert newly formed ceramide 1-phosphate to ceramide nor does SMaseD treatment affect membrane permeability or cell viability (19,20).Given the lack of understanding of SMaseD bioactivity, we set out to re-examine the substrate specificity and cellular effects of the enzyme. Our interest was stirred by a report of more than 30 years ago, showing that partially purified SMaseD from C. pseudotuberculosis (ovis) can catalyze the release of choline from lysophosphatidylcholine (LPC) but not from phosphatidylcholine (PC) (21). LPC is an abundant plasma component and removal ...

Corynebacterium pseudotuberculosis: microbiology, biochemical properties, pathogenesis and molecular studies of virulence

“…Several of the biological activities of C. pseudotuberculosis PLD, as well as its molecular structure, have also been found in sphingomyelinases in the venom of the medically important spider genus Loxosceles [7,10,30,102,108,112].…”

A description of genes of Corynebacterium pseudotuberculosis useful in diagnostics and vaccine applications

“…Several studies have been carried out involving the biological activities of C. pseudotuberculosis PLD, as well as its molecular structures, and results have shown similarities with sphingomyelinases present in the venom of the medically important spider genus Loxosceles (Bernheimer et al, 1985;Songer, 1997;Tambourgi et al, 2002;van Meeet al, 1985;Songer, 1997;Tambourgi et al, 2002;van Mee-1985;Songer, 1997;Tambourgi et al, 2002;van Meeet al, 2002;van Mee-2002;van Meeteren et al, 2004;Binford et al, 2005). Unlike diphtheria toxin, which occurs in about half of the isolates of C. diphtheria (Saragea et al, 1966;Toshach et al, 1977), PLD probably is characteristic of most or almost all strains of C. pseudotuberculosis and C. ulcerans and have not been found in any other Corynebacteria (Barksdale et al, 1981).…”

Of Spiders and Crabs: The Emergence of Lysophospholipids and Their Metabolic Pathways as Targets for Therapy in Cancer

“…In addition to cancer, LPA and S1P are central to the pathobiology of a wide variety of disease processes ranging from spider bites (65,66), diarrheal toxins (67), vascular plaque (32), transplantation rejection (18), and immune diathesis. The most intriguing of these is the recent demonstration that the production and action of LPA is required for the toxic effects of envenomation by the Loxosceles reclusa or brown recluse spider (Fig.…”