Platelet aggregation and sphingomyelinase D activity of a purified toxin from the venom of loxosceles reclusa

G, Kurpiewski; Forrester, Lawrence J.; Barrett, Janet R; Campbell, Benedict J.

doi:10.1016/0304-4165(81)90128-8

Cited by 147 publications

(74 citation statements)

References 27 publications

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“…First, as described above, bacterial SMases C and D inhibit CFTR current, an action leading to the production of thick mucus that clogs the airways and thereby fosters further bacterial growth. Second, SMase D causes severe tissue necrosis (17,39). Last, ceramide and ceramide-1-phosphate induce inflammation and/or trigger cell death (40)(41)(42)(43).…”

Section: Discussionmentioning

confidence: 99%

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Inhibition of CFTR Cl ⁻ channel function caused by enzymatic hydrolysis of sphingomyelin

Ramu

Lü

2007

Proc. Natl. Acad. Sci. U.S.A.

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Numerous mutations in the cystic fibrosis (CF) transmembrane conductance regulator (CFTR, a Cl − channel) disrupt salt and fluid transport and lead to the formation of thick mucus in patients' airways. Obstruction by mucus predisposes CF patients to chronic infections and inflammation, which become gradually harder to control and eventually fatal. Aggressive antibiotic therapy and supportive measures have dramatically lengthened CF patients' lives. Here, we report that sphingomyelinases (SMase) from human respiratory pathogens strongly inhibit CFTR function. The hydrolysis of sphingomyelin by SMase makes it more difficult to activate CFTR by phosphorylation of its regulatory domain. By inhibiting CFTR currents, SMase-producing respiratory tract bacteria may not only aggravate pulmonary infection in some CF patients but may also elicit a condition, analogous to CFTR deficiency, in non-CF patients suffering from bacterial lung infection.

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Section: Discussionmentioning

confidence: 99%

“…The enzyme catalyzes removal of the choline group of sphingomyelin (which is naturally present mainly in the outer leaf of the membrane bilayer). The hydrolysis products are choline and ceramide-1-phosphate (16,17) (Fig. 3D).…”

Section: Discovery and Identification Of Cftr-inhibiting Activity In mentioning

confidence: 99%

Inhibition of CFTR Cl ⁻ channel function caused by enzymatic hydrolysis of sphingomyelin

Ramu

Lü

2007

Proc. Natl. Acad. Sci. U.S.A.

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“…Both enzymes specifically hydrolyze sphingomyelin but in different ways (Fig. 1a): SMase D removes only choline and leaves the lipid ceramide-1-phosphate behind in the membrane whereas SMase C removes phosphocholine, leaving ceramide behind 12,13 . A comparison of the effects of these two enzymes on the channels will thus help reveal the functional significance of the phosphodiester group in voltage gating.…”

Section: Introductionmentioning

confidence: 99%

Removal of phospho-head groups of membrane lipids immobilizes voltage sensors of K+ channels

Ramu

Lü

2008

Nature

168

161

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A fundamental question regarding the gating mechanism of voltage-activated K + (Kv) channels is how five positively charged voltage-sensing residues in the fourth transmembrane (TM) segment 1, 2 are energetically stabilized, as they operate in a low-dielectric cell membrane. The simplest solution would be to pair them with negative charges 3 . However, too few negatively charged channel residues are positioned for such a role 4,5 . Recent studies suggest that some of the channel's positively charged residues are exposed to cell membrane phospholipids and interact with their head groups [5][6][7][8][9] . A key question nonetheless remains: Is the phospho-head of membrane lipids necessary for proper function of the voltage sensor itself? Here, we find that a given type of Kv channel may interact with several species of phospholipid, and that enzymatic removal of their negatively charged phospho-head creates an insuperable energy barrier for the positively charged voltage sensor to move through the initial gating step(s), thus immobilizing it, and also raises the energy barrier for the downstream step(s).Kv2.1 channels, expressed in Xenopus oocytes, interact with sphingomyelin 8 present mainly in the outer leaf of plasma membranes. To investigate the importance of phospho-head groups of membrane lipids in Kv channel gating we employed bacterial sphingomyelinases C and D (SMases C and D) 10,11 . Both enzymes specifically hydrolyze sphingomyelin but in different ways (Fig. 1a): SMase D removes only choline and leaves the lipid ceramide-1-phosphate behind in the membrane whereas SMase C removes phosphocholine, leaving ceramide behind 12,13 . A comparison of the effects of these two enzymes on the channels will thus help reveal the functional significance of the phosphodiester group in voltage gating.SMase D of Corynebacterium pseudotuberculosis 11 shifts the conductance-voltage (G-V) relation of Kv2.1 by about -30 mV 8 (Fig. 1d), allowing channels to be activated at a negative voltage where they otherwise remain largely deactivated (Fig. 1c). The effect is maximal within 2 minutes and persists for at least 24 hours ( Fig. 1c, d; cells cannot regenerate sphingomyelin from ceramide-1-phosphate). It does not require direct exposure of channels to SMase D as it also occurred in Kv2.1-expressing oocytes that had been treated with SMase D and then thoroughly washed prior to injection with Kv2.1 cRNA (Fig. 1e).* Please address correspondence to: Dr. Zhe Lu, University of Pennsylvania, Department of Physiology, D302A Richards Building, 3700 Hamilton Walk, Philadelphia, PA 19104, Tel: 215-573-7711, FAX: 215-573-1940, zhelu@mail.med.upenn Additional exposure of such oocytes to SMase D, as expected, caused no further shift. Thus, SMase D acts through its lipase activity, not by direct binding to the channel. Our previous study 8 supports an electrostatic mechanism whereby removal of the positively charged choline favors the activated state of the positively charged voltage sensors.Unlike SMase D, SMase C removes the nega...

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“…The exact mechanisms by which the S.S. Veiga et al venoms cause their deleterious effects are currently under investigation, with putative explanations involving an indirect event, as is the case for endothelial cell-dependent neutrophil activation caused by the venoms and seemingly related to the dermonecrotic lesion (4,(12)(13)(14). The presence of a sphingomyelinase D-like enzyme (32-35 kDa) probably associated with necrotic, hemolytic and thrombocytopenic activities triggered by the venoms has also been identified in different Loxosceles species (3,4,6,10,15,16). Other enzymes such as a hyaluronidase have been postulated to be a spreading factor during the lesions (4,17), and protease activities also appear to have some participation in the noxious effects of the venoms (11,(18)(19)(20)(21).…”

Section: Introductionmentioning

confidence: 99%

Extracellular matrix molecules as targets for brown spider venom toxins

Veiga

Zanetti

Braz

et al. 2001

Braz J Med Biol Res

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Loxoscelism, the term used to describe lesions and clinical manifestations induced by brown spiders venom (Loxosceles genus), has attracted much attention over the last years. Brown spider bites have been reported to cause a local and acute inflammatory reaction that may evolve to dermonecrosis (a hallmark of envenomation) and hemorrhage at the bite site, besides systemic manifestations such as thrombocytopenia, disseminated intravascular coagulation, hemolysis, and renal failure. The molecular mechanisms by which Loxosceles venoms induce injury are currently under investigation. In this review, we focused on the latest reports describing the biological and physiopathological aspects of loxoscelism, with reference mainly to the proteases recently described as metalloproteases and serine proteases, as well as on the proteolytic effects triggered by L. intermedia venom upon extracellular matrix constituents such as fibronectin, fibrinogen, entactin and heparan sulfate proteoglycan, besides the disruptive activity of the venom on Engelbreth-Holm-Swarm basement membranes. Degradation of these extracellular matrix molecules and the observed disruption of basement membranes could be related to deleterious activities of the venom such as loss of vessel and glomerular integrity and spreading of the venom toxins to underlying tissues. Correspondence

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Platelet aggregation and sphingomyelinase D activity of a purified toxin from the venom of loxosceles reclusa

Cited by 147 publications

References 27 publications

Inhibition of CFTR Cl ⁻ channel function caused by enzymatic hydrolysis of sphingomyelin

Inhibition of CFTR Cl ⁻ channel function caused by enzymatic hydrolysis of sphingomyelin

Removal of phospho-head groups of membrane lipids immobilizes voltage sensors of K+ channels

Extracellular matrix molecules as targets for brown spider venom toxins

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Platelet aggregation and sphingomyelinase D activity of a purified toxin from the venom of loxosceles reclusa

Cited by 147 publications

References 27 publications

Inhibition of CFTR Cl − channel function caused by enzymatic hydrolysis of sphingomyelin

Inhibition of CFTR Cl − channel function caused by enzymatic hydrolysis of sphingomyelin

Removal of phospho-head groups of membrane lipids immobilizes voltage sensors of K+ channels

Extracellular matrix molecules as targets for brown spider venom toxins

Contact Info

Product

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About

Inhibition of CFTR Cl ⁻ channel function caused by enzymatic hydrolysis of sphingomyelin

Inhibition of CFTR Cl ⁻ channel function caused by enzymatic hydrolysis of sphingomyelin